[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 271759
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
HURRICANE FRANCES IS CENTERED NEAR 15.0N 49.0W AT 27/1500 UTC
MOVING WNW 9 KT.  MAXIMUM SUSTAINED WINDS HAVE INCREASED TO 90
KT WITH GUSTS TO 110 KT MAKING FRANCES THE 4TH CATEGORY OF THE
TWO HURRICANE ON THE SAFFIR-SIMPSON SCALE. ESTIMATED MINIMUM
CENTRAL PRESSURE IS NOW 970 MB.  SEE THE LATEST NHC FORECAST/
ADVISORY ISSUED UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS.  THE SATELLITE SIGNATURE ASSOCIATED WITH
FRANCES CONTINUES TO IMPROVE. DURING THE LAST FEW HOURS...THE
DEEP CONVECTION HAS BECOME MORE SYMMETRIC ABOUT A 10-15 NM WIDE
EYE.  FRANCES IN LOCATED NEAR THE W PERIPHERY OF A MID-UPPER
LEVEL RIDGE ALONG 20N.  THIS SETUP IS PROVIDING A FAVORABLE
ENVIRONMENT COMPRISED OF LOW VERTICAL SHEAR AND GOOD UPPER LEVEL
OUTFLOW.  IN FACT...A WELL-DEFINED OUTFLOW CHANNEL IS EVIDENT
POLEWARD OF FRANCES.  FRANCES IS FORECAST TO REMAIN WITHIN A
FAVORABLE ENVIRONMENT OVER THE NEXT FEW DAYS WITH WARMER-
THAN-AVERAGE WATERS IN ITS PATH.

1015 MB LOW PRESSURE HAS FORMED OFF THE SE UNITED STATES COAST
APPROXIMATELY 125 NM SE OF CHARLESTON SOUTH CAROLINA.  LATEST
SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT THIS
AREA IS BECOMING BETTER ORGANIZED.  THE SYSTEM IS LOCATED WITHIN
A FAVORABLE AREA FOR DEVELOPMENT AND A TROPICAL DEPRESSION COULD
FORM ANYTIME WITHIN THE NEXT DAY OR SO.  WHILE THE STRONGEST
SHOWERS/THUNDERSTORM ACTIVITY LIES JUST OFFSHORE THE SE UNITED
STATES COAST...THIS ACTIVITY COULD AFFECT COASTAL AREAS OF NORTH
CAROLINA...SOUTH CAROLINA...AND GEORGIA DURING THE NEXT 24 HOURS
AS THE SYSTEM REMAINS NEARLY STATIONARY.

1016 MB LOW PRESSURE LOCATED APPROXIMATELY 200 NM S OF BERMUDA.
WHILE CONVECTION HAS INCREASED SE OF THE LOW CENTER DURING THE
DAY...THERE IS LITTLE INDICATION OF ORGANIZATION AT THIS TIME.
NONETHELESS...THE SYSTEM HAS THE POTENTIAL TO DEVELOP INTO A
TROPICAL DEPRESSION DURING THE NEXT DAY OR SO.

...TROPICAL WAVES...
TROPICAL WAVE JUST WEST OF THE CAPE VERDE ISLANDS ALONG 26W S OF
22N MOVING W 10-15 KT.  THIS WAVE HAS BECOME A LITTLE BETTER
DEFINED IN SATELLITE IMAGERY BUT STILL LACKS DEEP CONVECTION.
THERE IS A SMALL AREA OF SCATTERED MODERATE ITCZ ACTIVITY TO THE
WEST FROM 6N-9N BETWEEN 28W-33W.  A LARGER AREA OF ACTIVITY IS
LOCATED OVER W AFRICA BUT THIS APPEARS MORE DIRECTLY RELATED TO
THE NEXT WAVE STILL INLAND.

TROPICAL WAVE OVER THE CENTRAL CARIBBEAN ALONG 75W SOUTH OF 16N
MOVING W 15-20 KT.  THIS WAVE REMAINS POORLY DEFINED IN
SATELLITE IMAGERY AND THE POSITION IS BASED ON THE SURFACE
ANALYSIS WHICH SHOWED A BROAD AREA OF LOWER PRESSURE. THE WAVE
REMAINS VOID OF DEEP CONVECTION.

...ITCZ...
ITCZ EMERGES OFF THE COAST OF AFRICA NEAR 10N15W EXTENDING
WESTWARD ALONG 9N30W 15N43W 7N57W 11N70W 7N80W. WIDELY SCATTERED
TO LOCALLY SCATTERED MODERATE CONVECTION EMERGING OFF THE COAST
OF AFRICA FROM 6N-14N BETWEEN 10W-20W.

...DISCUSSION...
GULF OF MEXICO...
MID/UPPER LEVEL RIDGE REMAINS OVER THE N HALF OF THE GLFMEX
EXTENDING FROM N MEXICO NEAR 25N103W NEWD OVER SE LOUISIANA INTO
THE SE UNITED UNITED STATES. THE RIDGE IS BEING UNDERCUT BY A
RETROGRADING UPPER LOW ALONG THE S COAST OF MEXICO BETWEEN
ACAPULCO AND THE GULF OF TEHUANTEPEC.  THIS UPPER PATTERN
CONTINUES TO PRODUCE LARGE SCALE SUBSIDENCE/DRY AIR ACROSS A
MAJORITY OF THE AREA SAVE THE NE GLFMEX WHERE A SHORTWAVE TROUGH
FROM JACKSONVILLE TO THE CENTRAL GULF IS PRODUCING WIDELY
SCATTERED SHOWERS/TSTMS FROM 26N-30N BETWEEN 83W-88W. AT THE
SURFACE...REMNANT FRONTAL TROUGH FROM N FLORIDA TO 25N92W IS
DISRUPTING THE SUBTROPICAL RIDGE WITH GENERALLY LIGHT SE FLOW
ACROSS THE AREA.

CARIBBEAN SEA...
MID-OCEANIC TROUGH EXTENDS FROM THE CENTRAL ATLC ACROSS THE N
CARIBBEAN FROM HISPANIOLA TO THE E TIP OF THE YUCATAN
PENINSULA.  SUBSIDENCE ALONG AND N OF THE TROUGH CONTINUES TO
COVER ALL OF CUBA AND THE EXTREME NW CARIBBEAN INCLUDING JAMAICA
AND THE CAYMAN ISLANDS.  FURTHER S...A WELL-DEFINED MID/UPPER
LEVEL RIDGE EXTENDS FROM THE COLUMBIA/VENEZUELA BORDER NW TO THE
YUCATAN PENINSULA. THE RIDGE HAS BEEN NEARLY STATIONARY DURING
THE LAST 24 HOURS ALLOWING AN AREA OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION TO PERSIST WITHIN 30 NM EITHER SIDE
OF A LINE FROM W COLOMBIA NEAR 8N76W TO SE NICARAGUA NEAR
13N85W. HOWEVER...NUMERICAL GUIDANCE INDICATES THE RIDGE WILL
BEGIN RETREATING SLOWLY WEST DURING THE NEXT 12-24 HOURS
ALLOWING THE AREA OF CONVECTION TO MOVE INTO CENTRAL AMERICA.

SUBTROPICAL ATLANTIC OCEAN...
A RATHER ACTIVE PATTERN IS UNFOLDING OVER THE W SUBTROPICAL ATLC
AS TWO AREAS OF LOW PRES FORM ALONG AN OLD FRONTAL BOUNDARY
WHICH HAS BEEN STATIONARY FOR SEVERAL DAYS.  THE MOST NOTICEABLE
OF THESE FEATURES IS A 1015 MB LOW JUST OFF THE SE UNITED STATES
NEAR 32N78W. LATEST VISIBLE SATELLITE IMAGERY INDICATES THAT
THIS AREA HAS BECOME BETTER ORGANIZED DURING THE DAY AND THIS
SYSTEM HAS THE POTENTIAL TO BECOME A TROPICAL DEPRESSION OVER
THE NEXT DAY OR SO AS IT REMAINS NEARLY STATIONARY.
CURRENTLY...THE SYSTEM IS PRODUCING A LARGE AREA OF SCATTERED
MODERATE CONVECTION FROM 28N-34N BETWEEN 75W-80W. FURTHER E...A
SECOND AREA OF LOW PRESSURE HAS FORMED APPROXIMATELY 200 NM S OF
BERMUDA NEAR 29N65.5W. WHILE CONVECTION HAS INCREASED SE OF THE
LOW CENTER...THERE IS LITTLE INDICATION OF ORGANIZATION AT THIS
TIME.  CURRENTLY...SCATTERED MODERATE CONVECTION FROM 26N-32N
BETWEEN 60W-67W.  OVER THE CENTRAL ATLC...MID-OCEANIC TROUGH
EXTENDS FROM 30N51W INTO THE CARIBBEAN OVER HISPANIOLA.  WATER
VAPOR IMAGERY INDICATES THAT THE TROUGH HAS BEEN THINNING OUT
DURING THE LAST 24 HOURS AS A STRONG ANTICYCLONE DEVELOPS OVER S
FLORIDA AND A SECOND MID-LATITUDE TROUGH DROPS SWD OVER
BERMUDA.  THE E ATLC REMAINS UNDER MODERATE TO STRONG SUBSIDENCE
AND DRY/TRANQUIL WEATHER.  THE ONLY FEATURE OF NOTE IS A
MID-UPPER LEVEL TROUGH EXTENDING FROM BETWEEN THE AZORES AND
CANARY ISLANDS TO 25N40W. AT THE SURFACE...SUBTROPICAL RIDGE
REMAINS DISRUPTED OVER THE W ATLC BY AFOREMENTIONED LOW PRESSURE
AREAS. THE RIDGE IS MORE PRONOUNCED OVER THE E ATLC FROM THE
AZORES TO 30N50W.

TROPICAL ATLANTIC...
THE MAIN WEATHER MAKER CONTINUES TO HURRICANE FRANCES...NOW A
CATEGORY TWO STORM...AS IT MOVES WNW. THE HURRICANE IS
POSITIONED EQUATORWARD OF A MID-UPPER LEVEL RIDGE EXTENDING FROM
W AFRICA NEAR MAURITANIA WSW TO 20N50W. THIS PATTERN IS
PRODUCING A LOW SHEAR ENVIRONMENT ACROSS MUCH OF THE TROPICAL
ATLC.  A BREAK IN THE UPPER RIDGE IS PRESENT W OF 50W IN
ASSOCIATION WITH A WEAK TROUGH W OF HURRICANE FRANCES. MODERATE
SUBSIDENCE AND MIDDLE TO UPPER LEVEL DRY AIR BLANKETS THE AREA
WEST TO THE LESSER ANTILLES.  MODERATE SUBSIDENCE AND DRY AIR IS
ALSO PRESENT E OF FRANCES TO THE CAPE VERDE ISLANDS.

$$
RHOME






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