[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181152
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT AUG 18 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
1115 UTC.

...SPECIAL FEATURES...

TROPICAL STORM HELENE IS CENTERED NEAR 21.9N 97.5W AT 18/1200
UTC OR ABOUT XX NM ENE OF TUXPAN MEXICO AND ABOUT 35 NM SE OF
TAMPICO MEXICO MOVING NW AT 7 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH
GUSTS TO 45 KT. THE BROAD CYCLONIC WIND FIELD RELATED TO HELENE
IS GENERATING SCATTERED SHOWERS AND TSTMS S OF 24N W OF 91W. SEE
LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

TROPICAL STORM GORDON WAS UPGRADED TO HURRICANE STATUS EARLY
THIS MORNING...NOW CENTERED NEAR 33.9N 39.6W AT 18/1200...OR
ABOUT 660 NM WSW OF THE AZORES MOVING E AT 16 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 985 MB. MAXIMUM SUSTAINED WIND SPEED
HAVE INCREASED TO 70 KT WITH GUSTS TO 85 KT. WIDELY SCATTERED
MODERATE CONVECTION IS FROM 33N-37N BETWEEN 37W-42W. SEE LATEST
NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT3/WTNT33 AND THE FULL FORECAST/ ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS.

A TROPICAL WAVE IS LOCATED IN THE ERN ATLC EXTENDING FROM 18N23W
TO A 1008 MB LOW NEAR 12N27W...EMBEDDED WITHIN THE MONSOON GYRE
DESCRIBED BELOW. SCATTERED SHOWERS AND THUNDERSTORMS ARE FROM
11N-15N BETWEEN 26W-31W...WITHIN THE BROAD CONVECTIVE REGION
ASSOCIATED TO THE MONSOON TROUGH. CONDITIONS APPEAR CONDUCIVE
FOR GRADUAL DEVELOPMENT DURING THE NEXT FEW DAYS...AND THIS
SYSTEM HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS...AS IT MOVES WESTWARD AT 15 TO 20 MPH.

...TROPICAL WAVES...

TROPICAL WAVE MOVES ACROSS THE CENTRAL TROPICAL ATLC WITH AXIS
EXTENDING FROM 17N42W TO 10N40W MOVING W AT 15-20 KT. THE WAVE
REMAINS EMBEDDED WITHIN A BROAD AREA OF ENHANCED DEEP LAYER
MOISTURE AS NOTED ON THE TOTAL PRECIPITABLE WATER IMAGERY.
CONVECTION AROUND THE WAVE AXIS IS LIMITED DUE TO A LARGE DRY
AIRMASS ASSOCIATED WITH THE SAHARAN AIR LAYER. ANY SHOWER
ACTIVITY IS LIKELY ASSOCIATED TO THE BROAD MONSOONAL GYRE.

TROPICAL WAVE MOVES ACROSS THE MONA PASSAGE WITH AXIS EXTENDING
FROM 21N68W TO 13N65W MOVING W AT 15-20 KT. SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS ARE FROM 15N-23N BETWEEN 65W-70W.
INCREASED CLOUDINESS AND PRECIPITATION IS EXPECTED ACROSS
HISPANIOLA THROUGH THE WEEKEND.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST OF SENEGAL...
ABOUT 80 NM N OF DAKAR TO 18N21W...RESUMING FROM THE SPECIAL
FEATURE 1008 LOW PRESSURE SYSTEM NEAR 12N27W ALONG 12N36W TO
8N45W. THE ITCZ AXIS BEGINS FORM THIS POINT TO THE COAST OF
GUYANA NEAR 7N58W. A BROAD AREA OF CLUSTERS OF SCATTERED
MODERATE CONVECTION COVERS FROM 6N-15N BETWEEN 25W-47W...AND
FROM 11N-17N E OF 20W.

...DISCUSSION...

GULF OF MEXICO...
WEAK SURFACE RIDGING IS NOTED ACROSS MOST OF THE DISCUSSION AREA
THIS MORNING...CENTERED AROUND A 1016 MB HIGH NEAR 27N89W. BROAD
UPPER LEVEL ANTICYCLONIC OUTFLOW FROM TROPICAL STORM HELENE
COVERS MOST OF THE GULF ON WATER VAPOR IMAGERY. DESPITE THESE
CONDITIONS AT SURFACE AND ALOFT...MID TO UPPER LEVEL CLOUDINESS
WITH A FEW ISOLATED SHOWERS COVER A GREAT PORTION OF THE NE AND
N-CENTRAL GULF...ASSOCIATED TO THE SRN EXTENSION OF A BROAD
UPPER LEVEL TROUGH MOVING OFF THE ERN CONUS SEABOARD. A WEAK
SURFACE TROUGH WAS ANALYZED FROM THE NRN FLORIDA PENINSULA NEAR
31N82W TO 28N84W. A FEW ISOLATED SHOWERS ARE NEAR THE TROUGH
AXIS. TROPICAL STORM HELENE CONTINUES TO IMPACT THE WRN MEXICO
COAST AND WRN BAY OF CAMPECHE AS IT MAKES IT'S WAY INLAND NEAR
THE CITY OF TAMPICO MEXICO THIS MORNING. THE BROAD CYCLONIC WIND
FIELD RELATED TO HELENE IS GENERATING SCATTERED SHOWERS AND
TSTMS S OF 24N W OF 91W. WINDS WILL REMAIN MODERATE TO FRESH IN
THIS REGION DURING THE NEXT 24 HOURS.

CARIBBEAN SEA...
SCATTERED MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS ARE NOTED
ACROSS THE SW CARIBBEAN S OF 13N W OF 75W...ESPECIALLY IN THE
VICINITY OF THE MONSOON TROUGH ANALYZED FROM NRN COLOMBIA TO SRN
COSTA RICA. WATER VAPOR SHOWS AN UPPER LEVEL INVERTED TROUGH
MOVING ACROSS THIS AREA ENHANCING THE CONVECTION NEAR THE
MONSOON TROUGH. SIMILAR CONVECTION IS NOTED WITHIN 200 NM ACROSS
THE WATERS S OF PUERTO RICO...ASSOCIATED WITH THE PASSAGE OF A
TROPICAL WAVE. THE SRN EXTENSION OF AN ELONGATED UPPER LOW
CENTERED IN THE SW ATLC IS PRODUCING A CLUSTER OF SCATTERED
SHOWERS OVER THE NE COASTAL WATERS OF DOMINICAN REPUBLIC. SOME
NOCTURNAL DRAINAGE AND SEA BREEZE CONVERGENCE PRODUCED SOME WEAK
SHOWERS MOVING OFF THE S-CENTRAL COAST OF CUBA AND WRN JAMAICA
...EXPECTED TO DISSIPATE LATER THIS MORNING. THE REMAINDER OF
THE CARIBBEAN IS DOMINATED BY DRY AIR AND SUBSIDENCE ALOFT NOTED
ON WATER VAPOR IMAGERY.

ATLANTIC OCEAN...
WATER VAPOR SHOWS A BROAD UPPER LEVEL TROUGH MOVING OFF THE ERN
CONUS SEABOARD THIS MORNING. WEAK TO MODERATE DIFFLUENCE ALOFT
FROM THIS UPPER LEVEL FEATURE IS GENERATING SCATTERED SHOWERS
AND THUNDERSTORMS ACROSS THE WRN ATLC DISCUSSION AREA N OF 25N W
OF 65W. A WEAK SURFACE TROUGH APPEARED ON AN EARLIER ASCAT PASS
FROM 30N76W TO 27N79W. ALSO EMBEDDED WITHIN THIS CONVECTIVE
AREA...AN UPPER LEVEL LOW IS CENTERED NEAR 27N65W. ELSEWHERE
ACROSS THE REMAINDER OF THE CENTRAL AND EASTERN ATLC...A BROAD
SURFACE RIDGE COVERS THE AREA ANCHORED BY A 1020 MB HIGH
CENTERED NEAR 27N55W...EXTENDING A RIDGE AXIS WESTWARD ALONG 25N
INTO THE GULF OF MEXICO...AND A RIDGE AXIS EASTWARD TO 25N23W.
ALSO...THE SAHARAN AIR LAYER AND ASSOCIATED DUST IS FURTHER
MAINTAINING STABLE CONDITIONS ACROSS THE DISCUSSION AREA E OF
62W.

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

$$

GARCIA



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