[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN DEC 20 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 4N30W 1N52W. SCATTERED
MODERATE CONVECTION IS FROM 1N-5N BETWEEN 31W-52W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE RIDGE AXIS EXTENDS FROM THE TEXAS GULF COAST ALONG THE
EASTERN MEXICO GULF COAST TO OVER NORTHERN PORTIONS OF CENTRAL
AMERICA WITH SURFACE HIGH PRESSURE EXPANDING EASTWARD TO COVER
THE GULF...YUCATAN PENINSULA...AND FLORIDA PENINSULA. N-NE WINDS
ARE NOTED FROM RECENT ASCAT AND WINDSAT SCATTEROMETER PASSES AS
WELL AS SHIP AND BUOY OBSERVATIONS ACROSS THE GULF THIS MORNING
AND AFTERNOON AS THE SURFACE HIGH PRESSURE IS FORECAST TO REMAIN
THE MAIN EMPHASIS ACROSS THE GULF THROUGH MONDAY. ALOFT...MOIST
SWLY UPPER LEVEL FLOW DOMINATES ACROSS THE GULF EAST OF AN UPPER
LEVEL TROUGH AXIS EXTENDING FROM DEEP SOUTHERN TEXAS ACROSS
CENTRAL MEXICO AND INTO THE TROPICAL EASTERN PACIFIC TO 8N104W.
PLENTIFUL MIDDLE TO UPPER LEVEL MOISTURE IS ADVECTING N-NE
ACROSS SOUTHERN MEXICO AND THE SW GULF WITH POSSIBLE ISOLATED
SHOWERS S OF 25N W OF 90W.

CARIBBEAN SEA...
AS OF 2100 UTC...A COLD FRONT EXTENDS FROM THE SW NORTH ATLC
THROUGH THE WINDWARD PASSAGE TO 18N77W NEAR JAMAICA. THE FRONT
THEN BECOMES STATIONARY FROM JAMAICA ALONG 16N80W TO THE
NORTHERN COSTA RICA COAST NEAR 11N84W. THIS FRONT IS SUPPORTED
ALOFT BY AN UPPER LEVEL TROUGH LOCATED IN THE W ATLC NORTH OF
THE DISCUSSION AREA OFF THE EASTERN U.S. SEABOARD FROM CAPE COD
TO THE GEORGIA COAST. HOWEVER...MOST OF THE CARIBBEAN IS UNDER
THE INFLUENCE OF A BROAD UPPER LEVEL RIDGE WITH AXIS FROM NW
VENEZUELA OVER PUERTO RICO TO BEYOND 32N60W IN THE W ATLC. W OF
70W...MIDDLE TO UPPER LEVEL MOISTURE FROM THE EASTERN PACIFIC IS
ADVECTING ACROSS THE WESTERN CARIBBEAN AND CENTRAL AMERICA AHEAD
OF AN UPPER LEVEL TROUGH AXIS LOCATED ACROSS CENTRAL MEXICO.
LOW-LEVEL CONVERGENCE OF EASTERLY TRADEWINDS NEAR THE STATIONARY
FRONT ALONG WITH UPPER LEVEL DIFFLUENCE W OF THE UPPER LEVEL
RIDGE AXIS IS GENERATING SCATTERED SHOWERS WITHIN 120 NM EITHER
SIDE OF THE FRONT. A PRE-FRONTAL SURFACE TROUGH IS ANALYZED FROM
17N73W TO 9N75W AND DENOTES A SUBTLE WIND SHIFT AND CYCLONIC
CURVATURE OVER THE CENTRAL CARIBBEAN. ISOLATED SHOWERS ARE
WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH WITH ISOLATED
SHOWER ACTIVITY POSSIBLE W TO THE STATIONARY FRONT. E OF 70W...
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...
AN OCCLUDED 977 MB LOW IS CENTERED OFF THE NEW ENGLAND COAST
NEAR 40N68W WITH A COLD FRONT EXTENDING INTO THE DISCUSSION AREA
NEAR 32N60W CONTINUING SW ALONG 25N67W TO THE WINDWARD PASSAGE
NEAR 20N73W AND INTO THE WESTERN CARIBBEAN SEA. LOW-LEVEL
CONVERGENCE NEAR THE COLD FRONT IS GENERATING SCATTERED SHOWERS
WITHIN 120 NM EITHER SIDE OF THE FRONT. BEHIND THE FRONT COLD
AIR STRATOCUMULUS CLOUDS AND STRONG NW WINDS FOLLOW THE FRONT
WITH A MUCH COOLER AND DRIER AIRMASS IN PLACE ACROSS THE W ATLC.
ACROSS THE EASTERN ATLC...ANOTHER COLD FRONT ENTERS THE REGION
NEAR 32N19W AND EXTENDS SW ALONG 25N25W TO 20N40W WHERE IT
CONTINUES AS A STATIONARY FRONT TO NEAR 20N46W. SCATTERED
SHOWERS AND POSSIBLE ISOLATED TSTMS ARE OCCURRING WITHIN 120 NM
E OF THE FRONT N OF 23N WHILE ISOLATED SHOWERS LINGER WITHIN 120
NM EITHER SIDE OF THE COLD AND STATIONARY FRONT W OF 28W. THIS
FRONTAL SYSTEM IS SUPPORTED ALOFT BY AN UPPER LEVEL TROUGH WITH
AXIS EXTENDING FROM 32N18W TO 12N34W. ELSEWHERE ACROSS THE
REMAINDER OF THE ATLC A SURFACE RIDGE IS IN PLACE ANCHORED BY A
1018 MB HIGH CENTERED NEAR 23N47W AND A 1019 MB HIGH CENTERED
NEAR 20N23W. THE SURFACE RIDGE AXIS EXTENDS FROM THE 1019 MB
HIGH ALONG 17N40W TO THE EASTERN CARIBBEAN NEAR 15N64W.
ALOFT...THIS SURFACE RIDGE IS SUPPORTED BY BROAD ANTICYCLONIC
FLOW LOCATED OVER THE CENTRAL ATLC WITH PRIMARILY NW TO N FLOW
DOMINATING E OF 62W.

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

$$
HUFFMAN





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