[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291109
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM 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 0600 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 1015 UTC.

...SPECIAL FEATURES...
THE REMNANT LOW CENTER OF JEANNE...NOW AN EXTRATROPICAL
CYCLONE...WAS NEAR 39.5N 73.3W...OR ABOUT 67 MILES EAST OF
ATLANTIC CITY NEW JERSEY...AT 29/1100 UTC. MAXIMUM SUSTAINED
WIND SPEED 35 MPH WITH SOME HIGHER GUSTS...MOVING NORTHEAST
30 MPH. MINIMUM CENTRAL PRESSURE 998 MB OR 29.47 INCHES.

TROPICAL STORM LISA CENTER NEAR 28.0N 46.1W AT 29/0900 UTC...
OR ABOUT 1300 MILES/2095 KM...WEST-SOUTHWEST OF THE AZORES.
MOVING NORTH 10 KT. MAXIMUM SUSTAINED WIND SPEED 60 KT GUSTS
75 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 991 MB. SEE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/
WTNT23 KNHC FOR MORE DETAILS. LISA COULD BECOME A HURRICANE
DURING THE NEXT 24 HOURS...AND IF IT DOES SO WOULD BE THE
EIGHTH HURRICANE OF THE SEASON. TROPICAL STORM FORCE WINDS
EXTEND OUTWARD UP TO 200 MILES/325 KM FROM THE CENTER.
SHOWERS AND THUNDERSTORMS ARE INCREASING TO THE NORTH...RATHER
THAN NORTHEAST OF THE CENTER...AND THE UPPER LEVEL CIRRUS IS
BEGINNING TO PUSH OUTWARD IN THE NORTHWEST QUADRANT...ALTHOUGH
THE SYSTEM REMAINS SHEARED WITH A SHARPLY ELONGATED LOW LEVEL
CIRCULATION. THIS IS CONSISTENT WITH THE FORECAST OF AN UPPER
LEVEL CUTOFF LOW TO THE SOUTHWEST OF LISA...WHICH SHOULD ACT TO
REDUCE THE SHEAR AND ALLOW LISA TO BECOME A HURRICANE DURING
THE NEXT 24 HOURS BEFORE THE SYSTEM MOVES OVER COOLER WATERS.
MODERATE TO STRONG SHOWERS AND THUNDERSTORMS FROM 28N TO 29N
BETWEEN 45W AND 46.5W...AND FROM 28.5N TO 30.5N BETWEEN 41.5W
AND 43.5W. BROKEN TO OVERCAST MULTILAYERED CLOUDS COVER THE
ATLANTIC WATERS FROM 26N TO 34N BETWEEN 38W AND 50W.

...TROPICAL WAVES...
TROPICAL WAVE ALONG 34W/35W SOUTH OF 16N MOVING WEST 10 TO
15 KT. CONDITIONS ARE NOT FAVORABLE FOR TROPICAL GENESIS WITH
A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER NEAR
19N33W...APPEARING TO BE MOVING IN PHASE WITH THIS WAVE DURING
AT LEAST THE LAST 24 HOURS. THE CYCLONIC FLOW FROM 10N TO 30N
BETWEEN 25W AND 40W WILL PROVIDE LOTS OF WESTERLY SHEAR. THIS
CYCLONIC CENTER WILL BE BUMPING INTO DIRECTLY AN UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTER NEAR 17N47W. WIDELY SCATTERED
MODERATE TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS FROM
12N TO 15N BETWEEN 30W AND 35W.

TROPICAL WAVE ALONG 45W/46W SOUTH OF 16N MOVING WEST 10 TO
15 KT. ISOLATED MODERATE TO LOCALLY STRONG SHOWERS AND
THUNDERSTORMS FROM 8N TO 11N BETWEEN 44W AND 48W.

TROPICAL WAVE 90W/91W SOUTH OF 22N MOVING WEST 10 TO 15 KT.
NO SHOWERS AND THUNDERSTORMS OVER INTERIOR SECTIONS OF CENTRAL
AMERICA DIRECTLY ATTRIBUTABLE TO THIS WAVE. UPPER LEVEL WESTERLY
WINDS FROM A MIDDLE TO UPPER LEVEL TROUGH FROM THE ATLANTIC
OCEAN...ACROSS PUERTO RICO AND HISPANIOLA INTO THE CENTRAL
CARIBBEAN SEA...ARE SHEARING THE CLOUD TOPS IN THE SOUTH CENTRAL
AND SOUTHWESTERN CARIBBEAN SEA.

...ITCZ...
ITCZ 14N17W 8N26W 8N32W 8N37W 9N44W 9N48W 10N63W...10N76W
10N85W IN THE SOUTHWESTERN CARIBBEAN SEA AND INTO THE EASTERN
PACIFIC OCEAN JUST WEST OF COSTA RICA. WIDELY SCATTERED TO
SCATTERED MODERATE AND STRONG SHOWERS AND THUNDERSTORMS IN
CLUSTERS FROM 3N TO 9N BETWEEN 27W AND 37W...AND FROM 12N
TO 14N BETWEEN 21W AND 23W. THE SHOWERS AND THUNDERSTORMS
OF EARLIER IN THE SOUTHWESTERN CARIBBEAN SEA HAVE BEEN SHEARED
TO SOME DEGREE BY THE UPPER LEVEL WESTERLY FLOW FROM A TROUGH
FROM THE ATLANTIC OCEAN TO THE CENTRAL CARIBBEAN SEA. STRONG
SHOWERS AND THUNDERSTORMS REMAIN...HOWEVER...SOUTH OF 10N
BETWEEN 76W AND 79W...AND IN THE GULF OF URABA.

...DISCUSSION...

THE GULF OF MEXICO...
DRIER AIR HAS FILTERED INTO THE NW GULF THANKS TO NLY WINDS FROM
JEANNE BEHIND A CENTRAL GULF SURFACE TROUGH. A NEW PUSH OF
COOLER/DRIER AIR IS STARTING WITH A COLD FRONT MOVING INTO THE
EXTREME NW GULF NOW. THIS FRONT IS NOT EXPECTED TO MOVE THROUGH
THE ENTIRE GULF WITH A NE-SW ORIENTED UPPER RIDGE FROM THE
SOUTHWESTERN GULF OF MEXICO TO THE FLORIDA STRAITS. THE UPPER
LEVEL TROUGH SOUTH OF THE REMNANT OF JEANNE IS MOVING OFF THE
UNITED STATES MIDDLE ATLANTIC COAST...NORTHEASTWARD...DRAGGING
UPPER LEVEL WESTERLY WINDS WITH IT ACROSS FLORIDA. MIDDLE TO
UPPER LEVEL DRY AIR WITHIN 120 NM ON EITHER SIDE OF LINE THROUGH
32N78W TO 27N84W TO 22N89W.

THE CARIBBEAN SEA...
BIG AREA OF UPPER LEVEL DIFFLUENT FLOW ALONG WITH THE ITCZ...
IS FORCING A LARGE AREA OF CLOUDS AND SHOWERS AND
THUNDERSTORMS...SOME DISSIPATING DURING THE LAST FEW HOURS...IN
THE SOUTH CENTRAL AND SOUTHWESTERN CORNER. SMALL UPPER TROUGH
ALONG IN THE NORTHWESTERN CARIBBEAN IS WEAKENING AND MOVING INTO
CENTRAL AMERICA. LARGE MIDDLE TO UPPER LEVEL TROUGH FROM THE
ATLANTIC INTO THE CENTRAL CARIBBEAN SEA DOMINATES THE WEATHER
PATTERN IN THE EASTERN CARIBBEAN. ENHANCED MIDDLE TO UPPER LEVEL
MOISTURE HELPS TO ENHANCE THE SHOWER/THUNDERSTORM CAPABILITIES.

THE SUBTROPICAL ATLANTIC OCEAN...
DEEP-LAYERED ANTICYCLONIC CIRCULATION CENTER NEAR 31N68W WITH
GENERAL ANTICYCLONIC FLOW AND DRY CONDITIONS WEST OF 60W. A
MIDDLE TO UPPER LEVEL TROUGH LEADING INTO THE CARIBBEAN SEA
OVER PUERTO RICO AND THE DOMINICAN REPUBLIC IS CAUSING A STRONG
EASTERLY JET NORTH OF PUERTO RICO. MIDDLE TO UPPER LEVEL TROUGH
IS DIGGING JUST WEST OF 50W NORTH OF 25N...LIFTING T.S. LISA
MORE NORTHWARD. RIDGING CONTROLS THE CENTRAL ATLC EAST OF LISA
TO 30W EXCEPT FOR CYCLONIC FLOW SOUTH OF 24N EAST OF 35W FROM A
MID/UPPER LEVEL CYCLONIC CIRCULATION CENTER NEAR 19N32W. WEAK
SURFACE RIDGE IN THE WESTERN ATLANTIC OCEAN WEST OF WEST OF 60W.
LISA DOMINATES THE CENTRAL ATLANTIC OCEAN. BROAD RIDGE THROUGH
32N31W TO 20N32W.

THE TROPICAL ATLANTIC OCEAN...
MIDDLE TO UPPER LEVEL ANTICYCLONIC CIRCULATION CENTER NEAR
17N47W AND MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER
NEAR 19N33W ARE THE MAIN FEATURES IN THE BASIN. GENERALLY DRY
AIR IN THE MIDDLE TO UPPER LEVELS WEST OF 40W WITH THE ONLY
WEATHER NEAR THE ITCZ AND A TROPICAL WAVE.  ENHANCING MOISTURE
IS EAST OF THE UPPER LOW INTO WEST AFRICA THOUGH UPPER WINDS
ARE NOT FAVORABLE FOR TROPICAL GENESIS. COMPUTER MODELS SUGGEST
INCREASING SHEAR OVER THE TROPICAL ATLC DURING THE NEXT FEW
DAYS...PERHAPS ENDING THE RECENT OUTBURST OF TROPICAL CYCLONE
ACTIVITY.

$$
MT


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