[Tropical] Tropical Weather Discussion

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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





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