000
AXNT20 KNHC 132356
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE DEC 13 2011

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL 
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2315 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA ENTERING THE E TROPICAL 
ATLC NEAR 9N14W TO 5N15W. THE ITCZ CONTINUES FROM 5N15W ALONG 
5N25W 7N32W TO 5N51W. CLUSTERS OF SCATTERED MODERATE CONVECTION 
ARE WITHIN 75 NM OF LINE FROM 5N13W TO 2N18W. 

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER RIDGE DOMINATES THE GULF THIS EVENING ANCHORED NEAR 
25N90W WITH A RIDGE AXIS EXTENDING N OVER THE GULF COAST STATES 
ALONG THE MISSISSIPPI VALLEY. STRONG SURFACE RIDGE REMAINS OVER 
THE GULF AND ANCHORED BY A 1031 MB HIGH OVER SE TENNESSEE AND A 
1033 MB HIGH OVER S OHIO. FRESH EASTERLY SURFACE FLOW COUPLED 
WITH LOW LEVEL MOISTURE IS GIVING MUCH OF THE GULF MOSTLY CLOUDY 
SKIES WITH PATCHES OF ISOLATED SHOWERS. THE EXCEPTION IS WITHIN 
120 NM ALONG THE COAST OF THE FLORIDA PENINSULA WHERE SKIES ARE 
CLEARING. HIGH PRES N OF THE AREA WILL SHIFT SLOWLY NE THROUGH 
WED ALLOWING FOR SOUTHERLY RETURN FLOW OVER THE W GULF TO SPREAD 
TO E ACROSS ALL OF THE GULF BY WED NIGHT. THE NEXT COLD FRONT 
WILL ENTER THE NW GULF THU NIGHT REACHING FROM SE LOUISIANA TO 
NE MEXICO ON FRI WHERE IT WILL STALL. IT WILL MEANDER ACROSS THE 
N GULF COAST WATERS THEN SINK S AND WEAKEN ALONG 27N THROUGH SUN.

CARIBBEAN SEA...
WEAK PRESSURE PATTERN CONTINUES TO DOMINATE THE CARIBBEAN THIS 
EVENING. A BROAD UPPER RIDGE DOMINATES THE CARIBBEAN WITH THE 
AXIS ALONG 73W DRAWING TROPICAL MOISTURE N OVER THE S/CENTRAL 
CARIBBEAN AND COUPLED WITH THE MONSOON TROUGH THAT EXTENDS FROM 
COLOMBIA NEAR 11N75W ACROSS PANAMA/COSTA RICA NEAR 10N83W INTO 
THE E PACIFIC REGION ARE GENERATING SCATTERED SHOWERS/ISOLATED 
THUNDERSTORMS S OF 14N W OF 75W TO INLAND OVER PANAMA TO 
NICARAGUA. THE REMAINDER OF THE CARIBBEAN IS UNDER MOSTLY FAIR 
CONDITIONS THIS EVENING WITH THE POSSIBLE ISOLATED LOW LEVEL 
SHOWER USHERED IN ON THE EASTERLY TRADE WINDS. THE SURFACE RIDGE 
OVER THE W ATLC WILL STRENGTHEN INCREASING THE TRADE WINDS 
ACROSS THE CARIBBEAN WATERS THROUGH SAT.

ATLANTIC OCEAN...
THE BROAD UPPER TROUGH IS OVER THE W ATLC N OF 23N BETWEEN 
60W-80W SUPPORTING A FRONTAL SYSTEM N OF THE REGION AND A 
SURFACE TROUGH THAT IS ANALYZED FROM 31N62W ALONG 27N64W TO 
22N61W. A DEVELOPING FRONT IS BEGINNING TO FORM TO THE W OF THE 
SURFACE TROUGH AND WILL BE ADDED ON THE 14/0000 UTC MAP. 
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 90 NM OF 
LINE FROM 17N54W TO 28N60W AND WITHIN 150 NM OF LINE FROM 29N61W 
TO BEYOND 32N57W. STRONG SUBSIDENCE AND DRY STABLE AIR COVERS 
THE W ATLC W OF 60W LIMITING SHOWER ACTIVITY OVER THE REMAINDER 
OF THE W ATLC. BROAD UPPER RIDGE COVERS THE E ATLC ANCHORED NEAR 
27N40W WITH A SURFACE RIDGE COVERING THE E ATLC ANCHORED BY A 
1029 MB HIGH JUST N OF THE DISCUSSION AREA NEAR 33N33W. 
DEVELOPING COLD FRONT OVER THE W ATLC WILL EXTEND FROM E OF 
BERMUDA TO JUST E OF THE TURKS AND CAICOS AND WITH THE SURFACE 
TROUGH CURRENTLY IN THE W ATLC WILL MOVE E IN TANDEM INTO THE 
CENTRAL ATLC. SURFACE RIDGE WILL STRENGTHEN ACROSS THE AREA 
THROUGH WED NIGHT. 

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

$$
PAW