000
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