WTNT44 KNHC 212051
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 PM AST TUE AUG 21 2012
 
AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE
DEPRESSION REPORTED 44-KT FLIGHT-LEVEL WINDS AT 1000 FT TO THE
NORTHEAST OF THE CENTER...AS WELL AS BIAS-CORRECTED SFMR SURFACE
WINDS ESTIMATES OF 35 KT.  THE MINIMUM CENTRAL PRESSURE WAS NEAR
1005 MB.  BASED ON THESE DATA...THE DEPRESSION IS UPGRADED TO
TROPICAL STORM ISAAC.  DESPITE THE UPGRADE...THE CYCLONE REMAINS
SOMEWHAT DISORGANIZED...WITH THE LOW-LEVEL CENTER PARTLY EXPOSED TO
THE NORTH OF THE MAIN CONVECTIVE MASS.
 
THE LOW-LEVEL CENTER HAS NUDGED NORTHWARD DURING THE AFTERNOON...BUT
THE LONGER TERM MOTION IS 275/15.  ISAAC REMAINS SOUTH OF A
DEEP-LAYER SUBTROPICAL RIDGE THAT IS FORECAST TO REMAIN INTACT
FOR THE NEXT 72 HR...WHICH SHOULD KEEP THE CYCLONE MOVING GENERALLY
WESTWARD AS SHOWN BY THE TIGHTLY CLUSTERED TRACK MODEL GUIDANCE.
AFTER THAT...THE GLOBAL MODELS CONTINUE TO FORECAST A SHORTWAVE
TROUGH TO DIG SOUTHWARD OVER THE SOUTHEASTERN U.S. AND THE GULF OF
MEXICO...WHICH IS EXPECTED TO WEAKEN THE RIDGE ACROSS FLORIDA AND
THE BAHAMAS. THIS SHOULD ALLOW THE CYCLONE TO TURN WEST-
NORTHWESTWARD AND SLOW DOWN OVER THE NORTH-CENTRAL CARIBBEAN SEA AND
THE GREATER ANTILLES.  THE GUIDANCE HAS BECOME LESS CONSISTENT
SINCE THE PREVIOUS ADVISORY.  WHILE THE CENTER OF THE GUIDANCE
ENVELOPE HAS CHANGED LITTLE...THE ECMWF HAS SHIFTED WELL TO THE
LEFT OF ITS PREVIOUS FORECAST AND NOW CALLS FOR A WESTWARD MOTION
AFTER ISAAC PASSES HISPANIOLA.  THE GFS ENSEMBLES HAVE ALSO SHIFTED
WESTWARD...ALTHOUGH THE ENSEMBLE MEAN STILL LIES NEAR THE FORECAST
TRACK.  THE NEW TRACK IS NUDGED A LITTLE TO THE NORTH OF THE
PREVIOUS TRACK BEFORE 72 HR...AND THEN IS NUDGED A LITTLE TO THE
RIGHT THEREAFTER.  THE TRACK FORECAST AFTER 72 HR LIES NEAR THE
LEFT EDGE OF THE GUIDANCE ENVELOPE...WITH ONLY THE ECMWF WELL TO
THE LEFT OF THE CURRENT FORECAST.  USERS ARE CAUTIONED THAT FIVE-DAY
TRACK ERRORS AVERAGE ABOUT 225 N MI.
 
ISAAC CONTINUES TO EXPERIENCE SOME LIGHT NORTHEASTERLY VERTICAL WIND
SHEAR...AND IT MAY NOT YET HAVE FULLY MIXED OUT THE DRY AIR THAT
HAS BEEN AFFECTING IT.  THE SHEAR IS FORECAST TO DIMINISH IN 12-24
HR...WHICH SHOULD ALLOW SOME STRENGTHENING.  THAT BEING SAID...THE
GFDL AND HWRF MODELS HAVE BACKED OFF ON THEIR FORECASTS OF
INTENSIFICATION...AND THE SHIPS AND LGEM MODELS ARE ALSO LESS
BULLISH.  BASED ON THIS...THE NEW INTENSITY FORECAST SHOWS A LITTLE
LESS STRENGTHENING THAN THE PREVIOUS ADVISORY.  THE INTENSITY
FORECAST AFTER 72 HR HAS AGAIN BEEN REDUCED DUE TO THE FORECAST
TRACK SHOWING INCREASED LAND INTERACTION WITH HISPANIOLA AND CUBA.
 
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/2100Z 15.4N  53.9W   35 KT  40 MPH
 12H  22/0600Z 15.6N  56.4W   40 KT  45 MPH
 24H  22/1800Z 15.9N  59.8W   45 KT  50 MPH
 36H  23/0600Z 16.3N  63.1W   50 KT  60 MPH
 48H  23/1800Z 16.6N  66.3W   65 KT  75 MPH
 72H  24/1800Z 17.0N  71.0W   75 KT  85 MPH
 96H  25/1800Z 19.5N  75.0W   75 KT  85 MPH
120H  26/1800Z 21.5N  78.0W   65 KT  75 MPH...INLAND
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 220249
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 PM AST TUE AUG 21 2012
 
THERE HAS BEEN NO AERIAL RECONNAISSANCE INTO ISAAC RECENTLY...BUT
THE CLOUD PATTERN OF THE STORM HAS NOT BECOME SIGNIFICANTLY BETTER
ORGANIZED OVER THE PAST FEW HOURS.  THE INTENSITY IS HELD AT 35 KT
WHICH IS IN AGREEMENT WITH A DVORAK INTENSITY ESTIMATE FROM TAFB.
ANOTHER HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE ISAAC
AT AROUND 0600 UTC.
 
THERE IS SOME SPREAD IN CENTER FIXES...BUT BASED ON GEOSTATIONARY
AND MICROWAVE IMAGERY THE INITIAL MOTION REMAINS ABOUT THE
SAME...275/16.  A WELL-DEFINED MID-TROPOSPHERIC RIDGE TO THE NORTH
OF THE TROPICAL CYCLONE SHOULD MAINTAIN THE WESTWARD TRACK FOR THE
NEXT COUPLE OF DAYS.  LATER IN THE FORECAST PERIOD...GLOBAL MODELS
DEPICT ISAAC NEARING A BREAK IN THE RIDGE NEAR FLORIDA.
CONSEQUENTLY THE FORWARD SPEED IS LIKELY TO SLOW...AND THE HEADING
TO GRADUALLY TURN TOWARD THE RIGHT...IN THE LATTER HALF OF THE
FORECAST PERIOD.  ALTHOUGH THE GFS HAS SHIFTED JUST A BIT TO THE
NORTH OF ITS PREVIOUS FORECAST...OVERALL THE TRACK GUIDANCE HAS NOT
CHANGED MUCH SINCE THE PREVIOUS CYCLE.  THE OFFICIAL FORECAST IS
VERY CLOSE TO THE LATEST HWRF TRACK AND NOT FAR FROM THE DYNAMICAL
CONSENSUS.
 
WATER VAPOR IMAGERY SUGGESTS THAT EAST-NORTHEASTERLY SHEAR IS
CURRENTLY AFFECTING ISAAC...BUT THE DYNAMICAL GUIDANCE PREDICTS A
DECREASE IN SHEAR WITH UPPER-LEVEL ANTICYCLONIC FLOW OVER THE
TROPICAL CYCLONE DURING THE NEXT SEVERAL DAYS.  THEREFORE
STRENGTHENING IS ANTICIPATED...AND ISAAC COULD BECOME A HURRICANE
WITHIN THE NEXT COUPLE OF DAYS.  LATER ON...THE INTENSITY FORECAST
IS COMPLICATED BY HOW MUCH THE CORE OF THE SYSTEM INTERACTS WITH
THE MOUNTAINOUS LAND MASSES OF HISPANIOLA AND EASTERN CUBA.  THE
OFFICIAL WIND SPEED FORECAST IS FAIRLY CLOSE TO THE STATISTICAL-
DYNAMICAL GUIDANCE FOR THE FIRST 48 HOURS AND THEN TRIES TO TAKE
INTO ACCOUNT THE LAND INTERACTION.  NEEDLESS TO SAY...THERE IS
CONSIDERABLE UNCERTAINTY IN THE INTENSITY OF ISAAC IN THE 3 TO 5
DAY TIME FRAME.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/0300Z 15.6N  55.6W   35 KT  40 MPH
 12H  22/1200Z 15.8N  58.1W   40 KT  45 MPH
 24H  23/0000Z 16.2N  61.2W   45 KT  50 MPH
 36H  23/1200Z 16.7N  64.3W   55 KT  65 MPH
 48H  24/0000Z 17.1N  67.1W   65 KT  75 MPH
 72H  25/0000Z 18.3N  72.0W   65 KT  75 MPH...INLAND
 96H  26/0000Z 20.5N  76.0W   70 KT  80 MPH...INLAND
120H  27/0000Z 23.0N  79.0W   70 KT  80 MPH...OVER WATER
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 220851
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 AM AST WED AUG 22 2012
 
SATELLITE IMAGERY INDICATES A LARGE CENTRAL DENSE OVERCAST FEATURE
HAS DEVELOPED OVER THE LOW-LEVEL CENTER...WHICH INCLUDES SOME COLD
CLOUD TOPS OF -82 TO -86C VERY NEAR THE CENTER. HOWEVER...THE SHARP 
INCREASE IN INNER-CORE CONVECTION HAS NOT YET TRANSLATED INTO ANY
SIGNIFICANT INTENSIFICATION. AN AIR FORCE RESERVE RECONNAISSANCE
AIRCRAFT INVESTIGATING ISAAC THIS MORNING HAS ONLY FOUND THE
CENTRAL PRESSURE TO BE 1003 MB AND 850 MB FLIGHT-LEVEL WINDS OF 47
KT...WHICH EQUATES TO ABOUT A 40-KT INTENSITY ESTIMATE. SFMR WINDS
IN VERY HEAVY RAIN HAVE BEEN AS HIGH AS 61 KT. THE BIAS-ADJUSTED
SFMR WINDS HAVE BEEN RUNNING AS HIGH AS 54 KT...BUT EVEN THOSE
VALUES APPEAR TO BE INFLATED. UNTIL THE AIRCRAFT COMPLETES ITS
MISSION... THE INITIAL INTENSITY WILL REMAIN AT 40 KT BASED ON THE
1003 MB PRESSURE-WIND RELATIONSHIP.
 
THE INITIAL MOTION ESTIMATE IS 270/15 KT. THE INITIAL POSITION IS A
BLEND OF THE RECON FIXES AND SATELLITE POSITIONS...AND CONTINUITY
WITH PREVIOUS FORECAST TRACK. THERE IS NO SIGNIFICANT CHANGE TO THE
PREVIOUS FORECAST TRACK OR REASONING. THE EAST-WEST ORIENTED
SUBTROPICAL RIDGE TO THE NORTH OF ISAAC ALONG 30N LATITUDE IS
FORECAST BY ALL OF THE GLOBAL MODELS TO REMAIN INTACT ACROSS
FLORIDA AND THE SOUTHEASTERN U.S. THROUGH 72 HOURS OR SO. AFTER
THAT...A BROAD MID- TO UPPER-LEVEL TROUGH CURRENTLY LOCATED OVER
THE CENTRAL U.S. FROM THE GREAT LAKES SOUTHWARD TO THE CENTRAL GULF
COAST IS EXPECTED TO DIG SOUTHWARD OVER THE NEXT 24 HOURS BEFORE
MOVING EASTWARD. THIS SHOULD RESULT IN AN EROSION OF THE RIDGE
ACROSS THE EASTERN GULF OF MEXICO AND THE SOUTHEASTERN U.S.
INCLUDING FLORIDA AND THE NORTHWESTERN BAHAMAS. THIS DEVELOPING
WEAKNESS IN THE RIDGE SHOULD ALLOW ISAAC TO TURN NORTHWESTWARD
ACROSS EASTERN AND CENTRAL CUBA BY DAYS 4 AND 5. THE NHC MODEL
GUIDANCE IS IN EXCELLENT AGREEMENT ON THIS EVOLVING SCENARIO WITH
THE ECMWF BEING THE LEFTMOST OF THE MODELS...AND THE GFDL AND HWRF
BEING THE RIGHTMOST OF THE MODELS. GIVEN THE RUN-TO-RUN CONSISTENCY
OF THE GFS AND UKMET MODELS...MORE WEIGHT HAS BEEN PLACED ON THOSE
SOLUTIONS...ESPECIALLY SINCE THEY HAVE A STRONGER AND VERTICALLY
DEEPER CYCLONE DEPICTED IN THE MODELS.

SHEAR ANALYSES FROM THE GFS-BASED SHIPS INTENSITY MODEL AND UW-CIMSS
INDICATE BOTH THE DEEP-LAYER AND MID-LEVEL SHEAR VALUES HAVE
DROPPED BELOW 10 KT...WHICH HAS FINALLY ALLOWED DEEP CONVECTION TO
DEVELOP AND PERSIST OVER THE LOW-LEVEL CENTER. THE SHEAR IS
FORECAST TO GRADUALLY DECREASE TO VALUES BELOW 5 KT BY 24 HOURS...
WHICH SHOULD ALLOW ISAAC TO STRENGTHEN TO A HURRICANE BY 48 HOURS.
AT 72 AND 96 HOURS...THE INTENSITY HAS BEEN DECREASED DUE TO
EXPECTED LAND INTERACTION WITH HAITI AND EASTERN CUBA. AFTER 96
HOURS...HOWEVER...ISAAC SHOULD BE MOVING BACK OVER THE VERY WARM
WATER BETWEEN CUBA AND FLORIDA. WITH SEA-SURFACE TEMPERATURES
EXPECTED TO BE NEAR 30C AND THE GFS AND UKMET MODELS DEPICTING A
EXTENSIVE UPPER-LEVEL OUTFLOW REGIME COMPLETE WITH DUAL OUTFLOW
CHANNELS TO THE NORTHWEST AND SOUTHEAST...STRENGTHENING APPEARS
LIKELY. THE OFFICIAL INTENSITY REMAINS ON THE CONSERVATIVE SIDE DUE
TO UNCERTAINTY IN HOW LONG AND HOW MUCH ISAAC WILL INTERACT WITH
HISPANIOLA AND CUBA...AND IS CLOSE TO A BLEND OF THE SHIPS...
DECAY-SHIPS...AND LGEM STATISTICAL-DYNAMICAL INTENSITY MODELS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  22/0900Z 15.5N  57.3W   40 KT  45 MPH
 12H  22/1800Z 15.9N  59.7W   45 KT  50 MPH
 24H  23/0600Z 16.3N  62.8W   55 KT  65 MPH
 36H  23/1800Z 16.8N  65.7W   65 KT  75 MPH
 48H  24/0600Z 17.3N  68.4W   75 KT  85 MPH
 72H  25/0600Z 18.8N  73.2W   65 KT  75 MPH...OVER WATER
 96H  26/0600Z 21.8N  77.1W   65 KT  75 MPH...OVER WATER
120H  27/0600Z 24.8N  80.0W   80 KT  90 MPH
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 221449
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 AM AST WED AUG 22 2012
 
THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT MONITORING ISAAC
DURING THE NIGHT REPORTED THAT THE INNER CORE WIND FIELD BECAME
DISORGANIZED AFTER 0600 UTC.  A COUPLE OF MICROWAVE OVERPASSES
SUGGEST THAT THE CIRCULATION CENTER BECAME ELONGATED DURING THIS
TIME....AND THE CENTER IS NOT READILY APPARENT IN FRENCH RADAR DATA
FROM MARTINIQUE AND GUADELOUPE.  THE INITIAL INTENSITY IS HELD AT
40 KT BASED ON AIRCRAFT-REPORTED WINDS NORTH OF THE CENTER.  WHILE
THE CENTRAL CORE IS DISORGANIZED...THE OVERALL STRUCTURE OF THE
STORM IS IMPROVING...AS SATELLITE IMAGERY SHOWS A LARGE OUTER BAND
FORMING AROUND THE CENTRAL CONVECTIVE FEATURE.
 
THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 280/15...AS IT IS UNCLEAR
HOW MUCH OF THE OBSERVED NORTHWARD NUDGE WAS DUE TO RE-FORMATION OF
THE CENTER. OTHER THAN THAT...THERE IS NO SIGNIFICANT CHANGE TO THE
PREVIOUS FORECAST TRACK OR REASONING DURING THE FIRST 48-72 HR OF
THE TRACK FORECAST. THE EAST-WEST ORIENTED SUBTROPICAL RIDGE TO THE
NORTH OF ISAAC ALONG 30N LATITUDE IS FORECAST BY ALL OF THE GLOBAL
MODELS TO REMAIN INTACT ACROSS FLORIDA AND THE SOUTHEASTERN U.S.
DURING THAT TIME.  THIS EARLY PART OF THE FORECAST TRACK IS AN
UPDATE OF THE PREVIOUS FORECAST.  AFTER THAT TIME...THE RIDGE IS
EXPECTED TO WEAKEN SOMEWHAT AS A MID/UPPER-LEVEL TROUGH MOVES ONTO
THE EASTERN UNITED STATES.  THE MODELS DIVERGE ON THEIR FORECASTS
OF THE RIDGE.  THE ECMWF DOES NOT BREAK THE RIDGE...AND THUS
FORECASTS A MORE WESTWARD MOTION NEAR OR SOUTH OF CUBA.  THE
CANADIAN AND NOGAPS HAVE A LARGE BREAK IN THE RIDGE AND TURN ISAAC
NORTHWARD EAST OF FLORIDA.  THE UKMET HAS A BREAK IN THE RIDGE OVER
THE NORTHERN GULF COAST AND MOVES THE CYCLONE OVER THE FLORIDA
PENINSULA.  THE GFS SHOWS A BREAK IN THE RIDGE EAST OF FLORIDA...
BUT FORECASTS ISAAC TO BYPASS THE BREAK AND MOVE NEAR THE SOUTHWEST
COAST OF FLORIDA.  THIS DECREASED-CONFIDENCE PORTION OF THE
FORECAST TRACK IS SHIFTED A LITTLE WEST OF THE PREVIOUS TRACK TO
LIE NEAR THE CONSENSUS MODELS.
 
WATER VAPOR IMAGERY AND MICROWAVE TOTAL PRECIPITABLE WATER DATA SHOW
DRY AIR TO THE NORTHEAST OF ISAAC...AND A LACK OF CONVECTION IN
THIS AREA SUGGESTS SOME OF THIS AIR IS ENTRAINING INTO THE CYCLONE.
OTHERWISE...ENVIRONMENTAL CONDITIONS APPEAR FAVORABLE FOR
INTENSIFICATION UNTIL THE CENTER REACHES HISPANIOLA IN ABOUT 48 HR.
AFTER THAT...THE INTENSITY WILL BE DETERMINED BY HOW MUCH TIME ISAAC
SPENDS OVER LAND.  THE NEW FORECAST IS SIMILAR TO THE PREVIOUS
FORECAST THROUGH 48 HR...THEN IS REDUCED A LITTLE BASED ON
INCREASED LAND INTERACTION IN THE NEW FORECAST TRACK.
 
A HURRICANE WARNING WILL LIKELY BE REQUIRED FOR PORTIONS OF THE
DOMINICAN REPUBLIC THIS AFTERNOON.  IT SHOULD BE NOTED THAT WHILE
NONE OF THE FORECAST POINTS ARE OVER LAND...THE CYCLONE IS FORECAST
TO MOVE OVER HISPANIOLA AND CUBA FROM 48-96 HR.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/1500Z 15.9N  59.3W   40 KT  45 MPH
 12H  23/0000Z 16.3N  61.8W   45 KT  50 MPH
 24H  23/1200Z 16.8N  64.8W   50 KT  60 MPH
 36H  24/0000Z 17.3N  67.8W   60 KT  70 MPH
 48H  24/1200Z 17.8N  70.3W   75 KT  85 MPH
 72H  25/1200Z 19.5N  74.5W   60 KT  70 MPH
 96H  26/1200Z 22.5N  78.5W   60 KT  70 MPH
120H  27/1200Z 25.5N  81.5W   70 KT  80 MPH
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 222039
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 PM AST WED AUG 22 2012

SATELLITE...AIRCRAFT...RADAR...AND SURFACE OBSERVATIONS INDICATE
THAT ISAAC HAS A BROAD CENTRAL AREA OF LIGHT WINDS WITH MULTIPLE
VORTICITY MAXIMA EMBEDDED.  THE LOWEST PRESSURES ARE IN AN AREA
NEAR GUADELOUPE...WHICH IS USED AS THE CURRENT CENTER SINCE IT HAS
SOME CONTINUITY WITH THE CENTER PREVIOUSLY BEING TRACKED. 
HOWEVER...THE MEAN CENTER IS LIKELY TO THE SOUTHEAST OF THE
ADVISORY POSITION.  SOME ADJUSTMENT OF THE CENTER POSITION MAY BE
NECESSARY WHEN THE CENTRAL CORE AGAIN CONSOLIDATES.  THE INITIAL
INTENSITY IS HELD AT 40 KT...ALTHOUGH THE HURRICANE HUNTER AIRCRAFT
DATA SUGGESTS THIS COULD BE GENEROUS.
 
THE INITIAL MOTION IS NOW A SOMEWHAT UNCERTAIN 280/19.  OTHER THAN
THE CENTER POSITION ISSUES...THERE IS NO SIGNIFICANT CHANGE TO THE
FORECAST REASONING DURING THE FIRST 48 HR OF THE TRACK FORECAST. THE
EAST-WEST ORIENTED SUBTROPICAL RIDGE TO THE NORTH OF ISAAC ALONG
30N LATITUDE IS FORECAST BY ALL OF THE GLOBAL MODELS TO REMAIN
INTACT ACROSS FLORIDA AND THE SOUTHEASTERN U.S. DURING THAT TIME. 
THIS EARLY PART OF THE FORECAST TRACK IS SHIFTED A LITTLE TO THE
SOUTH OF THE PREVIOUS FORECAST BASED ON THE OBSERVED POSITION AND
MOTION.  AFTER 48 HR...THE RIDGE IS EXPECTED TO WEAKEN AS A
MID/UPPER-LEVEL TROUGH MOVES ONTO THE EASTERN UNITED STATES.  THE
GLOBAL MODELS HAVE COME INTO BETTER AGREEMENT SINCE THE LAST
ADVISORY...WITH THE NOGAPS AND CANADIAN MODELS SHIFTING TO THE WEST
AND THE ECMWF TO THE NORTH.  HOWEVER...THE ECMWF CONTINUES TO SHOW
A STRONGER RIDGE...AND THUS SHOWS A MORE WESTERLY MOTION THAN THE
OTHER MODELS.  THE 72-120 HR PORTION OF THE FORECAST TRACK IS
SIMILAR TO THE PREVIOUS FORECAST AND LIES NEAR THE CONSENSUS
MODELS.  THERE REMAINS CONSIDERABLE UNCERTAINTY AS TO WHICH PORTIONS
OF FLORIDA...IF ANY...COULD BE AFFECTED BY ISAAC.

WATER VAPOR IMAGERY AND MICROWAVE TOTAL PRECIPITABLE WATER DATA
CONTINUE TO SHOW DRY AIR TO THE NORTHEAST OF ISAAC...AND A LACK OF
CONVECTION IN THIS AREA SUGGESTS SOME OF THIS AIR IS ENTRAINING
INTO THE CYCLONE AND DISRUPTING THE CONVECTIVE STRUCTURE.  GIVEN
THE CURRENT STRUCTURE...THE NEW INTENSITY FORECAST CALLS FOR LITTLE
CHANGE IN STRENGTH FOR THE NEXT 12 HR...FOLLOWED BY INTENSIFICATION
INTO A HURRICANE BY 48 HR SIMILAR TO THE PREVIOUS ADVISORY.  AFTER
48 HR...THE MAIN FACTOR CONTROLLING THE INTENSITY IS THE AMOUNT OF
LAND INTERACTION.  THIS LOW-CONFIDENCE PART OF THE INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY BUT ABOVE THE INTENSITY
CONSENSUS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/2100Z 16.0N  61.2W   40 KT  45 MPH
 12H  23/0600Z 16.3N  63.6W   40 KT  45 MPH
 24H  23/1800Z 16.7N  66.7W   50 KT  60 MPH
 36H  24/0600Z 17.2N  69.4W   60 KT  70 MPH
 48H  24/1800Z 17.9N  71.6W   70 KT  80 MPH...INLAND
 72H  25/1800Z 20.5N  75.5W   60 KT  70 MPH...INLAND
 96H  26/1800Z 23.5N  79.5W   60 KT  70 MPH...OVER WATER
120H  27/1800Z 26.5N  82.5W   70 KT  80 MPH
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 230257
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 PM AST WED AUG 22 2012
 
AN AIR FORCE HURRICANE HUNTER AIRCRAFT INVESTIGATED ISAAC SEVERAL
HOURS AGO AND FOUND THAT THE CENTER WAS STILL NOT WELL-DEFINED AND
THE INTENSITY ESTIMATE OF 40 KT WAS PROBABLY A LITTLE ON THE HIGH
SIDE.  HOWEVER...DROPSONDE DATA FROM A NOAA AIRCRAFT CURRENTLY
INVESTIGATING THE STORM SUGGEST THAT THE CENTER HAS PROBABLY BECOME
A LITTLE BETTER DEFINED AND THAT THE MINIMUM PRESSURE HAS DROPPED A
BIT.  THERE HAS ALSO BEEN AN INCREASE IN COLD-TOPPED CONVECTION
NEAR AND OVER THE ESTIMATED CENTER SO THE CURRENT INTENSITY IS HELD
AT 40 KT.  ISAAC HAS DEVELOPED AN IMPRESSIVE UPPER-LEVEL OUTFLOW
PATTERN AND DYNAMICAL GUIDANCE SHOWS THAT THE VERTICAL SHEAR SHOULD
REMAIN WEAK DURING THE NEXT SEVERAL DAYS.  THEREFORE THE PRIMARY
IMPEDIMENT TO STRENGTHENING SHOULD BE THE INTERACTION WITH THE
MOUNTAINOUS TERRAIN OF HISPANIOLA AND EASTERN CUBA.  THE MOST
RECENT RUNS OF THE HWRF AND GFDL SHOW SIMILAR AMOUNTS OF LAND
INTERACTION BUT ARE NOT IN GOOD AGREEMENT ON THE INTENSITY FORECAST
AS THE FORMER MODEL SHOWS MUCH LESS STRENGTHENING THAN THE LATTER.
THE OFFICIAL WIND SPEED FORECAST IS IN REASONABLE AGREEMENT WITH
THE LATEST STATISTICAL-DYNAMICAL GUIDANCE.

AFTER A SLIGHT SOUTHWARD RELOCATION OF THE CENTER...THE INITIAL
MOTION CONTINUES BASICALLY WESTWARD OR 270/17.  ISAAC SHOULD
CONTINUE TO MOVE WESTWARD TO WEST-NORTHWESTWARD FOR THE NEXT COUPLE
OF DAYS ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE.  THE
GLOBAL MODELS CONTINUE TO DEPICT A BREAK IN THE RIDGE IN THE
VICINITY OF FLORIDA IN SEVERAL DAYS...WHICH SHOULD INDUCE A MORE
NORTHWARD COMPONENT OF MOTION.  THE ECMWF MODEL SHOWS LESS OF A
BREAK IN THE RIDGE THAN THE GFS SOLUTION.  CONSEQUENTLY...THE ECMWF
TRACK IS SOMEWHAT TO THE SOUTHWEST OF MOST OF THE OTHER TRACK
MODELS WHICH WOULD LESSEN THE THREAT TO FLORIDA.  THE OFFICIAL
TRACK FORECAST FOR THIS ADVISORY IS QUITE CLOSE TO THE PREVIOUS ONE
AND ALSO VERY CLOSE TO THE DYNAMICAL MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  23/0300Z 15.8N  63.0W   40 KT  45 MPH
 12H  23/1200Z 16.2N  65.4W   45 KT  50 MPH
 24H  24/0000Z 16.9N  68.1W   55 KT  65 MPH
 36H  24/1200Z 17.5N  70.5W   65 KT  75 MPH
 48H  25/0000Z 18.6N  72.7W   55 KT  65 MPH
 72H  26/0000Z 21.5N  77.0W   60 KT  70 MPH...ON NORTH COAST OF CUBA
 96H  27/0000Z 24.0N  80.5W   65 KT  75 MPH
120H  28/0000Z 27.0N  83.5W   70 KT  80 MPH
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 230858
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 AM AST THU AUG 23 2012
 
AN AIR FORCE RECONNAISSANCE AIRCRAFT INVESTIGATING ISAAC THIS
MORNING HAS FOUND A POORLY DEFINED INNER CORE WITH A LARGE AREA OF
LIGHT WINDS AROUND A CENTER...WHICH IS SIMILAR TO WHAT AN EARLIER
NOAA RESEARCH MISSION INDICATED. RADAR DATA FROM GUADELOUPE AND SAN
JUAN ALSO INDICATE A POORLY DEFINED INNER CORE CONVECTIVE PATTERN.
RATHER THAN INITIALIZE THE CENTER OF ISAAC WELL TO THE SOUTH OF THE
PREVIOUS TRACK...I HAVE OPTED TO USE A BLEND OF THE RECON FIXES...
SATELLITE IMAGERY...DATA FROM NEARBY NOAA BUOY 42060...AND A 06Z
CONSENSUS FORECAST POSITION FROM THE GFS...ECMWF...AND UKMET
MODELS. THE INITIAL INTENSITY WAS ALSO DECREASED TO 35 KT BASED ON
DATA FROM THE RECON AIRCRAFT AND NOAA BUOY 42060.

THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 270/12 KT. THE 00Z
GFS...ECMWF...AND UKMET MODELS DID AN OUTSTANDING JOB PREDICTING
THE RECENT SOUTHWESTWARD JOG OR REFORMATION OF THE CENTER OF ISAAC.
THOSE SAME MODELS ARE ALSO FORECASTING ISAAC TO MAKE A SHARP JOG TO
THE NORTHWEST OVER THE NEXT 12-24 HOURS...AND THEN STEADY OFF ON A
GENERAL WEST-NORTHWESTWARD MOTION THROUGH 48 HOURS. AFTER THAT...
THE GLOBAL AND REGIONAL MODELS HAVE COME INTO BETTER AGREEMENT ON
ISAAC MOVING NORTHWESTWARD TOWARD A BREAK IN THE SUBTROPICAL RIDGE
THAT IS FORECAST TO DEVELOP AFTER 72 HOURS ACROSS FLORIDA AND THE
EASTERN GULF OF MEXICO.  THE ECMWF MODEL HAS CONTINUED ITS EASTWARD
SHIFT OVER THE PAST 36 HOURS...AND EVEN THE LATEST NOGAPS AND
CANADIAN MODEL RUNS HAVE SHIFTED WELL TO THE WEST ACROSS THE
FLORIDA PENINSULA ARE NOW NO LONGER CONSIDERED TO BE OUTLIERS. DUE
TO LESS SPREAD IN THE LATEST NHC MODEL GUIDANCE...AND THE FACT THAT
ECMWF HAS SHIFTED CLOSER TO THE PREVIOUS FORECAST AT DAYS 4 AND
5...THE OFFICIAL FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS
ADVISORY TRACK...AND IS CLOSE TO THE DYNAMICAL CONSENSUS MODELS
TVCA AND TV15.

UPPER-AIR DATA FROM ST. MAARTEN AT 00Z CONFIRMS THE DRY AIR IN THE
MID-LEVELS OF THE ATMOSPHERE BETWEEN 600 AND 300 MB AS ALLUDED TO
IN PREVIOUS DISCUSSIONS. THIS LAYER OF VERY DRY AIR HAS BEEN
HINDERING CONVECTIVE DEVELOPMENT IN THE NORTHEASTERN QUADRANT FOR
THE PAST 3-4 DAYS. HOWEVER...THE GLOBAL MODELS ARE IN GOOD
AGREEMENT ON THE DRY AIR MIXING OUT OVER THE NEXT 36 HOURS AND THE
INNER CORE BECOMING QUITE MOIST...WHICH SHOULD ALLOW FOR SOME
STEADY INTENSIFICATION TO OCCUR BEFORE ISAAC INTERACTS WITH THE
MOUNTAINOUS TERRAIN OF HISPANIOLA. GIVEN THE IMPRESSIVE UPPER-LEVEL
OUTFLOW PATTERN THAT THE CYCLONE HAS DEVELOPED...ISAAC IS STILL
EXPECTED TO BECOME A HURRICANE BY 36 HOURS. AFTER THAT...HOWEVER...
THE THE PRIMARY IMPEDIMENT TO STRENGTHENING WILL BE THE INTERACTION
WITH THE LAND MASSES OF HISPANIOLA AND EASTERN CUBA.  HOW MUCH THE
INNER CORE OF ISAAC IS DISRUPTED WHILE OVER LAND WILL DETERMINE
JUST HOW MUCH RE-STRENGTHENING WILL OCCUR ONCE THE CENTER MOVES
BACK OVER WATER AFTER 72 HOURS. THE OFFICIAL INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS FORECAST AND IS IN REASONABLE AGREEMENT
WITH THE DECAY-SHIPS AND LGEM INTENSITY MODELS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/0900Z 15.3N  64.0W   35 KT  40 MPH
 12H  23/1800Z 16.2N  65.9W   40 KT  45 MPH
 24H  24/0600Z 16.9N  68.4W   50 KT  60 MPH
 36H  24/1800Z 17.8N  71.1W   65 KT  75 MPH
 48H  25/0600Z 19.1N  73.4W   55 KT  65 MPH
 72H  26/0600Z 21.8N  77.4W   60 KT  70 MPH...INLAND
 96H  27/0600Z 24.4N  80.9W   65 KT  75 MPH...OVER WATER
120H  28/0600Z 27.4N  83.7W   70 KT  80 MPH
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 231453
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 AM AST THU AUG 23 2012
 
THE SATELLITE APPEARANCE OF ISAAC HAS IMPROVED SOMEWHAT THIS
MORNING...WITH MULTIPLE CONVECTIVE BANDS DEVELOPING AROUND THE
CENTER.  HOWEVER...REPORTS FROM AIR FORCE RESERVE AND NOAA
HURRICANE HUNTER AIRCRAFT INDICATE THAT THE CENTRAL CORE OF ISAAC
REMAINS POORLY ORGANIZED...WITH MULTIPLE LOW-LEVEL VORTICITY CENTERS
ROTATING AROUND A LARGE AREA OF LIGHT WINDS.  IN ADDITION...THE
CENTER IN AIRCRAFT DATA IS NORTH OF THE CENTER SUGGESTED BY THE
SATELLITE IMAGERY.  A COMBINATION OF FLIGHT-LEVEL...DROPSONDE...AND
SFMR WINDS SUGGEST THAT THE INITIAL INTENSITY IS NEAR 35 KT.

THE OVERALL CIRCULATION OF ISAAC IS A LITTLE FARTHER SOUTH THAN 12
HR AGO.  HOWEVER...IT SEEMS TO HAVE RESUMED A WESTWARD MOTION AT
ABOUT 13 KT.  THE TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT THAT
ISAAC SHOULD MOVE WEST-NORTHWESTWARD FOR THE NEXT 36-48 HR...
STEERED BY THE SUBTROPICAL RIDGE TO THE NORTH.  AFTER THAT...THE
STORM SHOULD APPROACH A WEAKNESS OR BREAK IN THE RIDGE OVER FLORIDA
AND THE EASTERN GULF OF MEXICO. THE NEW FORECAST TRACK IS SHIFTED A
LITTLE TO THE WEST OF THE PREVIOUS TRACK BASED ON CURRENT POSITION
AND LIES DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE NEAR THE
CONSENSUS MODELS.  IT SHOULD BE NOTED...THOUGH...THAT NEAR THE 96
HR POINT THE GUIDANCE MODELS ARE SPREAD BETWEEN SOUTHEASTERN
FLORIDA AND WESTERN CUBA...AND AT 120 HR THEY ARE BETWEEN
NORTHEASTERN FLORIDA AND THE CENTRAL GULF OF MEXICO.  THUS...
SIGNIFICANT UNCERTAINTY REMAINS ABOUT THE THREAT ISAAC POSES TO
FLORIDA.

IN THE SHORT TERM...THE STRUCTURE OF ISAAC SUGGESTS THAT ONLY SLOW
STRENGTHENING IS LIKELY.  HOWEVER...THE ENVIRONMENTAL CONDITIONS
ARE FAVORABLE FOR RAPID INTENSIFICATION...WHICH COULD OCCUR IF THE
CYCLONE DEVELOPS A WELL-DEFINED INNER CORE.  BASED ON THIS...THE
INTENSITY FORECAST CONTINUES TO SHOW HURRICANE STRENGTH BEFORE THE
SYSTEM REACHES HISPANIOLA IN ABOUT 36 HR.  AFTER THAT...PASSAGE OVER
HISPANIOLA AND CUBA SHOULD CAUSE SOME WEAKENING...FOLLOWED BY
LITTLE CHANGE OF STRENGTH FROM 48-72 HR.  THE INTENSITY FORECAST
SHOWS A LITTLE MORE STRENGTHENING OVER THE GULF OF MEXICO DUE TO
THE FORECAST TRACK BEING A LITTLE FARTHER FROM THE FLORIDA
PENINSULA THAN BEFORE.  THE INTENSITY FORECAST IS BASED ON A BLEND
OF THE PREVIOUS FORECAST AND THE SHIPS/LGEM MODELS...AND IT IS WELL
ABOVE THE INTENSITY CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 15.6N  65.4W   35 KT  40 MPH
 12H  24/0000Z 16.1N  67.4W   40 KT  45 MPH
 24H  24/1200Z 16.9N  70.0W   50 KT  60 MPH
 36H  25/0000Z 18.0N  72.4W   65 KT  75 MPH
 48H  25/1200Z 19.3N  74.6W   55 KT  65 MPH
 72H  26/1200Z 22.0N  78.5W   55 KT  65 MPH...INLAND
 96H  27/1200Z 24.5N  81.5W   65 KT  75 MPH...OVER WATER
120H  28/1200Z 27.5N  84.5W   75 KT  85 MPH
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 232055
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 PM AST THU AUG 23 2012

LOCATING THE CENTER OF ISAAC IS A BIT PROBLEMATIC THIS AFTERNOON. 
WHILE THE CYCLONE HAS A LARGE AND WELL-DEFINED OUTER
CIRCULATION...THE INNER CORE HAS NOT CONSOLIDATED AND THERE ARE
STILL MULTIPLE VORTICITY CENTERS ROTATING AROUND THE MEAN CENTER. 
HIGHLIGHTING THE ISSUE ARE DATA FROM NOAA BUOY 42059...WHICH HAS
REPORTED 25-30 KT SOUTHWESTERLY WINDS AT A POSITION SOUTHWEST OF
THE LATEST HURRICANE HUNTER AIRCRAFT FIXES...WHICH IN TURN WERE
SOUTH OF THE CENTER TRACKED IN THE PREVIOUS ADVISORY.  THE INITIAL
POSITION IS A BLEND OF ALL THESE FEATURES.  THE INITIAL INTENSITY
REMAINS 35 KT BASED ON THE HURRICANE HUNTER DATA.

THE SOMEWHAT UNCERTAIN INITIAL MOTION IS 285/14.  THE TRACK MODEL
GUIDANCE IS IN GOOD AGREEMENT THAT ISAAC SHOULD MOVE GENERALLY
WEST-NORTHWESTWARD FOR THE NEXT 48-72 HR...AND THIS PART OF THE NEW
FORECAST TRACK IS VERY SIMILAR TO THE PREVIOUS TRACK.  AFTER THAT
TIME...THE GUIDANCE HAS SHIFTED A LITTLE WESTWARD IN RESPONSE TO
THE GLOBAL MODELS FORECASTING THE WEAKNESS IN THE SUBTROPICAL RIDGE
TO BE SOMEWHAT FARTHER WEST THAN BEFORE.  THE ECMWF IN PARTICULAR
HAS MADE A SIGNIFICANT SHIFT...SHOWING A WEST-NORTHWESTWARD MOTION
INTO THE CENTRAL GULF OF MEXICO BY DAY 5.  DESPITE THE GENERAL
WESTWARD SHIFT...THE HWRF AND CANADIAN MODELS STILL CALL FOR ISAAC
TO MOVE UP THE FLORIDA PENINSULA.  THUS... SIGNIFICANT UNCERTAINTY
REMAINS ABOUT THE THREAT ISAAC POSES TO FLORIDA AND OTHER PORTIONS
OF THE GULF COAST.  THE 96-120 HR POINTS HAVE BEEN SHIFTED A LITTLE
WESTWARD FROM THE PREVIOUS ADVISORY AND LIE NEAR THE CENTER OF THE
GUIDANCE ENVELOPE AND THE CONSENSUS MODELS.

IN THE SHORT TERM...THE STRUCTURE OF ISAAC SUGGESTS THAT ONLY SLOW
STRENGTHENING IS LIKELY.  HOWEVER...THE ENVIRONMENTAL CONDITIONS
ARE FAVORABLE FOR RAPID INTENSIFICATION...WHICH COULD OCCUR IF THE
CYCLONE DEVELOPS A WELL-DEFINED INNER CORE.  WHILE THE OFFICIAL
FORECAST NO LONGER SHOWS IT...ISAAC COULD REACH HURRICANE INTENSITY
ABOUT THE TIME IT MAKES LANDFALL IN HISPANIOLA BETWEEN 24-36 HR. 
AFTER THAT...PASSAGE OVER HISPANIOLA AND CUBA SHOULD CAUSE SOME
WEAKENING. THE INTENSITY FORECAST SHOWS STRENGTHENING OVER THE GULF
OF MEXICO...AND THE CURRENT 120 HR INTENSITY COULD BE CONSERVATIVE
IF THE GLOBAL MODEL UPPER-LEVEL WIND FORECASTS VERIFY.  THE NEW
INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS FORECAST AND REMAINS
STRONGER THAN THE INTENSITY CONSENSUS.

THE NOAA G-IV JET AND AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
ARE CURRENTLY CONDUCTING A SYNOPTIC SURVEILLANCE MISSION AROUND
ISAAC.  THE DATA WILL BE AVAILABLE FOR THE 0000 UTC MODEL RUNS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/2100Z 16.0N  67.1W   35 KT  40 MPH
 12H  24/0600Z 16.6N  69.0W   40 KT  45 MPH
 24H  24/1800Z 17.5N  71.5W   50 KT  60 MPH
 36H  25/0600Z 18.9N  74.0W   60 KT  70 MPH
 48H  25/1800Z 20.3N  76.2W   55 KT  65 MPH...INLAND
 72H  26/1800Z 23.0N  80.0W   50 KT  60 MPH...OVER WATER
 96H  27/1800Z 25.5N  83.0W   65 KT  75 MPH
120H  28/1800Z 28.5N  85.5W   75 KT  85 MPH
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 240250
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 PM AST THU AUG 23 2012

OBSERVATIONS FROM A NOAA HURRICANE HUNTER AIRCRAFT SUGGEST THAT
ISAAC HAS STRENGTHENED ONLY SLIGHTLY THIS EVENING.  FLIGHT-LEVEL
AND SFMR-OBSERVED SURFACE WINDS FROM THE AIRCRAFT SUGGEST THAT THE
CURRENT INTENSITY IS NEAR 40 KT.  THE STORM CONTINUES TO HAVE
FAIRLY STRONG UPPER-LEVEL OUTFLOW AND...IF THE INNER CORE BECOMES
BETTER DEFINED...HAS AN OPPORTUNITY TO STRENGTHEN AS LONG AS IT
REMAINS OVER WATER.  HOWEVER...THE CENTER OF THE STORM IS FORECAST
TO MOVE OVER SOUTHWESTERN HISPANIOLA IN 12 HOURS OR SO...AND THIS
WOULD HALT ANY INTENSIFICATION.  A LITTLE LATER ON...LAND
INTERACTIONS WITH EASTERN CUBA WOULD ALSO INHIBIT INTENSIFICATION
OR CAUSE WEAKENING.  ISAAC WILL LIKELY RESTRENGTHEN WHEN IT MOVES
OVER THE STRAITS OF FLORIDA AND THE EASTERN GULF OF MEXICO IN THE
LATTER PART OF THE FORECAST PERIOD.  HOWEVER IT SHOULD BE NOTED
THAT THERE IS SIGNIFICANT UNCERTAINTY IN TROPICAL CYCLONE INTENSITY
PREDICTIONS AT 3-5 DAYS.

THE INITIAL MOTION ESTIMATE IS 290/16.  A MID-TROPOSPHERIC TROUGH
OVER THE SOUTHEASTERN U.S. IS CAUSING A BREAK IN THE SUBTROPICAL
RIDGE.  IN RESPONSE TO THIS...ISAAC SHOULD TURN TOWARD A MORE
NORTHWESTWARD HEADING OVER THE NEXT FEW DAYS.  THE MODEL CONSENSUS
HAS SHIFTED A BIT TO THE RIGHT DURING THE FIRST HALF OF THE FORECAST
PERIOD...PRIMARILY DUE TO AN EASTWARD SHIFT OF THE LATEST GFS
TRACK.  THE OFFICIAL FORECAST IS NUDGED A BIT TO THE RIGHT OF
THE PREVIOUS ONE AND IS SOMEWHAT FASTER BASED ON THE LATEST MODEL
GUIDANCE.

THE INITIAL AND FORECAST WIND RADII HAVE BEEN EXPANDED BASED ON BUOY
AND SHIP DATA.  IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK
BECAUSE OF FORECAST UNCERTAINTIES AND THE FACT THAT ISAAC HAS A
LARGE AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.

A SYNOPTIC SURVEILLANCE MISSION BY THE NOAA G-IV JET AIRCRAFT HAS
BEEN CONDUCTED TO COLLECT ATMOSPHERIC OBSERVATIONS IN THE
LARGE-SCALE ENVIRONMENT OF ISAAC.  THESE DATA WILL BE ASSIMILATED
INTO THE 0000 UTC RUNS OF THE GLOBAL MODELS...AND SHOULD IMPROVE
THE ACCURACY OF THEIR FORECASTS FOR THE NEXT ADVISORY CYCLE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0300Z 16.7N  68.7W   40 KT  45 MPH
 12H  24/1200Z 17.5N  70.7W   55 KT  65 MPH
 24H  25/0000Z 18.8N  73.1W   45 KT  50 MPH
 36H  25/1200Z 20.2N  75.4W   45 KT  50 MPH...INLAND
 48H  26/0000Z 21.8N  77.7W   45 KT  50 MPH...INLAND
 72H  27/0000Z 24.8N  82.0W   55 KT  65 MPH...OVER WATER
 96H  28/0000Z 27.5N  85.5W   70 KT  80 MPH
120H  29/0000Z 30.0N  88.0W   80 KT  90 MPH
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 240859
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 AM EDT FRI AUG 24 2012
 
DATA FROM THE HURRICANE HUNTER AIRCRAFT INDICATE THAT ISAAC REMAINS
POORLY ORGANIZED. WHILE THE 850-MB FLIGHT LEVEL CENTER WAS WELL
SOUTH OF THE PREVIOUSLY ESTIMATED SURFACE CENTER LOCATION...
DROPSONDE DATA SUGGEST THAT THE SURFACE CENTER REMAINS FARTHER
NORTH. FLIGHT LEVEL AND SFMR WINDS SUPPORT MAINTAINING THE
INTENSITY AT 40 KT FOR THIS ADVISORY...WHILE THE AIRCRAFT FOUND A
MINIMUM PRESSURE OF 1000 MB. GIVEN THE CURRENT LACK OF ORGANIZATION
OF THE INNER CORE...ONLY LIMITED STRENGTHENING IS FORECAST BEFORE
THE CYCLONE BEGINS TO INTERACT WITH HISPANIOLA IN THE NEXT 24
HOURS. AFTER THAT TIME LITTLE CHANGE IS FORECAST AS ISAAC INTERACTS
WITH PORTIONS OF CUBA. LATER IN THE PERIOD...ISAAC SHOULD HAVE AN
OPPORTUNITY TO STRENGTHEN OVER THE STRAITS OF FLORIDA AND THE GULF
OF MEXICO...AND THE NHC FORECAST IS CLOSE TO THE LGEM MODEL AT DAYS
4 AND 5. IT SHOULD BE NOTED THAT THERE IS SIGNIFICANT UNCERTAINTY
IN TROPICAL CYCLONE INTENSITY PREDICTIONS AT 3 TO 5 DAYS.
 
THE LONG TERM INITIAL MOTION ESTIMATE IS A HIGHLY UNCERTAIN
275/13...AS THE INITIAL POSITION ESTIMATE IS BASED ON A BLEND OF
RECENT FIXES AND CONTINUITY. THE TRACK MODEL GUIDANCE CONTINUES TO
BE IN GENERALLY GOOD AGREEMENT ON THE RESUMPTION OF A WEST-
NORTHWESTWARD AND THEN NORTHWESTWARD MOTION IN THE NEXT 24 HOURS AS
THE SUBTROPICAL RIDGE NORTH OF ISAAC WEAKENS. THIS GENERAL MOTION
SHOULD CONTINUE THROUGH DAY 4...WHEN A TURN MORE TOWARD THE NORTH
IS SHOWN AS A SHORTWAVE TROUGH AMPLIFIES OVER THE MISSISSIPPI
VALLEY. LATE IN THE PERIOD THE TRACK MODEL GUIDANCE IS IN BETTER
AGREEMENT ON THIS SCENARIO...AS THE ECMWF HAS TRENDED EASTWARD
TOWARD THE REST OF THE MODELS THIS CYCLE. THE NEW NHC FORECAST HAS
BEEN ADJUSTED ABOUT A DEGREE SOUTHWARD IN THE FIRST 12 HOURS DUE TO
THE INITIAL POSITION AND MOTION...AND IS THEN BLENDED BACK TOWARD
THE PREVIOUS TRACK BY 48 HOURS. AFTER THAT TIME...THE NHC FORECAST
IS ESSENTIALLY AN UPDATE OF THE PREVIOUS ONE...AND IS BETWEEN THE
ECMWF ON THE LEFT AND THE GFS AND TVCA CONSENSUS ON THE RIGHT. 
 
IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK DUE TO UNCERTAINTIES
IN THE INITIAL LOCATION AND THE TRACK FORECAST...AND THE FACT THAT
ISAAC HAS A LARGE AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED
WITH IT. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0900Z 16.1N  70.0W   40 KT  45 MPH
 12H  24/1800Z 17.0N  71.9W   50 KT  60 MPH
 24H  25/0600Z 18.8N  74.1W   45 KT  50 MPH
 36H  25/1800Z 20.6N  76.7W   45 KT  50 MPH...INLAND
 48H  26/0600Z 22.4N  78.9W   45 KT  50 MPH...OVER WATER
 72H  27/0600Z 25.0N  82.5W   55 KT  65 MPH
 96H  28/0600Z 28.0N  86.0W   65 KT  75 MPH
120H  29/0600Z 30.5N  87.5W   75 KT  85 MPH...INLAND
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 241455
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 AM EDT FRI AUG 24 2012

RECONNAISSANCE AIRCRAFT DATA AND SATELLITE IMAGERY INDICATE THAT
ISAAC HAS BECOME BETTER ORGANIZED DURING THE PAST SEVERAL HOURS. 
WHILE THE CIRCULATION CENTER REMAINS ELONGATED EAST-TO-WEST WITH
MULTIPLE EMBEDDED VORTICITY MAXIMA...THE LARGE CENTRAL AREA OF
LIGHT WINDS HAS SHRUNK AS THE STRONGEST WINDS MOVE CLOSER TO THE
CENTER.  AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT REPORTED
66 KT FLIGHT-LEVEL WINDS AT 850 MB NORTHEAST OF THE CENTER...ALONG
WITH SFMR BIAS-CORRECTED WIND ESTIMATES NEAR 50 KT.  BASED ON THESE
DATA...THE INITIAL INTENSITY IS INCREASED TO 50 KT.

THE 12Z POSITION USED A MEAN CENTER...WHICH RESULTED IN A SOUTHWARD
ADJUSTMENT.  SINCE THEN...ISAAC APPEARS TO HAVE ACQUIRED A STRONGER
NORTHWARD COMPONENT OF MOTION...AND THE INITIAL MOTION IS A
SOMEWHAT UNCERTAIN 295/12.  THE TRACK MODEL GUIDANCE IS IN GOOD
AGREEMENT THAT ISAAC SHOULD MOVED NORTHWESTWARD FOR THE NEXT 72
HR...STEERED BY THE SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC
TOWARD A WEAKNESS IN THE RIDGE OVER THE SOUTHEASTERN UNITED STATES. 
THIS PART OF THE NEW FORECAST TRACK IS SHIFTED A LITTLE TO THE LEFT
OF THE PREVIOUS TRACK BASED ON THE INITIAL POSITION...AND LIES NEAR
THE CONSENSUS MODELS.  AFTER 72 HR...THE SPREAD OF THE TRACK
GUIDANCE INCREASES DUE TO MODEL DISAGREEMENT ON THE EVOLUTION OF A
TROUGH OVER THE EASTERN UNITED STATES.  THE ECMWF KEEPS MORE RIDGE
BETWEEN ISAAC AND THE TROUGH...WHICH RESULTS IN A NORTHWESTWARD
MOTION THROUGH DAY 5.  THE GFS HAS A STRONGER TROUGH...WHICH
RESULTS IN A MORE NORTHWARD MOTION.  THE GUIDANCE ENVELOPE HAS
SHIFTED A LITTLE EASTWARD AFTER 72 HR...AND THUS THE LATTER PORTION
OF THE NEW FORECAST TRACK IS ALSO ADJUSTED EASTWARD.

WHILE THE ORGANIZATION HAS IMPROVED...THE STRUCTURE OF ISAAC STILL
DOES NOT FAVOR RAPID INTENSIFICATION DESPITE A VERY FAVORABLE
UPPER-LEVEL WIND PATTERN.  THE EARLY PART OF THE INTENSITY FORECAST
SHOWS A LITTLE MORE STRENGTHENING THAN EARLIER...AND IT IS POSSIBLE
THAT ISAAC COULD BE NEAR HURRICANE STRENGTH WHEN IT REACHES
HISPANIOLA.  LAND INTERACTION WILL LIMIT THE INTENSITY FROM 24-48
HR...AND THIS PART OF THE FORECAST MAY NEED SOME ADJUSTMENT AFTER
IT IS SEEN WHAT STRUCTURE ISAAC HAS AFTER CROSSING HISPANIOLA. 
ISAAC SHOULD STRENGTHEN OVER THE GULF OF MEXICO...WITH THE FORECAST
SHOWING THE CYCLONE BECOMING A HURRICANE BEFORE REACHING THE
NORTHERN GULF COAST.

IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK DUE TO THE
UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/1500Z 16.3N  70.8W   50 KT  60 MPH
 12H  25/0000Z 17.4N  72.6W   55 KT  65 MPH
 24H  25/1200Z 19.2N  75.1W   55 KT  65 MPH
 36H  26/0000Z 20.9N  77.6W   50 KT  60 MPH...INLAND
 48H  26/1200Z 22.3N  79.5W   45 KT  50 MPH...INLAND
 72H  27/1200Z 25.0N  83.0W   55 KT  65 MPH...OVER WATER
 96H  28/1200Z 28.0N  85.5W   65 KT  75 MPH
120H  29/1200Z 31.0N  86.5W   70 KT  80 MPH...INLAND
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 242055
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 PM EDT FRI AUG 24 2012
 
RECONNAISSANCE AIRCRAFT DATA INDICATE THAT THE CIRCULATION OF ISAAC
HAS BECOME BETTER ORGANIZED THIS AFTERNOON...WITH A WELL-DEFINED
AND MORE CIRCULAR INNER CIRCULATION.  THE MAXIMUM 850 MB
FLIGHT-LEVEL WINDS HAVE BEEN 70 KT...THE MAXIMUM RELIABLE SFMR
SURFACE WIND ESTIMATE HAS BEEN 55 KT...AND THE MINIMUM REPORTED
PRESSURE HAS BEEN 994 MB.  BASED ON THESE DATA...THE INITIAL
INTENSITY IS INCREASED TO 55 KT.  ONE SIGN OF ONGOING ORGANIZATION
ISSUES...HOWEVER...IS THE LACK OF PERSISTENCE OF THE INNER CORE
CONVECTION...WHICH HAS WANED OVER THE PAST FEW HOURS.

ISAAC HAS MADE ITS EXPECTED TURN TOWARD THE NORTHWEST AND THE
INITIAL MOTION IS NOW 315/14.  DURING THE FIRST 48-60 HR...THE
TRACK GUIDANCE MADE AN EASTWARD SHIFT SINCE THE LAST ADVISORY. 
THIS WAS LED BY THE GFS...WHICH CHANGED TO A TRACK INTO THE
SOUTHEASTERN GULF OF MEXICO TO LANDFALL IN SOUTHEASTERN FLORIDA. 
THE ECMWF AND UKMET ARE NOW ON THE LEFT EDGE OF THE GUIDANCE...
SHOWING A TRACK ALONG THE NORTH COAST OF CUBA.  THIS PART OF
THE FORECAST TRACK IS SHIFTED EASTWARD BUT STILL LIES A LITTLE TO
THE LEFT OF THE CENTER OF THE GUIDANCE ENVELOPE AND THE CONSENSUS
MODELS.  THERE REMAINS A SPREAD IN THE MODEL GUIDANCE AFTER 48
HR.  THE GFS-BASED GUIDANCE SHOWS A NORTHEASTWARD MOTION AFTER
LANDFALL ON THE NORTHERN GULF COAST...WHILE THE UKMET AND ECMWF
SHOW A NORTHWARD MOTION.  THE LATTER PART OF THE FORECAST TRACK IS
SHIFTED EASTWARD CLOSE TO THE CONSENSUS MODELS.
 
THE MAIN CONVECTIVE BAND AND STRONGEST WINDS NORTHEAST OF THE CENTER
ARE MOVING INLAND AT THIS TIME.  BASED ON THIS AND THE CURRENT LACK
OF CONVECTION NEAR THE CENTER...LITTLE CHANGE IN STRENGTH IS
EXPECTED BEFORE LANDFALL.  THE INTENSITY FROM 12-48 HR WILL BE
DETERMINED BY THE AMOUNT OF LAND INTERACTION.  THE CURRENT FORECAST
IS BASED ON THE PREMISE THAT ISAAC WILL REMAIN OVER LAND LONG
ENOUGH TO ALLOW GRADUAL WEAKENING.  HOWEVER...ANY CHANGE IN THE
TRACK THAT ALLOWS IT TO REMAIN OVER WATER FOR A LONGER TIME COULD
ALLOW IT TO BE STRONGER THAN FORECAST.  AFTER 48 HR...THE
ENVIRONMENTAL CONDITIONS APPEAR GENERALLY FAVORABLE FOR ISAAC TO
STRENGTHEN INTO A HURRICANE OVER THE GULF OF MEXICO...AND THE
INTENSITY FORECAST REFLECTS THIS.  CONVERSELY...A LONGER TRACK OVER
LAND MAY DISRUPT ISAAC ENOUGH TO BE UNABLE TO TAKE ADVANTAGE OF
THESE FAVORABLE CONDITIONS.
 
IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK DUE TO THE
UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.  THE TROPICAL
STORM WATCH FOR SOUTH FLORIDA AND THE FLORIDA KEYS MAY HAVE TO BE
UPGRADED TO A HURRICANE WATCH IF THE INTENSITY FORECAST IS REVISED
UPWARD.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/2100Z 17.2N  71.9W   55 KT  65 MPH
 12H  25/0600Z 18.7N  73.6W   50 KT  60 MPH
 24H  25/1800Z 20.7N  76.2W   50 KT  60 MPH...INLAND
 36H  26/0600Z 22.4N  78.6W   45 KT  50 MPH...NEAR COAST OF CUBA
 48H  26/1800Z 23.9N  80.7W   55 KT  65 MPH...OVER WATER
 72H  27/1800Z 26.5N  84.0W   65 KT  75 MPH
 96H  28/1800Z 29.5N  86.0W   75 KT  85 MPH
120H  29/1800Z 32.0N  86.0W   45 KT  50 MPH...INLAND
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 250319
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 PM EDT FRI AUG 24 2012
 
SATELLITE IMAGERY AND RECONNAISSANCE AIRCRAFT DATA INDICATE THAT THE
CIRCULATION AND CONVECTIVE ORGANIZATION OF ISAAC HAS CONTINUED TO
IMPROVE SINCE THE PREVIOUS ADVISORY. INFRARED AND MICROWAVE
SATELLITE IMAGERY SUGGEST THAT AN EYE IS FORMING...AND THIS IS THE
BASIS FOR INCREASING THE INTENSITY TO 60 KT. 
 
THE INITIAL MOTION ESTIMATE IS 315/12 BASED ON RECON AND MICROWAVE
FIXES. ALTHOUGH THE TRACK FORCAST WAS ADJUSTED SLIGHTLY TO THE
RIGHT THROUGH 48 HOURS...NO OTHER SIGNIFICANT CHANGES WERE MADE TO
THE PREVIOUS ADVISORY TRACK. RECENT UPPER-AIR DATA AND NOAA G-IV
AIRCRAFT DROPSONDE DATA INDICATE THE TROUGH THAT HAS CREATED THE
BREAK IN THE SUBTROPICAL RIDGE ACROSS FLORIDA HAS SHIFTED TO A
POSITION JUST EAST OF THE FLORIDA PENINSULA. THE 18Z GFS MODEL...
WHICH SHIFTED TO THE RIGHT OF ITS 12Z TRACK...CAPTURED THIS FARTHER
EAST POSITION...WHEREAS THE 18Z UKMET AND 12Z ECMWF KEPT THE TROUGH
ACROSS THE WESTERN FLORIDA PENINSULA VALID AT 00Z THIS EVENING.
BASED ON THE GFS VERIFYING BETTER THAN THE OTHER MODELS AT 00Z THIS
EVENING...THE NHC TRACK HAS BEEN SHIFTED A LITTLE TO THE RIGHT.
AFTER 48 HOURS...THE RIDGE IS EXPECTED TO BUILD BACK WESTWARD
ACROSS FLORIDA AND KEEPING ISAAC ON A MOSTLY NORTHWESTWARD HEADING
ACROSS THE EASTERN AND NORTH-CENTRAL GULF MEXICO. THE OFFICIAL
FORECAST TRACK IS CLOSE TO THE CONSENSUS MODELS TVCA AND TV15
THROUGH 48 HOURS...AND THEN IS A LITTLE TO THE RIGHT OF THOSE
MODELS AFTER THAT.

WITH THE INNER CORE CONVECTION IMPROVING...THERE IS STILL THE
POSSIBILITY THAT ISAAC COULD REACH HURRICANE INTENSITY BEFORE
REACHING HAITI TONIGHT. THE INTENSITY FROM 12-24 HOURS WILL BE
DETERMINED BY THE AMOUNT OF LAND INTERACTION WITH HAITI AND EASTERN
CUBA. AFTER THAT...THE SLIGHT EASTWARD SHIFT IN THE FORECAST TRACK
IS ENOUGH TO PLACE ISAAC OVER WATER LONGER THAN WHAT WAS INDICATED
IN THE PREVIOUS INTENSITY FORECAST REQUIRED AN INCREASE IN THE
INTENSITY FORECAST. THE EASTWARD TRACK SHIFT AND A LARGER INITIAL
AND FORECAST WIND FIELD TO THE NORTH ARE WHAT NECESSITATED THE
CHANGES IN THE WATCHES AND WARNINGS FOR FLORIDA.
 
IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK DUE TO THE
UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
AREA OF TROPICAL-STORM-FORCE WINDS ASSOCIATED WITH IT.  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/0300Z 17.7N  72.5W   60 KT  70 MPH
 12H  25/1200Z 19.4N  74.1W   50 KT  60 MPH
 24H  26/0000Z 21.7N  76.7W   50 KT  60 MPH
 36H  26/1200Z 23.4N  79.4W   55 KT  65 MPH
 48H  27/0000Z 24.9N  81.6W   60 KT  70 MPH
 72H  28/0000Z 27.1N  84.6W   70 KT  80 MPH
 96H  29/0000Z 30.0N  86.5W   80 KT  90 MPH
120H  30/0000Z 32.5N  86.5W   40 KT  45 MPH...INLAND
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 250859
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 AM EDT SAT AUG 25 2012
 
THE CIRCULATION OF ISAAC HAS REMAINED RELATIVELY INTACT AFTER MOVING
ACROSS THE SOUTHWESTERN PENINSULA OF HAITI OVERNIGHT. BEFORE THE
CENTER MOVED INLAND...HURRICANE HUNTER AIRCRAFT DATA SUGGESTED THAT
THE CYCLONE HAD PEAK WINDS OF ABOUT 55 KT. ASSUMING THE CYCLONE
WEAKENED A LITTLE AFTER ENCOUNTERING THE HIGH TERRAIN...THE INITIAL
INTENSITY IS LOWERED TO 50 KT FOR THIS ADVISORY.
 
THE INITIAL MOTION ESTIMATE IS 320/12. AS A MID-LEVEL TROUGH LIFTS
OUT OF THE SOUTHEASTERN UNITED STATES...ISAAC WILL MOVE GENERALLY
WEST-NORTHWESTWARD AROUND THE WEST SIDE OF THE SUBTROPICAL RIDGE
FOR THE NEXT THREE DAYS OR SO...AND THEN TURN NORTHWARD LATE IN THE
PERIOD AS A SHORTWAVE TROUGH AMPLIFIES OVER THE EASTERN UNITED
STATES. THERE HAS BEEN LITTLE CHANGE TO THE NHC FORECAST THIS
CYCLE...AND THE NEW TRACK FORECAST IS CLOSE TO THE MIDDLE OF THE
GUIDANCE ENVELOPE AND LIES CLOSE TO THE GFS AND THE TVCA
MULTI-MODEL CONSENSUS THROUGH 96 HOURS. BY DAY 5 THERE IS SOME
DISAGREEMENT AS TO WHETHER ISAAC WILL TURN NORTHEASTWARD AHEAD OF
THE SHORTWAVE TROUGH AS SHOWN BY THE GFS...UKMET...AND THE GFDL OR
BE LEFT BEHIND AS SHOWN BY THE ECMWF AND HWRF. THE NHC DAY 5 POINT
IS BETWEEN THE TWO CAMPS SHOWING A SLOW NORTHWARD MOTION.
 
GIVEN THAT THE CYCLONE HAS FARED RATHER WELL AFTER MOVING ACROSS
HAITI...AND THAT THE TRACK FORECAST HAS ONLY MINIMAL INTERACTION
WITH CUBA...THE INTENSITY FORECAST AFTER 12 HOURS HAS BEEN ADJUSTED
UPWARD FOLLOWING THE TREND OF THE LATEST INTENSITY GUIDANCE. ISAAC
IS EXPECTED TO BECOME A HURRICANE IN ABOUT 36 HOURS...WITH
ADDITIONAL INTENSIFICATION EXPECTED AS THE CYCLONE MOVES INTO THE
EASTERN GULF OF MEXICO IN A FAVORABLE ENVIRONMENT. THE NEW NHC
INTENSITY FORECAST IS CLOSE TO THE INTENSITY CONSENSUS AIDS THROUGH
72 HOURS AND FOLLOWS A BLEND OF THE DECAY SHIPS AND LGEM AFTERWARD.
 
THE NEW NHC FORECAST NECESSITATES THE ISSUANCE OF A HURRICANE
WARNING FOR THE FLORIDA KEYS AND A PORTION OF THE SOUTHWEST COAST
OF FLORIDA AT THIS TIME.
 
IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK OF ISAAC DUE TO THE
UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/0900Z 19.0N  73.3W   50 KT  60 MPH
 12H  25/1800Z 20.4N  75.0W   50 KT  60 MPH...INLAND
 24H  26/0600Z 22.2N  77.6W   55 KT  65 MPH...OVER WATER
 36H  26/1800Z 23.8N  80.0W   65 KT  75 MPH
 48H  27/0600Z 25.0N  81.8W   70 KT  80 MPH
 72H  28/0600Z 27.7N  84.9W   80 KT  90 MPH
 96H  29/0600Z 30.5N  86.0W   70 KT  80 MPH...INLAND
120H  30/0600Z 32.5N  86.0W   35 KT  40 MPH...INLAND
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 251502
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 AM EDT SAT AUG 25 2012

ISAAC HAS BEEN SOMEWHAT DISRUPTED BY ITS PASSAGE ACROSS HAITI.  THE
LAST REPORT FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
SHOWED THAT THE CENTER PRESSURE HAD RISEN TO 998 MB...AND THAT THE
STRONGEST FLIGHT-LEVEL WINDS WERE 60-70 N MI FROM THE CENTER.  THESE
WINDS SUPPORT AN INITIAL INTENSITY OF 50 KT.  THE CONVECTIVE
PATTERN IS DISORGANIZED...WITH LARGE CONVECTIVE BANDS SOUTH OF
HISPANIOLA AND LITTLE CONVECTION CURRENTLY NEAR THE CENTER.  IT
SHOULD BE NOTED THAT ISAAC IS AT THE EASTERN END OF A LARGE AND
ELONGATED LOW PRESSURE SYSTEM OVER THE NORTHWESTERN CARIBBEAN
SEA...WHICH IS CREATING A LARGE AREA OF STRONG EASTERLY LOW-LEVEL
WINDS WELL TO THE NORTHWEST OF THE CENTER.

THE LOW-LEVEL CENTER HAS JOGGED WESTWARD DURING THE PAST FEW
HOURS...AND THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 315/15.  IN
THE SHORT-TERM...A MID/UPPER-LEVEL TROUGH OVER THE EASTERN UNITED
STATES IS LIFTING OUT TO THE NORTHEAST AS A UPPER-LEVEL LOW MOVES
SOUTHWARD ACROSS THE CENTRAL GULF OF MEXICO.  THIS EVOLUTION...
COMBINED WITH THE LOW-LEVEL RIDGE NORTH OF ISAAC...SHOULD STEER THE
CYCLONE GENERALLY NORTHWESTWARD NEAR THE NORTH COAST OF CUBA AND THE
FLORIDA KEYS DURING THE NEXT 48 HR AS INDICATED BY THE TIGHTLY-
CLUSTERED MODEL GUIDANCE.  AFTER THAT...THE CYCLONE IS EXPECTED TO
MOVE AROUND THE WESTERN END OF THE SUBTROPICAL RIDGE AND TURN MORE
NORTHWARD OVER THE EASTERN GULF OF MEXICO.  WHILE THE GUIDANCE
GENERALLY AGREES WITH THIS SCENARIO...THERE IS A SPREAD IN
POTENTIAL LANDFALL LOCATIONS BETWEEN THE EASTERN FLORIDA PANHANDLE
AND SOUTHEASTERN LOUISIANA...WHICH LOWERS CONFIDENCE IN THE FINAL
LANDFALL POINT.  THE NEW FORECAST TRACK FOLLOWS THE CENTER OF THE
GUIDANCE ENVELOPE AND THE CONSENSUS MODELS IN CALLING FOR LANDFALL
IN THE WESTERN FLORIDA PANHANDLE BETWEEN 72-96 HR.

LITTLE CHANGE IN STRENGTH IS EXPECTED TODAY DUE TO A COMBINATION OF
LAND INTERACTION...SOME WESTERLY SHEAR...AND THE CURRENT LACK OF
CONVECTION.  THE SHEAR IS FORECAST TO DECREASE AS THE CENTER MOVES
AWAY FROM LAND...WOULD SHOULD ALLOW FOR STRENGTHENING AFTER 12 HR. 
THE NEW INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS FORECAST
THROUGH 48 HR...THEN CALLS FOR A LITTLE MORE STRENGTHENING THAN THE
PREVIOUS FORECAST OVER THE NORTHERN GULF.  THE CYCLONE SHOULD
WEAKEN TO A DEPRESSION AFTER LANDFALL ON THE NORTHERN GULF COAST.
  
THE NEW NHC FORECAST NECESSITATES THE ISSUANCE OF ADDITIONAL
TROPICAL STORM WARNINGS AND WATCHES FOR PORTIONS OF THE FLORIDA
PENINSULA.
 
IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK OF ISAAC DUE TO THE
UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/1500Z 20.1N  74.6W   50 KT  60 MPH
 12H  26/0000Z 21.7N  76.4W   50 KT  60 MPH
 24H  26/1200Z 23.3N  79.0W   55 KT  65 MPH
 36H  27/0000Z 24.7N  81.3W   65 KT  75 MPH
 48H  27/1200Z 25.9N  83.1W   75 KT  85 MPH
 72H  28/1200Z 28.5N  85.5W   85 KT 100 MPH
 96H  29/1200Z 31.5N  86.5W   65 KT  75 MPH...INLAND
120H  30/1200Z 33.0N  86.0W   30 KT  35 MPH...INLAND
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 252102
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 PM EDT SAT AUG 25 2012

THE CENTER OF ISAAC IS CURRENTLY MOVING ALONG THE NORTH COAST OF
EASTERN CUBA.  THE SATELLITE APPEARANCE IS SOMEWHAT DISORGANIZED...
WITH THE MAIN CONVECTIVE MASS 50 N MI OR MORE EAST OF THE LOW-LEVEL
CENTER.  AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS
REPORTED 850 MB FLIGHT-LEVEL WINDS OF 56 KT TO THE NORTHEAST OF THE
CENTER...WITH RELIABLE-LOOKING SFMR SURFACE WIND DATA NEAR 50 KT. 
BASED ON THIS...THE INITIAL INTENSITY REMAINS 50 KT.  THE CENTRAL
PRESSURE OF 997 MB IS BASED ON A COMBINATION OF AIRCRAFT DATA AND
CUBAN SURFACE OBSERVATIONS.

THE INITIAL MOTION IS NOW 310/18.  ISAAC IS CURRENTLY PART OF A
LARGE LOW/MID-LEVEL LOW PRESSURE SYSTEM COVERING THE NORTHWESTERN
CARIBBEAN SEA AND THE ADJACENT LAND AND OCEAN AREAS.  THIS LOW
PRESSURE AREA HAS A SECOND VORTICITY CENTER BETWEEN JAMAICA AND THE
CAYMAN ISLANDS...AND FOR THE NEXT 24-36 HR ISAAC AND THIS CENTER
WILL LIKELY ROTATE AROUND EACH OTHER.  BASED ON THIS EXPECTATION...
THE FORECAST TRACK SHOWS ISAAC MOVING NORTHWESTWARD FOR 12 HR OR
SO...FOLLOWED BY A TURN TOWARD THE WEST-NORTHWEST.  IT IS POSSIBLE
THE STORM COULD MAKE A SHARPER TURN THAN FORECAST...AS THE UKMET IS
SHOWING AN ALMOST DUE WEST MOTION BETWEEN THE FLORIDA KEYS AND CUBA
NEAR THE 36 HR POINT.  THE EARLY PART OF THE FORECAST TRACK IS
SHIFTED A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST...BUT STILL
LIES TO THE RIGHT OF THE CONSENSUS MODELS AND THE BULK OF THE
DYNAMICAL MODELS.  AFTER 36 HR...ISAAC SHOULD BREAK FREE OF OR
ABSORB THE REST OF THE LOW...WITH THE SUBTROPICAL RIDGE TO THE EAST
BECOMING THE DOMINANT STEERING INFLUENCE.  THIS SHOULD ALLOW THE
STORM TO GRADUALLY TURN TOWARD THE NORTHWEST AND NORTH OVER THE
EASTERN AND NORTHERN GULF OF MEXICO...WITH AN EVENTUAL LANDFALL
ALONG THE NORTHERN GULF COAST IN 72-96 HR.  WHERE THIS MIGHT OCCUR
IS STILL RATHER UNCERTAIN...WITH THE TRACK GUIDANCE SPREAD BETWEEN
SOUTHEASTERN LOUISIANA AND THE CENTRAL FLORIDA PANHANDLE.  THIS PART
OF THE TRACK FORECAST LIES IN THE CENTER OF THE GUIDANCE ENVELOPE
NEAR THE CONSENSUS MODELS AND IS SIMILAR TO THE PREVIOUS FORECAST.

A COMBINATION OF LIGHT WESTERLY VERTICAL WIND SHEAR AND LAND
INTERACTION SHOULD AT LEAST SLOW INTENSIFICATION FOR THE NEXT 12
HR.  AFTER THAT...THE SHEAR SHOULD DIMINISH WHILE THE CYCLONE
REACHES OPEN WATER.  THIS SHOULD ALLOW ISAAC TO GRADUALLY STRENGTHEN
INTO A HURRICANE NEAR THE FLORIDA KEYS OR OVER THE SOUTHEASTERN
GULF OF MEXICO.  THE NEW INTENSITY FORECAST IS SIMILAR TO THE
PREVIOUS FORECAST AND IS NEAR OR A LITTLE ABOVE THE INTENSITY
CONSENSUS.  IT SHOULD BE NOTED THAT THE GLOBAL MODELS ARE
FORECASTING A VERY FAVORABLE PATTERN OF UPPER-LEVEL WINDS OVER THE
NORTHERN GULF OF MEXICO BY 72 HR.  SHOULD THIS VERIFY AND SHOULD
ISAAC ESTABLISH AN INNER CORE...THE CYCLONE COULD BE SIGNIFICANTLY
STRONGER THAN CURRENTLY FORECAST.
 
IT IS IMPORTANT NOT TO FOCUS ON THE EXACT TRACK OF ISAAC DUE TO THE
UNCERTAINTIES IN THE FORECAST AND THE FACT THAT ISAAC HAS A LARGE
AREA OF TROPICAL STORM FORCE WINDS ASSOCIATED WITH IT.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  25/2100Z 21.3N  76.0W   50 KT  60 MPH
 12H  26/0600Z 22.6N  78.0W   55 KT  65 MPH
 24H  26/1800Z 24.1N  80.6W   60 KT  70 MPH
 36H  27/0600Z 25.2N  82.7W   65 KT  75 MPH
 48H  27/1800Z 26.5N  84.3W   75 KT  85 MPH
 72H  28/1800Z 29.0N  86.0W   85 KT 100 MPH
 96H  29/1800Z 31.5N  86.0W   55 KT  65 MPH...INLAND
120H  30/1800Z 33.5N  85.5W   25 KT  30 MPH...INLAND
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 260244
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 PM EDT SAT AUG 25 2012
 
SATELLITE AND RADAR DATA FROM CUBA SHOW THAT ISAAC IS MOVING
PARALLEL TO...BUT OFFSHORE OF...THE NORTHERN COAST OF CUBA.
THE HURRICANE HUNTER AIRCRAFT DID NOT FIND ANY STRONGER WINDS
DURING THE LATTER PORTION OF THE FLIGHT AND THE INITIAL WIND
SPEED REMAINS 50 KT.  HOWEVER...THUNDERSTORM ACTIVITY HAS
INCREASED IN A BAND TO THE NORTH AND EAST OF THE CENTER DURING
THE PAST FEW HOURS AND ISAAC MAY BE ON THE VERGE OF STRENGTHENING.
THE NEXT RECONNAISSANCE FLIGHT IS EXPECTED TO BE IN THE CYCLONE
AROUND 0600 UTC.
 
THE INITIAL MOTION ESTIMATE IS 305/15 KT.  ISAAC SHOULD CONTINUE ON
A WEST-NORTHWESTWARD TO NORTHWESTWARD MOTION DURING THE NEXT 24
HOURS OR SO BETWEEN A LARGE LOW/MID-LEVEL LOW PRESSURE SYSTEM OVER
THE NORTHWESTERN CARIBBEAN SEA AND A MID-LEVEL RIDGE OVER THE
WESTERN ATLANTIC.  THE MODEL GUIDANCE IS TIGHTLY CLUSTERED DURING
THIS TIME AND SHOWS A TRACK OVER THE STRAITS OF FLORIDA AND NEAR OR
OVER THE FLORIDA KEYS.  IN ABOUT 48 HOURS...ISAAC WILL BE NEARING
THE WESTERN PORTION OF THE RIDGE AND SHOULD MOVE IN A GENERAL
NORTHWESTWARD HEADING OVER THE EASTERN GULF OF MEXICO...BUT LARGE
DIFFERENCES EXIST BETWEEN THE LATEST ECMWF AND GFS MODELS AFTER
THAT TIME.  THE ECMWF RECURVES ISAAC AHEAD OF A MID-LATITUDE
TROUGH OVER THE EASTERN UNITED STATES...WHILE THE GFS SLOWS ISAAC
DOWN AS THE TROUGH BYPASSES THE SYSTEM AND THE MODEL THEN TURNS
THE CYCLONE WESTWARD TO THE SOUTH OF A DEVELOPING MID- TO
UPPER-LEVEL RIDGE.  THIS BIFURCATION IS ALSO SEEN IN THE MOST RECENT
ECMWF AND GFS ENSEMBLES WITH ABOUT AN EQUAL NUMBER OF MEMBERS
SHOWING RECURVATURE VERSUS A CONTINUE NORTHWESTERLY TRACK TOWARD
THE NORTHERN GULF COAST.  SINCE THE UNCERTAINTY IS LARGE AND EITHER
OF THESE SCENARIOS ARE POSSIBLE AT THIS TIME...THE NHC FORECAST IS
LIES BETWEEN THEM.  THE UPDATED TRACK IS VERY CLOSE TO THE PREVIOUS
ADVISORY THROUGH 36 HOURS.  AFTER THAT TIME...THE TRACK HAS BEEN
ADJUSTED WESTWARD...BUT IT REMAINS EAST OF THE DYNAMICAL MODEL
CONSENSUS TO RETAIN SOME CONTINUITY WITH THE PREVIOUS FORECAST.

THE UPPER-LEVEL ENVIRONMENT IS EXPECTED TO BECOME MORE CONDUCIVE FOR
STRENGTHENING DURING THE NEXT COUPLE OF DAYS AS ISAAC MOVES OVER
THE WARM WATERS OF THE FLORIDA STRAITS AND EASTERN GULF.  STEADY
STRENGTHENING IS EXPECTED AND ISAAC IS EXPECTED TO BE AT OR NEAR
HURRICANE STRENGTH WHEN THE CENTER REACHES THE FLORIDA KEYS.
ADDITIONAL STRENGTHENING IS LIKELY WHILE THE CYCLONE MOVES OVER THE
EASTERN GULF OF MEXICO.  THE NEW INTENSITY FORECAST IS A LITTLE
HIGHER THAN THE PREVIOUS ADVISORY AND IS BETWEEN THE SHIPS/LGEM
GUIDANCE AND THE MORE AGGRESSIVE HWRF MODEL.
 
IT IS IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK SINCE
SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER.  SINCE LARGE
UNCERTAINTIES REMAIN IN THE EXTENDED PORTION OF THE FORECAST...IT
IS TOO EARLY TO DETERMINE EXACTLY WHERE AND WHEN ISAAC WILL MAKE
LANDFALL ALONG THE GULF COAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/0300Z 22.1N  77.2W   50 KT  60 MPH
 12H  26/1200Z 23.4N  79.4W   55 KT  65 MPH
 24H  27/0000Z 24.6N  81.8W   65 KT  75 MPH...NEAR FLORIDA KEYS
 36H  27/1200Z 25.8N  83.7W   75 KT  85 MPH
 48H  28/0000Z 27.2N  85.2W   85 KT 100 MPH
 72H  29/0000Z 29.5N  86.5W   90 KT 105 MPH
 96H  30/0000Z 31.5N  86.5W   50 KT  60 MPH...INLAND
120H  31/0000Z 34.0N  86.0W   25 KT  30 MPH...INLAND
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 260900
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  21
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 AM EDT SUN AUG 26 2012
 
WHILE THE SATELLITE PRESENTATION OF ISAAC REMAINS SOMEWHAT
UNIMPRESSIVE...WITH DEEP CONVECTION LIMITED TO A RATHER SMALL AREA
NORTH AND EAST OF THE CENTER...AIRCRAFT DATA SUGGEST THAT THE
CYCLONE HAS STRENGTHENED A LITTLE OVERNIGHT. PEAK 850-MB
FLIGHT-LEVEL WINDS OF 69 KT IN THE NORTHEAST QUADRANT ADJUST TO AN
INTENSITY OF 55 KT...WHICH IS THE VALUE FOR THIS ADVISORY. AIRCRAFT
DATA INDICATE THAT THE MINIMUM PRESSURE HAS ALSO DROPPED A LITTLE...
TO 995 MB. ISAAC STILL APPEARS TO BE BATTLING THE EFFECTS OF SOME
LOW- TO MID-LEVEL DRY AIR IN THE WESTERN SIDE OF THE CIRCULATION...
AS SEEN IN UPPER-AIR DATA FROM MIAMI AND KEY WEST. ASIDE FROM
THIS...HOWEVER...CONDITIONS APPEAR FAVORABLE FOR STEADY
INTENSIFICATION AS THE CYCLONE MOVE ACROSS THE FLORIDA STRAITS AND
INTO THE EASTERN GULF OF MEXICO. WATERS ALONG THE FORECAST TRACK ARE 
VERY WARM...AND UPPER-LEVEL WINDS ARE FORECAST BY THE GLOBAL MODELS
TO BECOME CONDUCIVE FOR STRENGTHENING. THE NEW NHC FORECAST IS
SIMILAR TO THE PREVIOUS ONE...BUT SHOWS A LITTLE SLOWER RATE OF
STRENGTHENING FOR THE FIRST COUPLE OF DAYS...TRENDING TOWARD THE
LATEST CYCLE OF GUIDANCE.
 
THE INITIAL MOTION ESTIMATE IS 305/16...A LITTLE FASTER THAN BEFORE.
AS THE UPPER-LOW TO THE WEST OF ISAAC RETREATS WESTWARD AND THE
CLOSED LOW OVER THE MID-ATLANTIC STATES LIFTS NORTHWARD...ISAAC
WILL MOVE GENERALLY WEST-NORTHWESTWARD OR NORTHWESTWARD AROUND THE
WESTERN PERIPHERY OF THE ATLANTIC SUBTROPICAL RIDGE FOR THE NEXT 48
HOURS. BEYOND THAT TIME...THERE IS CONSIDERABLE SPREAD IN THE MODEL
GUIDANCE. MOST OF THE MODELS...WITH THE EXCEPTION OF THE UKMET...NO
LONGER SHOW ISAAC RECURVING AHEAD OF A SHORTWAVE TROUGH MOVING
EASTWARD ACROSS THE EASTERN UNITED STATES. ONE CAMP OF GUIDANCE...
INCLUDING THE GFS...HWRF...AND GFS ENSEMBLE MEAN SHOW A
NORTHWESTWARD TRACK TOWARD THE CENTRAL GULF COAST AS THE SHORTWAVE
BYPASSES ISAAC COMPLETELY. THE ECMWF AND GFDL SHOW HAVE MORE OF A
WEAKNESS IN THE RIDGE AND SHOW ISAAC TURNING NORTHWARD TOWARD THE
EASTERN GULF COAST. THE NEW NHC FORECAST IS FASTER THAN THE
PREVIOUS ONE THROUGH MUCH OF THE PERIOD...BUT IS ALONG THE PREVIOUS
TRACK THROUGH 36 HOURS. AFTER THAT TIME...A SIGNIFICANT WESTWARD
ADJUSTMENT WAS MADE...AND THE NEW NHC TRACK IS CLOSE TO THE TVCA
MULTI-MODEL CONSENSUS AND THE ECMWF...SHOWING A NORTH-NORTHWESTWARD
AND NORTHWARD TURN AT DAYS 3 THROUGH 5. GIVEN THE LARGE SPREAD IN
THE GUIDANCE...CONFIDENCE IN THE LONG-RANGE TRACK FORECAST IS QUITE
LOW...AND IT IS TOO EARLY TO DETERMINE EXACTLY WHERE AND WHEN ISAAC
WILL MAKE LANDFALL ALONG THE GULF COAST. FURTHER ADJUSTMENTS TO THE
TRACK MAY BE NECESSARY LATER TODAY.
 
THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT
FORECAST TRACK SINCE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE
CENTER.
 
GIVEN THE NEW NHC FORECAST...A HURRICANE WATCH HAS BEEN ISSUED FOR A
PORTION OF THE NORTHERN GULF COAST.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/0900Z 23.1N  79.0W   55 KT  65 MPH
 12H  26/1800Z 24.2N  80.8W   60 KT  70 MPH
 24H  27/0600Z 25.5N  83.1W   65 KT  75 MPH
 36H  27/1800Z 26.9N  84.9W   70 KT  80 MPH
 48H  28/0600Z 28.1N  86.5W   80 KT  90 MPH
 72H  29/0600Z 30.2N  88.0W   90 KT 105 MPH
 96H  30/0600Z 32.0N  88.5W   40 KT  45 MPH...INLAND
120H  31/0600Z 34.0N  88.5W   25 KT  30 MPH...INLAND
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 261459
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 AM EDT SUN AUG 26 2012

VISIBLE SATELLITE AND IMAGERY SUGGEST THAT THE TROPICAL CYCLONE IS
GRADUALLY BECOMING BETTER ORGANIZED.  THERE ARE INDICATIONS OF
INNER CORE DEVELOPMENT WITH INCREASED CONVECTION NEAR AND OVER THE
CENTER...AND A PARTIAL EYEWALL IS IN EVIDENCE ON RADAR IMAGERY.  THE
BANDING FEATURES HAVE BECOME MORE DISTINCT OVER THE NORTHERN AND
EASTERN SEMICIRCLES OF THE CIRCULATION.  THE CURRENT INTENSITY
ESTIMATE IS HELD AT 55 KT PENDING OBSERVATIONS FROM AN AIR FORCE
HURRICANE HUNTER AIRCRAFT THAT SHOULD BE IN THE CENTER SHORTLY. 
ISAAC CONTINUES TO EXHIBIT A WELL-DEFINED UPPER-LEVEL OUTFLOW
PATTERN...AND GRADUAL STRENGTHENING IS LIKELY AS THE CYCLONE
TRAVERSES THE EASTERN GULF OF MEXICO OVER THE NEXT COUPLE OF DAYS. 
THE OFFICIAL WIND SPEED FORECAST IS SIMILAR TO THE PREVIOUS NHC
FORECAST AND IS ALSO CLOSE TO THE LATEST STATISTICAL-DYNAMICAL
GUIDANCE.

THE TRACK FORECAST BEYOND DAY 2 HAS BECOME PROBLEMATIC.  DYNAMICAL
MODELS DEPICT THE CYCLONE MOVING INTO A BREAK IN THE SUBTROPICAL
RIDGE NORTH OF THE GULF COAST IN ABOUT 72 HOURS.  HOWEVER THERE IS
A LARGE SPREAD AMONG THE MORE RELIABLE TRACK MODELS.  FOR EXAMPLE...
THE ECMWF FORECAST IS ABOUT 300 N MI EAST OF THE GFS SOLUTION AT DAY
3.  SINCE THE DYNAMICAL MODEL CONSENSUS HAS SHIFTED WESTWARD...THE
OFFICIAL TRACK FORECAST IS MOVED A BIT TO THE WEST OF THE PREVIOUS
ONE.  THIS REQUIRES AN EXTENSION OF THE HURRICANE WATCH WESTWARD
ALONG THE LOUISIANA COAST.  IT SHOULD BE NOTED THAT THERE IS
GREATER THAN USUAL UNCERTAINTY IN THE TRACK FORECAST.
 
THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT
FORECAST TRACK SINCE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE
CENTER.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/1500Z 23.9N  80.8W   55 KT  65 MPH
 12H  27/0000Z 25.0N  82.7W   65 KT  75 MPH
 24H  27/1200Z 26.1N  84.8W   70 KT  80 MPH
 36H  28/0000Z 27.4N  86.4W   75 KT  85 MPH
 48H  28/1200Z 28.5N  87.6W   80 KT  90 MPH
 72H  29/1200Z 30.5N  89.0W   90 KT 105 MPH
 96H  30/1200Z 32.5N  89.5W   30 KT  35 MPH...INLAND
120H  31/1200Z 34.5N  89.5W   20 KT  25 MPH...INLAND
 
$$
FORECASTER PASCH/ROBERTS
 

WTNT44 KNHC 262102
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 PM EDT SUN AUG 26 2012

ALTHOUGH SATELLITE AND RADAR IMAGES HAVE SUGGESTED THAT THE TROPICAL
CYCLONE WAS BECOMING A LITTLE BETTER ORGANIZED...AN AIR FORCE
HURRICANE HUNTER AIRCRAFT INVESTIGATING ISAAC THIS AFTERNOON HAVE
FOUND THAT THERE HAS BEEN NO STRENGTHENING OF THE STORM. 
FLIGHT-LEVEL AND SFMR-OBSERVED WINDS SUPPORT AN INTENSITY OF 50 KT. 
THERE IS STILL A WELL-ESTABLISHED UPPER-LEVEL OUTFLOW PATTERN OVER
THE SYSTEM...AND VERTICAL SHEAR SHOULD REMAIN FAIRLY LIGHT FOR THE
NEXT COUPLE OF DAYS.  INTENSIFICATION STILL SEEMS LIKELY AS ISAAC
MOVES OVER THE EASTERN GULF...AND POSSIBLY OVER THE HIGHER HEAT
CONTENT OF THE LOOP CURRENT.  THE OFFICIAL INTENSITY FOREAST IS
CLOSE TO THE LATEST LGEM GUIDANCE...AND NOT MUCH DIFFERENT FROM THE
PREVIOUS NHC FORECAST.    

ISAAC HAS MOVED A LITTLE TO THE LEFT OF PREVIOUS PROJECTIONS AND
CENTER FIXES YIELD A 6- TO 12-HOUR AVERAGED MOTION OF 295/15.   THE
TRACK FORECAST CONTINUES TO BE CHALLENGING.  THE DYNAMICAL MODELS
SHOW THE TROPICAL STORM/HURRICANE GRADUALLY TURNING TO THE RIGHT
AND HEADING FOR A BREAK IN THE SUBTROPICAL RIDGE.  HOWEVER...THERE
ARE SUBSTANTIAL DIFFERENCES AMONG THE MOST RELIABLE MODELS AS TO
WHERE ISAAC MIGHT CROSS THE NORTHERN GULF COAST.  THE U.K. MET.
OFFICE AND ECMWF MODELS ARE ABOUT 300 N MI TO THE EAST OF THE GFS
AT LANDFALL.  IT SHOULD BE NOTED THAT NEARLY ALL OF THE GFS ENSMEBLE  
MEMBERS ARE EAST OF THE GFS CONTROL TRACK.  BECAUSE OF THE WIDE
MODEL SPREAD...THERE CONTINUES TO BE GREATER THAN USUAL TRACK
FORECAST UNCERTAINTY.  
 
THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT
FORECAST TRACK DUE TO FORECAST UNCERTAINTIES AND THE FACT THAT
SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER.

THE OFFICIAL FORECAST TRACK AND WIND RADII NECESSITATE THE ISSUANCE
OF A HURRICANE WARNING FOR THE NORTHERN GULF COAST AT THIS TIME. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  26/2100Z 24.2N  82.3W   50 KT  60 MPH
 12H  27/0600Z 25.1N  83.9W   55 KT  65 MPH
 24H  27/1800Z 26.3N  85.9W   60 KT  70 MPH
 36H  28/0600Z 27.7N  87.6W   70 KT  80 MPH
 48H  28/1800Z 28.9N  88.5W   80 KT  90 MPH
 72H  29/1800Z 30.7N  89.5W   85 KT 100 MPH...INLAND
 96H  30/1800Z 32.5N  90.0W   30 KT  35 MPH...INLAND
120H  31/1800Z 34.5N  90.0W   20 KT  25 MPH...INLAND
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 270250
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  24
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1100 PM EDT SUN AUG 26 2012
 
SATELLITE IMAGERY HAS SHOWN AN INCREASE IN THE AREA OF COLD CLOUD
TOPS NEAR THE CENTER OF ISAAC.  HOWEVER...THERE HAS NOT BEEN ANY
SIGNIFICANT CHANGE IN ORGANIZATION IN RADAR DATA FROM KEY WEST
THIS EVENING. IN FACT...THE AIRCRAFT FIXES HAVE BEEN NEAR THE
SOUTHEASTERN EDGE OF THE CONVECTIVE CLUSTER SEEN IN BOTH SATELLITE
AND RADAR IMAGERY.  AN EARLIER SHIP OBSERVATION AND SFMR
MEASUREMENTS OF 50-55 KT SUPPORTED INCREASING THE INTENSITY TO 55
KT ON THE INTERMEDIATE ADVISORY.  SINCE THAT TIME...THE AIRCRAFT
HAS NOT FOUND ANY STRONGER WINDS SO THE INITIAL WIND SPEED REMAINS
UNCHANGED.  THE LARGE SCALE ENVIRONMENTAL FACTORS...WARM
WATERS...AND A CONDUCIVE UPPER-AIR PATTERN FAVOR STRENGTHENING
DURING THE NEXT COUPLE OF DAYS. HOWEVER...THE LACK OF AN INNER CORE
AND LARGE WIND FIELD COULD CONTINUE TO BE IMPEDING FACTORS FOR
SIGNIFICANT STRENGTHENING IN THE SHORT TERM.  THE NHC INTENSITY
FORECAST SHOWS A GRADUAL INCREASE IN WIND SPEED DURING THE NEXT 12
HOURS OR SO...FOLLOWED BY MORE STEADY STRENGTHENING.  THE OFFICIAL
FORECAST IS CLOSE TO THE SHIPS/LGEM GUIDANCE AND THE INTENSITY
CONSENSUS.
 
AIRCRAFT AND RADAR CENTER FIXES INDICATE THAT ISAAC JOGGED WESTWARD
AND SLOWED DOWN THIS EVENING.  HOWEVER...THE LONGER TERM MOTION IS
285/12 KT.  THE MODELS SHOW ISAAC TURNING TOWARD THE NORTHWEST INTO
A BREAK IN THE SUBTROPICAL RIDGE.  ALTHOUGH THE MODELS AGREE ON
THIS TURN...THERE IS AN UNUSUALLY LARGE SPREAD IN THE TRACK GUIDANCE
AFTER 24 HOURS.  THE SPREAD OF LANDFALL LOCATIONS ALONG THE NORTHERN
GULF COAST RANGES FROM THE TEXAS/LOUISIANA BORDER EASTWARD TO THE
ALABAMA/FLORIDA BORDER WITH THE HWRF...GFDL...AND GFS NEAR THE
WESTERN EDGE AND THE UKMET AND ECMWF ALONG THE EASTERN EDGE OF THE
ENVELOPE.  OVERALL...THE CONSENSUS HAS SHIFTED A LITTLE WESTWARD
AND THE OFFICIAL FORECAST AS BEEN MOVED IN THAT DIRECTION.  THE NHC
FORECAST IS BETWEEN THE ECMWF AND GFS ENSEMBLE MEANS AND NEAR THE
HFIP MULTI-MODEL CONSENSUS.  BECAUSE OF THE VERY LARGE SPREAD IN
THE GUIDANCE...THERE CONTINUES TO BE GREATER THAN USUAL TRACK
FORECAST UNCERTAINTY.
 
THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT
FORECAST TRACK DUE TO FORECAST UNCERTAINTIES AND THE FACT THAT
SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/0300Z 24.2N  82.9W   55 KT  65 MPH
 12H  27/1200Z 25.2N  84.8W   60 KT  70 MPH
 24H  28/0000Z 26.5N  86.7W   70 KT  80 MPH
 36H  28/1200Z 27.9N  88.3W   80 KT  90 MPH
 48H  29/0000Z 28.9N  89.3W   85 KT 100 MPH
 72H  30/0000Z 30.6N  90.3W   70 KT  80 MPH...INLAND
 96H  31/0000Z 33.0N  91.0W   30 KT  35 MPH...INLAND
120H  01/0000Z 36.0N  91.0W   20 KT  25 MPH...INLAND
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 270859
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  25
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
500 AM EDT MON AUG 27 2012
 
THE LAST AIRCRAFT FIX BEFORE 06Z SUGGESTED THAT THE CENTER OF ISAAC
HAD REFORMED A LITTLE CLOSER TO THE DEEP CONVECTION...AND THAT THE
PRESSURE HAD FALLEN TO 990 MB. HOWEVER...NO STRONGER WINDS WERE
OBSERVED BY THE AIRCRAFT...AND THE INITIAL INTENSITY IS HELD AT 55
KT FOR THIS ADVISORY. THE CONTINUED LACK OF INNER CORE STRUCTURE...
THE LARGE CIRCULATION...AND SOUTHEASTERLY SHEAR NEAR THE OUTFLOW
LAYER DUE TO AN UPPER-LEVEL LOW SOUTHWEST OF ISSAC SHOULD RESULT IN
ONLY GRADUAL STRENGTHENING FOR THE FIRST 12 HOURS OR SO. AFTER THAT
TIME...STEADIER STRENGTHENING IS EXPECTED AS THE CIRCULATION
CONSOLIDATES AND AS THE UPPER LOW MOVES AWAY FROM ISAAC. THE NEW
NHC FORECAST IS A LITTLE LOWER THAN THE PREVIOUS ONE...AND IS CLOSE
TO OR A BIT ABOVE THE INTENSITY CONSENSUS UNTIL LANDFALL IN ABOUT
48 HOURS.

RECENT AIRCRAFT FIXES SHOW THE CENTER IS NOW LOCATED CLOSER TO THE
DEEP CONVECTION. THE INITIAL MOTION ESTIMATE IS 300/12...AS ISAAC
IS SITUATED ON THE SOUTHWESTERN PERIPHERY OF THE ATLANTIC
SUBTROPICAL RIDGE. A DECREASE IN FORWARD SPEED AND A TURN TOWARD
THE NORTHWEST ARE EXPECTED IN THE NEXT DAY OR SO...AS ISAAC MOVES
INTO A BREAK IN THE RIDGE OVER THE NORTHERN GULF OF MEXICO INDUCED
BY A TROUGH MOVING THROUGH THE EASTERN UNITED STATES. THE TRACK
MODEL GUIDANCE IS PRETTY TIGHTLY CLUSTERED FOR THE FIRST 36 HOURS
OR SO...AND THROUGH THAT TIME THE NEW NHC FORECAST IS A LITTLE TO
THE RIGHT OF THE PREVIOUS ONE DUE TO THE INITIAL POSITION AND
MOTION. WHILE THE MODEL SPREAD INCREASES AT 48 HOURS AND BEYOND...
THE ECMWF AND UKMET HAVE SHIFTED WESTWARD THIS CYCLE AND NOW TAKE
ISAAC TOWARD THE MISSISSIPPI COAST. THE GFS...GFS ENSEMBLE MEAN...
GFDL...AND HWRF CONTINUE TO SHOW LESS OF A NORTHWARD TURN AND BRING
THE CYCLONE INTO SOUTHEASTERN LOUISIANA. THE NEW NHC TRACK FORECAST
HAS BEEN ADJUSTED WESTWARD BY ABOUT A DEGREE AT 72 HOURS AND BEYOND
AND LIES BETWEEN THE ECMWF AND THE GFS ENSEMBLE MEAN. BECAUSE OF
THE LARGE SPREAD IN THE GUIDANCE...THE UNCERTAINTY IN THE TRACK
FORECAST CONTINUES TO BE GREATER THAN USUAL AT 48 HOURS AND BEYOND.
 
BECAUSE OF THIS UNCERTAINTY...AND THE FACT THAT SIGNIFICANT HAZARDS
EXTEND WELL AWAY FROM THE CENTER...IT IS IMPORTANT NOT TO FOCUS ON
THE EXACT FORECAST TRACK. 
 
GIVEN THE NEW TRACK AND INTENSITY FORECAST...NEW WATCHES AND
WARNINGS HAVE BEEN ISSUED FOR PORTIONS OF THE LOUISIANA COAST. THE
INITIAL 34-KT WIND RADII HAVE BEEN EXPANDED IN THE SOUTHEAST
SEMICIRCLE GIVEN CONTINUING OBSERVATIONS OF TROPICAL STORM
CONDITIONS IN THE FLORIDA KEYS. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/0900Z 25.2N  84.2W   55 KT  65 MPH
 12H  27/1800Z 26.2N  85.9W   60 KT  70 MPH
 24H  28/0600Z 27.6N  87.8W   70 KT  80 MPH
 36H  28/1800Z 28.8N  89.1W   75 KT  85 MPH
 48H  29/0600Z 29.7N  90.1W   80 KT  90 MPH...INLAND
 72H  30/0600Z 31.2N  91.1W   50 KT  60 MPH...INLAND
 96H  31/0600Z 34.0N  92.0W   30 KT  35 MPH...INLAND
120H  01/0600Z 38.0N  91.5W   20 KT  25 MPH...INLAND
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 271458
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  26
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 AM CDT MON AUG 27 2012
 
DATA FROM THE TAMPA AND KEY WEST DOPPLER RADARS...AND FROM AIR FORCE
RESERVE AND NOAA RECONNAISSANCE AIRCRAFT DATA INDICATE THE INNER
CORE STRUCTURE AND INTENSITY OF ISAAC HAS CHANGED LITTLE SINCE THE
PREVIOUS ADVISORY. A RAGGED EYE FEATURE HAS OCCASIONALLY APPEARED
IN THESE DATA...BUT IT HAS BEEN UNABLE TO PERSIST. THE CENTRAL
PRESSURE HAS DECREASED TO AROUND 987-988 MB...BUT THIS HAS NOT
RESULTED IN ANY INCREASE IN THE WIND SPEEDS. THE PREVIOUS INTENSITY
OF 55 KT IS BEING MAINTAINED FOR THIS ADVISORY BASED ON THE RECON
WIND DATA.

THE INITIAL MOTION ESTIMATE IS 305/12. NO SIGNIFICANT CHANGE WAS
MADE TO THE PREVIOUS FORECAST TRACK. THE LATEST 12Z UPPER-AIR DATA
INDICATE 20-40 METER HEIGHT RISES AT THE 500 MB AND 400 MB LEVELS
ACROSS THE SOUTHEASTERN AND SOUTH-CENTRAL U.S....WHICH SUGGESTS
THAT THE SUBTROPICAL RIDGE TO THE NORTH OF ISAAC HAS STRENGTHENED
SLIGHTLY. THIS WOULD SUPPORT A NORTHWESTWARD TO WEST-NORTHWESTWARD
MOTION UNTIL LANDFALL IN ABOUT 36-48 HOURS...AND THIS MOTION IS
SUPPORTED BY THE NHC MODEL CONSENSUS. AFTER 48 HOURS...HOWEVER...
THE MODEL GUIDANCE IS WIDELY DIVERGENT WITH A SPREAD OF MORE THAN
500 N MI BETWEEN THE GFS ON THE LEFT AND THE ECMWF ON THE RIGHT.
THE FORECAST TRACK AT DAYS 3-5 IS ALSO SIMILAR TO THE PREVIOUS
ADVISORY AND LIES CLOSE TO THE MODEL CONSENSUS...BUT THIS IS A LOW
CONFIDENCE FORECAST AT THOSE TIME PERIODS.

THE LACK OF STRENGTHENING APPEARS TO TO BE DUE TO THE
LARGER-THAN-AVERAGE WIND RADII...WHICH HAVE YET TO CONTRACT
INWARD...ALONG WITH THE PERIODIC ENTRAINMENT OF DRY MID-LEVEL AIR
FROM THE EASTERN SEMICIRCLE INTO THE INNER-CORE REGION. UNTIL THE
DRY AIR MIXES OUT...EROSION OF THE INNER-CORE CONVECTION WILL
LIKELY CONTINUE UNTIL ISAAC APPROACHES THE NORTH-CENTRAL GULF COAST
IN ABOUT 24 HOURS. AT THAT TIME...INCREASED FRICTIONAL EFFECTS FROM
THE GULF COAST LAND MASS IS EXPECTED TO CONTRIBUTE TO AN INCREASE
IN CONVECTION IN THE NORTHEAST QUADRANT...WHICH COULD ENABLE THE
STRENGTHENING PROCESS. THE OFFICIAL INTENSITY FORECAST IS SIMILAR
TO THE PREVIOUS ADVISORY AND IS SLIGHTLY ABOVE THE INTENSITY
CONSENSUS MODEL IV15.
 
BECAUSE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER...IT IS
IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/1500Z 26.1N  85.3W   55 KT  65 MPH
 12H  28/0000Z 27.1N  86.8W   65 KT  75 MPH
 24H  28/1200Z 28.3N  88.4W   70 KT  80 MPH
 36H  29/0000Z 29.3N  89.6W   80 KT  90 MPH
 48H  29/1200Z 30.2N  90.5W   70 KT  80 MPH...INLAND
 72H  30/1200Z 31.9N  91.7W   40 KT  45 MPH...INLAND
 96H  31/1200Z 35.2N  92.3W   25 KT  30 MPH...INLAND
120H  01/1200Z 39.3N  91.3W   20 KT  25 MPH...INLAND
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 272058
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  27
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 PM CDT MON AUG 27 2012
 
THE MUCH ANTICIPATED INTENSIFICATION PROCESS APPEARS TO HAVE FINALLY
STARTED BASED ON REPORTS FROM AN AIR FORCE RESERVE RECONNAISSANCE
AIRCRAFT AND FROM NEARBY NOAA BUOY 42003. THE CENTRAL PRESSURE HAS
DECREASED BY AT LEAST 7 MB SINCE THE PREVIOUS ADVISORY. THE HIGHEST
FLIGHT-LEVEL WINDS OBSERVED HAVE BEEN 74 KT IN THE SOUTHWEST
QUADRANT AND THE HIGHEST BIAS-ADJUSTED SFMR WINDS ARE NEAR 58 KT.
THESE DATA SUPPORT AN INTENSITY OF 60 KT.
 
ISAAC WOBBLED WESTWARD THIS AFTERNOON...BUT A REPRESENTATIVE INITIAL
MOTION ESTIMATE IS 305/10. THE LATEST 12Z NHC MODEL GUIDANCE IS IN
BETTER AGREEMENT ON A WEST-NORTHWEST TO NORTHWEST MOTION TOWARD THE
SOUTHEAST LOUISIANA AND MISSISSIPPI COASTAL AREAS OVER THE NEXT
36-48 HOURS. AFTER 48 HOURS...HOWEVER...THE MODEL GUIDANCE REMAINS
DIVERGENT ON THE HANDLING OF A SHORTWAVE TROUGH FORECAST TO DIG
SOUTHEASTWARD FROM THE UPPER MIDWEST AND INTO THE MID-ATLANTIC
REGION...FOLLOWED BY A RIDGE BUILDING IN BEHIND THE TROUGH. THE GFS
AND ECMWF...OUR MOST RELIABLE MODELS... NOW HAVE VERY SIMILAR
SOLUTIONS THROUGH DAY 5...AND THE OFFICIAL FORECAST TRACK IS
BETWEEN THOSE TWO MODELS.
 
SATELLITE DATA INDICATE ISAAC HAS BECOME BETTER ORGANIZED OVER THE
PAST 6 HOURS WITH THE DEVELOPMENT OF A CENTRAL DENSE OVERCAST CLOUD
PATTERN OVER THE CENTER ALONG WITH A DEVELOPING EYE IN RECON DATA.
SATELLITE DATA T-NUMBERS HAVE INCREASED TO T4.5/77 KT FROM TAFB AND
SAB. RECON WIND DATA INDICATE THE RADIUS OF MAXIMUM WINDS HAS ALSO
PULLED INWARD TO ABOUT 30 N MI. ALTHOUGH ADDITIONAL CONVECTION HAS
BEEN DEVELOPING IN THE NORTHEASTERN QUADRANT...DRY MID-LEVEL AIR
STILL LURKS JUST TO THE EAST AND SOUTHEAST OF THE CDO FEATURE...
WHICH COULD BE ENTRAINED INTO THE INNER CORE AT ANY TIME AND
DISRUPT THE DEVELOPMENT PROCESS. DUE TO THE PROXIMITY OF DRY
AIR...THE INTENSITY FORECAST INDICATES ONLY MODEST DEVELOPMENT FOR
THE NEXT 24 HOURS. HOWEVER...STRENGTHENING IS EXPECTED TO CONTINUE 
RIGHT UP UNTIL LANDFALL OCCURS DUE TO THE VERY WARM WATERS THE
CYCLONE WILL BE PASSING OVER AND THE VERY FAVORABLE UPPER-LEVEL
OUTFLOW REGIME THAT ISAAC IS FORECAST TO DEVELOP BY 24 HOURS. THE
INTENSITY FORECAST IS JUST SLIGHTLY HIGHER THAN THE MODEL GUIDANCE.
 
BECAUSE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE CENTER...IT IS
IMPORTANT NOT TO FOCUS ON THE EXACT FORECAST TRACK. THE SLOW FORWARD
SPED OF AROUND 5 KT AFTER LANDFALL WILL RESULT IN A HEAVY RAIN AND
FLOOD SITUATION FOR PORTIONS OF THE CENTRAL GULF COAST AND LOWER
MISSISSIPPI VALLEY REGIONS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/2100Z 26.4N  86.2W   60 KT  70 MPH
 12H  28/0600Z 27.4N  87.5W   70 KT  80 MPH
 24H  28/1800Z 28.6N  89.0W   80 KT  90 MPH
 36H  29/0600Z 29.5N  90.0W   85 KT 100 MPH...NEAR THE COAST
 48H  29/1800Z 30.3N  90.7W   75 KT  85 MPH...INLAND
 72H  30/1800Z 32.2N  91.8W   35 KT  40 MPH...INLAND
 96H  31/1800Z 35.9N  92.1W   25 KT  30 MPH...INLAND
120H  01/1800Z 38.7N  89.3W   20 KT  25 MPH...INLAND
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 280255
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  28
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 PM CDT MON AUG 27 2012
 
THE SATELLITE PRESENTATION OF ISAAC HAS NOT CHANGED VERY MUCH DURING
THE PAST FEW HOURS.  INFRARED AND MICROWAVE IMAGERY SHOW A STRONG
BAND OF CONVECTION...PERHAPS THE BEGINNING OF AN EYEWALL...WRAPPING
AROUND THE SOUTH AND EAST PORTIONS OF THE CIRCULATION.  HOWEVER...
AIRCRAFT OBSERVATIONS INDICATE THAT THE CONVECTIVE BAND WAS OPEN TO
THE NORTHWEST AND THAT THE LOW-LEVEL CENTER WAS DISPLACED A LITTLE
TO THE SOUTH OF THE ROTATION SEEN IN SATELLITE PICTURES.  THE
MINIMUM PRESSURE HAS NOT FALLEN SIGNIFICANTLY DURING THE PAST
SEVERAL HOURS AND THE NOAA AND AIR FORCE AIRCRAFT HAVE NOT REPORTED
WINDS ANY HIGHER THAN WHAT WAS MEASURED LATE THIS AFTERNOON.
THEREFORE...ISAAC REMAINS A 60-KT TROPICAL STORM FOR THIS ADVISORY.
ISAAC CONTINUES TO HAVE DIFFICULTLY MAINTAINING DEEP CONVECTION
OVER THE NORTHERN SEMICIRCLE LIKELY DUE TO SOME DRY AIR
ENTRAINMENT.  OTHERWISE...ENVIRONMENTAL CONDITIONS SHOULD BE
CONDUCIVE FOR STRENGTHENING UNTIL LANDFALL.  ISAAC IS FORECAST TO
BECOME A HURRICANE OVERNIGHT AND NHC INTENSITY FORECAST IS SLIGHTLY
HIGHER THAN MOST OF THE GUIDANCE.
 
ISAAC HAS BEEN MOVING NORTHWESTWARD OR 310 DEGREES AT 9 KT.  THE
TRACK GUIDANCE HAS CONTINUED TO COME INTO BETTER AGREEMENT DURING
THE FIRST 36 TO 48 HOURS OF THE FORECAST PERIOD.  ISAAC SHOULD MOVE
NORTHWESTWARD TOWARD THE NORTH-CENTRAL GULF COAST WHERE A BREAK IN
THE SUBTROPICAL RIDGE IS LOCATED.  AS A MID-LATITUDE TROUGH
BYPASSES ISAAC IN A DAY OR SO...SOME RIDGING BUILDS TO THE
NORTHWEST OF THE CYCLONE.  THIS IS EXPECTED TO CAUSE ISAAC TO
SLOW DOWN AS IT MOVES INLAND.  AFTER 72 HOURS...THE CYCLONE SHOULD
BEGIN TO MOVE A LITTLE FASTER TOWARD THE NORTH AND NORTHEAST AS IT
MOVES AROUND THE WESTERN SIDE OF A MID-LEVEL RIDGE THAT SLIDES
EASTWARD ACROSS THE OHIO VALLEY AND MID-ATLANTIC REGIONS.  THE NEW
NHC TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND REMAINS BETWEEN
THE ECMWF AND GFS MODELS.
 
ISAAC IS A LARGE TROPICAL CYCLONE.  A DANGEROUS STORM SURGE...HEAVY
RAINFALL...AND STRONG WINDS EXTEND WELL AWAY FROM THE CENTER AND
ARE EXPECTED TO AFFECT A LARGE PORTION OF THE NORTHERN GULF COAST.
THE THREAT OF HEAVY RAINFALL AND FLOODING IS ALSO EXPECTED TO
SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY REGION DURING THE
NEXT FEW DAYS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/0300Z 27.1N  87.0W   60 KT  70 MPH
 12H  28/1200Z 28.0N  88.0W   70 KT  80 MPH
 24H  29/0000Z 29.1N  89.2W   80 KT  90 MPH...ON THE COAST
 36H  29/1200Z 29.9N  90.1W   65 KT  75 MPH...INLAND
 48H  30/0000Z 30.7N  90.7W   50 KT  60 MPH...INLAND
 72H  31/0000Z 33.3N  91.7W   30 KT  35 MPH...INLAND
 96H  01/0000Z 37.5N  91.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  02/0000Z 40.5N  87.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BROWN/BLAKE
 

WTNT44 KNHC 280856
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 AM CDT TUE AUG 28 2012
 
REPORTS FROM THE AIR FORCE HURRICANE HUNTER AIRCRAFT INDICATE THAT
THE CENTRAL PRESSURE HAS DROPPED A LITTLE MORE...BUT SO FAR...THE
MAXIMUM FLIGHT-LEVEL AND SFMR-OBSERVED SURFACE WINDS STILL DO NOT
QUITE SUPPORT HURRICANE INTENSITY.  THE CURRENT INTENSITY IS HELD
AT 60 KT PENDING ADDITIONAL OBSERVATIONS FROM THE HURRICANE
HUNTERS.  ALTHOUGH THE WIND FIELD REMAINS RATHER BROAD AND
RELATIVELY FLAT...RECENT AIRCRAFT DATA SUGGEST THAT THE MAXIMUM
WINDS ARE NOW OCCURRING SOMEWHAT CLOSER TO THE CENTER OVER THE
NORTHERN SEMICIRCLE OF THE CYCLONE.  THIS WOULD SUGGEST THAT THE
INNER CORE CIRCULATION IS BECOMING BETTER DEFINED...AND
STRENGTHENING MIGHT BE IMMINENT.  UPPER-LEVEL OUTFLOW IS
WELL-ESTABLISHED OVER THE SOUTHERN SEMICIRCLE OF THE SYSTEM...BUT
CENTRAL CONVECTION CONTINUES TO FLUCTUATE.  THE LATTER IS
PRESUMABLY DUE TO A CONTINUED INTRUSION OF DRY AIR INTO THE CORE
REGION.  THE STATISTICAL-DYNAMICAL GUIDANCE IS A LITTLE LOWER THAN
IN PREVIOUS RUNS...AND THE STORM HAS ONLY ABOUT 12-24 HOURS BEFORE
MOVING INLAND.  THE OFFICIAL INTENSITY FORECAST IS JUST SLIGHTLY
LOWER THAN THE PREVIOUS ONE.
 
CENTER FIXES FROM THE AIRCRAFT INDICATE THAT THE STORM HAS WOBBLED
ON A GENERALLY WESTWARD COURSE OVER THE PAST FEW HOURS.  THIS IS
BELIEVED TO BE TEMPORARY...HOWEVER...AND THE LONGER-TERM MOTION
ESTIMATE IS ABOUT 305/10.  THE CURRENT AND FORECAST STEERING REGIME
ARE BASICALLY THE SAME AS IN THE PREVIOUS PACKAGE.  ISAAC IS
EXPECTED TO MOVE INTO A WEAKNESS IN THE SUBTROPICAL RIDGE NEAR THE
NORTH-CENTRAL GULF COAST...WITH SOME SLOWING OF FORWARD SPEED
DURING THE NEXT COUPLE OF DAYS AS A RIDGE BUILDS A LITTLE TO THE
NORTHWEST OF THE CYCLONE.  LATER ON...THE SYSTEM SHOULD TURN
NORTHWARD AND NORTHEASTWARD INTO THE OHIO VALLEY REGION AS IT MOVES
AROUND THE WESTERN PERIPHERY OF A MID-LEVEL ANTICYCLONE.
 
ISAAC IS A LARGE TROPICAL CYCLONE.  A DANGEROUS STORM SURGE...HEAVY
RAINFALL...AND STRONG WINDS EXTEND WELL AWAY FROM THE CENTER AND
ARE EXPECTED TO AFFECT A LARGE PORTION OF THE NORTHERN GULF COAST. 
FOR THIS REASON...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT CENTER
LOCATION.  THE THREAT OF HEAVY RAINFALL AND FLOODING IS ALSO
EXPECTED TO SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY REGION
DURING THE NEXT FEW DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/0900Z 27.5N  88.1W   60 KT  70 MPH
 12H  28/1800Z 28.5N  89.1W   70 KT  80 MPH
 24H  29/0600Z 29.5N  90.1W   75 KT  85 MPH...NEAR THE COAST
 36H  29/1800Z 30.3N  90.9W   55 KT  65 MPH...INLAND
 48H  30/0600Z 31.4N  91.5W   45 KT  50 MPH...INLAND
 72H  31/0600Z 34.5N  92.5W   25 KT  30 MPH...INLAND
 96H  01/0600Z 38.0N  91.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  02/0600Z 40.5N  87.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 281459
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  30
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 AM CDT TUE AUG 28 2012
 
REPORTS FROM AIR FORCE AND NOAA HURRICANE HUNTER AIRCRAFT INDICATE
THE CENTRAL PRESSURE HAS DECREASED TO ABOUT 976 MB SINCE THE
PREVIOUS ADVISORY...BUT IT HAS LEVELED OFF OVER THE PAST FEW HOURS.
THE MAXIMUM 850 MB FLIGHT-LEVEL WIND OBSERVED HAS BEEN 89 KT...
WHICH EQUATES TO A SURFACE WIND OF ABOUT 71 KT. HOWEVER...
BIAS-ADJUSTED SFMR SURFACE WINDS HAVE ONLY BEEN AROUND 60-62 KT...
WHICH CORRELATES WELL WITH DROPSONDE BOUNDARY LAYER-DERIVED SURFACE
WINDS. AS SUCH...THE INTENSITY OF ISAAC IS BEING MAINTAINED AT 60
KT...WHICH IS JUST BELOW HURRICANE STATUS.

CENTER FIXES FROM THE AIRCRAFT INDICATE THAT ISAAC HAS BEEN WOBBLING
IN A GENERAL NORTHWESTWARD MOTION OF 310/09 KT. THERE REMAINS NO
SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING.    
ISAAC IS FORECAST TO MOVE INTO A WEAKNESS IN THE SUBTROPICAL RIDGE
NEAR THE NORTH-CENTRAL GULF COAST OVER THE NEXT 24-36 HOURS...
ACCOMPANIED BY A GRADUAL DECREASE IN THE FORWARD SPEED. AS THE 
RIDGE BUILDS BACK IN TO THE NORTH OF THE CYCLONE...ISAAC IS
EXPECTED TO TURN A LITTLE MORE TOWARD THE WEST-NORTHWEST BEFORE IT
TURNS NORTHWARD ON DAY 4...AND MOVES NORTHEASTWARD INTO THE OHIO
VALLEY REGION ON DAY 5. THE OFFICIAL FORECAST TRACK HAS BEEN NUDGED
A LITTLE TO THE LEFT OF THE PREVIOUS ADVISORY TRACK AND LIES JUST
TO THE RIGHT OF THE CONSENSUS MODELS TV15 AND TCVA.

MID-LEVEL DRY AIR ENTRAINMENT CONTINUES TO PLAGUE ISAAC. AS SOON AS
THE CYCLONE DEVELOPS INNER-CORE CONVECTION AND THE APPEARANCE OF AN
EYE IN RADAR AND SATELLITE IMAGERY...THE CONVECTION ERODES DUE TO
THE DRY AIR. DESPITE THE FAVORABLE OCEANIC CONDITIONS AND
UPPER-LEVEL OUTFLOW REGIME...ISAAC ONLY HAS ABOUT 12-18 HOURS FOR
FURTHER STRENGTHENING TO OCCUR. THE OFFICIAL INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY...WITH ONLY TIMING ADJUSTMENTS
MADE TO THE INTENSITY FORECAST...AND CLOSELY FOLLOWS THE INTENSITY
MODEL CONSENSUS.
 
ISAAC IS A LARGE TROPICAL CYCLONE.  A DANGEROUS STORM SURGE...HEAVY
RAINFALL...AND STRONG WINDS EXTEND WELL AWAY FROM THE CENTER AND
ARE EXPECTED TO AFFECT A LARGE PORTION OF THE NORTHERN GULF COAST.
FOR THIS REASON...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT CENTER
LOCATION.  THE THREAT OF HEAVY RAINFALL AND FLOODING IS ALSO
EXPECTED TO SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY REGION
DURING THE NEXT FEW DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/1500Z 28.1N  88.5W   60 KT  70 MPH
 12H  29/0000Z 28.8N  89.4W   70 KT  80 MPH
 24H  29/1200Z 29.7N  90.4W   65 KT  75 MPH...INLAND
 36H  30/0000Z 30.5N  91.5W   45 KT  50 MPH...INLAND
 48H  30/1200Z 32.0N  92.0W   35 KT  40 MPH...INLAND
 72H  31/1200Z 35.0N  92.5W   20 KT  25 MPH...INLAND
 96H  01/1200Z 38.5N  90.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  02/1200Z 41.0N  86.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 282053
TCDAT4
 
HURRICANE ISAAC DISCUSSION NUMBER  31
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 PM CDT TUE AUG 28 2012
 
SINCE THE LAST RECON FLIGHTS INTO ISAAC...WHEN A BIAS-CORRECTED SFMR
WIND OF 64 KT WAS OBSERVED...THE RADAR AND SATELLITE APPEARANCE HAS
CONTINUED TO BECOME BETTER DEFINED. ON THIS BASIS...THE ESTIMATED 
INTENSITY HAS BEEN INCREASED TO 70 KT.

TRENDING THROUGH ALL OF THE WIGGLES AND WOBBLES IN THE AIRCRAFT
FIXES YIELDS A GENERAL NORTHWESTWARD MOTION OF 310/07 KT. ISAAC
REMAINS ON TRACK...AND THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE
EARLY PART OF THE FORECAST. ISSAC IS EXPECTED TO CONTINUE
NORTHWESTWARD TOWARD A WEAKNESS IN THE SUBTROPICAL RIDGE THAT IS
ORIENTED EAST-WEST ALONG 30N LATITUDE. BECAUSE OF THIS WEAKNESS...
THE STEERING FLOW IS FORECAST TO DECREASE OVER THE NEXT 36-48
HOURS...WHICH WILL RESULT IN ISAAC SLOWING DOWN SOME MORE.
AFTERWARDS...THE RIDGE IS FORECAST TO BUILD BACK IN BY ALL OF THE
MODELS...ALBEIT TO VARYING DEGREES...WHICH SHOULD CAUSE THE CYCLONE
TO TURN SLIGHTLY TOWARD THE WEST-NORTHWEST BEFORE IT TURNS
NORTHWARD BY DAY 4...AND THEN MOVE NORTHEASTWARD INTO THE LOWER
GREAT LAKES AND OHIO VALLEY REGIONS BY DAY 5. IN THE LATTER PART OF
THE FORECAST PERIOD THE FORECAST HAS BEEN NUDGED A LITTLE TO THE
LEFT OF THE PREVIOUS TRACK...BUT REMAINS TO THE RIGHT OF THE
CONSENSUS MODELS THAT HAVE RECENTLY HAD A LEFTWARD BIAS.
 
ALTHOUGH NOT EXPLICITLY FORECAST DUE TO LAND INTERACTION AT 12
HOURS...FAVORABLE WATER TEMPERATURES ALONG WITH AN IMPRESSIVE
UPPER-LEVEL OUTFLOW REGIME SUGGEST THAT ISAAC COULD STRENGTHEN A
LITTLE MORE BEFORE LANDFALL OCCURS.  HOWEVER...BECAUSE OF THE
UNUSUALLY LARGE WIND FIELD...RAPID INTENSIFICATION IS NOT EXPECTED.
 
ISAAC REMAINS A LARGE TROPICAL CYCLONE. A DANGEROUS STORM
SURGE...HEAVY RAINFALL...AND STRONG WINDS EXTEND WELL AWAY FROM THE
CENTER AND ARE EXPECTED TO AFFECT A LARGE PORTION OF THE NORTHERN
GULF COAST. FOR THIS REASON...IT IS IMPORTANT NOT TO FOCUS ON THE
EXACT CENTER LOCATION. THE THREAT OF HEAVY RAINFALL AND FLOODING IS
ALSO EXPECTED TO SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY
REGION DURING THE NEXT FEW DAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  28/2100Z 28.7N  89.2W   70 KT  80 MPH
 12H  29/0600Z 29.4N  90.0W   70 KT  80 MPH...INLAND
 24H  29/1800Z 30.3N  91.0W   55 KT  65 MPH...INLAND
 36H  30/0600Z 31.3N  91.9W   35 KT  40 MPH...INLAND
 48H  30/1800Z 33.0N  92.5W   30 KT  35 MPH...INLAND
 72H  31/1800Z 36.0N  92.5W   20 KT  25 MPH...INLAND
 96H  01/1800Z 39.0N  90.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  02/1800Z 41.5N  86.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 290252
TCDAT4
 
HURRICANE ISAAC DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 PM CDT TUE AUG 28 2012
 
ISAAC PASSED OVER THE MISSISSIPPI RIVER DELTA IN EXTREME SOUTHEAST
LOUISIANA AROUND 2345 UTC.  SINCE THAT TIME...THE CENTER HAS
WOBBLED WESTWARD AND HAS MOVED BACK OVER WATER. A NORTHWESTWARD
MOTION HAS RECENTLY RESUMED AND A SECOND LANDFALL SHOULD OCCUR
LATER TONIGHT NEAR GRAND ISLE.  DATA FROM NOAA AND AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT INDICATE THAT THE MINIMUM
PRESSURE HAS CONTINUED TO GRADUALLY FALL AND IS NOW 968 MB. THE AIR
FORCE RESERVE AIRCRAFT HAS MEASURED A PEAK 850-MB FLIGHT-LEVEL WIND
OF 96 KT AND BIAS-CORRECTED SFMR WINDS OF AROUND 65 KT.  BASED ON
THESE DATA...THE INITIAL INTENSITY REMAINS 70 KT.  LITTLE CHANGE IN
STRENGTH IS EXPECTED DURING THE NEXT 12 HOURS OR SO AS THE CENTER
MOVES ACROSS THE BAYOUS OF SOUTHEASTERN LOUISIANA.  STEADY
WEAKENING SHOULD COMMENCE LATER WEDNESDAY AS THE CENTER MOVES
FARTHER INLAND.
 
SMOOTHING THROUGH THE WOBBLES DURING THE PAST FEW HOURS...THE LONGER
TERM MOTION ESTIMATE IS 310/7 KT.  ISAAC IS EXPECTED TO MOVE SLOWLY
NORTHWESTWARD DURING THE NEXT 24 TO 36 HOURS AS A MID-LEVEL RIDGE TO
THE NORTHWEST OF THE CYCLONE SLIDES EASTWARD.  AS THE RIDGE MOVES
ACROSS THE OHIO VALLEY AND INTO THE MID-ATLANTIC REGION...THIS
SHOULD CAUSE ISAAC TO TURN NORTH-NORTHWESTWARD AND NORTHWARD IN A
COUPLE OF DAYS.  AFTER THAT TIME...THE CYCLONE IS EXPECTED TO TURN
NORTHEASTWARD AS IT ENTERS THE MID-LATITUDE WESTERLY FLOW.  THE
GLOBAL MODEL GUIDANCE HAS BEEN SHIFTING WESTWARD DURING THE PAST
COUPLE OF RUNS...AND THE NHC FORECAST HAS BEEN ADJUSTED IN THAT
DIRECTION.
 
BECAUSE OF THE SLOW MOTION OF ISAAC...A PROLONGED PERIOD OF STRONG
WINDS AND HEAVY RAINFALL ARE EXPECTED OVER A LARGE PORTION OF THE
NORTHERN GULF COAST.  THE THREAT OF HEAVY RAINFALL AND FLOODING IS
ALSO EXPECTED TO SPREAD INLAND OVER THE LOWER MISSISSIPPI VALLEY
REGION DURING THE NEXT FEW DAYS.
 
NATIONAL OCEAN SERVICE TIDE GAUGES INDICATE THAT STORM SURGE HEIGHTS
OF 6 TO 10 FEET ARE OCCURRING ALONG PORTIONS OF THE COAST OF
SOUTHEASTERN LOUISIANA AND MISSISSIPPI.  GIVEN THE LONG DURATION
OF ONSHORE FLOW IN THESE AREAS...WATER LEVELS ARE EXPECTED TO REMAIN
HIGH FOR THE NEXT 12 TO 24 HOURS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0300Z 29.0N  89.7W   70 KT  80 MPH
 12H  29/1200Z 29.6N  90.6W   65 KT  75 MPH...INLAND
 24H  30/0000Z 30.3N  91.4W   55 KT  65 MPH...INLAND
 36H  30/1200Z 31.5N  92.3W   35 KT  40 MPH...INLAND
 48H  31/0000Z 33.2N  93.2W   25 KT  30 MPH...INLAND
 72H  01/0000Z 37.0N  94.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  02/0000Z 40.0N  91.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  03/0000Z 41.5N  86.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 290858
TCDAT4
 
HURRICANE ISAAC DISCUSSION NUMBER  33
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 AM CDT WED AUG 29 2012
 
AFTER REMAINING QUASI-STATIONARY FOR SEVERAL HOURS...AIRCRAFT AND
RADAR DATA INDICATE THAT THE CENTER OF ISAAC MADE A SECOND LANDFALL
NEAR PORT FOURCHON LOUISIANA AND IS BEGINNING TO MOVE INLAND OVER
SOUTHEAST LOUISIANA.  OBSERVATIONS FROM THE HURRICANE HUNTER
AIRCRAFT INDICATE THAT THE EYE IS OPEN OVER THE WESTERN PORTION OF
THE CIRCULATION...AND THE RADAR PRESENTATION HAS BECOME MORE
ASYMMETRIC OVER THE PAST COUPLE OF HOURS.  HOWEVER...THE RADAR
REFLECTIVITIES INDICATE THAT CONVECTION HAS BECOME STRONGER OVER
THE NORTHERN AND EASTERN PORTIONS OF THE CYCLONE...AND THE AIRCRAFT
REPORTED THAT THE CENTRAL PRESSURE REMAINS QUITE LOW.  THE CURRENT
INTENSITY IS HELD AT 70 KT...BUT WEAKENING IS IMMINENT NOW THAT THE
CENTER HAS BEGUN TO MOVE OVER LAND.  FOR THE NEXT 24 HOURS OR
SO...THE OFFICIAL INTENSITY FORECAST SHOWS A SOMEWHAT SLOWER RATE
OF WEAKENING THAN THAT GIVEN BY THE INLAND DECAY MODEL DUE TO THE
SWAMPY TERRAIN THAT THE SYSTEM WILL TRAVERSE. 

SINCE THE SYSTEM HAS ONLY BEGUN TO MOVE RECENTLY...THE INITIAL
MOTION IS AN UNCERTAIN 300/7.  ISAAC IS CURRENTLY MOVING THROUGH A
WEAKNESS IN THE SUBTROPICAL RIDGE.  OVER THE NEXT FEW DAYS...A
MID-LEVEL ANTICYLONE SHIFTS EASTWARD OVER THE CENTRAL AND EASTERN
UNITED STATES.  AS A RESULT...ISAAC SHOULD GRADUALLY TURN TOWARD
THE NORTH AND NORTHEAST DURING THE FORECAST PERIOD.  NEAR THE END
OF THE PERIOD...POST-TROPICAL ISAAC SHOULD MOVE EAST-NORTHEASTWARD
IN THE FLOW BETWEEN THE MID-LATITUDE WESTERLIES AND THE
AFOREMENTIONED ANTICYLONE.  THE OFFICIAL TRACK FORECAST IS SIMILAR
TO THE PREVIOUS ONE AND CLOSE TO THE MODEL CONSENSUS.

SINCE THE SYSTEM IS LIKELY TO MOVE SLOWLY OVER THE NEXT 24 HOURS OR
SO...THERE IS A CONTINUED THREAT OF FLOODING FROM HEAVY RAINS OVER
THE NORTHERN GULF COAST AREA.

NATIONAL OCEAN SERVICE TIDE GAUGES INDICATE THAT STORM SURGE HEIGHTS
OF 6 TO 10 FEET ARE STILL OCCURRING ALONG PORTIONS OF THE COAST OF
SOUTHEASTERN LOUISIANA AND MISSISSIPPI.  GIVEN THE LONG DURATION
OF ONSHORE FLOW IN THESE AREAS...WATER LEVELS ARE EXPECTED TO REMAIN
HIGH THROUGH TODAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0900Z 29.2N  90.5W   70 KT  80 MPH...INLAND
 12H  29/1800Z 29.7N  91.1W   65 KT  75 MPH...INLAND
 24H  30/0600Z 30.5N  91.8W   50 KT  60 MPH...INLAND
 36H  30/1800Z 31.8N  92.8W   30 KT  35 MPH...INLAND
 48H  31/0600Z 33.6N  93.7W   25 KT  30 MPH...INLAND
 72H  01/0600Z 37.5N  93.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  02/0600Z 39.5N  90.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  03/0600Z 40.5N  86.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER PASCH/ROBERTS
 

WTNT44 KNHC 291451
TCDAT4
 
HURRICANE ISAAC DISCUSSION NUMBER  34
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 AM CDT WED AUG 29 2012
 
HURRICANE ISAAC IS INLAND OVER SOUTHEASTERN LOUISIANA NEAR HOUMA.
THE CYCLONE HAS MAINTAINED AN IMPRESSIVE RADAR SIGNATURE...WHICH
INCLUDES A RAGGED 40-NMI DIAMETER EYE. CURVED CONVECTIVE RAINBANDS
HAVE INCREASED IN THE EASTERN SEMICIRCLE...AND DOPPLER RADAR
VELOCITIES OF NEAR 80 KT OVER WATER SUPPORT KEEPING ISAAC AS A
MINIMAL HURRICANE FOR THIS ADVISORY. SIMILAR DOPPLER VELOCITIES
OVER LAND AND OVER LAKE PONTCHARTRAIN SUGGEST WIND GUSTS TO NEAR 80
KT COULD OCCUR INLAND OVER SOUTHEASTERN LOUISIANA INTO THIS
AFTERNOON. BY LATE THIS AFTERNOON OR EVENING...HOWEVER...ISAAC IS
FORECAST TO WEAKEN TO A TROPICAL STORM...AND BECOME A TROPICAL
DEPRESSION BY THURSDAY NIGHT.

THE INITIAL MOTION ESTIMATE IS 310/5. ISAAC IS EXPECTED TO MOVE
SLOWLY NORTHWESTWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE
FOR THE NEXT 24 HOURS...AND THEN TURN NORTH-NORTHWESTWARD AND
NORTHWARD AROUND THE WESTERN PERIPHERY OF THE RIDGE BY 36 AND 48
HOURS...RESPECTIVELY. BY 72 HOURS...ISAAC IS FORECAST TO BECOME A
POST-TROPICAL REMNANT LOW PRESSURE SYSTEM THAT SHOULD MOVE
NORTHEASTWARD TO EAST-NORTHEASTWARD WHEN IT WILL BE CAUGHT UP IN
WEAK MID-LATITUDE WESTERLIES. THERE ARE CURRENTLY NO INDICATIONS IN
ANY OF THE MODEL GUIDANCE SUGGESTING THAT ISAAC WILL TAP INTO ANY
BAROCLINIC ENERGY SOURCES THAT COULD RESULT IN EXTRATROPICAL
STRENGTHENING OVER THE CENTRAL UNITED STATES. THE OFFICIAL TRACK
FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY TRACK AND IS JUST EAST
OF THE MODEL CONSENSUS.
 
SINCE ISAAC IS FORECAST TO MOVE SLOWLY OVER THE NEXT 24-36 HOURS...
THERE WILL BE A PROLONGED THREAT OF FLOODING FROM HEAVY RAINS OVER
THE NORTHERN GULF COAST AREA AND THE SOUTH-CENTRAL UNITED STATES.
 
NATIONAL OCEAN SERVICE TIDE GAGES INDICATE THAT STORM SURGE HEIGHTS
OF 6 TO 8 FEET ARE STILL OCCURRING ALONG PORTIONS OF THE COAST OF
SOUTHEASTERN LOUISIANA AND MISSISSIPPI.  GIVEN THE LONG DURATION
OF ONSHORE FLOW IN THESE AREAS...WATER LEVELS ARE EXPECTED TO REMAIN
HIGH THROUGH TODAY.
 
A SPECIAL THANKS TO THE CREWS OF THE AIR FORCE RESERVE AND NOAA
HURRICANE HUNTERS WHO FLEW A TOTAL OF 34 HAZARDOUS MISSIONS INTO
ISAAC...WHICH RESULTED IN AN IMPRESSIVE TOTAL OF 95 CENTER FIXES.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 29.6N  90.7W   65 KT  75 MPH...INLAND
 12H  30/0000Z 30.2N  91.4W   55 KT  65 MPH...INLAND
 24H  30/1200Z 31.2N  92.2W   45 KT  50 MPH...INLAND
 36H  31/0000Z 32.8N  93.1W   30 KT  35 MPH...INLAND
 48H  31/1200Z 34.6N  93.5W   25 KT  30 MPH...INLAND
 72H  01/1200Z 38.0N  92.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  02/1200Z 40.0N  89.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  03/1200Z 41.0N  85.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 292056
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  35
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 PM CDT WED AUG 29 2012
 
ISAAC CONTINUES TO TRUDGE SLOWLY TO THE NORTHWEST ACROSS
SOUTHEASTERN LOUISIANA...AND THE INITIAL MOTION REMAINS  310/5
KT...BASED ON DOPPLER RADAR DATA FROM SLIDELL AND FT. POLK
LOUISIANA. THE MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH
THE PREVIOUS OFFICIAL TRACK...SO NO SIGNIFICANT CHANGES WERE MADE
FOR THIS ADVISORY. ISAAC SHOULD CONTINUE TO MOVE NORTHWESTWARD AND
EVENTALLY NORTHWARD THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE
OVER THE NEXT 36-48 HOURS. BY DAY 3 WHEN THE REMNANT CYCLONE IS
OVER THE UPPER-MIDWEST...ISAAC SHOULD TURN EAST-NORTHEASTWARD WHEN
IT INTERACTS WITH WEAK MID-LATITUDE WESTERLY FLOW. THE OFFICIAL
FORECAST TRACK IS JUST AN UPDATE OF THE PREVIOUS ADVISORY
TRACK...AND LIES BETWEEN THE MODEL CONSENSUS AND THE ECMWF MODEL.

STRONG BANDS OF THUNDERSTORMS CONTINUE TO DEVELOP OVER WATER IN THE
THE EASTERN SEMICIRCLE AND ALSO SOUTHWEST OF THE CENTER. THEY HAVE
OCCASIONALLY PRODUCED SUSTAINED TROPICAL-STORM-FORCE WINDS ALONG
WITH GUSTS EXCEEDING 60 KT. THOSE STRONG RAINBANDS WILL GRADUALLY
SPREAD WESTWARD TONIGHT ACROSS THE COASTAL AREAS OF SOUTHEASTERN
LOUISIANA AND SOUTHERN MISSISSIPPI...INCLUDING THE NEW ORLEANS
METROPOLITAN AREA. BY THURSDAY NIGHT...ISAAC COULD WEAKEN TO A
TROPICAL DEPRESSION...AND IT SHOULD BECOME A POST-TROPICAL REMNANT
LOW PRESSURE SYSTEM BY FRIDAY. THERE REMAINS NO INDICATION IN ANY
OF THE NHC MODEL GUIDANCE THAT ISAAC WILL BE ABLE TO ACQUIRE ANY
BAROCLINIC ENERGY THAT COULD CAUSE IT TO STRENGTHEN INTO A
SIGNIFICANT EXTRATROPICAL LOW WHILE IT IS OVER THE UNITED STATES.
 
SINCE ISAAC WILL CONTINUE TO MOVE SLOWLY OVER THE NEXT 24-36
HOURS...THERE WILL BE A PROLONGED THREAT OF FLOODING FROM HEAVY
RAINS OVER THE NORTHERN GULF COAST AREA AND THE SOUTH-CENTRAL
UNITED STATES.
 
NATIONAL OCEAN SERVICE TIDE GAGES INDICATE THAT STORM SURGE HEIGHTS
OF NEAR 7 FEET ARE STILL OCCURRING ALONG PORTIONS OF THE COAST OF
SOUTHEASTERN LOUISIANA AND MISSISSIPPI.  GIVEN THE LONG DURATION
OF ONSHORE FLOW IN THESE AREAS...WATER LEVELS ARE EXPECTED TO REMAIN
HIGH THROUGH TONIGHT.

PUBLIC ADVISORY TIMES HAVE REVERTED BACK TO A 3-HOURLY CYCLE. THE
NEXT INTERMEDIATE PUBLIC ADVISORY WILL BE ISSUED AT 700 PM
CDT/0000Z.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/2100Z 30.0N  91.1W   60 KT  70 MPH...INLAND
 12H  30/0600Z 30.7N  91.7W   50 KT  60 MPH...INLAND
 24H  30/1800Z 32.0N  92.6W   40 KT  45 MPH...INLAND
 36H  31/0600Z 33.8N  93.3W   30 KT  35 MPH...INLAND
 48H  31/1800Z 35.7N  93.4W   25 KT  30 MPH...INLAND
 72H  01/1800Z 38.6N  91.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  02/1800Z 40.0N  88.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  03/1800Z 40.5N  83.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 300255
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  36
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 PM CDT WED AUG 29 2012
 
NATIONAL WEATHER SERVICE DOPPLER RADAR IMAGERY SHOWS THAT ISAAC
CONTINUES TO MOVE SLOWLY NORTHWESTWARD AT ABOUT 5 KT OVER
SOUTHEASTERN LOUISIANA.  THE SLOW FORWARD SPEED IS EXPECTED TO
PERSIST OVERNIGHT.  HOWEVER...A SLIGHT INCREASE IS FORWARD SPEED
AND A TURN TOWARD THE NORTH-NORTHWEST SHOULD OCCUR ON THURSDAY 
AS ISAAC MOVES AROUND THE WESTERN PERIPHERY OF A RIDGE THAT MOVES
EASTWARD INTO THE MID-ATLANTIC REGION.  IN 2 TO 3 DAYS...THE
CYCLONE SHOULD TURN NORTHEASTWARD...THEN EASTWARD AS IT ENTERS AN
AREA OF WEAK MID-LATITUDE WESTERLY FLOW. THE OFFICIAL FORECAST IS
CLOSE TO THE PREVIOUS TRACK THROUGH 36 HOURS...BUT IS ADJUSTED
SLIGHTLY WEST AT 48 AND 72 HOURS TO BE CLOSER TO THE LATEST
GUIDANCE.
 
RECENT WIND OBSERVATIONS NEAR THE NORTHERN GULF COAST INDICATE
THAT THE MAXIMUM WINDS ARE ABOUT 50 KT. THESE WINDS ARE PRIMARILY
OCCURRING OVER WATER.  CONTINUED WEAKENING IS EXPECTED AND ISAAC
SHOULD BECOME A TROPICAL DEPRESSION BY THURSDAY EVENING.
 
HEAVY RAINFALL AND A SIGNIFICANT FLOOD THREAT ARE EXPECTED TO SPREAD
INLAND ACROSS PORTIONS OF THE CENTRAL UNITED STATES DURING THE NEXT
SEVERAL DAYS.  WATER LEVELS ALONG THE NORTHERN GULF COAST WILL
REMAIN ELEVATED THROUGH EARLY THURSDAY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/0300Z 30.3N  91.2W   50 KT  60 MPH
 12H  30/1200Z 31.2N  92.0W   40 KT  45 MPH...INLAND
 24H  31/0000Z 32.8N  92.9W   30 KT  35 MPH...INLAND
 36H  31/1200Z 34.9N  93.6W   25 KT  30 MPH...INLAND
 48H  01/0000Z 37.3N  93.4W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  02/0000Z 39.5N  91.3W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  03/0000Z 40.0N  87.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  04/0000Z 40.5N  83.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 300852
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  37
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 AM CDT THU AUG 30 2012
 
ISAAC IS SLOWLY WEAKENING AS MORE OF ITS LARGE CIRCULATION MOVES
OVER LAND.  BASED ON THE LATEST SURFACE WIND OBSERVATIONS NEAR THE
NORTHERN GULF COAST...THE MAXIMUM WINDS HAVE DIMINISHED TO NEAR 40
KT.  THESE WINDS ARE OCCURRING PRIMARILY OVER WATER OR ALONG THE
COASTLINE.   CONTINUED GRADUAL WEAKENING IS EXPECTED...AND ISAAC IS
LIKELY TO BECOME A TROPICAL DEPRESSION BY THIS EVENING.  THE
OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ONE...AND IS
MORE OR LESS IN AGREEMENT WITH THE STATISTICAL-DYNAMICAL GUIDANCE.
 
CENTER FIXES USING SURFACE SYNOPTIC DATA AND NATIONAL WEATHER
SERVICE DOPPLER RADAR IMAGERY INDICATE THAT ISAAC IS MOVING
NORTHWESTWARD AT A SLIGHTLY FASTER PACE...325/7.  THE TRACK
FORECAST AND PROGNOSTIC REASONING REMAIN ESSENTIALLY UNCHANGED.
OVER THE NEXT SEVERAL DAYS...THE PRIMARY STEERING MECHANISM SHOULD
BE THE FLOW BETWEEN THE MID-LATITUDE WESTERLIES AND A RIDGE OVER
THE SOUTHEASTERN UNITED STATES.  AS A RESULT THE CYCLONE IS
EXPECTED TO TURN NORTHWARD...NORTHEASTWARD...AND EASTWARD DURING
THE FORECAST PERIOD.  THE OFFICIAL TRACK FORECAST IS VERY CLOSE TO
THE PREVIOUS ONE...AND ALSO CLOSE TO THE LATEST DYNAMICAL MODEL
CONSENSUS.
 
HEAVY RAINFALL AND A SIGNIFICANT FLOOD THREAT ARE EXPECTED TO SPREAD
INLAND ACROSS PORTIONS OF THE CENTRAL UNITED STATES DURING THE NEXT
SEVERAL DAYS.  WATER LEVELS ALONG THE NORTHERN GULF COAST WILL
REMAIN ELEVATED THROUGH AT LEAST THIS MORNING.  TORNADOES REMAIN A
THREAT AS WELL FROM THIS SYSTEM TODAY. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/0900Z 30.9N  91.6W   40 KT  45 MPH
 12H  30/1800Z 31.9N  92.3W   35 KT  40 MPH...INLAND
 24H  31/0600Z 33.8N  93.2W   30 KT  35 MPH...INLAND
 36H  31/1800Z 36.0N  93.5W   25 KT  30 MPH...INLAND
 48H  01/0600Z 38.0N  93.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  02/0600Z 39.5N  90.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  03/0600Z 40.0N  86.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  04/0600Z 40.5N  82.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 301441
TCDAT4
 
TROPICAL STORM ISAAC DISCUSSION NUMBER  38
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
1000 AM CDT THU AUG 30 2012
 
CENTER FIXES USING SURFACE OBSERVATIONS AND NOAA DOPPLER WEATHER
RADARS INDICATE THAT ISAAC IS MOVING NORTHWESTWARD AT 330/08 KT. 
THE FORECAST TACK AND REASONING REMAIN BASICALLY UNCHANGED FROM THE
PREVIOUS ADVISORY. ISAAC AND ITS REMNANTS ARE EXPECTED TO BE
STEERED NORTHWARD AROUND THE WESTERN PORTION OF A SUBTROPICAL RIDGE
THAT IS LOCATED OVER THE SOUTHEASTERN U.S. THROUGH DAY 2...AND THEN
TURN NORTHEASTWARD AND EASTWARD ON DAY 3-5 AS THE SYSTEM MOVES INTO
WEAK MID-LATITUDE WESTERLY FLOW. THE OFFICIAL TRACK FORECAST IS
VERY CLOSE TO THE PREVIOUS ONE...AND LIES CLOSE TO THE LATEST
DYNAMICAL MODEL CONSENSUS.
 
THE INITIAL INTENSITY HAS BEEN DECREASED TO 35 KT...AND THAT IS IN 
SMALL AREA OVER WATER BETWEEN SOUTHEASTERN LOUISIANA AND THE
MISSISSIPPI COAST...AND PERHAPS EXTENDING A FEW MILES INLAND.
ISAAC WILL CONTINUE TO WEAKEN OVER LAND AND IT IS LIKELY TO BECOME A
TROPICAL DEPRESSION BY THIS EVENING...AND BECOME A POST-TROPICAL
REMNANT LOW BY SATURDAY...IF NOT SOONER.  THE OFFICIAL INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ONE...AND CLOSELY FOLLOWS THE
DECAY-SHIPS STATISTICAL-DYNAMICAL INTENSITY MODEL.

HEAVY RAINFALL AND A SIGNIFICANT FLOOD THREAT WILL CONTINUE TO
SPREAD INLAND ACROSS PORTIONS OF THE CENTRAL UNITED STATES DURING
THE NEXT SEVERAL DAYS. WATER LEVELS ALONG THE NORTHERN GULF COAST
WILL REMAIN ELEVATED THROUGH AT LEAST THIS MORNING. THE THREAT FOR
TORNADOES WITH THIS SYSTEM ALSO APPEARS TO BE INCREASING TODAY.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/1500Z 31.7N  92.1W   35 KT  40 MPH...INLAND
 12H  31/0000Z 33.0N  92.8W   30 KT  35 MPH...INLAND
 24H  31/1200Z 35.0N  93.3W   25 KT  30 MPH...INLAND
 36H  01/0000Z 37.0N  93.3W   20 KT  25 MPH...INLAND
 48H  01/1200Z 38.4N  92.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  02/1200Z 39.4N  89.2W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  03/1200Z 39.5N  86.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  04/1200Z 39.5N  83.0W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 302048
TCDAT4
 
TROPICAL DEPRESSION ISAAC DISCUSSION NUMBER  39
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092012
400 PM CDT THU AUG 30 2012
 
SURFACE OBSERVATIONS AND NOAA DOPPLER WEATHER RADARS INDICATE THAT
ISAAC IS MOVING NORTH-NORTHWESTWARD AT 340/11 KT. ISAAC WILL
GRADUALLY TURN TO THE NORTH OVER THE NEXT 24-36 HOURS...AND MOVE
ACROSS ARKANSAS AND INTO MISSOURI. BY DAY 3...THE REMNANTS OF ISAAC
SHOULD TURN NORTHEASTWARD AND THEN EASTWARD AS THE SYSTEM MOVES
INTO WEAK MID-LATITUDE WESTERLY FLOW. THE OFFICIAL TRACK FORECAST
IS VERY CLOSE TO THE PREVIOUS ONE...AND LIES JUST TO THE RIGHT OF
THE CONSENSUS MODELS TCVA AND TV15.
 
THE INITIAL INTENSITY HAS BEEN DECREASED TO 30 KT...BASED ON SURFACE
OBSERVATIONS AND DOPPLER RADAR VELOCITY DATA. ISAAC WILL CONTINUE
TO WEAKEN OVER LAND AND IT IS EXPECTED TO BECOME A POST-TROPICAL
REMNANT LOW BY SATURDAY...IF NOT SOONER.  THE OFFICIAL INTENSITY
FORECAST IS SIMILAR TO THE PREVIOUS ONE...AND CLOSELY FOLLOWS THE
DECAY-SHIPS STATISTICAL-DYNAMICAL INTENSITY MODEL.
 
HEAVY RAINFALL AND A SIGNIFICANT FLOOD THREAT WILL CONTINUE TO
SPREAD INLAND ACROSS PORTIONS OF THE CENTRAL UNITED STATES DURING
THE NEXT SEVERAL DAYS. WATER LEVELS ALONG THE NORTHERN GULF COAST
WILL REMAIN ELEVATED THROUGH THIS EVENING...AND THEN GRADUALLY
SUBSIDE ON FRIDAY. THE THREAT FOR TORNADOES WITH THIS SYSTEM WILL
CONTINUE THROUGH TONIGHT.
 
THIS IS THE LAST ADVISORY ON ISAAC ISSUED BY THE NATIONAL HURRICANE
CENTER. FUTURE INFORMATION ON THIS SYSTEM CAN BE FOUND IN PUBLIC
ADVISORIES ISSUED BY THE HYDROMETEOROLOGICAL PREDICTION CENTER...
UNDER AWIPS HEADER TCPAT4 AND WMO HEADER WTNT34 KWNH...BEGINNING AT
10 PM CDT.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  30/2100Z 32.7N  92.6W   30 KT  35 MPH...INLAND
 12H  31/0600Z 34.0N  93.0W   25 KT  30 MPH...INLAND
 24H  31/1800Z 36.0N  93.2W   20 KT  25 MPH...INLAND
 36H  01/0600Z 37.7N  92.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  01/1800Z 38.6N  91.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  02/1800Z 39.5N  88.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  03/1800Z 39.5N  85.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
120H  04/1800Z 38.5N  82.5W   15 KT  15 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER STEWART
 

