000
AXNT20 KNHC 210518
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST WED DEC 21 2011

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

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0515 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE COAST OF SIERRA LEONE NEAR 
8N13W TO 7N15W. THE ITCZ CONTINUES FROM 7N15W TO 5N30W TO 5N52W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 4N-7N 
BETWEEN 12W-33W. 

...DISCUSSION...

GULF OF MEXICO...
A COLD FRONT EXTENDS FROM LOUISIANA TO TAMPICO MEXICO ALONG 
30N92W 22N98W. WIDELY SCATTERED MODERATE CONVECTION IS E OF THE 
FRONT N OF 26N BETWEEN 86W-93W. 15 KT N WINDS ARE W OF THE FRONT 
WITH PLENTY OF COLD AIR ADVECTION. THE REMAINDER OF THE GULF OF 
MEXICO HAS 10-20 KT SOUTHERLY RETURN FLOW AND FAIR WEATHER WITH 
TEMPERATURES IN THE 70'S. EXPECT THE COLD FRONT OVER THE NEXT 24 
HOURS TO STALL AND RETROGRADE BACK W TO THE TEXAS COAST WITH 
RAIN AND SHOWERS. ALSO EXPECT SOUTHERLY RETURN FLOW OVER THE 
REMAINDER OF THE GULF WITH SCATTERED SHOWERS OVER THE CENTRAL 
AND NE GULF.    

CARIBBEAN SEA...
A TIGHT SURFACE PRESSURE GRADIENT IS OVER THE CARIBBEAN SEA 
PRODUCING 20-30 KT TRADEWINDS WITH STRONGEST WINDS ALONG THE 
COAST OF N COLOMBIA. A COLD FRONT THAT DIPPED INTO THE LEEWARD 
ISLAND HAS NOW DISSIPATED...HOWEVER RADAR IMAGERY SHOWS 
SCATTERED RAINSHOWERS REMAIN N OF 17N BETWEEN 60W-70W. A MONSOON 
TROUGH EXTENDS FROM N COLOMBIA TO COSTA RICA. ISOLATED SHOWERS 
ARE S OF 10N. BROKEN TO OVERCAST LOW CLOUDS WITH ISOLATED 
SHOWERS ARE FURTHER N OVER NICARAGUA AND HONDURAS. SIMILAR 
SHOWERS ARE OVER HISPANIOLA. MORE SHOWERS ARE OVER THE WINDWARD 
ISLANDS AND THE COAST OF N VENEZUELA S OF 14N. EXPECT OVER THE 
NEXT 24 HOURS FOR MORE SHOWERS TO ADVECT FROM THE ATLANTIC TO 
THE WINDWARD ISLANDS AND N VENEZUELA. ALSO EXPECT CONTINUED RAIN 
AND SHOWERS OVER THE SW CARIBBEAN AND CENTRAL AMERICA. 

ATLANTIC OCEAN...
A 1027 MB HIGH IS CENTERED OVER THE W ATLANTIC NEAR 30N70W. A 
COLD FRONT IS OVER THE CENTRAL ATLANTIC FROM 30N40W TO 20N50W. A 
DISSIPATING COLD FRONT CONTINUES TO E OF THE LEEWARD ISLANDS AT 
18N60W. WIDELY SCATTERED MODERATE CONVECTION IS N OF 26N BETWEEN 
38W-40W. SCATTERED SHOWERS ARE WITHIN 30 NM OF THE REMAINDER OF 
THE FRONT. A SHEAR LINE IS E OF THE LESSER ANTILLES FROM 13N54W 
TO 10N60W. SCATTERED SHOWERS ARE WITHIN 30 NM OF THE SHEAR LINE. 
A 1034 MB HIGH IS CENTERED W OF SPAIN AT 41N15W. A RIDGE AXIS 
EXTENDS S FROM THE HIGH TO 27N34W. EXPECT THE COLD FRONT TO MOVE 
E TO THE EASTERN ATLANTIC OVER THE NEXT 24 HOURS TO 30N36W WITH 
CONVECTION.   

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

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FORMOSA