[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 082351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

HURRICANE KATIA IS CENTERED NEAR 34.9N 69.6W AT 08/2100 UTC OR
ABOUT 330 MI...530 KM NW OF BERMUDA MOVING N AT 14 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 973 MB. MAXIMUM SUSTAINED WIND SPEED
IS 70 KT WITH GUSTS TO 85 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. LARGE SWELL 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. THIS
SWELL IS LIKELY TO CAUSE LIFE THREATENING SURF AND RIP CURRENT
CONDITIONS. PLEASE CONSULT PRODUCTS ISSUED BY LOCAL NATIONAL
WEATHER SERVICE OFFICES FOR MORE INFORMATION. GLOBAL MODELS
INDICATE THAT KATIA WILL REMAIN A POWERFUL CYCLONE OVER THE NEXT
DAY OR SO. THE FORECAST TAKES THE REMNANTS OF KATIA NORTH OF THE
BRITISH ISLES IN ABOUT FOUR DAYS. SCATTERED MODERATE CONVECTION
IS FROM 33N-38N BETWEEN 67W-72W.

TROPICAL STORM NATE IS CENTERED NEAR 19.7N 92.2W AT 09/0000 UTC
OR ABOUT 110 MI...180 KM W OF CAMPECHE MEXICO...OR ABOUT 175
MI...285 KM NE OF COATZACOALCOS MEXICO...AND IS STATIONARY.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB. THE MAXIMUM
SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 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. THE
OUTER CONVECTION FROM NATE ALSO COVERS IMMEDIATE COASTAL WATERS
OF THE EASTERN COAST OF THE YUCATAN PENINSULA. NATE IS CURRENTLY
LOCATED IN AN ENVIRONMENT OF LIGHT TO MODERATE NORTHEASTERLY
SHEAR. NATE IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS OF 2
TO 4 INCHES WITH ISOLATED MAXIMUM AMOUNTS OF 8 INCHES OVER THE
MEXICAN STATES OF CAMPECHE... TABASCO...AND SOUTHERN VERACRUZ. A
STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS 1 TO 3 FEET
ABOVE NORMAL TIDE LEVELS ALONG THE IMMEDIATE COAST IN THE
WARNING AREA. THE SHEAR IS FORECAST TO LESSEN DURING THE NEXT
DAY OR SO...WHICH SHOULD ALLOW FOR GRADUAL STRENGTHENING.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION REMAINS S OF
THE CENTER OVER THE W BAY OF CAMPECHE TO INLAND OVER MEXICO S OF
21N BETWEEN 91W-95W.

TROPICAL STORM MARIA IS CENTERED NEAR 13.2N 53.6W AT 09/0000 UTC
OR ABOUT 490 MI...790 KM E OF THE WINDWARD ISLANDS MOVING W AT
19 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 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 SOUTH OF A PERSISTENT AND LARGE SUBTROPICAL RIDGE THAT
EXTENDS WESTWARD ACROSS THE ATLC. THIS STEERING PATTERN CALLS
FOR A WEST TO WEST-NORTHWEST TRACK OVER THE NEXT TWO TO THREE
DAYS. AFTER THAT...A WEAKER RIDGE NORTH OF THE CYCLONE IS
EXPECTED TO ALLOW A MORE NORTHWESTWARD TRACK AT A SOMEWHAT
SLOWER FORWARD SPEED. GUIDANCE IS IN VERY GOOD AGREEMENT...AND
MOST OF THE MODELS ARE CLUSTERED HAVING MARIA OVER OR JUST TO
THE NORTH OF THE CENTRAL BAHAMAS IN FIVE DAYS. SCATTERED
MODERATE TO STRONG CONVECTION IS FROM 12N-16N BETWEEN 48W-54W.

...TROPICAL WAVES...

TROPICAL WAVE IS W OF CAPE VERDE ISLANDS FROM 18N27W TO 8N29W
MOVING W 10-15 KT. THE WAVE IS EMBEDDED WITHIN AN AREA OF DEEP
LAYER MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER
IMAGERY AND IS WELL DEFINED IN THE LOW LEVEL CLOUD FIELD ON
SATELLITE IMAGERY. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
ARE WITHIN 120 NM ON EITHER SIDE OF THE WAVE AXIS.

TROPICAL WAVE IS OVER E HISPANIOLA FROM 23N68W TO 13N68W MOVING
WNW 15-20 KT. THE WAVE IS EMBEDDED WITHIN AN AREA OF DEEP LAYER
MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE CONVECTION IS E OF THE WAVE AXIS FROM 17N-24N
BETWEEN 64W-68W. ISOLATED MODERATE CONVECTION IS W OF THE WAVE
AXIS FROM 14N-20N BETWEEN 69W-72W.

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

THE MONSOON TROUGH IS ANALYZED OVER AFRICA INTO THE E TROPICAL
ATLC ACROSS THE NORTHERN COAST OF MAURITANIA NEAR 21N16W TO
18N21W. THE MONSOON TROUGH AND ITCZ AXIS HAS BEEN DISRUPTED OVER
THE REMAINDER OF THE TROPICAL ATLANTIC DUE TO THE LACK OF
CONFLUENCE IN THE TRADE WINDS AND THE PRESENCE OF TROPICAL STORM
MARIA. ISOLATED MODERATE CONVECTION IS OFF THE COAST OF WEST
AFRICA FROM 4N-7N BETWEEN 11W-16W. SIMILAR CONVECTION IS FROM
5N-9N BETWEEN 36W-41W.

...DISCUSSION...

GULF OF MEXICO...
THE PRIMARY CONCERN TONIGHT IS TROPICAL STORM NATE...SEE SPECIAL
FEATURES SECTION ABOVE. AS OF 2100 UTC...THE TAIL END OF A
DISSIPATING STATIONARY FRONT EXTENDS FROM N FLORIDA TO THE
E GULF OF MEXICO ALONG 28N80W 26N86W. SCATTERED SHOWERS ARE
WITHIN 120 NM OF THE FRONT. RADAR IMAGERY SHOWS SCATTERED
SHOWERS AND RAIN OVER THE SE GULF OF MEXICO FROM 25N-28N BETWEEN
27W-82W. FAIR WEATHER IS NOTED OVER THE NW GULF AND TEXAS DUE TO
UPPER LEVEL DRY AIR SUBSIDENCE. IN THE NEXT 24 HOURS EXPECT NATE
TO REMAIN IN THE BAY OF CAMPECHE AND GRADUALLY INTENSIFY. ALSO
EXPECT THE FRONT TO DISSIPATE AND BE REPLACED BY A SURFACE
TROUGH.

CARIBBEAN SEA...
A TROPICAL WAVE IS OVER THE LESSER ANTILLES. SEE ABOVE.
ELSEWHERE...WIDELY SCATTERED MODERATE CONVECTION IS NOTED INLAND
OVER PORTIONS OF NW VENEZUELA...AND N COLOMBIA. SIMILAR
CONVECTION IS OVER CENTRAL AMERICA FROM PANAMA TO S GUATEMALA.
ISOLATED MODERATE CONVECTION IS OVER THE HIGHER ELEVATIONS OF
HISPANIOLA...JAMAICA...AND CUBA. THE REMAINDER OF THE CARIBBEAN
IS UNDER UPPER LEVEL DRY AIR SUBSIDENCE BRINGING FAIR WEATHER
CONDITIONS. 10-20 KT TRADEWINDS DOMINATE THE CARIBBEAN WITH THE
HIGHEST WINDS ALONG THE COAST OF N  COLOMBIA. EXPECT OVER THE
NEXT 24 HOURS FOR THE TROPICAL WAVE TO MOVE W TO THE CENTRAL
CARIBBEAN. ALSO EXPECT ADDITIONAL CONVECTION TO BE OVER THE SW
CARIBBEAN DUE TO THE MONSOON TROUGH...AND OVER THE YUCATAN
PENINSULA DUE TO NATE.

ATLANTIC OCEAN...
TROPICAL STORM MARIA...AND THE TWO TROPICAL WAVES ARE THE
DOMINANT WEATHER PRODUCERS IN THE TROPICAL ATLANTIC. A
DISSIPATING STATIONARY FRONT IS OVER THE W ATLANTIC FROM 31N75W
TO 28N80W. SCATTERED SHOWERS ARE WITHIN 60 NM OF THE FRONT. A
1023 MB HIGH IS CENTERED OVER THE WESTERN ATLANTIC NEAR 33N55W.
A SURFACE TROUGH IS OVER THE CENTRAL ATLANTIC FROM 31N34W TO
26N40W PRODUCING SIGNIFICANT WIND SHIFTS AND NO CONVECTION.
TROPICAL STORM WATCH AND WARNINGS HAVE BEEN ISSUED FOR PORTIONS
OF THE LEEWARD ISLANDS DUE TO MARIA.

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

$$
FORMOSA





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