000
AXNT20 KNHC 040534
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST SUN JAN 04 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...THE ITCZ...

ITCZ IS CENTERED ALONG 9N13W 4N23W 5N40W 2N51W. SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 75 NM N OF THE 
ITCZ FROM 16W-19W. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE 
FROM 5N TO JUST S OF THE EQUATOR E OF 18W TO ACROSS THE PRIME 
MERIDIAN. 

...DISCUSSION...

GULF OF MEXICO...
UPPER RIDGE ANCHORED OVER CENTRAL AMERICA IS GIVING THE GULF 
STRONG WLY FLOW WITH MID/UPPER LEVEL MOISTURE STREAMING ACROSS 
THE N GULF. A JET STREAM WITH WINDS OF 80-110 KT CROSSES THE N 
GULF AND FLORIDA PENINSULA. A SHORTWAVE UPPER TROUGH IS MOVING E 
OF THE MISSISSIPPI VALLEY PRODUCING AN SQUALL LINE THAT EXTENDS 
FROM SE GEORGIA ACROSS THE FLORIDA PENINSULA BETWEEN PANAMA CITY 
AND PENSACOLA INTO THE GULF TO NEAR 29N87W. THIS SHORTWAVE IS 
ALSO GENERATING A BAND OF HEAVY RAINS AND THUNDERSTORMS ALONG 
THE N GULF COAST WITHIN 30 NM OF 30N FROM THE FLORIDA/ALABAMA 
BORDER TO INLAND OVER SE LOUISIANA MOVING E AT ROUGHLY 30 KT. A 
SURFACE RIDGE ANCHORED IN THE W ATLC COVERS THE E GULF WITH SLY 
RETURN FLOW AROUND THE RIDGE COVERING THE ENTIRE GULF. UPPER 
LEVEL DIVERGENCE IS COMBINING WITH MOISTURE ALOFT AND 
CONVERGENCE WITH THE S SURFACE FLOW IS GIVING THE THE NE GULF 
SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS N OF 26N E 
OF 87W TO OVER FLORIDA. STRONG SUBSIDENCE AND DRY STABLE AIR IS 
GIVING THE S GULF CLEAR SKIES TONIGHT. THE NEXT COLD FRONT IS 
FORECAST TO ENTER THE NW GULF LATE SUN.

CARIBBEAN SEA...
BROAD UPPER RIDGE ANCHORED OVER CENTRAL AMERICA COVERS THE NW 
CARIBBEAN WHILE A SECOND UPPER RIDGE ANCHORED OVER THE E PORTION 
OF SOUTH AMERICA IS GIVING THE REMAINDER OF THE CARIBBEAN SW TO 
W UPPER FLOW. STRONG SUBSIDENCE AND DRY STABLE AIR COVERS THE 
AREA W OF 70W GIVING THAT AREA TRANQUIL WEATHER TONIGHT. 
MODERATE/STRONG ELY TRADE WINDS ARE SUPPLYING THE E CARIBBEAN 
WITH LOW LEVEL MOISTURE AND COUPLED WITH A SURFACE TROUGH THAT 
EXTENDS ALONG 18N70W TO 13N71W ARE GENERATING SCATTERED SHOWERS 
E OF 70W TO ACROSS THE LESSER ANTILLES. 

ATLANTIC...
STRONG WLY FLOW ALOFT COVERS THE W ATLC WITH A JET STREAM OF 
80-100 KT WITHIN 120 NM OF LINE FROM ACROSS FLORIDA NEAR WEST 
PALM BEACH TO 24N70W. DEEP LAYERED TROUGH COVERS THE AREA N OF 
26N FROM 50W-70W WITH THE ACCOMPANYING FRONTAL BOUNDARY JUST N 
OF THE REGION. A SURFACE RIDGE DOMINATES THE ATLC INTO THE E 
GULF OF MEXICO WITH A 1022 MB HIGH NEAR 29N75W AND A 1021 MB 
HIGH NEAR 27N64W. A WEAKNESS IN THE FORM OF A SURFACE TROUGH IS 
BETWEEN THE SURFACE HIGHS ALONG 25N71W ACROSS THE TURKS AND 
CAICOS TO THE WINDWARD PASSAGE. FARTHER TO THE E...A WEAKENING 
STATIONARY FRONT EXTENDS INTO THE CENTRAL ATLC NEAR 32N40W TO 
31N42W WHERE IT CONTINUES AS A SURFACE TROUGH TO 28N47W 
GENERATING SCATTERED SHOWERS WITHIN 180 NM E OF THE FRONT/TROUGH 
N OF 28N. AN UPPER RIDGE COVERS THE AREA S OF 30N FROM 30W-50W 
AND A SURFACE RIDGE COVERS THE E ATLC ANCHORED BY A 1028 MB HIGH 
NEAR 35N24W BRIDGING THE ABOVE FRONT/TROUGH AND GIVING THE E 
ATLC FAIR WEATHER TONIGHT. 

$$
WALLACE