[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 010558
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI 01 OCT 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0315 UTC.

...SPECIAL FEATURES...
TROPICAL STORM LISA IS CENTERED NEAR 34.6N 47.7W AT 01/0300 UTC
MOVING N 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. DEEP CONVECTION HAS
REDEVELOPED WRAPPING AROUND TO THE SW OF THE LOW LEVEL
CIRCULATION. LISA HAS BEEN CUT OFF FROM A MID/UPPER LEVEL LOW
AND IS BEGINNING TO MOVE N AROUND AN UPPER LEVEL HIGH TO THE
EAST. THERE IS LITTLE SHEAR SO EVEN OVER COOLER SST LISA MAY
STILL INTENSIFY TO MINIMAL HURRICANE STRENGTH. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 75 NM IN THE SW
QUADRANT. SCATTERED SHOWERS ARE WITHIN 120 NM IN THE E
SEMICIRCLE.

...TROPICAL WAVES...
E ATLC TROPICAL WAVE IS ALONG 28W S OF 17N MOVING W 10-15 KT.
BROAD MID LEVEL INVERTED V SIGNATURE CURVATURE IS OBSERVED ON
INFRARED SATELLITE IMAGERY PASSING THE CAPE VERDE ISLANDS. THE
ITCZ AXIS IS DISTORTED BY THIS WAVE. THIS WAVE IS ALONG THE W
EDGE OF AN UPPER RIDGE. SCATTERED MODERATE/STRONG CONVECTION IS
WITHIN 60/75 NM OF LINE FROM 12N23W-13N27W-13N30W.

MID ATLC TROPICAL WAVE IS ALONG 42W/43W S OF 17N MOVING W 10-15
KT. WEAK BUT DISTINCT LOW LEVEL CIRCULATION ALONG 11N IS THE
BASIS FOR THE WAVE AXIS. WITH NO VERTICAL SHEAR AND STRONG
SUBSIDENCE SURROUNDING THIS CIRCULATION FURTHER DEVELOPMENT IS
UNLIKELY. SCATTERED MODERATE CONVECTION WITHIN A 45/60 NM RADIUS
OF 12N42W.

TROPICAL WAVE APPROACHING THE LESSER ANTILLES ALONG 53W/54W S OF
17N MOVING W 10-15 KT. WEAK LOW LEVEL INVERTED V SIGNATURE
CURVATURE IS OBSERVED ON INFRARED SATELLITE IMAGERY. AS THE WAVE
MOVES INTO THE THE E CARIBBEAN...AN UPPER RIDGE THERE WILL
PREVENT THIS WAVE FROM DEVELOPING FOR THE NEXT COUPLE OF DAYS.
IT WILL BRING SCATTERED SHOWERS AND POSSIBLE THUNDERSTORMS TO
THE LESSER ANTILLES LATE TODAY INTO SATURDAY. ISOLATED SHOWERS
ARE FROM 15N-20N BETWEEN 51W-58W.

...ITCZ...
ITCZ IS CENTERED ALONG 10N13W 7N20W 9N37W 10N62W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS MOVING OFF THE SW COAST
OF AFRICA TO WITHIN 120 NM ALONG THE COAST OF LIBERIA AND SIERRA
LEONE. SCATTERED CLUSTERS OF SIMILAR CONVECTION DOT THE AREA
FROM 1N-15N BETWEEN 16W-43W.

...DISCUSSION...
GULF OF MEXICO AND W ATLANTIC...
BROAD LONGWAVE DEEP LAYERED TROUGH CONTINUES TO COVER THE E HALF
OF THE UNITED STATES MOVING INTO THE NW ATLC OVER THE CANADIAN
MARITIMES. THIS IS PRODUCING A COLD FRONT OVER THE W ATLC N OF
THE REGION DRAPING BACK ACROSS TO SE U.S. AS A STATIONARY FRONT.
A SURFACE TROUGH EXTENDS FROM THE FRONT ACROSS THE FLORIDA
PANHANDLE NEAR 31N84W TO 29N92W IN THE N GULF. A SECOND PART OF
THE SURFACE TROUGH EXTENDS FROM THE CENTRAL GULF NEAR 26N91W
INTO THE W BAY OF CAMPECHE NEAR 20N95W. STRONG SUBSIDENCE AND
DRY AIR AT ALL LEVELS COVERS MOST OF THE SE U.S. AND THE NW GULF
N OF A LINE FROM MEXICO NEAR 23N98W TO FLORIDA NEAR 31N84W. THIS
IS PREVENTING ANY SHOWER ACTIVITY. MID/UPPER LEVEL HIGH IS OVER
THE BAY OF CAMPECHE IN THE S GULF NEAR 19N95W WITH A LONG RIDGE
AXIS EXTENDING NE ACROSS FLORIDA NEAR 26N81W TO BEYOND BERMUDA.
ANTICYCLONIC FLOW COVERS THE REMAINDER OF THE GULF AND THE W
ATLC N OF 24N W OF 62W. MODERATE TO STRONG SUBSIDENCE AND
RELATIVE DRY AIR HAS LIMITED THE SHOWERS TO ONLY OVER SW
FLORIDA THAT ARE SEA BREEZE INDUCED. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE MOVING OFF THE W COAST OF THE YUCATAN
PENINSULA BEING INDUCED BY THE DOWN SLOPE OF THE UPPER LEVEL
HIGH.

CARIBBEAN SEA...
LARGE MID/UPPER LOW IS CENTERED NEAR 17N77W WITH CYCLONIC FLOW
COVERING THE AREA FROM 9N-23N BETWEEN 72W-83W. A SURFACE
REFLECTION IS A SURFACE TROUGH EXTENDING FROM N HAITI NEAR
20N72W S TO OFF THE COAST OF COLOMBIA NEAR 20N76W. A MID LEVEL
LOW IS ALONG THE COAST OF COLOMBIA NEAR 11N73W WITH A 1007 MB
LOW CENTERED NEAR 9N74W. THIS IS PRODUCING SCATTERED MODERATE/
STRONG CONVECTION OFF THE COAST WITHIN 90 NM OF 12N FROM
69W-75W. SCATTERED SHOWERS DOT THE W CARIBBEAN W OF 70W MOVING S
TO SE AROUND THE UPPER LEVEL CIRCULATION. OVER THE E CARIBBEAN
AN INDUCED MID/UPPER LEVEL RIDGE EXTENDS FROM THE COAST OF
VENEZUELA NEAR 11N64W NNW THROUGH THE MONA PASSAGE TO 23N70W.
SCATTERED SHOWERS DOT THE AREA FROM 14N-20N BETWEEN THE LEEWARD
ISLANDS AND 70W. THE ENVIRONMENT IS FAVORABLE IN THE CARIBBEAN
AND IS BEING MONITORED CLOSELY AS THE AREA HAS THE POTENTIAL FOR
FURTHER DEVELOPMENT.

CENTRAL/EASTERN ATLANTIC...
BROAD MID/UPPER LEVEL LOW IS IN THE CENTRAL ATLC NEAR 23N54W
WITH CYCLONIC FLOW FROM 17N-32N BETWEEN 46W-62W. T.S. LISA  HAS
BEEN CUT OFF FROM THIS FEATURE. A SURFACE REFLECTION IN THE FORM
OF A SURFACE TROUGH EXTENDS FROM 30N50W TO 20N56W. TO THE W A
WEAK SURFACE TROUGH EXTENDS FROM 30N63W TO 22N67W. SCATTERED
SHOWERS/THUNDERSTORMS HAVE DEVELOPED ALONG THE W SIDE OF THE
UPPER LOW FROM 21N-28N BETWEEN 57W-63W. THIS UPPER LEVEL FEATURE
IS BEGINNING TO INTERACT WITH THE TROPICAL WAVE APPROACHING THE
LESSER ANTILLES. BROAD WEAK MID/UPPER LOW IS IN THE E ATLC NEAR
20N36W WITH CYCLONIC FLOW FROM 15N-26N BETWEEN 30W-42W. THIS LOW
IS ADVECTING TROPICAL MOISTURE INTO THE MID-LATITUDES. MID/UPPER
INDUCED HIGH IS CENTERED BETWEEN THE LOWS 30N42W WHICH IS
DRAWING A TROUGH OVER THE NE ATLC DOWN INTO THE REGION. THIS
MID/UPPER LEVEL TROUGH IN THE NE ATLC EXTENDS FROM AN UPPER LOW
NEAR 33N24W SW TO 28N33W. THIS IS BRINGING STRONG SUBSIDENCE/DRY
AIR TO JUST W OF THE CANARY ISLANDS.

TROPICAL ATLANTIC...
TO THE S OF THE NE ATLC TROUGH IS A MID/UPPER LEVEL HIGH
CENTERED NEAR 11N26W WITH A RIDGE EXTENDING NE TO 24N22W.
ANTICYCLONIC FLOW S OF 24N E OF 30W. THE TROPICAL MOISTURE
ADVECTED N IS BEING SPREAD E ACROSS THE CAPE VERDE ISLANDS. THE
NORMAL WESTERLYS ARE BEING DROWN N INTO THE UPPER LOW NEAR
20N36W. WEAK MID/UPPER LEVEL HIGH IS CENTERED NEAR 11N49W WITH A
RIDGE AXIS EXTENDING N TO 16N46W. MID/UPPER LEVEL MOISTURE IS
ALSO LIMITED WITH GENERALLY DRY CONDITIONS S OF 10N W OF 50W.

$$
WALLACE


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