[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 270549
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI 27 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
0545 UTC.

...SPECIAL FEATURE...
HURRICANE FRANCES IS CENTERED NEAR 14.0N 47.3W AT 27/0300 UTC
MOVING WNW 13 KT.  MAXIMUM SUSTAINED WINDS 75 KT GUSTING TO 90
KT WITH THE ESTIMATED MINIMUM CENTRAL PRESSURE OF 980 MB.  SEE
THE LATEST NHC FORECAST/ ADVISORY ISSUED UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.  FRANCES CONTINUES TO
INTENSIFICATION  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 LOCATED ABOUT 200 NM E OF THE CAPE VERDE ISLANDS
ALONG 20W S OF 22N MOVING W 10-15 KT.  BROAD ROTATION IS NOTED
FROM SATELLITE IMAGERY ALONG WITH SURFACE OBSERVATION FROM 0400
UTC.  NO SIGNIFICANT CONVECTION ASSOCIATED WITH THE WAVE AT THIS
TIME.

TROPICAL WAVE OVER THE CENTRAL CARIBBEAN ALONG 69W 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 12N15W 8N30W 12N40W
7N50W.  ISOLATED MODERATE FROM 8N-13N BETWEEN 12W-13W AND FROM
6N-10N BETWEEN 29W-30W.

...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.  NEARLY ALL OF THE UPSTREAM MOISTURE AND DYNAMICS
ARE RIDING UP OVER THE RIDGE PRODUCING A DRY/TRANQUIL PATTERN W
OF 90W.  FARTHER S... A UPPER LOW IS HELPING TO ENHANCE MODERATE
CONVECTION OVER YUCATAN AND GUATEMALA.  THE NE GULF REMAINS
UNSETTLED WITH A DEEP-LAYERED TROUGH FROM JACKSONVILLE TO THE
CENTRAL GULF NEAR 22N91W WITH WIDELY SCATTERED SHOWERS/TSTMS
PREDOMINANTLY E OF THE TROUGH AXIS.

CARIBBEAN SEA...
MID-OCEANIC TROUGH EXTENDS FROM THE CENTRAL ATLC ACROSS THE N
CARIBBEAN OVER HAITI TO GRAND CAYMAN INTO BELIZE.  SUBSIDENCE
OVER THE E PART OF THE AREA N OF 10N E OF 71W IS LIMITING
CONVECTION. FURTHER S... A MID/UPPER LEVEL RIDGE EXTENDS FROM
COLUMBIA NW TO THE YUCATAN PENINSULA WITH  MODERATE/ STRONG
SCATTERED CONVECTION REMAINING MOSTLY OVER COLUMBIA BETWEEN
7N-10N FROM 71W-754W.

SUBTROPICAL ATLANTIC OCEAN...
A WEAK 1017 MB LOW  LOCATED S OF CHARLESTON SC NEAR 32N80W IS
PRODUCING SCATTERED MODERATE CONVECTION WITH IN 90 NM OF CENTER.
ELSEWHERE FARTHER E ANOTHER SURFACE LOW...1019 MB... HAS FORMED
JUST S OF BERMUDA NEAR 30N64W.  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 30N53W TO HAITI NEAR 19N75W.  A
SMALL UPPER LOW NEAR 30N53W IS ENHANCING ISOLATED TSTMS FROM
26N-29N BETWEEN 55W-56W.    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 62W. OVER THE E ATLC...RIDGE EXTENDS FROM THE
AZORES SW TO 27N43W.

TROPICAL ATLANTIC...
MID-UPPER LEVEL RIDGE EXTENDS FROM W AFRICA NEAR MAURITANIA WSW
ALONG 17N30W 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.  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.

$$
JP/RG


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