000
AXNT20 KNHC 211746
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
105 PM EST SUN NOV 21 2010

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 
1630 UTC.

...THE ITCZ...
 
ITCZ AXIS IS ANALYZED FROM SRN LIBERIA NEAR 6N8W 3N28W 6N44W 
8N49W 6N57W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS 
FROM 4N-7N BETWEEN 3W-11W...AND FROM 1N-4N BETWEEN 14W-18W. 
ISOLATED MODERATE/STRONG CONVECTION IS FROM EQ-8N BETWEEN 
18W-30W. AN EMBEDDED SURFACE TROUGH EXTENDS FROM 15N46W TO 4N49W 
ENHANCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 
8N-12N BETWEEN 45W-48W...AND FROM 7N-10N BETWEEN 50W-53W. 

...DISCUSSION...

GULF OF MEXICO...
A SHORTWAVE UPPER TROUGH EMBEDDED WITH MOSTLY DRY AIR EXTENDS 
FROM CENTRAL FLORIDA INTO THE CENTRAL GULF OF MEXICO NEAR 
24N90W. DUE TO THE DRY AIR, THE UPPER TROUGH IS NOT SUPPORTING 
ANY SIGNIFICANT WEATHER BESIDES A FEW SHOWERS NOTED OFF THE E 
CENTRAL COAST OF FLORIDA. ELSEWHERE...SURFACE RIDGING DOMINATES 
THE BASIN ANCHORED BY A 1029 MB HIGH OFF THE COAST OF SOUTH 
CAROLINA SUPPORTING BY AN UPPER LEVEL RIDGE COVERING THE ENTIRE 
ERN CONUS AND FAR W ATLC. ANTI-CYCLONIC SURFACE FLOW UP TO 20 
KTS IS AROUND THE RIDGE. EXPECT LITTLE CHANGE OVER THE NEXT 
COUPLE OF DAYS. 

CARIBBEAN SEA...
UPPER LEVEL RIDGING COVERS THE ENTIRE CARIBBEAN CENTERED W OF 
THE LESSER ANTILLES NEAR 14N65W. WATER VAPOR IMAGERY INDICATES A 
SWATH OF DRY AIR ACROSS THE NRN HALF OF THE BASIN MAINTAINING 
MOSTLY FAIR CONDITIONS. HOWEVER...A SHEAR LINE TO THE N OF 
HISPANIOLA AND ERN CUBA IS SUPPORTING CLOUDINESS AND ISOLATED 
SHOWERS ACROSS THE ISLANDS. A SURFACE TROUGH EXTENDS IN THE SW 
CARIBBEAN OFF THE COASTS OF NICARAGUA...COSTA RICA...AND PANAMA 
ALONG 15N83W 11N82W 10N78W ENHANCING SCATTERED 
SHOWERS/THUNDERSTORMS WITHIN 90 NM NE OF THE AXIS...AND 150 NM 
SW OF THE AXIS. SIMILAR ACTIVITY IS ALSO OFF THE NRN COAST OF 
COLOMBIA AND VENEZUELA WITHIN 150 NM DUE TO FRESH NE TRADE WINDS 
CONVERGING AGAINST LIGHTER WINDS ALONG THE COASTLINE. EXPECT 
SHOWER ACTIVITY TO CONTINUE ALONG THE SRN PORTION OF THE BASIN 
WHILE THE REMAINDER STAYS UNDER FAIR CONDITIONS.

ATLANTIC OCEAN...
A BROAD UPPER RIDGE COVERS THE W ATLC SUPPORTING A SURFACE RIDGE 
ANCHORED BY A 1029 MB HIGH OFF THE COAST OF S CAROLINA CENTERED 
NEAR 32N72W MAINTAINING FAIR WEATHER WITH SOME AREAS OF 
STRATOCUMULUS CLOUD COVER. FARTHER E...AN UPPER LEVEL TROUGH 
EXTENDING FROM NEWFOUNDLAND SE TO NEAR 18N46W SUPPORTS A COLD 
FRONT ENTERING THE DISCUSSION AREA NEAR 32N35W TO 22N56W WHERE 
IT TRANSITIONS INTO A SHEAR LINE ALONG 21N62W 19N68W 21N76W. 
ISOLATED SHOWERS ARE WITHIN 90 NM BEHIND THE FRONT...AND WITHIN 
60 NM EITHER SIDE OF THE SHEAR AXIS. A PRE-FRONTAL SURFACE 
TROUGH IS AHEAD OF THE FRONT ALONG 32N32W 23N44W. SCATTERED 
SHOWERS ARE WITHIN 120 NM AHEAD OF THE FRONT N OF 26N. UPPER 
LEVEL RIDGING EXTENDING FROM THE TROPICAL ATLC COVERS THE 
REMAINDER OF THE E ATLC MAINTAINING FAIR CONDITIONS.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON