[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 251042
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE SEP 25 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION TWELVE HAS BEEN UPGRADED TO TROPICAL STORM
KAREN IN THE EAST ATLANTIC...AND IS NO IMMEDIATE THREAT TO LAND
AREAS. AT 25/0900 UTC T.S. KAREN WAS NEAR 10.4N 38.0W OR ABOUT
1360 NM E OF THE WINDWARD ISLANDS...MOVING W-NW AT 14
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM
SUSTAINED WINDS ARE 35 KT WITH GUSTS TO 45 KT. SEE LATEST NHC
FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
AND THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE
DETAILS. KAREN IS A LARGE SYSTEM WITH SCATTERED
MODERATE/ISOLATED STRONG CONVECTION OVER MUCH OF THE AREA FROM
6N-15N BETWEEN 33W-43W. SOME ADDITIONAL STRENGTHENING IS
FORECAST OVER THE NEXT DAY OR SO AS KAREN CONTINUES ON A WNW
TRACK S OF A MID LEVEL RIDGE.

A 1009 MB LOW IS OVER THE SW GULF OF MEXICO NEAR 22N94W. A SFC
TROUGH EXTENDS THROUGH THE LOW FROM NEAR BROWNSVILLE TO THE
YUCATAN ALONG 26N97W 22N94W 20N92W. DISORGANIZED SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS ARE FROM 21N-27N BETWEEN
90W-96W. UPPER LEVEL WINDS ARE BECOMING MORE FAVORABLE...AND
THIS SYSTEM COULD BECOME A TROPICAL DEPRESSION OVER THE NEXT DAY
OR SO AS IT DRIFTS SLOWLY AND ERRATICALLY.  AN AIR FORCE RESERVE
HURRICANE HUNTER AIRCRAFT IS SCHEDULE TO INVESTIGATE THE SYSTEM
LATER TODAY...IF NECESSARY.

A 1011 MB LOW PRESSURE AREA IS NEAR 15N62W ASSOCIATED WITH A
TROPICAL WAVE MOVING THROUGH THE LESSER ANTILLES. SHOWER
ACTIVITY ASSOCIATED WITH THIS SYSTEM HAS BECOME LESS ORGANIZED
OVERNIGHT...AND UPPER-LEVEL WINDS ARE BECOMING LESS FAVORABLE
FOR DEVELOPMENT OF A TROPICAL DEPRESSION. HOWEVER...THE SYSTEM
IS EXPECTED TO MOVE NORTHWESTWARD AND BRING SQUALLY WEATHER TO
PORTIONS OF THE LEEWARD ISLANDS TODAY...AND TO THE VIRGIN
ISLANDS AND PUERTO RICO BY WEDNESDAY. SATELLITE IMAGERY AND
METEO-FRANCE RADAR DATA FROM MARTINIQUE DEPICT ISOLATED SHOWERS
AND TSTMS FROM 13N-21N BETWEEN 58W-65W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 62W AFFECTING THE LESSER ANTILLES. SEE
SPECIAL FEATURES ABOVE FOR MORE DETAILS.

A WEAK TROPICAL WAVE IS ALONG 90W S OF 18N MOVING W 10-15 KT.
WAVE REMAINS DIFFICULT TO LOCATE WITH ITS POSITION BASED MAINLY
ON CONTINUITY FROM PREVIOUS ANALYSES. SCATTERED MODERATE
CONVECTION IS MOSTLY INLAND OVER CENTRAL AMERICA S OF 17N
BETWEEN 88W-92W. FOR FUTURE INFO ON THIS WAVE PLEASE REFER TO
PACIFIC DISCUSSION UNDER MIATWDEP.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 7N25W 12N35W 7N50W 13N59W.
BESIDES THE ACTIVITY ASSOCIATED WITH THE SPECIAL
FEATURES/TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS ALONG
AND JUST OFF THE COAST OF AFRICA FROM 6N-13N BETWEEN 12W-18W.
SCATTERED MODERATE/ISOLATED STRONG IS WITHIN 150NM EITHER SIDE
OF THE AXIS BETWEEN 18W-27W.

DISCUSSION...

GULF OF MEXICO...
THE MAIN WEATHER FEATURE ACROSS THE GULF IS THE AREA OF LOW
PRES LOCATED OVER THE SW GULF WHICH COULD BECOME A TROPICAL
CYCLONE OVER THE NEXT COUPLE OF DAYS. SEE SPECIAL FEATURES
ABOVE. ABUNDANT DEEP LAYER MOISTURE IS OVER THE BASIN BETWEEN
87W-95W. THIS IS ASSOCIATED WITH THE SPECIAL FEATURE IN THE SW
GULF IN ADDITION TO LIFT AHEAD OF AN UPPER TROUGH OVER THE FAR
WRN GULF. AN UPPER RIDGE CONTINUES TO DOMINATE MUCH OF THE
CENTRAL GULF...WITH THE AXIS NOW EXTENDING NE BETWEEN THE BAY OF
CAMPECHE TO SE LOUISIANA. VERY DRY MID TO UPPER AIR IS BEING
ADVECTED INTO THE NE GULF AROUND AN UPPER TROUGH EXTENDING INTO
THE AREA FROM THE WRN ATLC...WHILE MOISTURE AND SCATTERED SHOWER
ACTIVITY PERSISTS OVER THE SE GULF...FL KEYS...AND STRAITS OF
FLORIDA. ELSEWHERE AT THE SFC...RIDGING EXTENDS INTO THE NE GULF
AROUND HIGH PRES CENTERED NEAR MID ATLANTIC COAST. RIDGING WILL
PERSIST OVER THE NRN GULF THROUGH WED WHILE LOW PRES MEANDERS IN
THE SW PORTION.

CARIBBEAN SEA...
THE MAIN WEATHER FEATURE IN THE CARIBBEAN IS ASSOCIATED WITH THE
TROPICAL WAVE AND ASSOCIATED LOW PRESSURE AREA MOVING THROUGH
THE LESSER ANTILLES AS DESCRIBED ABOVE. OTHERWISE THE BASIN IS
FAIRLY TRANQUIL. AN UPPER RIDGE/TROUGH/RIDGE PATTERN CONTINUES
TO DOMINATE. DEEP MOISTURE AND A FEW ISOLATED TSTMS ARE
AFFECTING THE FAR NW PORTION N OF 18N W OF 75W. THIS ACTIVITY
SEEMS MOSTLY ASSOCIATED WITH DIFFLUENT FLOW ALOFT OVER THE AREA.
UPPER SLY FLOW AHEAD OF AN UPPER TROUGH IS ADVECTING HIGH
CLOUDS/MOISTURE NWD BETWEEN 66W-78W. ISOLATED SHOWER ACTIVITY
ALSO ANTICIPATED IN THIS REGION...WITH LIGHTNING DATA SUPPORTING
A FEW TSTMS CURRENTLY JUST S OF THE MONA PASSAGE...WHERE
SHORTWAVE IR IMAGERY SHOWS A SMALL AREA OF LOW LEVEL CYCLONIC
TURNING. TRADES REMAIN LIGHT TO MODERATE ACROSS THE BASIN...BUT
WINDS/SEAS COULD BE HIGHER AT TIMES IN SQUALLS NEAR THE LOW/WAVE
MOVING THROUGH THE LESSER ANTILLES.

ATLANTIC OCEAN...
MOST OF THE ACTIVE SFC FEATURES ARE DISCUSSED IN THE SPECIAL
FEATURES SECTION ABOVE. ELSEWHERE AT THE SFC...WEAK HIGH PRES
RIDGING AN ELY FLOW CONTROL THE W ATLC. A 1020 MB SFC HIGH NEAR
30N55W AND A PAIR OF WEAK TROUGHS DOMINATE THE CENTRAL ATLC
AREA. THE FIRST OF THE TROUGHS IS ALONG 66W N OF 23N...WHICH IS
GENERATING SCATTERED SHOWERS/TSTMS FROM 25N-29N BETWEEN 60W-67W.
THE SECOND TROUGH ENTERS THE AREA NEAR 32N41W AND CONTINUES SW
TO 26N56W. SCATTERED SHOWERS ARE GENERALLY WITHIN 90 NM EITHER
SIDE OF THIS TROUGH. MODERATE RIDGING TAKES OVER IN THE E ATLC
ANCHORED BY A 1031 MB HIGH LOCATED WELL NE OF THE AZORES. THIS
PATTERN IS PRODUCING MODERATE TRADES IN THE E ATLC...EXCEPT
STRONGER NEAR THE NW COAST OF AFRICA WHERE THE PRES GRADIENT
TIGHTENS. THE WEAK LOW THAT WAS PREVIOUSLY NEAR 15N49W IS NOW
ANALYZED AS A SMALL TROUGH ALONG 50W FROM 12N-19N...BASED ON
RECENT ASCAT AND QUIKSCAT PASSES.

IN THE MID AND UPPER LEVELS...A BROAD UPPER LOW NEAR 29N72W HAS
TROUGHING OVER MUCH OF THE WRN ATLC. THE UPPER TROUGH IS
SUPPORTING NUMEROUS SHOWERS AND TSTMS OVER THE STRAITS OF
FLORIDA...WRN BAHAMAS...AND NEAR THE COAST OF SE FLORIDA S OF
27N W OF 76W. THERE ARE NO SIGNS OF ORGANIZATION OF THIS
ACTIVITY...AND ANY DEVELOPMENT SHOULD BE SLOW TO OCCUR. VERY DRY
AIR IS OVER THE REMAINDER OF THE WRN ATLC N OF 27N W OF 74W. WSW
FLOW TO THE S OF AND AHEAD OF THE UPPER LOW DOMINATES THE
CENTRAL ATLC N OF 20N. AN AMPLIFIED UPPER RIDGE IS SEEN E OF THE
TROUGHING EXTENDING NE FROM AN UPPER HIGH SITUATED NEAR 15N60W
TO BEYOND 32N34W. A LARGE UPPER LOW IS LOCATED E OF THE RIDGE W
OF THE MADEIRA ISLANDS NEAR 31N21W. THIS APPEARS TO BE PRODUCING
ISOLATED SHOWER ACTIVITY N OF 29N BETWEEN 19W-23W...BUT IS ONLY
GENERATING PATCHES OF HIGH CLOUDINESS ELSEWHERE.

$$
MW




This weather bulletin was brought to you by:
www.nashvilleweather.net