[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 291748
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU SEP 29 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...

TROPICAL STORM OPHELIA IS CENTERED NEAR 20.9N 61.8W AT 29/1500
UTC OR ABOUT 180 NM N-NE OF THE NORTHERN LEEWARD ISLANDS MOVING
N-NW AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 991 MB.
MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT.
SCATTERED MODERATE CONVECTION IS FROM 19N-24N BETWEEN 58W-63W.
ISOLATED MODERATE CONVECTION IS FROM 18N-20N BETWEEN 57W-60W.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

TROPICAL STORM PHILIPPE IS CENTERED NEAR 18.6N 42.6W AT 29/1500
UTC OR ABOUT 1075 NM W OF THE CAPE VERDE ISLANDS MOVING NW AT 11
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM
SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SCATTERED
MODERATE AND ISOLATED STRONG CONVECTION IS SHEARED TO THE NORTH
OF THE CENTER OF PHILIPPE OCCURRING FROM 19N-22N BETWEEN
40W-44W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 02N35W TO 09N32W MOVING W NEAR
10-15 KT. THIS RELATIVELY LOW-LATITUDE WAVE CONTINUES TO EXHIBIT
CYCLONIC TURNING OF THE LOW-LEVEL CLOUD FIELD IN THE VICINITY OF
THE WAVE AXIS BETWEEN 30W-36W. ISOLATED MODERATE CONVECTION IS
FROM 06N-08N BETWEEN 32W-36W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 16N16W TO
10N25W. SCATTERED MODERATE CONVECTION IS FROM 03N-08N BETWEEN
20W-30W.

...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 CENTERED OVER THE GULF OF TEHUANTEPEC
REGION IN THE E PACIFIC NEAR 15N95W. WATER VAPOR IMAGERY SHOWS
AN MIDDLE TO UPPER LEVEL SHORTWAVE ROTATING AROUND THE TROUGH
THAT IS CURRENTLY PROGRESSING ACROSS THE MISSISSIPPI RIVER DELTA
REGION. SIGNS OF FRONTOGENESIS ARE OCCURRING OVER THE NE GULF AS
A SURFACE TROUGH IS ANALYZED FROM THE SW NORTH ATLC WATERS
ACROSS THE NORTHERN FLORIDA PENINSULA TO 28N87W. WITH A COLD
FRONT BEGINNING TO FORM AND MOVE EASTWARD...DEWPOINTS HAVE BEEN
CONSISTENTLY IN THE MID 60'S ACROSS THE FLORIDA PANHANDLE THIS
MORNING AND REMAIN IN THE UPPER 60'S AND LOWER 70'S OVER THE
SOUTHERN FLORIDA PENINSULA. FARTHER WEST...REMNANT CONVECTION
FROM THE OVERNIGHT PERIOD FOCUSED ALONG AN OUTFLOW BOUNDARY
CONTINUES TO MOVE SOUTHWESTWARD OVER THE WESTERN GULF AND MERGE
WITH CONVECTION LOCATED WITHIN A WEAKNESS OF THE SURFACE RIDGE
IN PLACE ACROSS MUCH OF THE GULF. THESE SCATTERED SHOWERS AND
TSTMS ARE OCCURRING FROM 22N-29N BETWEEN 89W-97W. ANOTHER AREA
OF ISOLATED SHOWER ACTIVITY LINGERS OVER THE BAY OF CAMPECHE S
OF 20N BETWEEN 92W-95W. OTHERWISE AT THE SURFACE...A WEAK 1014
MB HIGH IS CENTERED NEAR 26N90W AND IS FORECAST TO MERGE WITH A
MARGINALLY STRONG HIGH DIVING SOUTHWARD FROM MONTANA TO OVER THE
CENTRAL CONUS BY EARLY FRIDAY.

CARIBBEAN SEA...
AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE E PACIFIC REGION INTO
THE WESTERN CARIBBEAN ALONG 18N TO 67W. 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 FROM 67W TO 83W WHERE LOW-LEVEL CONVERGENCE OCCURS
BETWEEN NORTHEAST WINDS ACROSS WESTERN CUBA AND THE NW CARIBBEAN
WATERS AND EASTERLIES FROM THE CENTRAL CARIBBEAN. A FEW ISOLATED
SHOWERS ARE OCCURRING WITHIN 60 NM OF A LINE FROM 16N84W TO
11N84W. ANOTHER AREA OF ISOLATED SHOWERS IS OVER THE WINDWARD
PASSAGE REGION FROM 15N-20N BETWEEN 73W-77W. FARTHER EAST...
TROPICAL STORM OPHELIA REMAINS WELL NORTHEAST OF THE NORTHERN
LEEWARD ISLANDS...HOWEVER...LOW-LEVEL MOISTURE CONVERGENCE IS
PRODUCING A FEW ISOLATED SHOWERS OVER THE LEEWARD ISLANDS AND NE
CARIBBEAN N OF 15N E OF 64W.

ATLANTIC OCEAN...
UPPER LEVEL TROUGHING IS THE DOMINANT FEATURE ACROSS THE EASTERN
CONUS AND THIS TROUGHING SUPPORTS A FORMING COLD FRONT FROM
32N80W TO THE NORTHERN FLORIDA PENINSULA NEAR 29N82W. A PRE-
FRONTAL SURFACE TROUGH IS ANALYZED FROM CAPE CANAVERAL NEAR
28N80W ACROSS THE FLORIDA STRAITS TO WESTERN CUBA NEAR 22N81W.
LOW-LEVEL CONVERGENCE EAST OF THE COLD FRONT AND IN THE VICINITY
OF THE SURFACE TROUGH IS GENERATING ISOLATED SHOWERS S OF 30N W
OF 70W AND WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS N OF 30N
W OF 71W. FARTHER EAST OVER THE CENTRAL ATLC...TROPICAL STORMS
OPHELIA AND PHILIPPE ARE TRACKING GENERALLY NORTH-NORTHWESTWARD
AND ARE EXPECTED TO REMAIN OVER THE OPEN ATLC HIGH SEAS WATERS
IN THE COMING DAYS. NORTH OF THE TROPICAL CYCLONE ACTIVITY...A
LONGWAVE UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY
ACROSS THE CENTRAL NORTH ATLC AND THIS TROUGHING DIPS TO 30N
BETWEEN 30W-50W IN SUPPORT OF A COLD FRONT ANALYZED FROM 32N37W
TO 28N51W. A PRE-FRONTAL TROUGH EXTENDS SE OF THE FRONT FROM
29N39W TO 24N49W. ISOLATED SHOWERS AND TSTMS ARE OCCURRING
WITHIN 60 NM EITHER SIDE OF THE COLD FRONT AND WITHIN 45 NM
EITHER SIDE OF A LINE FROM 30N34W TO 32N28W. OTHERWISE...THE
REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A
SURFACE RIDGE ANCHORED BY A 1021 MB HIGH CENTERED NEAR 27N26W.
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 10N-28N E OF 35W.

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

$$
HUFFMAN




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