Tropical Depression TWENTY-SEVEN

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TROPICAL DEPRESSION TWENTY-SEVEN DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
10 AM EST MON NOV 14 2005
 
WESTERLY SHEAR CONTINUES TO DISPLACE MOST OF THE CONVECTION TO THE
EAST OF THE SOMEWHAT ILL-DEFINED LOW-LEVEL CIRCULATION. HOWEVER...
THE CONVECTION IS STILL RATHER DEEP AND PERSISTENT... AND IT
APPEARS TO BE IN THE PROCESS OF FORMING A CURVED BAND THAT COULD
SOON WRAP AROUND THE LOW LEVEL CENTER. THE CYCLONE APPEARS CLOSE TO
BECOMING A TROPICAL STORM... AS SUGGESTED BY DVORAK INTENSITY
ESTIMATES OF 30-35 KT... BUT THE ADVISORY INTENSITY IS MAINTAINED
AT 30 KT TO WAIT FOR A LITTLE MORE ORGANIZATION IN THE CONVECTIVE
PATTERN.
 
THE DEPRESSION IS MOVING A LITTLE MORE SLOWLY THAN BEFORE...
PRESUMABLY DUE TO THE EFFECTS OF THE WESTERLY SHEAR. WHILE THE
INITIAL MOTION OF 295/6 IS STILL A BIT UNCERTAIN DUE TO THE POOR
ORGANIZATION OF THE SYSTEM... IT APPEARS QUITE LIKELY THE CYCLONE
WILL GENERALLY MOVE WESTWARD THROUGHOUT THE FIVE-DAY FORECAST
PERIOD. A MID-TROPOSPHERIC RIDGE IS FORECAST BY THE DYNAMICAL
MODELS TO PERSIST OVER THE WESTERN ATLANTIC AND INDUCE EASTERLY
FLOW OVER THE CARIBBEAN. THE RIDGE WILL PROBABLY WEAKEN LATE IN THE
FORECAST PERIOD AS A MID-LATITUDE TROUGH DEEPENS OVER THE EASTERN
UNITED STATES... WHICH WOULD SERVE TO SLOW THE CYCLONE DOWN BUT NOT
BE ENOUGH TO PICK IT UP OUT OF THE CARIBBEAN SEA. INDEED... ALL OF
THE TRACK GUIDANCE KEEPS THE CYCLONE IN THE CARIBBEAN SEA THROUGH
FIVE DAYS... ALTHOUGH SOME DISAGREEMENT EXISTS ON THE LATITUDE AT
WHICH THE CYCLONE WILL MOVE... MOSTLY DUE TO DIFFERENCES AMONG THE
MODELS IN HOW STRONG THE CIRCULATION WILL BECOME. THE OFFICIAL
FORECAST IS JUST A LITTLE SOUTH OF THE PREVIOUS ADVISORY TO NUDGE
TOWARD THE MODEL CONSENSUS.
 
THE UPPER-LEVEL PATTERN OVER THE CARIBBEAN THIS MORNING IS RATHER
ZONAL... WITH MUCH STRONGER WESTERLIES NORTH OF 15N THAN TO THE
SOUTH.  NONETHELESS... THE SHEAR APPEARS TO BE STRONG ENOUGH OVER
THE DEPRESSION TO KEEP ITS SHORT-TERM DEVELOPMENT GRADUAL. THE
MODELS FORECAST THE PATTERN TO BECOME MORE AMPLIFIED... WITH AN
UPPER-LEVEL ANTICYCLONE FORMING OVER THE WEST-CENTRAL CARIBBEAN IN
THE NEXT 2-3 DAYS. IF THE DEPRESSION CONTINUES TO SNEAK TO THE
SOUTH OF THE STRONGER WESTERLIES AND BECOMES SITUATED BENEATH THE
ANTICYCLONE... IT COULD HAVE AN OPPORTUNITY TO STRENGTHEN. THE
OCEAN TEMPERATURES DO NOT PROVIDE ANY LIMITING FACTOR... SO THE
INTENSITY FORECAST HINGES LARGELY ON HOW SHEAR IMPACTS THE TROPICAL
CYCLONE. THE SHIPS GUIDANCE BASED ON GFS MODEL FIELDS DIAGNOSES
SHEAR OF 25-30 KT FOR THE NEXT COUPLE OF DAYS AND DOES NOT FORECAST
A TROPICAL STORM UNTIL 36 HOURS. IT THEN FORECASTS A STORM NO
STRONGER THAN ABOUT 50 KT IN THE NEXT FIVE DAYS... BUT IT COULD BE
OVERESTIMATING THE IMPACTS OF SHEAR... ESPECIALLY IF THE CYCLONE
ENDS UP DIRECTLY BENEATH THE ANTICYCLONE. THE GFDL CONTINUES TO
FORECAST INTENSIFICATION TO A HURRICANE IN ABOUT THREE DAYS... WITH
THE 06Z RUN PEAKING AT 110 KT IN ABOUT FOUR DAYS. GIVEN THE
DIFFERENCE IN THE GUIDANCE ON A SYSTEM STILL IN THE FORMATIVE
STAGES... THE INTENSITY FORECAST IS HIGHLY UNCERTAIN. THE NEW
OFFICIAL FORECAST IS ADJUSTED ONLY SLIGHTLY UPWARD FROM THE
PREVIOUS ADVISORY AND IS IN BETWEEN THE SHIPS AND GFDL.
 
FORECASTER KNABB
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/1500Z 13.8N  63.6W    30 KT
 12HR VT     15/0000Z 14.4N  64.8W    35 KT
 24HR VT     15/1200Z 15.1N  66.6W    40 KT
 36HR VT     16/0000Z 15.4N  68.4W    40 KT
 48HR VT     16/1200Z 15.4N  70.4W    45 KT
 72HR VT     17/1200Z 15.5N  74.0W    50 KT
 96HR VT     18/1200Z 15.5N  77.5W    60 KT
120HR VT     19/1200Z 15.5N  80.0W    65 KT
 
 
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