[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 192357
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 19 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS WEST OF THE CAPE VERDE ISLANDS ALONG 28W S OF
17N MOVING W NEAR 10 KT. THIS WAVE IS BENEATH AN UPPER LEVEL
RIDGE AND NO CONVECTION IS NOTED WITH THIS FEATURE.

A TROPICAL WAVE IS ALONG 49W S OF 19N MOVING W NEAR 10 KT. SMALL
SWIRL OF LOW CLOUDS IS ALONG THE WAVE AXIS NEAR 16N. UPPER
DIFFLUENCE IS ENHANCING SOME SHOWER ACTIVITY WITHIN 220 NM E OF
THE AXIS AND WITHIN 180 NM W OF AXIS FROM 13N-18N.

A TROPICAL WAVE...ACCOMPANIED BY A BROAD SURFACE LOW PRESSURE
SYSTEM...CONTINUES TO PRODUCE WIDESPREAD CLOUDINESS AND SHOWERS
OVER THE LESSER ANTILLES...AND ADJACENT CARIBBEAN AND ATLANTIC
WATERS. ITS AXIS IS ALONG 63W SOUTH OF 19N MOVING SLOWLY WWD.
THIS SYSTEM HAS BECOME A LITTLE BETTER ORGANIZED TODAY...AND
ALTHOUGH UPPER-LEVEL WINDS ARE CURRENTLY UNFAVORABLE...THEY ARE
EXPECTED TO BECOME MORE CONDUCIVE FOR SOME ADDITIONAL
DEVELOPMENT TO OCCUR OVER THE NEXT COUPLE OF DAYS.

A TROPICAL WAVE IS ALONG 74W/75W S OF 19N MOVING W 10-15 KT.
SCATTERED MODERATE CONVECTION IS ASSOCIATED WITH THE WAVE OVER
THE CENTRAL CARIBBEAN. THESE SHOWERS ARE BEING SUPPORTED BY AN
UPPER LEVEL TROUGH EXTENDING FROM CENTRAL CUBA TO THE SW
CARIBBEAN.

A TROPICAL WAVE IS OVER SE MEXICO ALONG 92W S OF 19N MOVING W
NEAR 10 KT. MUCH OF THE CONVECTION ASSOCIATED WITH THIS WAVE IS
ON THE PACIFIC SIDE. AS THIS WAVE MOVES W IT WILL BECOME
ABSORBED INTO A LARGE AREA OF DISTURBED WEATHER SSW OF THE GULF
OF TEHUANTEPEC. FOR FURTHER INFORMATION SEE THE TWDEP.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 8N13W 8N25W 7N35W 9N46W 11N60W. A
LARGE AREA OF MODERATE TO STRONG CONVECTION IS APPROACHING THE
WEST COAST OF AFRICA FROM THE EAST. THIS CONVECTIVE ACTIVITY IS
LIKELY ASSOCIATED WITH THE A NEW TROPICAL WAVE. SCATTRED
MODERATE CONVECTION IS FROM 3N-10N BETWEEN 18W-21W. THIS
ACTIVITY IS MOVING WWD UNDER AN ELY WIND FLOW. SCATTERED SHOWERS
ARE ALONG THE REMAINDER OF THE ITCZ AXIS WITH THE EXCEPTION OF A
CLUSTER OF MODERATE/ISOLATED STRONG CONVECTION JUST EAST OF
TRINIDAD AND TOBAGO IN THE WINDWARD ISLANDS. THIS SHOWER/TSTM
ACTIVITY APPEARS TO BE ASSOCIATED WITH THE TROPICAL WAVE OVER
THE EASTERN CARIBBEAN.

...DISCUSSION...

GULF OF MEXICO...
BROAD SURFACE TROUGH COVERS THE WESTERN GULF GENERATING ABUNDANT
CLOUDINESS WITH EMBEDDED SHOWERS AND ISOLATED TSTMS. THE TROUGH
AXIS IS ROUGHLY ALONG 94W. SURFACE DATA CLEARLY INDICATES THE
WIND SHIFT ASSOCIATED WITH THE TROUGH AXIS. A SFC RIDGE
DOMINATES THE SE CONUS AND THE NE PORTION OF THE GULF. THE
TROUGH IS EXPECTED TO PERSIST OVER THE WESTERN GULF DURING THE
UPCOMING WEEKEND AND GRADUALLY DISSIPATE. UPPER DIFFLUENCE
BETWEEN A RIDGE THAT COVERS THE ENTIRE GULF AND AN UPPER-LEVEL
LOW SPINNING OVER THE EASTERN U.S. IS SUPPORTING SOME SHOWER AND
TSTM ACTIVITY OVER THE NE CORNER OF THE GULF NEAR THE FLORIDA
PANHANDLE. A GOOD AMOUNT OF UPPER-LEVEL MOISTURE IS SEEN OVER
THE GULF REGION WHILE SUBSIDENCE/DRY AIR DOMINATES THE FLORIDA
PENINSULA AND THE ADJACENT ATLANTIC WATERS.

CARIBBEAN SEA...
ATTENTION REMAINS FOCUSED ON THE ACTIVE TROPICAL WAVE LOCATED
OVER THE EASTERN CARIBBEAN THAT IS PRODUCING WIDESPREAD
CLOUDINESS AND SHOWERS OVER THE LESSER ANTILLES AND ADJACENT
CARIBBEAN AND ATLANTIC WATERS. CLUSTERS OF MODERATE TO ISOLATED
STRONG CONVECTION COVER THE AREA FROM 11N-18N BETWEEN 56W-61W
MORE CONCENTRATED N OF 14N. MOISTURE AHEAD OF THE WAVE AXIS HAS
ALREADY REACHED THE UK/US VIRGIN ISLANDS WITH THE SAN JUAN
DOPPLER RADAR SHOWING SCATTERED TO NUMEROUS SHOWERS WITH
EMBEDDED TSTMS MOVING WWD ACROSS THESE ISLANDS. THE GFS COMPUTER
MODEL HAS THE DEEP TROPICAL MOISTURE ASSOCIATED WITH THIS WAVE
SPREADING OVER THESE ISLANDS AND THE EASTERN CARIBBEAN LATE
TONIGHT INTO SATURDAY...AND OVER DOMINICAN REPUBLIC ON SUNDAY
AS THE WAVE CONTINUES TO MOVE SLOWLY WWD. SEE ABOVE FOR MORE
DETAILS. ELSEWHERE...CONVECTION HAS FLARED UP ONCE AGAIN OVER
CUBA AND HISPANIOLA. SCATTERED MODERATE CONVECTION DOTS PARTS OF
CENTRAL AMERICA AS WELL AS NORTHERN COLOMBIA AND WESTERN
VENEZUELA WHERE THERE IS A TROPICAL WAVE. MOIST SOUTHWESTERLY
FLOW ALOFT OVER THE CENTRAL AND E CARIBBEAN IN A BROAD UPPER
LEVEL TROUGH THAT EXTENDS FROM CENTRAL CUBA TO NICARAGUA IS
PROMOTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE
CENTRAL CARIBBEAN. A BROAD AREA OF LOW PRESSURE HAS FORMED IN
THIS AREA JUST EAST OF HONDURAS-NICARAGUA BORDER...BUT THE ABOVE
MENTIONED UPPER-LEVEL WINDS/TROUGH ARE CURRENTLY NOT FAVORABLE
FOR ADDITIONAL DEVELOPMENT. THE RIDGE THAT DOMINATES THE GULF OF
MEXICO ALSO EXTENDS OVER THE WESTERN CARIBBEAN AND CENTRAL
AMERICA HELPING TO INDUCE CONVECTION ACROSS THE AREA. MODERATE
TRADE WINDS ARE NOTED ACROSS THE BASIN.

ATLANTIC OCEAN...
A WEAKENING FRONTAL SYSTEM EXTENDS FROM A 1014 MB LOW LOCATED
NEAR 31N72W TO THE NW BAHAMAS NEAR 25N78W. SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ARE WITHIN 100 NM OF FRONT. THIS ACTIVITY
IS BEING ENHANCED BY SOUTHWESTERLY FLOW EAST OF AN UPPER LEVEL
TROUGH ALONG THE CONUS E COAST THAT ALSO SUPPORTS THE ABOVE
MENTIONED FRONT. THIS TROUGH DIGS INTO THE CARIBBEAN SEA ACROSS
CENTRAL CUBA. N TO NE WINDS OF 15-20 KT ARE BEHIND THE FRONT
OVER THE FAR NW PORTION OF THE DISCUSSION AREA. FURTHER EAST...A
BROAD UPPER-LEVEL LOW IS SPINNING OVER THE CENTRAL ATLC NEAR
26N45W. ONLY ISOLATED SHOWERS ARE RELATED TO THIS UPPER-LEVEL
FEATURE. A PAIR OF TROPICAL WAVES ARE MOVING WWD ACROSS THE
TROPICAL ATLC...AND A NEW ONE APPEARS TO MOVE OFF THE WEST
AFRICAN COAST. N OF 20N...A SURFACE RIDGE DOMINATES THE FORECAST
REGION BRINGING MOSTLY FAIR WEATHER TO MUCH OF THE AREA. STRONG
UPPER-LEVEL HIGH LOCATED INLAND OVER WEST AFRICA HAS A RIDGE
EXTENDING WWD TO ABOUT 38W ENVELOPING THE CAPE VERDE ISLANDS.

$$
GR




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