000
AXNT20 KNHC 212320
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
705 PM EST MON DEC 21 2009

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...METEOROLOGICAL ANALYSIS...WEATHER 
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2230 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N10W 6N20W 4N33W 3N42W 1N51W. 
NO DEEP CONVECTION IS NOTED AT THIS TIME.

...DISCUSSION...

GULF OF MEXICO...
SURFACE RIDGING CONTINUES TO DOMINATE THE GULF OF MEXICO 
ANCHORED BY A SERIES OF HIGH CENTERS RANGING FROM A 1026 MB  
HIGH OVER THE FLORIDA PANHANDLE...A 1028 MB HIGH OVER CENTRAL 
MEXICO...A 1025 MB HIGH ON THE MEXICO COASTLINE NEAR 
TAMPICO...AND A 1021 MB HIGH OVER GUATEMALA. MAINLY NE SURFACE 
FLOW IS ACROSS THE E GULF SHIFTING TO SE ACROSS THE W GULF. IN 
THE UPPER LEVELS...AN UPPER LEVEL TROUGH EXTENDS FROM LOUISIANA 
TO THE BAY OF CAMPECHE. MOIST SWLY FLOW AROUND THE E SIDE OF THE 
UPPER TROUGH IS SUPPORTING OVERCAST SKIES E OF 88W INCLUDING 
MUCH OF THE FLORIDA PENINSULA. EXPECT THE SURFACE RIDGE OVER THE 
NRN GULF TO CONTINUE TO SHIFT EWD ALLOWING RETURN FLOW TO 
INCREASE ACROSS THE W GULF AHEAD OF THE NEXT COLD FRONT FORECAST 
TO ENTER THE NW BASIN LATE WED. 

CARIBBEAN SEA...
A WEAK STATIONARY FRONT DRAPES ACROSS THE CARIBBEAN FROM 
HISPANIOLA TO JAMAICA AND INTO THE SW CARIBBEAN TO COSTA RICA. A 
SURFACE TROUGH IS AHEAD OF THE FRONT EXTENDING FROM S OF JAMAICA 
TO PANAMA. N-NE WINDS UP TO 25 KTS ARE BEHIND THE FRONT.  MOIST 
SWLY FLOW ALOFT AROUND AN UPPER LEVEL RIDGE CENTERED E OF THE 
LESSER ANTILLES IS ACROSS THE BASIN DRAWING TROPICAL MOISTURE TO 
THE NE. THIS ALONG WITH SURFACE CONVERGENCE NEAR THE FRONT AND 
TROUGH ARE SUPPORTING SCATTERED SHOWERS W OF 77W. DRY AIR AND 
SUBSIDENCE COVER THE FAR E CARIBBEAN E OF 67W NOTED IN WATER 
VAPOR IMAGERY BRINGING GENERALLY FAIR WEATHER TO THAT PORTION OF 
THE BASIN. BESIDES NEAR THE FRONT...MODERATE TRADEWINDS ARE 
ACROSS MUCH OF THE BASIN. EXPECT THE FRONT TO DRIFT N AS A WARM 
FRONT OVER THE NEXT 24 HRS AS WEAK LOW PRESSURE DEVELOPS ALONG 
THE FRONT SW OF JAMAICA.

ATLANTIC OCEAN...
AN OCCLUDED 970 MB LOW IS LOCATED OFF THE NRN NEW ENGLAND COAST 
NEAR 42N55W WITH A COLD FRONT ENTERING INTO THE DISCUSSION AREA 
NEAR 32N43W CONTINUING ALONG 26N51W 23N62W BECOMING STATIONARY 
TO HISPANIOLA AND INTO THE CARIBBEAN. A SECONDARY COLD FRONT 
TRAILS BEHIND THE PRIMARY FRONT DEMARCATING A SECOND SURGE OF 
COLD AIR EXTENDING FROM 31N50W TO 29N59W. SCATTERED SHOWERS ARE 
WITHIN 60 NM OF THE PRIMARY FRONT...AND FARTHER E N OF 24N 
BETWEEN 28W-44W. A LARGE AREA OF STRATOCUMULUS CLOUDS AND STRONG 
W-NW WINDS ARE BEHIND THE FRONT. A PAIR OF WEAK HIGHS...A 1017 
MB HIGH NEAR 17N45W...AND A 1016 MB HIGH NEAR 18N31W..COVER THE 
S CENTRAL ATLC SUPPORTED BY AN UPPER LEVEL RIDGE COVERING THE 
AREA S OF 30N CENTERED E OF THE LESSER ANTILLES NEAR 15N58W. A 
SHORTWAVE UPPER TROUGH OFF THE COAST OF PORTUGAL SUPPORTS A 
DYING STATIONARY FRONT EXTENDING ACROSS SPAIN TO THE CANARY 
ISLANDS. SCATTERED SHOWERS ARE NEAR THE FRONT N OF 26N BETWEEN 
10W-16W.

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

$$
WALTON