000
AXNT20 KNHC 181127
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
705 AM EST FRI DEC 18 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1030 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N8W 5N19W 6N30W 5N40W 2N52W. 
SCATTERED MODERATE/STRONG CONVECTION IS WITHIN 120 NM S AND 60 
NM N OF THE AXIS BETWEEN 10W-26W.

...DISCUSSION...

GULF OF MEXICO...
ENHANCED MOISTURE CONTINUES TO INVADE THE ERN HALF OF THE GULF 
OF MEXICO THIS MORNING AROUND THE E SIDE OF AN UPPER LEVEL 
TROUGH EXTENDING DOWN THE GREAT PLAINS INTO THE W GULF. AS OF 
0900 UTC...A 1003 MB LOW IS S OF NEW ORLEANS LOUISIANA NEAR 
29N90W. A COLD FRONT EXTENDS S FROM THE LOW ALONG 25N89W TO THE 
YUCATAN PENINSULA NEAR 20N90W. A SQUALL LINE IS ANALYZED 160 NM 
AHEAD OF THE FRONT EXTENDING INTO THE NW CARIBBEAN. A WARM FRONT 
EXTENDS E FROM THE LOW ALONG 29N TO THE BIG BEND OF FLORIDA. 
SURFACE CONVERGENCE NEAR THE LOW AND FRONTAL BOUNDARIES ALONG 
WITH DIFFLUENT FLOW ALOFT IS ENHANCING A LARGE AREA OF NUMEROUS 
SHOWERS/SCATTERED THUNDERSTORMS ACROSS THE CENTRAL AND E GULF 
AFFECTING LOUISIANA...ALABAMA...GEORGIA...AND FLORIDA. PORTIONS 
OF ALL FOUR STATES HAVE CURRENT FLOOD WATCHES AND WARNINGS IN 
EFFECT. NEAR GALE FORCE WINDS ARE NEAR THE COLD FRONT AS WELL 
AND EXPECTED TO CONTINUE ACROSS THE CENTRAL AND E GULF THROUGH 
TONIGHT. DRY AIR BUILDS BEHIND THE COLD FRONT EVIDENT IN WATER 
VAPOR IMAGERY. EXPECT CONTINUED WIDESPREAD SHOWER ACTIVITY OVER 
THE CENTRAL AND E GULF...POSSIBLY SEVERE AT TIMES...TO CONTINUE 
OVER THE NEXT 24 HRS AS THE LOW CENTER DEEPENS AND CONTINUES 
MOVING E ACROSS THE NRN GULF. 

CARIBBEAN SEA...
SUBSIDENCE AND DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE WITH 
AXIS ALONG 70W CONTINUES TO KEEP THE CARIBBEAN UNDER GENERALLY 
FAIR CONDITIONS. MOISTURE ASSOCIATED WITH THE LOW PRESSURE 
SYSTEM IN THE GULF OF MEXICO HAS PUSHED INTO THE NW CARIBBEAN 
ENHANCING A LINE OF SHOWERS/THUNDERSTORMS OFF THE YUCATAN 
PENINSULA ALONG A SQUALL LINE ANALYZED FROM 22N86W TO 18N87W. A 
LINE OF ISOLATED SHOWERS EMBEDDED IN ELY FLOW CONTINUES TO MOVE 
QUICKLY FROM THE LESSER ANTILLES TO N OF HONDURAS BISECTING THE 
CARIBBEAN. MODERATE TO FRESH TRADEWINDS PREVAIL ACROSS MUCH OF 
THE BASIN. EXPECT ENHANCED MOISTURE OVER THE NW CARIBBEAN AS THE 
COLD FRONT IN THE CENTRAL GULF REACHES THE YUCATAN CHANNEL LATER 
TODAY.

ATLANTIC OCEAN...
MOISTURE FROM THE GULF OF MEXICO LOW PRESSURE SYSTEM HAS PUSHED 
INTO THE SW N ATLC ENHANCING NUMEROUS SHOWERS OFF THE E COAST OF 
FLORIDA W OF 78W. A DEEP LAYER TROUGH ACROSS THE NW ATLC 
SUPPORTS A COLD FRONT EXTENDING FROM THE CENTRAL ATLC NEAR 
32N42W ALONG 24N56W 24N69W TO NEAR NASSAU BAHAMAS. ISOLATED 
SHOWERS ARE WITHIN 90 NM AHEAD OF THE FRONT AXIS...WITH NUMEROUS 
SHOWERS FARTHER E N OF 25N BETWEEN 34W-42W. FARTHER E...A WEAK 
1016 MB HIGH IS CENTERED NEAR 23N32W POSITIONED BETWEEN THE COLD 
FRONT IN THE CENTRAL ATLC AND A SECOND COLD FRONT TO THE E 
EXTENDING FROM THE CANARY ISLANDS NEAR 32N13W TO W OF THE CAPE 
VERDE ISLANDS NEAR 17N27W. THE SECOND COLD FRONT IS SUPPORTED BY 
AN UPPER LEVEL TROUGH CENTERED NE OF THE AZORES ISLANDS. THE 
UPPER LEVEL TROUGH IS ALSO ENHANCING CONVECTION ALONG THE E 
PORTION OF THE ATLC ITCZ. 

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

$$
WALTON