000
AXNT20 KNHC 281115
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST WED DEC 28 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1100 UTC.

...ITCZ/MONSOON TROUGH...

A GREAT PORTION OF THE MONSOON TROUGH REMAINS INLAND OVER 
AFRICA. A SMALL SECTION OF IT ENTERS THE ATLC THROUGH THE COAST 
OF SIERRA LEONE ALONG 8N13W AND QUICKLY ENDS AT 3N23W. THE ITCZ 
AXIS EXTENDS WSW FROM THIS POINT ALONG 2N40W TO THE COAST OF 
BRAZIL NEAR 1S47W. SCATTERED MODERATE TO ISOLATED STRONG 
CONVECTION IS WITHIN 200 NM ON THE NRN SIDE OF THE ITCZ AXIS 
BETWEEN 17W-40W.

...DISCUSSION...

GULF OF MEXICO...
THE COLD FRONT THAT HAS BEEN MOVING ACROSS THE GULF THESE PAST 
FEW DAYS IS NOW IN THE WRN ATLC BASIN. ONLY SCATTERED SHOWERS 
AND POSSIBLE ISOLATED THUNDERSTORMS ARE LINGERING OVER THE BAY 
OF CAMPECHE S OF 21N. THE REMAINDER OF THE GULF IS UNDER THE 
INFLUENCE OF MOSTLY DRY WSW FLOW ALOFT AND A SURFACE RIDGE 
ANCHORED BY A 1023 MB HIGH CENTERED OVER SRN LOUISIANA. 
NORTHERLY WINDS ARE EXPECTED TO PERSIST WITH WEATHER CONDITIONS 
REMAINING FAIR THROUGH EARLY THURSDAY.

CARIBBEAN SEA...
VERY DRY AIR ALOFT AND STRONG SUBSIDENCE COVERS MOST OF THE 
CARIBBEAN WATERS THIS MORNING. THIS AIRMASS IS SUPPRESSING DEEP 
CONVECTION ACROSS THE DISCUSSION AREA. HOWEVER...A FEW SHOWERS 
ARE OVER THE FAR NW BASIN INCLUDING THE YUCATAN CHANNEL IN THE 
VICINITY OF THE SRN EXTENSION OF THE WRN ATLC COLD FRONT. FRESH 
TO STRONG TRADE WIND FLOW CONTINUES ACROSS MUCH OF THE 
BASIN...ESPECIALLY BETWEEN 68W-80W AND NEAR THE COAST OF 
COLOMBIA...WITH A FEW SMALL CLUSTERS OF LOW-TOP WEAK SHOWERS 
EMBEDDED IN THE FLOW. THESE CONDITIONS ARE EXPECTED TO PERSIST 
THROUGH FRIDAY AS A RIDGE WILL POSITION ITSELF IN THE SW NORTH 
ATLC AND INCREASE THE TRADES DUE TO AN INCREASED PRESSURE 
GRADIENT. THE TRADES WILL REMAIN STRONG BASIN-WIDE THROUGH THE 
UPCOMING WEEKEND.

ATLANTIC OCEAN...
A LONGWAVE UPPER LEVEL TROUGH IS MOVING OFF THE CONUS SEABOARD 
SUPPORTING A COLD FRONT ANALYZED INTO THE DISCUSSION AREA ALONG 
32N73W ACROSS THE NW BAHAMAS NEAR 25N77W TO THE COAST OF CUBA 
NEAR 23N81W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 70 
NM ON EITHER SIDE OF THE FRONT. THE REMAINDER OF THE SW NORTH 
ATLC IS UNDER THE INFLUENCE OF A 1023 MB SURFACE HIGH CENTERED 
NEAR 29N62W. FARTHER EAST...AN UPPER LEVEL LOW IS NOTED ON WATER 
VAPOR IMAGERY CENTERED NORTH OF THE DISCUSSION AREA. THIS UPPER 
LEVEL FEATURE SUPPORTS AN OCCLUDED BUT STRONG LOW PRESSURE 
SYSTEM THAT EXTENDS A COLD FRONT INTO THE AREA ALONG 32N44W TO 
27N47W TO 24N54W. SCATTERED SHOWERS AND THUNDERSTORMS ARE WITHIN 
100-200 NM E OF THE BOUNDARY. THE MAIN IMPACT WITH THIS FRONT IS 
GUSTY NW WINDS UP TO 25 KT N OF 27N W OF FRONT TO 55W GENERATING 
SEAS BETWEEN 12-23 FT. THE REMAINDER OF THE EASTERN ATLC IS 
UNDER THE INFLUENCE OF AN UPPER LEVEL LOW CENTERED NEAR 21N27W. 
MIDDLE TO UPPER LEVEL MOISTURE CONTINUES TO BE DRAWN ACROSS THE 
FAR ERN ATLC WITH ISOLATED SHOWERS OCCURRING FROM 10N-21N E OF 
23W. 

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

$$

GARCIA