000
AXNT20 KNHC 170556
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST SAT NOV 17 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0515 UTC.

...ITCZ/MONSOON TROUGH...

MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL ATLC 
NEAR 11N15W TO 9N16W WHERE THE ITCZ AXIS CONTINUES ALONG 5N24W 
10N47W TO SOUTH AMERICA NEAR 7N62W. A SURFACE TROUGH IS ANALYZED 
ALONG THE E SIDE OF AN UPPER TROUGH FROM 19N34W TO 12N40W WITH  
SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS WITHIN 250 
NM E OF THE TROUGH AXIS. A SECOND SURFACE TROUGH IS ANALYZED AT 
THE BASE OF THE SAME UPPER TROUGH ALONG 46W/47W FROM 11N-16N 
WITH SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS FROM 
14N-16N BETWEEN 39W-47W. SCATTERED MODERATE/ISOLATED STRONG 
CONVECTION IS WITHIN 60 NM OF 8.5N BETWEEN 41W-45W. CLUSTERS OF 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 150 NM 
ALONG THE COAST OF SW AFRICA S OF 10N W OF 10W AND WITHIN 45 NM 
OF THE ITCZ BETWEEN 19W-22W. 

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER TROUGH EXTENDS FROM THE CANADIAN MARITIMES OVER THE 
E CONUS INTO THE E GULF OF MEXICO CONTINUING S INTO THE NW 
CARIBBEAN. A BROAD UPPER RIDGE ANCHORED OVER THE E PACIFIC 
REGION COVERS THE W GULF. THIS IS GIVING THE GULF MOSTLY NW FLOW 
ALOFT. A SURFACE RIDGE DOMINATES THE GULF ANCHORED BY A 1035 MB 
HIGH OVER THE GREAT LAKES AREA. THE UPPER RIDGE IS DRAWING MOIST 
TROPICAL AIR ACROSS MEXICO INTO THE W GULF AND COUPLED WITH A 
SURFACE TROUGH THAT IS ANALYZED ALONG THE COAST OF MEXICO FROM 
24N97W TO 19N95W ARE GENERATING SCATTERED SHOWERS AND POSSIBLE 
ISOLATED THUNDERSTORMS S OF 25N W OF 92W. THE DEEP MOISTURE THAT 
WAS OVER THE E GULF AND THE FLORIDA PENINSULA IS BEGINNING TO 
RETREAT EASTWARD. HOWEVER...SCATTERED SHOWERS AND POSSIBLE 
ISOLATED THUNDERSTORMS REMAIN OVER THE SE GULF S OF 26N E OF 
87W. DRY CONTINENTAL AIR IS STREAMING INTO THE N GULF MAINLY N 
OF 24N BETWEEN 85W-92W GIVING THE REMAINDER OF THE GULF FAIR 
WEATHER TONIGHT. SURFACE RIDGE WILL SLOWLY MOVE E AND WEAKEN MON 
THROUGH WED. 

CARIBBEAN SEA...
A WEAK PRESSURE PATTERN DOMINATES THE CARIBBEAN TONIGHT. THE 
BROAD UPPER TROUGH OVER THE GULF OF MEXICO EXTENDS OVER THE NW 
CARIBBEAN W OF 77W WHILE AN UPPER RIDGE DOMINATES THE REMAINDER 
OF THE CARIBBEAN FROM AN UPPER HIGH OVER VENEZUELA WITH THE AXIS 
EXTENDING ALONG 63W CONTINUING OVER THE W/CENTRAL ATLC. 
DIFFLUENCE ALOFT ON THE W SIDE OF THE UPPER RIDGE IS GENERATING 
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ACROSS THE 
CENTRAL CARIBBEAN BETWEEN 70W-82W. THIS IS LEAVING THE NW AND 
FAR E CARIBBEAN WITH FAIR WEATHER TONIGHT. THE WEAK PRESSURE 
PATTERN WILL MAINTAIN MODERATE TRADE WINDS ACROSS THE AREA 
THROUGH TUE INCREASING IN THE NW CARIBBEAN ON WED. LOW PRESSURE 
IS EXPECTED TO FORM IN THE FAR SW CARIBBEAN. 

ATLANTIC OCEAN...
THE BROAD UPPER TROUGH IN THE GULF OF MEXICO COVERS THE FAR W 
ATLC W OF 73W SUPPORTING A COLD FRONT THAT EXTENDS THROUGH 
32N72W TO 31N75W WHERE IT PULLS UP STATIONARY TO THE COAST OF 
FLORIDA NEAR WEST PALM BEACH. SCATTERED SHOWERS/ISOLATED 
THUNDERSTORMS ARE N OF THE FRONT TO 31N W OF 78W TO THE COAST OF 
FLORIDA. THE BROAD UPPER RIDGE OVER THE CARIBBEAN EXTENDS OVER 
THE W/CENTRAL ATLC ACROSS THE VIRGIN ISLANDS NEAR 18N63W TO 
BEYOND 32N57W. A SURFACE TROUGH IS BENEATH THE UPPER RIDGE 
EXTENDING FROM 32N61W TO 21N67W. THE SURFACE TROUGH COUPLED WITH 
THE UPPER RIDGE PROVIDING DIFFLUENCE ALOFT ARE GENERATING 
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 
250/300 NM OF LINE FROM THE GREATER ANTILLES NEAR 20N72W ALONG 
26N66W TO 28N59W. AN UPPER TROUGH EXTENDS FROM AN UPPER LOW OVER 
PORTUGAL ALONG 32N17W CONTINUING TO A SECOND WEAKER UPPER LOW 
NEAR 25N36W THEN SW INTO THE TROPICS NEAR 10N46W AND SUPPORTING 
A COLD FRONT THAT ENTERS THE REGION NEAR 32N11N ACROSS THE 
CANARY ISLANDS TO 27N19W. THIS UPPER TROUGH IS ALSO ENHANCING 
THE ACTIVITY ASSOCIATED WITH THE SURFACE TROUGHS IN THE 
ITCZ/MONSOON TROUGH SECTION ABOVE. A LARGE SURFACE RIDGE 
DOMINATES THE ATLC W OF 60W ANCHORED BY A 1030 MB HIGH ABOUT 300 
NM W OF THE AZORES. THE W ATLC STATIONARY FRONT WILL LINGER 
UNTIL MON WHILE A REINFORCING HIGH PRESSURE BUILDS OVER THE SE 
CONUS. A BROAD AREA OF LOW PRESSURE IS FORECAST TO DEVELOP SUN 
AND MON N OF 25N ALONG 65W AND WILL MOVE N OF THE AREA LATE MON 
INTO TUE BUT A SURFACE TROUGH WILL EXTEND S OF THE LOW AND 
LINGER OVER CENTRAL ATLC INTO WED.

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

$$
PAW