000
AXNT20 KNHC 132346
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
705 PM EST SUN DEC 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2315 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N11W 3N30W TO THE EQUATOR NEAR 
43W AND INTO NE BRAZIL NEAR 1S46W. SCATTERED MODERATE CONVECTION 
IS WITHIN 50 NM OF 6N13W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...AN UPPER LEVEL SHORTWAVE TROUGH IS EXITING TO 
THE NE ACROSS THE MID-ATLC STATES AND SUPPORTS A STATIONARY 
FRONT DRAPED ACROSS THE SE CONUS AND TRAILING INTO THE GULF NEAR 
GULFPORT MISSISSIPPI CONTINUING ALONG 28N90W 24N96W TO THE 
WESTERN BAY OF CAMPECHE NEAR 20N95W. MOSAIC DOPPLER RADAR AND 
LIGHTNING DATA INDICATE SCATTERED SHOWERS AND ISOLATED TSTMS 
REMAINING N OF 26N BETWEEN 84W-90W...INCLUDING PORTIONS OF THE 
FLORIDA PANHANDLE. ELSEWHERE S OF 26N...ISOLATED SHOWERS LINGER 
WITHIN 90 NM EITHER SIDE OF THE FRONT ACROSS THE WESTERN GULF. A 
WEAK SURFACE RIDGE OF HIGH PRESSURE FOLLOWS NW OF THE FRONT WITH 
MAINLY LOW STRATUS AND FOG BEING REPORTED IN OBSERVATIONS ALONG 
THE TEXAS AND LOUISIANA GULF COASTS. SE OF THE STATIONARY 
FRONT...LIGHT S-SE SURFACE WINDS ARE NOTED AS CAPTURED BY A 
RECENT AFTERNOON ASCAT PASS. VISIBLE SATELLITE IMAGERY ALSO 
CONFIRMS GENERALLY FAIR WEATHER AND RELATIVELY CLEAR SKIES OVER 
THE SE GULF THIS EVENING.

CARIBBEAN SEA...
STRONG EASTERLY TRADES HIGHLIGHT THE CARIBBEAN SEA AS THE 
PRESSURE GRADIENT REMAINS RATHER STRONG BETWEEN HIGH PRESSURE 
OVER THE WESTERN ATLC AND AN AREA OF LOW PRESSURE OVER NORTHERN 
S AMERICA. WINDS TO 35 KT NEAR THE COAST OF COLOMBIA ARE 
FORECAST TO PERSIST THROUGH LATE MONDAY. STRONG SUBSIDENCE IS 
NOTED ON WATER VAPOR IMAGERY AS AN UPPER LEVEL ANTICYCLONIC 
CIRCULATION IS CENTERED IN THE WESTERN CARIBBEAN NEAR 17N80W. 
HOWEVER...THE EASTERLY TRADES ARE USHERING IN ISOLATED POCKETS 
OF LOW-LEVEL SHOWERS ACROSS THE BASIN. AS THE ATLC HIGH WEAKENS 
AND SHIFTS EASTWARD OVER THE NEXT FEW DAYS...IT WILL ALLOW FOR 
THE TRADES TO GRADUALLY DIMINISH BEGINNING WEDNESDAY.

ATLANTIC OCEAN...
AN UPPER LEVEL SHORTWAVE TROUGH IS MOVING NE ACROSS THE MID-ATLC 
STATES AND AS OF 2100 UTC SUPPORTS A STATIONARY FRONT THAT 
EXTENDS ALONG THE CAROLINA COAST TO CENTRAL GEORGIA. AN UPPER 
LEVEL DIFFLUENT PATTERN EAST OF THE FRONT IS GENERATING 
SCATTERED SHOWERS AND ISOLATED TSTMS N OF 30N BETWEEN 70W-81W. 
THE REMAINDER OF THE W ATLC IS INFLUENCED LARGELY BY A STRONG 
SURFACE RIDGE ANCHORED ON A 1030 MB HIGH CENTERED NEAR 35N64W. 
FARTHER EAST INTO THE CENTRAL ATLC...A COLD FRONT ENTERS THE 
DISCUSSION AREA NEAR 32N32W AND EXTENDS SW ALONG 25N43W TO 
22N57W WHERE IT CONTINUES WESTWARD AS A STATIONARY FRONT TO 
24N70W. ISOLATED SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THE 
FRONTAL BOUNDARY. THIS FRONT IS SUPPORTED ALOFT BY AN UPPER 
LEVEL DEEP LAYERED TROUGH ACROSS THE N/CENTRAL ATLC. ELSEWHERE 
SE OF THE COLD FRONT...A SURFACE RIDGE CONTROLS THE EASTERN ATLC 
ANCHORED BY A 1016 MB HIGH CENTERED NEAR 25N29W. 

$$
HUFFMAN