[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 130537
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST WED DEC 13 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...
METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0515 UTC.

...THE ITCZ...
ITCZ AXIS IS ALONG 7N12W 5N27W 3N40W 1N50W. SCATTERED MODERATE
CONVECTION IS WITHIN 180 NM EITHER SIDE OF THE AXIS BETWEEN
24W-36W. ISOLATED MODERATE IS WITHIN 150 NM S OF THE AXIS E OF
18W.

...DISCUSSION...
THE GULF OF MEXICO...
THERE ARE A COUPLE WEAK FEATURES IN THE GULF PRODUCING AREAS OF
CLOUDINESS AND SOME SHOWER ACTIVITY. ONE IS A VERY WEAK FRONTAL
BOUNDARY WHICH HAS NOW GONE STATIONARY FROM ERN LOUISIANA TO
26N91W. ONLY A SLIGHT TEMP AND DEWPOINT DROP ARE NOTED BEHIND
THE FRONT. SFC WINDS HAVE A NLY COMPONENT BEHIND THE FRONT...
WHICH IS THE MAIN COMPONENT IN FINDING THIS BOUNDARY...BUT ARE
LIGHT AND THEN APPEAR TO BE RATHER VARIABLE WELL BEHIND THE
FRONT IN TEXAS. ASSOCIATED SHOWER ACTIVITY IS IN THE WARM SECTOR
E OF THE WEAK FRONT. MOSAIC DOPPLER RADAR FROM THE SE U.S.
DEPICTS SCATTERED SHOWERS AND TSTMS ACROSS THE WRN PORTION OF
THE FLA PANHANDLE EXTENDING NWD ACROSS ALABAMA AND GEORGIA.
LIGHTER MORE ISOLATED SHOWER ACTIVITY EXISTS FURTHER E IN THE
FLORIDA PENINSULA. THE OTHER WEAK FEATURE IS A SFC TROUGH WHICH
RUNS FROM 24N88W SWD ACROSS THE YUCATAN AND INTO THE WRN CARIB.
FAIRLY WELL DEFINED BUT BROAD LOW-MID LEVEL CYCLONIC TURNING IS
NOTED ABOUT THE TROF AXIS. CONSIDERABLE CLOUDINESS AND ISOLATED
TO SCATTERED SHOWERS ARE WITHIN 240 NM E OF THE AXIS. LOOKING
AHEAD OVER THE NEXT COUPLE OF DAYS...THE WEAK FRONT WILL SLOWLY
PROPAGATE E AS A SHORTWAVE TROF CURRENTLY OVER THE SWRN U.S.
APPROACHES THE AREA. GFS DRIFTS THE TROUGH IN THE SRN GULF NWD
AND DEVELOPS IT INTO A WEAK LOW AND THEN TRACKS IT ACROSS FL.
THERE IS MUCH UNCERTAINTY IN THIS SCENARIO AS THERE IS NOT MUCH
AGREEMENT IN THE MODELS AND IN EACH INDIVIDUAL RUN.

THE CARIBBEAN SEA...
THERE IS SOME INSTABILITY IN THE WRN CARIB DUE TO A SFC TROUGH
WHICH EXTENDS FROM HONDURAS NWD ACROSS THE NE YUCATAN PENINSULA
AND INTO THE SRN GULF. SFC OBS...SATELLITE IMAGERY ALONG WITH
LOW-LEVEL SAT DERIVED WINDS SHOW A BROAD AREA OF CYCLONIC
TURNING IN THE REGION. SCATTERED SHOWERS AND ISOLATED TSTMS
APPEAR TO BE CONFINED TO WITHIN 200 NM E OF THE TROUGH AXIS
BASED ON CLOUD TOP TEMPS ON IR IMAGERY. GFS SHOWS THIS FEATURE
PULLING NWD AND POSSIBLY CLOSING OFF LATER THIS WEEK. FOR MORE
DETAILS REFER TO THE GULF OF MEXICO SECTION ABOVE. ANOTHER SFC
TROUGH IS IN THE SW CARIB ANALYZED FROM 10N80W TO 15N81W.
HOWEVER...THIS TROUGH IS LESS DEFINED AND BASED MOSTLY ON SOME
CYCLONIC TURNING IN THE WINDS EVIDENT IN AN EARLIER QSCAT PASS.
SOME LIFT NEAR THE SFC TROUGH ALONG WITH WEAK UPPER
DIFFLUENCE...BETWEEN A BROAD FLAT RIDGE CENTERED OVER COLOMBIA
AND STRONGER UPPER LEVEL WLY FLOW IN THE NW CARIB...IS SPARKING
SCATTERED SHOWERS FROM 12N-17N BETWEEN 78W-83W. THE REMAINDER OF
THE CARIB IS QUIET UNDER MODERATELY DRY AIR ALOFT ASSOCIATED
WITH THE BROAD UPPER LEVEL RIDGE. TRADE WINDS ARE MOSTLY IN THE
15-20 KT RANGE EXCEPT FOR SOME STRONGER WINDS IN THE S CENTRAL
CARIB DUE TO LOWER PRES OVER COLOMBIA. NO MAJOR CHANGES IN
THESE WINDS ARE EXPECTED THRU THE WEEK.

THE ATLANTIC OCEAN...
A LONGWAVE RIDGE/TROUGH/RIDGE PATTERN IS ESTABLISHED ACROSS THE
DISCUSSION AREA. VERTICALLY STACKED RIDGING EXISTS IN THE WRN
ATLC WITH THE MEAN AXIS ALONG 70W. A BAND OF STRONG MID-UPPER
LEVEL WINDS OR A WEAK JET STRETCHES FROM THE BAHAMAS EASTWARD TO
21N50W THEN RACING NWD IN RESPONSE TO THE TROUGH IN THE CENTRAL
ATLC.  N OF THE WEAK JET...PLENTY OF DRY STABLE AIR ALOFT EXISTS
W OF 50W. THIS STRONG MID-LEVEL CAP IS KEEPING THE PATCHES OF
LOW-LEVEL MOISTURE DRIVEN BY FRESH NE-E WINDS SHALLOW. A BROAD
TROUGH DOMINATES THE CENTRAL ATLC WITH THE UPPER AXIS ALONG 45W.
AN ASSOCIATED COLD FRONT EXTENDS FROM 32N43W TO 23N51W. A PLUME
OF MOISTURE ASSOCIATED WITH THE SFC FRONT AND UPPER LEVEL JET
MENTIONED IS N OF 24N BETWEEN 37W-43W. A SECOND REINFORCING
FRONT REMAINS TO THE N BUT MAY MOVE INTO THE DISCUSSION AREA
LATER TODAY. A WEAK SFC TROUGH LIES TO THE SE OF FRONT ALONG 47W
FROM 13N-24N. THIS FEATURE IS NOT PRODUCING ANY NOTABLE WEATHER
BESIDES FOR A BROAD WIND SHIFT. THE SUBTROPICAL E ATLC IS
DOMINATED BY STRONG VERTICALLY STACKED RIDGING WITH THE UPPER
HIGH CENTER NEAR 31N23W AND THE 1031 MB SFC CENTER FURTHER TO
THE NE. A WEAKENING CUT OFF UPPER LEVEL LOW IS EMBEDDED IN THE
LARGE SCALE RIDGE NEAR 25N29W. THIS UPPER LEVEL FEATURE IS ONLY
PRODUCING SOME ISOLATED SHOWERS NEAR IT AND IT APPEARS THAT IT
WILL BE COMPLETELY OVERTAKEN BY A NARROW RIDGE TO ITS W AS
SUGGESTED BY GFS.

$$
CANGIALOSI







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