000
AXNT20 KNHC 181750
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN DEC 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1715 UTC.

...ITCZ/MONSOON TROUGH...
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 7N12W TO 
5N25W TO 8N50W TO 6N56W. SCATTERED MODERATE CONVECTION WITHIN 
180 NM N OF AXIS FROM 30W-37W.

...DISCUSSION...
GULF OF MEXICO...
UPPER LEVEL CONFLUENCE IS NOTED ACROSS THE GULF AS AN UPPER 
LEVEL LONGWAVE TROUGH REMAINS TO THE NE OFF THE SE U.S. COAST 
THIS FLOW IS PRODUCING MODERATE TO STRONG SUBSIDENCE WITH DRY 
STABLE AIR AT THE MIDDLE AND UPPER LEVELS ACROSS MUCH OF THE 
GULF THE ONLY EXCEPTION BEING THE FAR NW GULF WHERE HIGH LEVEL 
MOISTURE IS MOVING THROUGH THE AREA. A WEAKENING COLD FRONT IS 
OFF THE SW FLORIDA COAST. THE FRONT IS EXPECTED TO DISSIPATE BY 
THIS EVENING. OVERCAST LOW CLOUDS ARE ALONG THE MEXICAN COAST S 
OF 26N W OF 95W. OTHERWISE SCATTERED/BROKEN LOW CLOUDS ARE 
ELSEWHERE S OF 26N. BY MON SLY RETURN FLOW IS EXPECTED TO 
RE-ESTABLISH OVER PORTIONS OF THE WESTERN GULF AS AN AREA OF LOW 
PRESSURE DEVELOPS OVER NORTH TEXAS AND OKLAHOMA. THE NEXT COLD 
FRONT IS THEN FORECAST TO ENTER THE NW GULF EARLY TUE.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC FLOW DOMINATES THE ENTIRE CARIBBEAN. 
UPPER LEVEL DIFFLUENT FLOW BETWEEN THE RIDGE AND AN UPPER TROUGH 
IN THE EASTERN PACIFIC IS ENHANCING CONVECTION IN THE SW 
CARIBBEAN OFF THE COAST OF PANAMA. STRONG SUBSIDENCE IS ACROSS 
THE EASTERN CARIBBEAN E OF AROUND 70W...WITH HIGH LEVEL MOISTURE 
ACROSS THE REMAINDER OF THE CARIBBEAN W OF 70W. OTHERWISE 
ISOLATED SHOWERS ARE ACROSS THE REMAINDER OF THE CARIBBEAN. 
STRONG TRADES IN THE 20-25 KT RANGE FROM 68W-80W. HIGH PRES IS 
FORECAST TO REMAIN ANCHORED EAST OF THE BAHAMAS THROUGH AT LEAST 
TUE MAINTAINING THE AREA OF INCREASED E-NE TRADES.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH OFF THE EASTERN U.S. COAST SUPPORTS A COLD 
FRONT ANALYZED FROM 32N67W S FLORIDA. A FEW LOW TOPPED SHOWERS 
ARE OCCURRING WITHIN 90 NM SE OF THE FRONT. A 105-115 KT 
JETSTREAM ENTERS THE AREA NEAR 32N76W TO 30N70W THEN NE TO 
32N65W. AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE 32N55W TO 
HISPANIOLA. EXCEPT FOR HIGH LEVEL MOISTURE OVER THE CENTRAL 
BAHAMAS STRONG SUBSIDENCE WITH DRY/STABLE AIR AT THE MIDDLE AND 
UPPER LEVEL IS ACROSS THE AREA N OF 12N W OF 50W. AN UPPER LEVEL 
LOW IS CENTERED NEAR 27N48W WITH TROUGH EXTENDING S TO 12N54W,
STATIONARY FRONT ENTERS THE DISCUSSION AREA AT 32N50W TO 1010 MB 
LOW PRES NEAR 27N49W THEN TROUGH FROM THE LOW TO 25N48W SW TO 
19N53W. A DISSIPATING STATIONARY FRONT EXTENDS FROM 27N46W TO 
17N48W THEN CONTINUES AS A TROUGH TO 12N50W. SCATTERED SHOWERS 
AND ISOLATED TSTMS ARE ALONG THE DISSIPATING FRONT FROM 27N-22N. 
ISOLATED LOW TOPPED SHOWERS ARE ALONG THE REMAINDER OF THE 
DISSIPATING STATIONARY FRONT. A 1035 MB HIGH PRES IS CENTERED N 
OF THE AREA SE OF THE AZORES NEAR 36N26W.

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

$$
DGS