[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 17 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.

...TROPICAL WAVES...
TROPICAL WAVE IS BETWEEN THE WEST AFRICAN COAST AND THE CAPE
VERDE ISLANDS ALONG 20W/21W S OF 18N MOVING W 10-15 KT. A BAND
OF MODERATE CONVECTION IS FROM 10N-11N BETWEEN 18W-20W...NEAR
THE INTERSECTION OF THE WAVE AND THE ITCZ AXIS.

LOW AMPLITUDE TROPICAL WAVE IS ALONG 39W/40W S OF 14N MOVING W
10 KT. ISOLATED SHOWERS ARE OCCURRING 150 NM ON EITHER SIDE OF
THE WAVE AXIS S OF 9N. TOTAL PRECIPITABLE WATER FIELDS DEPICT
ENHANCED DEEP LAYER MOISTURE IN THE VICINITY OF THE WAVE
AXIS...PARTICULARLY OVER ITS SOUTHERN HALF.

TROPICAL WAVE IS IN THE E CARIBBEAN ALONG 64W S OF 20N MOVING W
10 KT. ISOLATED SHOWERS ARE OCCURRING IN AN AREA WITHIN 150 NM
EAST OF THE WAVE AXIS NORTH OF 11N. RECENT VISIBLE SATELLITE
IMAGERY INDICATES THE DEVELOPMENT OF A LOW LEVEL CIRCULATION
JUST N OF THE WAVE...WHERE MODERATE CONVECTION IS FROM 22N-25N
BETWEEN 62W-65W.

TROPICAL WAVE IS OVER THE WEST CARIBBEAN SEA ALONG 83W S OF 20N
MOVING W 10-15 KT GENERATING CLUSTERS OF SCATTERED MODERATE
CONVECTION WITHIN 75 NM EITHER SIDE OF THE WAVE AXIS S OF 15N
INCLUDING COASTAL AREAS OF E HONDURAS/NICARAGUA.

TROPICAL WAVE IS OVER S MEXICO ALONG 93W S OF 18N MOVING W 10-15
KT. ALL CONVECTION IS IN THE E PACIFIC REGION ALONG THE COAST OF
MEXICO IN THE GULF OF TEHUANTEPEC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N17W 9N27W 10N37W 10N79W. BESIDES
THE CONVECTION MENTIONED IN THE TROPICAL WAVE SECTION...
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS OCCURRING FROM
11N-15N E OF 17W INLAND OVER W AFRICA. ISOLATED MODERATE
CONVECTION IS FROM 6N-12N BETWEEN 50W-63W.

...DISCUSSION...

GULF OF MEXICO...
A STATIONARY FRONT IS DRAPED FROM THE W ATLC ACROSS NE FLORIDA
INTO THE GULF N OF TAMPA ALONG 25N92W INTO THE BAY OF CAMPECHE.
MODERATE WINDS ARE N AND W OF THE FRONT ESPECIALLY OFF THE SE
MEXICAN COAST. SCATTERED SHOWERS ARE OCCURRING AS A RESULT OF
ENHANCED LOW LEVEL CONVERGENCE IN THE VICINITY OF THE FRONT OVER
THE WESTERN GULF FROM 19N-25N BETWEEN 91W-98W. THIS CONVECTION
IS FURTHER BEING ENHANCED BY UPPER LEVEL DIFFLUENCE ON THE
EASTERN PERIPHERY OF AN UPPER LEVEL ANTICYCLONE OVER CENTRAL
MEXICO NEAR 21N99W. THE CIRCULATION AROUND THIS ANTICYCLONE IS
RESULTING IN NORTHWESTERLY UPPER LEVEL FLOW OVER MUCH OF THE
GULF. WEAK UPPER LEVEL CONVERGENCE OVER THE CENTRAL AND EASTERN
GULF COMBINED WITH MID/UPPER LEVEL DRY AIR ARE RESULTING IN FAIR
WEATHER OVER THE CENTRAL AND EASTERN GULF...ALTHOUGH ISOLATED
SHOWERS AND THUNDERSTORMS COULD DEVELOP OVER THE SE GULF
EXTENDING FROM 25N84W TO 23N89W...AS WELL AS OVER SOUTH FLORIDA
IN RESPONSE TO SEA BREEZE CONVERGENCE PROCESSES.

CARIBBEAN SEA...
TWO TROPICAL WAVES ARE OVER THE CARIBBEAN SEA AND CENTRAL
AMERICA. SEE ABOVE. LARGE CLUSTERS OF MODERATE WITH ISOLATED
STRONG CONVECTION CONTINUE AFFECTING THE CENTRAL CARIBBEAN FROM
9N-17N BETWEEN 70W-77W. THIS CONVECTION IS BEING AIDED BY UPPER
LEVEL DIFFLUENCE IN NORTHERLY FLOW ALOFT COMBINED WITH THE
PRESENCE OF DEEP LAYER MOISTURE. THIS NORTHERLY FLOW ALOFT IS ON
THE WESTERN PERIPHERY OF AN UPPER LEVEL TROUGH ANCHORED BY AN
UPPER LEVEL CYCLONE LOCATED NEAR 20N67W. MOIST SOUTHWESTERLY
FLOW DOWNSTREAM OF THIS TROUGH AXIS IS SUPPORTING ISOLATED
SHOWERS OVER THE LESSER ANTILLES. UPPER LEVEL CONFLUENCE IN DRY
MID-LEVELS IS RESULTING IN FAIR WEATHER CONDITIONS ACROSS MUCH
OF THE CENTRAL AND NORTHERN CARIBBEAN. SCATTERED MODERATE
CONVECTION WILL CONTINUE NEAR THE EASTERN COAST OF CENTRAL
AMERICA AS THE WESTERN CARIBBEAN TROPICAL WAVE MOVES WESTWARD.

ATLANTIC OCEAN...
LIGHT WESTERLY FLOW ALOFT IS OCCURRING ACROSS MUCH OF THE
TROPICAL ATLANTIC. IN THE W TROPICAL ATLC AN UPPER HIGH IS NEAR
15N50W PRODUCING STRONG UPPER LEVEL FLOW TO THE W OF THE HIGH.
CLUSTERS OF MODERATE CONVECTION EAST OF THE LESSER ANTILLES ARE
FROM 8N-18N BETWEEN 50W-62W RESULTING FROM MOIST ATMOSPHERIC
LIFT. MOISTURE IN MODERATE UPPER LEVEL FLOW NEAR THE BASE OF AN
UPPER LEVEL TROUGH OVER THE NORTHEASTERN ATLANTIC IS SUPPORTING
SCATTERED SHOWERS FROM 27N-30N BETWEEN 15W-40W. ALSO...A SURFACE
TROUGH TRAILING SOUTHWESTWARD FROM 32N62W TO 26N70W IS
GENERATING SCATTERED SHOWERS AND POSSIBLE THUNDERSTORMS 100 NM
EITHER SIDE OF THE TROUGH AXIS. ELSEWHERE ACROSS THE
ATLANTIC...MAINLY FAIR WEATHER CONDITIONS ARE THE RULE WITH A
SURFACE RIDGE EXTENDING SOUTHWESTWARD ACROSS THE CENTRAL
ATLANTIC ANCHORED BY A 1023 MB SURFACE HIGH NEAR 34N43W.

$$
COHEN/WALLACE

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