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TROPICAL DEPRESSION TEN DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT SAT SEP 22 2001
 
TROPICAL DEPRESSION TEN IS A BIT OF AN ENIGMA THIS MORNING.  THE
SYSTEM SHOWS A NICE CURVED CONVECTIVE BAND IN THE EASTERN
SEMICIRCLE...AND THIS IS RESPONSIBLE FOR  SATELLITE INTENSITY
ESTIMATES OF 45 KT FROM SAB AND 35 KT FROM TAFB.  HOWEVER...
MULTISPECTRAL IR IMAGERY SHOWS SOME EXPOSED LOW CLOUD LINES WEST
OF THE MAIN CONVECTION SUGGESTING THAT THE CENTER IS ON THE EDGE
OF THE CONVECTION.  BETWEEN THIS AND THE EARLIER SHIP AND AIRCRAFT
DATA SHOWING THE SYSTEM WAS LESS INTENSE THAN THE SATELLITE
ESTIMATES...THE INITIAL INTENSITY WILL REMAIN 25 KT.  FIRST LIGHT
VISIBLE IMAGES IN A FEW HR MAY HELP SHOW WHETHER THE CYCLONE HAS
ACTUALLY STRENGTHENED OR NOT.

THE LOW CLOUD LINES SUGGEST THE CENTER MAY BE WEST OF THE SATELLITE
FIXES...AND THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 320/12.
THE DEPRESSION IS NORTHEAST OF AN UPPER LOW AND MOVING TOWARD A
BREAK IN THE SUBTROPICAL RIDGE.  LARGE-SCALE MODELS ALL DEVELOP
A LARGE DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES...AND THE
COMBINATION OF THESE FACTORS SHOULD CAUSE THE CYCLONE TO GRADUALLY
RECURVE DURING THE FORECAST PERIOD.  NHC HURRICANE GUIDANCE IS IN
REASONABLY GOOD AGREEMENT WITH THIS SCENARIO...ALTHOUGH THERE IS
SOME SPREAD AS TO HOW FAR EAST THE CYCLONE MAY TURN.  THE OFFICIAL
FORECAST IS LITTLE CHANGED FROM THE PREVIOUS PACKAGE AND IS IN
BEST AGREEMENT WITH THE GFDL AND BAMD.  IT SHOULD BE NOTED THAT
THE BAM MODELS...THE AVN...AND THE UKMET HAVE SHIFTED THEIR
FORECASTS SOMEWHAT WESTWARD SINCE THE PREVIOUS PACKAGE.
 
WHILE THE DEPRESSION CURRENTLY SHOWS GOOD ANTICYCLONIC OUTFLOW OVER
THE EASTERN SEMICIRCLE...THE PARTLY EXPOSED CENTER SUGGESTS THAT
THE UPPER LEVEL ENVIRONMENT IS LESS FAVORABLE THAN IT APPEARS TO
BE.  IN THE SHORT TERM...AN UPPER LEVEL LOW SOUTHWEST OF THE
DEPRESSION IS FORECAST BY LARGE-SCALE MODELS TO LIFT NORTHWARD AND
POSSIBLY SHEAR THE DEPRESSION.  THERE ARE NO SIGNS OF THIS
HAPPENING YET.  IN THE LONGER TERM...THE CYCLONE WILL LIKELY RUN
INTO STRONG UPPER LEVEL SOUTHWESTERLIES THAT SHOULD LIMIT
DEVELOPMENT.  BASED ON THIS...THE INTENSITY FORECAST WILL CONTINUE
TO CALL FOR STRENGTHENING...BUT A LITTLE LESS STRENGTHENING THAN
INT THE PREVIOUS PACKAGE.

FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     22/0900Z 28.1N  66.5W    25 KTS
12HR VT     22/1800Z 29.3N  67.6W    30 KTS
24HR VT     23/0600Z 31.0N  68.6W    35 KTS
36HR VT     23/1800Z 32.8N  69.4W    45 KTS
48HR VT     24/0600Z 35.0N  69.5W    55 KTS
72HR VT     25/0600Z 37.5N  68.5W    60 KTS
 
 
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