[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231807
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN AUG 23 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1630 UTC.

...SPECIAL FEATURES...
AS OF 23/1800 UTC...THE CENTER OF HURRICANE BILL IS NEAR 44.4N
62.5W OR ABOUT 60 MILES...95 KM...EAST-SOUTHEAST OF HALIFAX NOVA
SCOTIA. BILL IS MOVING TO THE NE NEAR 29 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 970 MB. MAXIMUM SUSTAINED WIND
SPEEDS ARE 70 KT WITH GUSTS TO 85 KT. PLEASE READ THE
FORECAST/ADVISORY UNDER AFOS/ WMO HEADERS TCMAT3/WTNT23 KNHC AND
THE PUBLIC ADVISORY UNDER TCPAT3/WTNT33 KNHC FOR MORE DETAILS.
NUMEROUS SHOWERS/THUNDERSTORMS ARE FROM 41N-49N BETWEEN 53W-65W
TO THE NE OF THE CENTER OF BILL.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 21W S OF 17N MOVING W 10-15 KT. VISIBLE
SATELLITE IMAGERY AND SATELLITE DERIVED WINDS INDICATE GOOD
LOW/MID-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS.
THIS WAVE ALSO COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM
OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 10N-16N BETWEEN
23W-27W. SIMILAR ACTIVITY IS FROM 14N-16N BETWEEN 18W-20W.

A TROPICAL WAVE EXTENDS FROM 17N51W TO 9N48W MOVING W 20-25 KT.
AN INVERTED-V FEATURE IS APPARENT IN THE LOW-LEVEL CLOUD
STRUCTURE IN VISIBLE SATELLITE IMAGERY. THE WAVE ALSO COINCIDES
WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 14N-15N BETWEEN 45W-54W.

A TROPICAL WAVE IS ALONG 68W S OF 18N MOVING W NEAR 15 KT. WAVE
POSITION IS BASED MAINLY ON CONTINUITY. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 11N-13N BETWEEN
67W-72W.

THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 11N14W 13N22W 9N33W 15N48W
12N56W 11N64W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
FROM 13N-18N BETWEEN 14W-18W. SIMILAR ACTIVITY IS FROM 10N-12N
BETWEEN 60W-64W.

...DISCUSSION...

THE GULF OF MEXICO...
A COLD FRONT DIPS ACROSS THE N AND CENTRAL GULF EXTENDING FROM N
FLORIDA NEAR 31N81W TO 25N88W AND UP TO THE TEXAS COAST TO NEAR
29N95 WHERE IT CONTINUES AS A STATIONARY FRONT INTO N TEXAS. THE
FRONT IS SUPPORTED BY AN UPPER LEVEL TROUGH ACROSS THE ERN CONUS
WHICH EXTENDS INTO THE NRN GULF TO NEAR 24N92W.
SHOWERS/THUNDERSTORMS ARE WITHIN 100 NM EITHER SIDE OF THE
FRONT. A WEAK 1015 MB SURFACE HIGH IS IN THE SW GULF NEAR
25N94W. AN 1148 UTC QUIKSCAT PASS CONFIRMED THE LOCATION OF THE
HIGH. A SMALL UPPER LEVEL LOW IS OVER THE YUCATAN PENINSULA NEAR
19N93W SUPPORTING A FEW ISOLATED SHOWERS/THUNDERSTORMS IN THE
SRN BAY OF CAMPECHE S OF 20N W OF 93W. EXPECT THE COLD FRONT TO
DISSIPATE TONIGHT AS A RIDGE BUILDS BACK ACROSS THE AREA.

THE CARIBBEAN SEA...
A BROAD UPPER LEVEL RIDGE DOMINATES THE CARIBBEAN CENTERED OVER
HAITI NEAR 20N73W. UPPER LEVEL DIFFLUENCE BETWEEN THIS RIDGE AND
THE UPPER LEVEL LOW OVER THE YUCATAN PENINSULA NEAR 19N93W IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS IN THE SW CARIBBEAN S
OF 16N W OF 80W INCLUDING PORTIONS OF COSTA RICA AND NICARAGUA.
SHOWERS/THUNDERSTORMS ARE ALONG THE SE CARIBBEAN ASSOCIATED WITH
THE TROPICAL WAVE ALONG 68W...SEE ABOVE. MODERATE TO FRESH
TRADEWINDS ARE ACROSS MUCH OF THE BASIN WITH STRONGER WINDS IN
THE E CARIBBEAN AND NEAR THE COAST OF COLOMBIA. EXPECT THE WAVE
ALONG 68W TO MOVE WWD ACROSS THE CENTRAL CARIBBEAN LATER TONIGHT.

THE ATLANTIC OCEAN...
A COLD FRONT ACROSS NRN FLORIDA EXTENDS TO A 1010 MB SURFACE LOW
IN COASTAL SOUTH CAROLINA NEAR 33N80W. SCATTERED
SHOWERS/THUNDERSTORMS ARE WITHIN 250 NM AHEAD OF THE FRONT
AFFECTING THE FLORIDA PENINSULA AND THE FAR NW BAHAMAS. THIS
ACTIVITY IS ALSO SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN THE
STRONG UPPER LEVEL TROUGH OVER THE ERN CONUS AND AN UPPER LEVEL
RIDGE THAT EXTENDS FROM AN UPPER LEVEL HIGH OVER HAITI NEAR
20N73W. TO THE E OF THE RIDGE A STRONG UPPER LEVEL LOW IS
CENTERED NEAR 25N56W AND IS SUPPORTING ISOLATED SHOWERS/POSSIBLE
THUNDERSTORMS FROM 20N-29N BETWEEN 50W-62W. ELSEWHERE ACROSS THE
ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1028 MB
HIGH NEAR 36N47W. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL HIGH
IS CENTERED NEAR 18N39W ENHANCING CONVECTION ALONG THE TROPICAL
WAVE NEAR 50W.

$$
WALTON





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