[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 301044
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN SEP 30 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM MELISSA IS CENTERED NEAR 16.5N 31.4W OR ABOUT 410
NM WEST OF THE CAPE VERDE ISLANDS AT 30/0900 UTC MOVING WNW AT
11 KT.  ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB.  MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 40 KT.  SEE LATEST
NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR
MORE DETAILS.  CONVECTION IN THE PAST 9 HOURS HAS DECREASED IN
INTENSITY THUS THE MAXIMUM WIND SPEEDS WERE REDUCED 5 KT.
STRONG WESTERLY SHEAR PERSISTS OVER THE STORM.  CONTINUED SLOW
DISSIPATION IS FORECAST FOR MELISSA FOR THE NEXT FEW DAYS AS
SHEAR INCREASES AND COOLER WATERS ARE ENCOUNTERED.  PRESENTLY
SCATTERED MODERATE CONVECTION IS FROM 16N-18N BETWEEN
28W-32W.

...TROPICAL WAVES...

TROPICAL WAVE IS OFF THE COAST OF W AFRICA ALONG 21W S OF 16N
MOVING W 10-15 KT.  THIS WAVE IS LOWER IN AMPLITUDE THAN MANY OF
PREVIOUS WAVES THIS MONTH.  THE MIMIC TPW ANIMATION SHOWS A
MODEST BULGE OF MOISTENED AIR OFF THE AFRICAN COAST.  SATELLITE
IMAGERY AND DERIVED WINDS SHOW A BROAD AREA OF TURNING.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS W OF THE
WAVE AXIS FROM 2N-8N BETWEEN 24W-26W.

TROPICAL WAVE IS ALONG 40W S OF 16N MOVING W 15 KT.  NIGHT
CHANNEL VISIBLE IMAGERY SHOWS AN AREA OF SLIGHT CYCLONIC TURNING
IN THE SURROUNDING LOW CLOUDS.  THERE IS ALSO A WEAK NWD
PERTURBATION IN THE ITCZ THAT IS NOTED ON THE MIMIC TPW
ANIMATION.  CONVECTION IS CONFINED TO THE ITCZ.  SCATTERED
MODERATE CONVECTION IS FROM 4N-6N BETWEEN 35W-39W.

TROPICAL WAVE IS OVER CENTRAL AMERICA AND THE NW CARIBBEAN ALONG
88W S OF 20N MOVING W 15 KT.  LOW-LEVEL CONVERGENCE NEAR THE
WAVE ALONG WITH DIFFLUENCE ALOFT IS GENERATING A FAIR AMOUNT OF
CONVECTION ALONG THE WAVE AXIS.  SCATTERED MODERATE CONVECTION
IS OVER BELIZE FROM 16N-18N BETWEEN 87W-89W.  SIMILAR CONVECTION
IS S OF EL SALVADOR FROM 11N-13N BETWEEN 88W-89W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 9N21W 6N30W 7N50W 7N60W.
OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES
...SCATTERED MODERATE CONVECTION IS FROM 3N-5N BETWEEN 12W-15W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 3N-5N
BETWEEN 31W-35W.

DISCUSSION...

GULF OF MEXICO...
A WEAK COLD FRONT HAS PUSHED S OF FLORIDA AND IS NOW IN THE
STRAITS OF FLORIDA.  THE FRONT IS DELINEATED BY A WIND SHIFT AND
SLIGHT THERMAL COOLING.  THUNDERSTORMS REMAIN OVER S FLORIDA S
OF LAKE OKEECHOBEE.  THE GULF OF MEXICO HAS NELY SURFACE FLOW AS
HIGH PRESSURE RIDGING WITH MOSTLY FAIR WEATHER PREVAILS.  WIND
VELOCITIES ARE 20-25 KT OVER THE NE GULF AND 10-15 KT
ELSEWHERE.  IN THE UPPER LEVELS...AN UPPER HIGH WITH SIGNIFICANT
UPPER LEVEL MOISTURE IS OVER THE W GULF NEAR 22N97W WITH A RIDGE
AXIS EXTENDING N TO LOUISIANA.  THE BASE OF A TROUGH WITH STRONG
SUBSIDENCE IS OVER NE GULF AND FLORIDA N OF 24N AND E OF 90W.
THIS UPPER LEVEL TROUGH IS HOSTING THE FRONTAL SYSTEM MENTIONED
ABOVE.  EXPECT THE COLD FRONT TO PUSH E INTO THE W ATLANTIC
DURING THE NEXT 24 HOURS.  EXPECT CONVECTION OVER THE BAHAMAS.
ALSO EXPECT ONSHORE FLOW TO PRODUCE CONVECTION ALONG THE TEXAS
AND MEXICO COASTS DURING THE NEXT 24 HOURS.

CARIBBEAN SEA...
A TROPICAL WAVE IS MOVING WWD ACROSS THE NW CARIBBEAN AND
CENTRAL AMERICA WITH CONVECTION. SEE THE TROPICAL WAVE SECTION
ABOVE.  ELSEWHERE...SCATTERED MODERATE TO STRONG CONVECTION IS
ALONG THE COASTS OF COSTA RICA AND NICARAGUA FROM 8N-13N BETWEEN
78W-84W.  SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS
ALSO W OF HAITI FROM 17N-19N BETWEEN 75W-77W.  WIDELY SCATTERED
MODERATE CONVECTION IS S OF THE DOMINICAN REPUBLIC FROM 16N-18N
BETWEEN 70W-73W.  TRADEWINDS REMAIN LIGHT TO MODERATE ACROSS THE
BASIN. IN THE UPPER LEVELS...AN UPPER LEVEL HIGH IS N OF
COLOMBIA NEAR 13N76W.  ANTICYCLONIC FLOW IS OVER THE CENTRAL AND
EASTERN CARIBBEAN.  SIGNIFICANT UPPER LEVEL MOISTURE AND BROKEN
HIGH CLOUDS COVERS THIS AREA.  EXPECT CONVECTION OVER MOST OF
THE CARIBBEAN AND CENTRAL AMERICA W OF 65W DURING THE NEXT 24
HOURS.

ATLANTIC OCEAN...
A WEAK COLD FRONT IS OVER THE W ATLANTIC EXTENDING S TO THE
STRAITS OF FLORIDA ALONG 32N63W 29N70W 24N80W.  CLUSTERS OF
ISOLATED MODERATE CONVECTION ARE WITHIN 60 NM OF THE FRONT.  A
PREFRONTAL TROUGH EXTENDS FROM 27N71W TO E CUBA NEAR 20N76W.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 20N-30N
BETWEEN 68W-73W.  A 1023 MB HIGH IS OVER THE CENTRAL ATLANTIC
NEAR 34N45W.  ANOTHER 1020 MB HIGH IS OVER THE E ATLANTIC NEAR
26N27W.  THE 1010 MB REMNANT LOW OF KAREN IS E OF THE LEEWARD
ISLANDS NEAR 16N53W AND CONTINUES TO HAVE STRONG WESTERLY SHEAR
OVER THE LOW CENTER.  SCATTERED MODERATE TO STRONG CONVECTION IS
E OF THE CENTER FROM 14N-19N BETWEEN 50W-55W.  IN THE UPPER
LEVELS...A TROUGH IS OVER THE W ATLANTIC N OF 25N W OF 75W.  A
RIDGE IS N OF 20N BETWEEN 70W-75W.  A LARGE UPPER LEVEL LOW IS
CENTERED OVER THE CENTRAL ATLANTIC NEAR 24N62W PRODUCING THE
WESTERLY SHEAR OVER THE REMNANTS OF KAREN.  WLY FLOW IS OVER THE
E ATLANTIC N OF 20N E OF 40W.  A LARGE UPPER LEVEL HIGH IS OVER
THE TROPICS NEAR 13N33W.  ANTICYCLONIC FLOW IS FROM EQ-20N
BETWEEN 20W-50W.

$$
FORMOSA






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