[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 311149
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

HURRICANE FRANCES CENTER NEAR 20.0N 63.4W OR ABOUT 200 MILES/
325 KM EAST-NORTHEAST OF SAN JUAN PUERTO RICO...AT 31/1200 UTC.
IT IS MOVING WEST 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
949 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.
LATEST SATELLITE IMAGERY SUGGEST THAT FRANCES IS BECOMING BETTER
ORGANIZED. CLOUD TOP TEMPERATURES ASSOCIATED WITH THE INNER
CONVECTION HAVE BEEN COOLING DURING THE LAST SEVERAL HOURS AND
THE EARLIER OBSCURED EYE HAS CLEARED OUT. UPPER LEVEL OUTFLOW
CONTINUES TO BE GOOD IN ALL QUADRANTS AND VERTICAL SHEAR IS
LOW.  THIS IS GENERALLY A FAVORABLE ENVIRONMENT FOR DEVELOPMENT
AND THE OFFICIAL FORECAST CALLS FOR GRADUAL STRENGTHENING DURING
THE NEXT FEW DAYS.  NUMEROUS STRONG CONVECTION WITHIN 90 NM OVER
THE S SEMICIRCLE AND 120 NM OVER THE N SEMICIRCLE.

TROPICAL DEPRESSION HERMINE WAS DECLARED EXTRATROPICAL AT
31/0900 UTC CENTERED NEAR 42.4N 69.9W OR ABOUT 60 MILES...EAST
OF BOSTON MASSACHUSETTS.  HERMINE IS MOVING NE AT 25 KT. MAXIMUM
SUSTAINED WINDS HAVE DECREASED TO 25 KT WITH GUSTS 35 KT AND THE
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1013 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.

TROPICAL STORM GASTON WAS CENTERED NEAR 38.4N 73.8W OR ABOUT 75
MILES... 125 KM...SOUTH-SOUTHEAST OF ATLANTIC CITY NEW JERSEY AT
31/0900 UTC. GASTON IS MOVING TOWARD THE EAST-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.  OUTER RAINBANDS ASSOCIATED WITH GASTON CONTINUE TO
AFFECT PORTIONS OF NEW JERSEY AND NEW YORK WITH LOCALLY HEAVY
RAINFALL.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE CAPE VERDE ISLANDS ALONG 23W/24W 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
SATELLITE IMAGERY...THE WAVE/LOW IS ONLY PRODUCING A SMALL AREA
OF SCATTERED MODERATE CONVECTION FROM 17N-19N BETWEEN 24W-26W.
THE SURROUNDING ENVIRONMENT REMAINS MARGINALLY FAVORABLE FOR
DEVELOPMENT.

CENTRAL ATLANTIC OCEAN TROPICAL WAVE APPROXIMATELY 800 NM E OF
BARBADOS ALONG 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 97W
SOUTH OF 20N MOVING WEST 15 TO 20 KT. NO ASSOCIATED DEEP
CONVECTION.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N10W 15N20W 8N40W 4N60W 7N80W.
SCATTERED MODERATE CONVECTION MOVING OFF THE COAST OF AFRICA
FROM 8N-13N BETWEEN 13W-18W. SCATTERED MODERATE CONVECTION FROM
7N-10N BETWEEN 51W-56W.

...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 AND THE
SE TEXAS COAST WITH ASSOCIATED DIVERGENCE/LIFT TO THE EAST
SUPPORTING WIDELY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
OVER THE FLORIDA PANHANDLE. THIS ACTIVITY SHOULD LIFT NEWD INTO
THE SE UNITED TODAY AS THE UPPER TROUGH FLATTENS. NW OF THE
TROUGH...VERY DRY MID-LATITUDE AIR IS MOVING SWD OVER TEXAS AND
EXTREME NW GLFMEX. ELSEWHERE...A NEARLY STATIONARY MID/UPPER
LEVEL ANTICYCLONE IS LOCATED OVER N FLORIDA WITH A RIDGE
EXTENDING SW TO THE CENTRAL GLFMEX NEAR 27N90W. THIS RIDGE IS
BEING ERODED BY A RETROGRADING UPPER LEVEL LOW JUST N OF THE
YUCATAN PENINSULA NEAR 23N87W.  UPPER DIVERGENCE/LIFT SE OF THE
UPPER LOW IS SUPPORTING INCREASING SHOWERS/THUNDERSTORMS OVER
THE SE GLFMEX AND FLORIDA KEYS. ANOTHER AREA OF SCATTERED
SHOWERS/THUNDERSTORMS IS LOCATED ALONG THE COAST OF MEXICO FROM
VERACRUZ TO TAMPICO.

CARIBBEAN SEA...
BROAD/WEAK 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.  THE UPPER
TROUGH WAS SUPPORTING POCKETS OF MODERATE CONVECTION OVER
CENTRAL AMERICA OVERNIGHT BUT THIS ACTIVITY HAS SINCE MOVED SWD
INTO THE E PACIFIC.  ANOTHER AREA OF WIDELY SCATTERED
SHOWERS/THUNDERSTORMS IS NOTED OVER W 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 ITCZ ACTIVITY OVER THE SW
CARIBBEAN.

SUBTROPICAL ATLANTIC OCEAN...
STRONG MID-LEVEL RIDGING CONTINUES TO DOMINATE MUCH OF THE ATLC
FROM THE AZORES TO FLORIDA. THE ONE EXCEPTION IS THE BAHAMAS
WHERE THE MID-OCEANIC TROUGH HAS SPLIT PRODUCING A LARGE
RETROGRADING UPPER LOW NEAR 25N77W. INSTABILITY ASSOCIATED WITH
THE COLD CORE LOW IS SUPPORTING SCATTERED MODERATE CONVECTION
OVER THE BAHAMAS PRIMARILY FROM 23N-25N BETWEEN 75W-77W. WHILE
THIS ACTIVITY HAS INCREASED IN INTENSITY OVERNIGHT...THERE ARE
NO SIGNS OF TROPICAL DEVELOPMENT AT THIS TIME.  OVER THE CENTRAL
ATLC...HURRICANE FRANCES IS THE PRIMARY FEATURE OF NOTE AS IT
MOVES WESTWARD AROUND THE SOUTH SIDE OF THE AFOREMENTIONED
MID-LEVEL RIDGE. FRANCES IS EXPECTED TO GRADUALLY TURN MORE
TOWARD THE WNW TODAY AND TONIGHT AS IT APPROACHES THE W
PERIPHERY OF THE RIDGE.  UW-CIMSS WATER VAPOR WINDS 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 33N20W 20N50W. THE TROUGH LACKS SIGNIFICANT DYNAMICS AND
ONLY ISOLATED SHOWERS/THUNDERSTORMS ACCOMPANY THE UPPER TROUGH.
AT THE SURFACE... SUBTROPICAL RIDGE LIES N OF THE AREA OVER THE
CENTRAL TO E ATLC THEN EXTENDING SWD FROM BERMUDA TO CENTRAL
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. THIS 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...CONFLUENT FLOW AND MODERATE SUBSIDENCE IN THE UPPER
LEVELS IS SUPPRESSING ITCZ/TROPICAL WAVE CONVECTION.

$$
RHOME






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