[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121755
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU OCT 12 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
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...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
SHOWERS AND THUNDERSTORMS OVER THE EASTERN CARIBBEAN SEA AND
WESTERN ATLANTIC OCEAN ARE ASSOCIATED WITH A WEAK AREA OF LOW
PRESSURE BETWEEN PUERTO RICO AND THE NORTHERN LEEWARD ISLANDS.
THIS SYSTEM HAS NOT BECOME ANY BETTER-ORGANIZED THIS MORNING AND
ENVIRONMENTAL CONDITIONS ARE FORECAST TO BECOME LESS FAVORABLE
FOR DEVELOPMENT THANKS TO THE PRESENCE OF AN UPPER TROUGH
LOCATED JUST WEST OF PUERTO RICO. THE CHANCE FOR A TROPICAL
DEPRESSION TO FORM IN THIS AREA IS DECREASING. LOCALLY HEAVY
RAIN AND GUSTY WINDS WILL CONTINUE TO SPREAD ACROSS THE
NORTHEASTERN CARIBBEAN SEA AND ADJACENT LAND AREAS TODAY AND
TONIGHT AS THE SYSTEM MOVES WEST-NORTHWESTWARD BETWEEN 10 TO 15
MPH. LATEST SATELLITE IMAGERY SHOWS THAT THE CLOUD TOPS ARE
WARMING UP. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
FOUND 12N-22N BETWEEN 60W-64W. LATEST SATELLITE PICTURES SUGGEST
THAT A NEW CIRCULATION SEEMS TO BE FORMING FARTHER NORTH NEAR
22N65W.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 36W S OF 18N MOVING W 10 KT. A 1010
SURFACE LOW HAS FORMED ALONG THE WAVE AXIS NEAR 13N THIS
MORNING. DEVELOPMENT IS NOT ANTICIPATED DUE TO STRONG
UPPER-LEVEL WINDS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS SEEN FROM 12N-15N BETWEEN 31W-36W.

A LARGE TROPICAL WAVE IS ALONG 64W S OF 22N. A 1010 MB SURFACE
LOW IS ALONG THE WAVE AXIS NEAR 18N. SEE SPECIAL FEATURE FOR
MORE DETAILS.

TROPICAL WAVE IS ALONG 77W S OF 20N MOVING W 10 KT. BROAD LOW
LEVEL INVERTED-V STRUCTURE IS NOTED ON SATELLITE IMAGERY. THIS
SYSTEM IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
VERY CLOSE TO THE COLOMBIAN COAST.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 1ON14W 8N25W 8N34W 8N45W 10N60W
WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 100/120 NM ON
EITHER SIDE OF THE AXIS WEST OF 30W. SIMILAR CONVECTION IS FOUND
MAINLY NORTH OF THE AXIS BETWEEN 38W-48W. CLUSTER OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE INLAND OVER AFRICA FROM
8N-13N BETWEEN 10W-16W.

...DISCUSSION...
GULF OF MEXICO...
DEEP LAYERED TROUGH IS MOVING RAPIDLY EASTWARD ACROSS THE
EASTERN US. THE ASSOCIATED FRONTAL BOUNDARY IS INLAND AND
EXTENDS FROM NORTHERN GEORGIA TO TEXAS. THE COLD FRONT WILL MOVE
INTO THE NW GULF OVERNIGHT AND EXTEND FROM NEAR TAMPA BAY
THROUGH 27N90W TO THE DEEP SOUTH LATE FRI. A WEAKENING FRONTAL
TROUGH IS AHEAD OF THIS FRONT AND ENTERS THE AREA NEAR 31N80W...
28N83W 25N88W. A NARROW BAND OF SHOWERS WITH EMBEDDED TSTMS IS
RELATED TO THE TROUGH AND IS APPROACHING NOW TO THE TAMPA BAY
AREA. A VERY LARGE MID/UPPER ANTICYCLONE CENTERED OVER CENTRAL
MEXICO NEAR 20N98W COVERS THE ENTIRE GULF...THE FLORIDA
PENINSULA... CUBA...THE WESTERN CARIBBEAN AND CENTRAL AMERICA
GIVING THE AREA DRY AIR AND A SUBSIDENCE PATTERN. THIS FRONT
PROMISES TO BRING THE COLDEST AIR OF THE SEASON SO FAR ACROSS
THE CENTRAL AND EAST PARTS OF THE U.S. THE FRONT WILL MODE
ACROSS SOUTH FLORIDA LATE SATURDAY INTO SUNDAY. TEMPERATURES MAY
DROP A FEW DEGREES BELOW NORMAL.

CARIBBEAN SEA...
THE MAIN WEATHER FEATURE TODAY ACROSS THE BASIN IS THE WEAK AREA
OF LOW PRESSURE LOCATED BETWEEN PUERTO RICO AND THE NORTHERN
LEEWARD ISLANDS. SEE SPECIAL FEATURE. AN UPPER TROUGH IN THE W
ATLC EXTENDS S INTO THE CARIBBEAN ACROSS HISPANIOLA. THIS UPPER
TROUGH WILL CONTINUE TO MOVE EASTWARD TODAY AND TONIGHT AND MAY
INTERACT WITH THE TROPICAL WAVE LOCATED CURRENTLY ALONG
64W...BRINGING THE POTENTIAL OF HEAVY RAIN TO PUERTO RICO AND
THE VIRGIN ISLANDS FRIDAY TROUGH SATURDAY AND PROBABLY BEYOND.
THE RISK OF FLASH AND RIVER FLOODING AND POSSIBLE MUD SLIDES
OVER MOUNTAINOUS TERRAIN WILL INCREASE. BROAD RIDGE ANCHORED IN
THE TROPICS NEAR 16N58W COVERING MOST OF THE CENTRAL ATLC
INCLUDES THE FAR E CARIBBEAN. UPPER DRY AIR DOMINATES THE
CARIBBEAN SEA WEST OF 67W. SCATTERED SHOWERS AND ISOLATED TSTMS
ARE FROM NORTHERN COLOMBIA TO COSTA RICA DUE TO THE PRESENCE OF
THE ITCZ AXIS. UNUSUAL LIGHT TRADE WINDS OF 10 KT DOMINATES THE
SOUTHERN CARIBBEAN.

ATLANTIC OCEAN...
A LINE OF SHOWERS WITH EMBEDDED TSTMS...PREVIOUSLY ASSOCIATED
WITH AND OLD FRONTAL BOUNDARY EXTENDS FROM 30N68W TO THE
NORTHERN BAHAMAS INTO SOUTH FLORIDA. DOPPLER RADAR IS SHOWING
MORE SHOWERS AND TSTMS APPROACHING SOUTH FLORIDA UNDER A WLY
WIND FLOW. AN UPPER TROUGH ENTERS THE AREA NEAR 31N70W THEN
CONTINUES S INTO THE CARIBBEAN SEA ACROSS HISPANIOLA. UPPER
DIFFLUENCE AHEAD OF THIS TROUGH IS ENHANCING THE CONVECTIVE
ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE/LOW LOCATED OVER THE
EASTERN CARIBBEAN.  RIDGE DOMINATES THE CENTRAL ATLC ANCHORED IN
THE TROPICS NEAR 16N58W COVERING THE AREA FROM 48W-65W. UPPER
TROUGH IS OVER THE E ATLC WITH THE AXIS EXTENDING ALONG 22/23W.
THE BASE OF THIS TROUGH REACHES THE CAPE VERDE ISLANDS. AN UPPER
RIDGE COVERS WESTERN AFRICA. AT THE SURFACE A BROAD SURFACE
RIDGE COVERS THE ATLC E OF 55W WITH A 1020 MB HIGH LOCATED NEAR
29N48W. AN AREA OF SCATTERED SHOWERS IS FROM 20N-24N BETWEEN
30W-41W AHEAD OF A SHORT WAVE TROUGH THAT LIES ALONG 43W.

$$
GR









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