[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 300545
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

TROPICAL STORM MELISSA IS CENTERED NEAR 15.8N 30.2W OR ABOUT 410
NM WEST OF THE CAPE VERDE ISLANDS AT 30/0300 UTC MOVING WNW AT 8
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 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 AND THE PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR
MORE DETAILS.  CONVECTION IN THE PAST 3 HOURS DECREASED IN
INTENSITY THOUGH MAINTAINED THE SAME SIZE OF COVERAGE.  STRONG
WESTERLY SHEAR PERSISTS OVER THE STORM.  TROPICAL STORM STATUS
IS FORECAST FOR A COUPLE OF DAYS FOLLOWED BY WEAKENING AS SHEAR
INCREASES AND COOLER WATERS ARE ENCOUNTERED.  PRESENTLY
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 14N-17N
BETWEEN 28W-30W.

...TROPICAL WAVES...

TROPICAL WAVE IS OFF THE COAST OF W AFRICA ALONG 20W S OF 14N
MOVING W 10-15 KT.  THIS WAVE IS LOWER AMPLITUDE THAT MANY OF
PREVIOUS ONES 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 CONVECTION IS FROM 9N-11N BETWEEN 19W-22W...
AND FROM 4N-6N BETWEEN 20W-25W.

TROPICAL WAVE IS ALONG 39W S OF 16N MOVING W 15 KT OVER THE PAST
24 HOURS. NIGHT CHANNEL VIS IMAGES SHOWS AN AREA OF SLIGHT
CYCLONIC TURNING IN THE SURROUNDING LOW CLOUDS.  THERE IS ALSO A
WEAK NWD PERTURBATION IN THE ITCZ...WHICH IS WELL REFLECTED IN
THE MIMIC TPW ANIMATION.  SHOWER ACTIVITY REMAINS VERY MINIMAL.

TROPICAL WAVE IS OVER CENTRAL AMERICA AND THE NW CARIBBEAN ALONG
86W S OF 20N MOVING W 15 KT.  LOW-LEVEL CONVERGENCE NEAR THE
WAVE ALONG WITH DIFFLUENCE ALOFT IS GENERATING A GOOD AMOUNT OF
CONVECTION W OF THE WAVE AXIS.  SCATTERED MODERATE TO STRONG
CONVECTION IS OVER EL SALVADOR AND HONDURAS FROM 12N-15N BETWEEN
86W-90W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N8W 7N20W 5N25W 8N38W 6N54W.
OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE E ATLC TROPICAL
WAVE...SCATTERED MODERATE CONVECTION IS FROM 6N-8N BETWEEN
24W-26W... AND FROM 4N-6N BETWEEN 32W-36W.

DISCUSSION...

GULF OF MEXICO...
A WEAK COLD FRONT HAS DIPPER S TO S FLORIDA.  THE FRONT IS
DELINEATED BY A WIND SHIFT AND SLIGHT THERMAL COOLING.
THUNDERSTORMS ARE NOW 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.  SCATTERED MODERATE CONVECTION IS ALONG THE COAST OF
HONDURAS FROM 15N-17N BETWEEN 83W-86W.  TRADEWINDS REMAIN LIGHT
TO MODERATE ACROSS THE BASIN.  SCATTERED MODERATE TO STRONG
CONVECTION IS OVER HAITI FROM 18N-20N BETWEEN 72W-75W.  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 S
FLORIDA ALONG 32N67W 27N80W.  CLUSTERS OF ISOLATED MODERATE
CONVECTION ARE WITHIN 60 NM OF THE FRONT.  A PREFRONTAL TROUGH
EXTENDS FROM 30N68W TO E CUBA NEAR 20N75W.  SCATTERED MODERATE
TO ISOLATED STRONG CONVECTION IS FROM 21N-24N BETWEEN
71W-76W...AND FROM 23N-26N BETWEEN 68W-71W.  A 1024 MB HIGH IS
OVER THE CENTRAL ATLANTIC NEAR 33N45W.  ANOTHER 1022 MB HIGH IS
OVER THE E ATLANTIC NEAR 27N22W.  THE 1009 MB REMNANT LOW OF
KAREN IS E OF THE LEEWARD ISLANDS NEAR 16N54W AND CONTINUES TO
HAVE STRONG WESTERLY SHEAR OVER THE LOW CENTER.  SCATTERED
MODERATE TO STRONG CONVECTION IS E OF THE CENTER FROM 13N-19N
BETWEEN 49W-53W.  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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