[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 011758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT OCT 01 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 29.5N 62.9W AT 01/1500 UTC OR
ABOUT 150 NM SE OF BERMUDA MOVING N AT 18 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 952 MB. MAXIMUM SUSTAINED WIND SPEED IS 105
KT WITH GUSTS TO 130 KT. NUMEROUS MODERATE AND ISOLATED STRONG
CONVECTION IS FROM 28N-31N BETWEEN 60W-65W. SEE LATEST NHC
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/
WTNT31 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

TROPICAL STORM PHILIPPE IS CENTERED NEAR 24.8N 48.0W AT 01/1500
UTC OR ABOUT 995 NM N-NE OF THE LEEWARD ISLANDS MOVING NW AT 08
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM
SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED
MODERATE ISOLATED STRONG CONVECTION IS FROM 22N-28N BETWEEN
43W-48W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N17W
ALONG 10N20W TO 07N33W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 07N33W TO 07N45W. ISOLATED MODERATE CONVECTION IS
FROM 05N-09N BETWEEN 11W-15W...AND FROM 13N-17N BETWEEN 15W-19W.
SCATTERED MODERATE CONVECTION IS FROM 06N-13N BETWEEN 45W-56W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL WESTERLY FLOW DOMINATES ACROSS THE GULF BETWEEN AN
UPPER LEVEL LOW AND ASSOCIATED TROUGHING ACROSS THE EASTERN
CONUS AND A BROAD EAST TO WEST UPPER LEVEL RIDGE AXIS ALONG 15N
BETWEEN HISPANIOLA AND WEST-CENTRAL MEXICO. WATER VAPOR IMAGERY
SHOWS A VERY DRY AIRMASS MOVING ACROSS THE NORTHERN GULF N OF
27N WHICH IS THE DRIVING FORCE FOR A COLD FRONT EXTENDING FROM
NEAR LAKE OKEECHOBEE FLORIDA TO 25N90W TO THE TEXAS COAST NEAR
BROWNSVILLE. WHILE THE FRONT LACKS ANY SIGNIFICANT DEEP
CONVECTION DUE TO A LACK OF SUFFICIENT MOISTURE AND STRONGER
MIDDLE TO UPPER LEVEL LIFT...EXAMINING DEWPOINTS OVER THE
NORTHERN GULF AND NORTHERN PORTIONS OF FLORIDA VERSUS THE
SOUTHERN GULF AND THE EXTREME SOUTHERN FLORIDA PENINSULA...A
STARK CONTRAST IN AIRMASSES IS APPARENT. DEWPOINTS REMAIN IN THE
LOWER TO MID 70'S SOUTH OF THE FRONT...WHILE DEWPOINTS ARE IN
THE 50'S AND UPPER 40'S IN SOME LOCATIONS ALONG THE NORTHERN
GULF COAST. VISIBLE SATELLITE IMAGERY INDICATES A FEW ISOLATED
SHOWERS ARE OCCURRING WITHIN 30 NM EITHER SIDE OF THE FRONT.
FARTHER SOUTH...LOW-LEVEL CONVERGENCE OVER THE SW GULF IS
GENERATING ISOLATED SHOWERS AND TSTMS S OF 25N W OF A LINE FROM
THE COLD FRONT TO 19N92W. AS THE COLD FRONT CONTINUES TO MARCH
ACROSS THE GULF THROUGH THE WEEKEND...A HIGH PRESSURE RIDGE IS
FORECAST TO BUILD IN OVER THE MISSISSIPPI RIVER VALLEY...
REACHING SOUTHWARD OVER THE GULF...PROVIDING A DRY AND
RELATIVELY STABLE AIRMASS TO REMAIN IN PLACE THROUGH EARLY
WEDNESDAY OF NEXT WEEK. AS THE FRONT PASSES...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 15N TO 64W. A MODERATELY DRY AIRMASS
ALOFT IS NOTED ON WATER VAPOR IMAGERY WITH THIS UPPER LEVEL
RIDGE AND THEREFORE CONDITIONS OVER CENTRAL AMERICA AND MOST OF
THE 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. THIS GENERALLY CYCLONIC
LOW-LEVEL FLOW IS FOCUSED ALONG A SURFACE TROUGH ANALYZED FROM
20N85W TO 16N88W WITH SCATTERED SHOWERS AND TSTMS OCCURRING FROM
15N-20N BETWEEN 83W-89W. FARTHER EAST...UPPER LEVEL DIFFLUENCE
IS SUPPORTIVE OF A FEW ISOLATED SHOWERS AND TSTMS ACROSS THE
WINDWARD PASSAGE REGION N OF 16N BETWEEN 71W-77W. ANOTHER AREA
OF ISOLATED SHOWERS AND TSTMS IS LOCATED IN THE SW CARIBBEAN IN
THE VICINITY OF THE MONSOON TROUGH AXIS ALONG 09N/10N. ISOLATED
SHOWERS AND TSTMS ARE OCCURRING S OF 12N BETWEEN 75W-79W...AND S
OF 12N W OF 82W. FARTHER EAST...S-SE WINDS ARE NOTED OVER THE
EASTERN CARIBBEAN AND LESSER ANTILLES THIS AFTERNOON WITH WEAK
LOW-LEVEL CONVERGENCE AIDING IN ISOLATED SHOWERS N OF 16N
BETWEEN 64W-68W...INCLUDING PUERTO RICO AND THE US/UK VIRGIN
ISLANDS.

ATLANTIC OCEAN...
UPPER LEVEL TROUGHING IS THE DOMINANT FEATURE ACROSS THE EASTERN
CONUS AND THIS TROUGHING SUPPORTS A FRONTAL BOUNDARY FROM 32N75W
TO THE SOUTHERN FLORIDA PENINSULA NEAR 27N80W. A PRE-FRONTAL
SURFACE TROUGH EXTENDS EAST OF THE FRONT FROM 32N73W TO THE
CENTRAL BAHAMAS NEAR 25N78W. LOW-LEVEL CONVERGENCE EAST OF THE
SURFACE TROUGH AND SUFFICIENT UPPER LEVEL DIFFLUENCE ALOFT IS
GENERATING SCATTERED SHOWERS AND TSTMS IN A NARROW ZONE ACROSS
THE SW NORTH ATLC WATERS FROM 20N-32N BETWEEN 69W-73W. FARTHER
EAST...THE REMAINDER OF THE SW NORTH ATLC IS CONCERNED WITH
HURRICANE OPHELIA AS A NORTHWARD MOVEMENT IS EXPECTED OVER THE
NEXT 24 HOURS DUE TO THE APPROACHING UPPER LEVEL TROUGH LOCATED
W OF 65W. TROPICAL STORM PHILIPPE IS EXPECTED TO REMAIN OVER THE
OPEN ATLC HIGH SEAS WATERS IN THE COMING DAYS THAT REMAINS
EMBEDDED WITHIN A SURFACE RIDGE COVERING MUCH OF THE CENTRAL
ATLC N OF 15N BETWEEN 25W-55W. OVER THE EASTERN ATLC...AN UPPER
LEVEL LOW IS CENTERED EAST OF THE AZORES NEAR 37N24W WITH A
TROUGH AXIS EXTENDING SOUTHWARD TO A BASE NEAR 24N30W. THIS
TROUGHING SUPPORTS A WEAKENING COLD FRONT EXTENDING INTO THE
DISCUSSION AREA NEAR 32N17W TO 26N25W. ISOLATED SHOWERS ARE
OCCURRING WITHIN 30 NM EITHER SIDE OF THE FRONT. FINALLY...
EXAMINING METEOSAT-9 VISIBLE SATELLITE IMAGERY AND THE CIMSS
SAHARAN AIR LAYER TRACKING PRODUCT...A LARGE AREA OF SAHARAN
DUST COVERS THE EASTERN AND CENTRAL ATLC FROM 07N-22N BETWEEN
25W-45W.

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

$$
HUFFMAN




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