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Tropical Depression TWENTY-SEVEN (Text)

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TROPICAL DEPRESSION TWENTY-SEVEN DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
4 PM EST TUE NOV 15 2005
 
THE AIR FORCE RECONNAISSANCE AIRCRAFT CONFIRMS WHAT THE SATELLITE
IMAGERY HAS BEEN INDICATING TODAY... THAT THE DEPRESSION REMAINS
QUITE POORLY ORGANIZED.  THE CIRCULATION IS ELONGATED
WEST-SOUTHWEST TO EAST-NORTHEAST... WITH ONLY VERY WEAK WESTERLY
WINDS ON THE SOUTHWESTERN SIDE AND A BROAD AREA OF WEAK WINDS
AROUND THE ESTIMATED CENTER LOCATION.  THE LOWEST PRESSURE REPORTED
BY THE AIRCRAFT HAS BEEN 1006 MB.  EVEN THOUGH THE CIRCULATION IS A
BIT SLOPPY... SOME DEEP CONVECTION REMAINS CLOSE BY... BUT ONLY ON
THE EASTERN SIDE DUE TO CONTINUING WESTERLY SHEAR.  PERHAPS
GENEROUSLY... THE SYSTEM REMAINS A DEPRESSION WITH 30 KT WINDS...
BASED ON FLIGHT LEVEL WINDS OF 41 KT... A FEW SHIP REPORTS OF ABOUT
30 KT IN THE SOUTHEASTERN QUADRANT... AND DVORAK SATELLITE
ESTIMATES.
 
THE CIRCULATION CENTER IS MOVING JUST NORTH OF DUE WEST AT ABOUT 11
KT.  THE TRACK FORECAST REMAINS RELATIVELY STRAIGHTFORWARD THROUGH
ABOUT 48 HOURS... AS A LOW- TO MID-LEVEL RIDGE IS FORECAST TO
PERSIST OVER THE EXTREME WESTERN ATLANTIC AND CONTINUE TO DRIVE THE
CYCLONE WESTWARD.  AFTER THAT... THERE ARE SEVERAL FACTORS
COMPLICATING THE TRACK FORECAST.  DYNAMICAL MODELS AGREE THE
WESTERN ATLANTIC RIDGE WILL BREAK DOWN AND CAUSE THE TROPICAL
CYCLONE TO MOVE MORE SLOWLY ON DAYS 3-5.  HOWEVER... EACH MODEL
FORECASTS A DIFFERENT EVOLUTION OF THE BROAD LOW CURRENTLY OVER THE
SOUTHWESTERN CARIBBEAN... AND EACH SHOWS AN UPPER-LEVEL TROUGH OVER
THE EASTERN UNITED STATES BY THAT TIME... BUT WITH VARYING STRENGTH
OVER THE GULF OF MEXICO.  THE TROPICAL CYCLONE WILL MOST LIKELY
BECOME EMBEDDED WITHIN WEAK STEERING CURRENTS BETWEEN THESE TWO
FEATURES... ALTHOUGH ONE COULD END UP HAVING MORE INFLUENCE THAN
THE OTHER.  MOST OF THE MODELS FAVOR A SLOW NORTHWARD COMPONENT TO
THE MOTION ON DAYS 4 AND 5.  THE NEW OFFICIAL FORECAST FOLLOWS THIS
SCENARIO AND IS FASTER THAN THE PREVIOUS ADVISORY THROUGH 72
HOURS... THEN SIMILARLY SLOW THEREAFTER.

ALTHOUGH THE SYSTEM IS BARELY HANGING ON TO TROPICAL CYCLONE
STATUS... ITS ENVIRONMENT SHOULD GRADUALLY BECOME MORE CONDUCIVE
FOR STRENGTHENING.  IF THE CYCLONE SURVIVES THE NEXT 24 HOURS OR SO
OF CONTINUED WESTERLY SHEAR... THE DEVELOPING UPPER-LEVEL
ANTICYCLONE OVER THE WEST-CENTRAL CARIBBEAN WILL CREATE A WEAKER
SHEAR ENVIRONMENT.  THIS COULD ALLOW FOR A TROPICAL STORM TO
DEVELOP IN 24-36 HOURS AS SUGGESTED BY THE SHIPS GUIDANCE.  SHIPS
PEAKS AT 55 KT IN ABOUT 72 HOURS... WHILE THE GFDL PEAKS AT 77 KT A
LITTLE LATER.  THE OFFICIAL FORECAST IS IN BETWEEN AND STILL
ANTICIPATES DEVELOPMENT INTO A HURRICANE... ALTHOUGH A WEAKENING
TREND IS NOW INTRODUCED AT THE END OF THE FORECAST IN ANTICIPATION
OF INCREASING SOUTHWESTERLY SHEAR IN ADVANCE OF THE TROUGH EXPECTED
TO DEVELOP OVER THE GULF OF MEXICO.
 
 
FORECASTER KNABB
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      15/2100Z 14.8N  69.0W    30 KT
 12HR VT     16/0600Z 14.9N  70.7W    30 KT
 24HR VT     16/1800Z 15.0N  73.0W    35 KT
 36HR VT     17/0600Z 15.2N  75.2W    40 KT
 48HR VT     17/1800Z 15.4N  77.5W    45 KT
 72HR VT     18/1800Z 15.5N  81.0W    55 KT
 96HR VT     19/1800Z 16.0N  82.0W    65 KT
120HR VT     20/1800Z 16.5N  82.5W    60 KT
 
 
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