[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211241 AAA
TWDAT

TROPICAL WEATHER DISCUSSION...AMENDED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED SEP 21 200521

AMENDED TO INCLUDE CATEGORY FOUR INFORMATION

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...

...SATELLITE IMAGERY SUGGESTS THAT RITA HAS BECOME A CATEGORY
FOUR HURRICANE. SATELLITE IMAGERY SUGGESTS THAT RITA HAS
CONTINUED TO STRENGHTEN AND MAXIMUM SUSTAINED WINDS HAVE
INCREASED TO NEAR 135 MPH WITH HIGHER GUSTS.  RITA IS NOW A
CATEGORY FOUR HURRICANE ON THE SAFFIR-SIMPSON SCALE. A NOAA
PLANE WILL CHECK THE INTENSITY LATER THIS MORNING. SOME
ADDITIONAL STRENGTHENING IS POSSIBLE DURING THE NEXT 24 HOURS.

HURRICANE RITA IS CENTERED NEAR 24.4N 85.3W OR ABOUT 195 MILES
WEST OF KEY WEST FLORIDA AND 790 MILES EAST-SOUTHEAST OF CORPUS
CHRISTI TEXAS AT 21/1200 UTC MOVING WEST AT 12 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 948 MB. MAXIMUM SUSTAINED WIND SPEED
IS 125 KT WITH HIGHER GUSTS. 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 A CATEGORY 3...WHICH IS A MAJOR HURRICANE ON THE
SAFFIR-SIMPSON SCALE WITH A 25 NM WIDE EYE. OUTFLOW IS APPARENT
IN ALL QUADRANTS. HEAVY RAIN/THUNDERSTORMS CONTINUE TO SPREAD
OVER S FLORIDA AND W CUBA BUT WILL BE MOVING OUT LATER THIS
MORNING. NUMEROUS STRONG CONVECTION IS WITHIN 60 NM OF THE
CENTER IN THE NW QUADRANT AND WITHIN 90 NM OF THE CENTER IN THE
REMAINING QUADRANTS. SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION COVERS THE AREA WITHIN 150 NM OF LINE FROM THE NW
CARIBBEAN NEAR 21N86W TO 27N82W INCLUDING W CUBA AND S FLORIDA.

TROPICAL STORM PHILIPPE IS CENTERED NEAR 19.5N 57.5W OR 285 NM
ENE OF THE LEEWARD ISLANDS AT 21/0900 UTC MOVING N AT 4 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB. MAXIMUM SUSTAINED
WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. DEEP CONVECTION HAS INCREASED OVER THE PAST 6
HOURS WITH THE LOW LEVEL CENTER ON THE SW EDGE. UPPER LEVEL LOW
THAT WAS DOMINATING THE AREA IS MOVING W AWAY FROM PHILIPPE AND
DRAWING THE DRY UPPER AIR WITH IT. WESTERLY SHEAR CONTINUES OVER
PHILIPPE MAKING A RATHER UNFAVORABLE ENVIRONMENT. SCATTERED/
NUMEROUS STRONG CONVECTION IS WITHIN 60 NM OF LINE 18N54W
20N56.5W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERS
THE AREA FROM 17N-22N BETWEEN 52.5W-57.5W. CLUSTERS OF SIMILAR
CONVECTION TRAIL THE SYSTEM TO THE S FROM 13N19N BETWEEN
50W-60W.

...TROPICAL WAVES...

CENTRAL ATLC TROPICAL WAVE IS ALONG 35W S OF 16N MOVING W 10 KT.
SIGNATURE CURVATURE IS OBSERVED ON VISIBLE SATELLITE IMAGERY.
WAVE IS BENEATH THE E EDGE OF AN UPPER RIDGE WITH ENOUGH
DIFFLUENCE TO GENERATE A SMALL AREA OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM 12.5N-15N BETWEEN
33W-35.5W.

W ATLC TROPICAL WAVE IS ALONG 45W S OF 15N MOVING W 10 KT. WEAK
SIGNATURE CURVATURE IS OBSERVED ON INFRARED SATELLITE IMAGERY.
ASSOCIATED CONVECTION WITHIN THE ITCZ.

A 1014 MB LOW IS CENTERED NEAR 18N46W MOVING W 10 KT. THE LOW IS
BEING DRAWN INTO THE AREA SURROUNDING T.S. PHILIPPE. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 90 NM E OF THE LOW.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N10W 5N23W 7N33W 7N51W 11N65W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 5N-10N BETWEEN 41W-50W AND WITHIN 150 NM ALONG THE COAST OF
GUINEA AFRICA. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE
WITHIN 90 NM S OF THE AXIS FROM E OF 19W TO JUST INLAND OVER
LIBERIA AFRICA.

...DISCUSSION...

GULF OF MEXICO...
RITA CONTINUES TO DOMINATE THE WEATHER PICTURE THIS MORNING AS A
CAT 3 HURRICANE MOVING ACROSS THE SE GULF. RITA COULD CONTINUE
TO INTENSIFY FOR THE NEXT 24 HOURS AND REMAIN A MAJOR HURRICANE
NEAR LANDFALL. AT THE UPPER LEVELS...AN UPPER HIGH IS CENTERED
NEAR HURRICANE RITA WITH BROAD ANTICYCLONIC FLOW COVERING MOST
OF THE GULF AND THE W ATLC FROM 70W-93W. A SMALL UPPER MID/LOW
IS OVER THE SW GULF NEAR THE BAY OF CAMPECHE NEAR 22N95W WITH AN
INVERTED TROUGH EXTENDING N ALONG THE COAST OF MEXICO/TEXAS.
DRY AIR REMAINS OVER THE NW GULF ALONG THE TEXAS COAST. UPPER
LEVEL MOISTURE IS GENERATING ISOLATED SHOWERS OVER THE W GULF S
OF 26N W OF 94W. RITA WILL CONTINUE TO MOVE ACROSS THE GULF FOR
THE REMAINDER OF THE WEEK MAKING LANDFALL EARLY IN THE WEEKEND.
THE E GULF WILL CLEAR WITH PASSING OF RITA.

CARIBBEAN...
BROAD UPPER HIGH IS FIRMLY ESTABLISHED OVER THE SW CARIBBEAN
CENTERED ALONG THE COAST OF COLOMBIA NEAR 11N77W WITH FLOW
COVERING THE AREA S OF 17N W OF 69W. A WEAK 1010 MB LOW IS
ANALYZED NEAR 12N80W. TROPICAL MOISTURE IS BEING ADVECTED ACROSS
CENTRAL AMERICA OVER THE AREA AND GENERATING CLUSTERS OF
SCATTERED MODERATE/STRONG CONVECTION WITHIN 90 NM ALONG THE
COAST OF COLOMBIA...PANAMA...AND COSTA RICA. NUMEROUS STRONG
CONVECTION IS INLAND OVER NE VENEZUELA INCLUDING LAKE MARACAIBO.
AN UPPER SHEAR AXIS EXTENDS FROM HAITI ACROSS JAMAICA TO THE
GULF OF HONDURAS. SCATTERED SHOWERS/THUNDERSTORMS ARE S OF THE
AXIS FROM 14N-17N BETWEEN 78W-83W. THE NW CARIBBEAN IS UNDER THE
INFLUENCE OF HURRICANE RITA WITH AN UPPER RIDGE AXIS EXTENDING
SE ACROSS THE BAHAMAS TO OVER THE E CARIBBEAN TO NEAR 16N63W.
THIS IS GENERATING SCATTERED SHOWERS/THUNDERSTORMS OVER THE NE
CARIBBEAN N OF 15N E OF 70W TO OVER THE N LEEWARD AND VIRGIN
ISLANDS...PUERTO RICO AND TO THE COAST OF HISPANIOLA. AN INDUCED
UPPER INVERTED TROUGH IS OVER THE SE CARIBBEAN BETWEEN THE RIDGE
FROM ACROSS THE BAHAMAS AND THE UPPER HIGH SE OF T.S. PHILIPPE
FROM THE ABC ISLANDS TO OVER THE CENTRAL LESSER ANTILLES. WET
WEATHER SHOULD REMAIN OVER THE NE CARIBBEAN UNTIL THE WEEKS END
AS MOISTURE FROM PHILIPPE LINGERS AND OVER THE SW CARIBBEAN.

ATLANTIC...
UPPER HIGH IN ASSOCIATED WITH HURRICANE RITA IS GIVING THE W
ATLC OUTFLOW FROM THE STORM WITH BROAD ANTICYCLONIC FLOW W OF
70W. SCATTERED SHOWERS/THUNDERSTORMS ARE W OF 77W AND WILL
LINGER THROUGH THE MORNING HOURS THEN CLEAR AS RITA CONTINUES ON
ITS WESTWARD TRACK. AN UPPER LOW IS IN THE CENTRAL ATLC NEAR
23N62W PROVIDING W SHEAR AND DRY UPPER AIR TOWARD T.S. PHILIPPE.
DRY AIR AND MODERATE/STRONG SUBSIDENCE ARE WITHIN 100/150 NM OF
LINE FROM 22N58W 21N63W TO 23N68W THEN BROADENS TO WITHIN 200 NM
TO 30N68W AND ENCOMPASSES THE AREA N OF 30N W OF 55W TO OVER THE
SE UNITED STATES. THIS IS GIVING MOST OF THE W ATLC E OF THE
BAHAMAS TO NEAR 60W FAIR WEATHER. AN UPPER HIGH S OF PHILIPPE
NEAR 14N58W EXTENDS A RIDGE NE TO 32N48W PRODUCING BROAD AREA OF
DIFFLUENCE WITH SCATTERED SHOWERS/THUNDERSTORMS OVER THE AREA
FROM 20N-33N BETWEEN 46W-59W. A SURFACE TROUGH IS BENEATH THIS
AREA EXTENDING FROM 22N54W-32N50W. THIS IS DIVIDING THE
SUBTROPICAL RIDGE WITH A RIDGE AXIS OVER THE W ATLC EXTENDING
FROM A 1022 MB HIGH N OF BERMUDA SW TO THE S BAHAMA ISLANDS AND
A BROADER RIDGE OVER THE E ATLC FROM A 1026 MB HIGH NEAR 35N40W
SE TO 20N32W. OVER THE E ATLC...AN UPPER HIGH IS LOCATED W OF
THE CAPE VERDE ISLANDS NEAR 15N39W AND A SECOND E OF THE CAPE
VERDE ISLANDS OVER W AFRICA. THIS IS PRODUCING A COL OVER THE
ISLANDS THEMSELVES. AN UPPER TROUGH OVER THE NE ATLC EXTENDS
FROM AN UPPER LOW NEAR 34N20W SW TO 22N33W. THIS IS PRODUCING A
JET WITH WINDS OF 70-90 KT AROUND THE BASE OF THE UPPER TROUGH
THEN NE TO THE CANARY ISLANDS. YET ANOTHER SURGE OF AFRICAN DUST
IS MOVING OVER THE FAR E ATLC FROM 10N-25N W TO THE CAPE VERDES
TO 28W...THUS DRYING THE AREA.

$$
WALLACE/MT


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