AXNT20 KNHC 210527
TWDAT 

TROPICAL WEATHER DISCUSSION   
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST FRI NOV 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0445 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 51W/52W S OF 17N MOVING W NEAR 10 KT. 
SATELLITE IMAGERY INDICATES THAT THIS WAVE COINCIDES WITH A 
MAXIMUM IN LOW LEVEL CYCLONIC CIRCULATION...WHICH IS CONFIRMED 
BY CIMSS WAVETRAK PRODUCT. AN 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 13N-17N BETWEEN 46W-51W.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 12N15W 9N22W 6N32W 9N42W 3N51W. 
SCATTERED MODERATE CONVECTION IS FROM 5N-9N BETWEEN 13W-21W. 
SIMILAR CONVECTION IS WITHIN 60 NM N OF THE ITCZ AXIS BETWEEN 
43W-46W.

...DISCUSSION...

GULF OF MEXICO...
STRONG WESTERLY FLOW ALOFT IS PRESENT OVER MUCH OF THE GULF 
REGION...WITH UPPER LEVEL MOISTURE STREAMING FROM THE E PACIFIC 
REGION ACROSS THE GULF. AT THE SURFACE...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 1045 MB SURFACE HIGH OVER THE NORTHERN PLAINS OF 
THE CONUS...WITH AN ASSOCIATED SURFACE RIDGE EXTENDING INTO THE 
N GULF. AS 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 FRONT...CURRENTLY 
OVER THE SE CONUS...WILL MOVE SOUTHWARD ACROSS THE GULF REGION 
AS A COLD FRONT. THIS COLD FRONT WILL REINFORCE THE MODIFIED 
CONTINENTAL POLAR AIRMASS ALREADY IN PLACE ACROSS THE GULF 
REGION...WITH FREEZE WATCHES IN EFFECT FOR LATE FRIDAY NIGHT 
THROUGH SATURDAY MORNING FOR PORTIONS OF FLORIDA. 
ADDITIONALLY...STRONG N TO NE SURFACE WINDS ARE FORECAST TO BLOW 
THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS 
IN THE E PACIFIC REGION BEGINNING AT 21/1200 UTC.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A 1008 MB SURFACE LOW IS LOCATED N OF 
PANAMA NEAR 10N80W. ADDITIONALLY...A SURFACE STATIONARY FRONT 
EXTENDS FROM THE SURFACE LOW TO 14N79W TO 16N75W...WITH A 
SURFACE COLD FRONT EXTENDING FROM 16N75W TO E HISPANIOLA NEAR 
19N68W. LOW LEVEL CONVERGENCE NEAR THE SURFACE LOW AND SURFACE 
FRONTS IS INTERACTING WITH DEEP LAYER MOISTURE OVER THE 
S CARIBBEAN TO GENERATE SCATTERED SHOWERS AND THUNDERSTORMS OVER 
THE S CARIBBEAN S OF 14N W OF 73W. THIS ACTIVITY IS BEING 
ENHANCED BY UPPER LEVEL DIFFLUENCE IN THE VICINITY OF AN UPPER 
RIDGE PRESENT OVER THE W CARIBBEAN...WITH THE AXIS OF THIS UPPER 
RIDGE EXTENDING FROM N COLOMBIA NEAR 11N73W TO 16N81W TO THE 
NW CARIBBEAN NEAR 20N85W. OVER THE E CARIBBEAN...UPPER LEVEL 
DIVERGENCE IS INTERACTING WITH DEEP LAYER MOISTURE TO SUPPORT 
SCATTERED SHOWERS S OF 15N E OF 71W.

ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH OVER THE W ATLC IS SUPPORTING A SURFACE 
COLD FRONT THAT EXTENDS FROM E HISPANIOLA NEAR 19N68W TO 24N57W 
TO 32N50W TO N OF THE DISCUSSION AREA. ISOLATED SHOWERS ARE 
OCCURRING 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 78W. 
FARTHER TO THE E...A 1014 MB SURFACE LOW IS CENTERED NEAR 
28N44W...WITH SCATTERED SHOWERS WITHIN 90 NM OF THIS SURFACE 
LOW. ALSO...AN UPPER TROUGH IS PRESENT OVER THE E ATLC N OF 17N 
E OF 35W WITH AN ASSOCIATED SURFACE TROUGH EXTENDING FROM 21N33W 
TO 25N33W TO 27N35W. LOW LEVEL CONFLUENCE IN THE VICINITY OF 
THIS SURFACE TROUGH IS SUPPORTING SCATTERED SHOWERS WITHIN 60 NM 
EITHER SIDE OF THE SURFACE TROUGH. ALSO...A 1015 MB SURFACE LOW 
IS FORECAST TO FORM NEAR 23N29W OVER THE NEXT DAY. TO THE E...A 
SURFACE RIDGE IS N OF 17N BETWEEN THE AFRICAN COAST AND 
27W...RESULTING IN GENERALLY FAIR WEATHER CONDITIONS ACROSS THE 
E ATLC.

$$
COHEN