[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081728
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN OCT 08 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.

...TROPICAL WAVES...
A HIGH AMPLITUDE LARGE TROPICAL WAVE IS ALONG 47W S OF 21N
MOVING W 15 TO 20 KT OVER THE PAST 24 HOURS. THE WAVE AXIS
CONTINUES TO BE EASY TO LOCATE ON SATELLITE IMAGERY WITH AN
INVERTED-V STRUCTURE NOTED. SCATTERED MODERATE CONVECTION
EXISTS ACROSS A VERY LARGE AREA EMBEDDED IN THE ITCZ WITHIN
SEVERAL HUNDRED NM EITHER SIDE OF THE WAVE AXIS FROM 5N TO 18N
BETWEEN 30W AND 60W. THE STRONGEST CONVECTION IS FROM 10N TO 12N
BETWEEN 46W AND 51W. THIS WAVE IS AN UNFAVORABLE ENVIRONMENT
WITH 40 TO 50 KT SW TO W UPPER LEVEL WINDS BLOWING ACROSS THE
WAVE...WHICH IS SPREADING ITS MOISTURE FAR TO THE E.

A TROPICAL WAVE IS ALONG 61W/62W S OF 16N MOVING W NEAR 15 KT.
THIS WAVE HAS LITTLE SIGNATURE ASSOCIATED WITH IT AND THE PSN IS
BASED ON CONTINUITY. LITTLE...IF ANY SHOWER ACTIVITY IS
ASSOCIATED WITH THIS FEATURE...LIKELY DUE TO THE DRY STABLE MID
AND UPPER LEVEL ENVIRONMENT ABOVE THE WAVE. A 0922 UTC QUIKSCAT
PASS SHOWS AN AREA OF 20 TO 25 KT WINDS E OF THE WAVE
AXIS...SUGGESTING THAT THE WAVE MIGHT HAVE HELPED TIGHTENED THE
PRES GRAD SLIGHTLY.

A TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 71W S OF 19N
MOVING W 10 TO 15 KT. SIMILARITY TO THE WAVE TO ITS EAST
...LITTLE WAVE STRUCTURE IS NOTED ON VIS IMAGES AND NO ORGANIZED
SHOWER ACTIVITY IS ASSOCIATED WITH THIS FEATURE. WESTERLY UPPER
LEVEL FLOW IS PROVIDING AN UNFAVORABLE ENVIRONMENT.

A TROPICAL WAVE IS ADJUSTED ALONG 95W S OF 19N MOVING W 10 TO 15
KT. THIS WAVE ADJUSTMENT IS BASED ON LOW-MID LEVEL CYCLONIC
TURNING NEAR 10N. ISOLATED MODERATE CONVECTION IS WITHIN 4-5
DEGREES OF THE WAVE AXIS.

...THE ITCZ...
ITCZ AXIS IS CENTERED 12N15W 10N33W 11N46W 9N49W 8N61W. ALL OF
THE SIGNIFICANT CONVECTION IN THE ITCZ IS ASSOCIATED WITH THE
LARGE TROPICAL WAVE ALONG 47W. FOR DETAILS REFER TO THAT SECTION.

...DISCUSSION...
THE GULF OF MEXICO...
THE EASTERN GULF IS NEAR THE BASE OF A LARGE CUT OFF UPPER LOW
WHICH HAS BEEN MOVING SWD NEAR 10 KT OVER THE LAST 24 HOURS.
STRONG SUBSIDENCE ACCOMPANIES THE TROUGH PRODUCING VERY DRY AIR
ALOFT NOTED ON WATER VAPOR IMAGES E OF 88W N OF 25N. AN
ASSOCIATED SLOW MOVING COLD FRONT EXTENDS FROM CENTRAL FLORIDA
WESTWARD TO NEAR 28N92W. ONLY SLIGHTLY DRIER AIR AND A FAINT
NARROW BAND OF LOW CLOUDS REPRESENT THIS BOUNDARY. A NARROW
SQUASHED RIDGE LIES TO THE W OF THE TROUGH EXTENDING FROM THE
YUCATAN PENINSULA NWD TO LOUISIANA. THIS RIDGE BROADENS AND
BECOMES A HIGHER AMPLITUDE ELONGATED RIDGE ACROSS THE
CENTRAL-EASTERN U.S. A FAIR AMOUNT OF MOSTLY MID-HIGH LEVEL
MOISTURE IS IN THE WRN GULF ASSOCIATED WITH THE MOIST SWLY FLOW
OF THE UPPER RIDGE. A WELL-DEFINED SFC TROUGH LIES UNDER THE
RIDGE ALONG 96W FROM 21N TO 27N HELPING TO DEEPEN SOME OF THE
AVAILABLE MOISTURE IN PRODUCING SCATTERED SHOWERS WITHIN 180 NM
E OF THE TROUGH AXIS. HOWEVER...THE BULK OF THE MOISTURE LIES TO
THE S OF THE AREA SUPPORTED BY UPPER DIFFLUENCE AND ADVECTED BY
A WESTERLY JET. GFS SHOWS THE DRY AIRMASS IN THE CENTRAL AND
EASTERN GULF SLOWLY PUSHING E OVER THE NEXT COUPLE OF DAYS.
LOOKING FURTHER AHEAD...A POTENTIALLY STRONG COLD FRONT FOR THIS
TIME OF YEAR MAY ENTER THE NRN GULF BY MID-WEEK.

THE CARIBBEAN SEA...
VERY ACTIVE WEATHER IS OCCURRING IN THE WRN CARIBBEAN AND ACROSS
PORTIONS OF COLOMBIA AND SRN CENTRAL AMERICA WHERE LARGE
CLUSTERS OF SCATTERED MODERATE TO OCCASIONALLY STRONG CONVECTION
EXISTS. A SFC TROUGH HAS BEEN ADDED TO THE 12 UTC ANALYSIS ALONG
10N82W 17N87W BASED ON LOW-MID LEVEL CLOUD SWIRLS AND VORTICITY
MAXIMUMS ALONG THIS AXIS. MOST OF THE CONVECTION LIES WITHIN 300
NM TO THE E OF THE SFC BOUNDARY. THIS CONVECTIVE ACTIVITY IS
BEING HIGHLY ENHANCED BY AN UPPER DIFFLUENT PATTERN AND AN
ABUNDANT AMOUNT OF TROPICAL MOISTURE ASSOCIATED WITH THE ITCZ.
A WESTERLY JET WITH CORE WINDS BETWEEN 40 AND 60 KT BASED ON
CIMSS DERIVED WINDS IS CARRYING SOME OF THIS MOISTURE ACROSS
CUBA AND INTO THE ATLC WHERE IT IS THEN ENHANCED BY A SFC
BOUNDARY. THE CENTRAL AND EASTERN CARIBBEAN IS QUIET WITH A FAIR
AMOUNT OF MODERATELY DRY AIR AND WESTERLY UPPER LEVEL FLOW IN
PLACE. HOWEVER MOISTURE WILL BE INCREASING ACROSS THE LESSER
ANTILLES LATER TODAY AND IT SHOULD REMAIN RATHER MOIST OVER THE
NEXT COUPLE OF DAYS AS THE WRN EDGE OF SHOWERS ASSOCIATED WITH A
LARGE TROPICAL WAVE MOVES INTO THE AREA AND SPREADS W.

THE ATLANTIC OCEAN...
A WELL-DEFINED UPPER LEVEL TROUGH/RIDGE/TROUGH PATTERN IS
ESTABLISHED ACROSS THE ATLC BASIN. A LARGE UPPER LEVEL TROUGH
COVERS MUCH OF THE EASTERN U.S. AND WRN ATLC W OF 70W N OF 24N
ANCHORED BY A LARGE UPPER LOW OVER SE GEORGIA. MODERATE TO
STRONG DRY STABLE AIR IS ASSOCIATED WITH THE TROUGH. AN
ASSOCIATED COLD FRONT EXTENDS FROM A 1014 MB LOW NEAR 33N79W TO
30N78W THEN SW TO CENTRAL FLORIDA. A MID-UPPER LEVEL SUBTROPICAL
RIDGE LIES TO THE E OF THE TROUGH AND COVERS THE REGION BETWEEN
38W AND 63W. DRY STABLE AIR IS ALSO IN PLACE UNDERNEATH THE
RIDGE LIMITING ANY SHOWER ACTIVITY. A SWLY JET EXISTS BETWEEN
THESE FEATURES AND IS ADVECTING A SWATH OF DEEP TROPICAL
MOISTURE BETWEEN 63W AND 70W. A SFC TROUGH ALONG 29N66W TO THE
CENTRAL BAHAMAS IS PROVIDING MORE LIFT GENERATING SCATTERED
MODERATE CONVECTION WITHIN 300 NM E AND 180 NM W OF THE AXIS.
THIS SFC BOUNDARY IS BEGINNING TO BECOME LESS DISTRICT THAN IT
WAS OVER THE PAST SEVERAL DAYS. IN THE EASTERN ATLC...AN
ELONGATED UPPER TROUGH AXIS EXTENDS FROM BETWEEN THE CANARY AND
AZORES ISLANDS ALONG 27N26W 20N25W 19N45W. AN UPPER LOW HAS
BECOME CUT OFF FROM THIS TROUGH AND IS MOVING SLOWLY W CENTERED
NEAR 18N60W. AT THE SURFACE...A BROAD RIDGE DOMINATES THE ATLC
EAST OF 65W WITH A STATIONARY 1022 MB HIGH LOCATED NEAR 31N49W.
ORGANIZED SHOWERS AND TSTMS IN THE CNTRL AND ERN ATLC ARE
CONFINED TO THE ITCZ AND TROPICAL WAVES.

$$
CANGIALOSI


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