[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131047
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU AUG 13 2009

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
1000 UTC.

...SPECIAL FEATURES...
TROPICAL DEPRESSION TWO IS CENTERED NEAR 14.0N 36.9W OR ABOUT
840 MILES...1350 KM...WEST OF THE SOUTHERNMOST CAPE VERDE
ISLANDS AT 13/0900 UTC MOVING W AT 10 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 25
KT WITH GUSTS TO 35 KT. WWD MOTION IS EXPECTED TO CONTINUE OVER
THE NEXT FEW DAYS WITH A GRADUAL BEND TO THE WNW AND AN INCREASE
IN FORWARD SPEED. LITTLE CHANGE IN INTENSITY IS EXPECTED OVER
THE NEXT 24 HRS. HOWEVER...THE DEPRESSION STILL COULD BECOME A
TROPICAL STORM IN A FEW DAYS. LITTLE DEEP CONVECTION IS
CURRENTLY ASSOCIATED WITH THE SYSTEM...BUT SCATTERED SHOWERS ARE
WITHIN 100 NM OF THE CENTER LOCATION. SEE LATEST NHC FORECAST
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 FOR MORE
DETAILS.

A STRONG TROPICAL WAVE IS ALONG 22W S OF 16N NEAR THE CAPE VERDE
ISLANDS MOVING W NEAR 15 KT. RECENT VISIBLE SATELLITE
IMAGERY...AS WELL AS A 0746 UTC QUIKSCAT PASS INDICATE LOW-LEVEL
CYCLONIC CIRCULATION NEAR THE WAVE GIVING EVIDENCE OF A 1010 MB
SURFACE LOW ANALYZED ALONG THE WAVE AXIS NEAR 12N. NUMEROUS
MODERATE/SCATTERED STRONG CONVECTION IS FROM 8N-11N BETWEEN
21W-28W...AND FROM 12N-15N BETWEEN 21W-26W. THERE IS A 30-50
PERCENT CHANCE OF THIS SYSTEM TO DEVELOP INTO A TROPICAL CYCLONE
IN THE NEXT 48 HRS.

...TROPICAL WAVES...
A TROPICAL WAVE EXTENDS ALONG 21N67W T15N65 7N64W MOVING W NEAR
20 KT. SATELLITE IMAGERY INDICATES AN INVERTED-V STRUCTURE IN
THE LOW-LEVEL CLOUD PATTERN. THE WAVE ALSO COINCIDES WITH A DEEP
MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-7N
BETWEEN 63W-65W...AND FROM 23N-25N BETWEEN 66W-71W. SCATTERED
SHOWERS ARE WITHIN 250 NM E OF THE WAVE AXIS AFFECTING THE
LESSER ANTILLES. THIS ACTIVITY IS ENHANCED BY UPPER LEVEL
DIFFLUENCE.

A TROPICAL WAVE IS ALONG 74W S OF 21N MOVING W NEAR 20 KT.
CURRENT POSITION IS BASED ON CONTINUITY. STRONG SUBSIDENCE ALOFT
IS INHIBITING ANY DEEP CONVECTION NEAR THE WAVE AXIS...EXCEPT
FOR OVER COLUMBIA WHERE A LARGE CLUSTER OF SCATTERED
MODERATE/STRONG CONVECTION IS FROM 5N-9N BETWEEN 73W-76W.

A TROPICAL WAVE IS ALONG 88W S OF 20N MOVING W NEAR 18 KT.
THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 15N-18N BETWEEN 86W-89W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 13N16W 12N25W 14N34W 10N48W
11N62W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS JUST
OFF THE AFRICA COAST FROM 7N-12N BETWEEN 13W-17W. SCATTERED
MODERATE CONVECTION IS FROM 10N-12N BETWEEN 42W-44W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0900 UTC...A SURFACE TROUGH IS ACROSS THE GULF OF MEXICO
EXTENDING FROM A 1013 MB SURFACE LOW NEAR 30N83W TO 24N91W. THE
TROUGH IS SUPPORTED BY AN UPPER LEVEL TROUGH ACROSS THE ERN
CONUS EXTENDING ACROSS THE ERN GULF TO 24N87W. UPPER LEVEL
DIFFLUENCE ALONG WITH SURFACE CONVERGENCE NEAR THE SURFACE
TROUGH ARE SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS MUCH
OF THE CENTRAL GULF WITH 100 NM EITHER SIDE OF THE TROUGH AXIS.
ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ACROSS THE FAR NW GULF N
OF 27N W OF 92W. THIS ACTIVITY IS SUPPORTED BY A STATIONARY
FRONT EXTENDING ACROSS THE GULF COAST FROM 31N88W TO 30N95W...AS
WELL AS UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH
OVER THE ERN GULF AND AN UPPER LEVEL RIDGE OVER TEXAS AND NRN
MEXICO. ISOLATED SHOWERS ARE ACROSS THE BAY OF CAMPECHE S OF 21N
BETWEEN 90W-95W SUPPORTED BY UPPER LEVEL DIFFLUENCE BETWEEN AN
UPPER LEVEL RIDGE CENTERED OVER BELIZE NEAR 17N89W AND AN UPPER
LEVEL TROUGH CENTERED S OF MEXICO NEAR 16N103W. EXPECT THE
SURFACE TROUGH TO REMAIN ACROSS THE CENTRAL GULF...AND A
TROPICAL WAVE E OF THE YUCATAN PENINSULA TO REACH THE SW GULF
LATER TODAY.

CARIBBEAN SEA...
THREE TROPICAL WAVES ARE AFFECTING THE CARIBBEAN SEA AND CENTRAL
AMERICA...SEE ABOVE. ISOLATED SHOWERS/THUNDERSTORMS ARE ACROSS
THE WRN CARIBBEAN FROM 9N-21N BETWEEN 78W-84W DUE TO UPPER LEVEL
DIFFLUENCE BETWEEN AN UPPER LEVEL HIGH OVER BELIZE NEAR 17N89W
AND AN UPPER LEVEL LOW OVER WRN HISPANIOLA NEAR 19N73W. STRONG
SUBSIDENCE ALOFT IS OVER THE CENTRAL CARIBBEAN INFLUENCED BY
CONVERGENCE NEAR THE UPPER LEVEL LOW...INHIBITING CONVECTION
NEAR THE TROPICAL WAVE ALONG 74W. UPPER LEVEL DIFFLUENCE BETWEEN
THE UPPER LEVEL LOW AND AN UPPER LEVEL RIDGE E OF 68W IS
SUPPORTING CONVECTION NEAR THE TROPICAL WAVE IN THE ERN
CARIBBEAN. MODERATE TO FRESH TRADEWINDS ARE OVER MUCH OF THE
BASIN...BECOMING STRONG NEAR THE COAST OF COLUMBIA.  EXPECT
SHOWERS/ISOLATED THUNDERSTORMS OVER THE CARIBBEAN DUE TO THE
TROPICAL WAVES OVER THE NEXT 24 HOURS.

ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS THE FAR W ATLC N OF
24N W OF 78W DUE TO SURFACE CONVERGENCE AHEAD OF A SURFACE
TROUGH OVER THE GULF OF MEXICO EXTENDING ACROSS NRN FLORIDA TO
NEAR 31N82W...AS OF 0900 UTC. UPPER LEVEL DIFFLUENCE BETWEEN AN
UPPER LEVEL TROUGH W OF 78W AND AN UPPER LEVEL RIDGE BETWEEN
57W-78W IS ALSO SUPPORTING THE SHOWER ACTIVITY. SCATTERED
SHOWERS/THUNDERSTORMS ARE N OF PUERTO RICO AND HISPANIOLA
ASSOCIATED WITH A TROPICAL WAVE IN THE ERN CARIBBEAN...SEE
ABOVE. A SURFACE TROUGH EXTENDS FROM 28N74W TO 30N64W SUPPORTING
A FEW ISOLATED SHOWERS WITHIN 50 NM N OF THE TROUGH AXIS.
ISOLATED SHOWERS/THUNDERSTORMS ARE FROM 27N-32N BETWEEN 49W-58W
DUE TO UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL RIDGE
BETWEEN 57W-78W AND AN UPPER LEVEL LOW NEAR 28N45W. ELSEWHERE
ACROSS THE ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A
1026 MB HIGH NEAR 39N26W. A BROAD UPPER LEVEL RIDGE DOMINATES
THE ERN ATLC E OF 40W.

$$
WALTON






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