[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 170546
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON SEP 17 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 31.4N 38.1W AT 17/0300
UTC OR ABOUT 675 NM WSW OF THE AZORES MOVING ENE AT 16 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. MAXIMUM SUSTAINED
WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SCATTERED MODERATE
CONVECTION IS FROM 31N-35N BETWEEN 32W-40W. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 09N36W TO 15N32W MOVING W AT 10-15 KT
THE WAVE REMAINS EMBEDDED WITHIN BROAD CYCLONIC FLOW S OF 15N
BETWEEN 29W-40W AND WITHIN A SURGE OF DEEP LAYER MOISTURE AS
SEEN ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE
CONVECTION IS FROM 13N-15N BETWEEN 32W-36W.

TROPICAL WAVE EXTENDS FROM 10N59W TO 17N58W MOVING W AT 10 KT.
EXAMINING SHORTWAVE INFRARED SATELLITE IMAGERY...IT APPEARS THAT
THE VERY WEAK SURFACE LOW PREVIOUSLY ANALYZED HAS OPENED UP AND
BECOME LOW TO MIDDLE LEVEL ENERGY EMBEDDED WITHIN THE WAVE AXIS.
THE WAVE REMAINS VERY SHALLOW AND EXHIBITS A LACK OF SIGNIFICANT
DEEP CONVECTION WITH GLOBAL MODEL DATA INDICATING A 700 MB
TROUGH AXIS FARTHER TO THE WEST OF THE WAVE AXIS ACROSS THE
EASTERN CARIBBEAN SEA. AS SUCH...CONVECTION IS MORE CLOSELY
ASSOCIATED WITH THE 700 MB TROUGH AT THIS TIME THAN THE WAVE
WITH WIDELY SCATTERED SHOWERS AND ISOLATED MODERATE CONVECTION
OCCURRING FROM 13N-19N BETWEEN 58W-66W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 11N16W TO
09N33W TO 09N44W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 09N44W TO 13N52W. SCATTERED MODERATE CONVECTION IS
FROM 04N-09N BETWEEN 14W-21W...FROM 06N-09N BETWEEN 26W-28W...
AND WITHIN 75 NM EITHER SIDE OF THE AXIS BETWEEN 40W-52W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES A MIDDLE TO UPPER LEVEL TROUGH IS
LOCATED OVER CENTRAL TEXAS WITH AXIS EXTENDING FROM 33N99W TO
25N103W. WITH MUCH OF THE LIFTING DYNAMICS MOVING OVER THE
ARKLATEX REGION THROUGH THE OVERNIGHT HOURS...THE TROUGH
SUPPORTS A SURFACE TROUGH ANALYZED OVER THE WESTERN GULF FROM
VERMILION BAY NEAR 30N92W TO 27N95W CURVING SOUTHWARD TO 20N95W.
LOW-LEVEL MOISTURE CONVERGENCE ALONG WITH MIDDLE TO UPPER LEVEL
DIFFLUENCE W OF 90W IS GENERATING WIDELY SCATTERED SHOWERS AND
ISOLATED TSTMS N OF 25N W OF 90W AND FROM 23N-25N W OF 96W.
GLOBAL MODELS ALL SUGGEST CYCLOGENESIS TO TAKE PLACE OVER THE
NEXT 12 TO 24 HOURS ACROSS THE NW GULF WATERS AND QUICKLY MOVE
NE BECOMING EMBEDDED WITHIN THE NEXT COLD FRONT TO SWEEP FROM
THE CENTRAL PLAINS INTO THE SE CONUS BY EARLY TUESDAY. THIS WILL
RESULT IS GENERAL SURFACE TROUGHING ACROSS MUCH OF THE GULF AND
PLACE IT UNDER 10 TO 20 KT S TO SW WINDS E OF 90W AND 10 TO 20
KT W TO NW WINDS N OF 24N W OF 90W. ELSEWHERE...A WEAK UPPER
LEVEL SHORTWAVE IS CENTERED NORTH OF THE LOWER FLORIDA KEYS NEAR
25N83W AND IS PROVIDING ENOUGH MIDDLE TO UPPER LEVEL LIFT TO
GENERATE ISOLATED SHOWERS AND TSTMS S OF 27N E OF 85W...
INCLUDING THE FLORIDA STRAITS.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER BELIZE
NEAR 17N88W THAT EXTENDS INFLUENCE AS FAR EAST AS 79W. A
DIFFLUENT ENVIRONMENT REMAINS MAXIMIZED OVER PORTIONS OF THE NW
CARIBBEAN AND CENTRAL AMERICA GENERATING WIDELY SCATTERED
SHOWERS AND TSTMS FROM 15N-21N BETWEEN 82W-91W...INCLUDING THE
GULF OF HONDURAS. FARTHER EAST...AN UPPER LEVEL LOW IS CENTERED
NEAR 14N74W AND EXTENDS AN INVERTED UPPER LEVEL TROUGH AXIS
NORTHWARD FROM THE UPPER LEVEL LOW CENTER TO OVER EASTERN CUBA
NEAR 20N76W. WATER VAPOR IMAGERY INDICATES THAT MOSTLY DRY AIR
AND IS ASSOCIATED WITH THIS FEATURE ACROSS THE CENTRAL CARIBBEAN
BETWEEN 68W-79W. FINALLY...ACROSS THE EASTERN CARIBBEAN...AS
MENTIONED ABOVE...A TROPICAL WAVE IS APPROACHING THE LESSER
ANTILLES ANALYZED IN THE VICINITY OF 58W. A WEAK 700 MB TROUGH
IS ALSO NOTED WEST OF THE WAVE AXIS AND THIS IS PROVIDING FOR AN
OVERALL UNSTABLE ATMOSPHERE WITH WIDELY SCATTERED SHOWERS AND
ISOLATED TSTMS FROM 13N-19N BETWEEN 58W-66W. OTHERWISE...
EASTERLY TRADES ARE EXPECTED TO PERSIST IN THE RANGE OF 10 TO 20
KT THROUGH TUESDAY.

ATLANTIC OCEAN...
A WEAK UPPER LEVEL SHORTWAVE IS CENTERED OVER THE SE GULF OF
MEXICO NEAR 25N82W AND CONTINUES TO PROVIDE ENOUGH MIDDLE TO
UPPER LEVEL LIFT IN THE ATMOSPHERE TO GENERATING ISOLATED
SHOWERS ACROSS THE NW BAHAMAS...FLORIDA STRAITS...AND PORTIONS
OF THE INLAND SOUTHERN FLORIDA PENINSULA THIS EVENING. MOSTLY
EMBEDDED WITHIN EASTERLY FLOW AND LOCATED ON THE SOUTHERN
PERIPHERY OF A RIDGE ANCHORED TO THE NORTH NEAR THE OUTER
BANKS...THE SHOWER ACTIVITY REMAINS FROM 22N-29N W OF 76W.
FARTHER NORTHEAST...A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM
36N56W INTO THE DISCUSSION ARE TO A BASE NEAR 26N61W. THIS
TROUGH SUPPORTS A DISSIPATED COLD FRONT FROM 31N59W TO 27N65W...
AND A PRE-FRONTAL SURFACE TROUGH FROM 31N59W TO 24N63W. NO
SIGNIFICANT DEEP CONVECTION IS NOTED WITH EITHER FEATURE...
HOWEVER ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE
OF THE BOTH BOUNDARIES. FINALLY...WHILE TROPICAL STORM NADINE
TRACKS TO THE EAST-NORTHEAST AND NORTH OF THE DISCUSSION
AREA...A SURFACE RIDGE IS ESTABLISHED FROM THE CANARY ISLANDS
SOUTHWESTWARD TO 20N50W ANCHORED BY A 1018 MB HIGH CENTERED NEAR
25N26W.

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

$$
HUFFMAN



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