[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201148
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN NOV 20 2011

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURES...

AN UPPER LEVEL LOW IS CENTERED NEAR 23N54W WITH AN UPPER LEVEL
TROUGH AXIS ORIENTED N-NW TO S-SE ALONG 31N57W TO 13N52W. THIS
UPPER LEVEL FEATURE SUPPORTS AN ELONGATED AREA OF SURFACE
TROUGHING ACROSS THE CENTRAL ATLC WITH A SURFACE TROUGH ANALYZED
FROM 13N52W ALONG 18N53W THROUGH A 1010 MB LOW NEAR 22N54W
CONTINUING ALONG 28N52W TO 33N48W WITH WEAKER SURFACE TROUGH
ANALYZED FROM 19N58W TO 22N63W. THE DOMINANT EASTERLY SURFACE
TROUGH REMAINS THE FOCUS FOR POTENTIAL TROPICAL OR SUB-TROPICAL
CYCLONE FORMATION WITH A MEDIUM CHANCE DURING THE NEXT 48 HOURS.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 45 NM OF
LINE FROM 21N52W TO 25N53W. THE ACTIVITY FURTHER E IS ASSOCIATED
MORE WITH THE UPPER RIDGE TO THE E RATHER THAN THE LOW/TROUGH
ITSELF.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA ENTERING THE E TROPICAL
ATLC NEAR 12N15W TO 9N18W. THE ITCZ AXIS EXTENDS FROM 9N18W
ALONG 7N29W 4N37W TO SOUTH AMERICA NEAR 4N51W. SCATTERED
MODERATE/STRONG CONVECTION IS FROM 3N-9N BETWEEN 16W-24W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 2N-8N
BETWEEN 24W-35W. CLUSTERS OF SCATTERED MODERATE/STRONG
CONVECTION ARE FROM 4N-9N BETWEEN 11W-16W. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 2N-10N BETWEEN
25W-30W AND FROM 6N-10N BETWEEN 30W-35W.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER RIDGE DOMINATES THE GULF ANCHORED IN THE E PACIFIC
REGION WITH THE UPPER RIDGE AXIS EXTENDING ACROSS S MEXICO NEAR
VERACRUZ TO OVER NE FLORIDA WITH DRY STABLE AIR ALOFT COVERING
THE ENTIRE GULF. A SURFACE RIDGE DOMINATES THE GULF ANCHORED IN
THE W ATLC EXTENDING AN AXIS ACROSS THE SE CONUS ALONG 30N86W TO
NEAR TUXPAN MEXICO. RETURN FLOW IS NOW ESTABLISHED OVER THE NW
GULF. OVERCAST LOW CLOUDS WITH SCATTERED SHOWERS ARE IN THE NE
GULF WITHIN 60/75 NM OF LINE FROM 27N87W TO INLAND OVER THE
FLORIDA PANHANDLE NEAR PANAMA CITY. ISOLATED SHOWERS ARE
OBSERVED ON MIAMI AND KEY WEST RADAR OVER THE STRAITS OF FLORIDA
FROM 24N TO THE FLORIDA KEYS LEAVING THE REMAINDER OF THE GULF
UNDER CLEAR SKIES THIS MORNING. SURFACE RIDGE WILL PERSIST
THROUGH MON WITH RETURN FLOW OVER THE NW GULF. A COLD FRONT WILL
MOVE OFF THE TEXAS COAST LATE TUE AND EXTEND FROM THE FLORIDA
BIG BEND AREA TO VERACRUZ MEXICO BY WED EVENING THEN WILL STALL
AND BECOME DIFFUSE ON THU.

CARIBBEAN SEA...
THE UPPER RIDGE OVER THE GULF OF MEXICO COVERS THE NW CARIBBEAN
N OF 15N W OF 78W. A WEAK INVERTED UPPER TROUGH EXTENDS FROM S
OF JAMAICA NEAR 17N77W TO NE NICARAGUA NEAR 13N84W GENERATING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS INLAND AND WITHIN 75 NM
ALONG THE COAST OF NICARAGUA FROM 14N TO THE COSTA RICA BORDER.
WEAK NE FLOW ALOFT COVERS THE REMAINDER OF THE CARIBBEAN E OF
77W. DRY STABLE AIR ALOFT DOMINATES THE E CARIBBEAN E OF 75W
WITH MOIST TROPICAL AIR OVER THE W CARIBBEAN. SCATTERED SHOWERS
AND POSSIBLE ISOLATED THUNDERSTORMS DOT THE W CARIBBEAN SW OF
LINE FROM THE YUCATAN PENINSULA NEAR 21N87W ALONG 17N80W TO
COLOMBIA NEAR 12N72W BEING USHERED IN ON THE STRONG EASTERLY
TRADE WINDS. THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR
11N75W ALONG 11N79W ACROSS COSTA RICA INTO THE E PACIFIC REGION
NEAR 10N84W. ISOLATED LOW LEVEL FAST MOVING SHOWERS ARE POSSIBLE
ACROSS THE SE CARIBBEAN S OF 15N E OF 73W ALSO USHERED IN ON THE
EASTERLY TRADE WINDS. FRESH TO STRONG NE TO E WINDS WILL PERSIST
OVER THE N CARIBBEAN AND N LEEWARD ISLANDS THROUGH MIDWEEK.

ATLANTIC OCEAN...
A SURFACE RIDGE DOMINATES THE W ATLC EXTENDING INTO THE GULF OF
MEXICO ANCHORED BY A 1034 MB HIGH ABOUT 850 NM NE BERMUDA.
ISOLATED SHOWERS ARE WITHIN 75 NM OF LINE FROM 26N70W TO OVER S
FLORIDA AND INTO THE STRAITS OF FLORIDA NEAR MIAMI. THE
ELONGATED UPPER LEVEL TROUGH/SURFACE FEATURES IN THE SPECIAL
FEATURES SECTION IS TO THE E OF THE SURFACE RIDGE...SEE ABOVE. A
HIGHLY AMPLIFIED UPPER RIDGE IS TO THE E OF THE SPECIAL FEATURES
EXTENDING FROM NEAR 12N41W ALONG 23N42W TO BEYOND 32N39W
PROVIDING DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS WITHIN 120 NM OF LINE FROM
13N48W TO 25N48W AND WITHIN 150/175 NM OF LINE FROM 25N51W TO
BEYOND 32N46W. AN UPPER TROUGH CONTINUES TO DIG S OVER THE E
ATLC TO 15N E OF 27W SUPPORTING A COLD FRONT NE OF THE
DISCUSSION AREA. THE REMAINDER OF THE E ATLC IS DOMINATED BY A
SURFACE RIDGE AXIS THAT EXTENDS THROUGH 32N33W TO 20N27W. STRONG
PRESSURE GRADIENT BETWEEN SURFACE RIDGE OVER THE ATLC AND THE
PERSISTENT ELONGATED SURFACE TROUGH IN THE SPECIAL FEATURES WILL
PRODUCE FRESH TO STRONG NE WINDS ACROSS MOST OF THE AREA THROUGH
TONIGHT BEFORE THE SURFACE LOW LIFTS NE MON AND TUE. SOUTHERLY
FLOW OFF THE N FLORIDA COAST WILL INCREASE WED AHEAD OF A COLD
FRONT EXPECTED TO MOVE INTO THE AREA FROM THE N WED NIGHT. THE
FRONT WILL MOVE SE THU AND REACH FROM W OF BERMUDA TO THE COAST
OF CENTRAL CUBA BY THU AFTERNOON.

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

$$
PAW






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