[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301047
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU 30 SEP 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...
TROPICAL STORM LISA IS CENTERED NEAR 32.5N 47.0W AT 30/0900 UTC
MOVING NNW AT 10 KT. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH
GUSTS TO 75 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. LISA REMAINS ON THE NE
PORTION OF AN MID/UPPER LEVEL LOW THAT HAS PROVIDED
NORTHEASTERLY SHEAR. THIS HAS ALSO BLOWN THE CLOUDS/SCATTERED
SHOWERS FURTHER S AWAY FROM THE LOW LEVEL CENTER. ISOLATED
SHOWERS ARE WITHIN 120 NM OF THE CENTER IN THE SW QUADRANT.

...TROPICAL WAVES...
EASTERN MOST TROPICAL WAVE IS STILL ABOUT MIDWAY BETWEEN AFRICA
AND THE WINDWARD ISLANDS ALONG 39W/40W S OF 15N MOVING W 5-10
KT. WEAK MID LEVEL CIRCULATION REMAINS ON SATELLITE IMAGERY WITH
ASSOCIATED DEEP CONVECTION TO THE E OF THE WAVE AXIS. WESTERLY
SHEAR IS PREVENTING ANY FURTHER DEVELOPMENT. SCATTERED MODERATE
CONVECTION IS WITHIN 45/60 NM OF LINE FROM 11N39W-14N35W.

WESTERN MOST TROPICAL WAVE IS ABOUT 565 NM W OF BARBADOS ALONG
50W S OF 15N MOVING W 10-15 KT. WEAK LOW/MID LEVEL CURVATURE IS
OBSERVED ON SATELLITE IMAGERY. THIS WAVE IS ON THE SW SIDE OF
AN MID/UPPER LEVEL HIGH WHICH IS FUNNELING IN DRY AIR INTO THE
BACK SIDE OF THE WAVE AND SHOULD PREVENTING FURTHER DEVELOPMENT.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERS THE AREA
FROM 8N-13N BETWEEN 48W-54W.

TROPICAL WAVE THAT WAS IN THE S GULF OF MEXICO IS NO LONGER IN
THE ATLANTIC BASIN.

...ITCZ...
ITCZ IS CENTERED ALONG 15N10W 10N21W 9N62W. BROAD AREA WITH
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERS
THE AREA FROM 2N-16N BETWEEN 20W-37W.

...DISCUSSION...
GULF OF MEXICO AND W ATLANTIC...
BROAD DEEP LAYERED TROUGH COVERS THE THE EASTERN HALF OF THE
UNITED STATES EXTENDING S OVER TEXAS AND INTO THE NW GULF. THE
ASSOCIATED COLD FRONT EXTENDS INTO THE GULF TO JUST OVER THE
FLORIDA PANHANDLE BECOMING STATIONARY NEAR 30N86W TO 23N91W THEN
DISSIPATING INTO THE BAY OF CAMPECHE NEAR 18N94W. STRONG
SUBSIDENCE/DRY AIR AT ALL LEVELS  ARE PREVENTING ANY SHOWERS W
OF THE FRONTAL BOUNDARY. MID/UPPER LEVEL HIGH IS ALONG THE COAST
MEXICO NEAR 19N95W WITH A RIDGE AXIS EXTENDING NE ACROSS S
FLORIDA INTO THE W ATLANTIC TO BEYOND BERMUDA. ANTICYCLONIC FLOW
COVERS THE W ATLC WITHIN 250 NM OF THE AXIS AND THE GULF SW OF
THE FRONTAL TROUGH. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 75 NM OF LINE FROM 23N94W S INTO THE BAY OF
CAMPECHE OVER S MEXICO TO 18N96W. AT THE SURFACE...A WEAK
SURFACE TROUGH IN THE W ATLC EXTENDS FROM 22N68W TO 30N62W.
SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF LINE FROM
24N60W-28N61W.

CARIBBEAN SEA...
ANTICYCLONIC FLOW FROM THE MID/UPPER LEVEL HIGH IN THE SW GULF
CONTINUES OVER THE NW CARIBBEAN N OF 16N W OF 80W. THIS IS
BRINGING IN MODERATE SUBSIDENCE/DRY AIR OVER THE AREA THUS
LIMITING ISOLATED SHOWER ACTIVITY TO THE LOW LEVELS IN THIS
AREA. BROAD MID/UPPER LEVEL LOW IS CENTERED S OF HAITI NEAR
16N74W WITH CYCLONIC FLOW WITHIN 250/300 NM OF AN AXIS FROM THE
SW ATLC N OF THE DOMINICAN REPUBLIC NEAR 22N70W SW TO 12N80W.
THIS IS PRODUCING SCATTERED MODERATE/ISOLATED STRONG CONVECTION
N OF 14N TO JUST INLAND OVER HISPANIOLA FROM 68W-74W. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 15N FROM 60W-68W
INCLUDING THE LEEWARD/VIRGIN ISLANDS AND PUERTO RICO. THIS UPPER
LOW IS ALSO ADVECTING THE MOISTURE EASTWARD OVER COLOMBIA AND NW
VENEZUELA WHICH IS PRODUCING SCATTERED MODERATE/ISOLATED STRONG
CONVECTION S OF 12N FROM 70W-78W INCLUDING LAKE MARACAIBO. THE
DIFFLUENCE BETWEEN THE RIDGE TO THE NW AND THE LOW TO THE E IS
PRODUCING OVERCAST MULTILAYERED CLOUDS WITH CLUSTERS OF
SHOWERS/THUNDERSTORMS ACROSS THE W CARIBBEAN WITHIN 45 NM OF
LINE FROM 12N78W-15N84W-17N88W.

CENTRAL/EASTERN ATLANTIC...
MID/UPPER LEVEL LOW IN THE CENTRAL ATLC IS CENTERED SW OF T.S.
LISA NEAR 26N52W WITH A TROUGH AXIS EXTENDING FROM 36N45W S TO
19N58W. CYCLONIC FLOW IS WITHIN 300/350 NM OF THE AXIS. LISA IS
EMBEDDED WITHIN THE FLOW SURROUNDED BY STRONG SUBSIDENCE AND
WITH THE POSITION OF LISA...IS SEVERELY LIMITING CONVECTION
WITHIN THE STORM. AT THE SURFACE...A TROUGH HAS DEVELOPED FROM S
OF LISA ALONG 31N42W TO 19N56W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS WITHIN 60/75 NM OF LINE FROM 19N55W-23N48W
AND WITHIN 60 NM OF LINE FROM 28N43W-1N41W. SCATTERED SHOWERS
ARE WITHIN 60 NM OF LINE FROM 23N48W-28N43W. MID/UPPER LEVEL LOW
OVER THE SE ATLC IS CENTERED NEAR 20N35W WITH CYCLONIC FLOW S OF
27N FROM 25W-40W. AN INDUCED MID/UPPER LEVEL HIGH IS BETWEEN THE
LOWS NEAR 28N38W.

TROPICAL ATLANTIC...
MID/UPPER HIGH IS NEAR 14N47W WITH ANTICYCLONIC FLOW AND
MODERATE SUBSIDENCE S OF 20N FROM 40W-50W EXCEPT IN THE VICINITY
OF THE TROPICAL WAVE. THE MID/UPPER LOW FROM THE SE ATLC NEAR
20N35W HAS CYCLONIC FLOW N OF 13N FROM 25N-40W. THIS FEATURE IS
ENHANCING THE ACTIVITY WITHIN THE ITCZ. A MID/UPPER LEVEL HIGH
IS OFF THE SW COAST OF AFRICA NEAR 12N20W WITH ANTICYCLONIC FLOW
S OF 22N E OF 26W.

$$
WALLACE



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