WTNT45 KNHC 072102
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 PM CDT WED SEP 07 2011
 
SATELLITE IMAGES INDICATE THAT THE AREA OF LOW PRESSURE IN THE BAY
OF CAMPECHE HAS BECOME BETTER ORGANIZED WITH CURVED BANDING
FEATURES NOTED.  SURFACE OBSERVATIONS FROM LAND AND PEMEX OIL
RIGS...ALONG WITH AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT
DATA...SHOW THAT THE LOW-LEVEL CIRCULATION IS WELL DEFINED...WITH
LITTLE TEMPERATURE GRADIENT NOTED.  THUS ADVISORIES ARE INITIATED
ON THIS SYSTEM.  SINCE THE RECON PLANE FOUND 53 KT AT FLIGHT LEVEL
ALONG WITH SFMR VALUES OF 40 TO 45 KT...THE CYCLONE IS BEING NAMED
NATE WITH A CONSERVATIVE INITIAL WIND SPEED OF 40 KT.

NATE IS FORECAST TO BE OVER VERY WARM WATERS WITH LITTLE VERTICAL
WIND SHEAR FOR THE NEXT FEW DAYS.  THE ONLY SIGNIFICANT INHIBITING
FACTOR IS A LARGE AREA OF DRY AIR SEEN IN WATER VAPOR IMAGES
NORTHWEST OF THE SYSTEM.  HOWEVER...THIS DRY AIR WILL TAKE SOME
TIME TO WORK ITS WAY INTO THE CENTER...IF AT ALL...IN A LOW SHEAR
ENVIRONMENT.  MOST MODELS SHOW INTENSIFICATION THROUGHOUT THE
FORECAST PERIOD...AND THE OFFICIAL FORECAST IS CLOSE TO A BLEND OF
THE LGEM AND SHIPS MODELS.     

THE CYCLONE HAS BEEN DRIFTING DURING THE DAY...WITH A LONG-TERM
MOTION OF ABOUT 110/2.  NATE IS IN AN AREA OF VERY WEAK STEERING
FLOW BETWEEN THE REMNANTS OF LEE OVER THE EASTERN UNITED STATES AND
A RIDGE OVER NORTHERN MEXICO.  LITTLE NET MOTION IS EXPECTED FOR
THE NEXT DAY OR SO DUE TO THIS PATTERN.  AFTER THAT TIME...A RIDGE
OVER THE WESTERN CARIBBEAN IS FORECAST TO BUILD...WHICH SHOULD
CAUSE NATE TO MOVE MORE TOWARD THE NORTH...EVENTUALLY BENDING TO
THE LEFT AS THE CYCLONE COMES UNDER THE INFLUENCE OF THE MEXICAN
RIDGE.  THERE IS A FAIR AMOUNT OF SPREAD IN THE GUIDANCE DUE TO THE
STRENGTH OF THE RIDGES...AND THE OFFICIAL FORECAST IS CLOSEST TO
THE HFIP MODEL CONSENSUS...A BIT SOUTH OF THE ECMWF MODEL.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/2100Z 20.2N  92.4W   40 KT  45 MPH
 12H  08/0600Z 20.0N  92.1W   45 KT  50 MPH
 24H  08/1800Z 20.1N  91.9W   50 KT  60 MPH
 36H  09/0600Z 20.4N  92.1W   60 KT  70 MPH
 48H  09/1800Z 21.0N  92.5W   65 KT  75 MPH
 72H  10/1800Z 22.5N  93.5W   70 KT  80 MPH
 96H  11/1800Z 23.0N  95.0W   75 KT  85 MPH
120H  12/1800Z 23.0N  96.5W   75 KT  85 MPH
 
$$
FORECASTER BLAKE/ZELINSKY
 

WTNT45 KNHC 080250
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 PM CDT WED SEP 07 2011

SATELLITE IMAGERY...CONVENTIONAL AND MICROWAVE...SHOWS LITTLE CHANGE
IN EITHER THE POSITION OR THE ORGANIZATION OF NATE DURING THE PAST
SEVERAL HOURS.  THE LOW-LEVEL CENTER REMAINS EXPOSED ABOUT 60 N MI
NORTHEAST OF THE MAIN CONVECTIVE AREA...AND OVERALL THE SYSTEM
RETAINS A SOMEWHAT BAROCLINIC APPEARANCE DUE TO ITS POSITION NEAR
THE SOUTHWESTERN END OF A FRONTAL ZONE.  SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB ARE BELOW TROPICAL STORM STRENGTH. 
HOWEVER...A SHIP REPORTED 40 KT WINDS SOUTHEAST OF THE CENTER AT
0000 UTC....AND THAT IS THE BASIS FOR THE INITIAL INTENSITY.

THE INITIAL MOTION IS A VERY UNCERTAIN 090/2...AND IT IS LIKELY THAT
FOR THE NEXT DAY OR SO REFORMATIONS OF THE CENTER WILL CAUSE LARGER
CHANGES IN POSITION THAN THE ACTUAL MOTION OF THE CYCLONE. AFTER
THAT TIME...RISING PRESSURES TO THE NORTH AND NORTHEAST SHOULD
CAUSE NATE TO BEGIN A SLOW NORTHWESTWARD MOTION...WHICH MOST OF THE
GUIDANCE SHOWS NATE TURNING WESTWARD BY 120 HOURS. THERE REMAINS A
LOT OF NORTH-TO-SOUTH SPREAD IN THE TRACK GUIDANCE...AND THE
CANADIAN MODEL IS A MAJOR OUTLIER IN SHOWING A MOTION TOWARD THE
NORTHERN GULF COAST. THAT SOLUTION IS DISCOUNTED FOR THIS FORECAST.
THE FORECAST TRACK IS SIMILAR TO THE PREVIOUS ONE AND SHOWS THE
CENTER OF NATE REMAINING OVER THE BAY OF CAMPECHE FOR THE NEXT FIVE
DAYS.

NATE IS FORECAST TO REMAIN IN AN AREA OF LIGHT VERTICAL WIND SHEAR
FOR THE NEXT 36-48 HOURS...AND THE INTENSITY GUIDANCE RESPONDS TO
THIS LOW SHEAR AND THE WARM UNDERLYING WATERS BY FORECASTING
STRENGTHENING.  HOWEVER...THERE IS ABUNDANT DRY AIR TO THE
NORTHWEST OF NATE WHICH COULD SLOW THE RATE OF STRENGTHENING IF THE
STORM INGESTS IT...AND THE CURRENT STORM STRUCTURE IS NOT FAVORABLE
FOR RAPID STRENGTHENING.  BASED ON THIS...THE INTENSITY FORECAST
SHOWS GRADUAL STRENGTHENING INTO A HURRICANE DURING THAT TIME. 
AFTER 48 HOURS...THE GLOBAL MODELS ARE DIVIDED ON HOW MUCH WIND
SHEAR NATE MIGHT ENCOUNTER...WITH THE ECMWF FORECASTING A MORE
FAVORABLE ENVIRONMENT THAN THE OTHER MODELS.  DUE TO THE
UNCERTAINTY...THE NEW INTENSITY FORECAST IS UNCHANGED FROM THE
PREVIOUS ADVISORY.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0300Z 20.4N  92.5W   40 KT  45 MPH
 12H  08/1200Z 20.3N  92.2W   45 KT  50 MPH
 24H  09/0000Z 20.5N  92.0W   50 KT  60 MPH
 36H  09/1200Z 21.1N  92.2W   55 KT  65 MPH
 48H  10/0000Z 21.7N  92.8W   65 KT  75 MPH
 72H  11/0000Z 23.0N  94.0W   70 KT  80 MPH
 96H  12/0000Z 23.5N  95.5W   75 KT  85 MPH
120H  13/0000Z 23.5N  97.0W   75 KT  85 MPH
 
$$
FORECASTER BEVEN
 

WTNT45 KNHC 080847
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 AM CDT THU SEP 08 2011
 
NATE APPEARS TO BE SLOWLY BECOMING BETTER ORGANIZED. A CURVED BAND 
NOW WRAPS AROUND THE NORTHWEST SEMICIRCLE. HOWEVER...CONVENTIONAL
AND MICROWAVE SATELLITE IMAGERY THAT THE MAIN CONVECTIVE MASS IS
CONFINED TO THE SOUTHWEST QUADRANT...WITH THE LOW-LEVEL CENTER
STILL DISPLACED ABOUT 60 N MI NORTHEAST OF IT. DVORAK
T-NUMBERS FROM TAFB AND SAB HAVE INCREASED SOME SINCE
0000 UTC BUT REMAIN BELOW TROPICAL STORM STRENGTH. A SHIP LOCATED
ABOUT 50 N MI SOUTHEAST OF THE CENTER REPORTED 45 KT WIND AT 0300
UTC...BUT THIS OBSERVATION WAS JUDGED TO BE A BIT HIGH. BASED UPON
THESE DATA...THE INITIAL INTENSITY ESTIMATE IS HELD AT 40 KT.
 
THE CENTER OF NATE APPEARS TO HAVE NOT MOVED MUCH RECENTLY.
HOWEVER...SINCE THE CENTER REMAINS HARD TO LOCATE...THE INITIAL
MOTION ESTIMATE OF 090/02 REMAINS AS UNCERTAIN AS IT WAS EARLIER.
THE CYCLONE REMAINS IN A WEAK STEERING FLOW IN BETWEEN MID-LEVEL
RIDGES OVER THE NORTHERN CARIBBEAN AND MEXICO...WITH SHOULD ONLY
ALLOW A SLOW AND ERRATIC MOTION FOR THE NEXT DAY OR SO. AFTER
THAT...A SLOW NORTHWESTWARD TO NORTHWESTWARD MOTION SHOULD COMMENCE
UNTIL ABOUT 72 HOURS AS THE MID-LEVEL RIDGE TO THE EAST OF NATE
LIFTS NORTHWARD.  LATER IN THE FORECAST PERIOD...GLOBAL MODELS SHOW
THE MEXICAN RIDGE BUILDING EASTWARD AND INDUCING A GENERALLY
WESTWARD TRACK.  WHILE THERE CONTINUES TO BE A FAIR AMOUNT OF
NORTH-TO-SOUTH SPREAD IN THE TRACK GUIDANCE THIS CYCLE....THE MORE
RELIABLE GFS/ECWMF REMAIN THE MOST CONSISTENT. ONLY MINOR CHANGES
WERE MADE TO THE PREVIOUS TRACK FORECAST...WITH THE NEW TRACK IN
BEST AGREEMENT WITH THE GFS/ECMWF SOLUTIONS.
  
THE INTENSITY FORECAST FOR NATE IS CHALLENGING.  WHILE THE CYCLONE
IS LOCATED IN A DIFFLUENT UPPER-LEVEL WIND ENVIRONMENT...WATER VAPOR
IMAGERY SHOWS A TONGUE OF EXCEPTIONALLY DRY AIR NEAR AND NORTH OF
NATE. THIS...AND THE RELATIVE LACK OF CONVECTIVE ORGANIZATION...
WOULD ARGUE AGAINST ANY SIGNIFICANT INTENSIFICATION IN THE SHORT
TERM.  LATER IN THE FORECAST PERIOD...SHIPS GUIDANCE STILL
INDICATES THE PRESENCE OF A RELATIVELY DRY LOW- TO MID-LEVEL AIR
MASS AND A SUDDEN INCREASE IN SOUTHWESTERLY SHEAR ASSOCIATED WITH A
TROUGH OVER THE SOUTHEASTERN UNITED STATES.  THIS SUGGESTS THAT THE
STRONGER DYNAMICAL GUIDANCE...E.G. HWRF...MAY BE IN DOUBT. THE
OFFICIAL NHC OFFICIAL IS SIMILAR TO THE PREVIOUS ONE AND PUTS MORE
WEIGHT ON THE STATISTICAL INTENSITY MODEL OUTPUT. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 20.4N  92.4W   40 KT  45 MPH
 12H  08/1800Z 20.4N  92.2W   45 KT  50 MPH
 24H  09/0600Z 20.6N  92.2W   50 KT  60 MPH
 36H  09/1800Z 21.2N  92.5W   55 KT  65 MPH
 48H  10/0600Z 21.8N  93.0W   60 KT  70 MPH
 72H  11/0600Z 22.7N  94.2W   65 KT  75 MPH
 96H  12/0600Z 23.0N  95.5W   70 KT  80 MPH
120H  13/0600Z 23.0N  97.0W   70 KT  80 MPH
 
$$
FORECASTER KIMBERLAIN/PASCH
 

WTNT45 KNHC 081458
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 AM CDT THU SEP 08 2011
 
EARLY MORNING VISIBLE SATELLITE IMAGES SHOW A MORE ORGANIZED
TROPICAL CYCLONE THAN WAS SEEN LATE YESTERDAY AFTERNOON.  NATE HAS
THE APPEARANCE OF A SHEARED TROPICAL CYCLONE WITH THE CENTER
LOCATED NEAR THE NORTHEASTERN TIP OF THE MAIN CONVECTIVE MASS. THE
INITIAL WIND SPEED IS RAISED TO 45 KT...BASED ON A SHIP OBSERVATION
OF 40 KT TO THE SOUTHEAST OF THE CENTER...AND RECENT STRONGER WIND
REPORTS FROM ELEVATED PEMEX OIL RIGS IN THE BAY OF CAMPECHE.  AN
AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO
INVESTIGATE NATE THIS AFTERNOON AND SHOULD PROVIDE A BETTER
ASSESSMENT OF THE INTENSITY.
 
NATE HAS NOT MOVED MUCH OVERNIGHT OR THIS MORNING...ALTHOUGH THE
LATEST SATELLITE AND MICROWAVE IMAGERY SUGGESTS THAT THE CENTER IS
A LITTLE SOUTH OF THE EARLIER ESTIMATES. THE CYCLONE IS FORECAST TO
REMAIN IN A WEAK STEERING PATTERN BETWEEN MID-LEVEL RIDGES OVER
MEXICO AND THE NORTHERN CARIBBEAN DURING THE NEXT 12-24 HOURS. IN A
DAY OR SO...NATE IS EXPECTED TO MOVE SLOWLY NORTHWARD AROUND THE
WESTERN PERIPHERY OF THE CARIBBEAN RIDGE. AFTER 36-48 HOURS...THE
MODEL SPREAD BECOMES INCREASINGLY LARGE...AS SUBTLE DIFFERENCES IN
THE STRENGTH AND ORIENTATION OF A MID/UPPER-LEVEL LOW AND TROUGH
EXTENDING FROM THE OHIO VALLEY SOUTHWESTWARD HAVE SIGNIFICANT
IMPLICATIONS ON THE FUTURE TRACK OF THE CYCLONE. THE LATEST GFS AND
GFDL MODELS...WHICH SHOW A SLIGHTLY DEEPER TROUGH...MOVE NATE
NORTHWARD TOWARD THE NORTHERN GULF COAST. THE ECMWF AND NOGAPS
MODELS DEPICT A WEAKER TROUGH THAT DOES NOT CAPTURE NATE AND ALLOWS
IT TURN TURN WESTWARD TOWARD MEXICO TO THE SOUTH OF A BUILDING
RIDGE...ALTHOUGH IT SHOULD BE NOTED THAT THERE IS CONSIDERABLE
SPREAD AMONG THE ECMWF ENSEMBLE MEMBERS. THE OFFICIAL FORECAST HAS
BEEN SHIFTED TO THE RIGHT AND LIES BETWEEN THESE TWO VIABLE
SCENARIOS BUT HAS NOT BEEN SHIFTED AS FAR AS THE TVCA CONSENSUS.
THE NOAA G-IV AIRCRAFT IS SCHEDULED TO PERFORM A SYNOPTIC
SURVEILLANCE MISSION LATER TODAY...WHICH WILL HOPEFULLY HELP REDUCE
THE SPREAD IN THE TRACK GUIDANCE TONIGHT.
 
NATE IS CURRENTLY LOCATED IN AN ENVIRONMENT OF LIGHT TO MODERATE
NORTHEASTERLY SHEAR.  THE SHEAR IS FORECAST TO LESSEN DURING THE
NEXT DAY OR SO...WHICH SHOULD ALLOW FOR GRADUAL STRENGTHENING.
LATER IN THE FORECAST PERIOD...SOUTHWESTERLY SHEAR IS EXPECTED TO
INCREASE AND ALONG WITH DRIER LOW- TO MID-LEVEL AIR...IS FORECAST TO
SLOW THE INTENSIFICATION PROCESS. THE UPDATED INTENSITY FORECAST IS
SIMILAR TO THE PREVIOUS ADVISORY AND IS IN GOOD AGREEMENT WITH THE
SHIPS/LGEM GUIDANCE.

 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 20.0N  92.4W   45 KT  50 MPH
 12H  09/0000Z 20.4N  92.2W   55 KT  65 MPH
 24H  09/1200Z 21.0N  92.2W   55 KT  65 MPH
 36H  10/0000Z 21.8N  92.7W   60 KT  70 MPH
 48H  10/1200Z 22.5N  93.2W   65 KT  75 MPH
 72H  11/1200Z 23.1N  93.8W   70 KT  80 MPH
 96H  12/1200Z 23.6N  94.4W   70 KT  80 MPH
120H  13/1200Z 24.0N  95.0W   70 KT  80 MPH
 
$$
FORECASTER BROWN
 

WTNT45 KNHC 082058
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 PM CDT THU SEP 08 2011
 
ALTHOUGH THE SATELLITE APPEARANCE OF NATE HAS NOT CHANGED MUCH
THIS AFTERNOON...AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT
HAS REPORTED PEAK 1000-FT FLIGHT-LEVEL WINDS OF 81 KT AND BELIEVABLE
SFMR SURFACE WINDS OF AROUND 60 KT.  BASED ON THESE DATA...THE
INITIAL INTENSITY IS INCREASED TO 60 KT.  THE CENTER REMAINS NEAR
THE NORTHEASTERN EDGE OF THE DEEP CONVECTION DUE TO LIGHT TO
MODERATE NORTHEASTERLY SHEAR.  THE SHEAR IS EXPECTED TO WEAKEN
DURING THE NEXT 12-24 HOURS...WHICH SHOULD PLACE NATE IN A 
FAVORABLE ENVIRONMENT FOR STRENGTHENING DURING THE NEXT FEW DAYS.
THE UPDATED INTENSITY FORECAST IS ABOVE THE PREVIOUS ADVISORY AND IS
A BLEND OF THE SHIPS/LGEM GUIDANCE.
 
FIXES FROM THE AIRCRAFT SHOW THAT NATE HAS MOVED SLOWLY
SOUTH-SOUTHEASTWARD DURING THE PAST 24 HOURS.  THE INITIAL MOTION
ESTIMATE IS 160/2 KT.  THE OVERALL FORECAST REASONING HAS CHANGED
LITTLE SINCE THIS MORNING.  NATE WILL REMAIN IN WEAK STEERING
CURRENTS DURING THE NEXT DAY OR SO...THEN IT SHOULD BEGIN MOVING
NORTHWARD AROUND THE WESTERN SIDE OF THE CARIBBEAN RIDGE.  AFTER
36-48 HOURS...THERE REMAINS A VERY LARGE SPREAD IN THE GUIDANCE...
HOWEVER THE MODELS HAVE GENERALLY SHIFTED WESTWARD.  THE GFS IS
ALONG THE EASTERN EDGE OF THE ENVELOPE AND SHOWS A SLOW NORTHWARD TO
NORTH-NORTHWESTWARD MOTION OVER THE CENTRAL GULF OF MEXICO.  MOST OF
THE REMAINDER OF THE TRACK MODELS MOVE NATE MORE WESTWARD TOWARD
MEXICO.  THE OFFICIAL FORECAST HAS BEEN SHIFTED TO THE LEFT...BUT
NOT NEARLY AS FAR WEST AS THE MULTI-MODEL CONSENSUS...OUT OF RESPECT
FOR THE GFS AND THE EARLIER ECMWF ENSEMBLE MEMBERS.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 19.7N  92.3W   60 KT  70 MPH
 12H  09/0600Z 19.7N  92.2W   65 KT  75 MPH
 24H  09/1800Z 20.2N  92.3W   70 KT  80 MPH
 36H  10/0600Z 20.9N  92.8W   75 KT  85 MPH
 48H  10/1800Z 21.6N  93.3W   80 KT  90 MPH
 72H  11/1800Z 22.5N  94.0W   85 KT 100 MPH
 96H  12/1800Z 23.0N  94.5W   85 KT 100 MPH
120H  13/1800Z 23.5N  95.0W   85 KT 100 MPH
 
$$
FORECASTER BROWN
 

WTNT45 KNHC 090251
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 PM CDT THU SEP 08 2011
 
DATA FROM THE MEXICAN RADAR STATION AT SABANCUY INDICATE THAT NATE
HAS WELL-DEFINED CURVED BANDS AND OCCASIONALLY IS TRYING TO WRAP UP
AN EYE FEATURE.  THIS SIGNATURE IS NOT APPARENT ON SATELLITE
IMAGERY...WITH THE CONVENTIONAL INFRARED SUGGESTING A WEAKER
SYSTEM.  THERE IS NOT MUCH EVIDENCE THAT NATE HAS STRENGTHENED
SINCE THE AIR FORCE RESERVE RECONNAISSANCE PLANE LEFT THIS
EVENING...SO THE INITIAL WINDS WILL REMAIN 60 KT.
 
MEXICAN RADAR DATA SHOW THAT NATE REMAINS STATIONARY...AND IT IS
LIKELY TO MOVE LITTLE TONIGHT WHILE IT IS CAUGHT IN AN AREA OF VERY
LIGHT STEERING CURRENTS. A RIDGE OVER THE WESTERN CARIBBEAN SEA IS
FORECAST TO BUILD TOMORROW...WHICH SHOULD CAUSE NATE TO MOVE MORE
TOWARD THE NORTH AND NORTH-NORTHWEST. THERE HAS BEEN A LARGE MODEL
CHANGE FROM SIX HOURS AGO...WITH THE GFS/GFDL/HWRF MODELS NOW
HAVING A GENERAL WESTWARD TRACK TOWARD MAINLAND MEXICO DUE TO THE
CYCLONE BEING TRAPPED BENEATH A NARROW RIDGE OVER THE NORTHERN GULF
OF MEXICO. NATE IS FARTHER SOUTH THAN EXPECTED YESTERDAY...SO THE
LIKELIHOOD OF A MORE POLEWARD TRACK AHEAD OF THE NEXT TROUGH OVER
THE CENTRAL UNITED STATES HAS DIMINISHED. THUS THE NHC FORECAST IS
SHIFTED WELL TO THE LEFT AT THIS TIME...BUT BASICALLY ALL RELIABLE
MODELS ARE STILL FARTHER TO THE SOUTH. IF CURRENT TRENDS
CONTINUE...THE FORECAST WOULD HAVE TO BE ADJUSTED SOUTHWESTWARD AT A
LATER TIME.
 
EXCEPT FOR SOME DRY AIR NORTHWEST OF THE CENTER...THE ATMOSPHERIC
AND OCEANIC ENVIRONMENT APPEARS FAVORABLE FOR AT LEAST STEADY
INTENSIFICATION DURING THE NEXT COUPLE OF DAYS. MOST OF THE GLOBAL
MODELS ARE BUILDING AN UPPER ANTICYCLONE OVER NATE... WHICH IS
USUALLY QUITE FAVORABLE FOR STRENGTHENING. IT IS A LITTLE
SURPRISING THAT NONE OF THE MODELS SHOW NATE BECOMING A MAJOR
HURRICANE WITH THIS TYPE OF UPPER-AIR ENVIRONMENT. GIVEN THE
PROXIMITY TO LAND AND THE DRY AIR LURKING NEARBY...IT IS PROBABLY
BEST NOT TO MAKE TOO LARGE OF A CHANGE TO THE INTENSITY FORECAST AT
THIS TIME.  THEREFORE...THE NEW NHC FORECAST IS JUST A BIT HIGHER
THAN THE PREVIOUS ONE...AT THE UPPER END OF THE GUIDANCE ENVELOPE
AND NEAREST THE LGEM MODEL.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 19.7N  92.2W   60 KT  70 MPH
 12H  09/1200Z 20.0N  92.3W   65 KT  75 MPH
 24H  10/0000Z 20.5N  92.7W   75 KT  85 MPH
 36H  10/1200Z 21.2N  93.5W   80 KT  90 MPH
 48H  11/0000Z 21.7N  94.4W   90 KT 105 MPH
 72H  12/0000Z 22.0N  96.5W   85 KT 100 MPH
 96H  13/0000Z 21.5N  99.5W   25 KT  30 MPH...INLAND
120H  14/0000Z...DISSIPATED
 
$$
FORECASTER BLAKE
 

WTNT45 KNHC 090855
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 AM CDT FRI SEP 09 2011
 
NATE HAS SEEMINGLY WEAKENED A LITTLE OVERNIGHT. DEEP CONVECTION HAS
DIMINISHED SIGNIFICANTLY OVER THE PAST 6-12 HOURS...ALTHOUGH THERE
HAS BEEN A MODEST COMEBACK OVER THE LAST HOUR OR TWO. THE HIGHEST
SFMR WINDS REPORTED FROM THE AIRCRAFT INVESTIGATING NATE AROUND 06Z
WERE 47 KT IN THE SOUTHEAST QUADRANT...AN AREA WHERE 60 KT SFMR
WINDS WERE FOUND YESTERDAY AFTERNOON. THE MINIMUM PRESSURE WAS ALSO
UP...TO 998 MB. BASED ON THESE DATA...THE ESTIMATED INTENSITY IS
LOWERED TO 55 KT. AN ASCAT PASS ALSO SUGGESTS THE WIND RADII HAVE
CONTRACTED.
 
RADAR AND RECONNAISSANCE DATA INDICATE THAT NATE IS STILL
ESSENTIALLY STATIONARY...AND THE GUIDANCE IS COMING INTO STRONGER
AGREEMENT THAT NATE WILL NOT BE ABLE TO MAKE MUCH NORTHWARD
PROGRESS.  BOTH THE GFS AND ECMWF SHOW A NARROW RIDGE DEVELOPING TO
THE NORTH OF THE CYCLONE THAT IS EXPECTED TO TURN NATE WESTWARD
OVER THE NEXT TWO TO THREE DAYS.  IN FACT...THERE IS A FAIR AMOUNT
OF GUIDANCE NOW THAT TAKES NATE WESTWARD AND THEN SOUTHWESTWARD
ACROSS THE BAY OF CAMPECHE.  THE SOUTHERNMOST MODEL IS THE HFIP
COAMPS-TC...WHILE THE NORTHERN EDGE OF THE GUIDANCE ENVELOPE IS
DEFINED BY THE ECMWF AND UKMET.  THE PRESENT MODEL SUITE REQUIRES A
SOUTHWARD ADJUSTMENT IN THE OFFICIAL FORECAST...WHICH IS IN GOOD
AGREEMENT WITH THE ECMWF BUT STILL NORTH OF THE CONSENSUS MODELS.
 
ALTHOUGH NATE HAS WEAKENED A LITTLE...THE ENVIRONMENT IS STILL
EXPECTED TO BE FAVORABLE FOR STRENGTHENING OVER THE NEXT
TWO TO THREE DAYS. THE GFS AND ECMWF BOTH SHOW A DIFLUENT AND
ANTICYCLONIC FLOW ALOFT...AND ONCE NATE BEGINS TO MOVE IT WILL HAVE
A DEEPER RESERVOIR OF VERY WARM WATER UNDERNEATH. THE DRY AIR IN
THE WESTERN GULF APPEARS TO BE THE PRIMARY INHIBITING FACTOR. THE
OFFICIAL FORECAST IS NEAR THE UPPER END OF THE TRADITIONAL
GUIDANCE...CLOSE TO THE LGEM STATISTICAL MODEL...THE HWRF...AND
GFDL. AMONG THE HFIP MODELS...WHICH AS A GROUP PERFORMED VERY WELL
DURING IRENE...THE UNIVERSITY OF WISCONSIN UWN8 IS MOST
AGRESSIVE...BRINGING NATE TO ABOUT 90 KT...WHILE THE COAMPS-TC AND
AHW ARE 15-25 KT LOWER.
 
A HURRICANE WATCH WILL LIKELY BE REQUIRED FOR A PORTION OF THE
WESTERN GULF COAST OF MEXICO LATER TODAY.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0900Z 19.9N  92.3W   55 KT  65 MPH
 12H  09/1800Z 20.3N  92.5W   60 KT  70 MPH
 24H  10/0600Z 20.7N  93.1W   65 KT  75 MPH
 36H  10/1800Z 20.8N  94.0W   75 KT  85 MPH
 48H  11/0600Z 20.9N  95.0W   85 KT 100 MPH
 72H  12/0600Z 20.5N  97.5W   80 KT  90 MPH...INLAND
 96H  13/0600Z 20.0N 100.5W   25 KT  30 MPH...INLAND
120H  14/0600Z...DISSIPATED
 
$$
FORECASTER FRANKLIN
 

WTNT45 KNHC 091440
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 AM CDT FRI SEP 09 2011

EARLY MORNING VISIBLE IMAGERY SHOWS THAT NATE HAS A WELL-ORGANIZED
CLOUD PATTERN...HOWEVER DRY AIR OVER THE WESTERN SEMICIRCLE
CONTINUES TO SUPPRESS DEEP CONVECTION IN THAT PORTION OF THE
CIRCULATION AND THE INFRARED PRESENTATION REMAINS UNIMPRESSIVE. THE
INITIAL INTENSITY IS HELD AT 55 KT BASED ON A DVORAK CI-NUMBER OF
3.5 FROM TAFB AT 12Z. AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT WILL BE INVESTIGATING NATE LATER TODAY TO PROVIDE
INFORMATION ON THE STRUCTURE AND INTENSITY OF THE CYCLONE. 

THE ENVIRONMENT IN TERMS OF SSTS AND UPPER-LEVEL WINDS APPEARS
FAVORABLE FOR INTENSIFICATION. HOWEVER...ACCORDING THE SHIPS MODEL
OUTPUT...MID-LEVEL DRY AIR WILL REMAIN A LIMITING FACTOR. OVERALL
THE INTENSITY GUIDANCE HAS TRENDED A LITTLE LOWER THIS CYCLE...AND
THE OFFICIAL FORECAST HAS BEEN NUDGED DOWNWARD A BIT...BUT STILL
SHOWS NATE REACHING HURRICANE STRENGTH IN 24 HOURS. NOTE THAT SOME 
ADDITIONAL STRENGTHENING IS POSSIBLE BETWEEN THE 48-HOUR FORECAST
POINT AND LANDFALL...WHICH SHOULD OCCUR BY 72 HOURS. THE NHC
FORECAST IS CLOSE TO OR A BIT ABOVE THE LGEM MODEL THROUGH THE
PERIOD. 

BASED ON SATELLITE IMAGERY...NATE FINALLY APPEARS TO BE MOVING
SLOWLY NORTHWEST AT AROUND 3 KT AS THE RIDGE TO THE NORTH HAS
WEAKENED A LITTLE BIT. HOWEVER...THE MODEL GUIDANCE IS IN GOOD
AGREEMENT ON THE RIDGE RESTRENGTHENING NORTH OF NATE IN THE NEXT DAY
OR SO. BY 36 HOURS A TURN TOWARD THE WEST IS EXPECTED...WITH A
MOTION SOUTH OF DUE WEST POSSIBLE BEFORE LANDFALL. AFTER
LANDFALL...THE CYCLONE SHOULD WEAKEN QUICKLY AND DISSIPATE BEFORE
96 HOURS. HOWEVER A 96-HOUR POINT WAS INCLUDED TO SHOW THE SYSTEM
WEAKENING BELOW TROPICAL STORM INTENSITY BEFORE DISSIPATION. THE
NHC TRACK FORECAST IS AN UPDATE OF THE PREVIOUS ONE AND LIES
ROUGHLY BETWEEN THE GFS AND ECMWF IN TERMS OF HEADING AND FORWARD
SPEED. 
 
GIVEN THE FORECAST TIMING OF THE APPROACH OF TROPICAL STORM
CONDITIONS TO THE COAST...A HURRICANE WATCH IS REQUIRED FOR A
PORTION OF THE WESTERN GULF COAST OF MEXICO AT THIS TIME. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 20.3N  92.6W   55 KT  65 MPH
 12H  10/0000Z 20.6N  93.0W   60 KT  70 MPH
 24H  10/1200Z 20.8N  93.8W   65 KT  75 MPH
 36H  11/0000Z 20.9N  94.8W   70 KT  80 MPH
 48H  11/1200Z 20.8N  95.9W   80 KT  90 MPH
 72H  12/1200Z 20.5N  98.5W   50 KT  60 MPH...INLAND
 96H  13/1200Z 20.0N 101.0W   25 KT  30 MPH...INLAND
120H  14/1200Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

WTNT45 KNHC 092037
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 PM CDT FRI SEP 09 2011
 
THE HURRICANE HUNTER AIRCRAFT INVESTIGATING NATE THIS AFTERNOON
FOUND A PEAK 850-MB FLIGHT-LEVEL WIND OF 55 KT AND PEAK SFMR VALUES
OF 40-45 KT. BASED ON THIS...THE INITIAL INTENSITY IS SET AT 45 KT
FOR THIS ADVISORY. WHILE NATE CONTINUES TO HAVE AN IMPRESSIVE
BANDED STRUCTURE IN VISIBLE IMAGERY...DEEP CONVECTION IS
LACKING...BUT HAS MADE A BIT OF A COMEBACK IN THE PAST HOUR OR TWO
IN RAINBANDS WELL EAST AND WEST OF THE CENTER. THE SHIPS MODEL
ANALYSIS CONTINUES TO SHOW RELATIVELY DRY AIR IN THE MID-LEVELS AND
AND A LACK OF INSTABILITY IN THE PROFILE. HOWEVER...GIVEN THE VERY
WARM SSTS OVER THE SOUTHWESTERN GULF OF MEXICO...NATE SHOULD BE
ABLE TO INTENSIFY SOME IF CAN RE-ESTABLISH CONVECTION NEAR THE
CENTER. GIVEN THE RECENT WEAKENING TREND THE STATISTICAL MODELS
SHOW ONLY GRADUAL STRENGTHENING UNTIL LANDFALL WHILE THE DYNAMICAL
MODELS ARE A LITTLE MORE AGGRESSIVE...BUT STILL LOWER THAN THE LAST
CYCLE. THE OFFICIAL FORECAST HAS BEEN ADJUSTED DOWNWARD BY ABOUT 10
KT COMPARED TO THE PREVIOUS PACKAGE BUT IS ABOVE MOST OF THE
GUIDANCE. AFTER LANDFALL NATE SHOULD QUICKLY WEAKEN OVER THE HIGH
TERRAIN AND DISSIPATE BY 96 HOURS.
 
AFTER APPEARING TO MOVE WEST-NORTHWESTWARD EARLIER TODAY...THE
LATEST AIRCRAFT FIXES SUGGEST NATE HAS BEEN NEARLY STATIONARY. 
MODEL GUIDANCE CONTINUES TO SUGGEST THAT A MID-LEVEL RIDGE WILL
REBUILD TO THE NORTH OF NATE OVER THE NEXT DAY OR TWO...WHICH
SHOULD GET NATE MOVING AGAIN. THE GFS...HWRF...AND GFDL MODELS NOW
SHOW MORE OF A TURN TOWARD THE WEST-SOUTHWEST AS NATE APPROACHES
THE COAST...WHILE THE ECMWF AND UKMET SHOW A MORE WESTWARD TRACK.
THE OFFICIAL FORECAST HAS BEEN SHIFTED SOUTHWARD FOR THIS CYCLE BUT
STILL LIES NORTH OF THE MULTI-MODEL CONSENSUS...SHOWING A SLOW
WESTWARD MOTION FOR 12 TO 24 HOURS AND A TURN SOUTH OF DUE WEST
PRIOR TO LANDFALL. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/2100Z 20.0N  92.8W   45 KT  50 MPH
 12H  10/0600Z 20.2N  93.4W   50 KT  60 MPH
 24H  10/1800Z 20.2N  94.1W   60 KT  70 MPH
 36H  11/0600Z 20.1N  95.0W   65 KT  75 MPH
 48H  11/1800Z 20.0N  96.0W   70 KT  80 MPH
 72H  12/1800Z 19.5N  98.5W   35 KT  40 MPH...INLAND
 96H  13/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

WTNT45 KNHC 100251
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 PM CDT FRI SEP 09 2011
 
THERE HAS NOT BEEN A LOT OF CHANGE WITH THE STRUCTURE OF NATE DURING
THE PAST SEVERAL HOURS.  ALTHOUGH THE CYCLONE CONTINUES TO HAVE
CURVED BANDING FEATURES ON THE SABANCUY RADAR...THE ASSOCIATED
CONVECTION IS NOT VERY DEEP AND THE CENTER HAS A HOLLOW APPEARANCE
ON INFRARED SATELLITE PICTURES.  THE INITIAL WINDS ARE KEPT AT 45
KT...AND AN AIR FORCE RESERVE PLANE WILL BE IN THE AREA AROUND 0600
UTC TO OBTAIN A BETTER ESTIMATE.
 
SATELLITE IMAGES SUGGEST THAT NATE HAS MOVED A LITTLE BIT TONIGHT...
WITH AN INITIAL MOTION ESTIMATE OF 280/2.  A RIDGE IS FORECAST TO
BUILD TO THE NORTH OF NATE...CAUSING THE STORM TO ACCELERATE TO THE
WEST TOMORROW.  A FAIR NUMBER OF THE MODELS ALSO SUGGEST A
SOUTH-OF-WEST MOTION COULD OCCUR AS THE CYCLONE APPROACHES
LAND...WHICH IS NOT UNCOMMON IN THAT PART OF THE SOUTHWESTERN GULF
OF MEXICO.  THE NEW NHC TRACK IS ADJUSTED A SMIDGE TO THE SOUTH AND
IS A LITTLE FASTER THAN THE PREVIOUS FORECAST...THOUGH IT REMAINS
TO THE NORTH OF THE MODEL CONSENSUS.
 
NATE IS YET ANOTHER EXAMPLE OF THE LIMITATIONS OF INTENSITY
FORECASTING.  DESPITE A SEEMINGLY FAVORABLE ENVIRONMENT AND ALL
MODELS SUGGESTING STRENGTHENING...THE STORM HAS LOST ORGANIZATION
SINCE THIS TIME YESTERDAY.  ONE REASON COULD BE THAT THE STATIONARY
SYSTEM HAS UPWELLED COOLER WATERS...CAUSING A LACK OF INSTABILITY
NEAR THE CENTER...WHICH SEEMS LIKE A GOOD POSSIBILITY GIVEN THE
DEARTH OF CENTRAL CONVECTION.   DRY AIR ALOFT ALSO MAY HAVE PLAYED
A ROLE...THOUGH LITTLE EVIDENCE CAN BE SEEN IN SSM/IS VAPOR IMAGES. 
IN ANY CASE...NATE IS FORECAST TO MOVE A LITTLE FASTER OVERNIGHT...
WHICH SHOULD BRING THE STORM OVER WARMER WATERS.  WITH LIGHT SHEAR
CONDITIONS LIKELY...SOME INTENSIFICATION IS THE BEST BET.  THE
MODELS DO SHOW STRENGTHENING...THOUGH THEY HAVE BACKED OFF OF THE
PEAK INTENSITY AND ALMOST ALL OF THEM KEEP NATE BELOW HURRICANE
STRENGTH BEFORE LANDFALL.  THIS REDUCTION SEEMS REASONABLE GIVEN
THAT NATE IS FORECAST TO SPEND LESS TIME OVER WATER.  THUS THE
INTENSITY FORECAST IS DECREASED FROM THE PREVIOUS ADVISORY...THOUGH
IT REMAINS ABOVE THE INTENSITY CONSENSUS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0300Z 20.1N  93.2W   45 KT  50 MPH
 12H  10/1200Z 20.2N  93.8W   45 KT  50 MPH
 24H  11/0000Z 20.1N  94.7W   55 KT  65 MPH
 36H  11/1200Z 20.0N  95.5W   60 KT  70 MPH
 48H  12/0000Z 19.8N  96.8W   55 KT  65 MPH...INLAND
 72H  13/0000Z 19.5N  99.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  14/0000Z...DISSIPATED
 
$$
FORECASTER BLAKE/BEVEN
 

WTNT45 KNHC 100846
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 AM CDT SAT SEP 10 2011
 
AN AIR FORCE RECONNAISSANCE PLANE INVESTIGATING NATE THIS MORNING
FOUND A MAXIMUM FLIGHT-LEVEL WIND OF 49 KT AND SURFACE WINDS NEAR
40 KT. DROPSONDE DATA ALSO SUGGEST THAT THE MINIMUM PRESSURE IS UP
A LITTLE TO 1000 MB. THESE DATA SUGGEST THAT NATE MAY HAVE WEAKENED
SLIGHTLY...BUT SINCE THE PLANE WAS UNABLE TO SAMPLE THE
SOUTHEASTERN SIDE OF THE TROPICAL STORM...I PREFER TO HOLD THE
INITIAL WIND SPEED AT 45 KT.   
 
SATELLITE AND AIRCRAFT FIXES SUGGEST THAT NATE IS NOW ON A MORE
STEADY WESTWARD PATH...WITH THE LATEST INITIAL MOTION ESTIMATE OF
270/4.  A BUILDING LOW- TO MID-LEVEL RIDGE TO THE NORTH OF THE STORM
SHOULD STEER NATE WESTWARD OR WEST-SOUTHWESTWARD WITH A SLIGHT
INCREASE IN FORWARD SPEED THROUGH LANDFALL OVER SOUTHERN
MEXICO...WHICH IS NOW FORECAST TO OCCUR IN ABOUT 36 HOURS. THE
OFFICIAL TRACK FORECAST IS FASTER AND A LITTLE TO THE SOUTH OF THE
PREVIOUS ONE...AND IS NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.
 
AS MENTIONED IN THE PREVIOUS ADVISORY...THE WEAKENING OR LACK OF
STRENGTHENING OF NATE DURING THE PAST 24 HOURS...DESPITE A VERY
FAVORABLE ENVIRONMENT...WAS NOT WELL FORECAST BY THE NHC OR THE
MODELS.  THIS COULD BE THE RESULT OF COOL WATER UPWELLING DUE TO
THE VERY SLOW MOTION OF THIS TROPICAL CYCLONE.  NOW THAT NATE
APPEARS TO BE MOVING AND REMAINS IN A FAVORABLE ENVIRONMENT FOR
STRENGTHENING...SOME INTENSIFICATION APPEARS LIKELY.  THE OFFICIAL
FORECAST SHOWS STEADY STRENGTHENING UNTIL LANDFALL AND IS CLOSE TO
THE SHIPS MODEL.  NATE IS FORECAST TO DISSIPATE OVER THE SIERRA
MADRE MOUNTAINS BY 72 HOURS.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/0900Z 20.0N  93.7W   45 KT  50 MPH
 12H  10/1800Z 20.0N  94.3W   50 KT  60 MPH
 24H  11/0600Z 19.9N  95.4W   55 KT  65 MPH
 36H  11/1800Z 19.8N  96.6W   60 KT  70 MPH...INLAND
 48H  12/0600Z 19.7N  97.7W   30 KT  35 MPH...INLAND
 72H  13/0600Z...DISSIPATED
 
$$
FORECASTER CANGIALOSI/AVILA
 

WTNT45 KNHC 101433
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
1000 AM CDT SAT SEP 10 2011
 
NATE CONTINUES TO HAVE A SOMEWHAT ATYPICAL APPEARANCE...WITH A LARGE
CENTER FILLED WITH LOW CLOUDS SURROUNDED BY SOME WEAK CONVECTIVE
BANDING. DVORAK CURRENT INTENSITY ESTIMATES ARE 45 KT FROM TAFB AND
SAB...AND THAT WILL BE THE INTENSITY FOR THIS ADVISORY. ANOTHER AIR
FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL INVESTIGATE NATE THIS
AFTERNOON. GIVEN THE LACK OF AN INNER CORE...IT APPEARS THAT ONLY
GRADUAL INTENSIFICATION IS LIKELY BEFORE LANDFALL. THE OFFICIAL
FORECAST REFLECTS THIS THINKING AND IS CLOSE TO A BLEND OF THE
SHIPS AND LGEM. IT IS POSSIBLE THAT NATE COULD STILL APPROACH
HURRICANE STRENGTH BETWEEN THE 24-HOUR FORECAST POINT AND
LANDFALL...SO THE HURRICANE WATCH IS MAINTAINED AT THIS TIME. NATE
SHOULD WEAKEN RAPIDLY AFTER LANDFALL AND DISSIPATE BY 72 HOURS...
HOWEVER THE THREAT OF HEAVY RAINFALL WILL PERSIST EVEN AFTER THE
CYCLONE WEAKENS.
 
THE INITIAL MOTION ESTIMATE IS 270/05...AS NATE IS NOW BEING STEERED
BY THE SUBTROPICAL RIDGE TO THE NORTH. AS A MID-LEVEL ANTICYCLONE
STRENGTHENS OVER MEXICO...A MOTION TO THE SOUTH OF DUE WEST IS
SHOWN BY MUCH OF THE GUIDANCE BY 12 HOURS...AND THAT IS REFLECTED IN
THE OFFICIAL FORECAST. THE NEW NHC TRACK IS AN UPDATE OF THE
PREVIOUS ONE AND LIES NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  10/1500Z 20.0N  94.2W   45 KT  50 MPH
 12H  11/0000Z 19.9N  95.0W   50 KT  60 MPH
 24H  11/1200Z 19.8N  96.1W   55 KT  65 MPH
 36H  12/0000Z 19.7N  97.2W   40 KT  45 MPH...INLAND
 48H  12/1200Z 19.6N  98.4W   30 KT  35 MPH...INLAND
 72H  13/1200Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

WTNT45 KNHC 102042
TCDAT5
 
TROPICAL STORM NATE DISCUSSION NUMBER  13
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL152011
400 PM CDT SAT SEP 10 2011
 
THE STRUCTURE OF NATE HAS IMPROVED THIS AFTERNOON...WITH AN INCREASE
IN DEEP CONVECTION...PARTICULARLY IN A LARGE CURVED BAND TO THE
EAST OF THE CENTER. THE HURRICANE HUNTER AIRCRAFT MEASURED A PEAK
850-MB FLIGHT LEVEL WIND OF 68 KT IN THE NORTHEAST QUADRANT AND AN
SFMR WIND OF 52 KT AS THE PLANE EXITED THE CENTER TO THE NORTHEAST.
BASED ON THESE DATA THE INITIAL INTENSITY IS INCREASED TO 55 KT.
STEADY INTENSIFICATION SEEMS LIKELY THROUGH LANDFALL AS NATE MOVES
OVER VERY WARM WATERS IN A LOW SHEAR ENVIRONMENT. THE OFFICIAL
FORECAST REFLECTS THIS THINKING AND SHOWS THE SYSTEM REACHING
HURRICANE STRENGTH BEFORE LANDFALL...IN GOOD AGREEMENT WITH THE
SHIPS MODEL.
 
AFTER PAUSING EARLIER THIS AFTERNOON...NATE AGAIN APPEARS TO BE
MOVING TOWARD THE WEST OR 270 DEGREES AT ABOUT 5 KNOTS. THE TRACK
FORECAST REASONING REMAINS UNCHANGED...AS THE CYCLONE SHOULD
CONTINUE MOVING WESTWARD OR JUST SOUTH OF DUE WEST THROUGH LANDFALL
TO THE SOUTH OF A MID-LEVEL RIDGE. THE NEW NHC FORECAST WAS
ADJUSTED NORTHWARD A LITTLE DUE TO THE INITIAL POSITION BEING A BIT
NORTH OF EARLIER ESTIMATES...BUT WAS OTHERWISE UNCHANGED AND LIES
BETWEEN THE GFS AND ECMWF MODELS.
 
A HURRICANE WARNING IS NOW REQUIRED FOR A PORTION OF THE COAST OF
MEXICO FROM TUXPAN TO VERACRUZ.
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  10/2100Z 20.1N  94.6W   55 KT  65 MPH
 12H  11/0600Z 20.0N  95.3W   60 KT  70 MPH
 24H  11/1800Z 19.9N  96.4W   65 KT  75 MPH
 36H  12/0600Z 19.8N  97.5W   40 KT  45 MPH...INLAND
 48H  12/1800Z 19.7N  98.7W   30 KT  35 MPH...INLAND
 72H  13/1800Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

