[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201148
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE SEP 20 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM RITA IS CENTERED NEAR 23.8N 80.4W...OR 100 MILES
ESE OF KEY WEST FLORIDA...AT 20/1200 UTC MOVING WNW AT 13 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED
WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
AND THE PUBLIC ADVISORY UNDER HEADERS MIATCPAT3/WTNT33 KNHC FOR
MORE DETAILS. RITA IS VERY CLOSE TO HURRICANE STATUS AS
INDICATED FROM DOPPLER RADAR VELOCITIES FROM KEY WEST.
CONVECTION SURROUNDING RITA HAS EXPANDED OVERNIGHT EXTENDING
FROM THE BAHAMA ISLANDS ACROSS S FLORIDA AND THE FLORIDA KEYS TO
OVER CUBA AND INTO THE GULF OF MEXICO. RITA CONTINUES TO
MAINTAIN STRONG CONVECTION TO THE E OF THE LOW-LEVEL CENTER. THE
UPPER LOW THAT WAS LOCATED BETWEEN JAMAICA AND THE CAYMAN
ISLANDS IS NO LONGER LIMITING OUTFLOW TO THE S OF RITA. NUMEROUS
STRONG CONVECTION IS FROM 23N-25N BETWEEN 78W-79.5W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION COVERS THE REMAINDER OF THE
AREA FROM 22N-26.5N BETWEEN 75.5W-83.5W. THE OUTFLOW PATTERN IS
BECOMING MORE UNIFORM AND RITA IS STILL EXPECTED TO STRENGTHEN
TO HURRICANE STATUS DURING THE DAY TODAY AS IT MOVES INTO THE
GULF OF MEXICO.

HURRICANE PHILIPPE IS CENTERED NEAR 18.8N 56.8W...OR 305 NM ENE
OF THE LEEWARD ISLANDS...AT 20/0900 UTC MOVING NNW AT 5 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 985 MB. MAXIMUM SUSTAINED
WIND SPEED IS 70 KT WITH GUSTS TO 85 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. PHILIPPE CONVECTIVE STRUCTURE HAS STRENGTHEN
EVEN MORE THIS MORNING AND REMAINS NNE/SSW. AN UPPER LEVEL RIDGE
LIES E OF THE STORM AND IS CAUSING THE OUTFLOW TO GOOD IN ALL
BUT THE W QUADRANT. NUMEROUS STRONG CONVECTION IS WITHIN 60 NM
OF LINE 18N57W-19.5N54.5W. SCATTERED MODERATE/STRONG CONVECTION
COVERS THE REMAINDER OF THE AREA WITHIN 150/175 NM OF LINE
14N58W-22N54W.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ALONG 27W/28W S OF 17N MOVING W 10 KT
WITH A WEAK 1013 MB LOW ALONG THE WAVE NEAR 10N. VERY WEAK
LOW-LEVEL CIRCULATION IS OBSERVED ON THE FIRST VISIBLE SATELLITE
IMAGES. NO ASSOCIATED DEEP CONVECTION.

CENTRAL ATLC TROPICAL WAVE IS ALONG 43W/44W S OF 17N MOVING W 10
KT. WAVE STILL HAS A WELL-DEFINED CURVATURE ON INFRARED
SATELLITE IMAGERY WITH THE ASSOCIATED CONVECTION BEING DRAWN NW
INTO THE LOW CENTER DESCRIBED BELOW.

A SURFACE TROUGH EXTENDS FROM 27N43W TO A 1014 MB LOW NEAR
19N47W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
150 NM OF LINE 15N40W-25N47W. THIS IS DUE TO THE UPPER
DIFFLUENCE FROM THE UPPER HIGH TIED TO PHILIPPE TO THE W.

W CARIBBEAN TROPICAL WAVE IS ALONG 82W/83W S OF 19N MOVING W 10
KT. WAVE IS WELL-DEFINED WITH CLUSTERS OF SCATTERED
MODERATE/STRONG CONVECTION WITHIN 75 NM EITHER SIDE OF THE WAVE
AXIS FROM 10N-14N.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N13W 10N25W...THEN ALONG 9N30W
13N42W...THEN ALONG 7N45W 11N62W. SCATTERED MODERATE/STRONG
CONVECTION IS ALONG THE COAST OF AFRICA FROM 4N-6.5N BETWEEN
9W-12W.

...DISCUSSION...

GULF OF MEXICO...
STRONG UPPER HIGH CONTINUES TO DOMINATE THE W GULF AND IS
BEGINNING TO SHIFT TO OVER CENTRAL TEXAS WITH ANTICYCLONIC FLOW
N OF 22N W OF 90W. THE STRONGEST SUBSIDENCE IS LOCATED NEAR THE
HIGH CENTER IN TEXAS...BUT DRY AIR STILL REMAINS OVER THE W
GULF. MOISTURE IS MOVING ACROSS THE E GULF THANKS TO T.S. RITA.
AN INVERTED UPPER TROUGH EXTENDS FROM THE NW CARIBBEAN AND THE
YUCATAN CHANNEL DIVIDING THE GULF BETWEEN THE UPPER HIGH
OVER TEXAS AND THE UPPER HIGH ASSOCIATED WITH T.S. RITA.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS AREA ALONG THE W COAST
OF MEXICO IN THE BAY OF CAMPECHE S OF 23N W OF 94W. THE AREA OF
FLORIDA S OF LAKE OKEECHOBEE TO OVER CUBA W OF 84W IS
EXPERIENCING SHOWERS/STRONG THUNDERSTORMS ASSOCIATED WITH THE
RAINBANDS OF T.S. RITA. CONDITIONS WILL CONTINUE TO DETERIORATE
THIS MORNING ACROSS FAR W CUBA AND INTO THE SE GULF AS THE
HEAVIEST CONVECTION MAKES ITS WAY ACROSS THE FLORIDA KEYS LATER
TODAY.

CARIBBEAN...
AN ELONGATED UPPER LEVEL TROUGH EXTENDS HAITI W N OF JAMAICA
OVER THE CAYMAN ISLANDS THEN NW THROUGH THE YUCATAN CHANNEL...
ON THE UNDERSIDE OF T.S. RITA. ISOLATED SHOWERS ARE S OF THE
UPPER TROUGH W OF 83W FROM THE YUCATAN CHANNEL INTO THE GULF OF
HONDURAS. N OF THE UPPER LOW IS EXPERIENCING SHOWERS/
THUNDERSTORMS OF THE RAINBANDS ASSOCIATED WITH T.S. RITA. AN
UPPER HIGH IS CENTERED OVER PANAMA WITH BROAD ANTICYCLONIC FLOW
REACHING N TO 16N AND THE ASSOCIATED UPPER DIFFLUENCE IS
FOSTERING THE CLUSTERS OF SHOWERS/THUNDERSTORMS S OF 14N W OF
75W TO THE COAST OF COSTA RICA AND NICARAGUA. RELATIVELY DRY AIR
REMAINS ENTRENCHED OVER THE AREA WITHIN 150 NM OF LINE FROM E
CARIBBEAN NEAR 14N62W-15N69W-TO OVER HISPANIOLA NEAR 20N74W.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE NE OF A LINE FROM
THE LEEWARD ISLANDS FROM MARTINIQUE NW TO THE MONA PASSAGE
STEMMING FROM HURRICANE PHILIPPE AND THE UPPER HIGH ASSOCIATED
WITH T.S. RITA.

ATLANTIC...
AN UPPER TROUGH IS DIGGING S OVER THE W ATLC N OF 30N W OF
BERMUDA BRINGING WITH IT DRY UPPER AIR. THIS IS FORMING AN
UPPER LEVEL SHEAR AXIS ALONG THE N PERIPHERY OF T.S. RITA FROM
30N77W-32N65W. AN UPPER LOW IN THE W/CENTRAL ATLC IS ROTATING W
NEAR 26N58W WITH MOISTURE WRAPPING AROUND THE CIRCULATION...AND
COMBINING WITH THE OUTFLOW OF HURRICANE PHILIPPE. THIS OUTFLOW
IS ALSO BEING ENHANCED BY AN UPPER RIDGE OVER THE TROPICS FROM
12N59W TO 24N46W. ELSEWHERE...AN UPPER LEVEL LOW IS CENTERED
JUST SE OF THE AZORES AND THE ASSOCIATED TROUGH DRAPING SW INTO
THE AREA ALONG 32N25W TO 26N39W. THE BELT OF WESTERLIES LIES
BETWEEN 16N-25N WITH JET ALONG 24N AS INDICATED BY THE
SATELLITE-DERIVED WINDS. A RIDGE AXIS LIES ALONG 15N ACROSS THE
E/CENTRAL ATLC THEN NE TO THE MAURITANIA/WESTERN SAHARA BORDER.
THE TROPICAL WAVE ALONG 43W/44W IS THE LEADING EDGE OF AN
EASTERLY SURGE AND HAS BROUGHT A PLUME OF SAHARAN DUST ACROSS
THE AREA FROM 13N-22N E OF 40W.

$$
WALLACE



This weather bulletin was brought to you by:
www.nashvilleweather.net