[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201738
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON OCT 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
1700 UTC.

...SPECIAL FEATURES...
SCATTERED MODERATE TO STRONG CONVECTION IN THE NW CARIBBEAN IS
ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE CENTERED NEAR
17N86W...OR ABOUT 100 NM E OF THE COAST OF BELIZE. CONVECTION IS
MOST PROMINENT N OF 16N AND W OF 80W. THE LOW IS NEARLY
STATIONARY AND SFC OBSERVATIONS IN THE VICINITY INDICATE RISING
PRESSURE. NE TO E WINDS 15-20 KT ARE OBSERVED TO THE NORTH AND
EAST OF THE LOW. ANY TROPICAL DEVELOPMENT OF THESE SYSTEM WILL
BE SLOW TO OCCUR...HOWEVER...HEAVY RAIN WILL PERSIST OVER
PORTIONS OF HONDURAS...GUATEMALA...BELIZE...THE YUCATAN
PENINSULA...AND THE NW CARIBBEAN SEA OVER THE NEXT COUPLE OF
DAYS.

...TROPICAL WAVES...
A TROPICAL WAVE HAS EMERGED OFF THE WEST COAST OF AFRICA AND IS
ANALYZED ALONG 19W S OF 14N. UPPER AIR OBSERVATIONS AT
DAKAR...SENEGAL INDICATE THE WAVE PASSED THE STATION NEAR 00Z
THIS MORNING. INITIAL MOTION ESTIMATES MOVE THE WAVE WESTWARD AT
10-15 KT. VISIBLE SATELLITE IMAGERY REVEAL BROAD CYCLONIC
CIRCULATION AND A DISTINCT INVERTED-V CLOUD SIGNATURE AROUND THE
WAVE AXIS. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 150
NM AHEAD...100 NM BEHIND THE AXIS FROM 8N-11N.

A TROPICAL WAVE IS ALONG 45W S OF 18N MOVING W NEAR 10 KT.MIMIC
TPW PRODUCT INDICATES THE WAVE AXIS IS ALONG THE LEADING EDGE OF
A MOISTURE SURGE...HOWEVER...CONVECTION PREVIOUSLY SURROUNDING
THE WAVE IS RAPIDLY BEING DRAWN NORTHWARD BY AN UPPER-LEVEL LOW
NEAR 20N49W.

A TROPICAL WAVE IN THE CARIBBEAN HAS BEEN RE-LOCATED TO ALONG
70W S OF 15N. E TO SE WIND SHIFTS CORRESPONDING TO A WAVE
PASSAGE OCCURRED AT THE SFC STATIONS IN THE NETHERLANDS ANTILLES
EARLY THIS MORNING. IN ADDITION...UPPER AIR DATA FROM TRINIDAD
AND TOBAGO INDICATE THE WAVE PASSED THE STATION NEAR 12Z ON OCT
18. THIS DATA IS THE BASIS BEHIND THE RE-LOCATION OF THE AXIS.
RELATIVE VORTICITY FROM THE CMISS WAVETRAK PRODUCT SUPPORT THE
LOCATION OF THE AXIS. SCATTERED MODERATE CONVECTION IS BETWEEN
70W-71W FROM 12N-14N.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 9N18W 4N31W 9N47W TO 9N61W. IN
ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL
WAVES...SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE
AXIS BETWEEN 24W-29W. SIMILAR CLUSTERS OF MODERATE CONVECTION
ARE BETWEEN 49W-60W FROM 10N-13N. THIS AREA OF CONVECTION IS
BEING ENHANCED BY UPPER-LEVEL FEATURES.

...DISCUSSION...

GULF OF MEXICO...
A MUCH DRIER AIR MASS WAS LEFT IN THE WAKE OF A COLD FRONT THAT
EXITED THE GULF REGION EARLY THIS MORNING. A SFC HIGH OVER THE
SE CONUS EXTENDS A RIDGE ACROSS THE NORTHERN GULF WITH E TO NE
WINDS 10-15 KT COVERING THE AREA N OF 26N. WINDS INCREASE S OF
26N TO 20 KT IN THE VICINITY OF THE AFOREMENTIONED FRONTAL
BOUNDARY WHICH NOW SPANS THE YUCATAN PENINSULA. ISOLATED SHOWERS
ARE MOVING THROUGH THE STRAIGHTS OF FLORIDA..OTHERWISE
CONVECTION IS LIMITED UNDER STRONG SUBSIDENCE ALOFT AND ONLY
PATCHY CLOUDS ARE OBSERVED ON SATELLITE IMAGERY. EXPECT THE
RIDGE ACROSS THE NORTHERN GULF TO WEAKEN IN ADVANCE OF A WEAK
FRONT FORECAST TO MOVE OVER THE SE CONUS TUE NIGHT.

CARIBBEAN SEA...
MOIST SW FLOW ON THE LEADING EDGE OF UPPER TROUGH AXIS IN THE
GULF OF MEXICO CONTINUES TO MOVE OVER THE NW CARIBBEAN...WHERE
UPPER LEVEL DIVERGENCE CONTINUES TO ENHANCE CONVECTION AROUND A
1010 MB SFC LOW. SEE SPECIAL FEATURES SECTION FOR MORE DETAILS.
A STATIONARY FRONT REMAINS SITUATED ACROSS CUBA THROUGH THE
YUCATAN CHANNEL AND INTO THE YUCATAN PENINSULA. EXPECT THIS
BOUNDARY TO DISSIPATE IN THE NEXT 24 HOURS. UPPER-LEVEL
DIVERGENCE IS GENERATING AN AREA OF MODERATE CONVECTION FROM
12N-17N BETWEEN 78W-81W. THIS CONVECTION IS MOVING RAPIDLY
TOWARD THE WNW IN MODERATE TRADE WIND FLOW. FURTHER
EAST...CONVECTION IS LIMITED DUE TO MODERATE SUBSIDENCE ON THE
SE QUADRANT OF AN UPPER-LEVEL HIGH.

ATLANTIC OCEAN...
A DEEP LAYER TROUGH OVER THE W ATLC IS SUPPORTING A COLD FRONT
THAT...AS OF 15Z...ENTERS THE DISCUSSION AREA NEAR 31N63W AND
EXTENDS ALONG 24N70W TO 22N79W WHERE IT BECOMES STATIONARY
ACROSS CUBA. SCATTERED SHOWERS EXTEND UP TO 60 NM EITHER SIDE OF
THE FRONT. TO THE EAST...A WEAK SFC LOW PRESSURE WAS EVIDENT ON
SATELLITE IMAGERY AS WELL AS IN THE QUIKSCAT WIND DATA NEAR
24N60W. A SMALL CLUSTER OF MODERATE CONVECT ASSOCIATED WITH THIS
FEATURE FLARED UP FROM 24N-25N BETWEEN 58W-59W. THIS CONVECTION
IS SHORT-LIVED DUE TO STRONG WLY SHEAR ALOFT. AT THE
SFC...STRONG HIGH PRESSURE DOMINATES THE ATLC E OF
55W...HOWEVER...A LARGE UPPER-LEVEL LOW NEAR 21N50W AND AN
UPPER-LEVEL HIGH NEAR 20N37W CONTINUE TO FUNNEL DEEP-LAYER
TROPICAL MOISTURE NORTHWARD INTO THE CENTRAL ATLC. THESE UPPER
FEATURES ARE RESULTING IN SCATTERED MODERATE CONVECTION FROM
12N-26N BETWEEN 35W-46W. UPPER-LEVEL DIVERGENCE SOUTH OF THE
UPPER-LEVEL LOW IS ENHANCING CONVECTION ALONG THE ITCZ FROM 78W
TO THE WINDWARD ISLANDS.


$$
WADDINGTON




This weather bulletin was brought to you by:
www.nashvilleweather.net