[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 292346
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED 29 SEP 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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
2315 UTC.

...SPECIAL FEATURES...
TROPICAL STORM LISA IS CENTERED NEAR 30.9N 45.9W AT 29/2100 UTC
MOVING N 10 KT. MAXIMUM SUSTAINED WIND SPEED IS 60 KT GUSTS 75
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS.  TSTMS HAVE WEAKENED AROUND THE CENTER HOWEVER
THE STORM HAS A DAY OR SO TO BECOME A HURRICANE OVER DECREASING
SSTS BUT LIGHT VERTICAL WIND SHEAR.  CONVECTION IS WRAPPING ON
THE SOUTHERN SIDE OF THE CIRCULATION WITH SCATTERED WEAK/
MODERATE WITHIN 75 NM OF THE CENTER.

...TROPICAL WAVES...
TROPICAL WAVE IS ABOUT MIDWAY BETWEEN AFRICA AND THE LESSER
ANTILLES ALONG 37W S OF 16N MOVING W 10-15 KT.  BROAD TURNING
SEEN ALONG THE WAVE WITH A WEAK LOW/MID-LEVEL CIRCULATION NEAR
12N.  HOWEVER VERTICAL WIND SHEAR IS PREVENTING DEVELOPMENT.
ISOLATED MODERATE FROM 10N-13N BETWEEN 30W-38W.

TROPICAL WAVE IS ALONG 47W S OF 16N MOVING W 10-15 KT.
SATELLITE PICTURES INDICATE THAT THIS AREA HAS WEAK TURNING IN
THE LOW LEVELS BUT ONLY SPORADIC CONVECTION.  ISOLATED MODERATE
FROM 8N-11.5N BETWEEN 46W-51W.  THIS SYSTEM IS FORECAST TO MOVE
ACROSS THE LESSER ANTILLES LATE FRI/EARLY SAT.

TROPICAL WAVE IS ALONG 93W S OF 20N MOVING W 10-15 KT.  THIS IS
A WEAK WAVE WITH NO SIGNIFICANT CONVECTION IN THE ATLC BASIN.

...ITCZ...
ITCZ IS CENTERED ALONG 10N14W 7N27W 8N44W 9N61W.  WIDELY
SCATTERED MODERATE WITHIN 90 NM OF 5N40W.  ISOLATED MODERATE
FROM 3N-9N BETWEEN 29W-39W AND FROM 3N-8N BETWEEN 20W-26W.

...DISCUSSION...
...GULF OF MEXICO...
COLD FRONT IS OVER THE CENTRAL GULF FROM ABOUT PENSACOLA SSW TO
28N90W INTO THE SW BAY OF CAMPECHE.  THIS IS GENERALLY A DRY
FRONT WITH ONLY ISOLATED MODERATE IN THE SW GULF S OF 23N W OF
92W.  FRONT ISN'T EXPECTED TO MAKE MUCH MORE PROGRESS DUE TO A
NE-SW ORIENTED MID/UPPER RIDGE FROM THE FLORIDA STRAITS TO THE
SW GULF.  PATTERN IS SOMEWHAT STAGNANT WITH LITTLE CHANGE LIKELY.

CARIBBEAN SEA...
TSTMS KEEP FIRING IN THE SW CARIBBEAN ON THE DIVERGENT SIDE OF A
BIG UPPER LOW S OF HISPANIOLA.  WIDELY SCATTERED MODERATE S OF
14N W OF 79W WITH STRONG TSTMS NEAR THE COAST OF NW COLOMBIA.
DRY NE WINDS ARE OVER THE NW CARIBBEAN WITH GENERALLY QUIET
WEATHER AND LOTS OF MID/UPPER SUBSIDENCE.  HIGH CLOUDS OVER MOST
OF THE E CARIBBEAN DUE TO TSTM BLOWOFF AND UPPER LIFT FROM THE
UPPER LOW S OF HISPANIOLA ADVECTING THE MOISTURE EASTWARD TOWARD
THE LESSER ANTILLES.  THIS UPPER LOW IS ALSO PRODUCING LOTS OF
RAIN WITH ISOLATED SHOWERS PRESENT N OF 16N E OF PUERTO RICO IN
THE MOISTURE-RICH ENVIRONMENT.  IN ADDITION..WIDELY SCATTERED
SHOWERS ARE FROM 12N-17N BETWEEN 65W-71W.  LOW WILL BE SPREADING
LOCALLY HEAVY RAINS ACROSS HISPANIOLA TONIGHT INTO THE REST OF
THE CENTRAL CARIBBEAN TOMORROW.  THE W CARIBBEAN MIGHT BE A
PLACE TO WATCH FOR TROPICAL GENESIS WITH MODELS DEVELOPING UPPER
RIDGING IN THE AREA BEHIND THE UPPER LOW MOVING THRU THE AREA
OVER THE NEXT FEW DAYS.

SUBTROPICAL ATLANTIC OCEAN...
LITTLE CHANGE TO THE PATTERN WITH A DEEP-LAYERED RIDGE OVER THE
W ATLC AND A SURFACE TROUGH ALONG 61W N OF 25N.  STRONG NLY
SHEAR IS ENHANCING ISOLATED MODERATE WITHIN 60 NM OF 27N61W.
LISA IS PINWHEELING AROUND A DEVELOPING MID/UPPER LOW NEAR
29N50W.  UPPER LOW HAS A TROUGH SW TO 21N58W WITH ISOLATED
SHOWERS BETWEEN 20N-25N BETWEEN 45W-55W.   GENERALLY WLY FLOW IN
THE E ATLC SAVE CYCLONIC FLOW S OF 25N BETWEEN 25W-40W FROM A
MID/UPPER LEVEL LOW NEAR 19N34W.  AT THE SURFACE... LISA BREAKS
UP WEAK RIDGING OVER THE ATLC ALONG 45W WITH RIDGE AXIS INTO THE
W ATLC ALONG 31N64W TO 28N77W.

TROPICAL ATLANTIC...
MID/UPPER HIGH NEAR 15N50W AND A MID/UPPER LOW NEAR 19N34W ARE
THE MAIN FEATURES IN THE BASIN.  LIFT/SHEAR FROM THE E ATLC
UPPER LOW IS ENHANCING SCATTERED MODERATE CONVECTION BETWEEN
8N-14N FROM 26W-31W.  IN THE W...MID/UPPER LEVELS ARE STILL
RATHER DRY WITH A SMALL ISLAND OF DEEP-LAYERED MOISTURE AROUND
THE TROPICAL WAVE NEAR 47W.

$$
BLAKE


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