WTNT44 KNHC 030831
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 AM EDT TUE AUG 03 2010
 
THE TROPICAL CYCLONE HAS BECOME BETTER ORGANIZED OVER THE PAST
SEVERAL HOURS.  ENHANCED INFRARED SATELLITE IMAGES SHOW A CURVED
BAND WRAPPING HALFWAY AROUND THE CIRCULATION OVER THE WESTERN
SEMICIRCLE.  DVORAK DATA T-NUMBERS ARE 2.5 FROM BOTH TAFB AND SAB
SUPPORTING A CURRENT INTENSITY ESTIMATE OF 35 KT.  THEREFORE THE
SYSTEM IS BEING NAMED AT THIS TIME.  COLIN IS EXPECTED TO BE IN AN
ENVIRONMENT CONDUCIVE FOR SOME STRENGTHENING...WITH MODERATE TO
WEAK VERTICAL SHEAR AND ANTICYCLONIC UPPER-LEVEL FLOW...FOR THE
NEXT 36 HOURS OR SO.  THEREAFTER...INCREASING WESTERLY SHEAR
ASSOCIATED WITH AN UPPER-LEVEL LOW OVER THE SOUTHWESTERN NORTH
ATLANTIC SHOULD BEGIN TO IMPACT THE STORM.  THE OFFICIAL FORECAST
CALLS FOR MODEST STRENGTHENING DURING THE NEXT 36 HOURS FOLLOWED BY
A LEVELING OFF OF INTENSITY THEREAFTER.  THIS IS SIMILAR TO THE
LATEST GFDL MODEL FORECAST AND NOT TOO DISSIMILAR TO THE PREVIOUS
NHC FORECAST.  NONE OF THE DYNAMICAL OR STATISTICAL/DYNAMICAL
INTENSITY GUIDANCE BRINGS COLIN TO HURRICANE STRENGTH OVER THE NEXT
5 DAYS.
 
CENTER FIXES SHOW THAT THE STORM CONTINUES TO MOVE BRISKLY TOWARD
THE WEST-NORTHWEST...AND THE INITIAL MOTION ESTIMATE REMAINS AT
285/20.  AT THIS TIME...THE STEERING FOR COLIN IS BEING PROVIDED DUE
TO A SUBTROPICAL RIDGE TO THE NORTH AND A LOW- TO MID-TROPOSPHERIC
EASTERLY JET.  THIS RELATIVELY FAST STEERING CURRENT SHOULD MORE OR
LESS PREVAIL FOR THE NEXT COUPLE OF DAY OR SO.  THEREAFTER...THE
TROPICAL CYCLONE IS LIKELY TO APPROACH A WEAKNESS IN THE
SUBTROPICAL RIDGE.  THIS WOULD CAUSE A GRADUAL TURN TO THE RIGHT
ALONG WITH A DECREASING FORWARD SPEED.  THE TRACK GUIDANCE MODELS
ARE IN FAIRLY GOOD AGREEMENT OVER THE NEXT 36 HOURS.  AFTER THAT
FORECAST TIME...THE MODELS BECOME MODERATELY DIVERGENT WITH THE GFS
AND ECMWF ON THE LEFT SIDE OF THE GUIDANCE ENVELOPE AND THE GFDL
AND HWRF ON THE RIGHT.  THE OFFICIAL TRACK FORECAST IS ROUGHLY IN
THE MIDDLE OF THE ENVELOPE...FAIRLY CLOSE TO THE DYNAMICAL MODEL
CONSENSUS...AND VERY CLOSE TO THE PREVIOUS NHC FORECAST.

OBSERVATIONS FROM NOAA DATA BUOY 41041 OVER THE CENTRAL TROPICAL
ATLANTIC INDICATE THAT COLIN IS A SMALL TROPICAL STORM...AND THE
WIND RADII SHOWN IN THE ADVISORY MIGHT BE GENEROUS.

INTERESTS IN THE NORTHERN LEEWARD ISLANDS SHOULD FOLLOW THE PROGRESS
OF COLIN.  AT THIS TIME...BASED ON THE FORECAST TRACK...WIND
FIELD...AND REASONABLE UNCERTAINTIES...NO TROPICAL STORM WATCHES OR
WARNINGS ARE REQUIRED.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/0900Z 14.0N  47.2W    35 KT
 12HR VT     03/1800Z 15.1N  50.3W    40 KT
 24HR VT     04/0600Z 16.8N  54.5W    45 KT
 36HR VT     04/1800Z 18.6N  58.3W    50 KT
 48HR VT     05/0600Z 20.6N  61.5W    50 KT
 72HR VT     06/0600Z 24.5N  66.5W    50 KT
 96HR VT     07/0600Z 28.0N  68.5W    50 KT
120HR VT     08/0600Z 31.0N  69.5W    50 KT
 
$$
FORECASTER PASCH
 

WTNT44 KNHC 031438
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 AM EDT TUE AUG 03 2010

COLIN HAS A VERY RAGGED APPEARANCE THIS MORNING.  THE CONVECTIVE
BANDING SEEN EARLIER HAS WEAKENED...LEAVING A SMALL CONVECTIVE MASS
NEAR THE CENTER AND A SECOND CONVECTIVE MASS TO THE NORTH. 
SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB AND 30 KT FROM
SAB...AND BASED ON THIS THE INITIAL INTENSITY REMAINS 35 KT.  IT
SHOULD BE NOTED THAT IT IS HARD TO FIND WESTERLY WINDS IN THE LOW
CLOUD MOTIONS SOUTH OF THE CENTRAL CONVECTION...AND THERE IS SOME
QUESTION AS TO WHETHER COLIN STILL HAS A CLOSED CIRCULATION.

THE SYSTEM HAS TURNED A LITTLE TO THE LEFT DURING THE PAST SEVERAL
HOURS.  THE INITIAL MOTION IS 280/21...AND THE SHORT-TERM MOTION
MAY BE EVEN FASTER.  COLIN IS ON THE SOUTH SIDE OF THE LOW/
MID-LEVEL BERMUDA HIGH...AND IN 48-72 HR SHOULD BE APPROACHING A
WEAKNESS OR BREAK IN THE HIGH CAUSED BY A MID/UPPER-LEVEL TROUGH
NEAR THE SOUTHEASTERN COAST OF THE UNITED STATES.  THIS PATTERN
SHOULD INITIALLY STEER COLIN RAPIDLY TOWARD THE WEST-NORTHWEST...
FOLLOWED BY A TURN TOWARD THE NORTHWEST WITH A DECREASE IN FORWARD
SPEED AFTER 48 HR.  THE MODEL GUIDANCE GENERALLY AGREES WITH THIS
SCENARIO.  HOWEVER...THERE IS A CONSIDERABLE SPREAD IN THE TRACKS
BY THE END OF THE FORECAST PERIOD.  THE GFDL AND HWRF FORECAST AN
EAST OF NORTH MOTION ON THE RIGHT EDGE OF THE GUIDANCE ENVELOPE BY
120 HR...WHILE THE CANADIAN AND GFDN ARE ON THE LEFT EDGE WITH NO
NORTHWARD TURN BEFORE 120 HR.  THE NEW FORECAST TRACK IS SHIFTED
60-90 N MI TO THE SOUTHWEST BASED ON THE INITIAL POSITION AND
MOTION.  IT IS IN BEST AGREEMENT WITH THE ECMWF AND LIES TO THE
LEFT OF THE CONSENSUS MODELS AND THE CENTER OF THE GUIDANCE
ENVELOPE.

CURRENTLY...COLIN IS EXPERIENCING WESTERLY VERTICAL SHEAR LIKELY
CAUSED BY THE LOWER PART OF THE STORM OUTRUNNING THE UPPER PART. 
THIS IS FORECAST TO CONTINUE FOR THE NEXT 24-36 HR DUE TO THE RAPID
MOTION.  AFTER THAT TIME...THE SYSTEM IS EXPECTED TO ENCOUNTER
INCREASING UPPER-LEVEL WESTERLY WINDS CAUSED BY THE WESTERN
ATLANTIC TROUGH.  THIS PATTERN DOES NOT APPEAR FAVORABLE FOR
SIGNIFICANT STRENGTHENING...AND THE ONLY INTENSITY GUIDANCE THAT
CURRENTLY CALLS FOR COLIN TO BECOME A HURRICANE IS CLIMATOLOGY/
PERSISTENCE.  GIVEN THE CURRENT TRENDS AND THE FORECAST SHEAR...THE
INTENSITY FORECAST IS A LITTLE WEAKER THAN THE PREVIOUS FORECAST...
WITH AN INTENSITY OF 45 KT THROUGH MOST OF THE FORECAST PERIOD.  AN
ALTERNATIVE SCENARIO IS THAT COLIN COULD DEGENERATE TO AN OPEN WAVE
DUE TO A COMBINATION OF ITS RAPID MOTION AND WESTERLY SHEAR.
 
INTERESTS IN THE NORTHERN LEEWARD ISLANDS AND THE VIRGIN ISLANDS
SHOULD FOLLOW THE PROGRESS OF COLIN. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/1500Z 14.2N  49.5W    35 KT
 12HR VT     04/0000Z 15.0N  52.7W    40 KT
 24HR VT     04/1200Z 16.5N  56.6W    45 KT
 36HR VT     05/0000Z 18.3N  60.4W    45 KT
 48HR VT     05/1200Z 20.2N  63.7W    45 KT
 72HR VT     06/1200Z 23.0N  67.5W    45 KT
 96HR VT     07/1200Z 26.5N  69.5W    45 KT
120HR VT     08/1200Z 29.0N  70.5W    50 KT
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 032043
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 PM EDT TUE AUG 03 2010
 
THE CENTER OF COLIN PASSED NEAR OR OVER THE WOODS HOLE NTAS BUOY
ABOUT 15Z...WHICH REPORTED A MINIMUM PRESSURE OF 1007 MB AND A
SMALL LOW PRESSURE CENTER.  HOWEVER...NEITHER THAT BUOY NOR THE
NEARBY NOAA BUOY 41040 REPORTED WINDS SUPPORTING A CLOSED
CIRCULATION...AND WESTERLY WINDS ARE NOT CURRENTLY APPARENT IN LOW
CLOUD MOTIONS SOUTH OF THE CENTER.  ADDITIONALLY...THE ASSOCIATED
CONVECTION HAS BECOME VERY DISORGANIZED.  BASED ON THIS...COLIN HAS
DEGENERATED INTO A REMNANT LOW WITH GALE-FORCE WINDS OVER A SMALL
AREA NORTH OF THE CENTER.  
 
IN THE SHORT TERM...REGENERATION APPEARS UNLIKELY AS THE REMNANTS OF
COLIN ENCOUNTER WESTERLY VERTICAL SHEAR CAUSED BY THE STRONG
LOW-LEVEL FLOW AND WESTERLY WINDS ASSOCIATED WITH A COMPLEX
UPPER-LEVEL TROUGH OVER THE SOUTHWESTERN ATLANTIC.  HOWEVER...NONE
OF THE DYNAMICAL MODELS FORECAST THE REMNANTS OF COLIN TO DISSIPATE
DURING THE FORECAST PERIOD...AND THEY FORECAST THAT THE SYSTEM
COULD REACH A MORE FAVORABLE ENVIRONMENT OFF THE SOUTHEASTERN COAST
OF THE UNITED STATES BY DAY 5.  BASED ON THIS...THE INTENSITY
FORECAST CALLS FOR THE REMNANTS OF COLIN TO DROP BELOW GALE FORCE
DURING THE NEXT 12 HR AND CONTINUE AS A 30 KT REMNANT LOW THROUGH
96 HR.  AFTER THAT...THE DISTURBANCE COULD REGENERATE INTO A
TROPICAL CYCLONE AS SHOWN IN THE 120-HR FORECAST.
 
THE INITIAL MOTION IS AN EXTREMELY RAPID 285/30.  ALL GUIDANCE
AGREES THAT THE REMNANTS OF COLIN SHOULD CONTINUE WEST-
NORTHWESTWARD FOR THE NEXT 48-72 HR WITH A SIGNIFICANT DECREASE IN
FORWARD SPEED.  THE NEW FORECAST TRACK IS SIMILAR IN DIRECTION TO
THE PREVIOUS FORECAST...BUT IS MUCH FASTER.  AFTER THAT TIME...THE
SYSTEM SHOULD TURN NORTHWESTWARD INTO A BREAK IN THE SUBTROPICAL
RIDGE NEAR THE EASTERN COAST OF THE UNITED STATES.  MOST OF THE
DYNAMICAL MODELS HAVE SHIFTED THEIR 96-120 HR FORECASTS WESTWARD...
AND THE OFFICIAL FORECAST WILL DO LIKEWISE.
 
INTERESTS IN THE NORTHERN LEEWARD ISLANDS AND THE VIRGIN ISLANDS
SHOULD FOLLOW THE PROGRESS OF THE REMNANTS OF COLIN.

THIS IS THE LAST ADVISORY ISSUED BY THE NATIONAL HURRICANE CENTER ON
THIS SYSTEM UNLESS REGENERATION OCCURS.  ADDITIONAL INFORMATION ON
THIS SYSTEM CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE
NATIONAL WEATHER SERVICE...UNDER AWIPS HEADER NFDHSFAT1 AND WMO
HEADER FZNT01 KWBC.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/2100Z 15.8N  53.8W    35 KT...POST-TROP/REMNT LOW
 12HR VT     04/0600Z 16.8N  57.2W    30 KT...POST-TROP/REMNT LOW
 24HR VT     04/1800Z 18.4N  60.8W    30 KT...POST-TROP/REMNT LOW
 36HR VT     05/0600Z 20.0N  63.8W    30 KT...POST-TROP/REMNT LOW
 48HR VT     05/1800Z 21.7N  66.5W    30 KT...POST-TROP/REMNT LOW
 72HR VT     06/1800Z 25.0N  70.0W    30 KT...POST-TROP/REMNT LOW
 96HR VT     07/1800Z 28.0N  72.5W    30 KT...POST-TROP/REMNT LOW
120HR VT     08/1800Z 30.0N  73.5W    30 KT...TROPICAL DEPRESSION
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 052101
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 PM AST THU AUG 05 2010
 
SATELLITE IMAGERY AND REPORTS FROM AN AIR FORCE RESERVE HURRICANE
HUNTER AIRCRAFT INDICATE THAT THE REMNANTS OF COLIN HAVE DEVELOPED
SUFFICIENT ORGANIZED CONVECTION AND A WELL-ENOUGH DEFINED CENTER OF
CIRCULATION TO AGAIN BE DESIGNATED A TROPICAL CYCLONE.  THE
AIRCRAFT FOUND 500-FT FLIGHT-LEVEL WINDS OF 50-52 KT AND SFMR WINDS
NEAR 40 KT EAST OF THE CENTER.  BASED ON THIS...ADVISORIES ARE
RE-INITIATED ON TROPICAL STORM COLIN AT AN INITIAL INTENSITY OF 40
KT.  
 
THE INITIAL MOTION IS 325/17.  COLIN IS BETWEEN THE SUBTROPICAL
RIDGE AND A MID/UPPER-LEVEL LOW 27N74W...WITH A DEEP-LAYER TROUGH
MOVING SOUTHEASTWARD INTO THE NORTHEASTERN UNITED STATES AND
EASTERN CANADA.  THIS COMBINATION SHOULD CAUSE COLIN TO TURN
NORTHWARD AROUND THE WESTERN EDGE OF THE RIDGE DURING THE NEXT
36-48 HR...FOLLOWED BY A NORTHEASTWARD TURN AND GRADUAL
ACCELERATION INTO THE WESTERLIES.  THE TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH THIS SCENARIO...ALTHOUGH THERE IS SOME SPREAD IN THE
FORWARD SPEED BETWEEN THE SLOWER GFS AND THE FASTER UKMET.  THE
FORECAST TRACK COMPROMISES IN SPEED BETWEEN THESE TWO EXTREMES AND
IS JUST TO THE WEST OF THE CONSENSUS MODELS.
 
COLIN IS EXPERIENCING 20-25 KT OF WESTERLY VERTICAL WIND SHEAR
CAUSED BY THE UPPER-LEVEL LOW.  THIS SHOULD CONTINUE FOR 12-24
HR...WITH THE STORM FINDING A MORE FAVORABLE SHEAR ENVIRONMENT FROM
24-72 HR.  THE INTENSITY FORECAST THUS CALLS FOR LITTLE CHANGE IN
STRENGTH FOR 24 HR...FOLLOWED BY STEADY INTENSIFICATION.  THE GFDL
AND HWRF CALL FOR COLIN TO REACH HURRICANE STRENGTH IN ABOUT 72
HR...WHILE THE SHIPS AND LGEM ARE LESS INTENSE.  THE FORECAST PEAK
INTENSITY IS A COMPROMISE BETWEEN THESE MODELS.  EXTRATROPICAL
TRANSITION IS EXPECTED TO BEGIN AT ABOUT 96 HR AND BE COMPLETE AT
120 HR.

INTERNET PROBLEMS WILL PREVENT THE NHC WEB SITE FROM BEING UPDATED
AT THIS TIME.  PLEASE SEE WEATHER.GOV FOR ADVISORY TEXT PRODUCTS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/2100Z 24.9N  66.3W    40 KT
 12HR VT     06/0600Z 26.6N  67.3W    40 KT
 24HR VT     06/1800Z 28.1N  67.7W    40 KT
 36HR VT     07/0600Z 29.6N  67.5W    45 KT
 48HR VT     07/1800Z 31.3N  67.1W    50 KT
 72HR VT     08/1800Z 36.0N  65.0W    55 KT
 96HR VT     09/1800Z 40.0N  61.5W    60 KT
120HR VT     10/1800Z 49.0N  48.0W    50 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 060001
TCDAT4
TROPICAL STORM COLIN SPECIAL DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
730 PM AST THU AUG 05 2010
 
...THIS SPECIAL ADVISORY HAS BEEN ISSUED TO PRIMARILY UPDATE THE
INTENSITY AND WIND RADII FORECASTS.

SHORTLY AFTER THE PREVIOUS ADVISORY HAD BEEN ISSUED...AN AIR FORCE
RESERVE RECONNAISSANCE AIRCRAFT INVESTIGATING TROPICAL STORM COLIN
REPORTED A 600-FT FLIGHT-LEVEL WIND OF 71 KT ABOUT 14 NMI NORTHEAST
OF THE CIRCULATION CENTER. IN ADDITION...A SURFACE PRESSURE OF 1005
MB WAS ALSO OBSERVED IN THE GENERAL VICINITY. IT IS UNCERTAIN IF
THESE VALUES WERE ASSOCIATED WITH A SMALL MESOVORTEX LOCATED
NORTHEAST OF THE CENTER...WHICH WOULD NOT BE REPRESENTATIVE OF THE
LARGER-SCALE WIND FIELD. FOR THIS REASON...THE INTENSITY WAS
INITIALIZED AT 40 KT IN AGREEMENT WITH NEARBY SFMR WINDS.
HOWEVER...SINCE THE TIME OF THAT RECON REPORT...DEEP CONVECTION IN
THE NORTHEASTERN QUADRANT OF COLIN HAS CONTINUED TO DEVELOP CLOSER
TO THE LOW-LEVEL CIRCULATION CENTER...WHICH JUSTIFIES INCREASING
THE INTENSITY TO 50 KT BASED ON A BLEND OF THE FLIGHT-LEVEL WINDS
AND SFMR SURFACE WINDS. SINCE A FORECAST INTENSITY OF 50 KT WAS NOT
EXPECTED TO OCCUR UNTIL 48 HOURS IN THE PREVIOUS ADVISORY...A
SPECIAL ADVISORY WAS REQUIRED TO INCREASE THE INTENSITY AND TO
ADJUST THE INTENSITY FORECAST UPWARD DURING THE NEXT 36 HOURS.
ALSO...DROPSONDE DATA INDICATES AN EXPANSION OF THE 34-KT WIND
RADII IN THE SOUTHEASTERN QUADRANT WAS NECESSARY.
 
NO SIGNIFICANT CHANGES TO THE PREVIOUS TRACK FORECAST OR REASONING
WERE MADE.
 
INTERNET PROBLEMS WILL PREVENT THE NHC WEB SITE FROM BEING UPDATED
AT THIS TIME.  PLEASE SEE WEATHER.GOV FOR ADVISORY TEXT PRODUCTS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/2330Z 25.6N  66.3W    50 KT
 12HR VT     06/0600Z 26.6N  67.1W    50 KT
 24HR VT     06/1800Z 28.1N  67.3W    50 KT
 36HR VT     07/0600Z 29.6N  67.3W    50 KT
 48HR VT     07/1800Z 31.3N  67.1W    55 KT
 72HR VT     08/1800Z 36.0N  65.0W    55 KT
 96HR VT     09/1800Z 40.0N  61.5W    60 KT
120HR VT     10/1800Z 49.0N  48.0W    50 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART/BROWN
 

WTNT44 KNHC 060345
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 PM AST THU AUG 05 2010
 
COLIN HAS MAINTAINED A SATELLITE CLOUD SIGNATURE SIMILAR TO WHEN A
RECONNAISSANCE AIRCRAFT INVESTIGATED THE SYSTEM 6 HOURS AGO. SINCE
THEN...A STRONG BURST OF DEEP CONVECTION HAS DEVELOPED IN THE
NORTHEASTERN QUADRANT...ALTHOUGH THE CONVECTION HAS WANED A LITTLE
DURING THE PAST COUPLE OF HOURS. HOWEVER...THE STRONG PRESSURE
GRADIENT IN THE EASTERN SEMICIRCLE BETWEEN THE CENTER OF COLIN AND
NOAA BUOY 41049 LOCATED 225 NMI TO THE NORTHEAST SUPPORTS KEEPING
THE INTENSITY AT 50 KT.
 
THE INITIAL MOTION ESTIMATE IS 340/12. THERE IS NO SIGNIFICANT
CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. COLIN IS
EXPECTED TO GRADUALLY SLOW DOWN AND TURN NORTHWARD TOWARD A
DEVELOPING WEAKNESS IN THE SUBTROPICAL RIDGE OVER THE NEXT 48
HOURS...AND THEN RECURVE TO THE NORTHEAST OVER THE NORTH ATLANTIC
BY 72 HOURS AHEAD OF AN EASTWARD-MOVING MID-LATITUDE SHORTWAVE
TROUGH CURRENTLY MOVING ACROSS GREAT LAKES AND OHIO VALLEY REGIONS.
THE MODELS REMAIN IN GOOD AGREEMENT ON THIS SCENARIO...AND THE
FORECAST TRACK WAS ONLY NUDGED SLIGHTLY TO THE EAST THROUGH 48
HOURS DUE TO THE MORE EASTWARD INITIAL POSITION. COLIN IS EXPECTED
TO PASS JUST WEST OF BERMUDA IN 36-48 HOURS...BUT ONLY A SLIGHT
DEVIATION TO THE EAST COULD BRING THE CENTER OVER BERMUDA.
 
SOUTHWESTERLY VERTICAL SHEAR OF 20-25 KT CONTINUES TO HINDER
SIGNIFICANT INTENSIFICATION OF COLIN...AND THESE UNFAVORABLE
CONDITIONS ARE EXPECTED TO CONTINUE THROUGH THE NEXT 24 HOURS.
HOWEVER...FROM 36 TO 48 HOURS...ALL OF THE GLOBAL MODELS ARE
FORECASTING THE VERTICAL SHEAR TO WEAKEN SIGNIFICANTLY AS COLIN
PASSES BETWEEN TWO UPPER-LEVEL LOWS AND MOVES UNDER A SMALL
RIDGE...WHICH PROVIDES A BRIEF WINDOW OF OPPORTUNITY FOR COLIN TO
STRENGTHEN. THE SHIPS AND LGEM MODELS BRING COLIN TO NEAR 60 KT BY
48 HOURS...WHEN THE CYCLONE IS NEAR BERMUDA...AND THIS TREND WAS
FOLLOWED FOR THIS ADVISORY PACKAGE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/0300Z 26.3N  66.6W    50 KT
 12HR VT     06/1200Z 27.4N  66.9W    50 KT
 24HR VT     07/0000Z 29.1N  67.0W    50 KT
 36HR VT     07/1200Z 30.7N  66.8W    55 KT
 48HR VT     08/0000Z 32.6N  66.1W    60 KT
 72HR VT     09/0000Z 37.2N  63.5W    60 KT
 96HR VT     10/0000Z 43.0N  57.0W    55 KT
120HR VT     11/0000Z 50.5N  45.0W    50 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER STEWART
 

WTNT44 KNHC 060838
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 AM AST FRI AUG 06 2010
 
VERTICAL WIND SHEAR...ANALYZED AT 25 KT BY THE SHIPS MODEL...HAS
AGAIN TAKEN A TOLL ON COLIN...WITH THE LOW-LEVEL CENTER NOW
COMPLETELY EXPOSED TO THE WEST OF THE PULSING DEEP CONVECTION.  AN
ASCAT PASS AROUND 0118 UTC SHOWED SEVERAL 35-40 KT RETRIEVALS EAST
OF THE CENTER...AND THE INITIAL INTENSITY IS LOWERED TO 40 KT FOR
THIS ADVISORY.  THE SHIPS MODEL SHOWS THE SHEAR DECREASING TO LESS
THAN 10 KT IN 24 HOURS...WHICH SHOULD GIVE COLIN AN OPPORTUNITY TO
RE-INTENSIFY.  HOWEVER...THE SHEAR INCREASES RAPIDLY AGAIN BY 48
HOURS...WHICH SHOULD LIMIT INTENSIFICATION BEYOND THAT TIME. THE
OFFICIAL INTENSITY FORECAST IS ADJUSTED DOWNWARD TOWARD THE ICON
INTENSITY CONSENSUS THROUGH 48 HOURS AND IS SIMILAR TO THE PREVIOUS
PACKAGE AFTER THAT.
 
THE 12-HOUR INITIAL MOTION ESTIMATE IS 325/12...TO THE LEFT OF THE
PREVIOUS TRACK FORECAST. COLIN IS SITUATED TO THE SOUTHEAST OF AN
UPPER-LEVEL SHEAR AXIS ANCHORED BY ONE LOW CENTER NEAR 27N 75W AND
ANOTHER NEAR BERMUDA.  THE GLOBAL MODELS SUGGEST THAT THESE LOWS
WILL MOVE AWAY AND ALLOW COLIN TO MOVE NORTHWARD AT A SLOWER SPEED
INTO A BREAK IN THE SUBTROPICAL RIDGE OVER THE NEXT COUPLE OF DAYS.
BEYOND THAT TIME...THE GLOBAL MODELS SHOW A LONGWAVE TROUGH
ADVANCING EASTWARD ACROSS THE NORTHEASTERN U.S. AND EASTERN
CANADA.  HOWEVER...THE TIMING OF THE INTERACTION BETWEEN COLIN AND
INDIVIDUAL SHORTWAVES IN THE TROUGH VARIES WIDELY IN THE
GUIDANCE...AND SO DOES THE FORWARD SPEED AND TRACK OF THE CYCLONE.
THE GFS...ECMWF...AND GFDL MOVE COLIN MORE SLOWLY AND DELAY
INTERACTION WITH THE TROUGH UNTIL AROUND DAY 4...WHILE THE UKMET...
NOGAPS...AND HWRF TAKE COLIN MORE QUICKLY NORTHWARD AND SHOW
INTERACTION WITH THE TROUGH ABOUT A DAY EARLIER. GIVEN THAT
THE 72-HOUR FORECAST POSITIONS FROM THE GFS AND NOGAPS ARE ABOUT
1000 MILES APART...THIS TRACK FORECAST HAS LOW CONFIDENCE...
ESPECIALLY IN THE LATER PERIODS.  THE OFFICIAL FORECAST HAS BEEN
ADJUSTED TO THE LEFT OF THE PREVIOUS NHC TRACK THROUGH 48 HOURS DUE
TO THE MORE WESTERLY INITIAL POSITION AND MOTION...AND LIES ALONG
THE LEFT SIDE OF THE GUIDANCE ENVELOPE. BEYOND THAT TIME...THE
BIGGEST CHANGE TO THE OFFICIAL FORECAST WAS TO SLIGHTLY DECREASE THE
FORWARD SPEED DUE TO THE LARGE SPREAD IN THE GUIDANCE. ONE
ALTERNATIVE SCENARIO IS THAT IF COLIN REMAINS A SHALLOW SYSTEM
WITHOUT MUCH DEEP CONVECTION...IT COULD MOVE FARTHER TO THE LEFT
AND MORE SLOWLY IN THE SHORT TERM ALONG A TRACK SIMILAR TO THE
SHALLOW BAM.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/0900Z 26.8N  67.4W    40 KT
 12HR VT     06/1800Z 27.9N  67.7W    40 KT
 24HR VT     07/0600Z 29.8N  67.4W    45 KT
 36HR VT     07/1800Z 31.5N  66.8W    50 KT
 48HR VT     08/0600Z 33.6N  65.7W    55 KT
 72HR VT     09/0600Z 38.5N  62.5W    60 KT
 96HR VT     10/0600Z 44.0N  56.0W    55 KT
120HR VT     11/0600Z 50.5N  45.0W    50 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 061449
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 AM AST FRI AUG 06 2010

COLIN SHOWS A CLASSIC SHEAR PATTERN THIS MORNING WITH THE LOW-LEVEL
CENTER EXPOSED TO THE WEST OF THE MAIN CONVECTIVE MASS BY 20-25 KT
OF WESTERLY VERTICAL WIND SHEAR.  DVORAK AND AMSU SATELLITE
INTENSITY ESTIMATES HAVE NOT CHANGED SINCE THE PREVIOUS ADVISORY
AND REMAIN NEAR 35 KT.  BASED ON THIS...THE INITIAL INTENSITY
REMAINS 40 KT...AND THIS COULD BE A LITTLE GENEROUS.  AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO INVESTIGATE COLIN
AROUND 18Z TODAY.

JUST AFTER THE PREVIOUS ADVISORY...THE CENTER OF COLIN TOOK A SHARP
TURN TO THE RIGHT...AND IT HAS BEEN MOVING 065/6 FOR THE PAST
SEVERAL HOURS.  THIS IS LIKELY TO BE TEMPORARY...AS THE SYNOPTIC
PATTERN OF HIGHER PRESSURES TO THE EAST AND LOWER PRESSURES TO THE
WEST SUPPORT A MOTION TOWARD THE NORTH DURING THE NEXT 24-36 HR. 
THAT MOTION SHOULD BRING COLIN NORTH OF THE SUBTROPICAL RIDGE AXIS
INTO THE WESTERLIES...WHICH IN TURN SHOULD CAUSE THE CYCLONE TO MOVE
NORTHEASTWARD WITH AN INCREASING FORWARD SPEED.  THE TRACK GUIDANCE
IS IN GOOD AGREEMENT WITH THIS SCENARIO...BUT THERE REMAIN SOME
SPREAD IN THE SPEED BETWEEN THE SLOWER GFS AND THE FASTER NOGAPS. 
THE NEW FORECAST TRACK IS NUDGED TO THE EAST BASED ON THE INITIAL
POSITION AND MOTION AND IS IN BEST OVERALL AGREEMENT WITH THE UKMET
AND ECMWF.  SOME ADDITIONAL ADJUSTMENT MAY BE NECESSARY LATER
TODAY...DEPENDING ON HOW LONG COLIN CONTINUES THE CURRENT MOTION.
 
SHEAR FORECASTS FROM THE SHIPS AND THE DYNAMICAL MODELS SUGGEST THAT
THE CURRENT SHOULD SHOULD DECREASE DURING THE NEXT 12-24 HR...
ALTHOUGH THE SHIPS MODEL MAY BE OVERLY OPTIMISTIC WITH ITS FORECAST
OF 11 KT OF SHEAR BY 00Z.  AFTER THIS...COLIN IS LIKELY TO REMAIN
IN AN ENVIRONMENT FAVORABLE FOR STRENGTHENING UNTIL IT REACHES
STRONGER SHEAR IN THE MAIN BELT OF THE WESTERLIES IN ABOUT 72 HR. 
THE GFDL AND HWRF FORECAST COLIN TO BECOME A HURRICANE BY 72 HR...
WHILE THE SHIPS AND LGEM ARE LESS AGGRESSIVE.  THE FORECAST PEAK
INTENSITY OF 60 KT IS A COMPROMISE BETWEEN THESE EXTREMES IN
AGREEMENT WITH THE INTENSITY CONSENSUS.  EXTRATROPICAL TRANSITION
SHOULD BEGIN AT ABOUT 72 HR AND BE COMPLETE BY 96 HR...WITH THE
DYNAMICAL MODELS FORECASTING COLIN TO REMAIN A STRONG CYCLONE
THROUGH THAT PROCESS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/1500Z 27.1N  66.9W    40 KT
 12HR VT     07/0000Z 28.3N  66.9W    40 KT
 24HR VT     07/1200Z 30.2N  66.3W    45 KT
 36HR VT     08/0000Z 32.2N  65.4W    50 KT
 48HR VT     08/1200Z 34.5N  64.1W    55 KT
 72HR VT     09/1200Z 39.5N  60.0W    60 KT
 96HR VT     10/1200Z 45.0N  52.0W    55 KT...POST-TROP/EXTRATROP
120HR VT     11/1200Z 53.0N  41.5W    50 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 062033
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 PM AST FRI AUG 06 2010
 
THERE HAVE BEEN SOME CHANGES WITH COLIN AND THE NEAR-STORM
ENVIRONMENT SINCE THE LAST ADVISORY.  FIRST...THE WELL-DEFINED LOW
CLOUD SWIRL SEEN EARLIER HAS BECOME PART OF A LARGER ELONGATED
CIRCULATION WITH MULTIPLE SWIRLS ROTATING AROUND A MEAN CENTER.
SECOND...CIRRUS CLOUDS APPROACHING THE CENTER FROM THE SOUTHWEST
ARE MOVING AT 40 KT...SUGGESTING THAT THE VERTICAL WIND SHEAR HAS
INCREASED.  THIRD...LIKELY AS A RESULT OF THE INCREASED SHEAR...THE
CONVECTION HAS DECREASED NEAR THE CENTER.  DESPITE THESE NEGATIVE
FACTORS...AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT HAS FOUND
43-KT WINDS AT 500 FT SOUTHEAST OF THE CENTER WITH ESTIMATED
SURFACE WINDS FROM THE SFMR OF 39 KT.  BASED ON THIS...THE INITIAL
INTENSITY REMAINS A POSSIBLY GENEROUS 40 KT.
 
AFTER THE TRACK EXCURSION NOTED EARLIER...THE MEAN CENTER OF THE
CIRCULATION HAS RESUMED A NORTHWARD MOTION OF 010/8.  THERE IS
LITTLE CHANGE TO THE TRACK FORECAST PHILOSOPHY.  COLIN IS MOVING
NORTHWARD BETWEEN THE SUBTROPICAL RIDGE AND A MID/UPPER-LEVEL LOW
NEAR 28N74W AS A DEEP-LAYER WESTERLY TROUGH MOVES ACROSS THE
NORTHEASTERN UNITED STATES.  ALL TRACK GUIDANCE AGREES THAT THE
CYCLONE SHOULD CONTINUE GENERALLY NORTHWARD OR NORTH-NORTHEASTWARD
FOR THE NEXT 36-48 HR...THEN TURN NORTHEASTWARD AT A FASTER FORWARD
SPEED AS IT REACHES THE MAIN BELT OF THE WESTERLIES.  THE NEW
FORECAST TRACK IS AN UPDATE OF THE PREVIOUS FORECAST.
 
LITTLE CHANGE IN STRENGTH IS LIKELY DURING THE NEXT 12-18 HR AS THE
40-KT UPPER-LEVEL WINDS IMPACT THE SYSTEM.  THE DYNAMICAL MODELS
FORECAST THAT THE SHEAR SHOULD DECREASE AFTER THAT...WHICH IF
CORRECT WOULD ALLOW COLIN TO STRENGTH.  THE GFDL AND HWRF MODELS
CONTINUE TO FORECAST COLIN TO BECOME A HURRICANE IN 60-72 HR...
WHILE THE SHIPS AND LGEM MODELS FORECAST A PEAK INTENSITY OF 50-55
KT.  THE NEW INTENSITY FORECAST IS THE SAME AS THE PREVIOUS
FORECAST...CALLING FOR A PEAK INTENSITY OF 60 KT IN 72 HR IN BEST
AGREEMENT WITH THE FLORIDA STATE SUPERENSEMBLE AND THE INTENSITY
CONSENSUS.  EXTRATROPICAL TRANSITION SHOULD BE UNDERWAY BY 72 HR
AND BE COMPLETE BY 96 HR...WITH THE DYNAMICAL MODELS FORECASTING
COLIN TO REMAIN A STRONG CYCLONE THROUGH THAT PROCESS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/2100Z 28.3N  66.8W    40 KT
 12HR VT     07/0600Z 29.5N  66.4W    40 KT
 24HR VT     07/1800Z 31.1N  65.7W    45 KT
 36HR VT     08/0600Z 32.8N  64.9W    50 KT
 48HR VT     08/1800Z 35.1N  64.0W    55 KT
 72HR VT     09/1800Z 41.0N  59.0W    60 KT
 96HR VT     10/1800Z 47.5N  48.5W    55 KT...POST-TROP/EXTRATROP
120HR VT     11/1800Z 56.0N  40.0W    50 KT...POST-TROP/EXTRATROP
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 070240
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 PM AST FRI AUG 06 2010
 

COLIN IS A SHEARED CYCLONE WITH INCREASING CONVECTION NEAR AND TO
THE EAST OF THE CENTER AT THIS TIME. THIS COULD GIVE AN IMPRESSION
OF A STRONGER CYCLONE BUT FLUCTUATIONS IN CONVECTION ARE TYPICAL IN
SHEARED SYSTEMS.  THE STRONG UPPER-LEVEL WINDS CURRENTLY OVER THE
CYCLONE WILL PROBABLY SEPARATE THE CENTER FROM THE THUNDERSTORM
ACTIVITY AGAIN SOON. THEREFORE...THE INITIAL INTENSITY IS KEPT AT
40 KNOTS. ANOTHER RECONNAISSANCE PLANE WILL CHECK COLIN IN SEVERAL
HOURS. COLIN HAS A SMALL WINDOW OF OPPORTUNITY TO GATHER SOME
STRENGTH WITHIN THE NEXT DAY OR SO...IF THE SHEAR RELAXES A BIT AS
DIAGNOSED BY THE SHIPS MODEL. IN FACT...IF THE CURRENT INCREASE IN
CONVECTION CONTINUES OR PERSIST IT COULD MEAN THAT THE SHEAR IS
ALREADY RELAXING AND SLIGHT INTENSIFICATION IS ABOUT TO BEGIN. THE
OFFICIAL FORECAST ASSUMES THAT THE SHEAR WILL RELAX A BIT AND CALLS
FOR A SMALL INCREASE IN INTENSITY. BY 96 HOURS...COLIN SHOULD BE
EXTRATROPICAL AND THEN BECOME ABSORBED BY A LARGER CYCLONE. THE
INTENSIFICATION SHOWN IN BOTH THE GFDL AND HWRF MODELS OCCURS LATE
IN THE FORECAST PERIOD. THIS DOES NOT SEEM TO BE REALISTIC BECAUSE
BY THEN...THE CYCLONE IS EXPECTED TO BE REACHING COOLER WATERS AND
BECOMING EXTRATROPICAL.  

THE CENTER IS CLEARLY OBSERVED ON THE WESTERN EDGE OF THE CONVECTION
AND ONE CAN OBTAIN A GOOD ESTIMATE OF THE INITIAL MOTION...WHICH IS
TOWARD THE NORTH OR 010 DEGREES AT 8 KNOTS. COLIN IS ALREADY ON THE
WESTERN EDGE OF THE SUBTROPICAL RIDGE AND IS NEARING THE
MID-LATITUDE WESTERLIES. THEREFORE...THE CYCLONE SHOULD GRADUALLY
TURN MORE TO THE NORTH-NORTHEAST WITH SOME INCREASE IN FORWARD
SPEED. THERE IS GOOD CONFIDENCE IN THE FORECAST BECAUSE THE TRACK
GUIDANCE IS PACKED AND THE OFFICIAL FORECAST IS IN THE MIDDLE OF
THE ENVELOPE. THE ONLY DIFFERENCE IS IN THE FORWARD SPEED SHOWN BY
VARIOUS MODELS...BUT THIS MOSTLY OCCUR AT THE LONG RANGE AS THE
SYSTEM BEGINS THE TRANSITION TO AN EXTRATROPICAL LOW.       

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0300Z 29.1N  66.5W    40 KT
 12HR VT     07/1200Z 30.3N  66.1W    40 KT
 24HR VT     08/0000Z 32.0N  65.2W    45 KT
 36HR VT     08/1200Z 33.7N  64.4W    55 KT
 48HR VT     09/0000Z 36.5N  63.0W    55 KT
 72HR VT     10/0000Z 42.0N  57.5W    55 KT
 96HR VT     11/0000Z 49.5N  46.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/0000Z...ABSORBED BY A LARGER EXTRATROPICAL CYCLONE 
 
$$
FORECASTER AVILA
 

WTNT44 KNHC 070857
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 AM AST SAT AUG 07 2010
 
DATA FROM THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SHOW THAT
COLIN REMAINS POORLY ORGANIZED...WITH THE THE SURFACE CENTER 
DISPLACED NORTH OF THE 850-MB FLIGHT LEVEL CENTER FIX.  THE HIGHEST
FLIGHT LEVEL AND SFMR WINDS SAMPLED BY THE AIRCRAFT WERE 36 KT. 
THE INITIAL INTENSITY WILL BE HELD GENEROUSLY AT 40 KT FOR THIS
PACKAGE...ASSUMING SOME HIGHER WINDS REMAIN IN THE DEEP CONVECTION
TO THE SOUTHEAST OF THE CENTER.
 
THE OUTFLOW HAS BECOME RESTRICTED IN THE NORTHEASTERN QUADRANT OVER
THE PAST FEW HOURS...AND DEEP CONVECTION IS NOW CONFINED TO THE
SOUTHEASTERN QUADRANT.  WHILE THE SHIPS MODEL ANALYZES ONLY ABOUT
10 KT OF SHEAR OVER COLIN...SATELLITE IMAGERY SUGGESTS THAT SHEAR
AND DRY AIR CONTINUE TO INHIBIT DEEP CONVECTION WEST AND NORTH OF
THE CENTER. SHIPS SHOWS THE SHEAR REMAINING LOW FOR THE NEXT 24
HOURS...WHICH MAY ALLOW FOR SOME STRENGTHENING AS COLIN WILL REMAIN
OVER WARM WATERS AND IN A DIVERGENT UPPER-LEVEL ENVIRONMENT. AFTER
48 HOURS...THE SHEAR INCREASES RAPIDLY AND COLIN SHOULD GRADUALLY
WEAKEN AS THE CYCLONE MOVES OVER COOLER WATERS AND BECOMES
EXTRATROPICAL. THE NEW NHC INTENSITY FORECAST IS IN BEST AGREEMENT
WITH ICON.
 
SATELLITE IMAGERY AND DATA FROM THE AIRCRAFT INDICATE THAT COLIN HAS
MOVED VERY SLOWLY NORTHWARD FOR THE PAST SEVERAL HOURS WITH AN
INITIAL MOTION ESTIMATE OF 010/04.  COLIN APPEARS TO BE CAUGHT IN A
REGION OF WEAK STEERING FLOW ON THE WESTERN EDGE OF THE WEAKENING
SUBTROPICAL RIDGE. THE TRACK GUIDANCE IS INSISTENT ON COLIN
ACCELERATING NORTH-NORTHEASTWARD AS THE RIDGE REBUILDS TO THE EAST
AND A LONGWAVE TROUGH MOVES OFF THE COAST OF THE NORTHEASTERN
UNITED STATES. AT 48 HOURS AND BEYOND...AN ACCELERATION TOWARD THE
NORTHEAST IS EXPECTED AS COLIN IS CAUGHT UP IN THE MID-LATITUDE
FLOW. MOST OF THE GUIDANCE IS IN GOOD AGREEMENT ON THE DIRECTION OF
MOTION...BUT THERE IS SOME DISAGREEMENT IN THE FORWARD SPEED. THE
NEW NHC FORECAST IS SLOWER THAN THE PREVIOUS ONE FOR THE FIRST 12
TO 24 HOURS DUE TO THE INITIAL MOTION...AND IS LARGELY AN UPDATE OF
THE PREVIOUS PACKAGE BEYOND THAT TIME...IN BEST AGREEMENT WITH THE
ECMWF.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 29.1N  66.5W    40 KT
 12HR VT     07/1800Z 30.4N  66.0W    40 KT
 24HR VT     08/0600Z 32.3N  65.0W    45 KT
 36HR VT     08/1800Z 34.8N  63.9W    50 KT
 48HR VT     09/0600Z 37.8N  61.9W    55 KT
 72HR VT     10/0600Z 44.0N  54.0W    50 KT
 96HR VT     11/0600Z 51.5N  43.0W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/0600Z...DISSIPATED
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 070901
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  14...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 AM AST SAT AUG 07 2010

CORRECTED FOR 120 HOUR FORECAST STATUS IN TABLE
 
DATA FROM THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT SHOW THAT
COLIN REMAINS POORLY ORGANIZED...WITH THE THE SURFACE CENTER 
DISPLACED NORTH OF THE 850-MB FLIGHT LEVEL CENTER FIX.  THE HIGHEST
FLIGHT LEVEL AND SFMR WINDS SAMPLED BY THE AIRCRAFT WERE 36 KT. 
THE INITIAL INTENSITY WILL BE HELD GENEROUSLY AT 40 KT FOR THIS
PACKAGE...ASSUMING SOME HIGHER WINDS REMAIN IN THE DEEP CONVECTION
TO THE SOUTHEAST OF THE CENTER.
 
THE OUTFLOW HAS BECOME RESTRICTED IN THE NORTHEASTERN QUADRANT OVER
THE PAST FEW HOURS...AND DEEP CONVECTION IS NOW CONFINED TO THE
SOUTHEASTERN QUADRANT.  WHILE THE SHIPS MODEL ANALYZES ONLY ABOUT
10 KT OF SHEAR OVER COLIN...SATELLITE IMAGERY SUGGESTS THAT SHEAR
AND DRY AIR CONTINUE TO INHIBIT DEEP CONVECTION WEST AND NORTH OF
THE CENTER. SHIPS SHOWS THE SHEAR REMAINING LOW FOR THE NEXT 24
HOURS...WHICH MAY ALLOW FOR SOME STRENGTHENING AS COLIN WILL REMAIN
OVER WARM WATERS AND IN A DIVERGENT UPPER-LEVEL ENVIRONMENT. AFTER
48 HOURS...THE SHEAR INCREASES RAPIDLY AND COLIN SHOULD GRADUALLY
WEAKEN AS THE CYCLONE MOVES OVER COOLER WATERS AND BECOMES
EXTRATROPICAL. THE NEW NHC INTENSITY FORECAST IS IN BEST AGREEMENT
WITH ICON.
 
SATELLITE IMAGERY AND DATA FROM THE AIRCRAFT INDICATE THAT COLIN HAS
MOVED VERY SLOWLY NORTHWARD FOR THE PAST SEVERAL HOURS WITH AN
INITIAL MOTION ESTIMATE OF 010/04.  COLIN APPEARS TO BE CAUGHT IN A
REGION OF WEAK STEERING FLOW ON THE WESTERN EDGE OF THE WEAKENING
SUBTROPICAL RIDGE. THE TRACK GUIDANCE IS INSISTENT ON COLIN
ACCELERATING NORTH-NORTHEASTWARD AS THE RIDGE REBUILDS TO THE EAST
AND A LONGWAVE TROUGH MOVES OFF THE COAST OF THE NORTHEASTERN
UNITED STATES. AT 48 HOURS AND BEYOND...AN ACCELERATION TOWARD THE
NORTHEAST IS EXPECTED AS COLIN IS CAUGHT UP IN THE MID-LATITUDE
FLOW. MOST OF THE GUIDANCE IS IN GOOD AGREEMENT ON THE DIRECTION OF
MOTION...BUT THERE IS SOME DISAGREEMENT IN THE FORWARD SPEED. THE
NEW NHC FORECAST IS SLOWER THAN THE PREVIOUS ONE FOR THE FIRST 12
TO 24 HOURS DUE TO THE INITIAL MOTION...AND IS LARGELY AN UPDATE OF
THE PREVIOUS PACKAGE BEYOND THAT TIME...IN BEST AGREEMENT WITH THE
ECMWF.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/0900Z 29.1N  66.5W    40 KT
 12HR VT     07/1800Z 30.4N  66.0W    40 KT
 24HR VT     08/0600Z 32.3N  65.0W    45 KT
 36HR VT     08/1800Z 34.8N  63.9W    50 KT
 48HR VT     09/0600Z 37.8N  61.9W    55 KT
 72HR VT     10/0600Z 44.0N  54.0W    50 KT
 96HR VT     11/0600Z 51.5N  43.0W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/0600Z...ABSORBED BY LARGE EXTRATROPICAL CYCLONE 
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 071440
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 AM AST SAT AUG 07 2010
 
 
VISIBLE SATELLITE IMAGES INDICATE THAT THE CLOUD PATTERN CONTINUES
TO BE DISORGANIZED AND CONSISTS OF A TIGHT SWIRL OF LOW CLOUDS WITH
SOME SHAPELESS CONVECTION TO THE EAST AND SOUTHEAST OF THE CENTER.
GIVEN THE CURRENT SATELLITE PRESENTATION...THE INITIAL INTENSITY
HAS BEEN REDUCED TO 35 KNOTS.  THESE WINDS ARE PROBABLY CONFINED TO
RAINBANDS ON THE EASTERN PORTION OF THE CIRCULATION. THE STRONG
WESTERLY SHEAR OBSERVED YESTERDAY HAS RELAXED A LITTLE BIT AND THE
CYCLONE IS LOCATED UNDER A SMALL UPPER-LEVEL RIDGE BETWEEN
TWO LARGER UPPER LEVEL LOWS. ALTHOUGH THERE ARE NO INDICATIONS THAT
STRENGTHENING IS ABOUT TO OCCUR...THE OBSERVED UPPER-LEVEL PATTERN
COULD ALLOW A SLIGHT INTENSIFICATION TO BEGIN LATER TODAY. BOTH THE
GFDL AND HWRF MODELS INSIST ON SOME STRENGTHENING BUT IT OCCURS BY
THE LATTER PART OF THE FORECAST WHEN EXTRATROPICAL TRANSITION
SHOULD BEGIN. COLIN IS FORECAST TO BECOME EXTRATROPICAL BY 72 HOURS
AS IT MOVES OVER COOLER WATERS.
 
UNEXPECTEDLY...COLIN HAS BARELY MOVED DURING THE PAST FEW HOURS AS
IT BECAME EMBEDDED WITHIN LIGHT STEERING CURRENTS. NONE OF THE
GUIDANCE FORECAST THE CURRENT SLOW MOTION AND IN FACT...MOST OF THE
MODELS INSIST ON RECURVATURE SOON AND A MOTION TOWARD THE
NORTH-NORTHEAST WITH AN INCREASE IN FORWARD SPEED. THIS
ACCELERATION TO THE NORTH-NORTHEAST APPEARS TO BE REALISTIC AS A
LARGE TROUGH AMPLIFIES OVER THE EASTERN UNITED STATES BRINGING A
STRONGER SOUTHWESTERLY STEERING FLOW OVER THE STORM. THIS IS THE
SCENARIO FOLLOWED IN THE OFFICIAL FORECAST.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/1500Z 29.0N  66.4W    35 KT
 12HR VT     08/0000Z 30.7N  66.2W    35 KT
 24HR VT     08/1200Z 33.0N  65.5W    40 KT
 36HR VT     09/0000Z 35.5N  64.0W    45 KT
 48HR VT     09/1200Z 39.0N  60.5W    50 KT
 72HR VT     10/1200Z 46.5N  50.0W    50 KT...POST-TROP/EXTRATROP
 96HR VT     11/1200Z 55.0N  41.5W    45 KT...POST-TROP/EXTRATROP
120HR VT     12/1200Z...ABSORBED BY A LARGE EXTRATROPICAL LOW
 
$$
FORECASTER AVILA
 

WTNT44 KNHC 072032
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 PM AST SAT AUG 07 2010
 
IT HAS BEEN INTERESTING TO OBSERVE THE EVOLUTION OF THE LOW-LEVEL
CENTER AND THE DEEP CONVECTION TODAY. DURING THE MORNING THE
LOW-LEVEL CENTER WAS COMPLETELY EXPOSED AND AS NEW CONVECTION
FORMED...THE CENTER SHIFTED EASTWARD AND BECAME TUCKED INTO THE
THUNDERSTORM ACTIVITY. EVEN THE OUTFLOW BEGAN TO EXPAND...GIVING THE
IMPRESSION THAT THERE WAS A DEVELOPING TREND. HOWEVER...DATA
FROM THE AIR FORCE RECONNAISSANCE PLANE INDICATE THAT THE CENTRAL
PRESSURE HAS RISEN AND THE WINDS HAVE NOT INCREASED. IN FACT...THE
INITIAL INTENSITY IS KEPT GENEROUSLY AT 35 KNOTS BASED ON ONE
SFMR OBSERVATION OF 34 KNOTS. SHIPS MODEL AS WELL AS THE GFDL/HWRF
PAIR SUGGEST THAT COLIN WILL AT LEAST KEEP ITS TROPICAL STORM
STATUS. GIVEN THE EXPECTED LOW SHEAR FOR A DAY OR SO...THE OFFICIAL
FORECAST ALSO KEEPS COLIN AS A TROPICAL STORM A LITTLE LONGER.
HOWEVER...THIS FORECAST IS HIGHLY UNCERTAIN.  AFTER 48
HOURS...COLIN IS EXPECTED TO BECOME EXTRATROPICAL AND ABSORBED BY A
LARGER MID-LATITUDE LOW.  IN FACT...MOST OF THE MODELS DO NOT EVEN
TRACK COLIN BEYOND 3 DAYS.
 
THE CENTER HAS BEEN MEANDERING ALL MORNING BUT LATEST VISIBLE IMAGES
AND DATA FROM THE RECONNAISSANCE PLANE INDICATE THAT COLIN IS
BEGINNING A SLOW NORTHERLY TRACK AT ABOUT 6 KNOTS OR LESS. THE
CYCLONE IS EXPECTED TO CONTINUE AROUND THE WESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE FOR THE NEXT DAY OR TWO. IT SHOULD THEN ACCELERATE
TO THE NORTHEAST EMBEDDED WITHIN THE SOUTHWESTERLY FLOW AHEAD OF A
TROUGH OVER THE EASTERN UNITED STATES. THE TRACK GUIDANCE
CONSISTENTLY TAKES COLIN NORTHWARD AND INDEED ALL MODELS BRING THE
CENTER JUST WEST OF BERMUDA IN ABOUT 24 HOURS...AND SO DOES THE
OFFICIAL FORECAST. ON THIS TRACK...MOST OF THE SHOWERS AND SQUALLS 
ASSOCIATED WITH COLIN WILL BE AFFECTING BERMUDA SINCE THEY ARE IN
THE EASTERN SEMICIRCLE. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      07/2100Z 29.4N  65.7W    35 KT
 12HR VT     08/0600Z 30.3N  65.5W    35 KT
 24HR VT     08/1800Z 32.2N  65.3W    40 KT
 36HR VT     09/0600Z 35.0N  65.0W    45 KT
 48HR VT     09/1800Z 38.5N  62.5W    45 KT
 72HR VT     10/1800Z 45.0N  50.0W    45 KT...POST-TROP/EXTRATROP
 96HR VT     11/1800Z...DISSIPATED
 
$$
FORECASTER AVILA
 

WTNT44 KNHC 080233
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 PM AST SAT AUG 07 2010
 
THE CENTER OF COLIN IS VERY DIFFICULT TO LOCATE THIS EVENING...EVEN
WITH THE HELP OF A TRMM MICROWAVE OVERPASS.  THE BEST ESTIMATE IS
THAT IT IS NORTH OF THE CURRENTLY SHRINKING AREA OF CONVECTION. 
SATELLITE INTENSITY ESTIMATES ARE 35 KT FROM TAFB AND 30 KT FROM
SAB.  BASED ON THIS...THE SYSTEM REMAINS A 35 KT TROPICAL
STORM...AND THIS COULD BE GENEROUS.  COLIN IS STRUGGLING TO
MAINTAIN ITSELF IN A SEEMINGLY FAVORABLE LOW-SHEAR ENVIRONMENT...
AND ONE POSSIBLE REASON IS A TONGUE OF LOW PRECIPITABLE WATER AIR
SEEN INTRUDING INTO THE CIRCULATION IN AN AMSR-E OVERPASS.
 
THE INITIAL MOTION IS A HIGHLY UNCERTAIN 015/3.  IN THE SHORT
TERM...COLIN APPEARS TO BE TRAPPED BETWEEN LOW-LEVEL RIDGES TO THE
EAST AND WEST...AND THIS COULD BE A REASON FOR THE CURRENT SLOW
MOTION.  IN THE LONGER TERM...A DEEP-LAYER TROUGH AND ASSOCIATED
FRONTAL SYSTEM MOVING OFF THE EAST COAST OF THE UNITED STATES
SHOULD STEER THE STORM NORTHWARD AND THEN NORTHEASTWARD INTO THE
WESTERLIES.  THE TRACK GUIDANCE REMAINS IN GOOD AGREEMENT WITH
THIS...AND THE NEW TRACK FORECAST IS SIMILAR TO...BUT SLOWER
THAN...THE PREVIOUS FORECAST.  IT SHOULD BE NOTED THAT SEVERAL OF
THE DYNAMICAL MODELS NOW FORECAST COLIN TO TAKE 24 OR MORE HOURS
BEFORE PASSING BERMUDA.
 
THE INTENSITY GUIDANCE AGREES THAT COLIN SHOULD STRENGTHEN DURING
THE NEXT 36 HR.  GIVEN THE CURRENT INTENSITY TREND AND LACK OF
ORGANIZATION...IT IS LIKELY THAT ANY STRENGTHENING WILL BE SLOWER
THAN THE GUIDANCE.  THE NEW INTENSITY FORECAST IS THE SAME AS THE
PREVIOUS FORECAST...WITH COLIN SLOWLY STRENGTHENING TO 45 KT IN 48
HR.  AN ALTERNATIVE SCENARIO IS THAT COLIN DOES NOT STRENGTHEN AND
REMAINS AT BEST A MINIMAL TROPICAL STORM AS IT MOVES NORTHWARD. 
REGARDLESS OF THE EXACT INTENSITY...COLIN SHOULD BEGIN
EXTRATROPICAL TRANSITION AT AROUND 48 HR AND COMPLETE IT BY 72 HR. 
THE CYCLONE IS THEN LIKELY TO BE ABSORBED BY A LARGER EXTRATROPICAL
LOW BY 96 HR.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0300Z 29.7N  65.6W    35 KT
 12HR VT     08/1200Z 30.7N  65.5W    35 KT
 24HR VT     09/0000Z 32.4N  65.5W    40 KT
 36HR VT     09/1200Z 34.7N  64.9W    45 KT
 48HR VT     10/0000Z 38.1N  62.6W    45 KT
 72HR VT     11/0000Z 47.5N  51.0W    45 KT...POST-TROP/EXTRATROP
 96HR VT     12/0000Z...ABSORBED BY EXTRATROPICAL LOW
 
$$
FORECASTER BEVEN
 

WTNT44 KNHC 080841
TCDAT4
TROPICAL STORM COLIN DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 AM AST SUN AUG 08 2010
 
THE LOW-LEVEL CENTER OF COLIN REMAINS DISPLACED TO THE NORTH OF THE
REMAINING DEEP CONVECTION...AS SHEAR AND DRY AIR CONTINUE TO
INHIBIT CONVECTIVE DEVELOPMENT OVER AND WEST OF THE CENTER. THE
INITIAL INTENSITY IS HELD AT 35 KT FOR THIS ADVISORY...IN AGREEMENT
WITH A DVORAK ESTIMATE OF 2.5 FROM TAFB. THE ENVIRONMENT AROUND
COLIN DOES NOT APPEAR CONDUCIVE FOR MORE THAN MODEST STRENGTHENING
OVER THE NEXT COUPLE OF DAYS...AND THE OFFICIAL FORECAST IS SIMILAR
TO THE PREVIOUS ONE...SHOWING SOME SLOW STRENGTHENING UNTIL
EXTRATROPICAL TRANSITION OCCURS IN ABOUT 3 DAYS.
 
THE CENTER IS DIFFICULT TO PINPOINT IN THE MULTI-CHANNEL INFRARED
IMAGERY...BUT THE INITIAL MOTION ESTIMATE IS A LITTLE FASTER
NOW...TOWARD 005 DEGREES AT 5 KT. COLIN FINALLY APPEARS TO BE
RESPONDING TO THE DEEP LAYER TROUGH MOVING OFFSHORE OF THE U.S.
EAST COAST...AND MOST OF THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON
THE GENERAL SCENARIO OF AN ACCELERATION TOWARD THE NORTH-NORTHEAST
AND NORTHEAST AHEAD OF THE TROUGH. HOWEVER...THE FORWARD SPEED OF
MOST OF THE GUIDANCE HAS TRENDED SLOWER WITH THIS CYCLE. THE
OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS ONE...BUT TRENDS
SLOWER AFTER 12 HOURS. COLIN SHOULD UNDERGO EXTRATROPICAL
TRANSITION BY 72 HOURS BEFORE BEING ABSORBED BY A LARGER
EXTRATROPICAL CYCLONE IN ABOUT 4 DAYS. IT IS POSSIBLE THAT THE
CENTER OF COLIN COULD BECOME ELONGATED AND OPEN UP INTO A TROUGH AS
IT DECOUPLES FROM THE MID-LEVEL CENTER...AS SUGGESTED BY THE UKMET
MODEL. IF THIS OCCURS...COLIN COULD DISSIPATE EARLIER THAN
INDICATED HERE.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/0900Z 30.7N  65.6W    35 KT
 12HR VT     08/1800Z 31.7N  65.6W    35 KT
 24HR VT     09/0600Z 33.4N  65.5W    40 KT
 36HR VT     09/1800Z 36.0N  64.8W    40 KT
 48HR VT     10/0600Z 38.9N  61.9W    45 KT
 72HR VT     11/0600Z 46.0N  52.0W    45 KT...POST-TROP/EXTRATROP
 96HR VT     12/0600Z...ABSORBED BY EXTRATROPICAL LOW
 
$$
FORECASTER BRENNAN
 

WTNT44 KNHC 081443
TCDAT4
TROPICAL DEPRESSION COLIN DISCUSSION NUMBER  19
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
1100 AM AST SUN AUG 08 2010
 
VISIBLE SATELLITE IMAGERY...RADAR DATA AND SURFACE OBSERVATIONS FROM
BERMUDA INDICATE THAT THE LOW-LEVEL CIRCULATION OF COLIN IS
BECOMING ELONGATED NORTH TO SOUTH AND THAT THE CONVECTIVE ACTIVITY
HAS LITTLE...IF ANY...ORGANIZATION. DVORAK DATA T-NUMBERS FROM SAB
AND TAFB HAVE DECREASED TO BELOW TROPICAL STORM STRENGTH. BASED ON
THE ABOVE...COLIN IS DOWNGRADED TO A TROPICAL DEPRESSION AT THIS
TIME.   

ALTHOUGH THE INTENSITY GUIDANCE STILL SHOWS STRENGTHENING...THIS
SEEMS UNLIKELY AS SHEAR AND DRY AIR CONTINUE TO TAKE A TOLL ON
COLIN. THE NEW INTENSITY FORECAST KEEPS COLIN AS A TROPICAL
DEPRESSION UNTIL DISSIPATION. IF THE CIRCULATION CONTINUES TO
ELONGATE...IT IS POSSIBLE THAT COLIN WILL DEGENERATE INTO A TROUGH
OF LOW PRESSURE LATER TODAY.  THIS SCENARIO IS SUPPORTED BY MOST OF
THE GLOBAL MODELS.
 
COLIN IS MOVING A LITTLE FASTER TOWARD THE NORTH OR 360 DEGREES
AT 10 KT.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT ON TAKING COLIN
OR ITS REMNANTS NORTHWARD...THEN NORTHEASTWARD AHEAD OF A DEEP LAYER
TROUGH ALONG THE EAST COAST OF THE UNITED STATES.  THE NEW TRACK
FORECAST IS VIRTUALLY AN UPDATE OF THE PREVIOUS NHC ADVISORY.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/1500Z 32.0N  65.6W    30 KT
 12HR VT     09/0000Z 33.3N  65.5W    30 KT
 24HR VT     09/1200Z 35.3N  64.8W    30 KT
 36HR VT     10/0000Z 37.9N  63.0W    30 KT
 48HR VT     10/1200Z 41.2N  58.8W    30 KT
 72HR VT     11/1200Z...DISSIPATED
 
$$
FORECASTER BROWN
 

WTNT44 KNHC 082032
TCDAT4
TROPICAL DEPRESSION COLIN DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL042010
500 PM AST SUN AUG 08 2010
 
SATELLITE IMAGERY AND RADAR DATA FROM BERMUDA INDICATE THAT COLIN
HAS DEGENERATED INTO A TROUGH OF LOW PRESSURE AND THIS WILL BE THE
LAST NHC ADVISORY ON THIS SYSTEM.  THE REMNANT OF COLIN IS EXPECTED
TO MOVE NORTH-NORTHEASTWARD AHEAD OF A DEEP-LAYER TROUGH EXITING
THE EAST COAST OF THE UNITED STATES.  ENVIRONMENTAL CONDITIONS ARE
FORECAST TO REMAIN PROHIBITIVE FOR REGENERATION INTO A TROPICAL
CYCLONE.
 
SOME ELEVATED WEATHER OBSERVING SITES IN BERMUDA HAVE RECORDED WIND
GUSTS TO TROPICAL STORM FORCE NEAR PASSING SHOWERS TODAY. THESE
WIND GUSTS SHOULD DECREASE TONIGHT AS THE REMNANT OF COLIN MOVES
AWAY FROM THE ISLAND.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      08/2100Z 32.9N  65.6W    25 KT...DISSIPATED
 12HR VT     09/0600Z...DISSIPATED
 
$$
FORECASTER BROWN
 

