[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 301751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE AUG 30 2011

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

TROPICAL STORM KATIA IS CENTERED NEAR 12.3N 33.4W AS OF 30/1500
UTC...OR ABOUT 550 NM WSW OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MOVING WNW AT 16 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003
MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT.
PLEASE SEE THE LATEST INTERMEDIATE PUBLIC ADVISORY UNDER
AWIPS/WMO HEADER MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST/
ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE
DETAILS. MOST OF THE ASSOCIATED CONVECTION IS W OF THE STORM
CENTER DUE TO SOME UPPER LEVEL SHEAR. SCATTERED MODERATE/STRONG
CONVECTION IS FROM 9N-15N BETWEEN 33W-39W. THE SHEAR IS EXPECTED
TO DECREASE WHICH WILL ALLOW FURTHER STRENGTHENING OVER THE NEXT
SEVERAL DAYS.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH IS ANALYZED ACROSS MAURITANIA FROM 22N10W SW
TO THE ERN CAPE VERDE ISLANDS NEAR 16N23W. THE CIRCULATION OF
KATIA HAS DISRUPTED THE MONSOON TROUGH TO THE W OF THE CAPE
VERDE ISLANDS. A SMALL PORTION OF THE ITCZ EXISTS TO THE W OF
KATIA ALONG 12N48W TO 9N62W. CONVERGENCE ALONG THIS AXIS IS
SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN
45 NM S...AND 120 NM N OF THE AXIS. AS KATIA MOVES WNW...THE
MONSOON TROUGH WILL RE-ESTABLISH WHILE THE ITCZ WILL BEGIN TO
BREAKDOWN.

...DISCUSSION...

GULF OF MEXICO...
A STATIONARY FRONT CONTINUES TO SIT OVER THE NE GULF FROM NEAR
TALLAHASSEE TO PANAMA CITY FLORIDA TO S OF LOUISIANA NEAR
29N90W. THE FRONT IS SUPPORTING BY AN UPPER LEVEL TROUGH THAT
EXTENDS DOWN THE ERN SEABOARD INTO THE NRN GULF ALONG 31N82W TO
23N100W. THE UPPER TROUGH IS ACCOMPANIED BY STRONG DRY AIR AND
SUBSIDENCE WHICH IS SUPPORTING FAIR WEATHER NE OF A LINE FROM
31N82W TO 23N98W. S OF THIS LINE...DEEP LAYERED MOISTURE
PREVAILS EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY AND WATER
VAPOR IMAGERY. UPPER LEVEL DIFFLUENCE AROUND THE E SIDE OF THE
UPPER TROUGH ALONG WITH THE ENHANCED MOISTURE IS HELPING
SUPPORTS SCATTERED SHOWERS/THUNDERSTORMS FROM 24N-29N BETWEEN E
OF 88W. A SURFACE TROUGH JUST W OF THE YUCATAN PENINSULA ALONG
22N90W TO 17N92W IS ALSO SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS FROM 21N-23N BETWEEN 91W-93W. THIS TROUGH
IS EXPECTED TO CONTINUE TO DRIFT WNW OVER THE NEXT COUPLE OF
DAYS. THE STATIONARY FRONT IN THE NE GULF IS EXPECTED TO
DISSIPATE OVER THE NEXT 24 HOURS AS THE UPPER LEVEL TROUGH
SUPPORTING IT MOVES TO THE E. SIGNIFICANT MOISTURE IS EXPECTED
TO REMAIN OVER MUCH OF THE GULF OF MEXICO WITH A LIKELY CHANCE
OF SCATTERED SHOWERS/THUNDERSTORMS.

CARIBBEAN SEA...
HIGH MOISTURE VALUES EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY
COVER THE WRN HALF OF THE CARIBBEAN. THIS IS HELPING ENHANCE
SCATTERED SHOWERS/THUNDERSTORMS ACROSS WRN CUBA...ERN NICARAGUA
AS WELL AS ISOLATED SHOWERS/THUNDERSTORMS OVER WATER FROM
13N-21N BETWEEN 79W-85W. CONTINUED SHOWER/THUNDERSTORM ACTIVITY
IN THIS AREA HAS CONTRIBUTED TO THE FORMATION OF A TROPICAL WAVE
WHICH WILL LIKELY BE ADDED TO THE 1800 UTC ANALYSIS. WAVE
FORMATION AND GROWTH IS ALSO POSSIBLE IN THE WRN CARIBBEAN...AND
CONDITIONS ARE CURRENTLY FAVORABLE FOR THIS TO OCCUR. MODEL
GUIDANCE IS ALSO IN FAVOR OF THIS FORMATION AND MOVES THE WAVE
TOWARDS THE WNW-NW INTO THE GULF OF MEXICO OVER THE NEXT COUPLE
OF DAYS. THIS WILL LIKELY SUPPORT CONTINUED SHOWER/THUNDERSTORM
ACTIVITY OVER THE NW CARIBBEAN OVER THE NEXT DAY OR SO. AN AREA
OF SCATTERED SHOWERS/THUNDERSTORMS ARE IN THE SW CARIBBEAN FROM
10N-13N BETWEEN 78W-80W. MUCH OF THE CENTRAL AND ERN CARIBBEAN
IS UNDER MOSTLY FAIR CONDITIONS. ALOFT...AN UPPER LEVEL RIDGE
COVERS THE WRN CARIBBEAN EXTENDING FROM NEAR 17N94W TO THE NW
BAHAMAS AND W ATLC. A WEAK UPPER LEVEL LOW IS OVER HISPANIOLA
EMBEDDED WITH DRY AIR ALOFT. WATER VAPOR IMAGERY ALSO INDICATES
DRY AIR ALOFT OVER THE ERN CARIBBEAN WHICH IS SUPPORTING THE
FAIR WEATHER ACROSS THIS AREA.

ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS COVER THE FAR WRN ATLC NW OF A
LINE FROM 24N78W TO 32N69W...ASSOCIATED WITH HIGH MOISTURE
VALUES AND UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH
OVER THE ERN SEABOARD AND AN UPPER LEVEL RIDGE EXTENDING FROM
CUBA...TO THE NW BAHAMAS...TO 32N68W. AN UPPER LEVEL LOW IN THE
CENTRAL ATLC NEAR 29N48W IS ALSO SUPPORTING AN AREA OF
SHOWERS/THUNDERSTORMS FROM 22N-32N BETWEEN 62W-67W. THE UPPER
LOW IS ALSO SUPPORTING A SURFACE TROUGH ALONG 31N49W TO 25N51W
WITH SCATTERED SHOWERS/THUNDERSTORMS FROM 27N-30N BETWEEN
51W-54W. A SECOND SURFACE TROUGH IS ALONG 27N41W TO 22N42W.
SCATTERED SHOWERS/THUNDERSTORMS ARE SHEARED TO THE E OF THE AXIS
FROM 21N-24N BETWEEN 36W-41W. BROAD UPPER RIDGING COVERS MUCH OF
THE TROPICAL ATLC CENTERED NEAR 20N27W SUPPORTING WEAK SURFACE
RIDGING AROUND A 1025 MB HIGH NEAR 30N29W. TO THE S...TROPICAL
STORM KATIA IS IMPACTING THE SRN TROPICAL ATLC. SEE SPECIAL
FEATURES ABOVE FOR MORE DETAILS. KATIA IS EXPECTED TO MOVE WNW
NEAR 16 KT. THE PAIR OF SURFACE TROUGHS ARE ALSO EXPECTED TO
MOVE WWD AROUND THE SUB-TROPICAL RIDGE IN THE N CENTRAL ATLC.

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

$$
WALTON






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