000
AXNT20 KNHC 281723
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED JAN 28 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1645 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N7W 2N18W 1N27W 1N47W CROSSING THE 
ITCZ NEAR 50W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
WITHIN 90 NM N OF THE ITCZ FROM 20W-24W. CLUSTERS OF SCATTERED 
MODERATE CONVECTION ARE WITHIN 75 NM OF LINE FROM 3N42W TO THE 
ITCZ NEAR 1N35W. 
 
...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER RIDGE CONTINUES TO DOMINATE MUCH OF THE GULF 
ANCHORED IN THE E PACIFIC REGION AND A DEEP LAYERED TROUGH CLIPS 
THE NW GULF WITH AN ASSOCIATED STRONG COLD FRONT ENTERING THE 
GULF OVER SE LOUISIANA NEAR 30N90W SW TO 26N96W THEN S INTO 
MEXICO NEAR TAMPICO CONTINUING NW AS A STATIONARY BOUNDARY ALONG 
THE SIERRA MADRE MOUNTAINS. A STRONG JET STREAM IS OVER THE SE 
US FROM E TEXAS ACROSS THE MISSISSIPPI VALLEY THEN NE OVER 
KENTUCKY AND WEST VIRGINIA. DENSE CLOUDS WITH SCATTERED SHOWERS 
ARE OVER THE GULF WATERS W OF THE FRONT WHILE THE HEAVIER 
ACTIVITY IS WELL INLAND OVER THE E US. THE SURFACE RIDGE 
ANCHORED IN THE W ATLC IS RETREATING EASTWARD AHEAD OF THE COLD 
FRONT WHILE A SECOND SURFACE RIDGE IS BUILDING OVER TEXAS 
ANCHORED BY A 1026 MB HIGH NEAR DALLAS. STRONG NORTHERLY WINDS 
ARE W OF THE FRONT WITH MODERATE SOUTHERLY WINDS COVER THE 
REMAINDER OF THE AREA E OF THE FRONT. THE SOUTHERLY FLOW AHEAD 
OF THE FRONT IS GENERATING PATCHES OF LOW CLOUDS WITH ISOLATED 
SHOWERS WITHIN 120 NM E OF THE FRONT WHILE THE REMAINDER OF THE 
GULF IS STILL ENJOYING CLEAR SKIES AND MILD TEMPERATURES. THE 
FRONT IS EXPECTED TO CONTINUE SE ACROSS THE GULF EXITING THE 
REGION FRI AFTERNOON/EVENING. 

CARIBBEAN SEA...
AN UPPER LOW IS OVER THE WINDWARD PASSAGE/HAITI EXTENDING AN 
UPPER TROUGH W TO NEAR THE CAYMAN ISLANDS. HOWEVER...STRONG 
SUBSIDENCE AND DRY STABLE AIR ALOFT IS LIMITING ANY DEEP 
SHOWERS/CONVECTION. A TIGHT SURFACE PRESSURE GRADIENT BETWEEN 
THE SURFACE RIDGE OVER THE ATLC AND LOWER PRESSURE OVER THE 
TROPICS CONTINUES TO PRODUCE MODERATE/STRONG EASTERLY TRADE 
WINDS ACROSS THE CARIBBEAN BUT ARE EXPECTED TO DIMINISH ON FRI 
AS THE COLD FRONT IN THE GULF OF MEXICO MOVES INTO THE CARIBBEAN 
LATE FRI PUSHING THROUGH THE CARIBBEAN TO BE FROM PUERTO RICO TO 
PANAMA LATE SUN. THESE TRADE WINDS ARE ALSO USHERING IN LOW 
LEVEL CLOUDS WITH ISOLATED FAST MOVING SHOWERS ACROSS THE ENTIRE 
CARIBBEAN AND BANKING LOW CLOUDS WITH SCATTERED SHOWERS ALONG 
THE MOUNTAINS OF W PANAMA AND COSTA RICA. 
 
ATLANTIC OCEAN...
TRANQUIL CONDITIONS WITH FAIR WEATHER CLOUDS COVER ALL BUT THE 
FAR W ATLC WHERE PATCHES OF LOW CLOUDS WITH ISOLATED SHOWERS 
HAVE MOVED OFF THE US E COAST N OF 28N E OF 78W DUE TO THE 
APPROACHING FRONT IN THE GULF OF MEXICO. AN UPPER LOW IS OVER 
THE WINDWARD PASSAGE/HAITI COVERS THE AREA TO OVER THE TURKS AND 
CAICOS WITH NEAR ZONAL WESTERLY FLOW ALOFT COVERING THE 
REMAINDER OF THE ATLC. THE ENTIRE ATLC BASIN HAS MODERATE TO 
STRONG SUBSIDENCE AND DRY AIR ALOFT LIMITING ANY DEEP SHOWERS/ 
CONVECTION. A SURFACE RIDGE DOMINATES THE ATLC ANCHORED BY A 
1029 MB HIGH NEAR 32N58W PRODUCING A TIGHT PRESSURE GRADIENT 
BETWEEN THIS RIDGE OVER THE ATLC AND LOWER PRESSURE OVER THE 
TROPICS RESULTING IN MODERATE/STRONG EASTERLY TRADE WINDS ACROSS 
THE TROPICS. 

$$
WALLACE