[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 262330
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU 26 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2245 UTC.

...SPECIAL FEATURE...
TROPICAL STORM FRANCES HAS BEEN UPGRADED TO A HURRICANE CENTERED
NEAR 13.7N 46.4W AT 26/2100 UTC MOVING WNW 14 KT.  MAXIMUM
SUSTAINED WINDS ARE UP TO 70 KT GUSTING TO 85 KT WITH THE
ESTIMATED MINIMUM CENTRAL PRESSURE OF 983 MB.  SEE THE LATEST
NHC FORECAST/ ADVISORY ISSUED UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.  FRANCES IS STILL IN A
RAPID INTENSIFICATION PHASE WITH BANDING FEATURES BECOMING MORE
PROMINENT AND A SOLID CENTRAL DENSE OVERCAST (CDO).  SHEAR IS
LIGHT AND FORECAST TO STAY LIGHT FOR THE NEXT DAY OR TWO WITH
WARMER-THAN-AVERAGE WATERS IN ITS PATH.  CIRRUS IS FANNING OUT
ESPECIALLY IN THE SW THRU N TO NE QUADRANTS.

...TROPICAL WAVES...
TROPICAL WAVE EMERGING OFF THE COAST OF AFRICA ALONG 19W S OF
22N MOVING W 10-15 KT.  BROAD ROTATION SEEN IN SATELLITE
PICTURES WITH THE WAVE PASSING DAKAR EARLIER TODAY.  NO
SIGNIFICANT CONVECTION.

TROPICAL WAVE OVER THE E CARIBBEAN ALONG 67W/68W SOUTH OF 16N
MOVING W 15-20 KT.  UW-CIMSS SATELLITE ANALYSIS INDICATES THAT
THE WAVE MARKS THE LEADING EDGE OF SOME AFRICAN DUST.   NO
SIGNIFICANT CONVECTION OVER WATER.

...ITCZ...
ITCZ EMERGES OFF THE COAST OF AFRICA NEAR 12N15WSW TO 8N30W
13N40W 7N50W.  ISOLATED MODERATE FROM 6N-10N BETWEEN 24W-30W AND
WITHIN 60 NM OF 8N47W.

...DISCUSSION...
GULF OF MEXICO...
PERSISTENT MID/UPPER LEVEL RIDGE FROM S TEXAS TO SE LOUISIANA IS
BEING UNDERCUT BY A RETROGRADING UPPER LOW NEAR THE ISTHMUS OF
TEHAUNTEPEC.  LITTLE FORCING EXCEPT FOR THE GULF COAST SEABREEZE
IS KEEPING THE WEATHER FAIRLY QUIET W OF 90W.  FARTHER S... THE
UPPER LOW IS ENHANCING SIGNIFICANT CONVECTION OVER YUCATAN AND
GUATEMALA.  THE NE GULF REMAINS UNSETTLED WITH A DEEP-LAYERED
TROUGH FROM JACKSONVILLE TO THE CENTRAL GULF NEAR 24N86W WITH
LAND-BASED SHOWERS/TSTMS PREDOMINANTLY E OF THE TROUGH AXIS AND
WITH SOME ISOLATED SHOWERS OVER WATER N OF 25N E OF 90W.

CARIBBEAN SEA...
MID-OCEANIC TROUGH EXTENDS FROM THE CENTRAL ATLC ACROSS THE N
CARIBBEAN OVER HAITI TO GRAND CAYMAN INTO BELIZE.  SUBSIDENCE
OVER THE N PART OF THE AREA N OF 17NW OF 71W IS LIMITING DIURNAL
CONVECTION OVER CUBA.  A DIFFLUENT RIDGE OVER THE SW CARIBBEAN
IS ENHANCING WIDELY SCATTERED MODERATE CONVECTION BETWEEN
12N-15N FROM 80W-84W WITH AN EARLIER LARGE BLOWUP LEAVING
CONVECTIVE CIRRUS DEBRIS S OF 16N W OF 74W.

SUBTROPICAL ATLANTIC OCEAN...
WEAK 1017 MB LOW HAS FORMED JUST S OF CHARLESTON ACCORDING TO
SURFACE OBSERVATIONS.  EARLIER CONVECTION HAS DIED OUT WITH ONLY
ISOLATED MODERATE WITHIN 90 NM NE OF THE CENTER.  UPPER HIGH
NEAR 30N77W IS PROVIDING AT LEAST A CHANCE FOR THE SYSTEM TO
DEVELOP SLOWLY.. THOUGH ITS PROXIMITY TO LAND AND HIGH
DISORGANIZATION WILL LIKELY HINDER THIS PROCESS.   ELSEWHERE A
BIT FARTHER E ANOTHER SURFACE LOW...1019 MB... HAS FORMED JUST S
OF BERMUDA.  THIS FEATURE HAS MORE UPPER SUPPORT WITH AN UPPER
LOW FORMING ALONG 33N65W... ENHANCING WIDELY SCATTERED MODERATE
FROM 28N-30N BETWEEN 63W-68W.  MID-OCEANIC TROUGH IS ALONG
31N52W TO HAITI.  A SMALL UPPER LOW NEAR 30N54W IS ENHANCING
ISOLATED TSTMS FROM 26N-29N BETWEEN 52W-55W.    FARTHER E...
SUBSIDENCE/DRY AIR IN THE MID/UPPER LEVELS PREVAILS... LIMITING
SIGNIFICANT CLOUDS/CONVECTION. AT THE SURFACE...A BREAK IN THE
SUBTROPICAL RIDGE EXISTS OVER THE W ATLC IN ASSOCIATION WITH A
FRONTAL ZONE ALONG 32N W OF 60W. OVER THE E ATLC...RIDGE EXTENDS
FROM THE AZORES SW TO 27N47W.

TROPICAL ATLANTIC...
MID-UPPER LEVEL RIDGE EXTENDS FROM W AFRICA NEAR MAURITANIA WSW
ALONG 17N37W TO 17N53W.  A BREAK IN THE UPPER RIDGE IS PRESENT W
OF 55W IN ASSOCIATION WITH A WEAK TROUGH. STRONG SUBSIDENCE W OF
50W BLANKETS THE AREA WEST OF FRANCES WITH NO LACK OF DRY AIR IN
THE MID/UPPER LEVELS.  SSMI IMAGERY INDICATES THAT DESPITE THE
DRY AIR ALOFT PRECIPITABLE WATER VALUES ARE STILL ABOVE 1.75 FOR
A FEW DEGREES NW OF THE STORM.   THE CYCLONE IS MOVING ON THE SW
SIDE OF THE UPPER RIDGE WITH SPEED/WIND DIVERGENCE OVER THE
CYCLONE CERTAINLY ASSISTING CONVECTION.  MOISTURE IS ALSO
LACKING IN THE MID/UPPER LEVELS BETWEEN 40W-25W BEFORE
INCREASING WITH THE NEXT WAVE.

$$
BLAKE

WWWW
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