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TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER 3
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT WED SEP 12 2001
SURFACE REPORTS INDICATE THAT THE DEPRESSION HAS BECOME A LITTLE
BETTER ORGANIZED. EAST GULF BUOY 42003 HAS A PRESSURE BELOW 1008 MB
AND A 24-HR PRESSURE DROP OF MORE THAN 4 MB. DEEP CONVECTION
REMAINS DISPLACED TO THE SOUTH OF THE CENTER DUE TO NORTHERLY
SHEAR...BUT BANDED CONVECTION HAS INCREASED IN THE EAST SEMICIRCLE
...ESPECIALLY ACROSS SOUTHERN FLORIDA.
THE INITIAL MOTION ESTIMATE IS 275/05. THE NHC MODEL GUIDANCE IS
WIDELY DIVERGENT AFTER 36 HOURS ON WHICH DIRECTION TO TAKE ERIN.
NOGAPS TAKES ERIN WEST-SOUTHWEST INTO THE SOUTHWEST GULF OF MEXICO
...BUT THIS APPEARS TO BE THE OUTLIER MODEL. THE SHORTWAVE TROUGH
CURRENTLY OVER THE SOUTHEAST U.S. COAST SHOULD LIFT OUT LATER TODAY
AND POSSIBLY CAUSE ERIN TO BECOME NEARLY STATIONARY. HOWEVER...BY
36 TO 48 HOURS...A SHORTAVE TROUGH OVER THE CENTRAL PLAINS IS
FOREACST TO DROP DOWN AND GRADUALLY PICK UP THE CYCLONE AND BEGIN
MOVING IT TO THE NORTHEAST. THE UKMET-AVN CONSENSUS WAS FOLLOWED
CLOSELY AND THE OFFICIAL FORWCAST IS JUST AN EXTENSION OF THE
PREVIOUS TRACK.
LITTLE CHANGE IN STRENGTH IS EXPECTED THROUGH 24 TO 36 HOURS DUE TO
NORTHERLY UPPER-LEVEL SHEAR AND DRY AIR ENTRAINMENT. HOWEVER... BY
36 TO 48 HOURS...THE UPPER-LEVEL FLOW IS EXPECTED TO BECOME QUITE
WEAK AND MORE ANTICYCLONIC...WHICH WOULD FAVOR SOME INTENSIFICATION
BEFORE THE SHEAR INCREASES AGAIN BY 72 HOURS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 12/0900Z 25.7N 85.8W 25 KTS
12HR VT 12/1800Z 25.8N 86.2W 30 KTS
24HR VT 13/0600Z 26.4N 86.6W 30 KTS
36HR VT 13/1800Z 27.2N 86.7W 35 KTS
48HR VT 14/0600Z 28.0N 86.0W 45 KTS
72HR VT 15/0600Z 29.0N 84.0W 60 KTS
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