[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 272333
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON 27 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 DEPRESSION JEANNE CENTER NEAR 32.8N 83.4W ABOUT 15 ENE
OF MACON GEORGIA AT 27/2100 UTC MOVING NNE 11 KT. MAXIMUM
SUSTAINED WIND SPEED 30 KT GUSTS 40 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE 992 MB.  SEE LATEST HPC PUBLIC ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KWNH FOR MORE DETAILS.
JEANNE CONTINUES TO PRODUCE VERY HEAVY RAIN ALONG ITS TRACK WITH
ISOLATED TORNADOES IN THE EASTERN SEMICIRCLE OF THE CYCLONE.

TROPICAL STORM LISA CENTER NEAR 21.5N 46.5W...OR ABOUT 1055
MILES/1700 KM...EAST-NORTHEAST OF THE LESSER ANTILLES AT 27/2100
UTC MOVING NNW 7 KT. MINIMUM CENTRAL PRESSURE IS 1003 MB. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/
WTNT23 KNHC FOR MORE DETAILS.  LISA HAS STRUGGLED MOST OF ITS
LIFE AND TODAY IS NO EXCEPTION.  STRONG WLY SHEAR HAS TAKEN
THE CONVECTION TO THE E AND N OF THE LOW-LEVEL CENTER.
SCATTERED MODERATE CONVECTION FROM 22N-24.5N BETWEEN 43W-46W.

...TROPICAL WAVES...
TROPICAL WAVE NEAR THE CAPE VERDE ISLANDS ALONG 23W/24W S OF 17N
MOVING W 15 KT.  THE WAVE IS MORE CONVECTIVE TODAY WITH WIDELY
SCATTERED MODERATE FROM 9N-11N BETWEEN 20W-25W AND WITHIN 90 NM
OF 14N26W.  RECENT SATELLITE PICTURES INDICATE THE WAVE MIGHT
HAVE TO REPOSITIONED A BIT FARTHER W IN THE NEXT ANALYSIS.

CENTRAL ATLC TROPICAL WAVE ALONG 40W/41W S OF 20N MOVING W 10-15
KT.  THIS WAVE HAS LITTLE CONVECTION BUT AN EARLIER QUIKSCAT
SHOWED A WELL-DEFINED LOW-LEVEL AXIS.

...ITCZ...
ITCZ AXIS IS ALONG 10N15W 4N30W 6N58W.  WIDELY SCATTERED
MODERATE FROM 3N-7N BETWEEN 21W-25W.  ISOLATED MODERATE WITHIN
90 NM OF AXIS BETWEEN 35W-42W.

...DISCUSSION...
FINALLY A QUIET NIGHT AT WORK WITH LISA FAR OUT TO SEA AND
JEANNE NOW HPC'S RESPONSIBILITY.  TO REFLECT ON HOW BUSY IT HAS
BEEN SO FAR... THIS IS THE MOST ACTIVE SEASON TO DATE UP UNTIL
SEPT 27 EVER SEEN IN TERMS OF NOAA'S ACCUMULATED CYCLONE ENERGY
(ACE) INDEX.  IN FACT...IF THE SEASON ENDED TODAY...2004 WOULD BE
THE 5TH MOST ACTIVE ACE SINCE RECORDS BEGAN IN 1851...WITH 1950-
1893-1995-1926 BEING THE TOP 4.  ONTO THE CURRENT WEATHER...

GULF OF MEXICO...
TROUGHING FROM JEANNE DOMINATES THE EASTERN GULF WHILE RIDGING
IS MOVING IN FROM MEXICO THRU THE WESTERN GULF.  NORTHERLY
SURFACE WINDS THROUGHOUT THE SE USA W OF JEANNE ARE KEEPING
DEWPOINTS VERY LOW FOR SEPT.  RIDGE AXIS EXTENDS FROM THE BAY OF
CAMPECHE TO SE TEXAS WITH ISOLATED TSTMS  NEAR THE MEXICAN
COAST.  BROAD HIGH PRESSURE IS EXPECTED TO BUILD AS JEANNE
DEPARTS IN THE MID/UPPER LEVELS THRU THE SOUTHERN GULF WITH FAST
SW FLOW FORECAST OVER THE GULF COAST STATES.

CARIBBEAN SEA...
UPPER TROUGH FROM CENTRAL CUBA TO 11N80W IS ASSISTING WIDELY
SCATTERED MODERATE CONVECTION SOUTH OF 15N W OF 76W.  THERE
COULD BE A WEAK TROPICAL WAVE IN THE AREA AS WELL.  TROUGH IS
SLOWLY MOVING W AND WILL LIKELY INCREASE SHOWER CHANCES OVER
CENTRAL AMERICA AND THE WESTERN CARIBBEAN WATERS TOMORROW.
DEEPER TROUGH EXTENDS FROM N OF PUERTO RICO NEAR 22N62W WSW
ACROSS HISPANIOLA.  GENERALLY DRY CONDITIONS NW OF TROUGH AXIS
WITH ISOLATED SHOWERS N OF 16N E OF 68W IN ENHANCED MID/UPPER
LEVEL MOISTURE.   THIS UPPER TROUGH IS EXPECTED TO CUT OFF FROM
THE MID-OCEANIC TROUGH AND MOVE WESTWARD... REPLACING THE W
CARIBBEAN TROUGH BY THE END OF THE WEEK.

SUBTROPICAL ATLANTIC OCEAN...
NARROW BAND OF MOISTURE IS ON WATER VAPOR PICTURES W OF 73W
UNDER A SMALL RIDGE.  MID-OCEANIC TROUGH DOMINATES THE W AND
CENTRAL ATLC OTHERWISE... STRETCHING FROM 30N50W TO 20N64W.  THE
WEATHER IS FAIRLY QUIET W OF THE TROUGH AXIS EXCEPT FOR ISOLATED
TRADE-WIND SHOWERS AND A FEW TSTMS WITHIN 60 NM OF 26N55W.  THE
TSTMS ARE ALONG A SURFACE TROUGH TO THE NW OF LISA FROM 25N50W TO
32N34W.  LISA IS CAUGHT IN SW SHEARING FLOW AHEAD OF THE UPPER
TROUGH WITH SOME RIDGING BUILDING ON THE N AND E SIDE OF THE
SYSTEM.  IN THE E ATLC LARGE UPPER LOW IS NEAR 20N28W WITH
GENERALLY DRY CONDITIONS N OF 20N E OF 30W.

TROPICAL ATLANTIC...
MID/UPPER ANTICYCLONE IS OVER THE W TROPICAL ATLC NEAR 15N50W
WITH RATHER DRY CONDITIONS ALOFT.  IT APPEARS THAT THE CAPE
VERDE SEASON HAS SHUT DOWN FOR NOW WITH A LARGE UPPER LOW NEAR
20N28W STRETCHING A TROUGH S TO 10N30W.  THIS FEATURE IS CAUSING
STRONG SHEAR IN THE E ATLC WITH LITTLE CHANCE OF TROPICAL
DEVELOPMENT.  THE LOW IS ENHANCING A TROPICAL WAVE'S CONVECTION
JUST SW OF THE CAPE VERDE ISLANDS. ITCZ CONVECTION IS ACTIVE E
OF 42W WITH MID/UPPER LEVEL MOISTURE LIMITED IN THE DEEP TROPICS
W OF 45W.  WITH KARL AND LISA MOVING ALONG SIMILAR PATHS...THE
TRADE WINDS HAVE BEEN QUITE WEAK ESPECIALLY AROUND THE LESSER
ANTILLES WITH MUCH WARMER-THAN-AVERAGE WATER TEMPERATURES.

$$
BLAKE


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