[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 302354
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU 30 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 33.6N 47.9W AT 30/2100 UTC
MOVING NNW 10 KT. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH
GUSTS TO 75 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS.  AFTER HAVING MINIMAL
CONVECTION OVERNIGHT...TSTMS HAVE RE-DEVELOPED AROUND A RAGGED
EYE.  LISA IS FLIRTING WITH HURRICANE INTENSITY BUT TIME IS
RUNNING OUT FOR FUTURE STRENGTHENING AS THE STORM CROSSES THE
24C SST LINE LATER TODAY.  GENERALLY THESE WATER TEMPS DO NOT
SUPPORT A HURRICANE BUT LISA HAS COOLER-THAN-AVERAGE UPPER TEMPS
TO WORK WITH DUE TO ITS PREVIOUS INTERACTION WITH AN UPPER LOW.
WIDELY SCATTERED MODERATE WITHIN 90 NM OF THE CENTER.

...TROPICAL WAVES...
TROPICAL WAVE INTRODUCED ALONG 27W S OF 16N MOVING W 10-15 KT.
TIMESECTIONS FROM SAL SHOW AN INCREASE IN MOISTURE AND SE WINDS
IN THE LOW/MID LEVELS. THE GFS ALSO SUGGESTS A WAVE JUST W OF
THAT LOCATION.  SCATTERED MODERATE FROM 9N-13N BETWEEN 24W-28W.

TROPICAL WAVE IS OVER THE EASTERN ATLANTIC ALONG 41W S OF 15N
MOVING W 10 KT. WEAK LOW/MID LEVEL CIRCULATION ALONG 11.5N
MARKS THE WAVE AXIS WITH WLY SHEAR PREVENTING DEVELOPMENT.
ISOLATED MODERATE WITHIN 60 NM OF 12N42W.

TROPICAL WAVE APPROACHING THE LESSER ANTILLES ALONG 52W/53W S OF
16N MOVING W 10-15 KT.  LAST VISIBLE SATELLITE SHOWED WEAK
TURNING BUT NO OTHER EVIDENCE OF ORGANIZATION.  WAVE SHOULD
INCREASE THE CHANCE OF RAIN FOR THE E CARIBBEAN ESPECIALLY IN
THE WINDWARD ISLANDS LATE FRI INTO SAT.  EARLIER CONVECTION HAS
DIMINISHED WITH ISOLATED MODERATE FROM 9N-13N BETWEEN 50W-55W.

...ITCZ...
ITCZ IS CENTERED ALONG 10N15W 6N20W 7N39W 9N61W.  ISOLATED
MODERATE WITHIN 60 NM OF 7.5N39W AND 3N33W.  SCATTERED MODERATE
FROM 4N-7N BETWEEN 19W-24W.

...DISCUSSION...
GULF OF MEXICO AND ATLANTIC OCEAN W OF 65W...
STATIONARY FRONT IS DISSIPATING OVER THE N GULF FROM THE FLORIDA
PANHANDLE INTO THE GULF A COUPLE HUNDRED MILES S OF LAFAYETTE
LOUISIANA.  TROUGH FROM THIS FRONT REMAINS IN THE BAY OF
CAMPECHE WITH ISOLATED MODERATE WITHIN 60 NM OF AXIS FROM 20N96W
TO 25N91W.  MID/UPPER RIDGING REMAINS FROM THE SW GULF INTO THE
FLORIDA PENINSULA IN A NEARLY STATIONARY PATTERN.  SUMMER
SHOWERS ARE LIMITED TO FLORIDA TODAY WITH RATHER DRY SURFACE AIR
OVER MOST OF THE GULF COAST STATES.

CARIBBEAN SEA...
LARGE MID/UPPER LOW NEAR 16N76W IS THE MAIN STORY WITH SCATTERED
TSTMS ON THE E SIDE OF THE SYSTEM FROM HISPANIOLA TO S AMERICA
FROM 70W-75W.  LOW IS MOVING W 15 KT WITH EVIDENCE THAT
TROUGHING HAS DEVELOPED AT THE SURFACE ALONG 74W IN THE
CARIBBEAN.  THIS IS THE MAIN AREA TO WATCH FOR ANY TROPICAL
DEVELOPMENT WITH THE LOW MOVING WESTWARD... LEAVING AT LEAST A
MARGINALLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT ON ITS E SIDE
WITH RIDGING FORMING IN ITS WAKE.  SURFACE PRESSURES ARE FAIRLY
LOW WITH ARUBA REPORTING 1008 MB THIS AFTERNOON.  ISOLATED HEAVY
RAINS ARE POSSIBLE OVER HISPANIOLA TONIGHT INTO TOMORROW.  W OF
THE LOW.... GENERALLY DRY CONDITIONS ARE PRESENT WITH MODERATE
SUBSIDENCE OVER THE OCEAN.  FARTHER INLAND.. DEEP-LAYERED
MOISTURE IS HIGHER OVER CENTRAL AMERICA WITH A MORE TYPICAL
SCATTERED TSTM DAY THERE.

SUBTROPICAL ATLANTIC OCEAN E OF 65W...
DEEP-LAYERED LOW IS NEAR 25N52W WEAKENING TO A TROUGH AT THE
SURFACE.  CYCLONIC FLOW IS N OF 18N W OF 46W WITH ISOLATED TSTMS
IN NLY FLOW ON THE BACKSIDE OF THE SYSTEM WITHIN 90 NM OF
24N61W.  LISA IS JUST N OF THIS LOW WITH WATER VAPOR WINDS
INDICATING THAT IT HAS SEPARATED FROM THE FEATURE TO THE S.
WEAK RIDGE IS BETWEEN THE LOW AND A CENTRAL ATLC MID/UPPER LOW
NEAR 20N36W.  LOW IS PULLING UP MID/UPPER MOISTURE FROM THE DEEP
TROPICS AND SLINGING IT EASTWARD INTO THE E ATLC.  GENERAL WLY
FLOW IS IN THE E ATLC OTHERWISE WITH A TROUGH DIPPING INTO THE
AREA N OF 30N30W.  LITTLE CHANGE TO THE SURFACE PATTERN WITH THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE EXTENDING INTO THE NW
BAHAMAS AND LISA BREAKING THE RIDGE IN THE CENTRAL ATLC.

TROPICAL ATLANTIC...
UPPER WLYS ARE INCREASING OVER MUCH OF THE AREA WITH THE RIDGE
AXIS SINKING TO ALONG 11N E OF THE ISLANDS TO 10N40W THEN NE
ACROSS THE CAPE VERDES ISLANDS AND E INTO SENEGAL.  MID/UPPER
MOISTURE IS ALSO LIMITED WITH GENERALLY DRY CONDITIONS S OF 18N
W OF 40W.  A MID/UPPER LOW IS NEAR 20N36W ENHANCING SCATTERED
MODERATE CONVECTION WITHIN 60 NM OF 15N31W. THE LOW IS FORECAST
TO MOVE NW OUT OF THE AREA IN A COUPLE OF DAYS.  THE E ATLC
MIGHT BE SOMEWHAT FAVORABLE FOR DEVELOPMENT WITH RIDGING IN
PLACE AND PLENTY OF DEEP-LAYERED MOISTURE THOUGH ANY SYSTEM
WOULD BE FIGHTING A LOT OF SHEAR N OF 15N.

$$
BLAKE


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