[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 111049
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI JUL 11 2008

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1015 UTC.

...SPECIAL FEATURE....

THE CENTER OF HURRICANE BERTHA AT 11/0900 UTC IS NEAR 28.0N
61.7W. IT IS MOVING NORTHWEST OR 315 DEGREES 6 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 980 MB. THE MAXIMUM SUSTAINED WIND
SPEEDS ARE 75 KT WITH GUSTS TO 90 KT. THIS POSITION ALSO IS
305 NM/565 KM SOUTHEAST OF BERMUDA. PLEASE READ THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
AND THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE
DETAILS. SCATTERED STRONG SHOWERS AND THUNDERSTORMS ARE FROM 27N
TO 30N BETWEEN 59W AND 63W. BROKEN TO OVERCAST MULTILAYERED
CLOUDS AND OTHER POSSIBLE PRECIPITATION COVER THE AREA FROM 25N
TO 32N BETWEEN 55W AND 66W. FORECAST TRACK GUIDANCE IS IN GOOD
AGREEMENT THAT BERTHA WILL TURN NORTHWARD DURING THE NEXT
36 HOURS AS A MIDDLE LEVEL RIDGE TO THE NORTH OF THE HURRICANE
MOVES EASTWARD. BERTHA IS CURRENTLY UNDER A LARGE UPPER-LEVEL
ANTICYCLONE...WITH THE LARGE-SCALE MODELS FORECASTING THIS TO
CONTINUE FOR AT LEAST 36 HOURS. THE INTENSITY FORECAST WILL
KEEP BERTHA AT 75 KT DURING THIS TIME. A CHANCE OF SOME
STRENGTHENING AT THE END OF THE EYEWALL REPLACEMENT CYCLE STILL
EXISTS. IT IS EXPECTED THAT BERTHA WILL MOVE SLOWLY OUT FROM
UNDER THE ANTICYCLONE AND ENCOUNTER VERTICAL WIND SHEAR STARTING
IN 48 TO 72 HOURS. THIS AND DECREASING SEA SURFACE TEMPERATURES
ALONG THE FORECAST TRACK SHOULD CAUSE BERTHA TO WEAKEN. OCEAN
ANALYSES FROM THE ATLANTIC OCEANOGRAPHIC AND MARINE LABORATORY
SHOW THAT THE WARM WATER UNDER BERTHA IS RELATIVELY SHALLOW...
AND THERE IS A CHANCE THAT THIS SLOW-MOVING SYSTEM COULD UPWELL
COLDER WATER UNDERNEATH IT. THIS COULD PARTICULARLY BE A FACTOR
IF BERTHA STALLS FOR 24 HOURS OR MORE. THE LATEST WIND SPEED
PROBABILITIES INDICATE THAT...GIVEN UNCERTAINTIES IN THE
FORECASTS OF BERTHA'S TRACK...INTENSITY...AND SIZE...THERE
REMAINS ROUGHLY A 50% CHANCE THAT WINDS OF TROPICAL STORM FORCE
WILL AFFECT BERMUDA DURING THE NEXT FIVE DAYS. A TROPICAL STORM
WATCH MAY BE ISSUED FOR THE ISLAND LATER TODAY.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 39W/40W SOUTH OF 13N
MOVING WEST 15 KT. ITCZ PRECIPITATION IS CURVING NORTHWARD AT
THE NORTHERN END OF THE WAVE FROM 10N TO 12N BETWEEN 34W AND 42W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 65W/66W SOUTH OF 16N
MOVING WEST 15 KT. UPPER LEVEL ANTICYCLONIC FLOW COVERS THE
CARIBBEAN SEA AND THE ATLANTIC OCEAN FROM 9N TO 16N BETWEEN
55W AND 66W. BROKEN TO OVERCAST MIDDLE AND HIGH LEVEL CLOUDS
ARE SOUTH OF 16N BETWEEN 56W AND 70W. SHOWERS ARE POSSIBLE
IN THIS AREA.

...THE ITCZ...
11N15W 7N30W 8N51W 10N62W. SCATTERED MODERATE TO STRONG SHOWERS
AND THUNDERSTORMS FROM 6N TO 10N BETWEEN 15W AND 18W...AND WITHIN
45 NM ON EITHER SIDE OF 11N43W 8N43W 8N52W 6N53W. ISOLATED TO
WIDELY SCATTERED MODERATE SHOWERS AND POSSIBLE THUNDERSTORMS
FROM 11N TO 13N BETWEEN 17W AND 19W...FROM 2N TO 10N BETWEEN 20W
AND 36W...AND FROM 10N TO 12N BETWEEN 34W AND 42W. SHOWERS ARE
POSSIBLE ELSEWHERE SOUTH OF 10N BETWEEN 30W AND 42W.

...DISCUSSION...

THE GULF OF MEXICO...
MIDDLE TO UPPER LEVEL ANTICYCLONIC FLOW MOVES FROM THE ATLANTIC
OCEAN ALONG THE WESTERN SIDE OF THE FLOW AROUND THE 28N69W
MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER...ACROSS THE
NORTHERN BAHAMAS TO THE STRAITS OF FLORIDA...INTO THE GULF OF
MEXICO NORTH OF 23N...NORTHWESTWARD TO THE LOUISIANA/TEXAS
BORDER. THE MIDDLE LEVEL CYCLONIC CIRCULATION CENTER/TROUGH
FROM 24 HOURS AGO HAS MOVED ASHORE. IT NOW HUGS THE COASTAL
PLAINS OF TEXAS FROM 30N SOUTHWARD INTO THE LOWER TEXAS COAST/
EXTREME NORTHEASTERN COASTAL MEXICO. A SECOND CYCLONIC
CIRCULATION CENTER IS NEAR 21N94W IN THE SOUTHWESTERN CORNER OF
THE AREA. MIDDLE TO UPPER LEVEL DRY AIR IS NORTH OF THE 21N94W
CYCLONIC CENTER WEST OF 90W. ISOLATED MODERATE SHOWERS IN THE
SOUTHWESTERN CORNER OF THE AREA SOUTH OF 22N.

THE CARIBBEAN SEA...
BROAD UPPER LEVEL ANTICYCLONIC FLOW IS SOUTH OF 18N BETWEEN
68W AND CENTRAL AMERICA. ISOLATED MODERATE SHOWERS HAVE BEEN
ALTERNATELY DEVELOPING...DISSIPATING...AND POSSIBLY
RE-DEVELOPING IN THE WATERS AND LAND AREAS NORTH OF 17N BETWEEN
PUERTO RICO AND THE NORTHWESTERN CORNER OF THE CARIBBEAN SEA.
THIS PART OF THE CARIBBEAN SEA NORTH OF 17N IS AN AREA OF UPPER
LEVEL DIFFLUENT WIND FLOW...GIVEN THE UPPER LEVEL ANTICYCLONIC
FLOW IN THE EASTERN GULF OF MEXICO...THE UPPER LEVEL ANTICYCLONIC
FLOW IN THE CARIBBEAN SEA SOUTH OF 18N...AND THE 28N69W 25N74W
21N77W TROUGH. MIDDLE LEVEL CYCLONIC FLOW IS IN THE SOUTHWESTERN
CORNER OF THE AREA. STRONG SHOWERS AND THUNDERSTORMS ARE FROM
10N TO 14N BETWEEN 81W AND 83W AT THE COAST OF NICARAGUA. STRONG
SHOWERS AND THUNDERSTORMS IN NORTHEASTERN COLOMBIA EIGHT HOURS
AGO HAVE MOVED INTO THE GULF OF URABA SOUTH OF 10N BETWEEN
COLOMBIA AND PANAMA...TO THE WEST OF BROAD MIDDLE LEVEL CYCLONIC
FLOW.

THE ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM A 28N69W CYCLONIC
CIRCULATION CENTER TO 25N74W TO 21N77W IN EASTERN CUBA. BROAD
UPPER LEVEL ANTICYCLONIC FLOW IS SOUTH OF 18N BETWEEN 68W AND
CENTRAL AMERICA. ISOLATED MODERATE SHOWERS HAVE BEEN ALTERNATELY
DEVELOPING...DISSIPATING...AND POSSIBLY RE-DEVELOPING IN THE
WATERS AND LAND AREAS NORTH OF 17N BETWEEN PUERTO RICO AND THE
NORTHWESTERN CORNER OF THE CARIBBEAN SEA. CYCLONIC FLOW AROUND
THIS CENTER COVERS THE ATLANTIC OCEAN FROM 26N TO 32N BETWEEN
66W AND 73W. UPPER LEVEL ANTICYCLONIC OUTFLOW FROM HURRICANE
BERTHA IS MOVING ON TOP OF THE EASTERN EXTENSION OF THE CYCLONIC
FLOW AROUND THE 28N69W CENTER. A MIDDLE TO UPPER LEVEL TROUGH
EXTENDS FROM A CYCLONIC CIRCULATION CENTER NEAR 35N43W...ABOUT
1000 NM EAST-NORTHEAST OF HURRICANE BERTHA...THROUGH 32N44W TO
26N46W. A SURFACE TROUGH PASSES THROUGH 33N46W TO 31N47W.
ISOLATED TO WIDELY SCATTERED MODERATE SHOWERS ARE NORTH OF 28N
BETWEEN 40W AND 50W. A SURFACE RIDGE EXTENDS FROM A 1024 MB HIGH
PRESSURE CENTER NEAR 29N72W TO 28N ALONG THE FLORIDA EAST
COAST...ACROSS THE GULF OF MEXICO TO THE LOWER TEXAS COAST.
BROAD SURFACE ANTICYCLONIC WIND FLOW COVERS THE ATLANTIC OCEAN
FROM 16N TO 30N BETWEEN AFRICA AND 52W.

$$

MT





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