[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 191208
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON SEP 19 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 22.8N 74.6W...OR 235 MILES
SE OF NASSAU BAHAMAS...AT 19/1200 UTC MOVING W AT 8 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED
WIND SPEED IS 50 KT WITH GUSTS TO 60 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. DEEP CONVECTION CONTINUES TO EVOLVE AROUND RITA.
ASSOCIATED UPPER LEVEL RIDGE IS ORIENTED NW/SE ON THE NE SIDE OF
THE SYSTEM. THE LOW-LEVEL CIRCULATION IS AGAIN PARTIALLY EXPOSED
AND IS EMBEDDED BENEATH THE DEEPEST CONVECTION. SCATTERED STRONG
CONVECTION IS WITHIN A 30 NM RADIUS OF 23N75W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION COVERS THE AREA FROM
21N-26.5N BETWEEN 70W-77W INCLUDING MOST OF THE BAHAMA ISLANDS
SAVE FOR ANDROS...ABACO...AND GRAND BAHAMA.

HURRICANE PHILIPPE IS CENTERED NEAR 17.1N 56.0W...OR 335 NM E OF
THE LEEWARD ISLANDS...AT 19/0900 UTC MOVING N AT 6 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED WIND SPEED
IS 65 KT WITH GUSTS TO 80 KT. SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.
PHILIPPE IS EMBEDDED BENEATH A BROAD AREA OF UPPER LEVEL RIDGING
WITH THE PATTERN BECOMING BETTER ESTABLISHED ENOUGH FOR OUTFLOW
TO EXPAND IN ALL BUT THE W QUADRANT. SCATTERED/NUMEROUS STRONG
CONVECTION IS WITHIN 45/60 NM RADIUS OF 17N56W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION COVERS THE REMAINDER OF THE
AREA FROM 14N-20N BETWEEN 52W-58W.

A 1009 MB LOW IS LOCATED IN THE CENTRAL ATLC NEAR 12N38W...ALONG
A TROPICAL WAVE LOCATED ALONG 38W/39W S OF 24N MOVING W NEAR 10
KT. THE WAVE REMAINS QUITE SHARP AND IS PRODUCING DEEP
CONVECTION NEAR ITS N END AS WELL AS E AND N OF THE LOW-LEVEL
CENTER. AN UPPER LEVEL RIDGE AXIS IS EXPECTED TO REMAIN BETWEEN
12N-15N AND THIS WILL PROVIDE A FAVORABLE ENVIRONMENT FOR
TROPICAL CYCLONE DEVELOPMENT WITHIN THE NEXT 24 TO 36 HOURS.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF
37W FROM 10.5N-14N AND FROM 14N-18N BETWEEN 34W-42W. SCATTERED
MODERATE CONVECTION IS FROM 21N-26N BETWEEN 33W-38W.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ALONG 25W S OF 18N MOVING W 10-15 KT.
A LOW-AMPLITUDE CIRCULATION APPEARS ON VISIBLE SATELLITE IMAGERY
S OF THE CAPE VERDE ISLANDS AND SHOWS AN ABUNDANCE OF AFRICAN
DUST COVERING THE AREA THUS LIMITING ANY DEEP CONVECTION
ASSOCIATED WITH THIS WAVE. SCATTERED SHOWERS/THUNDERSTORMS ARE
WITHIN 150 NM E OF THE WAVE S OF 14N AND THE CAPE VERDE ISLANDS.

SEE SPECIAL FEATURES FOR TROPICAL WAVE/LOW ALONG 38W/39W.

CENTRAL CARIBBEAN TROPICAL WAVE IS ALONG 77W S OF 20N MOVING W
10 KT. THE LOW-LEVEL CLOUD FIELD IN THE CARIBBEAN INDICATES A
WEAK APEX BETWEEN HAITI AND JAMAICA...BUT THERE IS LITTLE TO NO
MOISTURE AVAILABLE FOR MARITIME SHOWERS/THUNDERSTORMS. CLUSTERS
OF NUMEROUS STRONG CONVECTION ARE S OF 12N E OF 82W TO INLAND
OVER COLOMBIA AND PANAMA.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 16N17W 12N23W...THEN ALONG 8N27W
15N36W 15N43W 16N53W. MOST OF THE CONVECTION IS ASSOCIATED WITH
THE TROPICAL WAVES AND HURRICANE PHILIPPE. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 16N-19N BETWEEN 60W AND THE
LEEWARD ISLANDS AND WITHIN 30/45 NM OF LINE 11.5N57W TO OVER
TRINIDAD.

...DISCUSSION...

GULF OF MEXICO...
STRONG UPPER HIGH REMAINS ANCHORED ALONG THE N GULF COAST NEAR
TEXAS/LOUISIANA BORDER ENCOMPASSING THE AREA FROM MEXICO TO
FLORIDA...N OF THE YUCATAN PENINSULA AND THE BAY OF CAMPECHE TO
OVER THE SE UNITED STATES. THIS CONTINUES TO ADVECT A LARGE
AREA OF DRY SUBSIDING AIR OVER THE GULF WATERS AND ADJACENT LAND
AREAS. CLOUD COVER IS VIRTUALLY NON-EXISTENT EXCEPT S OF 20N
WHERE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS CONTINUE TO
GENERATE THIS MORNING MOVING ACROSS THE BAY OF CAMPECHE. HAZY
CONDITIONS HAVE CLEARED OVER FLORIDA BUT REMAIN OVER THE GEORGIA
COAST WHERE AN MEANDERING STATIONARY FRONT EXTENDS ACROSS SE
GEORGIA AND THE N GULF COAST FROM TALLAHASSEE TO THE
MISSISSIPPI/LOUISIANA BORDER. MOISTURE WILL BEGIN TO INCREASE
LATE TODAY INTO TUE WITH THE ARRIVAL OF T.S. RITA INTO THE
STRAITS OF FLORIDA.

CARIBBEAN...
A LARGE AND NEARLY STATIONARY UPPER LEVEL LOW IS CENTERED NEAR
THE CAYMAN ISLANDS NEAR 20N80W WITH ITS CIRCULATION EXTENDING
FROM THE STRAITS OF FLORIDA S TO THE GULF OF HONDURAS BETWEEN
HAITI AND THE YUCATAN PENINSULA. DEEP MOISTURE IS BEING ADVECTED
E ON THE UNDERSIDE OF THE LOW...AND THE MOST CONVECTION OVER THE
SW CARIBBEAN ASSOCIATED WITH A TROPICAL WAVE. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS AREA S OF THE UPPER LOW FROM
15N-21N BETWEEN THE WINDWARD PASSAGE AND THE COAST OF THE
YUCATAN PENINSULA. AN UPPER LEVEL COL IS CENTERED OVER THE
E/CENTRAL CARIBBEAN WITH AN AREA OF MODERATE/STRONG SUBSIDENCE
LOCATED BETWEEN 63W-73W. CONDITIONS WERE DRY OVER THE LESSER
ANTILLES BUT SHOWERS/THUNDERSTORMS ARE MOVING OVER THE LEEWARD
ISLANDS AHEAD OF HURRICANE PHILIPPE AND BEING DRAWN N OF THE
VIRGIN ISLANDS TOWARD T.S. RITA.

WEST/CENTRAL ATLANTIC...
AN INVERTED UPPER LEVEL TROUGH...AN EXTENSION OF THE UPPER LOW
NEAR THE CAYMAN ISLANDS...STRETCHES ACROSS W/CENTRAL CUBA
BETWEEN N BAHAMAS AND FLORIDA...JUST AHEAD OF T.S. RITA.
ABUNDANT DRY AIR IS MOVING FROM NE TO SW FROM THE NW ATLC ACROSS
FLORIDA...BUT THIS FEATURE APPEARS TO BE ISOLATING THE DRIEST AIR
AWAY FROM RITA. A WEAK UPPER LEVEL HIGH IS E OF RITA NEAR 23N71W
WITH A MODERATE OUTFLOW JET EXTENDING ALONG 23N/24W E INTO THE
CENTRAL ATLC N OF PHILIPPE. AN UPPER LEVEL SHEAR AXIS LIES N OF
THIS JET ALONG 28N73W 25N60W 25N51W AND SEPARATES THE UPPER
MOISTURE OF RITA FROM DRY AIR ON THE S SIDE OF A LARGE UPPER
HIGH CENTERED NEAR 37N48W. A SURFACE TROUGH IS LOCATED ABOUT 375
NM E OF RITA AND ALTHOUGH IT IS UNDER STRONG WESTERLY SHEAR FROM
THE OUTFLOW JET IS AIDING IN THE LINE OF SHOWERS/THUNDERSTORMS
FROM THE VIRGIN ISLANDS NEAR 19N64W TO 22.5N68.5W. ELSEWHERE...A
LARGE UPPER HIGH IS OVER PHILIPPE NEAR 16N55W WITH THE BEST
OUTFLOW IN ALL BUT THE W QUADRANT.

EAST ATLANTIC...
AN UPPER LEVEL RIDGE STRETCHES ACROSS THE TROPICS ALONG 15N/16N
FROM PHILIPPE E TO THE CAPE VERDE ISLANDS AND IS PROVIDING A
RELATIVELY LOW SHEAR ENVIRONMENT BETWEEN 10N-20N...THE MAIN BELT
OF TROPICAL WAVE PROGRESSION. STRONGER UPPER LEVEL WESTERLIES
ARE LOCATED N OF 20N...AND THIS PATTERN MAY FOSTER ADDITIONAL
TROPICAL CYCLONE DEVELOPMENT OVER THE NEXT SEVERAL DAYS IN THE E
ATLC. AN UPPER LEVEL TROUGH IS LOCATED FARTHER N FROM AN UPPER
LOW JUST S OF THE AZORES SW ALONG 29N38W TO A DEVELOPING UPPER
LOW NEAR THE N PORTION OF THE TROPICAL NEAR 25N39W.

$$
WALLACE



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