[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 101453
TCDAT2

TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072012
1100 AM AST FRI AUG 10 2012

THE CONVECTIVE STRUCTURE OF THE DEPRESSION HAS CHANGED LITTLE OVER
THE PAST FEW HOURS...AND DVORAK CI NUMBERS ARE STILL 1.5 FROM TAFB
AND SAB.  WITHOUT ANY ADDITIONAL DATA AVAILABLE TO US AT THIS
TIME...WE ARE KEEPING THE CYCLONE AS A 30-KT DEPRESSION.

THE CENTER OF THE DEPRESSION HAS BECOME MORE APPARENT IN VISIBLE
IMAGERY...AND THE UPDATED POSITION YIELDS A FASTER 12-HR MOTION OF
270/20 KT.  THE SUBTROPICAL RIDGE TO THE NORTH OF THE DEPRESSION IS
EXPECTED TO CONTINUE STEERING THE CYCLONE WESTWARD INTO THE
CARIBBEAN SEA OVER THE NEXT FEW DAYS.  THE RIDGE SHOULD BREAK DOWN
OVER THE FAR WESTERN ATLANTIC AND GULF OF MEXICO BY DAYS 4 AND
5...BUT SINCE THE CYCLONE IS EXPECTED TO REMAIN WEAK...NOT MUCH
GAIN IN LATITUDE IS EXPECTED.  THE NEW NHC FORECAST IS AN UPDATE OF
THE PREVIOUS ONE TO ACCOUNT FOR THE FASTER INITIAL MOTION AND
CONTINUES TO LIE CLOSE TO THE GFS SOLUTION.

NEEDLESS TO SAY...THE INTENSITY FORECAST IS A DIFFICULT ONE.  THE
ONLY ENVIRONMENTAL PARAMETER THAT APPEARS IDEAL FOR STRENGTHENING
IS THE SEA SURFACE TEMPERATURE.  ON THE OTHER HAND...THE DEPRESSION
IS LIKELY BEING AFFECTED BY SURROUNDING DRY AIR...WHICH COULD BE
COMPOUNDED BY INCREASING SOUTHERLY TO SOUTHWESTERLY SHEAR OVER THE
NEXT COUPLE OF DAYS.  THE FAST MOTION OF THE DEPRESSION WOULD
NORMALLY FAVOR LESS STRENGTHENING AS WELL.  PROBABLY DUE TO THESE
FACTORS...THE MAJORITY OF THE GLOBAL MODELS CONTINUE TO DEGENERATE
THE CYCLONE INTO AN OPEN WAVE OVER THE EASTERN CARIBBEAN SEA.  AS
PLAUSIBLE AS THAT SCENARIO IS...THE OFFICIAL FORECAST STILL KEEPS
THE SYSTEM AS A TROPICAL CYCLONE THROUGH THE 5-DAY PERIOD BUT AT A
SLIGHTLY LOWER INTENSITY.

GIVEN THE HIGH UNCERTAINTY IN THE INTENSITY FORECAST...AND THE
POSSIBILITY THAT THE DEPRESSION COULD BECOME AN OPEN WAVE EARLIER
THAN INDICATED BY THE GLOBAL MODELS...TROPICAL STORM WATCHES AND
WARNINGS ARE NOT BEING ISSUED FOR PORTIONS OF THE LESSER ANTILLES
AT THIS TIME.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 13.7N  49.5W   30 KT  35 MPH
 12H  11/0000Z 13.7N  52.2W   35 KT  40 MPH
 24H  11/1200Z 13.8N  55.7W   40 KT  45 MPH
 36H  12/0000Z 14.1N  59.1W   40 KT  45 MPH
 48H  12/1200Z 14.6N  62.5W   40 KT  45 MPH
 72H  13/1200Z 15.5N  69.0W   40 KT  45 MPH
 96H  14/1200Z 16.0N  76.0W   40 KT  45 MPH
120H  15/1200Z 17.0N  83.5W   40 KT  45 MPH

$$
FORECASTER BERG



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