000
AXNT20 KNHC 111739
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN NOV 11 2012

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1645 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE COAST OF GUINEA-BISSAU AT 
12N16W TO 7N19W 6N24W. THE ITCZ BEGINS AT 6N24W AND CONTINUES 
ALONG 11N44W 7N59W. SCATTERED MODERATE/ISOLATED STRONG 
CONVECTION IS FROM 3N-7N BETWEEN 13W-25W. SIMILAR ACTIVITY IS 
FROM 9N-14N BETWEEN 16W-23W...AND FROM 7N-10N BETWEEN 41W-53W. 
 
...DISCUSSION...

THE GULF OF MEXICO...
MOSTLY FAIR WEATHER CONTINUES TO COVER THE GULF OF MEXICO WITH 
ONLY A FEW ISOLATED SHOWERS MOVING INTO EASTERN TEXAS AND 
LOUISIANA. THE FAIR WEATHER IS ATTRIBUTED TO SURFACE RIDGING 
EXTENDING FROM THE NW ATLC AND DRY AIR ALOFT AROUND AN UPPER 
LEVEL RIDGE COVERING THE BASIN WITH AXIS FROM THE SW GULF TO THE 
EASTERN SEABOARD. SOME MOISTURE ALOFT IS EMERGING OVER THE 
WESTERN GULF AROUND THE EAST SIDE OF AN APPROACHING UPPER 
TROUGH. THIS UPPER TROUGH SUPPORTS A COLD FRONT THAT IS EXPECTED 
TO REACH THE BASIN EARLY TOMORROW MORNING. WINDS HAVE ALREADY 
INCREASED ACROSS THE NW GULF REACHING UP TO 30 KT. EAST TO 
SOUTHEAST WINDS OF 15-20 KT SPREAD ACROSS THE REST OF THE BASIN.

THE CARIBBEAN SEA...
DRY AIR ALOFT COVERS A GOOD PORTION OF THE CARIBBEAN TODAY 
WRAPPING AROUND AN UPPER LEVEL RIDGE IN THE GULF OF MEXICO AND 
THEN AROUND AN UPPER LEVEL TROUGH COVERING THE WEST ATLC AND 
CENTRAL CARIBBEAN. THIS PATTERN IS HELPING PROVIDE MOSTLY FAIR 
CONDITIONS ACROSS THE BASIN. SCATTERED SHOWERS ARE NOTED OFF THE 
COAST OF COSTA RICA AND PANAMA ASSOCIATED WITH THE MONSOON 
TROUGH THAT EXTENDS THROUGH BOTH COUNTRIES AND THEN DIPS SOUTH 
OF PANAMA INTO COLOMBIA. A FEW ISOLATED SHOWERS ARE EMBEDDED 
WITHIN STRONG NE FLOW OF 20-25 KT...WHICH IS PRESENT ACROSS MUCH 
OF THE CENTRAL AND WESTERN CARIBBEAN. SLIGHTLY LIGHTER WINDS OF 
15 KT ARE ACROSS THE FAR EASTERN CARIBBEAN. A FEW ISOLATED 
SHOWERS ARE BEGINNING TO REACH THE LEEWARD ISLANDS ASSOCIATED 
WITH A SURFACE TROUGH JUST EAST OF THE  ISLANDS. THE SURFACE 
TROUGH IS EXPECTED TO MOVE WESTWARD AND WILL LIKELY CAUSE 
SHOWERS/POSSIBLE THUNDERSTORMS ACROSS THE NE CARIBBEAN. LITTLE 
CHANGE IS EXPECTED ELSEWHERE. 

THE ATLANTIC OCEAN...
SURFACE RIDGING ACROSS THE EASTERN CONUS CONTINUES INTO THE WEST 
ATLC MAINTAINING MOSTLY FAIR CONDITIONS ACROSS THE AREA. DRY AIR 
ALOFT IS ALSO SPREADING INTO THE AREA AS IT WRAPS AROUND AN 
UPPER LEVEL RIDGE OVER THE EASTERN SEABOARD AND AROUND AN UPPER 
LEVEL TROUGH OVER THE AREA ALONG 70W. THE UPPER TROUGH CONTINUES 
TO SUPPORT A FRONTAL BOUNDARY IN THE CENTRAL ATLC. IT HAS BECOME 
STATIONARY AND EXTENDS ALONG 32N50W 25N60W 20N70W. SCATTERED 
SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 150 NM EITHER SIDE OF 
THE AXIS. A SURFACE TROUGH IS EAST OF THE LEEWARD ISLANDS ALONG 
19N60W TO 13N58W SUPPORTING A FEW ISOLATED SHOWERS WITHIN 120 NM 
EITHER SIDE OF THE AXIS. AN UPPER LEVEL RIDGE COVERS THE CENTRAL 
ATLC ALONG 50W EXTENDING INTO A LARGER UPPER RIDGE OVER THE NE 
ATLC SUPPORTING A BROAD SURFACE RIDGE ANCHORED BY A 1033 MB 
AZORES HIGH. THE RIDGE IS PROVIDING GENERALLY FAIR CONDITIONS 
ACROSS THE EASTERN ATLC EXCEPT FOR AN AREA OF DISTURBED 
WEATHER IN THE EASTERN TROPICAL ATLC. AN UPPER LEVEL LOW SOUTH 
OF THE LARGE UPPER RIDGE NEAR 24N38W IS SUPPORTING SCATTERED 
SHOWERS/ISOLATED THUNDERSTORMS FROM 18N-28N BETWEEN 31W-37W. A 
WEAK SURFACE TROUGH IS WEST OF THIS AREA ALONG 19N43W TO 
15N45W...BUT IS NOT CAUSING ANY ACTIVE WEATHER. MODEL GUIDANCE 
INDICATES A SECOND SURFACE TROUGH WILL FORM NEAR THE AREA OF 
ACTIVITY ASSOCIATED WITH THE UPPER LOW. THE STATIONARY FRONT IN 
THE CENTRAL ATLC IS ALSO EXPECTED TO BREAK OFF FROM THE MAIN 
FRONT AND MOVE WESTWARD AS A SURFACE TROUGH. 

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

$$
WALTON