[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201755
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT SEP 20 2008

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...
TROPICAL WAVE IS ALONG 66W S OF 19N MOVING W NEAR 10 KT. THIS
WAVE IS EMBEDDED WITHIN A BROAD AREA OF LOWER PRESSURE ACROSS
THE E CARIBBEAN AND IS GENERATING A LARGE AREA OF CLOUDINESS
WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM THE WAVE AXIS
ACROSS THE LESSER ANTILLES. THIS SYSTEM IS SHOWING SIGNS OF
IMPROVED ORGANIZATION TODAY AND UPPER-LEVEL WINDS ARE EXPECTED
TO BECOME SOMEWHAT MORE FAVORABLE OVER THE NEXT COUPLE DAYS FOR
SOME ADDITIONAL DEVELOPMENT TO OCCUR.

...TROPICAL WAVES...
TROPICAL WAVE WAS INTRODUCED ALONG 20W/21W S OF 10N MOVING W
NEAR 10-15 KT BASED ON THE SATELLITE IMAGERY AND A RECENT PASS
OF QUIKSCAT. A LOWER TO MID LEVEL LOW IS ALONG THE WAVE NEAR 5N.
BROAD AREA OF CLOUDINESS WITH EMBEDDED SHOWERS COVERS THE AREA
FROM THE EQUATOR TO 13N BETWEEN 16W-24W.

TROPICAL WAVE WAS RELOCATED FROM 30W TO ALONG 36W FROM 12N-18N
BASED ON LONG-TERM SATELLITE IMAGES MOVING W 10-15 KT. WEAK AND
SMALL AREA OF INVERTED-V CURVATURE IS OBSERVED BETWEEN 14N-18N.
WAVE IS EMBEDDED WITHIN A RATHER DRY AIR...THUS NO ASSOCIATED
SHOWER ACTIVITY.

TROPICAL WAVE IS ALONG 53W/54W S OF 18N MOVING W 10-15 KT. WAVE
IS BENEATH AN UPPER RIDGE PROVIDING UPPER LEVEL DIFFLUENCE
MASKING THE SATELLITE SIGNATURE AND ENHANCING AN AREA OF
CLOUDINESS WITH SCATTERED SHOWERS WITHIN 120 NM OF LINE FROM
20N46W ACROSS THE WAVE TO NEAR 14N55W.

TROPICAL WAVE IS ALONG 79W S OF 19N MOVING W 10-15 KT.  WELL
DEFINED INVERTED-V CURVATURE S OF JAMAICA WITH CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION S OF 16N TO INLAND
OVER SOUTH AND CENTRAL AMERICA BETWEEN 74W-84W.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 8N12W 8N19W 5N25W 7N37W 7N50W 9N59W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 2N-10N BETWEEN 26W-31W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH EXTENDS OFF THE COAST OF TEXAS AND MEXICO FROM
28N96W 24N97W TO THE BAY OF CAMPECHE NEAR 20N95W. A BROAD UPPER
LEVEL RIDGE DOMINATES THE GULF ANCHORED OVER S/CENTRAL MEXICO
EXTENDING NE JUST N OF VERACRUZ TO OVER THE FLORIDA PENINSULA
NEAR NAPLES AND COUPLED WITH THE SURFACE TROUGH IS PRODUCING
WIDESPREAD CLOUDINESS WITH CLUSTERS OF SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS N OF 22N BETWEEN 87W-93W AND W OF 93W
INTO THE BAY OF CAMPECHE. A SURFACE RIDGE COVERS THE US TO THE N
GULF COAST STATES. THE SURFACE TROUGH IS EXPECTED TO SLOWLY
WEAKEN AND DRIFT W THROUGH SUN AS THE SURFACE RIDGE WILL
STRENGTHEN DURING THE FIRST OF THE WORKWEEK.

CARIBBEAN SEA...
THE TROPICAL WAVE IN THE E CARIBBEAN IS BECOMING AN AREA TO
WATCH AS SLOW DEVELOPMENT COULD OCCUR OVER THE NEXT FEW DAYS.
SEE SPECIAL FEATURES ABOVE. THE W CARIBBEAN TROPICAL WAVE
CONTINUES TO GENERATE PLENTY OF ACTIVITY BUT DEVELOPMENT IS NOT
EXPECTED. THE UPPER LEVEL ARE DOMINATED BY THE UPPER RIDGE OVER
THE GULF TO THE W AND A SECOND UPPER RIDGE ANCHORED OVER SOUTH
AMERICA EXTENDING NE ACROSS THE ABC ISLANDS INTO THE W TROPICAL
ATLC OVER THE LEEWARD ISLANDS. BETWEEN THESE UPPER RIDGES IS AN
UPPER TROUGH EXTENDING FROM THE W ATLC ACROSS CENTRAL CUBA S TO
PANAMA. THE UPPER LEVEL FEATURES ARE ENHANCING THE ACTIVITY
ASSOCIATED WITH BOTH TROPICAL WAVES WHILE THE REMAINDER OF THE
CARIBBEAN IS ENJOYING FAIR WEATHER THIS AFTERNOON.

ATLANTIC OCEAN...
A NARROW UPPER TROUGH IS OVER THE FAR W ATLC EXTENDING THROUGH
32N78W ACROSS CENTRAL CUBA AND OVER THE CARIBBEAN. A SURFACE
TROUGH ENTERS THE W ATLC FROM A 1016 MB LOW N OF THE REGION
THROUGH 32N73W OVER THE N BAHAMA ISLANDS TO NEAR 24N79W.
ISOLATED SHOWERS ARE WITHIN 200 NM E OF THE SURFACE TROUGH WITH
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OFF THE COAST OF NE
FLORIDA AND GEORGIA FROM 29N-33N BETWEEN 76W-81W. A PAIR OF
BENIGN UPPER LOWS ARE TO THE E CENTERED NEAR 27N46W AND 23N66W.
THE UPPER RIDGE OVER THE E CARIBBEAN EXTENDS OVER THE W TROPICAL
ATLC ACROSS THE LEEWARD ISLANDS TO 18N50W. AN UPPER TROUGH IS
OVER THE NE ATLC EXTENDING FROM A DEEP LAYERED LOW N OF THE
REGION TO 24N E OF 30W TO OVER THE CANARY ISLANDS. A SURFACE
TROUGH ENTERS THE E ATLC NEAR 32N20W EXTENDING TO 27N26W BUT AS
THIS SYSTEM IS IN AN AREA OF DRY STABLE AIR...THUS NO SHOWER
ACTIVITY. THE TYPICAL E/W UPPER RIDGE DOMINATES THE REMAINDER OF
THE TROPICAL ATLC TO 43W S OF THE UPPER TROUGH MENTIONED ABOVE.
OTHERWISE THE ATLC IS DOMINATED BY A WEAK BUT BROAD SURFACE
RIDGE BETWEEN 28W-65W ANCHORED BY A 1023 MB HIGH NEAR 32N41W.

$$
WALLACE





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