[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 301837
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 30 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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
1815 UTC.

...SPECIAL FEATURE...

A WESTERN CARIBBEAN SEA 1008 MB SURFACE LOW PRESSURE CENTER IS
NEAR 19N83W...ABOUT 260 NM EAST OF THE SOUTHEASTERN YUCATAN
PENINSULA...MOVING NORTH-NORTHWEST 5 TO 10 KT DURING THE LAST
24 HOURS. THE 24 HOUR FORECAST IS FOR THIS LOW CENTER TO MOVE
WEST-SOUTHWEST AND BE NEAR THE YUCATAN PENINSULA COAST. WIDELY
SCATTERED TO SCATTERED MODERATE/ISOLATED STRONG SHOWERS AND
THUNDERSTORMS ARE FOUND FROM THE HONDURAS COAST TO CUBA BETWEEN
80W AND 87W. OTHER SIMILAR SHOWERS AND THUNDERSTORMS ARE FOUND
ELSEWHERE IN THE CARIBBEAN SEA NORTH OF 13N WEST OF 69W. UPPER
LEVEL ANTICYCLONIC FLOW FROM AN ATLANTIC OCEAN/CARIBBEAN SEA
RIDGE IS ON TOP OF THIS AREA OF PRECIPITATION. IT APPEARS THAT
THIS SYSTEM HAS BECOME BETTER ORGANIZED EVEN THOUGH UPPER LEVEL
WINDS HAVE BECOME LESS FAVORABLE. THIS FEATURE STILL HAS THE
POTENTIAL TO BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY
OR SO AS IT MOVES SLOWLY WEST-NORTHWESTWARD. THE RECONNAISSANCE
FLIGHT SCHEDULED FOR THIS AFTERNOON HAS BEEN CANCELED. ANOTHER
AIR FORCE RESERVE AIRCRAFT IS SCHEDULED TO INVESTIGATE THE
SYSTEM LATE TONIGHT OR SATURDAY IF NECESSARY. IT IS LIKELY
THAT LOCALLY HEAVY RAINFALL MAY AFFECT JAMAICA...THE CAYMAN
ISLANDS...SECTIONS OF CENTRAL AND WESTERN CUBA...AND THE YUCATAN
PENINSULA DURING THE NEXT FEW DAYS...REGARDLESS OF WHETHER OR
NOT THIS SYSTEM BECOMES A TROPICAL CYCLONE. RESIDENTS IN AND
AROUND THE NORTHWESTERN CARIBBEAN SEA SHOULD CLOSELY MONITOR
THE PROGRESS OF THIS DISTURBANCE.

A SURFACE 1010 MB LOW PRESSURE CENTER IS NEAR 12N33W. ITS
MOVEMENT HAS NOT BEEN STEADY DURING THE LAST 24 HOURS...
JUMPING AROUND A BIT FROM MAP TO MAP. NUMEROUS STRONG SHOWERS
AND THUNDERSTORMS NOW ARE FOUND FROM 10.5N TO 12N BETWEEN 31W
AND 34W. OTHER SHOWERS AND THUNDERSTORMS ARE SEEN FROM 7N TO
14N BETWEEN 29W AND 36W. THE THUNDERSTORM ACTIVITY HAS INCREASED
AND BECOME BETTER ORGANIZED...AND UPPER LEVEL WINDS ARE
FAVORABLE FOR A TROPICAL DEPRESSION TO FORM LATER TODAY OR ON
SATURDAY AS THE SYSTEM MOVES SLOWLY NORTHWESTWARD OVER OPEN
WATERS.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROUGH IS ALONG 17N53W 10N51W. ISOLATED
MODERATE SHOWERS AND THUNDERSTORMS ARE WITHIN 90 NM ON EITHER
SIDE OF 10N44W 13N48W 17N52W. THIS PRECIPITATION EASILY MORE
PROBABLY IS RELATED TO UPPER LEVEL DIFFLUENT FLOW IN THE MIDDLE
OF UPPER LEVEL LOW CENTERS NEAR 21N61W AND 25N28W.

A TROPICAL WAVE IS MOVING THROUGH THE MONA PASSAGE ALONG 68W
SOUTH OF 20N MOVING WEST 10 TO 15 KT. THIS WAVE IS MOVING TOWARD
UPPER LEVEL ANTICYCLONIC FLOW...AWAY FROM THE CYCLONIC FLOW WITH
THE ATLANTIC OCEAN-TO-EASTERN CARIBBEAN SEA TROUGH.

...ITCZ...

ITCZ 10N13W 8N20W 11N31W...10N38W 11N47W...10N53W 10N61W. WIDELY
SCATTERED TO SCATTERED MODERATE/ISOLATED STRONG SHOWERS AND
THUNDERSTORMS FROM 2N TO 8N BETWEEN 30W AND 40W. ISOLATED
MODERATE SHOWERS AND LOCALLY STRONG THUNDERSTORMS FROM 3N TO
8N BETWEEN 10W AND 16W.

...DISCUSSION...

THE GULF OF MEXICO...
THE PESKY 1012 MB SURFACE LOW PRESSURE CENTER...WHICH HAS BEEN
SPINNING AROUND IN THE NORTHERN GULF WATERS FOR THE LAST FEW
DAYS...WON'T QUIT AND REMAINS ALIVE...NOW NEAR 26N91.5W. IT IS
POSSIBLE THAT THIS LOW CENTER MAY REACH THE NORTHEASTERN COAST
OF MEXICO BY TOMORROW...IF IT CONTINUES ON ITS CURRENT
WEST-SOUTHWEST TRACK. THIS LOW CENTER HAS BEEN FORECAST TO
DISSIPATE EVERY DAY FOR THE LAST FEW DAYS BUT IT JUST WON'T
GO AWAY. THE CURRENT GFS SURFACE PRESSURE ANALYSIS FORECAST
INITIALIZES THIS LOW CENTER...BUT THEN APPEARS TO GET RID
OF IT IN 24 HOURS. SOME FORM OF A CYCLONIC CIRCULATION CENTER
IS PRESENT IN THE AREA FROM 23N TO 24N BETWEEN 96W AND 97W
BY 01/1200 UTC. IT IS NOT CLEAR WHETHER OR NOT THIS CENTER IS
THE SAME CIRCULATION AS THE PERSISTENT ONE WHICH NOW IS NEAR
26N91.5W. ANY SHOWER ACTIVITY WITH THIS LOW CENTER IS FOUND FROM
24N TO 25N BETWEEN 92W AND 93W. IT IS POSSIBLE THAT SOME RAIN
AND WIND MAY REACH SECTIONS OF THE NORTHEASTERN MEXICO GULF
COAST BY 24 HOURS WITH THIS LOW. A FRONTAL BOUNDARY NOW
STRETCHES FROM SOUTHEASTERN GEORGIA TO SOUTHEASTERN LOUISIANA
TO THE LOWER TEXAS COAST. MIDDLE TO UPPER LEVEL DRY AIR
EVERYWHERE IN THE GULF OF MEXICO IS INHIBITING AREAS OF DEEP
CONVECTIVE ACTIVITY. THIS FRONT HAS BEEN MAINLY STATIONARY...
BUT IT HAS TAKEN ON SOME COLD FRONT CHARACTERISTICS TOWARD THE
SOUTHWESTERN END...NEAR THE TEXAS COAST...ESPECIALLY DURING THE
LAST 3 TO 4 HOURS. UPPER LEVEL ANTICYCLONIC FLOW COVERS THE
NORTHERN HALF OF THE GULF WATERS...WHILE THE SOUTHERN END OF AN
ATLANTIC OCEAN-TO-SOUTHEASTERN GULF OF MEXICO TROUGH CONTINUES
TO STAY ALIVE.

THE CARIBBEAN SEA...
UPPER LEVEL ANTICYCLONIC FLOW COVERS THE CARIBBEAN SEA WEST OF
70W. THE SAME MIDDLE TO UPPER LEVEL ATLANTIC OCEAN-TO-EASTERN
CARIBBEAN SEA TROUGH FROM 24 HOURS AGO IS IN PLACE AT THIS TIME.
AN UPPER LEVEL LOW CENTER IS NEAR 21N61W...AND THIS TROUGH GOES
FROM THE LOW CENTER TO THE NORTHERN VENEZUELA COAST NEAR 10N67W.
WIDELY SCATTERED MODERATE TO ISOLATED SHOWERS AND THUNDERSTORMS
ARE FOUND IN THE ATLANTIC WATERS FROM 19N TO 20N BETWEEN 55W AND
62W...AND FROM 23N TO 27N BETWEEN 57W AND 61W.

THE ATLANTIC OCEAN...
THE SOUTHERN END OF THE U.S.A. EAST COAST TROUGH...SUPPORTING
THE GULF OF MEXICO FRONTAL BOUNDARY...REACHES 32N80W. THE FLOW
GOES AROUND THIS TROUGH AND ENTERS THE ATLANTIC OCEAN SOUTH OF
30N AS NORTHWESTERLY FLOW...MOVING TOWARD THE CYCLONIC FLOW
AROUND THE 21N61W-TO-VENEZUELA TROUGH. ANOTHER TROUGH...POSSIBLY
PART OF THIS 21N61W SYSTEM 24 HOURS AGO...NOW IS ALONG 50W NORTH
OF 30N. AN UPPER LEVEL NORTHWEST-TO-SOUTHEAST ORIENTED RIDGE
IS IN THE MIDDLE OF THE CYCLONIC FLOW WITH THE 21N61W UPPER LOW
AND THE MIDDLE TO UPPER LEVEL LOW CENTER NEAR 25N28W.

$$
MT


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