[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 200547
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU SEP 20 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS CENTERED NEAR 37.1N 31.0W AT 20/0600
UTC OR ABOUT 140 NM S OF FLORES IN THE AZORES MOVING E AT 3 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB. MAXIMUM SUSTAINED
WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED MODERATE
CONVECTION IS FROM 37N-39N BETWEEN 31W-34W. SEE LATEST NHC
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/
WTNT34 AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.

AN UPPER LEVEL LOW IS CENTERED NEAR 31N51W AND SUPPORTS A 1010
MB SURFACE LOW NEARLY COLLOCATED WITH THE UPPER LEVEL LOW NEAR
31N52W. A SURFACE TROUGH EXTENDS SW FROM THE LOW CENTERED TO
25N57W. THE CIRCULATION OF THE LOW HAS GRADUALLY BECOME BETTER
DEFINED OVER THE PAST 24 HOURS AND CONTINUES TO ORGANIZE. THIS
SYSTEM HAS A MEDIUM CHANCE OF BECOMING A SUBTROPICAL CYCLONE
DURING THE NEXT 48 HOURS. SCATTERED MODERATE CONVECTION IS FROM
33N-36N BETWEEN 47W-56W WITH WIDELY SCATTERED MODERATE
CONVECTION ELSEWHERE FROM 28N-33N BETWEEN 51W-58W.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 12N23W TO 20N25W MOVING W AT 10-15
KT. GLOBAL MODEL DATA INDICATES THE WAVE AXIS COINCIDES WITH A
700 MB TROUGH ALONG 26W AND REMAINS WITHIN AN AREA OF MAXIMUM
TOTAL PRECIPITABLE WATER FROM 14N-19N BETWEEN 21W-28W...CENTERED
OVER THE CAPE VERDE ISLANDS. WHILE NO SIGNIFICANT DEEP
CONVECTION IS NOTED ON SATELLITE IMAGERY...ISOLATED SHOWERS ARE
POSSIBLE FROM 14N-22N BETWEEN 18W-31W.

TROPICAL WAVE EXTENDS FROM 10N53W TO 19N48W MOVING W AT 10-15
KT. THE WAVE REMAINS EMBEDDED WITHIN BROAD LOW-LEVEL CYCLONIC
FLOW BETWEEN 47W-55W AND WITHIN AN AREA OF DEEP LAYER MOISTURE
AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE
CONVECTION IS FROM 16N-20N BETWEEN 47W-52W. SCATTERED SHOWERS
ARE ELSEWHERE FROM 11N-21N BETWEEN 47W-56W.

TROPICAL WAVE EXTENDS FROM 13N76W TO 21N76W MOVING W AT 10-15
KT. THE WAVE REMAINS DIFFICULT TO TRACK WITH LOW-LEVEL CYCLONIC
FLOW EVIDENT ACROSS THE CENTRAL CARIBBEAN AND GLOBAL MODEL DATA
INDICATING A WEAK 700 MB TROUGH PROGRESSING WESTWARD ON THE
SOUTHERN PERIPHERY OF A MIDDLE TO UPPER LEVEL RIDGE CENTERED
OVER THE SW NORTH ATLC REGION. TOTAL PRECIPITABLE WATER IMAGERY
INDICATES MAXIMIZED VALUES OVER THE AREA FROM 15N-20N BETWEEN
66W-78W. ISOLATED MODERATE CONVECTION IS FROM 14N-21N BETWEEN
66W-78W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO
06N36W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
06N36W TO 04N51W. ISOLATED MODERATE CONVECTION IS FROM 05N-09N
BETWEEN 10W-28W. WIDELY SCATTERED MODERATE CONVECTION IS FROM
04N-08N BETWEEN 41W-46W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL TROUGH
EXTENDS FROM THE UPPER GREAT LAKES REGION SOUTHWARD TO THE LOWER
MISSISSIPPI RIVER VALLEY AND OVER MUCH OF THE WESTERN GULF. THE
TROUGHING SUPPORTS A COLD FRONT ANALYZED FROM THE CENTRAL
FLORIDA PENINSULA NEAR 28N82W TO 26N85W BECOMING STATIONARY INTO
THE SW GULF ALONG 24N90W TO 19N92W. LOW-LEVEL MOISTURE
CONVERGENCE IN THE VICINITY OF THE FRONT ALONG WITH MIDDLE TO
UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH AXIS IS GENERATING
SCATTERED SHOWERS AND TSTMS EAST OF A LINE FROM THE FLORIDA
PANHANDLE NEAR 30N85W TO 20N97W. THE MOST INTENSE CONVECTION IS
LOCATED SOUTH AND EAST OF THE STATIONARY FRONT FROM 21N-25N
BETWEEN 80W-91W. THE FRONT IS FORECAST TO BECOME MORE AND MORE
DIFFUSE THROUGH FRIDAY AS SURFACE HIGH PRESSURE REMAINS ANCHORED
OVER THE SE CONUS.

CARIBBEAN SEA...
WHILE A MIDDLE TO UPPER LEVEL TROUGH IS OVER THE GULF OF
MEXICO...AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED
NORTH OF EASTERN CUBA NEAR 23N74W AND PROVIDES INFLUENCE ACROSS
MUCH OF THE CARIBBEAN. WEST OF THE RIDGE AXIS ALONG 73W...MIDDLE
TO UPPER LEVEL DIFFLUENCE REMAINS MAXIMIZED BETWEEN THE TWO
FEATURES WITH A WEAK UPPER LEVEL LOW CENTERED NEAR 20N82W
EMBEDDED WITHIN THE RIDGE AND MOVING NORTHWESTWARD INTO THE
LARGER MEAN TROUGHING OVER THE GULF OF MEXICO. SCATTERED SHOWERS
AND TSTMS ARE OCCURRING IN RESPONSE N OF 19N BETWEEN 78W-87W...
INCLUDING INLAND PORTIONS OF WESTERN CUBA. FARTHER EAST...
BENEATH THE HEART OF THE UPPER LEVEL ANTICYCLONE...A TROPICAL
WAVE IS ALONG 77W AND WITH AN ALREADY OVERALL DIFFLUENT
ENVIRONMENT IN PLACE OVER THE CENTRAL CARIBBEAN...ISOLATED
SHOWERS AND TSTMS ARE OCCURRING FROM 14N-21N BETWEEN 66W-78W.
FINALLY EAST OF THE UPPER LEVEL RIDGE AXIS...OUTSIDE OF THE
ISOLATED CONVECTION ASSOCIATED WITH THE TROPICAL WAVE...
CONDITIONS ARE EXPECTED TO IMPROVE AS MOSTLY CLEAR SKIES AND
NORTHERLY WINDS ALOFT PROVIDE AN OVERALL STABLE ENVIRONMENT
ACROSS THE LESSER ANTILLES.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH IS ACROSS THE EASTERN CONUS AND
SUPPORTS A COLD FRONT ANALYZED FROM 32N76W TO THE CENTRAL
FLORIDA PENINSULA NEAR CAPE CANAVERAL. WATER VAPOR IMAGERY
INDICATES DEEP LAYERED MOISTURE ADVECTION FROM THE WESTERN
CARIBBEAN SEA NORTH-NORTHEASTWARD TO THE CANADIAN MARITIMES OF
NOVA SCOTIA AND NEWFOUNDLAND THAT SUPPORTS SCATTERED SHOWERS AND
ISOLATED TSTMS MOSTLY WEST OF 75W. THE REMAINDER OF THE SW NORTH
ATLC IS UNDER THE INFLUENCE OF A WEAK SURFACE RIDGE WITH AXIS
EXTENDING FROM BERMUDA NEAR 32N65W TO THE CENTRAL BAHAMAS NEAR
25N75W. FARTHER EAST OVER THE CENTRAL ATLC...THE SPECIAL
FEATURES LOW CONTINUES TO INFLUENCE THE AREA N OF 20N BETWEEN
45W-60W. ALSO...CYCLONIC WINDS AND CONVECTION ASSOCIATED WITH
TROPICAL STORM NADINE ARE LOCATED N OF 30N BETWEEN 20W-38W
IMPACTING THE AZORES THROUGH THE OVERNIGHT HOURS. ELSEWHERE THE
REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A
SURFACE RIDGE ANCHORED BY A 1019 MB HIGH CENTERED NEAR 25N37W.

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

$$
HUFFMAN



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