[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 212356
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT AUG 21 2010

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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION SIX IS CENTERED NEAR 11.0N 32.1W AT 21/2100
UTC OR 500 NM WSW OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING
W-NW AT 08 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB.
MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH GUSTS TO 35 KT.
STRENGTHENING IS FORECAST OVER THE NEXT FEW DAYS AS THE CYCLONE
RESIDES ON THE SOUTHWESTERN PERIPHERY OF AN UPPER LEVEL
ANTICYCLONIC CIRCULATION CENTERED NEAR 21N20W WITH AN UPPER
LEVEL RIDGE AXIS EXTENDING SW FROM THE CENTER TO 15N39W. THIS IS
EXPECTED TO PROVIDE AN OVERALL FAVORABLE UPPER LEVEL DIFFLUENT
ENVIRONMENT FOR THE SYSTEM TO MAINTAIN ORGANIZED CONVECTION AND
PROVIDE FOR MINIMAL WIND SHEAR. SCATTERED MODERATE AND ISOLATED
STRONG CONVECTION COVERS A BROAD AREA FROM 06N-16N BETWEEN
25W-41W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE EXTENDS FROM 12N46W TO 18N50W TO 25N49W MOVING W
AT 15-20 KT. SATELLITE IMAGERY INDICATES CYCLONIC FLOW IN THE
LOW-LEVEL CLOUD FIELD ALONG THE WAVE AXIS. AN AREA OF MAXIMUM
DEEP LAYER MOISTURE IS OBSERVED ON THE TPW IMAGERY FROM 10N-25N
BETWEEN 44W-53W...HOWEVER MUCH OF THE MOISTURE TO THE EAST OF
THE WAVE IS POSITIONED BENEATH A STABLE SAHARAN AIR LAYER THAT
COVERS MUCH OF THE CENTRAL ATLC N OF 15N BETWEEN 30W-45W. NO
SIGNIFICANT DEEP ORGANIZED CONVECTION ACCOMPANIES THE WAVE...
HOWEVER ISOLATED SHOWERS ARE FROM 10N-15N BETWEEN 46W-50W...AND
FROM 18N-24N BETWEEN 46W-52W.

TROPICAL WAVE EXTENDS FROM 14N69W TO 24N66W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH A MID-LEVEL TROUGH OVER THE W ATLC
BETWEEN 65W-74W. MAXIMUM TOTAL PRECIPITABLE WATER VALUES ARE
HIGHEST N OF 20N BETWEEN 60W-68W AS THIS MOISTURE CONTINUES TO
ADVECT NORTHWARD DUE TO A WEAKNESS IN THE SUBTROPICAL RIDGE
BETWEEN 70W-80W. ISOLATED MODERATE CONVECTION AND WIDELY
SCATTERED SHOWERS ARE OCCURRING FROM 18N-28N BETWEEN 62W-70W.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 11N48W 11N57W THEN RESUMES OVER THE
SOUTH-CENTRAL CARIBBEAN SEA NEAR 12N71W 11N80W 14N90W. ASIDE
FROM THE CONVECTION ASSOCIATED WITH T.D. SIX...ISOLATED MODERATE
CONVECTION IS FROM 04N-09N BETWEEN 41W-53W. FARTHER EAST OVER
THE TROPICAL EASTERN ATLC...THE GRADUAL DISSIPATION OF THE
MONSOON TROUGH THAT HAS PERSISTED OVER THE PAST SEVERAL DAYS IS
ANALYZED AS A SURFACE TROUGH FROM NE OF T.D. SIX NEAR 15N26W TO
17N18W. CONVECTION IS MOSTLY ASSOCIATED WITH THE ONGOING
TROPICAL CYCLONE LOCATED W OF 25W. ELSEWHERE...SCATTERED
MODERATE TO STRONG CONVECTION IS MOVING OFF THE W AFRICA COAST
FROM 04N-14N E OF 18W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER
SOUTHERN NEW MEXICO NEAR 32N107W AND EXTENDS AN UPPER LEVEL
RIDGE AXIS EASTWARD TO THE NE GULF NEAR 30N87W. THIS UPPER LEVEL
FEATURE IS PROVIDING EASTERLY FLOW ALOFT OVER MUCH OF THE GULF N
OF 22N. LOW TO MID-LEVEL INSTABILITY AND UPPER LEVEL DIFFLUENCE
PROVIDED BY THE UPPER LEVEL RIDGE IS GENERATING SCATTERED
SHOWERS AND TSTMS OVER THE EASTERN GULF AND FLORIDA PENINSULA NE
OF A LINE FROM 29N90W TO WESTERN CUBA NEAR 23N83W. A FEW
ISOLATED SHOWERS OVER WESTERN CUBA W OF 83W HAVE MOVED WESTWARD
AND EXTEND OVER THE YUCATAN CHANNEL FROM 21N-23N BETWEEN
83W-88W. OVER THE SW GULF...AN UPPER LEVEL LOW IS NOTED ON WATER
VAPOR IMAGERY NEAR 20N94W THAT IS SUPPORTING THE REMNANTS OF A
TROPICAL WAVE ANALYZED AS A SURFACE TROUGH FROM 20N98W TO 17N93W
OVER INTERIOR SOUTHERN MEXICO. SCATTERED SHOWERS AND TSTMS ARE
FOCUSED ALONG THE SURFACE TROUGH AND ARE LOCATED WITHIN 90 NM
EITHER SIDE OF A BOUNDARY. THE REMAINDER OF THE GULF IS UNDER
THE INFLUENCE OF THE EASTERN FLOW ALOFT MENTIONED ABOVE AND THIS
SUPPORTS A 1019 MB SURFACE HIGH CENTERED OVER THE CENTRAL GULF
NEAR 26N89W. CLEAR SKIES ARE NOTED ON SATELLITE IMAGERY N OF 20N
W OF 90W UNDER LIGHT ANTICYCLONIC WINDS.

CARIBBEAN SEA...
CONVERGENT LOW-LEVEL SOUTHEASTERLY FLOW DOMINATES ACROSS THE
WESTERN CARIBBEAN W OF 78W AND PORTIONS OF CENTRAL AMERICA THIS
EVENING. AN UPPER LEVEL TROUGH AXIS EXTENDS FROM AN UPPER LOW
CENTERED OVER THE WINDWARD PASSAGE NEAR 20N74W WESTWARD TO THE
NORTHERN YUCATAN PENINSULA NEAR 20N89W. THESE TWO FACTORS ALONG
WITH ABUNDANT MOISTURE AND INSTABILITY ARE GENERATING SCATTERED
SHOWERS AND TSTMS FROM 11N-18N BETWEEN 77W-87W. THE ITCZ AXIS
EXTENDS ACROSS THE SW CARIBBEAN ALONG 11N AND IS ALSO PROVIDING
LOW-LEVEL FOCUS FOR SCATTERED SHOWERS AND ISOLATED TSTMS OVER
PORTIONS OF COSTA RICA AND PANAMA THIS EVENING. FARTHER EAST...
THE UPPER LEVEL LOW CENTERED OVER THE WINDWARD PASSAGE IS
GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS OVER HISPANIOLA
AND THE NEARBY ADJACENT COASTAL WATERS FROM 16N-21N BETWEEN
68W-75W. THE APPROACH OF A TROPICAL WAVE ALONG 68W WILL CONTINUE
TO PROVIDE SCATTERED SHOWER ACTIVITY OVER THE NEXT 12-24 HOURS
AS THE WAVE MOVES WESTWARD OVER HISPANIOLA AND THE NORTH-CENTRAL
CARIBBEAN SEA. LASTLY...WHILE MUCH OF THE EASTERN CARIBBEAN
BETWEEN 63W-68W IS UNDER RELATIVELY CLEAR SKIES...THE APPROACH
OF A SURFACE TROUGH FROM 10N-16N ALONG 59W IS GENERATING
SCATTERED SHOWERS AND ISOLATED TSTMS FROM 09N-18N BETWEEN
57W-62W. INCREASED CLOUDINESS AND PRECIPITATION IS EXPECTED
ACROSS THE LESSER ANTILLES OVER THE NEXT 12-24 HOURS.

ATLANTIC OCEAN...
AN ANTICYCLONIC CIRCULATION CENTERED OVER THE SE CONUS NEAR
31N86W IS PROVIDING MOST OF THE W ATLC WITH NE UPPER LEVEL FLOW
N OF 22N W OF 72W. AN UPPER LEVEL LOW IS CENTERED OVER THE
WINDWARD PASSAGE NEAR 20N74W AND EXTENDS AN UPPER LEVEL TROUGH
AXIS NORTHWARD TO 30N70W. BETWEEN THESE TWO UPPER LEVEL
FEATURES...UPPER LEVEL DIFFLUENCE ALONG WITH LOW-LEVEL MOISTURE
AND DAYTIME INSTABILITY ARE GENERATING SCATTERED SHOWERS AND
ISOLATED TSTMS FROM 21N-31N W OF 72W. A TROPICAL WAVE ALONG 68W
IS EMBEDDED WITHIN IN THE NORTHERLY UPPER LEVEL FLOW EAST OF THE
UPPER LOW AND IS ADVECTING MOISTURE...WIDELY SCATTERED SHOWERS
AND ISOLATED TSTMS N-NW FROM 18N-28N BETWEEN 62W-70W. ELSEWHERE
ACROSS THE REMAINDER OF THE CENTRAL AND EASTERN ATLC...SURFACE
RIDGING DOMINATES N OF 25N ANCHORED BY A 1024 MB HIGH CENTERED
NEAR 31N33W MAINTAINING GENERALLY FAIR WEATHER E OF 62W. THE
RIDGE AXIS EXTENDS FROM THE HIGH CENTER ALONG 30N TO 50W THEN SW
TO 22N60W. ALOFT...AN UPPER LEVEL ANTICYCLONE COVERS THE CENTRAL
ATLC CENTERED NEAR 31N44W.

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

$$
HUFFMAN



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