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Tropical Depression TWENTY

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TROPICAL DEPRESSION TWENTY DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT SAT OCT 01 2005
 
AIR FORCE RECON AIRCRAFT THIS AFTERNOON FOUND A SMALL SURFACE
CIRCULATION SOUTHWEST OF WHERE SATELLITE AND SURFACE OBSERVATIONS
SUGGEST THE LARGER-SCALE CENTER OF ROTATION IS LOCATED. RECENT
OBSERVATIONS FROM NOAA BUOY 42056 ALSO INDICATE VEERING SURFACE
WINDS... WHICH SUGGESTS THAT ANOTHER SMALL-SCALE CIRCULATION MAY BE
PASSING JUST SOUTHWEST OF THE BUOY. FLIGHT-LEVEL WINDS AT 850 MB
SUGGEST THAT A BROADER CIRCULATION CENTER IS EITHER LOCATED OR
FORMING NORTHEAST OF THE VORTEX MESSAGE POSITION. THE ADVISORY
POSITION IS A COMPROMISE OF ALL THE SMALL SWIRLS AND LEANS MORE
TOWARD THE LARGE-SCALE ROTATION NOTED IN SATELLITE IMAGERY AND THE
SURFACE PRESSURE PATTERN. HOWEVER... ANY ONE OF THE SMALLER
CIRCULATIONS COULD BECOME MORE DOMINANT IF DEEP CONVECTION DEVELOPS
NEARBY. THE INITIAL INTENSITY OF 30 KT IS BASED ON A 31-KT SUSTAINED
WIND REPORTED EARLIER BY NOAA BUOY 42056.
 
THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 255/05.  THE VARIOUS
GLOBAL AND REGIONAL MODELS DID NOT INITIALIZE THE DEPRESSION VERY
WELL... ESPECIALLY THE GFS AND CANADIAN MODELS. HOWEVER... THE
GENERAL TREND IN ALL OF THE MODELS IS FOR THE BROAD SUBTROPICAL
RIDGE TO THE NORTH ALONG THE NORTHERN GULF COAST TO SLOWLY BUILD
WESTWARD THROUGHOUT THE FORECAST PERIOD. THE MORE WESTWARD AND
SOUTHERLY INITIAL POSITION HAS RESULTED IN A SOUTHWARD SHIFT OF THE
BAM MODELS... AND AS RESULT... THE OFFICIAL FORECAST TRACK WAS ALSO
SHIFTED SOUTHWARD. IT SHOULD BE NOTED THAT SOME ERRATIC MOTION WILL
BE POSSIBLE UNTIL A WELL-DEFINED LOW-LEVEL CENTER DEVELOPS.
 
EXCLUDING LAND INTERACTION... ENVIRONMENTAL CONDITIONS ARE EXPECTED
TO BE QUITE FAVORABLE FOR SOME SIGNIFICANT INTENSIFICATION TO
OCCUR. THE SHIPS MODEL INCREASES THE INTENSITY TO 86 KT BY 72 HOURS
AND 94 KT BY 96 HOURS DUE TO VERY WARM SSTS AND LOW VERTICAL SHEAR.
THE 12Z GFDL MODEL LOSES THE CYCLONE BY 24 HOURS... WHICH IS NOT
UNUSUAL FOR SYSTEMS THAT ARE INITIALIZED WITH 25 KT WINDS. THE 18Z
GFDL WILL LIKELY BE MORE ROBUST SINCE IT WAS INITIALIZED WITH 30 KT
SURFACE WINDS.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/2100Z 19.2N  86.5W    30 KT
 12HR VT     02/0600Z 19.8N  87.9W    35 KT...INLAND ERN YUCATAN
 24HR VT     02/1800Z 20.4N  89.8W    25 KT...INLAND WRN YUCATAN
 36HR VT     03/0600Z 21.0N  91.8W    35 KT...OVER WATER
 48HR VT     03/1800Z 21.4N  93.6W    50 KT
 72HR VT     04/1800Z 21.6N  96.2W    65 KT
 96HR VT     05/1800Z 21.0N  99.0W    30 KT...INLAND ERN MEXICO
120HR VT     06/1800Z...DISSIPATED INLAND
 
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