071 
 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