000
AXNT20 KNHC 290545
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0535 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST OF GUINEA NEAR 
10N14W TO 5N22W. THE ITCZ AXIS EXTENDS WSW FROM THIS POINT ALONG 
2N33W TO THE COAST OF BRAZIL NEAR 1S47W. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION IS WITHIN 120 NM ON THE NRN SIDE OF 
THE ITCZ AXIS BETWEEN 20W-30W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL SHORTWAVE PROGRESSING 
OVER THE N CENTRAL GULF BASIN ADVECTING MIDDLE TO UPPER LEVEL 
MOISTURE ACROSS THE NE CORNER OF THE BASIN. DESPITE THE UPPER 
LEVEL FEATURE...A 1022 MB HIGH IS CENTERED OVER THE COASTAL 
WATERS NEAR THE WESTERN FLORIDA PANHANDLE NEAR 30N87W. IN 
ADDITION TO LIGHT AND VARIABLE WINDS IN THE VICINITY AND AROUND 
THE HIGH PRESSURE CENTER...LIGHT ANTICYCLONIC FLOW AND FAIR 
WEATHER CONDITIONS ARE EXPERIENCED ELSEWHERE ACROSS THE AREA. 
THE HIGH IS FORECAST TO SLIDE EASTWARD THROUGH SATURDAY AND MOVE 
INTO THE SW NORTH ATLC BY SUNDAY. THE NEXT COLD FRONT IS THEN 
EXPECTED BY SUNDAY MORNING TO ENTER THE NW GULF USHERING IN 
STRONG NORTHERLY WINDS THAT WILL SPREAD EASTWARD ACROSS THE GULF 
THROUGH EARLY NEXT WEEK.

CARIBBEAN SEA...
VERY DRY AIR ALOFT AND STRONG SUBSIDENCE COVERS THE CARIBBEAN 
WATERS THIS LATE EVENING. THIS AIRMASS IS SUPPRESSING DEEP 
CONVECTION ACROSS THE DISCUSSION AREA. HOWEVER...A SHEAR LINE IS 
ANALYZED ALONG CENTRAL CUBA NEAR 22N79W TO 18N85W WITH ISOLATED 
SHOWERS OCCURRING WITHIN 120 NM EITHER SIDE OF THE BOUNDARY. 
MODERATE TO FRESH TRADE WIND FLOW CONTINUES ACROSS MUCH OF THE 
CENTRAL AND ERN BASIN...ESPECIALLY BETWEEN 67W-77W 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 BROAD UPPER LEVEL TROUGH IS MOVING ACROSS THE NW ATLC 
SUPPORTING A COLD FRONT ANALYZED INTO THE DISCUSSION AREA ALONG 
32N62W TO THE CENTRAL BAHAMAS NEAR 24N75W BECOMING A WEAK SHEAR 
LINE AXIS INTO CENTRAL CUBA ALONG 22N79W. SCATTERED WEAK SHOWERS 
AND POSSIBLE ISOLATED TSTMS ARE OCCURRING WITHIN 30 NM ON EITHER 
SIDE OF THE FRONT. HIGH PRESSURE WILL CONTINUE TO BUILD IN 
BEHIND THE FRONT FROM THE EASTERN GULF OF MEXICO ACROSS THE 
REMAINDER OF THE SW NORTH ATLC THROUGH EARLY FRIDAY. FARTHER 
EAST...A NARROW UPPER LEVEL TROUGH IS MOVING ACROSS THE N 
CENTRAL ATLC OUTSIDE THE DISCUSSION AREA. THIS UPPER LEVEL 
FEATURE SUPPORTS THE TAIL END OF A COLD FRONT THAT EXTENDS INTO 
THE AREA ALONG 32N39W TO 25N43W. LOW-LEVEL MOISTURE REMAINS 
LIMITED WITH THIS FRONT...WITH JUST A FEW WEAK SHOWERS WITHIN 40 
EITHER SIDE OF THE FRONT. THE REMAINDER OF THE EASTERN ATLC IS 
UNDER THE INFLUENCE OF A STRONG SURFACE RIDGE ANCHORED N OF THE 
DISCUSSION AREA.

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

$$

GARCIA