[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 190550
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED SEP 19 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 36.2N 32.1W AT 19/0600
UTC OR ABOUT 195 NM SSW OF FLORES IN THE AZORES MOVING NNE AT 6
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 993 MB. MAXIMUM
SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED
MODERATE CONVECTION IS FROM 36N-41N BETWEEN 28W-36W. 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.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 07N48W TO 18N41W MOVING W AT 10-15
KT. THE WAVE REMAINS EMBEDDED WITHIN BROAD CYCLONIC FLOW FROM
08N-17N BETWEEN 41W-50W AND WITHIN A SURGE OF DEEP LAYER
MOISTURE AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED
MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF A LINE FROM
10N50W TO 18N44W.

TROPICAL WAVE EXTENDS FROM 12N68W TO 19N65W MOVING W AT 10 KT.
THE WAVE REMAINS DIFFICULT TO TRACK WITH LOW-LEVEL CYCLONIC FLOW
EVIDENT ACROSS THE LESSER ANTILLES ON INFRARED SATELLITE
IMAGERY...HOWEVER MOST OF THE ACTIVE CONVECTION IS LOCATED
FARTHER W-NW ACROSS THE NORTH-CENTRAL CARIBBEAN SEA AND PORTIONS
OF PUERTO RICO AND HISPANIOLA. TOTAL PRECIPITABLE WATER IMAGERY
INDICATES MAXIMIZED VALUES OVER THE AREA FROM 14N-19N BETWEEN
60W-74W. ISOLATED MODERATE CONVECTION IS FROM 15N-21N BETWEEN
64W-75W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 15N17W TO
05N29W TO 05N36W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 05N36W TO 08N44W THEN RESUMES AT 08N51W TO 08N59W.
ISOLATED MODERATE CONVECTION IS FROM 04N-08N BETWEEN 25W-44W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL TROUGH
EXTENDS FROM THE UPPER GREAT LAKES REGION S-SW TO THE LOWER
MISSISSIPPI RIVER VALLEY AND OVER PORTIONS OF THE NW GULF. THE
TROUGHING SUPPORTS A COLD FRONT ANALYZED AT 19/0300 UTC FROM
NORTHERN FLORIDA NEAR 31N83W TO 25N88W BECOMING STATIONARY INTO
THE SW GULF TO NEAR 19N93W. 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 ALONG AND EAST OF THE FRONT WITH THE MOST
INTENSE CONVECTION OCCURRING OVER THE FLORIDA STRAITS...YUCATAN
CHANNEL...AND PORTIONS OF THE YUCATAN PENINSULA. THE FRONT IS
FORECAST TO BECOME STATIONARY DRAPED FROM NORTHERN FLORIDA TO
25N90W WEDNESDAY INTO THURSDAY AND EVENTUALLY BECOME ABSORBED
INTO A SECONDARY COLD FRONT CURRENTLY EXTENDING FROM THE WESTERN
FLORIDA PANHANDLE TO THE TEXAS AND LOUISIANA BORDER. THE FRONT
IS EXPECTED TO GRADUALLY DISSIPATE OVER THE EASTERN GULF WATERS
AND LINGER ACROSS THE FLORIDA PENINSULA THURSDAY INTO FRIDAY.

CARIBBEAN SEA...
AN APPROACHING MIDDLE TO UPPER LEVEL TROUGH IS OVER THE GULF OF
MEXICO THIS EVENING AND THE ASSOCIATED DIFFLUENCE EAST OF THE
TROUGH AXIS IS GENERATING SCATTERED SHOWERS AND TSTMS OVER
PORTIONS OF THE NW CARIBBEAN NORTH OF A LINE FROM 22N80W TO
17N88W...INCLUDING THE YUCATAN CHANNEL...YUCATAN PENINSULA...AND
WESTERN CUBA. ELSEWHERE OVER THE WESTERN CARIBBEAN...MOSTLY
CLEAR SKIES PREVAIL W OF 76W AS AN INVERTED UPPER LEVEL TROUGH
WITH AXIS ALONG 80W REMAINS EMBEDDED WITHIN DRY AIR ALOFT AS
NOTED ON WATER VAPOR IMAGERY. TO THE EAST OF THIS UPPER LEVEL
TROUGH AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED NORTH
OF HISPANIOLA NEAR 21N69W. WHILE PROVIDING AN OVERALL DIFFLUENT
ATMOSPHERE BENEATH THIS FEATURE...A WEAK 850 MB TO 700 MB TROUGH
IS LOCATED BETWEEN THE TROPICAL WAVE ALONG 68W AND 76W. WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING FROM 15N-20N
BETWEEN 64W-75W. THE PRESENCE OF THE TROPICAL WAVE IS LIKELY
ENHANCING LOW-LEVEL MOISTURE CONVERGENCE AND WILL CONTINUE TO
PROVIDE A HIGHER LIKELIHOOD OF PRECIPITATION THROUGH THE
OVERNIGHT HOURS INTO WEDNESDAY FOR PUERTO RICO AND HISPANIOLA.

ATLANTIC OCEAN...
WITH THE APPROACH OF AN MIDDLE TO UPPER LEVEL TROUGH ACROSS THE
SE CONUS...THE SW NORTH ATLC IS UNDER THE INFLUENCE OF MAXIMIZED
DIFFLUENCE ALOFT AHEAD OF A FRONTAL BOUNDARY EXTENDING FROM
NORTHERN FLORIDA INTO THE SOUTH-CENTRAL GULF OF MEXICO.
SCATTERED SHOWERS AND TSTMS ARE OCCURRING FROM 29N-33N BETWEEN
73W-76W...FROM 25N-29N W OF 77W...AND W OF 80W...INCLUDING THE
FLORIDA STRAITS. SE OF THIS AREA...AN UPPER LEVEL ANTICYCLONIC
CIRCULATION IS CENTERED N OF HISPANIOLA NEAR 21N69W AND EXTENDS
A RIDGE AXIS NORTHWARD TO ANOTHER ANTICYCLONIC CIRCULATION NEAR
34N68W. WATER VAPOR IMAGERY INDICATES MOST MIDDLE TO UPPER LEVEL
MOISTURE IS CENTERED OVER HISPANIOLA WITH ISOLATED SHOWERS AND
TSTMS OCCURRING FROM 18N-23N BETWEEN 65W-76W. FARTHER EAST...AN
UPPER LEVEL LOW IS CENTERED NEAR 33N53W AND EXTENDS A TROUGH
AXIS SOUTHWARD TO A BASE NEAR 22N57W. THIS TROUGHING SUPPORTS A
1014 SURFACE LOW CENTERED NEAR 31N50W. A SURFACE TROUGH EXTENDS
SW FROM THE LOW TO 25N55W WITH SCATTERED SHOWERS AND TSTMS
OCCURRING OVER THE AREA FROM 26N-33N BETWEEN 45W-55W. ASIDE FROM
THE CYCLONIC WINDS ASSOCIATED WITH TROPICAL STORM NADINE N OF
28N BETWEEN 24W-44W...THE REMAINDER OF THE EASTERN AND CENTRAL
ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A
1019 MB HIGH CENTERED NEAR 29N20W WITH A RIDGE AXIS EXTENDING SW
FROM THE HIGH CENTER TO 22N40W.

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

$$
HUFFMAN




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