[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 082352
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN SEP 08 2013

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 DEPRESSION NINE IS CENTERED NEAR 13.1N 21.4W AT 09/0000
UTC OR 165 NM SE OF PRAIA CAPE VERDE ISLANDS MOVING W AT 10 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED
WIND SPEED IS 25 KT WITH GUSTS TO 35 KT. NUMEROUS MODERATE AND
SCATTERED STRONG CONVECTION IS FROM 10N-17N BETWEEN 20W-26W WITH
SCATTERED MODERATE AND ISOLATED STRONG CONVECTION ELSEWHERE FROM
10N-17N BETWEEN 17W-27W. SEE LATEST NHC INTERMEDIATE PUBLIC
ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC AND THE
FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC FOR MORE DETAILS.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 14N38W TO 21N38W MOVING W AT 10-15
KT. A 1010 MB LOW IS CENTERED ALONG THE WAVE AXIS NEAR 18N AND
THIS REMAINS THE FOCUS FOR WIDELY SCATTERED MODERATE CONVECTION
OCCURRING FROM 18N-23N BETWEEN 34W-42W. GLOBAL MODELS SUGGEST
THE WAVE WILL CONTINUE TO DRIFT WESTWARD DURING THE NEXT FEW
DAYS WEAKENING SOMEWHAT AS IT APPROACHES W OF 45W AS A MID-
LATITUDE UPPER LEVEL TROUGH DIGS SOUTHWARD AND BEGINS TO PROVIDE
AN INCREASED SHEAR ENVIRONMENT ACROSS THE CENTRAL TROPICAL ATLC.

TROPICAL WAVE EXTENDS FROM 13N87W TO 22N87W MOVING W AT 10-15
KT. THE WAVE COINCIDES WITH BROAD AND WEAK SURFACE TO 700 MB
TROUGHING OVER THE NW CARIBBEAN SEA...THE YUCATAN PENINSULA...
AND PORTIONS OF THE SW GULF OF MEXICO. SCATTERED MODERATE
CONVECTION IS FROM 13N-22N BETWEEN 84W-93W...AND IT IS LIKELY
ENHANCED BY BROAD UPPER LEVEL TROUGHING TO THE NORTH OVER THE
GULF OF MEXICO PROVIDING A DIFFLUENT ENVIRONMENT FOR SUSTAINING
CONVECTION. ANY CONVECTION OCCURRING ACROSS INTERIOR PORTIONS OF
CENTRAL AMERICA THIS EVENING FACE THE INCREASED LIKELIHOOD OF
LOCALIZED FLASH FLOODING AND MUD SLIDES.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 15N17W TO
12N25W TO 18N38W TO 13N44W. THE INTERTROPICAL CONVERGENCE ZONE
AXIS EXTENDS FROM 13N44W TO 09N50W TO 08N55W. ASIDE FROM
CONVECTION ASSOCIATED WITH TROPICAL DEPRESSION NINE AND THE
TROPICAL WAVE ALONG 38W...ISOLATED MODERATE CONVECTION IS FROM
05N-13N BETWEEN 22W-32W...AND FROM 08N-12N BETWEEN 43W-47W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL TROUGH AXIS EXTENDS FROM OVER THE SW NORTH ATLC
NEAR 29N81W OVER THE FLORIDA PENINSULA AND OVER THE NE GULF
WATERS TO 29N91W. THIS UPPER LEVEL PATTERN IS RESULTING IN MOST
OF THE GULF BASIN UNDER THE INFLUENCE OF WEST-NORTHWESTERLY FLOW
ALOFT. OVER WESTERN PORTIONS OF THE BASIN STRETCHING INLAND OVER
EASTERN MEXICO...ANOTHER UPPER LEVEL TROUGH EXTENDS FROM AN
UPPER LEVEL LOW CENTERED OVER WEST TEXAS NEAR 30N101W SE TO
22N95W. THIS TROUGHING SUPPORTS A SURFACE TROUGH ANALYZED FROM
24N96W TO 18N93W WITH SCATTERED SHOWERS AND ISOLATED TSTMS
OCCURRING OVER A LARGE PORTION OF THE WESTERN GULF W OF 89W. THE
APPROACH OF A TROPICAL WAVE ALONG 87W IS ALSO GENERATING
SCATTERED SHOWERS AND STRONG TSTMS ACROSS THE YUCATAN PENINSULA
THIS EVENING. E-SE WINDS IN THE RANGE OF 5-15 KT WILL PERSIST
THROUGH THE OVERNIGHT HOURS INTO MONDAY AS SURFACE RIDGING
REMAINS ANCHORED OVER THE SE CONUS. EASTERLY WINDS WILL
GRADUALLY INCREASE TO 10-20 KT TUESDAY INTO WEDNESDAY AS THE
PRESSURE GRADIENT BETWEEN THE RIDGE AND LOWER PRESSURE OVER
SOUTHERN MEXICO STRENGTHENS.

CARIBBEAN SEA...
AN NARROW UPPER LEVEL RIDGE AXIS EXTENDS FROM OVER HISPANIOLA
NEAR 18N72W TO OVER EASTERN HONDURAS NEAR 15N84W. NORTH OF THIS
RIDGE AXIS...BROAD UPPER LEVEL TROUGHING AND A DIFFLUENT
ENVIRONMENT REMAINS AS A LIFTING MECHANISM GENERATING SCATTERED
SHOWERS AND TSTMS N OF 17N BETWEEN 74W-91W. THE PRESENCE OF A
TROPICAL WAVE ALONG 87W IS ALSO ADDING INCREASED LOW-LEVEL
MOISTURE CONVERGENCE ACROSS FAR WESTERN PORTIONS OF THE NW
CARIBBEAN...CENTRAL AMERICA...AND YUCATAN PENINSULA...COINCIDING
WITH THE STRONGEST ONGOING CONVECTION AT THIS TIME. SOUTH OF THE
RIDGE AXIS...CONDITIONS REMAINS GENERALLY FAIR WITH ONLY
SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING WITHIN 90 NM
EITHER SIDE OF THE MONSOON TROUGH AXIS ANALYZED FROM NORTHERN
COLOMBIA NEAR 09N76W TO 09N79W TO THE BASE OF THE TROPICAL WAVE
NEAR 13N87W. FINALLY...SURFACE TROUGHING EXTENDS SOUTHWESTWARD
FROM THE REMNANT LOW OF GABRIELLE CENTERED IN THE SW NORTH ATLC
NEAR 25N69W TO THE NORTHERN COAST OF HISPANIOLA NEAR 20N72W. LOW-
LEVEL MOISTURE CONVERGENCE E OF 74W AND A FAVORABLE UPPER LEVEL
DIFFLUENT ENVIRONMENT IN THE VICINITY OF HISPANIOLA IS
GENERATING SCATTERED SHOWERS AND TSTMS N OF 14N BETWEEN 67W-74W.
OTHERWISE...THE LESSER ANTILLES REMAIN UNDER FAIR SKIES AND
TRANQUIL CONDITIONS THIS EVENING DUE TO SURFACE RIDGING
EXTENDING SOUTHWESTWARD FROM THE CENTRAL ATLC.

HISPANIOLA...
CURRENTLY SURFACE TROUGHING EXTENDS FROM THE REMNANT LOW OF
GABRIELLE NEAR 25N69W TO THE NORTHERN COAST OF THE ISLAND NEAR
20N72W. LOW-LEVEL MOISTURE CONVERGENCE EAST OF THIS TROUGHING
AND A FAVORABLE UPPER LEVEL DIFFLUENT PATTERN OVER THE ISLAND
CONTINUE TO SUPPORT SCATTERED SHOWERS AND TSTMS AT THIS TIME.
WITH THE SURFACE TROUGHING SLOWLY DRIFTING NORTHEAST OVER THE
NEXT 24 TO 48 HOURS...CONDITIONS ARE EXPECTED TO GRADUALLY
IMPROVE BY LATE TUESDAY AS THE MORE USUAL TRADE WIND REGIME RE-
ESTABLISHES ITSELF. AS ALWAYS...WITH PEAK DAYTIME HEATING AND
INSTABILITY...AFTERNOON AND EARLY EVENING CONVECTION IS POSSIBLE
OVER THE NEXT FEW DAYS.

ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH AXIS EXTENDS INTO THE DISCUSSION
AREA NEAR 32N74W TO OVER THE FLORIDA PENINSULA NEAR 28N81W AND
WESTWARD OVER PORTIONS OF THE NE GULF OF MEXICO. THIS TROUGHING
SUPPORTS A STATIONARY FRONT TO THE NORTH...HOWEVER A HIGH
PRESSURE RIDGE ANCHORED BY A 1017 MB HIGH CENTERED ACROSS
ALABAMA CONTINUES TO DOMINATE ACROSS MUCH OF THE SW NORTH ATLC W
OF 70W. WITH THE MID-LEVEL LIFT IN PLACE WIDELY SCATTERED
SHOWERS AND ISOLATED TSTMS ARE OCCURRING OVER THE SOUTHERN
FLORIDA PENINSULA AND ADJACENT COASTAL WATERS FROM 25N-27N
BETWEEN 76W-82W WITH ISOLATED SHOWERS ELSEWHERE N OF 24N BETWEEN
72W-77W. FARTHER EAST...THE REMNANT 1008 MB LOW OF GABRIELLE IS
CENTERED NEAR 25N69W WITH A SURFACE TROUGH AXIS EXTENDING N-NE
TO BEYOND BERMUDA NEAR 32N65W AND S-SW FROM THE LOW CENTER TO
THE NORTHERN COAST OF HISPANIOLA NEAR 20N72W. SCATTERED SHOWERS
AND ISOLATED TSTMS ARE OCCURRING PRIMARILY EAST OF THE SURFACE
TROUGHING W OF A LINE FROM 32N56W TO 18N66W. EAST OF THIS
CONVECTION...A SURFACE RIDGE ANCHORED BY A 1032 MB HIGH CENTERED
S OF THE AZORES NEAR 37N29W DOMINATES THE REMAINDER OF THE
CENTRAL AND EASTERN ATLC.

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

$$
HUFFMAN


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