[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 010604
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...SPECIAL FEATURES...

HURRICANE FRANCES IS CENTERED NEAR 21.0N 67.9W...OR ABOUT 185
MILES... 340 KM... EAST OF GRAND TURK ISLAND...AT 01/0600 UTC.
IT IS MOVING WNW 15 KT AROUND THE SOUTHERN PERIPHERY OF THE
SUBTROPICAL RIDGE. MAXIMUM SUSTAINED WIND SPEED IS MEASURED BY
RECON AT 140 MPH/220 KM/HR WITH HIGHER GUSTS...AND THE RECON
MEASURED MINIMUM CENTRAL PRESSURE IS 939 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 REMAIN IN THE -65 TO -75
DEGREE CELSIUS RANGE.  FRANCES IS FORECAST TO REMAIN WITHIN A
FAVORABLE ENVIRONMENT AS IT TRACKS AROUND THE W PERIPHERY OF A
RIDGE IN THE MIDDLE LEVELS OF THE ATMOSPHERE AND ADDITION
STRENGTHENING IS POSSIBLE.

TROPICAL STORM GASTON WAS CENTERED NEAR 41.8N 66.0W OR ABOUT 230
MILES... 365 KM...SOUTH-SOUTHWEST OF HALIFAX NOVA SCOTIA... AT
01/0300 UTC. GASTON IS MOVING TOWARD THE EAST NORTHEAST AT 27
KT. MAXIMUM SUSTAINED WINDS ARE 35 KT WITH GUSTS TO 45 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 LOSING TROPICAL CHARACTERISTICS AND
BEGINNING EXTRATROPICAL TRANSITION. SCATTERED TO LOCALLY
NUMEROUS MODERATE CONVECTION FROM 41N-45N BETWEEN 62W-65W
INCLUDING THE S COAST OF NOVA SCOTIA.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC ALONG 30W 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. 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 400 NM E
OF BARBADOS ALONG 52W SOUTH OF 17N MOVING WEST 15 KT. THIS WAVE
REMAINS VOID OF SIGNIFICANT CONVECTION.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N10W 15N30W 8N50W 8N80W. WIDELY
SCATTERED MODERATE CONVECTION FROM 4N-12N BETWEEN 10W-21W.
SIMILAR ACTIVITY OVER N PORTIONS OF S AMERICA FROM 3N-10N
BETWEEN 65W-75W.

...DISCUSSION...

GULF OF MEXICO...
STRONG MIDDLE TO UPPER LEVEL RIDGE OVER THE W ATLC WATERS
EXTENDS WESTWARD ACROSS N FLORIDA.  THE RIDGE IS THEN SPLIT OVER
THE CENTRAL GLFMEX BY AN UPPER LEVEL TROUGH FROM LOUISIANA TO
THE YUCATAN PENINSULA.  STRONG MID/UPPER LEVEL RIDGING IS ALSO
PRESENT 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 NEWD INTO 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.  THIS
ACTIVITY IS NOW MOVING WESTWARD INTO THE E GLFMEX FROM 24N-29N
BETWEEN 81W-84W. ANOTHER AREA OF SHOWERS/THUNDERSTORMS AFFECTED
THE COAST OF MEXICO FROM TAMPICO TO VERACRUZ BUT HAS SINCE
DISSIPATED.

CARIBBEAN SEA...
BROAD/FLAT UPPER LEVEL TROUGH CONTINUES TO PRODUCE UNSETTLED
WEATHER OVER THE W CARIBBEAN. EARLIER CONVECTION OVER CUBA HAS
DISSIPATED WITH ONLY ISOLATED ACTIVITY REMAINING ALONG THE S
COAST.  AN IMPRESSIVE AREA OF CONVECTION OVER THE YUCATAN
PENINSULA HAS MOVED SWD NOW ENTERING N PORTIONS OF GUATEMALA.  A
WEAK UPPER LEVEL ANTICYCLONE AND ASSOCIATED DIFFLUENT FLOW
LOCATED OVER THE SW CARIBBEAN IS AIDING ITCZ CONVECTION WITH THE
STRONGEST AND MOST NUMEROUS ACTIVITY FOCUSED OVER 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 THE AZORES SW TO FLORIDA WITH
HURRICANE FRANCES MOVING AROUND THE S SIDE OF THE RIDGE JUST N
OF PUERTO RICO.  UW-CIMSS SATELLITE DERIVED WINDS CONTINUE TO
SHOW FRANCES IS SITUATED SW OF A WELL-DEFINED ANTICYCLONE
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
SPLIT THE MID-OCEANIC UPPER LEVEL TROUGH PRODUCING A CUTOFF LOW
OVER THE BAHAMAS NEAR 25N79W.  THE UPPER LOW HAS BEEN SLOWLY
RETROGRADING WESTWARD TOWARD FLORIDA WITH ASSOCIATED INSTABILITY
ENHANCING TYPICAL CONVECTIVE ACTIVITY.  WIDELY SCATTERED
SHOWERS/THUNDERSTORMS ARE ALSO NOTED OVER THE N HALF OF THE
BAHAMAS.  SUBSIDENCE AROUND THE PERIPHERY OF FRANCES HAS CLEARED
OUT THE S BAHAMAS.  OVER THE CENTRAL ATLC...LARGE UPPER LEVEL
LOW IS FORMING NEAR 23N46W AND MOVING SLOWLY WESTWARD. WIDELY
SCATTERED SHOWERS/THUNDERSTORMS ARE OCCURRING OVER THE W SIDE OF
THE UPPER LOW FROM 21N-29N BETWEEN 45W-51W.  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 16N-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


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