000
AXNT20 KNHC 182343
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL  
805 PM EDT FRI MAR 18 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2245 UTC.

...ITCZ...

THE ITCZ AXIS IS ALONG 5N9W 1N20W CROSSING THE EQUATOR AT 25W 
THEN CONTINUES ALONG 1S35W INTO NE BRAZIL NEAR 4S42W. ISOLATED 
MODERATE CONVECTION IS NEAR 3N10W AND NEAR 2N29W. SIMILAR 
CONVECTION IS FROM THE EQUATOR TO 5N BETWEEN 36W AND 46W. 

...DISCUSSION...

GULF OF MEXICO...
A 1026 MB SURFACE HIGH PRESSURE LOCATED NEAR 29N87W DOMINATES 
THE ENTIRE GULF OF MEXICO AND THE STATE OF FLORIDA PRODUCING 
MAINLY FAIR WEATHER CONDITIONS. WINDS ARE LIGHT AND VARIABLE 
NEAR THE HIGH PRES CENTER. MODERATE TO FRESH WINDS PREVAIL ON 
THE SOUTHERN PERIPHERY OF THE HIGH WITH SLY RETURN FLOW OVER THE 
WESTERN GULF WATERS. A BAND OF TRANSVERSE HIGH CLOUDS IS NOTED 
OVER THE SOUTHERN GULF IN ASSOCIATION WITH A MOSTLY ZONAL 
WESTERLY FLOW ALOFT. MODERATE TO STRONG SUBSIDENCE AND THE 
IMPLIED DRY AIR MASS IS SEEN N OF 26N INCLUDING THE N GULF 
STATES AND FLORIDA WHERE WARM AND DRY WEATHER CONDITIONS ARE 
EXPECTED TO CONTINUE THROUGH SAT. THE SURFACE RIDGE IS FORECAST 
TO REMAIN NEARLY STATIONARY OVER THE NEXT SEVERAL DAYS AND 
CONTINUE TO PROVIDE OVERALL STABLE WEATHER CONDITIONS.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED EAST OF THE 
LESSER ANTILLES EXTENDS A RIDGE OVER MOST OF THE BASIN PRODUCING 
SW TO W WINDS ALOFT. MODERATE TO STRONG SUBSIDENCE IS ASSOCIATED 
WITH THIS RIDGE LIMITING THE DEVELOPMENT OF ANY DEEP CONVECTION. 
SHALLOW MOISTURE EMBEDDED IN THE TRADE WIND FLOW WILL CONTINUE 
TO AFFECT THE REGION GENERATING ISOLATED TO SCATTERED PASSING 
SHOWERS. A BAND OF LOW LEVEL MOISTURE IS NEAR THE COASTAL WATERS 
OF WESTERN VENEZUELA AND COLOMBIA. THIS CLOUDINESS IS ALSO 
AFFECTING THE ABC ISLANDS WHERE LIGHT SHOWERS HAVE BEEN 
REPORTED. SURFACE HIGH PRES LOCATED OVER THE NE GULF AND 
PORTIONS OF THE SW NORTH ATLC CONTINUES TO PRODUCE A LARGE AREA 
OF FRESH TO STRONG E-NE TRADES OVER MUCH OF THE CARIBBEAN WITH 
THE STRONGEST WINDS...AS USUAL...NEAR THE COAST OF COLOMBIA. 
SURFACE DATA AND THE MOST RECENT ASCAT PASS SHOWED NE WINDS OF 
25 KT NEAR THE COAST OF COLOMBIA. NE WINDS OF 2O KT CAN BE FOUND 
OVER THE NW CARIBBEAN AND JUST SOUTH OF DOMINICAN REPUBLIC. LOW 
LEVEL CONVERGENCE IS PUSHING ISOLATED SHOWERS ONSHORE ALONG THE 
NICARAGUA...COSTA RICA...AND WESTERN PANAMA COASTS. THE SURFACE 
FLOW IS FORECAST TO REMAIN QUITE BRISK THROUGH THE WEEKEND AS A 
STRONG HIGH PRES BUILDS N OF AREA.

ATLANTIC OCEAN...
HIGH PRES AT THE SURFACE AND ALOFT DOMINATES THE WESTERN ATLC W 
OF 65W WITH MOSTLY FAIR WEATHER CONDITIONS. THE COMBINATION OF 
THIS HIGH AND A COUPLE OF WEAK LOW PRES SYSTEMS LOCATED BETWEEN 
60W AND 65W WILL PRODUCE FRESH NE WINDS ACROSS THE SOUTHERN 
BAHAMAS AND THE GREATER ANTILLES THROUGH SAT NIGHT. SURFACE DATA 
AND THE LATEST ASCAT PASS PROVIDED OBSERVATIONS OF NE WINDS OF 
20 KT NEAR THE SE BAHAMAS AND THE WINDWARD PASSAGE. AN UPPER 
LEVEL TROUGH IS MOVING SE ACROSS THE FORECAST AREA WITH AXIS 
EXTENDING FROM AN UPPER-LEVEL LOW NEAR 30N62W TO THE NW BAHAMAS. 
AT THE SURFACE...A WEAK 1017 MB LOW PRES IS ANALYZED NEAR 30N63W 
WITH A TROUGH TO NEAR 26N61W. AN AREA OF SHOWERS WITH ISOLATED 
TSTMS IS AHEAD OF THE TROUGH AXIS PARTICULARLY N OF 26N BETWEEN 
55W AND 59W. UPPER DIFFLUENCE AHEAD OF THE AFOREMENTIONED UPPER 
LEVEL TROUGH IS HELPING TO INDUCE THIS CONVECTIVE ACTIVITY. 
ACCORDING TO THE GFS MODEL...THE LOW PRES WILL MOVE SE REACHING 
NEAR 24N52W IN ABOUT 24 HOURS WHILE DEEPENING. ANOTHER WEAK 1015 
MB LOW PRES IS NEAR 23N64W AND IS FORECAST TO DISSIPATE OVER THE 
NEXT DAY. A CUT-OFF LOW IS NEAR 36N31W WITH A TROUGH EXTENDING S 
AND SW TO NEAR 23N30W. THIS UPPER LEVEL FEATURE SUPPORTS A COLD 
FRONT THAT ENTERS THE DISCUSSION AREA NEAR 31N25W THEN CONTINUES 
SW TO 23N34W WHERE IT BECOMES STATIONARY TO 22N46W. A FEW 
SHOWERS ARE ALONG THE FRONTAL BOUNDARY. A 1027 MB HIGH PRES 
SITUATED NEAR 33N44W FOLLOWS THE FRONT. MODERATE TO FRESH TRADE 
WINDS ARE BLOWING ACROSS THE TROPICAL ATLANTIC.   

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

$$
GR