[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 100521
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN 10 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
0345 UTC.

...SPECIAL FEATURES...

TROPICAL STORM MATTHEW IS CENTERED OVER THE N CENTRAL GULF OF
MEXICO NEAR 27.7N 91.3W...OR ABOUT 165 MILES SOUTHWEST OF THE
MOUTH OF THE MISSISSIPPI RIVER...AT 10/0300 UTC. MATTHEW IS
MOVING NNE AT 8 KT. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH
GUSTS TO 45 KT AND THE MINIMUM CENTRAL PRESSURE IS 998 MB. SEE
LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SATELLITE IMAGERY
INDICATES THAT MATTHEW IS UNDERGOING A REMARKABLY SIMILAR
EVOLUTION AS THAT WITNESSED LAST NIGHT. STRONG SW SHEAR
ASSOCIATED WITH A MID-LATITUDE TROUGH OVER THE CENTRAL UNITED
STATES AND N MEXICO HAS ONCE AGAIN STRIPPED AWAY THE DEEP
CONVECTION AND THE LOW LEVEL CIRCULATION IS COMPLETELY EXPOSED.
THE CDO FEATURE HAS WEAKENED SIGNIFICANTLY AND ASSOCIATED
CONVECTION IS NOW ALIGNED IN MORE OF A LINEAR PATTERN FROM THE
FLORIDA PANHANDLE TO THE N TIP OF THE YUCATAN PENINSULA.  GIVEN
THIS TREND...IT WILL BE DIFFICULT FOR MATTHEW TO STRENGTHEN
SIGNIFICANTLY AND THE PRIMARY THREAT WILL BE LOCALLY HEAVY
RAINFALL AND POSSIBLE FLOODING ALONG THE N GULF COAST FROM SE
LOUISIANA EWD TO THE FLORIDA PANHANDLE.  THIS AREA HAS ALREADY
RECEIVED HEAVY RAINS AHEAD OF MATTHEW AS TROPICAL MOISTURE
SURGES NWD INTO THE SE UNITED STATES.

A 1000 MB LOW IS LOCATED APPROXIMATELY 100 NM SSW OF BERMUDA
NEAR 30.5N66W MOVING N NEAR 10 KT. SATELLITE IMAGERY INDICATES
THAT THIS SYSTEM IS BECOMING BETTER ORGANIZED AND MORE TROPICAL
IN NATURE. THE UPPER LOW WHICH WAS PREVIOUSLY LIMITING TROPICAL
DEVELOPMENT HAS MOVED SEWD AND IS NOW PRODUCING A MORE FAVORABLE
UPPER LEVEL PATTERN. THIS LOW IS ALREADY PRODUCING WINDS TO
TROPICAL STORM FORCE PRIMARILY WITHIN SCATTERED MODERATE
CONVECTION 150 NM OVER THE NW SEMICIRCLE. THUS...IF CONVECTIVE
DEVELOPMENT CONTINUES OVERNIGHT...TROPICAL STORM ADVISORIES MAY
BE INITIATED SOMETIME TODAY.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE E ATLC ALONG 31W S OF 19N MOVING W NEAR
10 KT.  THE WAVE IS CURRENTLY INTERACTING WITH A HIGH AMPLITUDE
MID-UPPER LEVEL TROUGH LOCATED OVER THE E ATLC. ASSOCIATED SHEAR
CONTINUES TO DISPLACE CONVECTION TO THE EAST OF THE WAVE AXIS
WITH SCATTERED MODERATE ACTIVITY FROM 13N-16N BETWEEN 27W-30W.

TROPICAL WAVE LOCATED 300-400 NM E OF BARBADOS ALONG 54W S OF
18N MOVING W 15-20 KT. THE WAVE IS CURRENTLY WITHIN A DIVERGENT
UPPER LEVEL ENVIRONMENT AND CONVECTION HAS INCREASED DURING THE
LAST FEW HOURS. CURRENTLY...NUMEROUS STRONG ACTIVITY EXISTS FROM
13N-19N BETWEEN 50W-56W.  LATEST SATELLITE IMAGERY INDICATES
THAT THIS ACTIVITY IS BEING DRAWN NWD WITHIN A WEAKNESS IN THE
SUBTROPICAL RIDGE CREATED BY THE AFOREMENTIONED LOW NEAR BERMUDA
AND TRAILING TROUGH. ADDITIONALLY...A STRONG UPPER LEVEL TROUGH
OVER THE E CARIBBEAN IS PRODUCING SW SHEAR LIMITING DEVELOPMENT
AND KEEPING MOST OF THE CONVECTION EAST OF THE LESSER ANTILLES.

...ITCZ...

ITCZ AXIS OFF THE COAST OF AFRICA NEAR GUINEA EXTENDING SW ALONG
6N20W 9N30W 6N40W 9N55W 7N70W 11N80W.  WIDELY SCATTERED MODERATE
CONVECTION FROM 3N-10N BETWEEN 10W-23W.

...DISCUSSION...

GULF OF MEXICO...
IN THE MIDDLE TO UPPER LEVELS...AN AMPLIFIED RIDGE COVERS MOST
OF THE GLFMEX WITH AXIS EXTENDING FROM THE BAY OF CAMPECHE NEWD
OVER THE FLORIDA PANHANDLE INTO THE SE UNITED STATES. THE RIDGE
IS SLOWLY SLIDING EWD AHEAD OF A STRONG MID-LATITUDE TROUGH
PROGRESSING THROUGH THE CENTRAL UNITED STATES AND N MEXICO.  THE
TROUGH CONTINUES TO TRIGGER SHOWERS/TSTMS OVER S MEXICO
PRIMARILY BETWEEN GUATEMALA AND 100W.  THE UPPER TROUGH IS ALSO
PRODUCING STRONG SW SHEAR OVER T.S. MATTHEW LIMITING DEVELOPMENT
AS THE SYSTEM MOVES NORTHWARD TOWARD LOUISIANA.  COPIOUS
TROPICAL MOISTURE SURGING AHEAD OF MATTHEW COUPLED WITH
MID-LATITUDE DYNAMICS AHEAD OF THE UPPER TROUGH CONTINUES TO
PRODUCE CLOUDINESS AND SHOWERS/THUNDERSTORMS OVER THE NE GLFMEX
AND ALONG THE N GULF COAST FROM EXTREME SE LOUISIANA EWD TO THE
FLORIDA PANHANDLE. THE STRONGEST OF THIS ACTIVITY CURRENTLY LIES
WITHIN 100 NM EITHER SIDE OF A LINE FROM THE FLORIDA/ALABAMA
BORDER SWD TO THE N TIP OF THE YUCATAN PENINSULA.  LOCALLY HEAVY
RAINFALL AND POSSIBLE FLOODING IS EXPECTED TO CONTINUE TODAY AS
MATTHEW APPROACHES THE LOUISIANA COAST. ONCE INLAND...MATTHEW IS
EXPECTED TO MERGE WITH THE APPROACHING MID-LATITUDE TROUGH AND
SWEEP A COLD FRONT CURRENTLY FORMING OVER THE W GLFMEX EWD.
SCATTERED SHOWERS/THUNDERSTORMS ARE LIKELY ALONG AND AHEAD OF
THE COLD FRONT WHICH WILL MOVE INTO THE E GLFMEX BY MON
AFTERNOON.

CARIBBEAN
LARGE MID/UPPER LEVEL TROUGH OVER THE W ATLC EXTENDS SWD INTO
THE E CARIBBEAN OVER HISPANIOLA. A MID-UPPER LEVEL RIDGE LIES W
OF THE TROUGH EXTENDING EWD FROM S MEXICO TO 16N73W. THIS
PATTERN IS PRODUCING DRY N/NW FLOW OVER MOST OF THE CARIBBEAN W
OF 70W. THE ONLY WEATHER OF NOTE W OF THE UPPER TROUGH AXIS IS
AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS OVER HISPANIOLA AND
JAMAICA ALONG A WEAK LOW LEVEL CONVERGENCE LINE EXTENDING SWD
FROM A LOW CENTER OVER THE ATLC. EAST OF THE UPPER
TROUGH...MOIST SW FLOW AND UPPER LEVEL DIVERGENT FLOW CONTINUES
TO PRODUCE CLOUDINESS AND SHOWERS/THUNDERSTORMS OVER THE EXTREME
SE CARIBBEAN AND LESSER ANTILLES.  NUMERICAL GUIDANCE INDICATES
THE UPPER TROUGH WILL REMAIN NEARLY STATIONARY DURING THE NEXT
24-36 HOURS KEEPING THE OVERALL UNSETTLED/WET PATTERN OVER THE
SE CARIBBEAN AND LESSER ANTILLES.

SUBTROPICAL ATLANTIC...
A HIGH AMPLITUDE TROUGH-RIDGE-TROUGH PATTERN EXISTS OVER THE
SUBTROPICAL ATLC WITH A LARGE MID/UPPER LEVEL LOW CENTERED ABOUT
350 NM SW OF BERMUDA...RIDGE OVER THE CENTRAL ATLC BETWEEN
30W-60W...AND TROUGH OVER THE E ATLC FROM THE CANARY ISLANDS SWD
INTO THE TROPICAL ATLC NEAR 10N40W.  THE W ATLC UPPER LOW
REMAINS THE PRIMARY WEATHER MAKER WITH BROAD DIVERGENT FLOW TO
THE EAST PRODUCING A LARGE AREA OF CLOUDINESS AND
SHOWERS/THUNDERSTORMS OVER THE CENTRAL ATLC BETWEEN 50W-60W.
THE STRONGEST/MOST NUMEROUS OF THIS ACTIVITY IS LOCATED FROM
23N-29N BETWEEN 50W-55W.  THIS UPPER LOW IS ALSO PROVIDING A
FAVORABLE ENVIRONMENT FOR THE DEVELOPMENT OF A 1000 MB LOW JUST
S OF BERMUDA DISCUSSED IN THE SPECIAL FEATURE SECTION. SCATTERED
MODERATE CONVECTION ACCOMPANIES THE LOW WITHIN 150 NM NW
SEMICIRCLE.  ELSEWHERE...STRONG SUBSIDENCE ON THE BACK/WEST SIDE
OF THE UPPER LOW COVERS THE REMAINDER OF THE W ATLC CREATING
DRY/TRANQUIL CONDITIONS.  MID-UPPER LEVEL MOISTURE ASSOCIATED
WITH AFOREMENTIONED CONVECTIVE ACTIVITY RIDES UP AND OVER THE
CENTRAL ATLC RIDGE LEAVING MUCH OF THE E ATLC UNDER DRY NW FLOW.
ADDITIONALLY...MODERATE SUBSIDENCE ACCOMPANIES THE E ATLC
TROUGH. AT THE SURFACE...THE SUBTROPICAL RIDGE REMAINS LARGELY
DISRUPTED BY THE DEVELOPING LOW SE OF BERMUDA AND TROUGH
TRAILING SWD OVER HISPANIOLA.

TROPICAL ATLANTIC...
A LARGE UPPER LEVEL HIGH E OF THE LESSER ANTILLES NEAR 17N51W
COVERS THE W HALF OF THE TROPICAL ATLC WHILE A MID-UPPER LEVEL
TROUGH OVER THE E SUBTROPICAL ATLC PENETRATES THE TROPICS FROM
20N20W TO 10N40W.  THE UPPER TROUGH IS PRODUCING STRONG SW SHEAR
E OF 30W WITH MODERATE SUBSIDENCE TO THE WEST REACHING THE ITCZ
BETWEEN 30W-45W.

$$
RHOME


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