[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 080554
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU SEP 08 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

HURRICANE KATIA IS CENTERED NEAR 31.4N 70.2W AT 08/0600 UTC OR
ABOUT 287 NM W-SW OF BERMUDA MOVING W-NW AT 11 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 975 MB. MAXIMUM SUSTAINED WIND SPEED
IS 80 KT WITH GUSTS TO 95 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. KATIA IS UNDERGOING MODERATE
WESTERLY SHEAR AND WITH DRY AIR ENTRAINING INTO THE CIRCULATION
LIMITING SCATTERED MODERATE/ISOLATED STRONG CONVECTION TO WITHIN
90 NM OF THE CENTER OVER THE E SEMICIRLCE. SHOWERS/ISOLATED
THUNDERSTORMS COVER THE AREA FROM 26N-35N BETWEEN 62W-71W. LARGE
SWELLS GENERATED BY HURRICANE KATIA WILL CONTINUE TO AFFECT MOST
OF THE EAST COAST OF THE UNITED STATES...BERMUDA... THE GREATER
ANTILLES...AND EAST FACING BEACHES OF THE BAHAMAS DURING THE
NEXT FEW DAYS. THESE SWELLS ARE LIKELY TO CAUSE LIFE THREATENING
SURF AND RIP CURRENT CONDITIONS. PLEASE CONSULT PRODUCTS ISSUED
BY LOCAL NATIONAL WEATHER SERVICE OFFICES FOR MORE INFORMATION.

TROPICAL STORM NATE IS CENTERED NEAR 20.4N 92.4W AT 08/0600 UTC
OR ABOUT 115 NM KM W-NW OF CAMPECHE MEXICO AND ABOUT 175 NM NE
OF COATZACOALCOS MEXICO MOVING E AT 2 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1003 MB. THE MAXIMUM SUSTAINED WIND SPEED IS
40 KT WITH GUSTS TO 50 KT. PLEASE SEE THE LATEST INTERMEDIATE
PUBLIC ADVISORY UNDER AWIPS/WMO HEADER MIATCPAT5/WTNT35 KNHC AND
THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT5/
WTNT25 KNHC FOR MORE DETAILS. NATE SHOWS LITTLE CHANGE OVER THE
PAST FEW HOURS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
REMAINS W OF THE CENTER OVER THE W BAY OF CAMPECHE S OF 21N TO
INLAND OVER MEXICO BETWEEN 93W-96W. SHOWERS/ISOLATED
THUNDERSTORMS ARE WITHIN 60 NM OF LINE FROM 23N84W TO 21N94W.

TROPICAL STORM MARIA IS CENTERED NEAR 13.4N 47.2W AT 08/0600 UTC
OR ABOUT 875 NM E-SE OF THE LEEWARD ISLANDS MOVING W AT 20 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED
WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. PLEASE SEE THE LATEST
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADER MIATCPAT4/
WTNT34 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO
HEADER MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. MARIA IS UNDER
SOUTHWESTERLY VERTICAL WIND SHEAR WITH SCATTERED STRONG
CONVECTION FROM 12N-17N BETWEEN 42W-46W AND FROM 13N-15N BETWEEN
47W-50W.

...TROPICAL WAVES...
TROPICAL WAVE IN THE E TROPICAL ATLC IS ALONG 26W/27W S OF 14N
WITH A 1011 MB LOW ALONG THE WAVE NEAR 9N MOVING W NEAR 15 KT.
WAVE IS EMBEDDED WITHIN AN AREA OF DEEP LAYER MOISTURE AS
DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY AND IS WELL
DEFINED IN THE UPPER LEVEL SATELLITE WINDS. SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS ARE FROM 11N-13N BETWEEN 24W-28W AND FROM
5N-8N BETWEEN 27W-31W.

TROPICAL WAVE IS IN THE W ATLC/NE CARIBBEAN ALONG 63W/64W S OF
22N MOVING W-NW 15-20 KT. WAVE IS EMBEDDED WITHIN AN AREA OF
DEEP LAYER MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER
IMAGERY. SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
ARE FROM 16N-22N BETWEEN 60W-67W.

...THE ITCZ/THE MONSOON TROUGH...
THE MONSOON TROUGH IS ANALYZED ACROSS AFRICA INTO THE E TROPICAL
ATLC NEAR 20N16W TO 15N19W. THE MONSOON TROUGH AND ITCZ AXIS HAS
BEEN DISRUPTED BY THE LACK OF CONFLUENCE IN THE TRADE WINDS AND
THE PRESENCE OF TROPICAL STORM MARIA. CLUSTERS OF SCATTERED
MODERATE CONVECTION ARE WITHIN 60/75 NM OF COAST OF W AFRICA
BETWEEN SIERRA LEONE AND THE S BORDER OF SENEGAL.

...DISCUSSION...

GULF OF MEXICO...
THE PRIMARY CONCERN FOR THE S GULF WATERS IF TROPICAL STORM
NATE...SEE SPECIAL FEATURES SECTION ABOVE. A SHARP UPPER TROUGH
EXTENDS FROM AN UPPER LOW OVER OHIO THROUGH GEORGIA ACROSS THE
FLORIDA PANHANDLE NEAR TALLAHASSEE INTO THE GULF ALONG 26N90W TO
W OF NATE NEAR 22N96W SUPPORTING A QUASI-STATIONARY FRONTAL
BOUNDARY THAT AT 08/0300 UTC ENTERS THE GULF WATERS NEAR TAMPA
FLORIDA TO 26N87W. SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS ARE WITHIN 90 NM EITHER SIDE OF THE FRONT. AN
UPPER RIDGE IS OVER THE SE GULF EXTENDING FROM NEAR NATE JUST N
OF THE YUCATAN TO ACROSS S FLORIDA ENHANCING THE SHOWER ACTIVITY
ASSOCIATED WITH NATE. VERY DRY AIR ALOFT IS W OF THE UPPER
TROUGH AXIS AND GIVING THE NW GULF REMARKABLE CLEAR SKIES
TONIGHT NW OF A LINE FROM APALACHICOLA BAY FLORIDA ALONG 26N91W
TO JUST N OF TUXPAN MEXICO. NATE IS EXPECTED TO REMAIN OVER THE
SOUTHWEST GULF WATERS AND BECOME A HURRICANE BY FRI EVENING
MAKING ITS WAY TO OFF THE COAST OF MEXICO NEAR TAMPICO BY MON
EVENING. STATIONARY FRONT WILL WEAKEN INTO A TROUGH OVER THE E
GULF LATER TODAY.

CARIBBEAN SEA...
WEAK UPPER FLOW DOMINATES THE CARIBBEAN. THE MONSOON TROUGH
EXTENDS ACROSS THE SW CARIBBEAN FROM COLOMBIA NEAR 10N75W ALONG
9N81W ACROSS CENTRAL AMERICA NEAR THE PANAMA/COSTA RICA BORDER
WITH SCATTERED SHOWERS/THUNDERSTORMS S OF A LINE FROM CENTRAL
NICARAGUA NEAR 13N84W TO COLOMBIA NEAR 11N74W. DRY STABLE AIR
ALOFT DOMINATES THE CENTRAL CARIBBEAN BETWEEN 70W-85W.
HOWEVER...AFTERNOON HEATING HAS GENERATED CLUSTERS OF SHOWERS/
THUNDERSTORMS INLAND OVER CUBA...JAMAICA...AND HISPANIOLA WITH
THESE STORMS CURRENTLY FROM 17N-21N BETWEEN 71W-79W. THIS IS
LEAVING THE REMAINDER OF THE CARIBBEAN UNDER REMARKABLY CLEAR
SKIES AGAIN TONIGHT WITH THE EXCEPTION OF THE SHOWER ACTIVITY
OVER THE NE CARIBBEAN ASSOCIATED WITH THE TROPICAL WAVE. MARIA
IS FORECAST TO APPROACH THE VIRGIN ISLANDS BY SAT NIGHT. THE
TROPICAL WAVE OVER THE NE CARIBBEAN WILL MOVE ACROSS THE N
CARIBBEAN THROUGH FRI.

ATLANTIC OCEAN...
A QUASI-STATIONARY FRONT ENTERS THE W ATLC NEAR 32N78W EXTENDING
ACROSS FLORIDA INTO THE GULF OF MEXICO NEAR DAYTONA BEACH
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90 NM
OF LINE FROM THE CENTRAL BAHAMAS NEAR 24N75W TO 31N80W. THE
UPPER RIDGE ASSOCIATED WITH HURRICANE KATIA IS UNDER THE
INFLUENCE OF THE WESTERLY SHEAR AND NOW COVERS THE AREA FROM
26N-35N BETWEEN 60W-72W. A CUTOFF UPPER LOW IS TO THE SE OF
KATIA CENTERED NEAR 24N58W GENERATING SHOWERS/THUNDERSTORMS FROM
21N-26N BETWEEN 56W-61W AND SCATTERED SHOWERS AND POSSIBLE
ISOLATED THUNDERSTORMS FROM 17N-21N BETWEEN 55W-61W. AN UPPER
TROUGH COVERS THE REMAINDER OF THE CENTRAL AND INTO E ATLC
BETWEEN 25W-47W N OF TROPICAL STORM MARIA SUPPORTING A SURFACE
TROUGH THAT EXTENDS FROM 31N36W TO 26N41W AND GENERATING
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM
27N-31N BETWEEN 31W-37W. A BROAD SURFACE RIDGE DOMINATES THE
ATLC N OF 20N BETWEEN 20W-60W WITH A WEAKNESS IN THE VICINITY OF
THE ABOVE SURFACE TROUGH. THE CENTER OF KATIA WILL MOVE N OF THE
AREA BY EARLY MORNING WITH TROPICAL STORM CONDITIONS CONTINUING
N OF 30N TODAY. SURFACE RIDGE WILL BUILD ACROSS THE AREA IN THE
WAKE OF KATIA THU THROUGH SAT. TROPICAL STORM MARIA WILL REACH
THE W ATLC SAT EVENING AND N OF THE TURKS AND CAICOS BY MON
NIGHT.

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

$$
PAW





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