000
AXNT20 KNHC 150541
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
105 AM 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0500 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N9W 6N17W 6N32W 1N51W. ISOLATED 
MODERATE CONVECTION IS WITHIN 60 NM N OF THE AXIS BETWEEN 
24W-28W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0300 UTC...A SQUALL LINE EXTENDS FROM S CENTRAL GEORGIA 
CLIPPING THE FLORIDA PANHANDLE TO THE CENTRAL LOUISIANA 
COASTLINE. RADAR IMAGERY INDICATES STRONG SHOWERS/POSSIBLE 
THUNDERSTORMS AFFECTING THE N CENTRAL GULF COAST...AND IMMEDIATE 
COASTAL WATERS N OF 29N. FLASH FLOOD WATCHES AND WARNINGS ARE 
ALREADY IN AFFECT FOR PORTIONS OF THE FLORIDA 
PANHANDLE...ALABAMA...MISSISSIPPI...AND LOUISIANA. A DYING 
STATIONARY FRONT EXTENDS DOWN THE TEXAS COASTLINE WITH ISOLATED 
SHOWERS POSSIBLE WITHIN 90 NM OF THE COASTLINE. MAINLY SWLY FLOW 
ALOFT COVERS THE BASIN. BESIDES THE MOISTURE ALONG THE FAR NRN 
GULF...THE REMAINDER OF THE AREA IS COVERED BY DRY AIR ALOFT 
EVIDENT ON WATER VAPOR IMAGERY SUPPORTING GENERALLY FAIR WEATHER 
AND WEAK SURFACE RIDGING ACROSS THE BASIN. SE RETURN FLOW IS 
OVER MUCH OF THE GULF AROUND THE WEAK SURFACE RIDGE AND AHEAD OF 
THE NEXT COLD FRONT FORECAST TO MOVE OFF THE TEXAS 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 LATER TODAY. STRONG SUBSIDENCE IS ACROSS THE BASIN 
AROUND AN UPPER LEVEL RIDGE CENTERED IN THE N CENTRAL CARIBBEAN 
NEAR 19N75W PROVIDING GENERALLY FAIR WEATHER ACROSS THE AREA. 
HOWEVER...ISOLATED LOW-LEVEL SHOWERS EMBEDDED IN THE ELY TRADES 
ARE MOVING QUICKLY ACROSS PORTIONS OF THE CARIBBEAN CONCENTRATED 
NEAR THE WINDWARD ISLANDS AND S OF HISPANIOLA. EXPECT LITTLE 
CHANGE OVER THE NEXT 24 HRS...EXCEPT FOR WINDS NEAR THE COAST OF 
COLOMBIA DIMINISHING BELOW GALE FORCE. 

ATLANTIC OCEAN...
A SHORTWAVE UPPER LEVEL TROUGH N OF THE DISCUSSION AREA SUPPORTS 
A COLD FRONT THAT CLIPS THE SW N ATLC ALONG 32N61W 31N70W 
BECOMING STATIONARY TO THE GEORGIA COASTLINE NEAR 31N81W. 
POSSIBLE ISOLATED SHOWERS ARE S OF THE FRONT FROM 27N-30N 
BETWEEN 55W-67W. ELSEWHERE ACROSS THE W ATLC...A BROAD SURFACE 
RIDGE DOMINATES ANCHORED BY A 1023 MB HIGH NEAR 27N63W. THE 
SURFACE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE EXTENDING 
FROM THE CARIBBEAN. FARTHER E...A DEEP LAYER UPPER LEVEL TROUGH 
IS SUPPORTING A COLD FRONT EXTENDING FROM E OF THE AZORES 
ISLANDS ENTERING THE DISCUSSION AREA NEAR 32N22W ALONG 27N25W 
BECOMING A DYING FRONT NEAR 23N31W TO 21N39W. A SHEAR LINE 
CONTINUES FROM THE DRYING FRONT ALONG 20N48W 18N56W 18N62W. 
ISOLATED SHOWERS ARE WITHIN 60 NM OF THE FRONT AXIS...AND 
POSSIBLE ALONG THE SHEAR LINE. WEAK HIGH PRESSURE IS SE OF THE 
FRONT ANCHORED BY A 1016 MB HIGH NE OF THE CAPE VERDE ISLANDS 
NEAR 19N20W.

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

$$
WALTON