[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 281820
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 28 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM KAREN AT 28/1500 UTC IN THE
ATLANTIC OCEAN WAS NEAR 15.1N 49.2W MOVING WEST-NORTHWEST
8 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE WAS 1009 MB.
THE MAXIMUM SUSTAINED WIND SPEEDS WERE 35 KT WITH GUSTS TO
45 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. PERSISTENTLY
STRONG SOUTHWESTERLY SHEAR IS EXPECTED TO AFFECT KAREN DURING
THE NEXT 72 HOURS. THE FORECAST ALREADY FOR THE NEXT TWELVE
HOURS IS FOR KAREN TO WEAKEN TO A TROPICAL DEPRESSION. IT IS
POSSIBLE THAT SOME INTERMITTENT BURSTS OF DEEP CONVECTIVE
PRECIPITATION MAY OCCUR DURING THE NEXT FEW DAYS. UNFAVORABLE
UPPER LEVEL NORTHWESTERLY WIND FLOW IS EXPECTED TO MOVE ACROSS
KAREN AND CONTINUE ITS WEAKENING TREND AFTER 72 HOURS. SATELLITE
DATA FROM THIS MORNING SUGGESTED THAT THE WEAKENING CENTER OF
KAREN WAS MOVING ERRATICALLY. THE WIND SPEED OF 35 KT ASSIGNED
TO KAREN AT 28/1500 UTC MAY BE GENEROUS CONSIDERING ITS
COMPARATIVELY-WEAKENED STATE. NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS FROM 15N TO 17N BETWEEN 48W AND 49W.

TROPICAL STORM LORENZO WAS DOWNGRADED TO TROPICAL DEPRESSION
LORENZO AT 28/1500 UTC. THE CENTER OF TROPICAL DEPRESSION AT
28/1500 UTC WAS INLAND NEAR 20.6N 98.4W MOVING WEST 8 KT. THE
ESTIMATED MINIMUM CENTRAL PRESSURE WAS 1002 MB. THE MAXIMUM
SUSTAINED WIND SPEEDS WERE 30 KT WITH GUSTS TO 40 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. ALL DATA INDICATE THAT
LORENZO HAS WEAKENED TO A TROPICAL DEPRESSION AS IT CONTINUES
TO MOVE MORE AND MORE INLAND IN EASTERN MEXICO. THE FORECAST
TRACK IS WESTWARD FOR THE NEXT 36 HOURS AT A COMPARATIVELY
SLOW PACE...AFTER WHICH TIME THE REMNANT LOW PRESSURE CENTER
IS EXPECTED TO DISSIPATE. TORRENTIAL RAINS ARE STILL A STRONG
POSSIBILITY WITH A SLOWLY-MOVING LORENZO AND/OR ITS REMNANT
LOW PRESSURE CENTER. THE COLDEST CLOUD TOP TEMPERATURES...
-69 DEGREES CELSIUS AT 47000 FEET ARE ALONG THE MEXICO GULF
COAST FROM 23N TO 24N BETWEEN 97W AND 98W. SHOWERS AND
THUNDERSTORMS REMAIN FROM 21N TO 25N BETWEEN 96W AND 100W.

TROPICAL DEPRESSION FOURTEEN DEVELOPED IN THE EASTERN ATLANTIC
OCEAN AT 28/1500 UTC NEAR 14.1N 26.5W MOVING WEST 6 KT. THE
ESTIMATED MINIMUM CENTRAL PRESSURE WAS 1008 MB. THE MAXIMUM
SUSTAINED WIND SPEEDS WERE 30 KT WITH GUSTS TO 40 KT. PLEASE
READ THE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT4/
WTNT34 KNHC FOR MORE DETAILS. THIS DEPRESSION DEVELOPED IN AN
AREA OF DEEP ORGANIZED CONVECTIVE PRECIPITATION NEAR THE CENTER
WITH WELL ESTABLISHED UPPER LEVEL OUTFLOW. A SHIP LOCATED JUST
TO THE NORTH OF THE CENTER REPORTED 29 KNOTS. THIS DEPRESSION
HAS THE OPPORTUNITY TO STRENGTHEN A LITTLE DURING THE NEXT DAY
OR TWO WHILE THE MIDDLE TO UPPER LEVEL SHEAR IS LOW. THE MIDDLE
TO UPPER LEVEL WIND PATTERNS FOR THE NEXT TWO TO THREE DAYS
SUGGEST THAT THE FUTURE TRACK OF T.D. FOURTEEN WILL BE TO THE
NORTHWEST AND THEN NORTH...ENCOUNTERING HIGHER SHEAR AND COOLER
SEA SURFACE TEMPERATURES AFTER 48 HOURS. STRONG SHOWERS AND
THUNDERSTORMS NOW ARE FROM 13N TO 14N BETWEEN 24W AND 26W...
AND FROM 14N TO 15N BETWEEN 25W AND 26W. TWO OTHER BURSTS OF
SHOWERS AND THUNDERSTORMS ARE WITHIN A 15 NM RADIUS OF 16N23W
AND 16N25.5W.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 30W/31W SOUTH OF 20N
MOVING WEST 10 TO 15 KT. NO WELL DEFINED CYCLONIC FLOW IS NOTED
IN THE VISIBLE CLOUD FIELD TO THE WEST OF T.D. FOURTEEN.
NO DEEP CONVECTIVE PRECIPITATION ACCOMPANIES THIS WAVE.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 77W/78W SOUTH OF 21N
MOVING WEST 10 TO 15 KT. THIS WAVE CUTS RIGHT THROUGH JAMAICA.
AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR 15N74W
AND A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS
NEAR 19N83W. A MIDDLE LEVEL TROUGH IN THE SOUTHWESTERN CORNER
OF THE CARIBBEAN SEA AND THE UPPER LEVEL ANTICYCLONIC FLOW MAY
BE CREATING AN ENVIRONMENT OF DIFFLUENT FLOW AT SOME LEVELS...
ENOUGH TO CREATE SCATTERED STRONG SHOWERS AND THUNDERSTORMS
FROM 11N TO 14N BETWEEN 79W AND NICARAGUA. IT IS POSSIBLE THAT
SOME ENERGY FROM THE WAVE MAY BE INFLUENCING THIS PRECIPITATION.
SHOWERS AND THUNDERSTORMS MORE TO THE NORTH...FROM 18N TO 21N
BETWEEN 75W AND 85W ARE IN AN AREA OF UPPER LEVEL DIFFLUENT FLOW
AND AROUND THE MIDDLE TO UPPER LEVEL CYCLONIC CENTER.

...THE ITCZ...
7N12W 11N22W 10N33W 12N46W 11N52W 9N60W. WIDELY SCATTERED TO
SCATTERED MODERATE SHOWERS/ISOLATED STRONG THUNDERSTORMS ARE
FROM 8N TO 13N BETWEEN 56W AND 62W...COVERING SOME OF THE
SOUTHEASTERN CARIBBEAN SEA ISLANDS. THIS AREA IS AT THE BASE
OF A SYNOPTIC SCALE ATLANTIC OCEAN TROUGH AND THE WESTERN END
OF THE ITCZ. SCATTERED MODERATE SHOWERS TO ISOLATED STRONG
THUNDERSTORMS ARE WITHIN 75 NM ON EITHER SIDE OF 6N11W 3N17W...
AND FROM 7N TO 10N BETWEEN 41W AND 44W. ISOLATED MODERATE
SHOWERS ARE WITHIN 90 NM ON EITHER SIDE OF 3N20W 6N29W 5N35W
AND 5N45W.

DISCUSSION...

THE GULF OF MEXICO...
TROPICAL DEPRESSION LORENZO IS WEAKENING IN EASTERN MEXICO.
RAINFALL TO THE EAST OF T.D. LORENZO IS IN THE COASTAL WATERS
FROM 21N TO 25N...AND INLAND ALSO. THE SLOW MOTION OF LORENZO
WILL GIVE IT SOME TIME IN ORDER TO BE ABLE TO PRODUCE TORRENTIAL
RAINFALL ALONG ITS PATH FOR THE NEXT FEW DAYS. UPPER LEVEL
ANTICYCLONIC OUTFLOW ON TOP OF LORENZO MAKES ITS WAY INTO THE
GULF WATERS AS FAR EAST AS 88W. MIDDLE TO UPPER LEVEL CYCLONIC
FLOW IS AROUND A TROUGH THAT EXTENDS FROM GEORGIA INTO CENTRAL
FLORIDA TO CUBA...AND ULTIMATELY TO THE 19N83W CARIBBEAN SEA
CYCLONIC CENTER. DRY AIR/SUBSIDENCE IS IN THE TROUGH AND MOVING
ACROSS THE SOUTHEASTERN U.S.A..

THE CARIBBEAN SEA...
MIDDLE TO UPPER LEVEL CYCLONIC FLOW CUTS ACROSS THE AREA FROM
THE NORTHEASTERN CORNER TO THE SOUTHEASTERN CORNER...PASSING ON
TOP OF HISPANIOLA AND PUERTO RICO AND EXITING THE AREA ACROSS
ST. LUCIA...BARBADOS AND OTHER WINDWARD ISLANDS. A CARIBBEAN
SEA TROPICAL WAVE IS ALONG 77W/78W SOUTH OF 21N MOVING WEST
10 TO 15 KT. THIS WAVE CUTS RIGHT THROUGH JAMAICA. AN UPPER
LEVEL ANTICYCLONIC CIRCULATION CENTER IS NEAR 15N74W AND
A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR
19N83W. A MIDDLE LEVEL TROUGH IN THE SOUTHWESTERN CORNER OF
THE CARIBBEAN SEA AND THE UPPER LEVEL ANTICYCLONIC FLOW MAY
BE CREATING AN ENVIRONMENT OF DIFFLUENT FLOW AT SOME LEVELS...
ENOUGH TO CREATE SCATTERED STRONG SHOWERS AND THUNDERSTORMS
FROM 11N TO 14N BETWEEN 79W AND NICARAGUA. IT IS POSSIBLE
THAT SOME ENERGY FROM THE WAVE MAY BE INFLUENCING THIS
PRECIPITATION. SHOWERS AND THUNDERSTORMS MORE TO THE
NORTH...FROM 18N TO 21N BETWEEN 75W AND 85W ARE IN
AN AREA OF UPPER LEVEL DIFFLUENT FLOW AND AROUND
THE MIDDLE TO UPPER LEVEL CYCLONIC CENTER.

THE ATLANTIC OCEAN...
A 1014 MB LOW PRESSURE CENTER IS NEAR 29N78W EAST OF THE FLORIDA
COAST. A SURFACE TROUGH PASSES THROUGH THE LOW CENTER...TO THE
NORTHERN BAHAMAS AND ULTIMATELY TO CUBA NEAR 23N81W. A MIDDLE
LEVEL TROUGH REMAINS UNDER AN UPPER LEVEL RIDGE IN THE WESTERN
ATLANTIC OCEAN. THE RIDGE IS ALONG 20N73W 25N74W 29N73W BEYOND
31N72W. A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER IS
NEAR 27N60W. MIDDLE TO UPPER LEVEL DRY AIR/SUBSIDENCE SURROUNDS
THIS CYCLONIC CENTER...AS FAR WEST AS 70W AND FAR EAST AS 50W.
DRY AIR/SUBSIDENCE EVEN CURVES TO THE SOUTHEAST FROM 30N70W TO
20N60W. A TROUGH CONNECTS A 30N50W CYCLONIC CIRCULATION CENTER
TO THE 27N60W CENTER...TO 10N60W OFF THE COASTS OF TRINIDAD AND
VENEZUELA. WIDELY SCATTERED TO SCATTERED MODERATE SHOWERS/
ISOLATED STRONG THUNDERSTORMS ARE WITHIN 60 TO 75 NM ON EITHER
SIDE OF 28N46W 25N55W 22N62W IN THE TROUGH.

$$
MT



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