[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 301746
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 30 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

HURRICANE OPHELIA IS CENTERED NEAR 23.5N 62.8W AT 30/1500 UTC OR
ABOUT 505 NM S OF BERMUDA MOVING N AT 10 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 960 MB. MAXIMUM SUSTAINED WIND SPEED IS 100
KT WITH GUSTS TO 120 KT. NUMEROUS MODERATE AND ISOLATED STRONG
CONVECTION IS FROM 21N-28N BETWEEN 59W-65W. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS.

TROPICAL STORM PHILIPPE IS CENTERED NEAR 22.9N 45.3W AT 30/1500
UTC OR ABOUT 995 NM N-NE OF THE LEEWARD ISLANDS MOVING NW AT 11
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM
SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 50 KT. SCATTERED
MODERATE CONVECTION IS FROM 21N-26N BETWEEN 43W-47W. SEE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22
KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE PREVIOUSLY ANALYZED NEAR 35W HAS CONTINUED TO
DISSIPATE OVER THE PAST 24 HOURS AND IS NO LONGER DISCERNIBLE IN
LOW-LEVEL FLOW...SO THEREFORE IT HAS BEEN DROPPED FROM THE
SURFACE ANALYSIS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 18N16W
ALONG 13N21W 11N25W 08N28W TO 04N35W. THE INTERTROPICAL
CONVERGENCE ZONE AXIS EXTENDS FROM 04N35W TO 04N51W. WIDELY
SCATTERED MODERATE CONVECTION IS N OF 04N TO THE MONSOON TROUGH
AXIS BETWEEN 13W-34W. ISOLATED MODERATE CONVECTION IS ALSO
OCCURRING FROM 05N-13N BETWEEN 46W-51W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL WESTERLY FLOW DOMINATES ACROSS THE GULF BETWEEN
UPPER LEVEL TROUGHING ACROSS THE EASTERN CONUS AND A BROAD EAST
TO WEST UPPER LEVEL RIDGE AXIS ALONG 17N BETWEEN HISPANIOLA AND
WEST-CENTRAL MEXICO. WATER VAPOR IMAGERY SHOWS A PROGRESSIVE
SHORTWAVE TROUGH AXIS MOVING ACROSS MISSISSIPPI AND ALABAMA
WHICH IS THE DRIVING FORCE FOR A COLD FRONT EXTENDING FROM
VERMILION BAY LOUISIANA TO THE TEXAS COAST NEAR MATAGORDA BAY. A
PRE-FRONTAL TROUGH EXTENDS FROM 29N94W TO 27N97W. SCATTERED
SHOWERS AND TSTMS ARE OCCURRING WITHIN 60 NM SE OF THE FRONTAL
TROUGH AND EXTEND SOUTHWARD ACROSS PORTIONS OF THE WESTERN GULF
WATERS S OF 24N W OF 94W. FARTHER EAST...A WEAK REMNANT FRONTAL
BOUNDARY EXTENDS ACROSS THE NORTHERN FLORIDA PENINSULA INTO THE
NE GULF WATERS NEAR 29N84W. WHILE THE BOUNDARY REMAINS FREE OF
CONVECTION...A DRIER AIRMASS REMAINS TO THE NW ACROSS THE SE
CONUS. AS THE COLD FRONT CONTINUES TO MARCH ACROSS THE GULF
THROUGH TODAY AND OVER THE WEEKEND...A HIGH PRESSURE RIDGE IS
FORECAST TO BUILD IN OVER THE CENTRAL PLAINS AND MISSISSIPPI
RIVER VALLEY...REACHING SOUTHWARD OVER THE GULF...PROVIDING A
DRY AND RELATIVELY COMFORTABLE AIRMASS TO REMAIN IN PLACE
THROUGH EARLY WEDNESDAY OF NEXT WEEK. AS THE FRONT PASSES...
MAINLY NE WINDS WILL DOMINATE OVER THE NEXT SEVERAL DAYS.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE E PACIFIC REGION INTO
THE WESTERN CARIBBEAN ALONG 18N TO 69W. A MODERATELY DRY AIRMASS
ALOFT IS NOTED ON WATER VAPOR IMAGERY WITH THIS UPPER LEVEL
RIDGE AND THEREFORE CONDITIONS OVER CENTRAL AMERICA AND THE
WESTERN AND CENTRAL CARIBBEAN REMAIN FAIRLY FREE OF ANY
SIGNIFICANT DEEP CONVECTION THIS AFTERNOON. EASTERLY TRADES
EXTEND ACROSS THE CENTRAL CARIBBEAN AND MEET WITH GENERALLY
LIGHT NORTHEASTERLY FLOW ACROSS THE WESTERN CARIBBEAN. A FEW
ISOLATED SHOWERS AND TSTMS ARE ACROSS THE GULF OF HONDURAS...
HOWEVER MOST OF THE ACTIVE CONVECTION IS A FEW ISOLATED SHOWERS
AND TSTMS IN THE VICINITY OF THE WINDWARD PASSAGE REGION N OF
16N BETWEEN 72W-78W. ANOTHER AREA OF ISOLATED SHOWERS AND TSTMS
IS NORTH OF THE PANAMA COAST IN THE VICINITY OF THE MONSOON
TROUGH AXIS ALONG 10N. SCATTERED SHOWERS AND TSTMS ARE OCCURRING
S OF 12N BETWEEN 76W-82W. FARTHER EAST...S-SE WINDS ARE NOTED
OVER THE FAR EASTERN CARIBBEAN AND LESSER ANTILLES THIS
AFTERNOON WITH WEAK LOW-LEVEL CONVERGENCE AIDING IN ISOLATED
SHOWERS N OF 15N BETWEEN61W-67W.

ATLANTIC OCEAN...
UPPER LEVEL TROUGHING IS THE DOMINANT FEATURE ACROSS THE EASTERN
CONUS AND THIS TROUGHING SUPPORTS A FRONTAL BOUNDARY FROM 32N78W
TO THE NORTHERN FLORIDA PENINSULA NEAR 30N82W. A SURFACE TROUGH
EXTENDS SOUTHWARD FROM THE FRONT NEAR 30N80W ALONG 26N80W TO
WESTERN CUBA NEAR 23N81W. LOW-LEVEL CONVERGENCE EAST OF THE
SURFACE TROUGH AND SUFFICIENT UPPER LEVEL DIFFLUENCE ALOFT IS
GENERATING SCATTERED SHOWERS AND TSTMS NORTH OF THE BAHAMAS FROM
25N-32N BETWEEN 74W-78W. FARTHER EAST...THE REMAINDER OF THE SW
NORTH ATLC IS CONCERNED WITH HURRICANE OPHELIA AS A GENERAL
NORTHWARD MOVEMENT IS EXPECTED OVER THE NEXT 24 HOURS DUE TO THE
UPPER LEVEL TROUGHING LOCATED W OF 66W. TROPICAL STORM PHILIPPE
IS EXPECTED TO REMAIN OVER THE OPEN ATLC HIGH SEAS WATERS IN THE
COMING DAYS. TO THE NORTH OF PHILIPPE...A LONGWAVE UPPER LEVEL
TROUGH IS NOTED ON WATER VAPOR IMAGERY ACROSS THE EASTERN ATLC
WITH TROUGH AXIS ALONG 28W DIPPING INFLUENCE SOUTHWARD TO 27N
BETWEEN 22W-42W. THIS TROUGH IS PRIMARILY IN SUPPORT OF A COLD
FRONT ANALYZED FROM 32N25W TO 29N37W WHERE THE BOUNDARY
TRANSITIONS TO A SHEAR LINE EXTENDING WESTWARD TO 28N46W.
EARLIER MORNING ASCAT AND WINDSAT SCATTEROMETER PASSES INDICATED
A NARROW ZONE WITH AN ABRUPT CHANGE IN THE HORIZONTAL WIND
PARALLEL TO THE SHEAR LINE. STRONGER NE WINDS BY 10-15 KT WERE
CAPTURED WITHIN 180 NM NORTH OF THE SHEAR LINE AS OPPOSED TO
WEAKER E-NE WINDS BETWEEN THE SHEAR LINE AND TROPICAL STORM
PHILIPPE. ELSEWHERE...THE REMAINDER OF THE EASTERN ATLC IS UNDER
THE INFLUENCE OF A SURFACE RIDGE WITH AXIS FROM THE MADEIRA
ISLANDS NEAR 31N16W TO 20N40W. FINALLY...EXAMINING METEOSAT-9
VISIBLE SATELLITE IMAGERY AND THE CIMSS SAHARAN AIR LAYER
TRACKING PRODUCT...A LARGE AREA OF SAHARAN DUST COVERS THE
EASTERN ATLC FROM 08N-27N E OF 38W.

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

$$
HUFFMAN




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