[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 241810
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED AUG 24 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 1200 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 1745 UTC.

...SPECIAL FEATURES...
TROPICAL DEPRESSION TWELVE BECAME TROPICAL STORM KATRINA AT
24/1800 UTC. THE CENTER OF TROPICAL STORM KATRINA WAS NEAR
25.2N 77.0W OR ABOUT 30 MILES/50 KM EAST-NORTHEAST OF NASSAU
IN THE BAHAMAS...AND ABOUT 200 MILES/320 KM EAST-SOUTHEAST
OF THE SOUTHEASTERN COAST OF FLORIDA. IT WAS MOVING NORTHEAST
17 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE WAS 1001 MB.
THE MAXIMUM SUSTAINED WIND SPEEDS 45 KT WITH GUSTS TO 55 KT.
SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER HEADERS
MIATCPAT1/WTNT32 KNHC FOR MORE DETAILS. STRONG SHOWERS AND
THUNDERSTORMS ARE OCCURRING OVER THE BAHAMAS ISLANDS NORTH
OF 23N...SPECIFICALLY FROM 23N TO 27N BETWEEN 74W AND 78W.

AN ATLANTIC 1009 MB LOW PRESSURE CENTER WAS NEAR 19N41W MOVING
WEST ABOUT 10 KT. IT IS POSSIBLE THAT THIS FEATURE MAY BECOME
A TROPICAL CYCLONE DURING THE NEXT 24 HOURS. A TROPICAL WAVE
WITH THIS LOW CENTER IS ALONG 41W SOUTH OF 22N MOVING WEST
WITH THE WHOLE SYSTEM. NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS WERE FOUND FROM 18N TO 19N BETWEEN 38W AND
40W. UPPER LEVEL ANTICYCLONIC OUTFLOW COVERS THE NORTHERN
SEMICIRCLE OF THIS FEATURE ABOUT 200 NM AWAY FROM THE CENTER.

...TROPICAL WAVES...
ATLANTIC OCEAN TROPICAL WAVE WAS ALONG 26W/27W SOUTH OF 15N
MOVING WEST 10 TO 15 KT. WEAK CYCLONIC FLOW APPEARS TO BE
PRESENT IN THE LOW CLOUD FIELD ON VISIBLE SATELLITE IMAGERY
AS CLOUDS PASS OVER THE CAPE VERDE ISLANDS. THERE ARE NO
DEEP SHOWERS OR THUNDERSTORMS. ISOLATED MODERATE TO LOCALLY
STRONG SHOWERS AND THUNDERSTORMS FROM 11N TO 13N BETWEEN 39W
AND 42W...ISOLATED MODERATE SHOWERS FROM 15N TO 18N BETWEEN
36W AND 40W...AND FROM 13N TO 15N BETWEEN 40W AND 44W.

CARIBBEAN SEA TROPICAL WAVE WAS ALONG 20N67W 16N68W 10N69W
MOVING WEST 15 TO 20 KT. THIS WAVE IS MOVING TOWARD THE AREA
OF A MIDDLE TO UPPER LEVEL INVERTED TROUGH...WHICH IS
COMPARATIVELY NOT AS WELL-DEFINED AS IT WAS THREE TO FOUR DAYS
AGO. ISOLATED TO WIDELY SCATTERED MODERATE SHOWERS TO LOCALLY
STRONG THUNDERSTORMS COVERED THE CARIBBEAN SEA FROM 13N TO 21N
BETWEEN 64W AND 70W. ISOLATED MODERATE SHOWERS ARE CAUGHT UP ON
THE WESTERN SIDE OF THE INVERTED TROUGH FROM 14N TO 17N BETWEEN
70W AND 76W.

SOUTHWESTERN GULF OF MEXICO TROPICAL WAVE ALONG 92W/93W SOUTH
OF 21N MOVING WEST 10 KT. WEAKENING PRECIPITATION WITH WARMING
CLOUD TOP TEMPERATURES FROM THE MEXICO COAST TO 21N BETWEEN
94W AND 96W.

...THE ITCZ...
ITCZ 12N16W 8N20W 8N23W...8N27W 11N34W CURVING TOWARD THE
19N41W ATLANTIC LOW CENTER...IT GOES FROM THE 19N41W LOW CENTER
SOUTHWESTWARD TO 10N46W TO 8N50W 11N64W. ISOLATED MODERATE
SHOWERS TO LOCALLY STRONG THUNDERSTORMS FROM 8N TO 13N BETWEEN
53W AND 62W IN THE SOUTHEASTERN CORNER OF THE CARIBBEAN SEA.
ISOLATED TO WIDELY SCATTERED MODERATE SHOWERS TO LOCALLY STRONG
THUNDERSTORMS FROM 6N TO 8N BETWEEN 12W AND 19W...AND FROM 5N
TO 7N BETWEEN 23W AND 32W.

...DISCUSSION...
THE GULF OF MEXICO...
THE SURFACE PRESSURE GRADIENT IS WEAK...WITH ONLY THE 1012 MB
ISOBAR MEANDERING FROM THE YUCATAN CHANNEL NORTHWESTWARD TO THE
MIDDLE TEXAS COAST. ALL THIS IS IN ADVANCE OF THE ARRIVAL OF
TROPICAL STORM KATRINA...STILL OVER THE BAHAMAS ISLANDS. AN
UPPER LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR SOUTHEASTERN
LOUISIANA. UPPER LEVEL ANTICYCLONIC WIND FLOW AROUND THIS CENTER
EASILY REACHES THE GULF WATERS AS FAR AS 22N/23N. ISOLATED
MODERATE SHOWERS TO LOCALLY STRONG THUNDERSTORMS ARE SEEN FROM
27N TO 29N BETWEEN 84W AND 86W IN THE NORTHEASTERN CORNER OF
THE AREA...AND IN THE NORTH CENTRAL GULF WATERS JUST SOUTH OF
LOUISIANA FROM 28N NORTHWARD TO THE COAST BETWEEN 90W AND 93W.
OTHER ISOLATED MODERATE SHOWERS ARE CAUGHT UP IN THE SURFACE
TRADEWIND FLOW.

THE CARIBBEAN SEA...
A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS INLAND
OVER SOUTHERN NICARAGUA...PROBABLY HELPING THE SHOWERS AND
THUNDERSTORMS IN THE SOUTHWESTERN CARIBBEAN WATERS FROM 10N
TO 12N BETWEEN 81W AND 82W. THE MIDDLE TO UPPER LEVEL INVERTED
TROUGH...TOWARD WHICH THE 66W/69W TROPICAL WAVE IS MOVING...
RUNS FROM THE SOUTHEASTERN DOMINICAN REPUBLIC TO 14N73W TO THE
GULF OF URABA OF NORTHERN COLOMBIA. SHOWERS AND THUNDERSTORMS
FROM 10N TO 21N BETWEEN 63W AND 76W ARE IN THE VICINITY OF THE
66W/69W TROPICAL WAVE AND NEAR THE MIDDLE TO UPPER LEVEL
INVERTED TROUGH.

THE ATLANTIC OCEAN...
TROPICAL STORM KATRINA WAS SPREADING SHOWERS AND THUNDERSTORMS
IN THE BAHAMAS FROM 23N TO 27N BETWEEN 74W AND 78W. A MIDDLE TO
UPPER LEVEL TROUGH RUNS FROM VERMONT AND NEW HAMPSHIRE TO
SOUTHEASTERN COASTAL VIRGINIA. UPPER LEVEL ANTICYCLONIC FLOW IS
ADJACENT AND TO THE EAST AND SOUTHEAST OF THIS TROUGH. AN EAST-
TO-WEST ORIENTED RIDGE RUNS ALONG 30N/31N REACHING 72W FROM
AROUND 50W. A SURFACE RIDGE RUNS THROUGH 33N43W TO 29N47W TO
30N65W TO 31N78W. A MIDDLE TO UPPER LEVEL TROUGH RUNS FROM
36N47W TO 31N46W. A MIDDLE TO UPPER LEVEL TROUGH RUNS FROM A
33N21W CYCLONIC CIRCULATION CENTER TO 30N34W TO 28N40W.

$$
MT


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