000
AXNT20 KNHC 312356
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT DEC 31 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2315 UTC.

...ITCZ/MONSOON TROUGH...

THE ITCZ EXTENDS FROM LIBERIA NEAR 5N10W TO 1N40W TO BRAZIL NEAR 
1N46W. ISOLATED MODERATE CONVECTION IS FROM 4N-9N BETWEEN 
15W-20W...AND FROM 3N-6N BETWEEN 30W-47W. 

...DISCUSSION...

GULF OF MEXICO...
A 1023 MB HIGH IS CENTERED OVER THE NE GULF OF MEXICO NEAR 
27N88W PRODUCING FAIR WEATHER. 5-10 KT ANTICYCLONIC WINDS ARE 
GOING AROUND THE HIGH. A SURFACE TROUGH IS OVER THE BAY OF 
CAMPECHE ALONG 21N95W 17N93W PRODUCING ONLY A WIND SHIFT IN A 10 
KT WIND FIELD. IN THE UPPER LEVELS...ZONAL FLOW PREVAILS. 
CONSIDERABLE UPPER LEVEL MOISTURE AND HIGH CLOUDS ARE OVER 
MEXICO AND THE W GULF W OF 90W FROM 20N-28N. STRONG SUBSIDENCE 
IS OVER THE E GULF. EXPECT IN 24 HOURS FOR...A STRONG COLD FRONT 
TO EXTEND FROM THE FLORIDA PANHANDLE TO S OF MATAMOROS MEXICO 
ALONG 31N86W 24N98W WITH CONVECTION AND MOVING SE. ALSO EXPECT 
20-25 KT WINDS BEHIND THE FRONT WITH A GOOD AMOUNT OF COLD AIR 
ADVECTION. EXPECT 10-15 KT EASTERLY SURFACE WINDS AND FAIR 
WEATHER OVER THE REMAINDER OF THE GULF.     

CARIBBEAN SEA...
15-30 KT TRADEWINDS ARE OVER THE CARIBBEAN SEA AND CENTRAL 
AMERICA WITH STRONGEST WINDS ALONG THE COAST OF N COLOMBIA AND 
LIGHTEST WINDS OVER THE YUCATAN CHANNEL. SCATTERED MODERATE 
CONVECTION IS NOTED ALONG THE COAST OF THE YUCATAN PENINSULA 
FROM 17N-20N BETWEEN 87W-90W. ISOLATED SHOWERS DOTS THE 
CARIBBEAN SEA NAMELY OVER THE W CARIBBEAN...NICARAGUA...AND 
HONDURAS FROM 12N-18N BETWEEN 76W-86W...AND OVER THE E CARIBBEAN 
E OF 70W. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE IS OVER THE 
CARIBBEAN WITH AXIS ALONG 70W. UPPER LEVEL SUBSIDENCE COVERS THE 
CARIBBEAN EXCEPT OVER THE COAST OF THE YUCATAN PENINSULA. EXPECT 
OVER THE NEXT 24 HOURS FOR INCREASED CONVECTION TO BE OVER THE W 
CARIBBEAN AND CENTRAL AMERICA W OF 82W.  

ATLANTIC OCEAN...
A SURFACE TROUGH IS OVER THE SOUTHERN BAHAMAS ALONG 25N72W 
20N74W. BROKEN LOW CLOUDS AND SCATTERED SHOWERS ARE WITHIN 30 NM 
OF THE TROUGH. A 1035 MB HIGH IS CENTERED W OF THE MADEIRA 
ISLANDS NEAR 35N23W. A SURFACE RIDGE AXIS EXTENDS SW FROM THE 
HIGH TO 30N60W THUS THE EASTERN AND CENTRAL ATLANTIC HAS 
EASTERLY FLOW FROM 10N-30N BETWEEN W AFRICA AND 60W. A TIGHT 
SURFACE PRESSURE GRADIENT IS ALSO OVER THE EASTERN AND CENTRAL 
ATLANTIC PRODUCING 25-30 KT WINDS FROM 15N-25N E OF 60W. 
IN THE UPPER LEVELS...AN UPPER LEVEL LOW IS CENTERED OVER THE 
TROPICAL CENTRAL ATLANTIC NEAR 17N36W. UPPER LEVEL DIFFLUENCE E 
OF THE LOW IS PRODUCING WIDELY SCATTERED MODERATE CONVECTION 
FROM 10N-17N BETWEEN 20W-35W. EXPECT IN 24 HOURS FOR THE TAIL 
END OF A COLD FRONT TO BE OVER THE CENTRAL AND WESTERN ATLANTIC 
FROM 30N66W TO THE CENTRAL BAHAMAS NEAR 25N75W WITH RAIN AND 
SHOWERS.  

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

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FORMOSA