000
AXNT20 KNHC 312352
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
805 PM EDT SAT OCT 31 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.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 45W S OF 16N MOVING W 15-20 KT. WAVE IS 
EMBEDDED WITHIN A BROAD AREA OF DEEP LAYERED MOISTURE AS 
INDICATED BY TOTAL PRECIPITABLE WATER IMAGERY AND BENEATH 
DIFFLUENCE ALOFT WHICH IS GIVING THE AREA SCATTERED MODERATE 
CONVECTION FROM 14N-20N BETWEEN 43W-49W. 

TROPICAL WAVE IS ALONG 65W S OF 17N MOVING W 10-15 KT. WEAK WAVE 
WITH LITTLE SIGNATURE AND A WEAK MOISTURE MAXIMUM ON THE TOTAL 
PRECIPITABLE WATER IMAGERY. ISOLATED SHOWERS ARE S OF 15N TO THE 
COAST OF VENEZUELA BETWEEN 63W-68W. 

TROPICAL WAVE IS ALONG 85W S OF 17N MOVING W NEAR 15 KT. WAVE IS 
MOSTLY INLAND OVER CENTRAL AMERICA AND IN THE E PACIFIC REGION 
WITH LITTLE SIGNATURE OR ACTIVITY IN THE CARIBBEAN BASIN. 

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N12W 7N25W 9N41W 10N48W 
10N62W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 
90 NM EITHER SIDE OF THE ITCZ FROM 17W-22W AND S OF 11N INLAND 
OVER SOUTH AMERICA BETWEEN 53W-60W. CLUSTERS OF SCATTERED 
MODERATE CONVECTION ARE WITHIN 120/150 NM EITHER SIDE OF THE 
ITCZ FROM 22W-38W. 
 
...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...A COLD FRONT EXTENDS ACROSS THE FLORIDA 
PANHANDLE NEAR TALLAHASSEE INTO THE GULF ALONG 24N89W 20N93W 
THEN S THROUGH THE BAY OF CAMPECHE TO OVER S MEXICO NEAR 17N93W. 
A WELL DEFINED ROPE CLOUD WITH SHOWERS DEFINES THE LEADING EDGE 
OF THE FRONT OVER THE GULF. SCATTERED SHOWERS ARE WITHIN 75 NM W 
OF THE FRONT WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 
22N BETWEEN 90W-95W. STRONG NLY WINDS ARE W OF THE FRONT WITH 
GALE FORCE WINDS OVER THE SW GULF. THIS FRONT IS SUPPORTED ALOFT 
BY A SHARP UPPER LEVEL TROUGH MOVING ACROSS THE MISSISSIPPI 
VALLEY TO OVER THE SE U.S. AND PROVIDING MOIST SWLY DIVERGENT 
FLOW ALOFT BETWEEN THE TROUGH AND AN UPPER LEVEL RIDGE ANCHORED 
IN THE W ATLC COVERING THE E GULF E OF 87W. STRONG SUBSIDENCE 
AND DRY STABLE AIR HAS MOVED IN OVER THE NW GULF THUS CLEARING 
SKIES W OF A LINE FROM THE MISSISSIPPI COAST TO TAMPICO MEXICO 
WITH A SURFACE RIDGE BUILDING BEHIND THE FRONT ANCHORED OVER N 
MEXICO BY A 1025 MB HIGH. SIMILAR DRY AIR AND STRONG SUBSIDENCE 
IS OVER THE E GULF E OF THE FRONT WITH SOME SCATTERED SEABREEZE 
SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS ARE INLAND ALONG THE 
W COAST OF THE FLORIDA PENINSULA. THE FRONT IS EXPECTED TO STALL 
OVER THE SE GULF SUN NIGHT AS WINDS WILL DIMINISH TO BELOW GALE 
FORCE SUN AFTERNOON. 

CARIBBEAN SEA...
IN ADDITION TO THE TWO TROPICAL WAVES IN THE CARIBBEAN IS A 
SURFACE TROUGH THAT EXTENDS OVER THE SW CARIBBEAN FROM 11N78W TO 
THE NE TIP OF NICARAGUA NEAR 14N84W GENERATING SCATTERED 
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 175 NM N OF THE SURFACE 
TROUGH. UPPER LOW IS CENTERED OVER GUATEMALA NEAR 15N89W AND IS 
GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE 
YUCATAN PENINSULA AND INTO THE GULF OF MEXICO E OF THE FRONT IN 
THE BAY OF CAMPECHE. AN UPPER RIDGE EXTENDS FROM W PANAMA NW TO 
THE YUCATAN CHANNEL ENHANCING THE ACTIVITY ASSOCIATED WITH THE 
SURFACE TROUGH ABOVE AS WELL AS THE ACTIVITY OVER THE YUCATAN 
PENINSULA. THE BROAD UPPER RIDGE ANCHORED IN THE W ATLC IS 
FORCING STRONG SUBSIDENCE AND DRY STABLE AIR OVER THE N 
CARIBBEAN N OF A LINE FROM THE N LEEWARD ISLANDS ALONG 16N73W TO 
21N84W. HOWEVER...SOME ISOLATED SHOWERS AND POSSIBLE ISOLATED 
THUNDERSTORMS ARE OVER THE GREATER ANTILLES DUE TO THE REMNANTS 
OF A FRONTAL BOUNDARY THAT DISSIPATES ALONG THE N COAST OF 
HISPANIOLA. 

ATLANTIC OCEAN...
THE PRIME FOCUS IN THE ATLC WATERS TONIGHT IS THE 1000 MB LOW 
CENTERED NEAR 29N47W WITH A COLD FRONT THAT EXTENDS ALONG 27N47W 
20N54W TO 19N60W WHERE IT DISSIPATES TO ALONG THE N COAST OF 
HISPANIOLA NEAR 20N72W. THE UPPER SUPPORT FOR THIS SYSTEM IS A 
LARGE UPPER LOW/TROUGH CENTERED NEAR 27N52W. A LARGE UPPER RIDGE 
IS TO THE W ANCHORED OVER THE W ATLC NEAR 30N72W AND A SECOND 
UPPER RIDGE TO THE E ANCHORED OVER THE E ATLC NEAR 33N20W. THIS 
SCENARIO IS TAPPING INTO TROPICAL MOISTURE AND GENERATING A 
LARGE AREA OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 
120 NM W OF THE FRONT AND WITHIN 150 NM E OF THE FRONT E OF 
54W...FROM 26N-30N BETWEEN 50W-56W...AND N OF 30N FROM 34W-54W. 
STRONG SUBSIDENCE COVERS THE W ATLC BUT SCATTERED/BROKEN LOW 
LEVEL CLOUDS REMAIN PRESENT. HOWEVER...THE SAME SCENARIO OF DRY 
AIR AND STRONG SUBSIDENCE IS ALSO OVER THE E ATLC BUT WITH 
RATHER CLEAR SKIES TONIGHT. A SURFACE RIDGE OVER THE W ATLC IS 
ANCHORED BY A 1030 MB HIGH JUST SE OF THE CANADIAN MARITIMES 
WITH A SECOND SURFACE RIDGE OVER THE E ATLC ANCHORED BY A 1026 
MB HIGH N OF MADEIRA ISLANDS. 

$$
WALLACE