[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 310605
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE 31 AUG 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
0345 UTC.

...SPECIAL FEATURES...

HURRICANE FRANCES IS CENTERED NEAR 19.8N 62.1W OR ABOUT 140
MILES... 245 KM...NNE OF THE ST. MARTIN AT 31/0600 UTC.
FRANCES CONTINUES MOVING W 12 KT AROUND THE SOUTH SIDE OF A
STRONG MIDDLE LEVEL RIDGE. MAXIMUM SUSTAINED WIND SPEED REMAINS
110 KT WITH GUSTS 135 KT AND THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 951 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. WHILE UPPER LEVEL OUTFLOW ASSOCIATED
WITH FRANCES HAS IMPROVED OVER THE LAST SEVERAL HOURS...THERE
HAS BEEN LITTLE OVERALL CHANGE IN THE CONVECTIVE STRUCTURE OR
ORGANIZATION AND CLOUD TOP TEMPERATURES ASSOCIATED WITH THE
INNER CONVECTION REMAINS IN THE -65 TO -75 CELSIUS RANGE.
NUMEROUS STRONG ACTIVITY SURROUNDS THE RAGGED EYE WITHIN 60 NM
OVER THE S SEMICIRCLE AND 120 NM OVER THE N SEMICIRCLE.

TROPICAL STORM HERMINE IS CENTERED NEAR 41.5N 71.1W OR ABOUT
25 MILES...45 KM...SSE OF TAUNTON MASSACHUSETTS AT 31/0600 UTC.
HERMINE IS ACCELERATING NOW MOVING NNE AT 22 KT. MAXIMUM
SUSTAINED WINDS HAVE DECREASED TO 35 KT WITH GUSTS 45 KT AND THE
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1010 MB. SEE THE LATEST
NHC PUBLIC ADVISORY OR FORECAST/ADVISORY ISSUED UNDER AWIPS/WMO
HEADERS MIATCPAT3/WTNT33 KNHC OR MIATCMAT3/ WTNT23 KNHC FOR MORE
DETAILS. HERMINE REMAINS DEVOID OF DEEP CONVECTION.

GASTON HAS RE-EMERGED OVER THE ATLANTIC E OF DELMARVA AND
REGAINED TROPICAL STORM STRENGTH.TROPICAL STORM.  THE CENTER OF
CIRCULATION WAS CENTERED NEAR 37.7N 75.8W OR ABOUT 55 MILES
SOUTHWEST OF OCEAN CITY MARYLAND AT 31/0300 UTC. GASTON IS
MOVING TOWARD THE NORTHEAST NEAR 16 KT. MAXIMUM SUSTAINED WIND
SPEED IS 35 KT WITH GUSTS TO 45 KT AND THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1001 MB. SEE THE LATEST NHC ADVISORIES
ISSUED UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC OR
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.  GASTON HAS RE-EMERGED
OVER THE ATLANTIC E OF DELMARVA AND REGAINED TROPICAL STORM
STRENGTH. THE STRONGEST CONVECTION REMAINS JUST INLAND OVER
MARYLAND...S NEW JERSEY...AND DELAWARE.  LOCALLY HEAVY RAINS AND
POSSIBLE FLOODING WILL CONTINUE OVER THESE AREAS TONIGHT AS THE
CIRCULATION PULLS AWAY FROM THE COAST.

...TROPICAL WAVES...

TROPICAL WAVE JUST E OF THE CAPE VERDE ISLANDS ALONG 21W/22W
WITH A 1010 MB LOW NEAR 17N. THE WAVE IS MOVING WESTWARD NEAR 20
KT.  WHILE THERE IS AN IMPRESSIVE LOW LEVEL CIRCULATION IN
LATEST IR SATELLITE IMAGERY...THE WAVE/LOW IS LACKING DEEP
CONVECTION WITH ONLY A FEW ISOLATED THUNDERSTORMS.  THE
SURROUNDING ENVIRONMENT REMAINS MARGINALLY FAVORABLE FOR
DEVELOPMENT.

CENTRAL ATLANTIC OCEAN TROPICAL WAVE APPROXIMATELY 850 NM E OF
BARBADOS ALONG 45W/46W SOUTH OF 17N MOVING WEST 10 TO 15 KT. NO
SIGNIFICANT CONVECTION AT THIS TIME.

TROPICAL WAVE JUST W OF THE ISTHMUS OF TEHUANTEPEC ALONG 95W/96W
SOUTH OF 20N MOVING WEST 15 TO 20 KT. NO ASSOCIATED DEEP
CONVECTION.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N10W 13N20W 8N40W 8N70W 9N80W.
SCATTERED MODERATE CONVECTION MOVING OFF THE COAST OF AFRICA
FROM 7N-14N BETWEEN 10W-18W. WIDELY SCATTERED MODERATE
CONVECTION OVER THE CENTRAL ATLC FROM 6N-11N BETWEEN 30W-45W.

...DISCUSSION...

THE GULF OF MEXICO...
THE BIGGEST WEATHER MAKER OVER THE GLFMEX IS A MID/UPPER LEVEL
TROUGH MOVING ACROSS THE E UNITED STATES. THE BASE OF THE UPPER
LEVEL TROUGH NOW CLIPS THE NW GULF WATERS NEAR LOUISIANA WITH
ASSOCIATED DIVERGENCE/LIFT TO THE EAST SUPPORTING WIDELY
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ALONG THE N GULF
COAST FROM LOUISIANA EWD TO THE FLORIDA PANHANDLE. NW OF THE
TROUGH...VERY DRY MID-LATITUDE AIR IS LOCATED OVER LOUISIANA AND
TEXAS AND WILL GRADUALLY SINK SWD OVER THE NW GLFMEX DURING THE
NEXT 24 HOURS. ELSEWHERE...A MID/UPPER LEVEL ANTICYCLONE IS
LOCATED OVER N FLORIDA WITH A RIDGE EXTENDING SW TO THE CENTRAL
GLFMEX NEAR 27N90W. THIS RIDGE IS BEING UNDERCUT BY A
RETROGRADING UPPER LEVEL LOW JUST N OF THE YUCATAN PENINSULA
NEAR 23N87W.  WATER VAPOR IMAGERY SHOWS AMPLE MID-UPPER LEVEL
MOISTURE BUT THE LOWER LEVELS REMAIN RELATIVELY DRY. THIS IS
CURRENTLY KEEPING MUCH OF THE S HALF OF THE GLFMEX CONVECTION
FREE.

CARIBBEAN SEA...
BROAD UPPER LEVEL TROUGH EXISTS OVER THE W CARIBBEAN IN
ASSOCIATION WITH AN UPPER LOW WHICH SPLIT OFF THE MID-OCEANIC
TROUGH AND IS NOW RETROGRADING OVER THE SE GLFMEX.  INSTABILITY
ASSOCIATED WITH THE BROAD TROUGH IS SUPPORTING POCKETS OF
MODERATE CONVECTION OVER CENTRAL AMERICA PRIMARILY CONCENTRATED
ALONG THE PACIFIC COASTAL REGIONS FROM NICARAGUA TO THE ISTHMUS
OF TEHUANTEPEC.  SIMILAR ACTIVITY IS NOTED OVER CUBA IN
ASSOCIATION WITH A SECOND UPPER LOW OVER THE BAHAMAS.
ELSEWHERE...MODERATE SUBSIDENCE AND DRY AIR PREVAILS E OF 80W
WITH THE ONLY CONVECTION OF NOTE BEING ISOLATED THUNDERSTORMS
ITCZ ACTIVITY OVER THE SW CARIBBEAN.

SUBTROPICAL ATLANTIC OCEAN...
RATHER COMPLEX MID-UPPER LEVEL ENVIRONMENT CONTINUES ACROSS THE
SUBTROPICAL ATLC.  INDUCED RIDGING E OF FRANCES CONTINUES TO
SPLIT THE MID-OCEANIC TROUGH PRODUCING A LARGE RETROGRADING
UPPER LOW OVER THE CENTRAL BAHAMAS. INSTABILITY ASSOCIATED WITH
THE COLD CORE LOW IS SUPPORTING WIDELY SCATTERED TO LOCALLY
SCATTERED MODERATE CONVECTION OVER THE BAHAMAS PRIMARILY FROM
22N-25N BETWEEN 74W-79W.  OVER THE CENTRAL ATLC...HURRICANE
FRANCES IS THE MAIN FEATURE OF NOTE.  FRANCES IS LOCATED ON THE
SOUTH SIDE OF A STRONG MID-LEVEL RIDGE WHICH IS STEERING THE
HURRICANE ON A GENERAL WESTWARD MOTION.  UW-CIMSS WATER VAPOR
WINDS ALSO SHOWS AN UPPER LEVEL ANTICYCLONE POSITIONED JUST NE
OF FRANCES WHICH IS GENERATING GOOD UPPER LEVEL OUTFLOW AND LOW
SHEAR.  E OF FRANCES...THE E PORTION OF THE MID-OCEANIC TROUGH
IS DIGGING SWD ALONG 35N20W 22N50W. THE TROUGH LACKS SIGNIFICANT
DYNAMICS AND THERE IS NO ASSOCIATED DEEP CONVECTION.  AT THE
SURFACE... SUBTROPICAL RIDGE EXTENDS FROM BERMUDA SW OVER S
FLORIDA. STRONG PRESSURE GRADIENT BETWEEN FRANCES AND THE
SUBTROPICAL RIDGE IS CREATING MODERATE ELY FLOW BETWEEN
50W-70W.

TROPICAL ATLANTIC...
ASIDE FROM HURRICANE FRANCES...THE TROPICAL ATLC IS RATHER QUIET
WITH THE ONLY FEATURE OF NOTE BEING A TROPICAL WAVE NEAR THE
CAPE VERDE ISLANDS. THE TROPICAL WAVE IS CURRENTLY SITUATED NEAR
A MID/UPPER LEVEL LOW JUST W OF THE CAPE VERDE ISLANDS WHICH HAS
LIMITED DEVELOPMENT. THE UPPER LOW IS EXPECTED TO RETREAT NW AND
WEAKEN POSSIBLY ALLOWING THE ENVIRONMENT TO BECOME A BIT MORE
FAVORABLE. OVER THE REMAINDER OF THE TROPICAL ATLC...A WEAK
UPPER TROUGH BLANKETS MUCH OF THE TROPICAL ATLC WITH SUBSIDENCE
SUPPRESSING ITCZ/TROPICAL WAVE CONVECTION.

$$
RHOME


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