000
AXNT20 KNHC 122347
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON DEC 12 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 13N17W TO 10N20W. THE ITCZ CONTINUES FROM 10N20W ALONG 
7N29W 5N37W TO 4N47W. SCATTERED MODERATE CONVECTION IS WITHIN 75 
NM OF LINE FROM 8N15W TO 7N28W. 

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH IS MOVING OFF THE COAST OF THE E CONUS COVERING 
THE E GULF TO OVER THE FLORIDA PENINSULA SUPPORTING A WEAK 
SURFACE TROUGH THAT AT 12/2100 UTC EXTENDS FROM JUST OFF THE 
COAST OF DAYTONA BEACH OVER LAKE OKEECHOBEE TO ACROSS THE UPPER 
FLORIDA KEYS TO 24N81W IN THE STRAITS OF FLORIDA. THE REMAINDER 
OF UPPER LEVELS ACROSS THE GULF ARE NEAR ZONAL WESTERLY FLOW. 
STRONG SURFACE RIDGE REMAINS OVER THE GULF AND ANCHORED BY A 
1034 MB HIGH ALONG THE COAST OF NEW JERSEY. EASTERLY SURFACE 
FLOW COUPLED WITH LOW LEVEL MOISTURE IS GIVING THE REMAINDER OF 
THE GULF MOSTLY CLOUDY SKIES WITH PATCHES OF SCATTERED SHOWERS. 
HIGH PRESSURE N OF THE AREA SHIFTS E ALLOWING THE S RETURN FLOW 
OVER THE W GULF THAT WILL THEN SPREAD E ACROSS ALL OF THE GULF 
BY WED NIGHT. THE NEXT COLD FRONT WILL ENTER THE NW GULF WATERS 
THU NIGHT AND STALL BRIEFLY FROM SE LOUISIANA TO SE TEXAS ON FRI 
THEN DRIFT W FRI NIGHT INTO SAT.

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 10N75W ALONG 10N80W THEN ACROSS PANAMA/COSTA RICA 
NEAR 9N83W INTO THE E PACIFIC REGION ARE GENERATING SCATTERED 
SHOWERS/ISOLATED THUNDERSTORMS S OF 15N BETWEEN 72W-84W. 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 MOVING OFF THE E CONUS EXTENDS INTO THE 
NW ATLC COUPLED WITH LOW LEVEL MOISTURE IS GIVING THE W ATLC N 
OF 26N W OF 77W MOSTLY CLOUDY SKIES WITH SCATTERED SHOWERS. THE 
BROAD UPPER RIDGE OVER THE CARIBBEAN COVERS SW ATLC S OF 22N 
BETWEEN 62W-80W WITH STRONG SUBSIDENCE AND DRY STABLE AIR S OF 
30N W OF 60W THUS LIMITING SHOWER ACTIVITY OVER THE REMAINDER OF 
THE W ATLC. A BROAD ELONGATED UPPER TROUGH IS OVER THE CENTRAL 
ATLC EXTENDING FROM 29N61W TO 20N56W SUPPORTING A SURFACE TROUGH 
ANALYZED FROM 29N65W TO 20N66W. SCATTERED SHOWERS/ISOLATED 
THUNDERSTORMS ARE FROM 14N-20N BETWEEN 46W-60W AND WITHIN 90/120 
NM OF LINE FROM 20N52W TO 30N60W. BROAD UPPER RIDGE COVERS THE E 
ATLC ANCHORED NEAR 32N38W WITH A SURFACE RIDGE COVERING THE E 
ATLC ANCHORED BY A 1031 MB HIGH N OF THE DISCUSSION AREA NEAR 
34N35W. THE SURFACE TROUGH IN THE W/CENTRAL ATLC WILL MOVE E 
THROUGH LATE TUE. SURFACE RIDGE WILL STRENGTHEN ACROSS THE AREA 
THROUGH WED NIGHT. 

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

$$
PAW