000
AXNT20 KNHC 112339
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE DEC 11 2012

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 2245 UTC.

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

THE MONSOON TROUGH EXTENDS ACROSS AFRICA TO THE COAST OF SIERRA 
LEONE AT 9N13W WHERE IT TRANSITIONS INTO ITCZ AND CONTINUES 
ALONG 7N20W 4N34W 4N49W. NO DEEP CONVECTION IS NEAR THE AXIS. 
ACTIVITY NORTH OF THE WESTERN PORTION OF THE ITCZ IS ASSOCIATED 
WITH AN UPPER LEVEL TROUGH AND WILL BE DISCUSSED IN THE ATLC 
SECTION. 
 
...DISCUSSION...

THE GULF OF MEXICO...
MOIST SOUTHWESTERLY FLOW ALOFT COVERS THE GULF OF MEXICO BETWEEN 
AN UPPER LEVEL TROUGH OVER THE CENTRAL CONUS AND AN UPPER LEVEL 
RIDGE OVER THE WEST ATLC. AT THE SURFACE...A COLD FRONT BISECTS 
THE BASIN EXTENDING FROM NE FLORIDA NEAR 31N82W TO 23N93W 
BECOMING STATIONARY TO THE MEXICO COAST AT 19N96W...AS OF 2100 
UTC. A SPOT 1013 MB LOW IS ANALYZED OVER NORTHERN FLORIDA ALONG 
THE AXIS AT 30N83W WHERE LOWER PRESSURES WERE OBSERVED. 
WIDESPREAD SHOWERS/ISOLATED THUNDERSTORMS EXTEND NW OF THE FRONT 
CONTINUING ALMOST TO THE TEXAS COAST. ALSO AS OF 2100 UTC...A 
SURFACE TROUGH WAS ADDED EAST OF THE FRONT ALONG 25N86W TO 
20N89W. WIDESPREAD SHOWERS/SCATTERED THUNDERSTORMS ARE EAST OF 
THE AXIS WITHIN 200 NM. THIS ACTIVITY CONTINUES TOWARDS THE NE 
TO CENTRAL FLORIDA. ONLY A FEW LARGE CELLS OF 
SHOWERS/THUNDERSTORMS CONTINUE ACROSS CENTRAL FLORIDA. THE 
SOUTHERN PORTION OF THE FRONT IS EXPECTED TO STALL...WHILE THE 
NORTHERN PORTION CONTINUES SLOWLY EASTWARD UNTIL LATER IN THE 
WEEK WHEN IT MOVES MORE QUICKLY THROUGH THE WESTERN ATLC. 

THE CARIBBEAN SEA...
UPPER LEVEL RIDGING ACCOMPANIED BY DRY AIR ALOFT COVERS THE 
CARIBBEAN WITH AXIS ALONG 73W. FAIR CONDITIONS PREVAIL EXCEPT 
FOR SCATTERED SHOWERS/THUNDERSTORMS MOVING OFF THE YUCATAN 
PENINSULA INTO THE NW CARIBBEAN EAST OF A SURFACE TROUGH IN THE 
GULF OF MEXICO. SIMILAR ACTIVITY IS ALSO ACROSS PANAMA 
ASSOCIATED WITH THE MONSOON TROUGH SOUTH OF THE COUNTRY. 
TRADEWIND FLOW OF 15-20 KT SPREADS ACROSS MUCH OF THE AREA WITH 
ONLY A FEW ISOLATED SHOWERS EMBEDDED WITHIN THE FLOW. EXPECT 
LITTLE CHANGE OVER THE NEXT 24 HOURS. 

THE ATLANTIC OCEAN...
AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS IS EAST OF NE FLORIDA 
FROM 27N-32N BETWEEN 76W-81W AHEAD OF A COLD FRONT IN THE GULF 
OF MEXICO. THE REMAINDER OF THE WEST ATLC IS QUIET INFLUENCED BY 
A LARGE SURFACE RIDGE ANCHORED BY A 1028 MB HIGH NEAR 33N53W. 
THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE EXTENDING FROM 
THE CARIBBEAN INTO THE W ATLC ALONG 21N72W 35N60W. THE UPPER 
RIDGE CONTINUES OVER THE NORTH CENTRAL ATLC SUPPORTING A SECOND 
1029 MB SURFACE HIGH CENTER NEAR 35N40W...WHICH IS PROVIDING 
SURFACE RIDGING ACROSS MUCH OF THE CENTRAL AND EASTERN ATLC. 
HOWEVER...AN UPPER LEVEL TROUGH EXTENDS FROM THE NE ATLC TO NEAR 
31N26W CONTINUING WESTWARD TO 30N42W AND THEN SW TO NEAR 12N61W. 
A SHEAR AXIS...REMNANTS OF A FRONTAL BOUNDARY EXTENDS ALONG 
19N34W 16N45W 10N57W. DIFFLUENCE ALOFT AROUND THE UPPER TROUGH 
IS SUPPORTING A LARGE AREA OF SHOWERS/POSSIBLE THUNDERSTORMS UP 
TO 350 NM SOUTH OF THE SHEAR AXIS. SIMILAR ACTIVITY ALSO EXTENDS 
UP TO 250 NM NORTH OF THE AXIS BETWEEN 34W-48W. UPPER LEVEL 
RIDGING COVERS THE REMAINDER OF THE TROPICAL EASTERN ATLC. 

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

$$
WALTON