[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 271039
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...SPECIAL FEATURE...
HURRICANE FRANCES IS CENTERED NEAR 14.5N 48.4W AT 27/0900 UTC
MOVING WNW 12 KT.  MAXIMUM SUSTAINED WINDS 80 KT GUSTING TO 100
KT WITH THE ESTIMATED MINIMUM CENTRAL PRESSURE OF 975 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 AT 0600Z THERE WAS A WELL-DEFINED EYE EMBEDDED WITHIN THE A
SYMMETRIC AREA OF DEEP CONVECTION.  SHEAR REMAINS LIGHT AND IS
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 JUST EAST OF THE CAPE VERDE ISLANDS ALONG 21W-22W
S OF 22N MOVING W 10-15 KT.  A BROAD ROTATION IS NOTED ON
VISIBLE SATELLITE IMAGERY.  NO SIGNIFICANT CONVECTION ASSOCIATED
WITH THE WAVE AT THIS TIME.

TROPICAL WAVE OVER THE CENTRAL CARIBBEAN ALONG 71W SOUTH OF 16N
MOVING W 15-20 KT.  THIS WAVE REMAINS POORLY DEFINED IN
SATELLITE IMAGERY AND THE POSITION IS BASED ON EXTRAPOLATION.
THERE IS NO SIGNIFICANT CONVECTION OVER WATER... WITH IN THE
ITCZ SCATTERED MODERATE/ISOLATED STRONG CONVECTION REMAINS OVER
PARTS OF COLUMBIA FROM 5N-10N BETWEEN 71W-76W.

...ITCZ...
ITCZ EMERGES OFF THE COAST OF AFRICA NEAR 11N15W 7N30W 12N40W
9N70W.  ISOLATED MODERATE CONVECTION FROM 8N-15N BETWEEN 12W-19W
AND FROM 5N-9N BETWEEN 29W-32W.

...DISCUSSION...
GULF OF MEXICO...
MID/UPPER LEVEL RIDGE REMAINS OVER THE GULF 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 WIDELY SCATTERED 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 1016 MB LOW  LOCATED S OF CHARLESTON SC NEAR 32N80W IS
PRODUCING SCATTERED MODERATE CONVECTION WITH IN 130 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 A WEAK UPPER LOW ALONG 31N65W... ENHANCING
WIDELY SCATTERED MODERATE FROM 27N-31N BETWEEN 61W-65W.
MID-OCEANIC TROUGH IS ALONG 39N52W TO EASTERN CUBA NEAR 20N76W.
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.

TROPICAL ATLANTIC...
MID-UPPER LEVEL RIDGE EXTENDS FROM W AFRICA NEAR MAURITANIA WSW
TO 20N28W.  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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