[Tropical] Tropical Cyclone Discussion

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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

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