[Tropical] Tropical Cyclone Discussion

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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


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