[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 092344
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 09 2012

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2245 UTC.

...SPECIAL FEATURES...

HURRICANE MICHAEL IS CENTERED NEAR 33.6N 423.8W AT 09/2100 UTC
OR ABOUT 860 NM WSW OF THE AZORES MOVING W AT 04 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 978 MB. MAXIMUM SUSTAINED WIND SPEED
IS 80 KT WITH GUSTS TO 100 KT. SCATTERED MODERATE CONVECTION IS
FROM 31N-34N BETWEEN 41W-45W. SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS.

TROPICAL STORM LESLIE IS CENTERED NEAR 33.8N 62.0W AT 10/0000
UTC OR ABOUT 165 NM ENE OF BERMUDA MOVING N AT 12 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED WIND SPEED
IS 50 KT WITH GUSTS TO 60 KT. NUMEROUS MODERATE/SCATTERED STRONG
CONVECTION IS FROM 31N-33N BETWEEN 61W-65W...FROM 33N-35N
BETWEEN 60W-62W...AND FROM 33N-34N BETWEEN 63W-65W. SCATTERED
MODERATE CONVECTION IS ELSEWHERE FROM 34N-38N BETWEEN 60W-65W.
SEE LATEST NHC INTERMEDIATE PUBLIC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT2/WTNT32 AND THE FULL
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS.

TROPICAL WAVE EXTENDS FROM 23N31W TO A 1009 MB SURFACE LOW AT
13N32W. THE WAVE/LOW ARE WITHIN A LARGE AREA OF DEEP MOISTURE
WITH MAXIMUM VALUES NEAR THE WAVE/LOW CENTER EVIDENT IN TOTAL
PRECIPITABLE WATER IMAGERY. MID/LOW-LEVEL CYCLONIC FLOW IS
EVIDENT IN SATELLITE IMAGERY AND SATELLITE DERIVED WINDS.
SCATTERED MODERATE/STRONG CONVECTION IS MAINLY WEST OF THE AXIS
FROM 15N-19N BETWEEN 31W-35W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 10N-12N BETWEEN 28W-36W. ENVIRONMENTAL
CONDITIONS APPEAR CONDUCIVE FOR GRADUAL DEVELOPMENT AS THE
LOW/WAVE MOVE WESTWARD AT ABOUT 20 KT.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
SENEGAL AT 15N17W CONTINUING ACROSS ATLC WATERS TO A SURFACE LOW
ATTACHED TO A TROPICAL WAVE AT 13N32W. IT THEN CONTINUES ALONG
10N42W 10N52W. THE ITCZ BEGINS AT 10N52W TO 11N61W. A NEGATIVELY
TILTED SURFACE TROUGH IS WEST OF THE TROPICAL WAVE ALONG 18N42W
TO 13N36W. IT ALSO ALIGNS WITH A SURGE OF DEEP LAYER MOISTURE
AND IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION
WITHIN 100 NM WEST OF THE AXIS. THE TROUGH WILL REMAIN TILTED
AND IS MOVING SLOWER THAN THE WAVE TO ITS EAST. THIS WILL
EVENTUALLY CAUSE THE TWO FEATURES TO MERGE LATER IN THE WEEK. NO
DEEP CONVECTION IS NOTED ELSEWHERE ALONG THE MONSOON TROUGH/ITCZ.

...DISCUSSION...

GULF OF MEXICO...
A WEAK COLD FRONT CONTINUES TO MOVE THROUGH THE GULF OF MEXICO
CURRENTLY EXTENDING FROM NORTHERN FLORIDA NEAR 29N82W TO SOUTH
OF THE SOUTHERN TIP OF TEXAS AT 23N98W CONTINUING INTO MEXICO TO
26N103W...AS OF 2100 UTC. ISOLATED SHOWERS/THUNDERSTORMS EXTEND
UP TO 150 NM SE OF THE AXIS AND WITHIN 90 NM NW OR BEHIND THE
FRONT. THE FRONT IS SUPPORTED BY A LONGWAVE UPPER TROUGH OVER
THE EASTERN CONUS. STRONG DRY AIR AND SUBSIDENCE ARE ALSO BEHIND
THE FRONT...WHICH IS LEAVING THE NORTHERN GULF COAST UNDER VERY
CLEAR SKIES. THE SOUTHERN GULF IS ALSO EXPERIENCING MOSTLY FAIR
CONDITIONS DUE TO DRY AIR ALOFT AROUND A WEAK UPPER RIDGE
EXTENDING FROM THE SW GULF TO CENTRAL FLORIDA. IT SUPPORTS WEAK
SURFACE RIDGING CROSS THIS AREA AND VERY LIGHT WINDS. WINDS ARE
HIGHER IMMEDIATELY AHEAD AND BEHIND THE FRONT. THE UPPER TROUGH
SUPPORTING THE FRONT IS EXPECTED TO MOVE MAINLY EAST...BUT NOT
MUCH FARTHER SOUTH. THE FRONT IS EXPECTED TO SLOWLY DRIFT SOUTH
BEFORE BECOMING STATIONARY ACROSS CENTRAL FLORIDA AND THEN WILL
GRADUALLY DISSIPATE OVER THE NEXT COUPLE OF DAYS. ISOLATED
SHOWERS/THUNDERSTORMS WILL BE LIKELY NEAR THE AXIS.

CARIBBEAN SEA...
A SIMILAR PATTERN AS YESTERDAY RESIDES ACROSS THE CARIBBEAN WITH
MOSTLY CLEAR SKIES AND FAIR CONDITIONS COVERING A GOOD PORTION
OF THE BASIN. THIS IS THE RESULT OF DRY AIR ALOFT AROUND AN
UPPER LEVEL RIDGE IN THE W ATLC. HOWEVER...AN INVERTED UPPER
TROUGH OVER THE NW CARIBBEAN IS HELPING PRODUCE SOME
SHOWERS/THUNDERSTORMS ACROSS HONDURAS AND GUATEMALA. SIMILAR
ACTIVITY IS ALSO ACROSS NICARAGUA AND COSTA RICA...BUT SOME OF
THIS ACTIVITY MAY BE MORE ASSOCIATED WITH THE MONSOON TROUGH
EXTENDING THROUGH COAST RICA AND PANAMA TO A 1007 MB SURFACE LOW
OVER NORTHERN COLOMBIA. TRADEWIND FLOW OF 15-20 KT IS ACROSS THE
MAJORITY OF THE BASIN WITH LIGHTER WINDS IN BOTH THE FAR EASTERN
AND FAR WESTERN CARIBBEAN. EXPECT LITTLE CHANGE OVER THE NEXT 24
HOURS.

ATLANTIC OCEAN...
THE COLD FRONT ACROSS THE GULF OF MEXICO IS BEGINNING TO EMERGE
OVER THE W ATLC WATERS FROM A FRONTAL LOW AT 33N77W TO NE
FLORIDA AT 30N81W. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 175
NM SE...AND 90 NM NW OF THE AXIS. THE FRONT IS SUPPORTED BY A
LONGWAVE UPPER TROUGH OVER THE EASTERN CONUS. AN UPPER LEVEL
RIDGE COVERS THE REMAINDER OF THE WEST ATLC ACCOMPANIED BY DRY
AIR ALOFT. IT SUPPORTS WEAK SURFACE RIDGING ACROSS THE CENTRAL
ATLC INTO THE W ATLC S OF THE CIRCULATION OF LESLIE. A WEAK SPOT
HIGH IS AT 20N61W. FAIR WEATHER IS PRESENT AROUND THE SURFACE
RIDGE. TO THE N...TROPICAL STORM LESLIE IS MOVING PAST BERMUDA
WITH HURRICANE MICHAEL WELL TO THE EAST. SEE THE SPECIAL
FEATURES SECTION FOR MORE DETAILS ON THESE STORMS. A NARROW
UPPER LEVEL TROUGH EXTENDS FROM SOUTH OF MICHAEL TOWARDS THE
LESSER ANTILLES...BUT IS NOT CAUSING ANY ACTIVE WEATHER. IT IS
SQUISHED BETWEEN THE UPPER RIDGE TO THE WEST OVER THE WEST
ATLC...AND AN UPPER LEVEL RIDGE COVERING THE EAST ATLC CENTERED
NEAR 23N32W. THE UPPER RIDGE SUPPORTS A 1023 MB SURFACE HIGH AT
31N27W...WHICH IS PROVIDING FAIR WEATHER BESIDES NEAR A TROPICAL
WAVE AND TROUGH IN THE TROPICAL ATLC. THE LAST VISIBLE SATELLITE
IMAGERY OF THE DAY ALONG WITH GOES-R ENHANCEMENT IMAGERY
INDICATES AN AREA OF AFRICAN DUST HAS EMERGED OFF THE COAST OF
AFRICA BEHIND THE TROPICAL WAVE. THE DUST EXTENDS TO ABOUT 30W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON





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