AXNT20 KNHC 201143
TWDAT 

TROPICAL WEATHER DISCUSSION   
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST THU NOV 20 2008

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1115 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 51W S OF 15N MOVING W NEAR 15 KT. THIS 
WAVE HAS BEEN RELOCATED TO THE E OF ITS 20/0000 UTC ANALYSIS 
POSITION ALONG 54W S OF 15N. RECENT SATELLITE IMAGERY INDICATES 
THAT THIS WAVE COINCIDES WITH A MAXIMUM IN LOW LEVEL CYCLONIC 
CIRCULATION...WHICH IS CONFIRMED BY CIMSS WAVETRAK PRODUCT. THIS 
LOW LEVEL CIRCULATION HAS RECENTLY BEEN REVEALED AFTER HAVING 
DEPARTED A REGION OF MID/HIGH-LEVEL CLOUDINESS. A WELL-DEFINED 
INVERTED-V PATTERN IN CLOUD COVERAGE IS IN THE VICINITY OF THIS 
WAVE. ADDITIONALLY...A MAXIMUM IN DEEP LAYER MOISTURE COINCIDES 
WITH THIS WAVE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM 
CIMSS. SCATTERED MODERATE CONVECTION IS FROM 9N-14N BETWEEN 
46W-52W.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 9N12W 7N22W 7N36W 9N44W 8N61W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM 
EITHER SIDE OF THE ITCZ AXIS BETWEEN 13W-19W. SCATTERED MODERATE 
CONVECTION IS WITHIN 90 NM S OF THE ITCZ AXIS BETWEEN 25W-31W. 
SCATTERED MODERATE CONVECTION IS ALSO FROM 9N-14N BETWEEN 
57W-61W...WHICH IS BEING ENHANCED BY UPPER LEVEL DIVERGENCE.

...DISCUSSION...

GULF OF MEXICO...
STRONG WESTERLY FLOW ALOFT AND DEEP LAYER DRY AIR ARE PRESENT 
OVER MUCH OF THE GULF REGION. HOWEVER...UPPER LEVEL MOISTURE IS 
STREAMING FROM THE E PACIFIC REGION TO THE W GULF. ALSO...A 
MODIFIED CONTINENTAL POLAR AIRMASS PERSISTS ACROSS THE GULF 
REGION. AS A RESULT...TEMPERATURES ACROSS THE GULF REGION ARE 
BELOW SEASONAL AVERAGES. THIS RELATIVELY COOLER AND DRIER 
AIRMASS IS BEING SUPPORTED BY A 1024 MB SURFACE HIGH OVER THE 
N GULF NEAR 29N88W. AS THE COOLER AIR IS BEING ADVECTED OVER THE 
RELATIVELY WARMER GULF WATERS...WEAK LOW LEVEL INSTABILITY IS 
SUPPORTING SCATTERED STRATOCUMULUS CLOUDS ACROSS THE GULF MAINLY 
S OF 26N. HOWEVER...SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS 
HIGHER IN THE ATMOSPHERE ARE INHIBITING DEEP CONVECTION ACROSS 
THE GULF REGION. OVER THE NEXT DAY...ANOTHER SURFACE COLD 
FRONT...CURRENTLY EXTENDING FROM THE GREAT LAKES TO THE PLAINS 
OF THE CONUS...WILL MOVE SOUTHWARD AND APPROACH THE N GULF 
COAST. THIS COLD FRONT WILL REINFORCE THE MODIFIED CONTINENTAL 
POLAR AIRMASS ALREADY IN PLACE ACROSS THE GULF REGION. 
ADDITIONALLY...STRONG N TO NE SURFACE WINDS ARE BLOWING THROUGH 
THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE 
E PACIFIC REGION.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A NEW 1009 MB SURFACE LOW IS LOCATED N OF 
PANAMA NEAR 10N80W BASED ON INCREASED CYCLONIC CIRCULATION 
EVIDENT IN RECENT SATELLITE IMAGERY WHERE SURFACE PRESSURE FALLS 
HAVE BEEN NOTED. ADDITIONALLY...A SURFACE COLD FRONT EXTENDS 
FROM THE SURFACE LOW TO 16N79W TO HAITI NEAR 19N72W. LOW LEVEL 
CONVERGENCE NEAR THE SURFACE LOW AND COLD FRONT IS INTERACTING 
WITH DEEP MOISTURE OVER THE SW CARIBBEAN TO GENERATE SCATTERED 
SHOWERS AND THUNDERSTORMS OVER THE SW CARIBBEAN S OF 14N W OF 
77W. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIVERGENCE 
IN THE VICINITY OF AN UPPER RIDGE PRESENT OVER THE 
W CARIBBEAN...WITH THE AXIS OF THIS UPPER RIDGE EXTENDING FROM 
N COLOMBIA NEAR 10N75W TO 14N82W TO BELIZE NEAR 16N89W. OVER THE 
E CARIBBEAN...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM NE 
VENEZUELA NEAR 10N64W TO 13N61W TO THE SW ATLC...WITH UPPER 
LEVEL DIVERGENCE SUPPORTING SCATTERED SHOWERS OVER THE 
E CARIBBEAN S OF 15N E OF 70W.

ATLANTIC OCEAN...
A VIGOROUS UPPER TROUGH IS OVER THE W ATLC...WHICH IS SUPPORTING 
A SURFACE COLD FRONT THAT EXTENDS FROM HAITI NEAR 19N72W TO 
24N61W TO 32N54W AND EXTENDS TO THE N OF THE DISCUSSION AREA. 
ISOLATED SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THIS COLD 
FRONT. TO THE W OF THIS COLD FRONT...A MODIFIED CONTINENTAL 
POLAR AIRMASS IS IN PLACE...WITH TEMPERATURES BELOW SEASONAL 
AVERAGES ACROSS FLORIDA AND SCATTERED STRATOCUMULUS CLOUDS 
BETWEEN THIS FRONT AND THE COAST OF THE SE CONUS. FARTHER TO THE 
E...AN UPPER RIDGE AXIS EXTENDS FROM 13N61W TO 23N45W TO 32N47W 
TO N OF THE DISCUSSION AREA. UPPER LEVEL DIVERGENCE ASSOCIATED 
WITH THIS UPPER RIDGE IS ENHANCING SCATTERED SHOWERS AND 
THUNDERSTORMS FROM 9N-14N BETWEEN 57W-61W. TO THE E...A 1011 MB 
SURFACE LOW IS CENTERED NEAR 28N45W. DEEP LAYER DRY AIR IS 
INHIBITING DEEP CONVECTION NEAR THIS SURFACE LOW. ALSO...AN 
UPPER TROUGH IS PRESENT OVER THE E ATLC N OF 14N E OF 38W WITH 
AN UPPER LOW NEAR 29N34W. UPPER LEVEL DIVERGENCE AND ATMOSPHERIC 
INSTABILITY NEAR THE UPPER LOW AND UPPER TROUGH ARE SUPPORTING 
SCATTERED SHOWERS N OF 26N BETWEEN 28W-35W.

$$
COHEN