[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211157
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI SEP 21 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS CENTERED NEAR 34.9N 27.5W AT 21/1200
UTC OR ABOUT 190 NM S OF THE AZORES MOVING S AT 6 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 981 MB. MAXIMUM SUSTAINED WIND SPEED
IS 55 KT WITH GUSTS TO 65 KT. SCATTERED MODERATE CONVECTION IS
FROM 32N-36N BETWEEN 26W-33W. 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 32N56W AND SUPPORTS A 1006
MB SURFACE LOW COLLOCATED WITH THE UPPER LEVEL LOW. LATEST
SATELLITE IMAGERY INDICATES THE CIRCULATION OF THE LOW PRESSURE
AREA REMAINS BROAD AS IT CONTINUES TO ORGANIZE CONVECTIVELY.
THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A SUBTROPICAL
CYCLONE DURING THE NEXT 48 HOURS. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 27N-37N BETWEEN 52W-59W.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 11N38W TO 18N36W MOVING W AT 15 KT.
GLOBAL MODEL DATA INDICATES THE WAVE AXIS COINCIDES WITH A 700
MB TROUGH ALONG 37W AND REMAINS WITHIN AN AREA OF MAXIMUM TOTAL
PRECIPITABLE WATER FROM 14N-18N BETWEEN 30W-41W. ISOLATED
MODERATE CONVECTION IS FROM 13N-17N BETWEEN 37W-43W.

TROPICAL WAVE EXTENDS FROM 13N65W TO 20N60W MOVING W AT 15 KT.
THE WAVE CONTINUES TO STRETCH IN A NE TO SW ORIENTATION DUE TO
AN UPPER LEVEL LOW AND TROUGH ACROSS THE EASTERN CARIBBEAN SEA
AND CENTRAL ATLC BETWEEN 55W-68W. THIS AREA IS RICH IN DEEP
LAYER MOISTURE AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY.
ISOLATED MODERATE CONVECTION IS FROM 18N-21N BETWEEN 56W-60W.

TROPICAL WAVE EXTENDS FROM 15N84W TO 23N82W MOVING W AT 10-15
KT. OVER THE PAST 24 HOURS...THE WAVE HAS MOVED INTO CLOSER
PROXIMITY OF AN UPPER LEVEL TROUGH ACROSS THE GULF OF MEXICO AND
HAS INCREASED DEEP LAYER MOISTURE ACROSS THE NW CARIBBEAN SEA
AND PORTIONS OF THE THE SE GULF OF MEXICO PER TOTAL PRECIPITABLE
WATER IMAGERY. LOW-LEVEL CYCLONIC FLOW IS EVIDENT AND GLOBAL
MODEL DATA INDICATES A WEAK 700 MB TROUGH ALONG 84W ON THE
SOUTHERN PERIPHERY OF A MID-LEVEL RIDGE CENTERED OVER THE SW
NORTH ATLC REGION. SCATTERED MODERATE CONVECTION IS FROM 16N-23N
BETWEEN 78W-86W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 11N15W TO
08N27W TO 06N40W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 06N40W TO 04N51W. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 05N-08N BETWEEN 11W-21W...AND FROM 04N-08N
BETWEEN 25W-34W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL TROUGH
EXTENDS FROM THE GREAT LAKES REGION SOUTHWARD TO THE SE CONUS
AND OVER MUCH OF THE GULF THIS MORNING. THE TROUGHING SUPPORTS A
DISSIPATING STATIONARY FRONT ANALYZED ACROSS THE CENTRAL FLORIDA
PENINSULA TO NEAR THE TAMPA BAY REGION. WHILE THE SURFACE FRONT
HAS DISSIPATED OVER THE EASTERN GULF...LOW-LEVEL MOISTURE
CONTENT REMAINS ELEVATED S OF 28N E OF A SURFACE TROUGH ANALYZED
FROM 28N93W TO 19N92W. WIDELY SCATTERED SHOWERS AND ISOLATED
TSTMS ARE OCCURRING MAINLY S OF 30N E OF 93W...WITH THE MOST
INTENSE ACTIVITY LOCATED ACROSS THE FLORIDA STRAITS AND
SOUTH-CENTRAL GULF S OF 25N BETWEEN 87W-91W. MOST OF THIS
CONVECTION IS LIKELY ENHANCED DUE TO MAXIMIZED MIDDLE TO UPPER
LEVEL DIFFLUENCE EAST OF THE UPPER LEVEL TROUGH AXIS WHICH LIES
ALONG 92W. WATER VAPOR IMAGERY INDICATES THAT DRY AIR ALOFT N OF
21N W OF 92W IS PREVENTING THE DEVELOPMENT OF ANY SIGNIFICANT
DEEP CONVECTION. LOOKING TO THE WEEKEND...THE SURFACE TROUGH IS
EXPECTED TO REMAIN ACROSS PORTIONS OF THE WESTERN GULF WITH
SURFACE RIDGING ESTABLISHING ITSELF OVER THE NORTHERN GULF
WATERS WITH AXIS ALONG
CARIBBEAN SEA...
WHILE A MIDDLE TO UPPER LEVEL TROUGH IS OVER THE GULF OF
MEXICO...AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED
OVER EASTERN CUBA NEAR 21N77W AND PROVIDES INFLUENCE SOUTHWARD
ACROSS MUCH OF THE WESTERN CARIBBEAN. WHILE MOSTLY FAIR
CONDITIONS ARE FOUND ACROSS PORTIONS OF THE CENTRAL CARIBBEAN
BETWEEN 68W-76W...MIDDLE TO UPPER LEVEL DIFFLUENCE IS MAXIMIZED
BETWEEN THE TROUGH AND RIDGE GENERATING SCATTERED SHOWERS AND
TSTMS N OF 16N W OF 76W. ADDING THE LOW-LEVEL MOISTURE
CONVERGENCE ASSOCIATED WITH THE TROPICAL WAVE ALONG 84W...
CONVECTION REMAINS ENHANCED OVER THE NW CARIBBEAN FROM 16N-22N
BETWEEN 78W-87W. FINALLY...EAST OF THE UPPER LEVEL
ANTICYCLONE...AN UPPER LEVEL LOW IS CENTERED NEAR 14N60W AND IS
PROVIDING THE EASTERN CARIBBEAN WITH DRIER AND MORE STABLE AIR
ALOFT E OF 74W. HOWEVER...A FEW ISOLATED LOW-TOPPED SHOWERS ARE
OCCURRING SOUTH OF PUERTO RICO FROM 14N-18N BETWEEN 64W-70W.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH IS ACROSS THE EASTERN CONUS AND
SUPPORTS A DISSIPATING STATIONARY FRONT ANALYZED FROM 32N73W TO
30N76W TO THE CENTRAL FLORIDA PENINSULA NEAR 29N81W. WATER VAPOR
IMAGERY INDICATES DEEP LAYERED MOISTURE ADVECTION FROM THE
NORTHWESTERN CARIBBEAN SEA NORTH-NORTHEASTWARD TO THE CANADIAN
MARITIMES OF NOVA SCOTIA AND NEWFOUNDLAND THAT SUPPORTS
SCATTERED SHOWERS AND WIDELY SCATTERED TSTMS WEST OF 74W.
FARTHER EAST OVER THE CENTRAL ATLC...THE SPECIAL FEATURES LOW
CONTINUES TO INFLUENCE THE AREA N OF 20N BETWEEN 46W-65W. WIDELY
SCATTERED SHOWERS AND TSTMS ARE OCCURRING WELL SE OF THE SPECIAL
FEATURES LOW FROM 21N-29N BETWEEN 45W-55W. ALSO...CYCLONIC WINDS
AND CONVECTION ASSOCIATED WITH TROPICAL STORM NADINE ARE LOCATED
N OF 27N BETWEEN 16W-35W IMPACTING THE AZORES. ELSEWHERE THE
REMAINDER OF THE CENTRAL ATLC IS UNDER THE INFLUENCE OF A
SURFACE RIDGE WITH AXIS EXTENDING INTO THE DISCUSSION AREA ALONG
42W.

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

$$
HUFFMAN*/



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