[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 200014
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT JUL 19 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2345 UTC.

...SPECIAL FEATURES...

THE CENTER OF HURRICANE BERTHA AT 19/2100 UTC IS NEAR 44.8N
43.3W MOVING NORTHEAST OR 35 DEGREES 22 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 989 MB. THE MAXIMUM SUSTAINED WIND
SPEEDS ARE 65 KT WITH GUSTS TO 80 KT. 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. BERTHA IS RETAINING HURRICANE INTENSITY EVEN AS IT
CONTINUES TO PLOW WELL NORTH OF 40 DEGREES LATITUDE AND MOVING
OVER COOLER SEA-SURFACE TEMPERATURES. HOWEVER THESE FACTORS WILL
SOON TAKE THEIR TOLL AND BERTHA IS EXPECTED TO BECOME AN
EXTRATROPICAL CYCLONE WITHIN 24 HOURS AND THEN BE ABSORBED BY A
LARGER SYSTEM IN LESS THAN THREE DAYS. THUS FAR BERTHA'S LONG
LIFE...16.75 DAYS AS A TROPICAL CYCLONE MAKES BERTHA BY SEVERAL
DAYS THE LONGEST LIVED JULY TROPICAL CYCLONE.

TROPICAL STORM CRISTOBAL AT 19/2100 UTC IS NEAR 33.0N 77.9W OR
ABOUT 125 MILES/195 KM...EAST OF CHARLESTON SOUTH CAROLINA AND
ABOUT 205 MILES/330 KM...SOUTHWEST OF CAPE HATTERAS NORTH
CAROLINA. CRISTOBAL IS MOVING NORTHEAST 6 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WINDS ARE
NOW 40 KT WITH GUSTS TO 50 KT. PLEASE READ THE LATEST NHC
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
AND THE PUBLIC ADVISORY UNDER MIATCPAT3/ WTNT33 KNHC FOR MORE
DETAILS. THE OVERALL ORGANIZATION OF THE SYSTEM CONTINUES TO
SLOWLY EVOLVE AS INDICATED BY THE LATEST SATELLITE IMAGERY AND
RADAR DATA FROM THE WILMINGTON NC WSR-88D. CRISTOBAL IS FORECAST
TO SLOWLY STRENGTHEN OVER THE NEXT FEW DAYS AS THE CENTER OF THE
STORM MOVES ALONG THE COAST OF NORTH CAROLINA TONIGHT AND
SUNDAY. RAINFALL AMOUNTS OF 3 TO 5 INCHES ARE EXPECTED ALONG THE
COAST OF NORTH CAROLINA WITH ISOLATED HEAVIER AMOUNTS.

STRONG TROPICAL WAVE ALONG 80W S OF 21N WITH AN ASSOCIATED LOW
PRESS NEAR 15N80W 1009 MB. SCATTERED STRONG THUNDERSTORMS
CONTINUE TO FLARE UP IN ASSOCIATION WITH THIS WAVE WITH SOME OF
THE ACTIVITY VERY CLOSE TO THE LOW LEVEL CENTER. DIFLUENT FLOW E
OF AN UPPER LEVEL LOW AND TROUGH OVER THE NW CARIBBEAN IS
ALLOWING CONVECTIVE ACTIVITY TO PERSIST IN THE VICINITY OF THE
WAVE AND LOW. SURFACE OBSERVATIONS FROM BUOYS 42057 AND 42058
INDICATED NE WINDS OF 20-25 KT AHEAD OF THE WAVE AND SE WINDS OF
20-25 KT BEHIND THE WAVE. HOWEVER OBSERVATIONS FROM A
RECONNAISSANCE AIRCRAFT INDICATED GALE FORCE WINDS AT THE
SURFACE N OF 16N E OF THE WAVE AXIS. A GALE WARNING WILL BE
ISSUED FOR THE AREA IN THE OFFSHORE WATERS AND HIGH SEAS
FORECASTS. THE RECONNAISSANCE AIRCRAFT ALSO DETERMINED THAT THE
CIRCULATION WAS NOT QUITE CLOSED AT THIS TIME. ENVIRONMENTAL
CONDITIONS APPEAR FAVORABLE FOR THIS SYSTEM TO BECOME A TROPICAL
DEPRESSION WITHIN THE NEXT DAY OR TWO AS IT MOVES WEST
NORTHWESTWARD AT 15 KT. REGARDLESS OF DEVELOPMENT ...LOCALLY
HEAVY RAINS WILL AFFECT JAMAICA...PORTIONS OF CUBA...AND THE
CAYMAN ISLANDS TONIGHT AND TOMORROW. INTERESTS IN THE
NORTHWESTERN CARIBBEAN SEA AND THE YUCATAN PENINSULA SHOULD
CONTINUE TO MONITOR THE PROGRESS OF THIS SYSTEM.

THE WESTERN CARIBBEAN SEA TROPICAL WAVE ALONG 91W SOUTH OF 21N
MOVING WEST ABOUT 12 KT. THE WAVE EXTENDS FROM THE NORTHERN
YUCATAN PENINSULA TO THE EASTERN PACIFIC OCEAN N OF 05N.
...CROSSING OVER GUATEMALA. ASSOCIATED 1009 MB LOW IS LOCATED
OVER THE E PACIFIC NEAR 13N91W. HEAVY RAINS OVER PORTIONS OF EL
SALVADOR... GUATEMALA...AND SE MEXICO COULD CAUSE
LIFE-THREATENING FLASH FLOODS AND MUDSLIDES OVER THE NEXT DAY OR
SO. IN ADDITION... CONDITIONS APPEAR CONDUCIVE FOR POSSIBLE
TROPICAL CYCLONE FORMATION WITHIN THE NEXT 48 HOURS IN THE E
PACIFIC BASIN.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 55W SOUTH OF 20N MOVING WEST 17 KT. THIS
WAVE IS SOMEWHAT LESS EVIDENT IN THE SATELLITE IMAGERY THAN THE
OTHER WAVES NOTED WITH ONLY AN INVERTED V SIGNATURE INDICATED IN
THE STRATOCUMULUS FIELD WITH NO DEEP CONVECTION ALONG THE WAVE
AXIS ITSELF.

...THE ITCZ...
12N16W 7N30W 4N42W 7N53W 10N62W. SCATTERED MODERATE TO STRONG
THUNDERSTORMS ARE WITHIN 60-75 NM EITHER SIDE OF THE AXIS
BETWEEN 26W AND 33W. SCATTERED MODERATE CONVECTION WAS NOTED
WITHIN 90 NM N OF THE AXIS BETWEEN 36W AND 45W. ADDITIONAL
SCATTERED MODERATE CONVECTION WAS EMERGING OFF THE WEST COAST OF
SENEGAL AND GAMBIA FROM 8N TO 12N.

...DISCUSSION...

THE GULF OF MEXICO...
THE OVERALL FLOW OVER THE GULF IS RATHER AMPLIFIED WITH A SHARP
UPPER LEVEL TROUGH EXTENDING FROM E TEXAS TO A CYCLONIC
CIRCULATION OVER THE MIDDLE RIO GRANDE VALLEY NEAR 28N99W.
A NARROW ANTICYCLONE IS CENTERED NEAR 27N89W. A NARROW RIBBON OF
40-50 KT SOUTH-SOUTHWESTERLY UPPER LEVEL WINDS ARE OVER THE W
GULF STREAMING N TOWARD THE LOUISIANA COAST. MIDDLE TO UPPER
LEVEL CYCLONIC FLOW COVERS THE SOUTHEASTERN CORNER OF THE GULF
IN ADVANCE OF A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION OVER
THE FAR NW CARIBBEAN JUST W OF THE ISLE OF YOUTH. AT THE SURFACE
WEAK 1019 MB HIGH PRESSURE NEAR 27N86W WAS IN CONTROL OVER THE
GULF.

THE CARIBBEAN SEA...
A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION WAS LOCATED JUST TO
THE WEST OF THE ISLE OF YOUTH AND WAS MOVING WEST 15-20 KT. AN
UPPER LEVEL ANTICYCLONE WAS LOCATED TO THE EAST NEAR 19N74W/THE
WINDWARD PASSAGE. DOMINATING THE FLOW OVER THE CENTRAL
CARIBBEAN. THE SOUTHWARD EXTENSION OF A MIDDLE TO UPPER LEVEL
TROUGH FROM THE ATLANTIC OCEAN NEAR 20N57W INTO THE EASTERN
CARIBBEAN SEA NEAR 17N62W TO A BASE NEAR 13N67W. SCATTERED
MODERATE SHOWERS AND ISOLATED THUNDERSTORMS FROM 11N TO 15N
BETWEEN 60W AND 66W IS TO THE SOUTHEAST OF THE BASE THE TROUGH.

THE ATLANTIC OCEAN...
A SURFACE TROUGH EXTENDS FROM 32N52W TO 27N60W TO A 1017 MB LOW
PRESSURE CENTER NEAR 27N65W. THE TROUGH CONTINUES FROM THE LOW
PRESSURE CENTER TO 25N71W. A PATCH OF SCATTERED MODERATE TO
STRONG THUNDERSTORMS ARE NOTED WITHIN 90 NM IN THE E SEMICIRCLE
OF THE LOW. ISOLATED MODERATE SHOWERS ARE WITHIN 60 NM ON EITHER
SIDE OF THE TROUGH BETWEEN 52W AND 58W...AND WITHIN 45-60 NM
EITHER SIDE OF THE TROUGH BETWEEN THE LOW AND 67W. A MIDDLE TO
UPPER LEVEL TROUGH IS CONNECTED BY ONE CYCLONIC CIRCULATION
CENTER NEAR 27N51W TO 20N57W TO 17N62W IN THE EASTERN
CARIBBEAN SEA. THIS TROUGH IS EMBEDDED IN/SURROUNDED BY DRY AIR
IN SUBSIDENCE.

$$
COBB





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