[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 230003
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED SEP 22 2010

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
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LISA IS CENTERED NEAR 17.7N 30.2W AT 22/2100 UTC
OR ABOUT 370 NM WNW OF THE CAPE VERDE ISLANDS MOVING E AT 3 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED
WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/ WTNT24 KNHC
FOR MORE DETAILS. LISA IS SURROUNDED BY MID LEVEL DRY AIR AND IS
LOCATED OVER AN AREA WHERE THE OCEAN HEAT CONTENT IS RATHER
LOW...THUS LIMITING DEEP CONVECTION NEAR THE CENTER. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 60/75
NM OF LINE FROM THE LOW LEVEL CENTER NE TO 21N26W.

TROPICAL WAVE EXTENDS ALONG 71W S OF 17N WITH A 1008 MB LOW
ALONG THE WAVE NEAR 13N. THIS WAVE IS EMBEDDED WITHIN AN AREA OF
DEEP LAYERED MOISTURE AND DIFFLUENT FLOW...THEREFORE A BROAD
AREA OF SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS COVERS MOST
OF THE CARIBBEAN. AIRCRAFT DATA FROM NATIONAL SCIENCE FOUNDATION
AND NASA RESEARCH MISSIONS INDICATE THAT THIS AREA HAS BECOME A
LITTLE BETTER DEFINED THIS EVENING. ENVIRONMENTAL CONDITIONS
APPEAR FAVORABLE FOR DEVELOPMENT AND THIS SYSTEM COULD BECOME A
TROPICAL DEPRESSION DURING THE NEXT DAY OR TWO AS IT MOVES W
NEAR 15 KT TOWARD THE W CARIBBEAN. THERE IS A HIGH CHANCE OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS. REGARDLESS OF DEVELOPMENT...THIS SYSTEM HAS THE POTENTIAL
TO PRODUCE HEAVY RAINFALL OVER NORTHERN VENEZUELA AND COLOMBIA
DURING THE NEXT DAY OR SO...AND OVER PORTIONS OF CENTRAL AMERICA
IN A COUPLE OF DAYS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 23W S OF 20N MOVING W NEAR 10 KT. THE
SURFACE LOW HAS DISSIPATED. ALTHOUGH THE WAVE IS LOCATED ON THE
EASTERN EDGE OF DEEP LAYERED MOISTURE AS INDICATED ON THE TOTAL
PRECIPITABLE WATER IMAGERY...THERE IS NO ASSOCIATED DEEP
CONVECTION.

...ITCZ...

THE ITCZ IS ANALYZED S OF T.S. LISA NEAR 11N31W 10N49W 11N63W.
SMALL CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 1N-10N
BETWEEN 18W-34W. SMALL CLUSTERS OF ISOLATED MODERATE CONVECTION
ARE FROM 6N-11N BETWEEN 36W-46W.

...DISCUSSION...

GULF OF MEXICO...
A BROAD UPPER RIDGE COVERS THE W GULF W OF 92W ANCHORED OVER THE
MEXICO/TEXAS BORDER NEAR 29N103W AND IS PROVIDING STABLE
NORTHERLY FLOW ALOFT OVER THE NW GULF. A SECOND UPPER RIDGE
COVERS THE E GULF E OF 87W ANCHORED IN THE W ATLC. THESE UPPER
RIDGES ARE INDUCING AN UPPER TROUGH OVER THE CENTRAL GULF FROM
OVER SE LOUISIANA THROUGH AN UPPER LOW NEAR 25N89W TO THE
YUCATAN PENINSULA NEAR 21N89W. A SURFACE RIDGE COVERS THE N GULF
N OF 25N ANCHORED BY A 1022 MB HIGH OVER S GEORGIA AND A 1025 MB
HIGH OVER THE W ATLC N OF THE DISCUSSION AREA GIVING THE GULF
WATERS E TO SE SURFACE FLOW. THIS SCENARIO IS GENERATING
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF A LINE
FROM FLORIDA NEAR FORT MYERS TO THE TEXAS/LOUISIANA BORDER.

CARIBBEAN SEA...
THE MAIN SURFACE FEATURE IS THE TROPICAL WAVE/LOW IN THE SPECIAL
FEATURES ABOVE. BROAD UPPER RIDGE COVERS THE CARIBBEAN W OF 70W
ANCHORED IN THE W ATLC WITH THE W CARIBBEAN W OF 80W WITH
SOUTHERLY FLOW ALOFT. EMBEDDED WITHIN THE UPPER RIDGE IS AN
UPPER LOW THAT IS MOVING W JUST N OF THE VIRGIN ISLANDS/PUERTO
RICO NEAR 10N65W COVERING THE AREA N OF 15N BETWEEN 60W-68W AND
IS DISTORTING THE UPPER RIDGE E OF 70W. DEEP LAYERED MOISTURE
COVERS THE CARIBBEAN WITH THE EXCEPTION OF N OF 17N E OF 75W
WHERE STRONG SUBSIDENCE AND RELATIVE DRY AIR DOMINATE. THIS DEEP
MOISTURE COUPLED WITH THE DIFFLUENT FLOW OVER MOST OF THE
CARIBBEAN ARE GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS N OF 18N TO ACROSS CUBA BETWEEN 75W-84W INCLUDING
JAMAICA. SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS
COVER THE REMAINDER OF THE CARIBBEAN FROM 12N-16N E OF 83W TO
OVER THE LESSER ANTILLES.

ATLANTIC OCEAN...
AN UPPER RIDGE COVERS THE W ATLC ANCHORED NEAR 25N69W BEING
DISTORTED BY AN UPPER LOW THAT IS MOVING W JUST N OF THE VIRGIN
ISLANDS/PUERTO RICO NEAR 10N65W COVERING THE AREA S OF 24N
BETWEEN 60W-68W. THE UPPER RIDGE IS DRAWING TROPICAL MOISTURE N
ACROSS CUBA AND IS GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS S OF 25N W OF 75W THROUGH THE FLORIDA STRAITS. A
SURFACE RIDGE DOMINATES THE W AND CENTRAL ATLC W OF 45W INTO
GULF OF MEXICO AND SE CONUS ANCHORED BY A 1025 MB HIGH 200 NM
NNE OF BERMUDA. AN UPPER LOW IS JUST N OF THE DISCUSSION AREA
NEAR 34N38W SUPPORTING A 1008 MB LOW NEAR 33N37W AND A SURFACE
TROUGH THAT ENTERS THE E ATLC NEAR 32N37W CONTINUING ALONG
29N39W TO 27N45W. HOWEVER WITH THE DRY AIR IN PLACE OVER THE E
ATLC THERE IS NO SIGNIFICANT WEATHER ASSOCIATED WITH THIS
SURFACE TROUGH. A BROAD HIGH AMPLITUDE UPPER RIDGE COVERS THE
FAR E ATLC E OF 25W ANCHORED INLAND OVER AFRICA.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
PAW




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