[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 011329
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED 01 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
1115 UTC.

...SPECIAL FEATURES...

AT 8AM AST/EDT OR 01/1200 UTC...HURRICANE FRANCES IS CENTERED
NEAR 21.4N 69.15W...OR ABOUT 130 MILES...210 KM...EAST OF GRAND
TURK ISLAND...0R 780 MILES...1260 KM...EAST-SOUTHEAST OF PALM
BEACH FLORIDA. FRANCES CONTINUES TO MOVE WNW 15 KT...16 MPH...
AROUND THE SOUTHERN PERIPHERY OF A STRONG MID-LEVEL RIDGE.
MAXIMUM SUSTAINED WIND SPEED IS 140 MPH/220 KM/HR WITH HIGHER
GUSTS...AND THE LATEST MINIMUM CENTRAL PRESSURE MEASURED BY
RECONNAISSANCE IS 937 MB. SEE THE LATEST NHC PUBLIC ADVISORY OR
FORECAST/ADVISORY ISSUED UNDER AWIPS/WMO HEADERS
MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS
AND WARNING INFORMATION. THE SATELLITE SIGNATURE ASSOCIATED WITH
FRANCES REMAINS EXCELLENT WITH GOOD UPPER LEVEL OUTFLOW IN ALL
QUADRANTS AND A WELL-DEFINED 20-25 NM WIDE EYE. SURROUNDING
CONVECTION IS SYMMETRIC ABOUT THE CENTER WITHIN 120 NM RADIUS
AND CLOUD TOP TEMPERATURES HAVE COOLED SLIGHTLY NOW IN THE -70
TO -80 DEGREE CELSIUS RANGE. FRANCES IS CURRENTLY WITHIN A
FAVORABLE MIDDLE TO UPPER LEVEL ENVIRONMENT AND SOME
INTENSIFICATION IS POSSIBLE AS IT TRACKS WEST-NORTHWEST AROUND
THE W PERIPHERY OF A MID-LEVEL RIDGE.

TROPICAL STORM GASTON WAS CENTERED NEAR 42.4N 61.5W OR ABOUT 185
MILES SOUTHEAST OF HALIFAX NOVA SCOTIA...AT 01/0900 UTC. GASTON
IS MOVING TOWARD THE EAST NORTHEAST AT 33 KT. MAXIMUM SUSTAINED
WINDS ARE 45 KT WITH GUSTS TO 55 KT AND THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 999 MB. SEE THE LATEST NHC ADVISORIES ISSUED
UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC OR
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. LATEST SATELLITE IMAGERY
INDICATES GASTON IS RAPIDLY BECOMING EXTRATROPICAL. SCATTERED TO
LOCALLY NUMEROUS MODERATE CONVECTION FROM 43N-46N BETWEEN
58W-62W INCLUDING THE EXTREME NE COAST OF NOVA SCOTIA.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC ALONG 32W/33W S OF 23N MOVING WEST
AT 20 KT.  A 1010 MB LOW IS ON THE WAVE AXIS NEAR 19N. SATELLITE
IMAGERY INDICATES THAT THERE HAS BEEN LITTLE OVERALL CHANGE IN
THE ORGANIZATION OF THIS SYSTEM DURING THE LAST 24 HOURS WITH
ONLY SMALL INTERMITTENT BURSTS OF DEEP CONVECTION NEAR THE LOW
LEVEL CIRCULATION. HOWEVER...THE SURROUNDING ENVIRONMENT REMAINS
FAVORABLE FOR DEVELOPMENT AND A TROPICAL DEPRESSION COULD FORM
DURING THE NEXT 48 HOURS.

CENTRAL ATLANTIC OCEAN TROPICAL WAVE IS APPROXIMATELY 350 NM E
OF BARBADOS ALONG 54W SOUTH OF 17N MOVING WEST 15 KT. ITCZ
CONVECTION NEAR THE WAVE HAS INCREASED OVERNIGHT WITH SCATTERED
MODERATE ACTIVITY FROM 7N-10N BETWEEN 52W-60W.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N10W 18N30W 7N45W 8N80W. ASIDE
FROM ACTIVITY NEAR TROPICAL WAVES...SCATTERED MODERATE TO STRONG
CONVECTION FROM 8N-12N BETWEEN 20W-23W.

...DISCUSSION...
GULF OF MEXICO...
STRONG MIDDLE LEVEL RIDGE OVER THE W ATLC WATERS EXTENDS
WESTWARD ACROSS N FLORIDA TO THE CENTRAL GLFMEX.  THE RIDGE IS
THEN SPLIT OVER THE CENTRAL GLFMEX BY A WEAK UPPER LEVEL TROUGH
EXTENDING N/S ALONG 89W/90W FROM THE YUCATAN PENINSULA TO SE
LOUISIANA.  STRONG MID/UPPER LEVEL RIDGING BECOMES ESTABLISHED
AGAIN OVER INTERIOR MEXICO EXTENDING NEWD ALONG THE SE TEXAS
COAST.  THE MID-LATITUDE TROUGH WHICH CLIPPED THE N GLFMEX OVER
LOUISIANA YESTERDAY HAS SINCE LIFTED JUST N OF THE AREA OVER THE
SE UNITED STATES TAKING WITH IT THE SHOWERS/THUNDERSTORMS
PREVIOUSLY OVER THE FLORIDA PANHANDLE.  FURTHER E...A LARGE
UPPER LOW OVER THE BAHAMAS RETROGRADING SLOWLY WESTWARD PRODUCED
AN IMPRESSIVE AREA OF SHOWERS/THUNDERSTORMS ALONG THE W COAST OF
FLORIDA OVERNIGHT.  THIS ACTIVITY HAS SINCE WEAKENED AND MOVED
WESTWARD INTO THE E GLFMEX FROM 25N-27N BETWEEN 84W-87W.
ISOLATED SHOWERS/THUNDERSTORMS OVER THE REMAINDER OF THE GLFMEX.

CARIBBEAN SEA...
BROAD/FLAT UPPER LEVEL TROUGH CONTINUES TO PRODUCE UNSETTLED
WEATHER OVER THE W CARIBBEAN. EARLIER CONVECTION OVER CUBA HAS
AND PORTIONS OF CENTRAL AMERICA DISSIPATED OVERNIGHT WITH ONLY
ISOLATED ACTIVITY REMAINING. HOWEVER...SHOWERS/THUNDERSTORMS
COULD BECOME MORE NUMEROUS LATER TODAY WITH AFTERNOON HEATING.
A WEAK UPPER LEVEL ANTICYCLONE AND ASSOCIATED DIFFLUENT FLOW
LOCATED OVER THE SW CARIBBEAN IS PRODUCING ISOLATED ITCZ
CONVECTION WITH THE STRONGEST STORMS FOCUSED NEAR SE NICARAGUA.
ELSEWHERE...STRONG SUBSIDENCE AND DRY AIR IN THE MIDDLE TO UPPER
LEVELS IS SUPPRESSING CONVECTION E OF 75W.

SUBTROPICAL ATLANTIC OCEAN...
THE LARGE-SCALE PATTERN OVER THE ATLC REMAINS ESSENTIALLY
UNCHANGED. STRONG MIDDLE LEVEL RIDGING CONTINUES OVER THE BULK
OF THE AREA EXTENDING FROM 40N40W SW ACROSS BERMUDA TO N FLORIDA
HURRICANE FRANCES IS MOVING AROUND THE S SIDE OF THE RIDGE JUST
N OF HISPANIOLA.  UW-CIMSS SATELLITE DERIVED WINDS CONTINUE TO
SHOW AN INDUCED UPPER LEVEL ANTICYCLONE OVER AND TO THE NE OF
FRANCES PRODUCING GOOD OUTFLOW AND LOW SHEAR.  IN FACT...THIS
FAVORABLE UPPER LEVEL PATTERN IS EXPECTED TO CONTINUE POSSIBLY
ALLOWING ADDITIONAL STRENGTHENING. THE INDUCED RIDGING NE OF
FRANCES HAS ALSO SPLIT THE UPPER LEVEL MID-OCEANIC TROUGH
PRODUCING A CUTOFF LOW OVER THE BAHAMAS NEAR GRAND BAHAMA
ISLAND.  THE UPPER LOW HAS BEEN SLOWLY RETROGRADING WESTWARD
TOWARD FLORIDA WITH ASSOCIATED INSTABILITY PROBABLY ENHANCING
AFTERNOON CONVECTION LATER TODAY OVER THE SUNSHINE STATE.
WIDELY SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO NOTED OVER THE N
HALF OF THE BAHAMAS.  EARLIER SHOWERS/THUNDERSTORMS OVER THE
BAHAMAS HAVE DISSIPATED AS LARGE SCALE SUBSIDENCE W OF FRANCES
IS MOVING OVER THE AREA.  OVER THE CENTRAL ATLC...LARGE UPPER
LEVEL LOW IS FORMING NEAR 24N46W AND MOVING SLOWLY WESTWARD.
WIDELY SCATTERED SHOWERS/THUNDERSTORMS ARE OCCURRING OVER THE W
SIDE OF THE UPPER LOW FROM 15N-25N BETWEEN 45W-53W.  OVER THE E
ATLC...E/W ORIENTED UPPER LEVEL RIDGE IS BUILDING ALONG 20N FROM
AFRICA WESTWARD TO 40W.  THE UPPER LEVEL RIDGE IS UNDERCUT BY A
WEAK MIDDLE LEVEL TROUGH FROM 15N40W TO JUST W OF THE CAPE VERDE
ISLANDS.  THIS FEATURE IS PRODUCING WIDELY SCATTERED MODERATE TO
STRONG CONVECTION FROM 15N-20N BETWEEN 30W-40W BUT IS LIMITING
DEVELOPMENT OF A TROPICAL WAVE W OF THE CAPE VERDE ISLANDS.

TROPICAL ATLANTIC...
ASIDE FROM HURRICANE FRANCES...THE TROPICAL ATLC REMAINS VERY
QUIET.  SUBSIDENCE AND DRY AIR IN THE MIDDLE TO UPPER LEVELS
CONTINUES TO LIMIT ITCZ CONVECTION WEST OF 30W.

$$
RHOME/NELSON



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