[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 262357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED SEP 25 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
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM NADINE IS CENTERED NEAR 30.2N 30.8W AT 26/2100
UTC OR ABOUT 505 NM SSW OF THE AZORES MOVING SSW AT 4 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB. MAXIMUM SUSTAINED
WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. WIDELY SCATTERED
MODERATE CONVECTION IS FROM 29N-33N BETWEEN 27W-33W. SEE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 09N28W TO 19N26W MOVING W AT 10-15
KT. THE WAVE COINCIDES WELL WITH A BROAD 700 MB TROUGH NOTED IN
GLOBAL MODEL GUIDANCE BETWEEN 22W-32W. TOTAL PRECIPITABLE WATER
IMAGERY ALSO INDICATES THE WAVE LIES WITHIN A MOISTURE MAXIMUM
FROM 10N-19N BETWEEN 19W-25W. ISOLATED MODERATE CONVECTION IS
OCCURRING FROM 13N-18N BETWEEN 21W-25W.

TROPICAL WAVE EXTENDS FROM 12N76W TO 17N73W MOVING W AT 10 KT.
THIS WAVE ALSO COINCIDES WITH A SHARPER...MORE DEFINED 700 MB
TROUGH OVER THE CENTRAL CARIBBEAN ALONG 74W AND IS EXPECTED TO
MOVE WESTWARD ON THE SOUTHERN PERIPHERY OF A MID-LEVEL RIDGE
ANCHORED OVER THE SW NORTH ATLC NEAR 27N76W. TOTAL PRECIPITABLE
WATER VALUES ACROSS THE CENTRAL CARIBBEAN REMAIN ELEVATED AS THE
WAVE MOVE THROUGH THE REGION WITH RESULTANT ISOLATED MODERATE
CONVECTION AND SCATTERED SHOWERS FROM 13N-18N BETWEEN 70W-76W. A
FEW ISOLATED SHOWERS AND TSTMS ARE ALSO OCCURRING NORTH OF THE
WAVE AXIS ACROSS PORTIONS OF HISPANIOLA THIS EVENING.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO
09N28W TO 08N38W. THE INTERTROPICAL CONVERGENCE ZONE AXIS
EXTENDS FROM 08N38W TO 09N48W. ISOLATED MODERATE CONVECTION IS
FROM 05N-09N BETWEEN 09W-14W...AND FROM 02N-06N BETWEEN 25W-35W.

...DISCUSSION...

GULF OF MEXICO...
A WEAK UPPER LEVEL TROUGH AXIS EXTENDS FROM 28N91W TO A BASE IN
THE SOUTH-CENTRAL GULF NEAR 22N88W. WHILE WATER VAPOR IMAGERY
INDICATES FAIRLY DRY AIR ALOFT NE OF THE TROUGH AXIS...A SURFACE
TROUGH ANALYZED FROM 23N92W TO 27N90W CONTINUES TO PROVIDE
LOW-LEVEL FOCUS FOR SCATTERED SHOWERS AND TSTMS OCCURRING MAINLY
EAST OF THE SURFACE TROUGH FROM 23N-27N BETWEEN 85W-92W. THE
REMAINDER OF THE GULF THIS EVENING IS UNDER THE INFLUENCE OF
SURFACE RIDGING...HOWEVER DUE TO THE UPPER LEVEL DIFFLUENCE
GENERATED BY THE UPPER LEVEL TROUGHING...MIDDLE TO UPPER LEVEL
MOISTURE IS PLENTIFUL AND CONTINUES TO COVER MUCH OF THE EASTERN
GULF...INCLUDING THE FLORID PENINSULA. ISOLATED SHOWERS AND
TSTMS ARE NOTED ON SATELLITE IMAGERY S OF 28N WITH MORE INTENSE
CONVECTION ONGOING ACROSS THE FLORIDA AND YUCATAN PENINSULAS.
LOOKING AHEAD...THE REMAINDER OF THE WEEK HOLDS RELATIVELY
BENIGN CONDITIONS FOR THE GULF AS SURFACE RIDGING IS FORECAST
ANCHOR TO THE NORTH OVER THE SE CONUS AND PROVIDE THE GULF WITH
MOSTLY GENTLE TO MODERATE E TO SE BREEZE CONDITIONS.

CARIBBEAN SEA...
UPPER LEVEL RIDGING EXTENDS OVER THE NW CARIBBEAN BETWEEN TWO
UPPER LEVEL TROUGHS...ONE OVER THE EASTERN GULF OF MEXICO AND
THE OTHER OVER THE SW CARIBBEAN IN THE VICINITY OF AN UPPER
LEVEL LOW CENTERED NEAR 12N76W. UPPER LEVEL DIFFLUENCE IS
MAXIMIZED OVER MUCH OF THE NW CARIBBEAN AND CENTRAL AMERICA THIS
EVENING WHICH IS GENERATING SCATTERED SHOWERS AND TSTMS W OF
82W...INCLUDING MUCH OF INLAND CENTRAL AMERICA. A TROPICAL WAVE
IS BEGINNING TO ENTER THE WESTERN CARIBBEAN AND LIES ALONG 75W
AND COINCIDES WITH A MID-LEVEL 700 MB TROUGH. LOW TO MIDDLE
LEVEL MOISTURE CONVERGENCE CONTINUES TO GENERATE AN AREA OF
SCATTERED SHOWERS AND ISOLATED TSTMS FROM 13N-18N BETWEEN
70W-76W. SOME OF THIS ACTIVITY SPREADS NORTHWARD AS CONVECTION
HAS BLOSSOMED THIS EVENING OVER PORTIONS OF HISPANIOLA...EASTERN
CUBA...AND JAMAICA. OTHERWISE...MODERATE TO FRESH TRADES WILL
DOMINATE OVER THE NEXT FEW DAYS.

ATLANTIC OCEAN...
MOST OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF AN UPPER
LEVEL ANTICYCLONIC CIRCULATION CENTERED NORTH OF HISPANIOLA NEAR
24N70W. NORTH OF THIS CIRCULATION...SOUTHWEST TO WESTERLY UPPER
LEVEL FLOW DOMINATES AND CONTINUES TO SUPPORT A VERY WEAK
STATIONARY FRONT ANALYZED FROM 32N71W TO 29N74W WHICH
TRANSITIONS TO A SURFACE TROUGH TO THE NW BAHAMAS NEAR 26N78W.
WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING FROM
25N-32N BETWEEN 61W-81W...INCLUDING PORTIONS OF THE FLORIDA
PENINSULA. WHILE ORGANIZATION OF ACTIVITY ACROSS THIS AREA LACKS
ANY SIGNIFICANT UPPER LEVEL SUPPORT...IT IS FORECAST TO REMAIN
AN AREA PRONE TO BROAD SURFACE TROUGHING IN BETWEEN SURFACE
RIDGING OVER THE SE CONUS AND THE CENTRAL ATLC N OF 25N. FARTHER
EAST...AN UPPER LEVEL LOW IS CENTERED NEAR 29N47W THAT EXTENDS
AN UPPER LEVEL TROUGH AXIS SW TO OVER THE LESSER ANTILLES NEAR
16N60W. LOCATED SE OF THE TROUGH AXIS...A PAIR OF SURFACE
TROUGHS ARE ANALYZED S OF 25N BETWEEN 45W-60W. THE FIRST SURFACE
TROUGH EXTENDS FROM 19N56W TO 23N50W AND CONTINUES TO GENERATE
THE MORE ACTIVE CONVECTION WITH SCATTERED SHOWERS AND TSTMS
OCCURRING FROM 20N-23N BETWEEN 47W-58W. THE OTHER SURFACE TROUGH
IS LOCATED DIRECTLY SOUTH OF THE NORTHERN FEATURE ANALYZED FROM
13N57W TO 16N52W. THIS WEAKER TROUGH AXIS IS GENERATING WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS FROM 14N-18N BETWEEN
47W-56W. FINALLY...TROPICAL STORM NADINE CONTINUES TO SPIN IN
THE VICINITY OF 30N30W WITH CYCLONIC WIND INFLUENCE REACHING
SOUTHWARD TO 25N BETWEEN 25W-36W. OTHERWISE...A SURFACE RIDGE
AXIS EXTENDS FROM THE CANARY ISLANDS TO A 1016 MB HIGH CENTERED
NEAR 22N40W.

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

$$
HUFFMAN



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