[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212346
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON NOV 21 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

A LARGE-SCALE UPPER LEVEL TROUGH IS LOCATED OVER THE CENTRAL
ATLC WITH AXIS EXTENDING FROM 30N57W SW OVER HISPANIOLA TO THE
WESTERN CARIBBEAN NEAR 15N83W. EMBEDDED WITHIN THIS TROUGHING...
WATER VAPOR IMAGERY INDICATES A SHORTWAVE WITH AXIS FROM 28N54W
TO 29N48W. THIS UPPER LEVEL FEATURE SUPPORTS A 1005 MB LOW
CENTERED NEAR 28N51W AND A SURFACE TROUGH ANALYZED FROM THE LOW
SW TO THE LEEWARD ISLANDS AND INTO THE EASTERN CARIBBEAN SEA.
THIS SURFACE LOW REMAINS THE FOCUS FOR POTENTIAL TROPICAL OR
SUB-TROPICAL CYCLONE GENESIS WITHIN THE NEXT 48 HOURS. WHILE
UPPER LEVEL DIFFLUENCE CONTINUES TO BE MAXIMIZED NORTH AND EAST
OF THE SHORTWAVE TROUGHING...SCATTERED MODERATE CONVECTION IS
OCCURRING FROM 27N-33N BETWEEN 47W-51W. AS THE LOW CONTINUES TO
CREATE A TIGHT PRESSURE GRADIENT AGAINST SURFACE RIDGING TO THE
NORTH OF THE DISCUSSION AREA...GALE FORCE WIND CONDITIONS ARE
EXPECTED THROUGH THE NEXT 24 TO 48 HOURS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 08N13W TO
07N15W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
07N15W TO 03N23W TO 07N44W TO 07N58W. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 02N-10N BETWEEN 14W-22W AND FROM 02N-06N
BETWEEN 22W-33W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL ANTICYCLONIC
CIRCULATION IS CENTERED NEAR 21N97W WITH A RIDGE AXIS EXTENDING
NE ACROSS THE NORTHERN FLORIDA PENINSULA AND INTO THE SW NORTH
ATLC WATERS. DRY AIR AND SUBSIDENT CONDITIONS PREVAIL ALOFT
ACROSS THE GULF WHICH IS SUPPORTIVE OF A SURFACE RIDGE ANCHORED
BY A 1025 MB HIGH CENTERED OVER SOUTHERN GEORGIA NEAR 31N84W.
FAIR WEATHER AND OVERALL STABLE CONDITIONS ARE NOTED ON
SATELLITE IMAGERY ACROSS THE BASIN WITH ONLY A SMALL AREA OF
ISOLATED SHOWERS OCCURRING FROM 26N-29N BETWEEN 88W-90W...AND
ACROSS THE FLORIDA PENINSULA S OF 28N INTO THE PORTIONS OF THE
FLORIDA STRAITS. ELSEWHERE...E TO SE WINDS ARE IN THE RANGE OF
10-20 KT THIS EVENING. THE RIDGE IS FORECAST TO BEGIN SLIDING
EASTWARD INTO THE SW NORTH ATLC WITH SOUTHERLY RETURN FLOW
INCREASING GRADUALLY ACROSS THE WESTERN GULF AS THE NEXT COLD
FRONT IS EXPECTED TO MOVE OFF THE TEXAS GULF COAST LATE TUESDAY
INTO EARLY WEDNESDAY.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH AXIS EXTENDS FROM THE CENTRAL ATLC SPECIAL
FEATURE MENTIONED ABOVE INTO THE CARIBBEAN NEAR 20N73W TO A BASE
NEAR 15N83W. MAINLY NORTH TO NORTHWESTERLY UPPER LEVEL FLOW IS
NOTED OVER THE NW CARIBBEAN WHILE WEST TO SOUTHWESTERLY FLOW IS
EAST OF THE TROUGH AXIS. WATER VAPOR IMAGERY INDICATES THAT
STRONG SUBSIDENCE AND DRY AIR IS ASSOCIATED WITH THE UPPER LEVEL
TROUGHING AND THAT CONDITIONS ACROSS THE CARIBBEAN THIS EVENING
ARE FAIRLY TRANQUIL UNDER NE TO E WINDS. THE MOST ACTIVE
CONVECTIVE AREA IS LOCATED IN THE SW CARIBBEAN WITH SCATTERED
SHOWERS AND TSTMS OCCURRING S OF 13N W OF 80W DUE TO LOW-LEVEL
CONVERGENCE AND CLOSE PROXIMITY OF THE MONSOON TROUGH AXIS
EXTENDING FROM THE E PACIFIC REGION ALONG 09N/10N TO NORTHERN
COLOMBIA. FARTHER EAST...THE UPPER LEVEL TROUGHING SUPPORTS A
SURFACE TROUGH EXTENDING INTO THE EASTERN CARIBBEAN NEAR 18N62W
TO 14N68W. ISOLATED SHOWERS ARE OCCURRING WITHIN 150 NM
NORTHWEST OF THE BOUNDARY. WIDELY SCATTERED SHOWERS ARE ALSO
OCCURRING OVER THE SE CARIBBEAN AND WINDWARD ISLANDS S OF 15N
BETWEEN 60W-65W.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE WESTERN GULF OF
MEXICO NORTHEASTWARD ACROSS THE NORTHERN FLORIDA PENINSULA INTO
THE SW NORTH ATLC WATERS TO BEYOND 32N78W. THIS UPPER LEVEL
RIDGE SUPPORTS A 1025 MB HIGH CENTERED OVER SOUTHERN GEORGIA AND
A 1024 MB HIGH CENTERED NEAR 32N71W. MOSTLY NE WINDS DOMINATE
ACROSS THE W ATLC DISCUSSION AREA WEST OF 60W WITH ISOLATED
SHOWERS POSSIBLE FROM 21N-30N W OF 62W. FARTHER EAST...AN UPPER
LEVEL TROUGH IS OVER THE CENTRAL ATLC WITH AXIS EXTENDING FROM
30N57W SW OVER HISPANIOLA INTO THE WESTERN CARIBBEAN SEA. THIS
TROUGH LARGELY SUPPORTS THE 1005 MB SPECIAL FEATURES LOW AND
AREA OF CONVECTION LOCATED MAINLY WITHIN THE NE QUADRANT OF THE
LOW FROM 27N-33N BETWEEN 47W-51W. THE REMAINDER OF THE EASTERN
ATLC IS UNDER THE INFLUENCE OF SURFACE RIDGING PROVIDING NE TO E
WINDS IN THE 15 TO 20 KT RANGE S OF 32N E OF 30W.

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

$$
HUFFMAN



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