000
AXNT20 KNHC 151731
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
105 PM EST TUE DEC 15 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1715 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 6N10W 4N20W 6N35W 2N51W. 
SCATTERED MODERATE CONVECTION IS FROM 1N-3N BETWEEN 11W-14W. 
WIDELY SCATTERED MODERATE CONVECTION IS FROM 6N-8N BETWEEN 
25W-29W...AND FROM 5N-7N BETWEEN 35W-38W. 

...DISCUSSION...

GULF OF MEXICO...
AS OF 1500 UTC...A PRE-FRONTAL TROUGH IS OVER THE NW GULF OF 
MEXICO FROM S LOUISIANA TO THE S TEXAS COAST ALONG 30N92W 28N95W 
26N96W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE 
TROUGH. FLASH FLOOD WATCHES AND FLOOD WARNINGS REMAIN IN EFFECT 
FOR PORTIONS OF THE GULF COAST STATES. A COLD FRONT EXTENDS FROM 
PORT ARTHUR TEXAS INLAND TO EAGLE PASS TEXAS ALONG 30N94W 28N98W 
29N100W. IN THE UPPER LEVELS...THE BACK SIDE OF AN UPPER LEVEL 
RIDGE IS PRODUCING SW FLOW OVER THE ENTIRE GULF OF MEXICO. AN 
UPPER LEVEL TROUGH IS OVER THE GREAT PLAINS SUPPORTING THE COLD 
FRONT. SIGNIFICANT UPPER LEVEL MOISTURE IS OVER THE NW GULF.
THE REMAINDER OF THE BASIN HAS DRY AIR ALOFT PRODUCING FAIR 
WEATHER ACROSS THE BASIN. ISOLATED SHOWERS ARE NOTED ACROSS S 
FLORIDA AND THE FAR SE GULF S OF 25N E OF 86W. EXPECT... 
CONTINUED CONVECTION AND SHOWER ACTIVITY ACROSS THE N GULF AS 
THE COLD FRONT MOVES OFF THE COAST LATER TODAY.

CARIBBEAN SEA...
STRONG ELY TRADEWINDS CONTINUE ACROSS THE CARIBBEAN AS A RESULT 
OF A STRONG PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE W 
ATLC AND LOW PRESSURE OVER NRN COLOMBIA. GALE FORCE WINDS TO 35 
KT REMAIN NEAR THE COAST OF COLOMBIA AND ARE FORECAST TO PERSIST 
THROUGH THIS EVENING. PATCHES OF BROKEN LOW CLOUDS WITH ISOLATED 
SHOWERS DOTS THE CARIBBEAN NAMELY OVER THE E CARIBBEAN E OF 75W 
FROM 11N-17N...AND THE W CARIBBEAN AND CENTRAL AMERICA W OF 80W 
FROM 8N-20N. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE IS OVER 
THE CARIBBEAN WITH AXIS ALONG 75W. VERY STRONG SUBSIDENCE IS 
ACROSS THE BASIN SUPPRESSING DEEP CONVECTION. EXPECT OVER THE 
NEXT 24 HOURS FOR THE STRONG PRESSURE GRADIENT ACROSS THE BASIN 
TO WEAKEN AS A COLD FRONT MOVES ACROSS THE GULF OF MEXICO AND 
THE GALE FORCE WINDS TO DIMINISH.

ATLANTIC OCEAN...
A 1021 MB HIGH IS OVER THE W ATLANTIC NEAR 27N65W. A COLD FRONT 
IS OVER THE CENTRAL ATLANTIC ALONG 32N50W 30N53W 30N60W 32N70W. 
A COLD FRONT IS OVER THE E ATLANTIC APPROACHING THE CANARY 
ISLANDS ALONG 32N16W 27N20W 21N30W. A DISSIPATING COLD FRONT 
CONTINUES TO 20N40W. SCATTERED SHOWERS ARE WITHIN 30 NM OF THE 
FRONT. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE IS OVER THE W 
ATLANTIC W OF 50W. A BROAD UPPER LEVEL TROUGH IS OVER THE E 
ATLANTIC N OF 20N E OF 50W. ZONAL FLOW IS OVER THE REMAINDER OF 
THE AREA. EXPECT... A COLD FRONT TO EXTEND FROM THE W ATLANTIC 
AT 32N65W TO CENTRAL FLORIDA IN 24 HOURS WITH SHOWERS AND 
CONVECTION. ALSO EXPECT A COLD FRONT OVER THE E ATLANTIC FROM 
THE CANARY ISLANDS TO 22N40W WITH SHOWERS.   

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

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FORMOSA