000
AXNT20 KNHC 122338
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON JAN 12 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.

...THE ITCZ...

ITCZ IS CENTERED ALONG 7N10W 4N20W 4N30W 3N40W THEN EQUATOR AT 
50W. SCATTERED MODERATE CONVECTION IS FROM EQ-6N BETWEEN 
27W-40W. SIMILAR CONVECTION IS WITHIN 80 NM S OF AXIS BETWEEN 
15W-25W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...A STATIONARY FRONT EXTENDS ACROSS SOUTH-CENTRAL 
FLORIDA AND THE GULF WATERS ALONG 26N82W 25N90W TO THE BAY OF 
CAMPECHE NEAR 18N93W. A WIDE BAND OF MULTILAYERED CLOUDS WITH 
EMBEDDED SHOWERS IS ASSOCIATED WITH THE FRONT. DOPPLER RADAR 
REVEALS SCATTERED SHOWERS OVER SOUTH FLORIDA AND COASTAL WATERS 
INCLUDING ALSO THE FLORIDA KEYS. THIS STATIONARY FRONTAL 
BOUNDARY WILL BE REINFORCED TUE BY A SECOND COLD FRONT...THAT 
WILL PUSH QUICKLY ACROSS THE NW GULF EARLY TUE MORNING AND MERGE 
WITH THE STALLING FRONT EXTENDING FROM THE FLORIDA KEYS TO THE 
EXTREME W CARIBBEAN BY TUESDAY EVENING. NLY WINDS OF 20 TO 30 
ARE EXPECTED IN THE WAKE OF THE FRONT WITH THE STRONGEST WINDS 
BLOWING ACROSS THE BAY OF CAMPECHE AND THE ISTHMUS OF 
TEHUANTEPEC. THIS WILL RESULT IN A GAP WIND EVENT WITH GALE 
FORCE WINDS IN THE EPAC REGION. IN FACT...AN EARLIER QSCAT PASS 
INDICATED NW WINDS OF 20 TO 30 KT BEHIND THE FRONT OVER THE SW 
PORTION OF THE GULF. SIMILAR SPEED WINDS ARE ALSO OBSERVED OVER 
THE GULF OF TEHUANTEPEC EARLY THIS EVENING. IN THE UPPER 
LEVELS... STRONG SOUTHWESTERLY FLOW WITH SIGNIFICANT UPPER LEVEL 
MOISTURE COVERS THE ENTIRE GULF REGION. THESE UPPER-LEVEL WINDS 
ARE AHEAD OF A BROAD LONG-WAVE TROUGH LOCATED OVER THE CENTRAL 
CONUS WHICH WILL SUPPORT THE AFOREMENTIONED FRONTS.    

CARIBBEAN SEA...
A TIGHT SURFACE PRESSURE GRADIENT BETWEEN HIGH PRES N OF AREA 
AND THE SEMI-PERMANENT SFC LOW OVER COLOMBIA/PANAMA IS PRODUCING 
MODERATE TO STRONG TRADEWINDS WITH OCCASIONAL GUSTS TO GALE 
FORCE ACROSS THE BASIN. AS USUAL...THE STRONGEST WINDS ARE NEAR 
THE COAST OF COLOMBIA. ABUNDANT CLOUDINESS COVERS THE WEST AND 
CENTRAL CARIBBEAN WITH A BAND OF TRANSVERSE HIGH CLOUDS 
EXTENDING FROM CENTRAL AMERICA TO BETWEEN CUBA AND JAMAICA THEN 
TURNING SE ACROSS THE EASTERN CARIBBEAN. THESE CLOUDS ARE MOVING 
AROUND A STRONG UPPER-LEVEL RIDGE WHICH EXTENDS FROM EASTERN 
COLOMBIA AND WESTERN VENEZUELA NWD ACROSS HISPANIOLA INTO THE 
WEST-CENTRAL ATLC TO BEYOND 32N55W. MODERATE TO STRONG 
UPPER-LEVEL SUBSIDENCE DOMINATES THE E CARIBBEAN COURTESY OF 
THIS RIDGE. THE NEXT COLD FRONT IS FORECAST TO REACH WESTERN 
CUBA AND THE NW CARIBBEAN LATE TUE THEN WILL EXTEND FROM CENTRAL 
CUBA TO HONDURAS ON WED.

ATLANTIC OCEAN...
A COLD FRONT ENTERS THE FORECAST AREA NEAR 31N71W THEN CONTINUES 
SW TO SOUTH-CENTRAL FLORIDA CROSSING JUST SOUTH OF LAKE 
OKEECHOBEE. A ROPE CLOUD DELINEATES THE LEADING EDGE OF THE 
FRONT OVER THE W ATLC. JUST AHEAD OF THE FRONT...SW TO S WINDS 
OF 20 TO 25 KT PREVAIL WHILE NE WINDS OF AROUND 15 KT ARE SEEN 
BEHIND THE FRONT. THE REMAINDER OF THE AREA IS UNDER THE 
INFLUENCE OF A SFC RIDGE ANCHORED BY A 1029 MB HIGH SITUATED 
WEST OF THE AZORES NEAR 36N33W. THIS SYSTEM WILL CONTINUE TO 
MOVE EWD DURING THE NEXT 24 HOURS. MOSTLY FAIR WEATHER IS NOTED 
BETWEEN 35W-65W. ALOFT...A RIDGE/TROUGH/RIDGE PATTERN DOMINATES 
THE DISCUSSION AREA. THE UPPER-LEVEL TROUGH STRETCHES ACROSS THE 
CENTRAL ATLC INTO THE DEEP TROPICS WITH THE BASE OF THIS TROUGH 
REACHING 10N58W. UPPER DIFFLUENCE BETWEEN THIS TROUGH AND AN 
UPPER-LEVEL RIDGE OVER THE E ATLC IS SUPPORTING A LARGE AREA OF 
MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS THAT COVERS MUCH OF 
THE E ATLC FROM THE ITCZ ALL THE WAY N TO AROUND 32N.     

$$
GR