000
AXNT20 KNHC 191743
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
105 PM EST SAT DEC 19 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 
2315 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 8N13W 3N30W 2N51W. ISOLATED 
MODERATE CONVECTION IS FROM 1N-4N BETWEEN 24W-30W. SIMILAR 
CONVECTION IS WITHIN 180 NM NORTH OF THE AXIS BETWEEN 40W-51W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE RIDGE AXIS EXTENDS FROM SOUTHERN TEXAS ALONG THE 
EASTERN MEXICO GULF COAST TO OVER NORTHERN PORTIONS OF CENTRAL 
AMERICA WITH SURFACE HIGH PRESSURE EXPANDING EASTWARD TO COVER 
THE GULF AND FLORIDA PENINSULA. NORTHERLY WINDS ARE NOTED ON 
SHIP AND BUOY OBSERVATIONS ACROSS THE GULF THIS AFTERNOON AS 
SURFACE HIGH PRESSURE IS FORECAST TO BUILD IN ACROSS THE 
NORTHERN GULF COAST THROUGH MONDAY. ALOFT...MOIST SWLY UPPER 
LEVEL FLOW DOMINATES ACROSS THE GULF AHEAD OF AN UPPER LEVEL 
TROUGH AXIS EXTENDING ACROSS NORTHERN MEXICO AND INTO THE 
TROPICAL EASTERN PACIFIC.

CARIBBEAN SEA...
AS OF 2100 UTC...A COLD FRONT EXTENDS FROM THE SW NORTH ATLC 
ACROSS EASTERN CUBA AND INTO THE NW CARIBBEAN TO NEAR 20N80W. 
THIS FRONT IS SUPPORTED ALOFT BY A VIGOROUS UPPER LEVEL TROUGH 
LOCATED OFF THE NORTH CAROLINA ATLC COAST. ISOLATED SHOWERS ARE 
OCCURRING WITHIN 30 NM E OF THE FRONT. THE REMAINDER OF THE 
CARIBBEAN IS UNDER THE INFLUENCE OF A BROAD UPPER LEVEL RIDGE 
WITH AXIS ALONG 78W. W OF 78W...MIDDLE TO UPPER LEVEL MOISTURE 
FROM THE EASTERN PACIFIC IS BEING ADVECTED ACROSS THE NW 
CARIBBEAN AND NORTHERN PORTIONS OF CENTRAL AMERICA AHEAD OF THE 
NEXT UPPER LEVEL TROUGH AXIS LOCATED ACROSS NORTHERN MEXICO. E 
OF 78W...MAINLY DRY AIR AND STRONG SUBSIDENCE IS NOTED IN THE 
UPPER LEVELS ON WATER VAPOR IMAGERY WHILE AT THE SURFACE 
EASTERLY TRADES UP TO 20 KT CONTINUE AND GENERALLY FAIR SKIES 
PREVAIL. 

ATLANTIC OCEAN...
A 988 MB LOW IS CENTERED OFF THE NORTH CAROLINA COAST NEAR 
35N75W WITH A COLD FRONT EXTENDING INTO THE DISCUSSION AREA NEAR 
32N74W CONTINUING S-SW ALONG 25N76W TO EASTERN CUBA NEAR 22N77W 
AND INTO THE NW CARIBBEAN SEA. A PRE-FRONTAL SURFACE TROUGH IS 
ANALYZED FROM 31N71W TO 24N74W WITH SCATTERED SHOWERS AND 
ISOLATED TSTMS OCCURRING WITHIN 120 NM E OF THE SURFACE TROUGH. 
THE FRONT DENOTES A NOTICEABLE WIND SHIFT IN OBSERVATIONS WHILE 
A POST-FRONTAL TROUGH ANALYZED FROM 29N77W TO 24N80W EXHIBITS A 
CONTRAST IN DEWPOINTS WITH A MUCH COOLER AND DRIER AIRMASS 
SETTLING IN ACROSS THE W ATLC NW OF THE COLD FRONT. FARTHER EAST 
ACROSS THE CENTRAL ATLC...ANOTHER COLD FRONT ENTERS THE REGION 
NEAR 32N29W AND EXTENDS SW ALONG 25N35W TO 21N49W WHERE IT 
CONTINUES AS A STATIONARY FRONT TO NEAR 23N60W. SCATTERED 
SHOWERS AND TSTMS ARE OCCURRING WITHIN 200 NM E OF THE FRONT N 
OF 22N WHILE ISOLATED SHOWERS LINGER WITHIN 120 NM EITHER SIDE 
OF THE COLD AND STATIONARY FRONT W OF 40W. THIS FRONTAL SYSTEM 
IS SUPPORTED ALOFT BY AN UPPER LEVEL TROUGH WITH AXIS EXTENDING 
FROM 32N27W TO 17N38W. THE EASTERN ATLC IS UNDER THE INFLUENCE 
OF A SURFACE RIDGE ANCHORED BY A 1018 MB HIGH CENTERED NEAR 
24N21W. THE SURFACE RIDGE AXIS EXTENDS FROM THE HIGH ALONG  
18N40W TO THE LEEWARD ISLANDS NEAR 16N60W. 

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

$$
HUFFMAN