[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271741
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED APR 27 2011

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTION
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1730 UTC.

...THE ITCZ...

FROM THE COAST OF SIERRA LEONE NEAR 7N12W...CROSSING THE EQUATOR
ALONG 22W...TO 5S25W. THEN..IT RESUMES NEAR 2S37W...INTO COASTAL
NORTHEASTERN BRAZIL NEAR EQ50W. A SURFACE TROUGH IS ANALYZED
FROM 2S33W TO 10S30W. THIS TROUGH IS WITHIN A BROAD AREA OF
LOW-MID LEVEL CYCLONIC CURVATURE GENERATING NUMEROUS MODERATE TO
HEAVY SHOWERS AND THUNDERSTORMS FROM 2S-14S BETWEEN 22W AND THE
COAST OF BRAZIL. SIMILAR CONVECTION IS OCCURRING FROM THE
EQUATOR TO 6N BETWEEN 20W-27W...AND ALSO FROM 5S-2N BETWEEN
10W-20W.

...DISCUSSION...

GULF OF MEXICO...
A COLD FRONT IS QUICKLY EMERGING OFF THE TEXAS COAST...MOVING
EAST ACROSS THE NW BASIN AT ABOUT 20 KT. THIS BOUNDARY IS
ANALYZED FROM THE COASTAL BORDER BETWEEN TEXAS AND LOUISIANA TO
THE SOUTHERN MOST COASTAL TIP OF TEXAS. A SHARP DROP IN DEW
POINT VALUES IS THE VARIABLE MOST NOTICED BEHIND THE FRONT.
DESPITE THE FRONTAL BOUNDARY...NO CONVECTION IS OBSERVED IN
SATELLITE...NOR DOPPLER RADAR IMAGERY. THIS IS DUE TO A DRY
WESTERLY FLOW ALOFT NOTED ON WATER VAPOR IMAGERY. THIS PATTERN
ALOFT IS SUPPRESSING ANY CONVECTIVE ACTIVITY ASSOCIATED TO THE
FRONT...WHILE AT THE SAME TIME MAINTAINING FAIR WEATHER
CONDITIONS ELSEWHERE ACROSS THE GULF. THE SURFACE PRESSURE
GRADIENT AHEAD OF THE FRONT HAS STREIGHTENED FROM E TO W OVER
THE PAST FEW HOURS...PRODUCING A SOUTHERLY/RETURN FLOW ELSEWHERE
ACROSS THE AREA...WITH UP TO NEAR GALE FORCE WINDS N OF 26N W OF
87W. THIS FRONT IS EXPECTED TO CONTINUE TO MOVE EASTWARD WITH
VERY LIMITED CONVECTION OVER THE NEXT 12 HOURS...AND EVENTUALLY
MAY TRIGGER SOME CONVECTION OVER THE COASTAL WATERS OF
MISSISSIPPI...ALABAMA...AND THE WESTERN FLORIDA PANHANDLE THE
NEXT 12 TO 24 HOURS.

CARIBBEAN SEA...
MOST OF THE CARIBBEAN SEA IS EXPERIENCING FAIR WEATHER
CONDITIONS DUE TO DRY AND STABLE AIR ALOFT MOVING ACROSS THE
AREA. AT SURFACE...SURFACE AND MARINE OBSERVATIONS INDICATE
15-20 KT TRADE WINDS TURNING N WESTWARD W OF 75W N OF 13N. A
SURFACE TROUGH IS APPROACHING THE LESSER ANTILLES...ANALYZED
FROM JUST EAST OF MARTINIQUE TO THE SOUTHERN TIP OF TRINIDAD AND
TOBAGO. THIS SYSTEM IS GENERATING SCATTERED SHOWERS AND
THUNDERSTORMS TO THE ISLANDS S OF MARTINIQUE. HOWEVER...THE
STRONGEST CONVECTION ASSOCIATED TO THIS SYSTEM IS FOUND EAST OF
THE LESSER ANTILLES. THEREFORE...AS THIS AREA OF CONVECTION
MOVES WEST...THESE GROUP OF ISLANDS WILL CONTINUE TO EXPERIENCE
BAD WEATHER FOR AT LEAST THE NEXT 24 HOURS AS THE TROUGH MOVES
WEST AT ABOUT 12 KT. ANOTHER AREA OF SCATTERED SHOWERS IS OVER
THE COASTAL WATERS OF PUERTO RICO AND EASTERN HISPANIOLA DUE TO
A WEAK UPPER LEVEL TROUGH LINGERING EAST ACROSS THE BAHAMAS.

ATLANTIC OCEAN...
MOST OF THE DISCUSSION AREA IS DOMINATED BY A STRONG UPPER LEVEL
RIDGE COVERING THE ATLC W OF 28W. THIS UPPER RIDGE IS SUPPORTING
A 1031 MB HIGH WOBBLING AROUND 34N57W. HOWEVER...A WEAKNESS IN
THE RIDGE ASSOCIATED TO A WEAK MID/UPPER LEVEL TROUGH EAST
ACROSS THE BAHAMAS IS GENERATING AN AREA OF SCATTERED MODERATE
TO HEAVY SHOWERS AND ISOLATED THUNDERSTORMS WITHIN 50 NM ON
EITHER SIDE OF A LINE FROM 18N65W TO 23N71W TO 29N75W. SHORT
RANGE COMPUTER MODELS SUGGEST THIS AREA OF CONVECTION WILL
LINGER OVER THE NEXT 24 HOURS. A WEAK 1014 MB LOW PRESSURE
SYSTEM IS OVER THE EAST ATLC NEAR 30N25W. NO SIGNIFICANT
CONVECTION IS OBSERVED IN THE VICINITY OF THE LOW. THIS SYSTEM
WILL DISSIPATE OVER THE NEXT 12 HOURS.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

GARCIA



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