[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 200606
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON AUG 20 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0415 UTC.

...SPECIAL FEATURE...
THE EYE OF EXTREMELY DANGEROUS CATEGORY FOUR HURRICANE DEAN WAS
NEAR 17.7N 79.7W...OR 130 NM/240 KM SOUTHEAST OF GRAND CAYMAN.
DEAN IS MOVING WEST 17 KT. THE MAXIMUM SUSTAINED WIND SPEEDS
ARE 125 KT WITH GUSTS TO 155 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 926 MB. FLUCTUATIONS IN INTENSITY ARE COMMON IN
MAJOR HURRICANES AND ARE POSSIBLE DURING THE NEXT 24 HOURS.
DEAN HAS THE POTENTIAL TO BECOME A CATEGORY FIVE HURRICANE IN
THE NORTHWESTERN CARIBBEAN SEA ON MONDAY...LIKE GILBERT IN 1988
AND WILMA IN 2005. ALL RESIDENTS IN THE WESTERN CARIBBEAN
SEA...AND THE GULF OF MEXICO SHOULD MONITOR THE PROGRESS OF THIS
POWERFUL HURRICANE. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE LATEST
PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR THE MOST RECENT
WATCH AND WARNING INFORMATION. FOR STORM INFORMATION SPECIFIC TO
YOUR AREA...INCLUDING POSSIBLE INLAND WATCHES AND WARNINGS.
PLEASE MONITOR FORECASTS AND BULLETINS ISSUED BY YOUR LOCAL
WEATHER OFFICE. HURRICANE FORCE WINDS EXTEND OUTWARD UP TO
52 NM/95 KM FROM THE CENTER...AND TROPICAL STORM FORCE WINDS
EXTEND OUTWARD UP TO 176 NM/335 KM. COASTAL STORM SURGE FLOODING
OF 5 TO 7 FEET ABOVE NORMAL TIDE LEVELS...ALONG WITH LARGE AND
DANGEROUS BATTERING WAVES...IS POSSIBLE NEAR THE CENTER OF DEAN
WITHIN THE HURRICANE WARNING AREAS IN JAMAICA AND THE CAYMAN
ISLANDS.  STORM SURGE FLOODING AND WAVES IN JAMAICA SHOULD
SUBSIDE LATER TODAY.  COASTAL STORM SURGE FLOODING OF 9 TO
11 FEET ABOVE NORMAL TIDE LEVELS IS POSSIBLE NEAR AND TO THE
NORTH OF WHERE DEAN MAKES LANDFALL ALONG THE EAST COAST OF THE
YUCATAN PENINSULA. THE EYE OF DEAN PASSED JUST SOUTH OF JAMAICA
STARTING AT 19/1900 UTC AND HAS JUST CROSSED THE LONGITUDE OF
NEGRIL ON THE WESTERN END OF THE ISLAND AROUND 20/0300 UTC. THE
CENTER CAME WITHIN ABOUT 20 N MI OF PORTLAND POINT ON THE SOUTH
CENTRAL COAST...CLOSE ENOUGH TO BRING HURRICANE-FORCE WINDS TO
KINGSTON. SATELLITE IMAGERY SUGGESTED THAT THE EYE DIAMETER WAS
SHRINKING GRADUALLY AS THE EYE WAS PASSING BY JAMAICA. AN AIR
FORCE HURRICANE HUNTER AIRCRAFT ARRIVED IN THE EYE OF DEAN AT
20/0130 UTC AND REVEALED THAT THE PRESSURE HAD FALLEN TO NEAR
925 MB...AND THAT DEAN NOW HAS A SINGLE EYEWALL AT A DIAMETER OF
ABOUT 15 N MI. THE SATELLITE APPEARANCE OF DEAN WAS IMPRESSIVE
WITH GOOD SYMMETRY FOR THE EYE...THE EYEWALL...SPIRAL RAINBANDS
AND OUTFLOW. NUMEROUS STRONG SHOWERS AND THUNDERSTORMS ARE FROM
16.5N TO 18.5N BETWEEN 78W AND 80.5W. STRONG SHOWERS AND
THUNDERSTORMS IN BANDS AROUND THE CENTER ARE WITHIN 90 TO 120 NM
OF THE CENTER FROM EAST TO SOUTH. STRONG SHOWERS AND
THUNDERSTORMS ARE FROM 15N TO 17N BETWEEN 71W AND 73W...AND FROM
11N TO 12N BETWEEN 73W AND 75W IN THE OUTER BAND THAT IS ABOUT
400 NM EAST OF THE CENTER. ISOLATED MODERATE SHOWERS TO LOCALLY
STRONG THUNDERSTORMS EXTEND FROM ONE END OF CUBA TO THE OTHER
END.

...TROPICAL WAVES...

A LARGE ATLANTIC OCEAN TROPICAL WAVE IS ALONG 54W/55W SOUTH OF
25N MOVING WEST 20 KT DURING THE LAST 24 HOURS. A 1010 MB LOW
PRESSURE CENTER IS ALONG THIS WAVE NEAR 12.5N. THE LOW CENTER
HAS BEEN WEAKENING WITH TIME. SCATTERED STRONG SHOWERS AND
THUNDERSTORMS ARE FROM 20N TO 22N BETWEEN 50W AND 53.5W...AND
FROM 23.5N TO 25N BETWEEN 55W AND 57W. SCATTERED MODERATE
SHOWERS TO ISOLATED STRONG THUNDERSTORMS ARE ELSEWHERE FROM
19.5N TO 26N BETWEEN 50W AND 60W. ISOLATED MODERATE SHOWERS ARE
IN THE ATLANTIC OCEAN AND THE CARIBBEAN SEA FROM 9N TO 20N
BETWEEN 50W AND 61W...AND IN THE ATLANTIC OCEAN FROM 14N TO 21N
BETWEEN 42W AND 50W. THIS WAVE WILL CONTINUE TO BE MONITORED
AS SLOW DEVELOPMENT APPEARS POSSIBLE AS IT TRACKS
WEST-NORTHWESTWARD DURING THE NEXT COUPLE OF DAYS.

A GULF OF MEXICO TROPICAL WAVE IS ALONG 92W/93W SOUTH OF 20N
MOVING WEST 10 TO 15 KT. A MIDDLE TO UPPER LEVEL CYCLONIC
CIRCULATION CENTER IS NEAR 26N92W. ALL THE PRECIPITATION IN THE
GULF OF MEXICO WEST OF 84W/85W APPEARS TO BE RELATED TO THIS
CYCLONIC CENTER. FEW SHOWERS OVER THE ISTHMUS OF TEHUANTEPEC.

...THE ITCZ...
FROM THE AFRICA COAST NEAR 12N16W TO 7N33W TO 14N44W 16N50W...
FROM 11N58W TO 10N62W. STRONG SHOWERS AND THUNDERSTORMS ARE
FROM 10N TO 11N BETWEEN 24W AND 29W...AND FROM 6.5N TO 7N
BETWEEN 41W AND 42.5W. ISOLATED MODERATE SHOWERS TO LOCALLY
STRONG THUNDERSTORMS ELSEWHERE FROM 3N TO 10N BETWEEN 20W
AND 50W.

DISCUSSION...

THE GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR
26N92W CONTINUING TO MOVE WESTWARD ACROSS THE GULF OF MEXICO.
THE WESTWARD MOVEMENT OF 15 TO 20 KT THAT WAS PREDICTED BY MANY
OF THE COMPUTER MODELS HAS BEEN PRETTY ACCURATE...THUS LIMITING
IT'S IMPACTS ON HURRICANE DEAN. CYCLONIC FLOW AROUND THE CENTER
COVERS THE AREA WEST OF 84W/85W. PRECIPITATION FROM 4 TO 5 HOURS
AGO ALONG THE NORTHWESTERN YUCATAN PENINSULA AND ABOUT 240 NM TO
THE SOUTH OF THE CENTER HAS DISSIPATED. POSSIBLE SHOWERS ARE
NORTH OF 21N WEST OF 90W. SCATTERED MODERATE SHOWERS TO ISOLATED
STRONG THUNDERSTORMS ARE FROM 26N TO 27N BETWEEN 83W AND 84W OFF
THE WEST COAST OF FLORIDA IN UPPER LEVEL DIFFLUENT WIND FLOW.
A MIDDLE LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR 30N/31N
ALONG 75W. UPPER LEVEL ANTICYCLONIC FLOW IS IN THE GULF OF
MEXICO EAST OF 84W/85W...AND FROM THE BAHAMAS NORTHWARD WEST
OF 70W IN THE ATLANTIC OCEAN. A SURFACE RIDGE EXTENDS FROM
SOUTHWESTERN GEORGIA TO SOUTHEASTERN LOUISIANA TOWARD 23N95W
IN THE SOUTHWESTERN CORNER OF THE GULF OF MEXICO. A TROPICAL
WAVE IS ALONG 92W/93W SOUTH OF 20N.

THE CARIBBEAN SEA...
ALL THE ATTENTION REMAINS FOCUSED ON POWERFUL CATEGORY FOUR
HURRICANE DEAN. DEAN WILL CONTINUE TO HAVE SIGNIFICANT IMPACTS
ON THE CENTRAL AND WESTERN CARIBBEAN SEA AS WELL AS THE YUCATAN
PENINSULA FROM NOW UNTIL AND INCLUDING TUESDAY NIGHT. A MIDDLE
TO UPPER LEVEL TROUGH EXTENDS FROM THE ATLANTIC OCEAN NEAR
25N56W TO 16N63W IN THE NORTHEASTERN CORNER OF THE AREA.

THE ATLANTIC OCEAN...
AN MIDDLE LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR 30N/31N
ALONG 75W. MIDDLE LEVEL ANTICYCLONIC FLOW IS IN THE ATLANTIC
OCEAN FROM THE BAHAMAS NORTHWARD WEST OF 70W. THIS IS THE
FEATURE STEERING DEAN FAIRLY QUICKLY TO THE WEST OR WEST-
NORTHWEST ACROSS THE WESTERN CARIBBEAN SEA. DEAN'S STRONG
CIRCULATION IS CAUSING DISTINCT SINKING/DRYING BEYOND IT'S
OUTFLOW ACROSS THE CENTRAL BAHAMAS AND REGIONS MORE TO THE
NORTH. EASTERLY WINDS ARE QUITE STRONG...25 TO 30 KT WITH HIGHER
GUSTS ACROSS THE EXTREME SOUTHWESTERN ATLANTIC OCEAN NEAR DEAN.
A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM THE ATLANTIC OCEAN
NEAR 25N56W TO 16N63W IN THE NORTHEASTERN CORNER OF THE
CARIBBEAN SEA. THIS TROUGH IS RIGHT ON TOP OF THE 54W/55W
TROPICAL WAVE. A MIDDLE LEVEL ANTICYCLONIC CIRCULATION CENTER IS
NEAR 14N40W. ANTICYCLONIC FLOW IS WITHIN A 360 NM RADIUS OF THE
CENTER. A MIDDLE TO UPPER LEVEL TROUGH EXTENDS FROM A CYCLONIC
CIRCULATION CENTER NEAR 30N29W TO 23N38W. A SURFACE RIDGE PASSES
THROUGH 32N49W...TO JUST SOUTH OF BERMUDA...TO 32N77W...INTO
SOUTHWESTERN GEORGIA.

$$
MT



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