Tropical Depression TWENTY

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TROPICAL DEPRESSION TWENTY DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT SAT OCT 01 2005
 
SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT THE CENTER
OF TROPICAL DEPRESSION TWENTY REMAINS BROAD THIS EVENING. 
HOWEVER...CONVECTION HAS INCREASED THIS EVENING...ESPECIALLY IN A
POORLY CURVED BAND IN THE SOUTHEASTERN QUADRANT.  THE INITIAL
INTENSITY REMAINS 30 KT IN AGREEMENT WITH SATELLITE INTENSITY
ESTIMATES FROM TAFB AND SAB.  THE CIRRUS OUTFLOW IS FAIR IN THE
EASTERN SEMICIRCLE AND IMPROVING IN THE WESTERN SEMICIRCLE.

THE CENTER IS A LITTLE HARD TO FIND IN INFRARED IMAGERY...SO THE
INITIAL MOTION IS A SOMEWHAT UNCERTAIN 285/5.  SATELLITE IMAGERY
AND EVENING RAWINSONDE DATA SHOWS LOW/MID/LEVEL RIDGING NORTH OF
THE DEPRESSION...WHICH IN THE SHORT TERM SHOULD KEEP THE CYCLONE ON
A WEST-NORTHWESTWARD TO WESTWARD TRACK.  AFTER 24-36 HR...A MID/
UPPER-LEVEL TROUGH OVER THE CENTRAL UNITED STATES SHOULD MOVE
NORTHEASTWARD...ALLOWING THE RIDGE TO BUILD WESTWARD TO THE WESTERN
GULF COAST.  THIS SHOULD CAUSE THE DEPRESSION TO TURN WESTWARD OR
EVEN WEST-SOUTHWESTWARD.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT
ON THIS SCENARIO THROUGH 72 HR.  AFTER THAT...THINGS BECOME MORE
UNCERTAIN AS THE LARGE-SCALE MODELS HAVE A VARIETY OF FORECASTS OF
HOW THE PATTERN AROUND THE DEPRESSION WILL EVOLVE.  SOME MODELS
STALL THE DEPRESSION OVER THE SOUTHWESTERN GULF...WHILE OTHERS MOVE
IT INTO MEXICO.  OTHERS DISSIPATE IT AS A NEW SYSTEM FORMS EAST OF
THE DEPRESSION IN THE CARIBBEAN...OR NORTHEAST OF THE DEPRESSION
ALONG A COLD FRONT FORECAST TO MOVE INTO THE GULF OF MEXICO.  THE
OFFICIAL FORECAST CONTINUES THE TREND OF THE PREVIOUS ADVISORY OF
MOVING THE CYCLONE WEST-SOUTHWESTWARD INTO MEXICO... ALBEIT AT A
SLOWER SPEED THAN THE PREVIOUS TRACK. HOWEVER...THE CONFIDENCE THAT
THIS WILL HAPPEN IS DECREASING.
 
CONDITIONS APPEAR FAVORABLE FOR STRENGTHENING THROUGH 72 HR WHILE
THE CYCLONE IS OVER WATER...AS VERTICAL SHEAR IS FORECAST TO BE
LIGHT.  THE INTENSITY FORECAST THUS CALLS FOR THE SYSTEM TO BRIEFLY
BECOME A TROPICAL STORM BEFORE MAKING LANDFALL ON YUCATAN...
FOLLOWED BY WEAKENING OVER LAND AND RE-INTENSIFICATION OVER THE BAY
OF CAMPECHE.  EVEN WITH LAND INTERACTION...SHIPS CALLS FOR THE
SYSTEM TO REACH HURRICANE STRENGTH IN 72 HR AND THE INTENSITY
FORECAST FOLLOWS THIS.  HOWEVER...THE LATEST GFDL RUN DOES NOT
STRENGTHEN THE CYCLONE ABOVE 40 KT.  THE INTENSITY FORECAST ASSUMES
THE CYCLONE WILL DISSIPATE OVER THE MOUNTAINS OF MEXICO AFTER
LANDFALL IN ABOUT 84 HR.  SHOULD THAT LANDFALL NOT OCCUR OR BE
DELAYED...THE LARGE-SCALE MODELS SUGGEST THE ENVIRONMENT MAY BECOME
LESS FAVORABLE FOR DEVELOPMENT DUE TO AN UPPER-LEVEL LOW FORMING
OVER THE GULF OF MEXICO AND A COLD FRONT MOVING TOWARD THE
SOUTHWESTERN GULF.
  
FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0300Z 19.3N  87.0W    30 KT
 12HR VT     02/1200Z 19.7N  88.2W    35 KT...INLAND
 24HR VT     03/0000Z 20.3N  90.2W    25 KT...INLAND
 36HR VT     03/1200Z 20.8N  92.0W    35 KT...OVER WATER
 48HR VT     04/0000Z 21.0N  93.8W    50 KT
 72HR VT     05/0000Z 20.5N  96.0W    65 KT
 96HR VT     06/0000Z 20.0N  98.5W    30 KT...INLAND
120HR VT     07/0000Z...DISSIPATED
 
 
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