Tropical Depression TWENTY-SEVEN

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TROPICAL DEPRESSION TWENTY-SEVEN DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
10 PM EST SUN NOV 13 2005
 
SATELLITE IMAGERY... SURFACE OBSERVATIONS... AND RADAR DATA FROM
MARTINIQUE INDICATE THUNDERSTORM ACTIVITY HAS CONTINUED TO INCREASE
AND BECOME MUCH BETTER ORGANIZED IN ASSOCIATION WITH THE LARGE LOW
PRESSURE SYSTEM LOCATED OVER THE SOUTHEASTERN CARIBBEAN SEA. AT
14/0000Z... ST. LUCIA REPORTED SUSTAINED SOUTHEAST WINDS OF 29 KT
...AND SHIP ZCBU6 LOCATED JUST OFF THE SOUTHWEST COAST OF REPORTED
SOUTHEAST WINDS OF 27 KT. SURFACE PRESSURE ANALYSES AT 00Z SUPPORT
A MINIMUM CENTRAL PRESSURE OF AT LEAST 1007 MB... CORRESPONDING TO
APPROXIMATELY 32 KT. RADAR DATA FROM MARTINIQUE SHOW CURVED
CONVECTIVE BANDING HAS DEVELOPED NEAR AND EAST OF THE LOW-LEVEL
CENTER... WHICH IS COINCIDENT WITH THE LARGE AREA OF -80C TO -82C
CONVECTIVE TOPS THAT HAVE BEEN NOTED IN INFRARED SATELLITE IMAGERY
SINCE 22Z. THEREFORE... THE LOW PRESSURE SYSTEM HAS BEEN UPGRADED
TO TROPICAL DEPRESSION TWENTY-SEVEN.
 
THE INITIAL MOTION ESTIMATE IS 300/09. THE DEPRESSION IS STILL IN
THE FORMATIVE STAGES... SO THERE MAY SOME ERRATIC MOTION FOR THE
NEXT 24 HOURS UNTIL THE CONVECTION BECOMES MORE CONSOLIDATED AROUND
THE CENTER. HOWEVER... THE GENERAL TREND BY THE VARIOUS GLOBAL
MODELS AND THE GFDL MODEL IS FOR THE CYCLONE TO PROPAGATE
WEST-NORTH OR NORTHWESTWARD FOR THE NEXT 24-36 HOURS TOWARD A
WEAKNESS IN THE SUBTROPICAL RIDGE LOCATED OVER THE NORTHEASTERN
CARIBBEAN SEA AND NORTHERN LESSER ANTILLES. AFTER THAT... THE
UPPER-LEVEL TROUGH THAT HAS CREATED THE WEAKNESS IS FORECAST TO
SLOWLY WEAKEN AND LIFT OUT TO THE NORTHEAST... ALLOWING THE RIDGE
TO BUILD EASTWARD TO THE NORTH AND NORTHEAST OF THE CYCLONE. THIS
SHOULD ACT TO THE DRIVE THE STORM WESTWARD ACROSS THE CENTRAL
CARIBBEAN SEA IN THE 48-120 HOUR FORECAST PERIODS. THE OFFICIAL
FORECAST TRACK IS CLOSE TO A BLEND OF THE NOGAPS... UKMET... AND
GFDL MODELS.
 
UPPER-LEVEL WESTERLY SHEAR OF 20-25 KT IS EXPECTED TO CONTINUE
ACROSS THE CYCLONE FOR THE NEXT 36-48 HOURS... WHICH SHOULD INHIBIT
ANY RAPID DEVELOPMENT DURING THAT TIME. AFTERWARDS... THE SHEAR IS
EXPECTED TO DECREASE TO LESS THAN 10 KT... AT WHICH TIME MORE
SIGNIFICANT DEVELOPMENT COULD OCCUR. THE SHIPS MODEL BRINGS THE
INTENSITY UP TO 66 KT IN 108 HOURS... WHEREAS THE GFDL MAKES THE
CYCLONE A 112-KT MAJOR HURRICANE AT THE SAME TIME. IT SHOULD BE
POINTED OUT THAT THE SHIPS INTENSITY MODEL FORECAST WAS BASED ON
THE MEDIUM BAM MODEL FORECAST TRACK... WHICH TAKES THE STORM
SOUTHWESTWARD ACROSS COLOMBIA WHERE UPPER-LEVEL WINDS ARE EXPECTED
TO BE MUCH STRONGER THAN THEY ARE OVER THE CENTRAL CARIBBEAN SEA.
IT IS QUITE POSSIBLE THAT THIS SYSTEM COULD END UP STRONGER THAN
INDICATED AFTER 72 HOURS... GIVEN THE MUCH LOWER VERTICAL WIND
SHEAR THAT THE GLOBAL MODELS ARE FORECASTING TO BE IN PLACE OVER
THE 96- AND 120-HOUR OFFICIAL FORECAST POSITIONS.
 
FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/0300Z 13.5N  62.7W    30 KT
 12HR VT     14/1200Z 14.3N  64.1W    30 KT
 24HR VT     15/0000Z 15.3N  65.7W    35 KT
 36HR VT     15/1200Z 15.9N  67.2W    35 KT
 48HR VT     16/0000Z 16.1N  68.8W    40 KT
 72HR VT     17/0000Z 16.0N  72.2W    45 KT
 96HR VT     18/0000Z 16.0N  75.5W    50 KT
120HR VT     19/0000Z 16.0N  79.0W    60 KT
 
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