[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 081154
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT SEP 08 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURE...
SUBTROPICAL STORM GABRIELLE WAS CENTERED NEAR 31.2N 73.8W OR
ABOUT 245 NM SOUTH-SOUTHEAST OF CAPE LOOKOUT NORTH CAROLINA AT
08/1200 UTC. GABRIELLE IS MOVING W-NW AT 10 KT...AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE DURING THE NEXT 24 HOURS
WITH A GRADUAL DECREASE IN FORWARD SPEED. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1011 MB. MAXIMUM SUSTAINED WINDS ARE 40 KT
WITH GUSTS TO 50 KT. SLIGHT STRENGTHENING IS EXPECTED AS
GABRIELLE ACQUIRES TROPICAL CHARACTERISTICS. SEE LATEST NHC
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST ADVISORY UNDER
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS INCLUDING THE LATEST
WATCH AND WARNING INFORMATION. GABRIELLE LOOKS A LITTLE BETTER
ON SATELLITE THIS MORNING AND APPEARS TO BE TAKING ON MORE
TROPICAL LIKE CHARACTERISTICS...WITH A CURVED BAND NOW OVER THE
N AND W QUADRANTS. THIS BAND OF SCATTERED MODERATE CONVECTION IS
FROM 31N-34N BETWEEN 70W-75W.

...TROPICAL WAVES...

AN EAST ATLANTIC TROPICAL WAVE IS ALONG 26W S OF 20N MOVING WEST
NEAR 15 KT. THIS WAVE CONTINUES TO EXHIBIT A BROAD ENVELOPE OF
CYCLONIC TURNING. THE FIRST FEW METSAT-9 VISIBLE IMAGES REVEAL A
MID LEVEL CIRCULATION ALONG THE WAVE AXIS NEAR 11N. A RECENT
QUIKSCAT PASS REVEALED AN ELONGATED TROUGH AXIS STRETCHING ENE
ALONG 7N38W 9N26W 13N20W. THIS WAVE IS PRODUCING A LARGE AREA OF
CLOUDINESS AND THUNDERSTORMS...WITH THE STRONGEST ACTIVITY NOTED
FROM 10N-13N BETWEEN 28W-33W...AND ALSO FROM 12N-15N BETWEEN
22W-26W. THIS SYSTEM HAS THE POTENTIAL FOR SOME DEVELOPMENT
DURING THE NEXT FEW DAYS.

AN ATLANTIC OCEAN TROPICAL WAVE IS GENERALLY ALONG 51W/52W SOUTH
OF 22N MOVING WEST NEAR 15 KT. THIS WAVE WAS ADJUSTED SLIGHTLY
TO THE E BASED ON ITS APPEARANCE IN SATELLITE IMAGERY SHOWING A
BROAD AREA OF LOW LEVEL CYCLONIC TURNING...AND ALSO AN EARLIER
ASCAT PASS. IN ADDITION...WINDS AT BUOY 41040 HAVE REMAINED FROM
THE NE OVER THE LAST SEVERAL HOURS SUGGESTING THE WAVE HAS YET
TO PASS. SHOWER ACTIVITY HAS INCREASED SLIGHTLY WITH THE
WAVE...WITH LIGHTNING DATA NOW DEPICTING SCATTERED TSTMS FROM
15N-17N BETWEEN 51W-56W. OVERALL THOUGH THE CONVECTION IS
MINIMAL AND DISORGANIZED. A SEPARATE 1013 MB LOW PRESSURE CENTER
IS E OF THE WAVE AXIS NEAR 12N46W...WHICH IS NEARLY STATIONARY
AND DISSIPATING.

TROPICAL WAVE IS ALONG 85W/86W SOUTH OF 19N THROUGH CENTRAL
AMERICA MOVING WEST 15 KT. THIS WAVE REMAINS DIFFICULT TO LOCATE
IN SATELLITE IMAGERY AND THE SURROUNDING SFC OBSERVATIONS...THUS
THE POSITION IS BASED MOSTLY ON EXTRAPOLATION. THE CONVECTION
OVER THE SW CARIBBEAN SEEMS MORE ASSOCIATED WITH THE ITCZ.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 15N17W 7N30W 8N50W 8N60W. A FAIRLY
LARGE CLUSTER OF MODERATE TO STRONG CONVECTION IS MOVING OFF THE
AFRICAN COAST FROM 14N-19N BETWEEN 15W-20W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90 NM EITHER SIDE
OF THE AXIS BETWEEN 27W-38W.

DISCUSSION...

THE GULF OF MEXICO...
THE MOST ACTIVE WEATHER IN THE GULF THIS MORNING IS THE
SCATTERED MODERATE CONVECTION IN THE SE PORTION FROM 23N-26N
BETWEEN 80W-86W. ISOLATED SHOWERS AND TSTMS ARE ALSO JUST TO THE
W OF THIS AREA OVER THE MIDDLE GULF...S OF 26N BETWEEN 86W-90W.
CLOUD TOPS OVER THIS CONVECTION ARE BEING STRETCHED TO THE S
INTO THE CARIBBEAN BY STRONG UPPER NLY FLOW BETWEEN THE UPPER
LOW JUST SW OF SUBTROPICAL STORM GABRIELLE...AND RIDGING
EXTENDING INTO THE GULF FROM AN UPPER HIGH OVER CENTRAL TEXAS.
THE TRIGGER FOR THESE SHOWERS/TSTMS SEEMS TO BE WEAK LOW TO MID
LEVEL TROUGHING. MOISTURE MAY HAVE ALSO BEEN INCREASED IN THE
VICINITY FROM THE TROPICAL WAVE MOVING THROUGH THE FAR W
CARIBBEAN. OTHERWISE...WEAK SFC RIDGING DOMINATES WHICH IS
PRODUCING MOSTLY LIGHT WINDS/LOW SEAS ACROSS THE BASIN. SIMILAR
CONDITIONS ARE GENERALLY EXPECTED TO PERSIST THROUGH THE END OF
THE WEEKEND. HOWEVER...SCATTERED TSTMS ASSOCIATED WITH WEAK SFC
TROUGHING IS GENERALLY EXPECTED TO PERSIST NEAR AND N OF THE
YUCATAN CHANNEL.

THE CARIBBEAN SEA...
THE CARIBBEAN IS OVERALL PRETTY QUIET THIS MORNING. THE MAIN
AREA OF CONVECTION IS THE SCATTERED MODERATE/ISOLATED STRONG IN
THE SW CARIBBEAN S OF 13N BETWEEN THE COASTS OF COLOMBIA AND
COSTA RICA/NICARAGUA. THIS SEEMS MOSTLY TIED TO THE ITCZ IN
ADDITION TO DIFFLUENT FLOW ALOFT. TRADES ARE LIGHT TO MODERATE
WITH ONLY WEAK RIDGING IN PLACE...WITH THE NORMAL PATTERN BEING
DISRUPTED IN PART BY GABRIELLE IN THE WRN ATLC. THE TRADES ARE
CARRYING TYPICAL PATCHES OF LOW LEVEL MOISTURE WITH EMBEDDED
SHOWERS WWD...WITH A SLIGHTLY MORE CONCENTRATED AREA OF SHOWERS
NOTED NEAR THE LEEWARD ISLANDS WHICH ARE IN VIEW OF THE SAN JUAN
RADAR. THIS ACTIVITY IS OCCURRING DOWNSTREAM FROM A WEAK
INVERTED UPPER TROUGH JUST E OF THE LEEWARD ISLANDS. THE
REMAINDER OF THE UPPER PATTERN IS DOMINATED BY RIDGING OVER THE
NW PORTION...WITH WLY UPPER FLOW OVER MUCH OF THE CENTRAL
CARIBBEAN BETWEEN THE UPPER LOW JUST E OF CENTRAL FLORIDA AND AN
UPPER HIGH OVER NRN SOUTH AMERICA. LIGHT TO MODERATE TRADES
EXPECTED TO PERSIST THROUGH THE END OF THE WEEKEND...STRONGEST
NEAR THE N COAST OF COLOMBIA.

THE ATLANTIC OCEAN...
THE WRN ATLC IS DOMINATED BY SUBTROPICAL STORM GABRIELLE. SEE
SPECIAL FEATURE SECTION ABOVE FOR MORE DETAILS. SFC TROUGHING
TRAILING S/SW OF GABRIELLE EXTENDS THROUGH THE SE BAHAMAS AND IS
SUPPORTING THE SCATTERED SHOWERS/ISOLATED TSTMS FROM 21N-27N
BETWEEN 70W-79W. THIS IS ALSO BEING SUPPORTED BY LIFT AHEAD OF
THE UPPER LOW NEAR 27N78W. THE TAIL END OF A FRONTAL SYSTEM IN
THE NORTH CENTRAL ATLC IS TRIGGERING ISOLATED TSTMS N OF 25N
BETWEEN 40W-63W. THE ASSOCIATED DEEP LAYER LOW REMAINS WELL
DEFINED NEAR 41N43W...AND HAS TROUGHING ENTERING THE AREA N OF
25N GENERALLY BETWEEN 45W-60W. WEAK RIDGING DOMINATES THE
REMAINDER OF THE SFC PATTERN ACROSS THE DISCUSSION AREA...WITH A
1021 MB CENTER ANALYZED NEAR 28N31W. WINDS ARE ON THE LIGHT TO
MODERATE SIDE OVER MUCH OF THE AREA E OF 65W...IN RESPONSE TO
THE WEAK RIDGING IN PLACE IN ADDITION TO THE FRONT ALONG 32N43W
26N55W 29N63W WHICH IS DISRUPTING THE TRADES. THE EXCEPTION IS
SLIGHTLY STRONGER NE FLOW OFF THE NW COAST OF AFRICA...PER THE
USUAL STRONGER GRADIENT IN PLACE.

$$
WILLIS




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