[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 031218
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI 03 SEP 2004

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 0945 UTC.

...SPECIAL FEATURES...

THE EYE OF CATEGORY THREE HURRICANE FRANCES AT 8 AM EDT/ 03/1200
UTC...WAS NEAR LATITUDE 25.3 NORTH...LONGITUDE 76.4 WEST OVER
ELEUTHERA ISLAND IN THE BAHAMAS. THIS POSITION ALSO IS ABOUT 260
MILES/400 KM...EAST-SOUTHEAST OF THE FLORIDA LOWER EAST COAST.
MAXIMUM SUSTAINED WIND SPEED 120 MPH GUSTS 195 KT. MINIMUM
CENTRAL PRESSURE 957 MB. SEE LATEST NHC PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC AND THE
FORECAST/ADVISORY UNDER HEADERS MIATCMAT1/WTNT21 KNHC FOR
ADDITIONAL INFORMATION. NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS FROM 24N-26N BETWEEN 74W-78W. THE OUTERMOST RAIN
BANDS HAVE BEEN MOVING ACROSS THE FLORIDA EAST COAST AND STRAITS
OF FLORIDA. A HEAVIER BAND IS MOVING SE THROUGH THE CAY SAL BANK
AND ONTO THE NORTH COAST OF CUBA AT THE MOMENT. UPPER OUTFLOW
EXTENDS NORTH AS FAR AS 34N AND AS FAR EAST AS 62W. OUTFLOW OVER
THE WEST SEMICIRCLE IS RESTRICTED BY UPPER LEVEL SHEARING AND
POSSIBLY SOME DRY AIR INTRUSION FROM MODIFIED AIR OVER
CUBA...ALL AIDING IN A WEAKENING STAGE.

TROPICAL STORM IVAN HAS DEVELOPED...CENTER NOW NEAR 10.0N 30.7W
AT 03/0900 UTC...MOVING WEST 14 KT. MAXIMUM SUSTAINED WIND SPEED
35 KT GUSTS 45 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 1005 MB.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. NUMEROUS STRONG SHOWERS
AND THUNDERSTORMS FROM 7.5N TO 11.5N BETWEEN 30W AND 36W.

...TROPICAL WAVES...

TROPICAL WAVE 25N42W TO 1012 MB LOW PRESSURE CENTER NEAR
20N43W...TO 8N44W...MOVING WEST 15 KT. SCATTERED TO NUMEROUS
STRONG SHOWERS AND THUNDERSTORMS FROM 23N TO 25N BETWEEN 39W
AND 41W...AND FROM 22N TO 23N BETWEEN 42W AND 43W.

TROPICAL WAVE ALONG 63W/65W SOUTH OF 24N MOVING WEST 10 TO 15 KT.
ISOLATED TO WIDELY SCATTERED MODERATE/LOCALLY STRONG SHOWERS AND
THUNDERSTORMS IN VENEZUELA FROM 7N TO 10N BETWEEN 64W AND 68W
MAY BE ENHANCED BY THIS WAVE AND THE ITCZ. THE WAVE IS BECOMING
INCREASINGLY INFLUENCED BY NORTHWEST-TO-WEST SHEAR AS A LARGE
UPPER LEVEL CYCLONIC CIRCULATION CENTER ROTATES WESTWARD IN THE
DIRECTION OF THE NORTHERN LEEWARD ISLANDS. DRY AIR NEAR THIS
CYCLONIC CENTER IS LIMITING DEEP CONVECTIVE ACTIVITY.

...ITCZ...

ITCZ 15N17W 12N26W 8N31W 10N42W 10N45W 8N60W...AND IN THE
SOUTHWESTERN CORNER OF THE CARIBBEAN SEA FROM 8N77W IN COLOMBIA
TO 9N83W IN PANAMA. ISOLATED TO WIDELY SCATTERED MODERATE/
LOCALLY STRONG SHOWERS AND THUNDERSTORMS FROM 10N TO 16N BETWEEN
50W AND 60W...TO THE SOUTH OF THE ATLANTIC-TO-CARIBBEAN SEA
MIDDLE TO UPPER LEVEL TROUGH. ISOLATED TO WIDELY SCATTERED
MODERATE/ LOCALLY STRONG SHOWERS AND THUNDERSTORMS FROM 16N TO
22N BETWEEN 50W AND 62W EVEN CLOSER TO THIS TROUGH. ISOLATED
MODERATE SHOWERS AND THUNDERSTORMS FROM 5N TO 10N BETWEEN AFRICA
COAST AND 24W...AND FROM 6N TO 8N BETWEEN 41W AND 44W.

...DISCUSSION...

GULF OF MEXICO...
A MID TO UPPER LAYER TROUGH EXTENDS SOUTH INTO THE GULF ALONG
31N87W 25N92W THROUGH THE BAY OF CAMPECHE TO A SMALL UPPER
CYCLONE OVER THE GULF OF TEHUANTEPEC AT 16N94W WITH THE TROUGH
CONTINUING SW INTO THE TROPICAL EAST-PACIFIC TO A BASE NEAR
6N98W. THE TROUGH IS SHIFTING WEST OVER THE GULF OF MEXICO SOUTH
OF 25N. AT THE LOW LEVELS A TROUGH IS ANALYZED ALONG THE TEXAS
COASTAL PLAINS. ASSOCIATED UPPER SUBSIDENCE IS NOTED WITHIN 90
NM EITHER SIDE OF THE UPPER TROUGH AND IS SUPPRESSING CONVECTION
TO ISOLATED MODERATE WITHIN 90 NM OF THE DEEP TROUGH AXIS.

TO THE E OF THIS TROUGH...AN UPPER ANTICYCLONE...CONTRIBUTING TO
THE STEERING OF HURRICANE FRANCES...IS OVER THE FLORIDA BIG BEND
AT 30N84W WITH A RIDGE EXTENDING SW TO 27N88W. A SMALL UPPER
CYCLONE IS CENTERED NEAR 22N85W AND IS MOVING WEST WITH TIME.
UPPER DIFFLUENCE WITHIN 180 NM OVER THE N SEMICIRCLE OF THIS
CYCLONE IS ENHANCING WIDELY SCATTERED SHOWERS AND A FEW
THUNDERSTORMS ALONG 23N BETWEEN 84W-88W. ELSEWHERE E OF THE
TROUGH...SCATTERED SHOWERS AND THUNDERSTORMS ARE CLUSTERED NEAR
29N86W AND ARE MOVING ANTICYCLONICALLY NORTH-NORTHEAST AROUND
THE STEERING RIDGE. BROAD UPPER SUBSIDENCE COVERS FLORIDA E OF
85W AND EXTENDS INTO THE ATLANTIC TO 79W...INCLUDING THE STRAITS
OF FLORIDA. THIS SUBSIDENCE W OF THE HURRICANE FRANCES IS
EXPECTED AND WILL HOPEFULLY ASSIST FLORIDIANS IN THEIR FINAL
HURRICANE PREPARATIONS THIS MORNING.

TO THE WEST OF THE TROUGH...THE UPPER ANTICYCLONE FROM HURRICANE
HOWARD HAS ITS RIDGE EXTENDING NE ACROSS OLD MEXICO ALONG
20N105W TO A SHARP CREST OVER THE W-CENTRAL GULF AT 24N95W. THE
MOISTURE PLUME FROM HOWARD'S CONVECTION CONTINUES TO ADVECT NE
ACROSS CENTRAL OLD MEXICO...SE TEXAS...AND ACROSS THE NW GULF OF
MEXICO. SOME OF THIS MOISTURE SPILLS SE AROUND THE RIDGE BACK
ACROSS MEXICO W OF 96W INTO THE TROPICAL EAST-PACIFIC. UNDER
THIS MOISTURE PLUME...WIDELY SCATTERED SHOWERS AND A FEW
THUNDERSTORMS ARE FLARING OVER THE NORTHWEST GULF AS THEY MOVE
ANTICYCLONICALLY WITH THE MID LEVEL STEERING FROM THE RIDGE.
NOTE THAT A RE LARGE AMOUNT OF THIS UPPER DEBRIS MOISTURE IS
ADVECTED NE ACROSS THE MISSISSIPPI VALLEY INTO THE NORTHEAST
CONUS.

CARIBBEAN...
A SMALL UPPER ANTICYCLONE HAS DEVELOPED SW OF HURRICANE FRANCES
NEAR 21N80W AND IS CONTRIBUTING TO THE WESTERLY SHEAR THAT
FRANCES IS EXPERIENCING. A SMALL UPPER CYCLONE IS OVER THE
YUCATAN CHANNEL ACCOMPANIED BY STRONG UPPER LEVEL SUBSIDENCE AND
CONVECTION IS SUPPRESSED. THIS SUPPRESSION WILL PROVIDE
BEAUTIFUL SAILING WEATHER IN THE NORTHWEST CARIBBEAN WHERE MANY
CRUISE SHIPS AND RECREATIONAL CRAFT ARE HOLDING WAITING FOR
HURRICANE FRANCES TO MOVE NORTH...ALLOWING PORT ENTRY TO RESUME
IN SOUTHERN FLORIDA.

UPPER DEBRIS MOISTURE FROM CONVECTION OVER VENEZUELA IS
SPREADING NE ACROSS THE SOUTHEAST CARIBBEAN. UPPER DEBRIS
MOISTURE ACCOMPANIED BAY A FEW SHOWERS AND THUNDERSTORMS...ARE
MOVING SOUTHWEST INTO THE NORTHEAST CARIBBEAN...ASSOCIATED WITH
AN UPPER CYCLONE AT 16N60W...WHICH IS SHIFTING WEST WITH TIME.

ELSEWHERE...THE UPPER LEVELS OF THE CARIBBEAN ARE DOMINATED BY
THE UPPER ANTICYCLONE FROM HURRICANE FRANCES...WITH STRONG UPPER
SUBSIDENCE SUPPRESSING CONVECTION. THINNING DEBRIS MOISTURE FROM
HURRICANE FRANCES IS STILL SPREADING SOUTHWEST OVER THE REGION
NORTH OF 17N BETWEEN 68W-78W.

REMAINDER OF SUBTROPICAL ATLANTIC...
AN UPPER LEVEL TROUGH LIES NEARLY STATIONARY ALONG 32N6W TO AN
UPPER CYCLONE DEVELOPING AT 24N23W...WITH A CYCLONIC SHEAR AXIS
EXTENDING NORTHWEST TO ANOTHER UPPER CYCLONE WHICH HAS CUT OFF
AT 34N32W. THIS TROUGH AND SHEAR AXIS ARE IDENTIFIED BY MODERATE
TO STRONG UPPER SUBSIDENCE WITHIN 120 EITHER SIDE OF THEIR AXIS.
AN UPPER ANTICYCLONE IS NOTED AT 19N38W WITH A RIDGE AMPLIFYING
NORTH ALONG 40W TO A SHARP CREST AT 36N41W. ASSOCIATED UPPER
DIFFLUENCE IS ENHANCING SCATTERED CONVECTION NE OF THE SURFACE
LOW AT 20N43W. AN UPPER CYCLONE IS POSITIONED JUST TO THE WEST
OF THE RIDGE NEAR 32N46W WITH A TROUGH SOUTHWEST ALONG 27N51W TO
AN UPPER CYCLONE NEAR 16N60W.  DEEP UPPER MOISTURE IS NOTED OVER
THE ATLANTIC WITHIN 300 NM EITHER SIDE OF LINE 32N38W
16N57W.

TROPICAL ATLANTIC...
UPPER DIFFLUENCE IS ENHANCING SCATTERED SHOWERS AND
THUNDERSTORMS FROM 11N-19N BETWEEN 60W-51W. UPPER RIDGING AND
DEEP-LAYERED ELY FLOW OVER THE EAST ATLC IS EXPECTED TO EXPAND
WESTWARD ALLOWING FAVORABLE ENVIRONMENT TO TRACK WEST WITH
TROPICAL STORM IVAN ALLOWING FURTHER STRENGTHENING. FARTHER EAST
...THE SQUALL LINE OVER WEST AFRICA IS LOSING ITS STRENGTH ALONG
12W...BUT SOME OF THE CONVECTION WILL LIKELY APPROACH THE
ATLANTIC WATERS LATE TODAY.

$$
MT/NELSON



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