[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 042348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON 04 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...
NONE.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 52W SOUTH OF 18N MOVING WEST 10 KT.  THE
WAVE IS ACCOMPANIED BY A LOW LEVEL CIRCULATION NEAR 13.5N WHICH
HAS BEEN THE BASIS FOR THE WAVE LOCATION FOR THE LAST FEW MAPS.
THE CIRCULATION HAS SHOWN VERY LITTLE WESTWARD MOTION DURING THE
LAST 24 HOURS WHICH IS ATYPICAL FOR A WAVE IN THIS PORTION OF
THE ATLC BASIN.  NONETHELESS...SATELLITE IMAGERY DOES INDICATE
THAT THE SYSTEM IS A LITTLE BETTER DEFINED WITH SCATTERED
MODERATE/ISOLATED STRONG CONVECTION NOW LOCATED FROM 12N-16.5N
BETWEEN 47W-53W.  UPPER LEVEL WINDS DO NOT APPEAR FAVORABLE FOR
SIGNIFICANT DEVELOPMENT AS THE SYSTEM IS CURRENTLY EXPERIENCING
WLY SHEAR.

TROPICAL WAVE OVER THE W CARIBBEAN ALONG 78W/79W SOUTH OF 20N
MOVING WEST 15 TO 20 KT. THIS WAVE CONTINUES TO EXPERIENCE
STRONG UPPER LEVEL NW FLOW AND MODERATE SUBSIDENCE ON THE
BACK/WEST SIDE OF A TROUGH OVER THE E CARIBBEAN.  CONVECTION W
OF THE WAVE AXIS OVER CENTRAL AMERICA APPEARS TO BE MORE
DIRECTLY RELATED TO DIVERGENT FLOW ALOFT ASSOCIATED WITH A RIDGE
OVER THE SW CARIBBEAN AND CENTRAL AMERICA.

TROPICAL WAVE OVER THE BAY OF CAMPECHE AND S MEXICO ALONG 97W
SOUTH OF 22N MOVING WEST NEAR 15 KT. THE WAVE IS PRODUCING AN
AREA OF SCATTERED MODERATE CONVECTION FROM 18N-25N BETWEEN
92W-97W INCLUDING COASTAL REGIONS OF MEXICO FROM VERACRUZ TO
TAMPICO.

...ITCZ...
ITCZ AXIS ALONG 9N10W 9N25W 6N40W 9N53W 7N65W 10N80W.  SCATTERED
MODERATE CONVECTION FROM 6N-10N BETWEEN 33W-45W.  SIMILAR
ACTIVITY OVER N PORTIONS OF S AMERICA FROM 4N-9N BETWEEN
62W-71W.

...DISCUSSION...
THE GULF OF MEXICO...
MIDDLE TO UPPER LEVEL RIDGE PREVAILS OVER THE GLFMEX WITH MEAN
AXIS EXTENDING E/W ALONG 25N. UPPER LEVEL ANTICYCLONE IS
POSITIONED OVER THE BAY OF CAMPECHE WITH ASSOCIATED DIVERGENT
FLOW ENHANCING CONVECTION ALONG A TROPICAL WAVE NEAR 97W.
ELSEWHERE...MODERATE SUBSIDENCE DOMINATES ESPECIALLY OVER THE SE
GLFMEX AND S FLORIDA. LOOKING UPSTREAM...AN UPPER LEVEL
SHORTWAVE IMPULSE EMBEDDED WITHIN THE WLY FLOW IS IGNITING
CONVECTION OVER TEXAS/LOUISIANA. THIS ACTIVITY HAS BEEN
PROPAGATING RAPIDLY SEWD AND MAY APPROACH THE N GULF COAST LATER
TONIGHT.  OTHERWISE...THE UPSTREAM PATTERN WILL BECOME
INCREASINGLY AMPLIFIED DURING THE NEXT 36-72 HOURS AS A LARGE
TROUGH DEVELOPS OVER MEXICO.  THIS PATTERN WOULD LIKELY PRODUCE
A DIVERGENT UPPER LEVEL PATTERN AND FAVOR INCREASING CLOUDINESS
AND SHOWERS/THUNDERSTORMS W OF 90W.

THE CARIBBEAN SEA...
A SHARP MIDDLE TO UPPER LEVEL RIDGE REMAINS OVER THE W
CARIBBEAN EXTENDING FROM COLOMBIA NW ALONG THE COAST OF CENTRAL
AMERICA AND ACROSS THE YUCATAN PENINSULA. DIVERGENT UPPER LEVEL
FLOW ON THE EQUATORWARD SIDE OF THE RIDGE IS PRODUCING NUMEROUS
SHOWERS/STRONG THUNDERSTORMS OVER E PORTIONS OF
NICARAGUA/HONDURAS FROM 11.5N-16.5N BETWEEN 82W-86W.  LOCALLY
HEAVY RAINFALL IS LIKELY WITHIN THIS AREA OF CONVECTION. WIDELY
SCATTERED ACTIVITY IS ALSO NOTED OVER BELIZE/N GUATEMALA AND
COSTA RICA/PANAMA. THE UPPER RIDGE IS EXPECTED TO REMAIN
ESSENTIALLY STATIONARY OVER THE NEXT 24 HOURS. THIS COUPLED WITH
INCREASING LOW LEVEL MOISTURE ASSOCIATED WITH A TROPICAL WAVE
NEARING 80W WILL KEEP A RATHER UNSETTLED PATTERN FOR A GOOD
PORTION OF CENTRAL AMERICA DURING THE NEXT DAY OR SO.  ELSEWHERE
OVER THE CARIBBEAN...MIDDLE TO UPPER LEVEL TROUGH EXTENDS SWD
FROM THE CENTRAL ATLC OVER PUERTO RICO TO THE N COAST OF
VENEZUELA NEAR 70W.  MODERATE SUBSIDENCE AND DRY AIR WITH THE
TROUGH COVERS ALL OF THE GREATER ANTILLES AND THE CENTRAL
CARIBBEAN SUPPRESSING DEEP CONVECTIVE ACTIVITY. DIVERGENT FLOW
AHEAD OF THE TROUGH IS PRODUCING ENHANCED CONVECTION OVER N
PORTIONS OF S AMERICA AND THE LESSER ANTILLES. THE UPPER TROUGH
IS EXPECTED TO BE MAINTAINED BY A SHORTWAVE DISTURBANCE
CURRENTLY DROPPING SEWD OVER THE N BAHAMAS AND FLORIDA STRAITS.

THE SUBTROPICAL ATLANTIC OCEAN...
A MIDDLE TO UPPER LEVEL TROUGH HAS MOVED OFF THE E COAST OF THE
UNITED STATES N OF 30N WITH ATTENDANT SURFACE COLD FRONT
TRAILING SWD OVER BERMUDA TO THE CENTRAL COAST OF FLORIDA NEAR
28N. NEARLY ALL OF THE UPPER LEVEL SUPPORT IS CONFINED WELL N OF
THE AREA AND ON ISOLATED SHOWERS/THUNDERSTORMS ACCOMPANY THE
COLD FRONT.  ELSEWHERE W OF 60W...STRONG SUBSIDENCE DOMINATES.
OVER THE CENTRAL ATLC...A MIDDLE TO UPPER LEVEL TROUGH EXTENDS
FROM 32N55W TO A LARGE UPPER LOW JUST N OF PUERTO RICO. THIS
FEATURE CONTINUES TO PRODUCING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS OVER THE CENTRAL ATLC WITHIN 150 NM EITHER SIDE OF
A LINE STRETCHING FROM 20N56W TO 30N51W. BUILDING MID-UPPER
LEVEL RIDGE LIES FURTHER BETWEEN 40W-60W WITH A TROUGH OVER THE
FAR E ATLC EXTENDING SWD FROM AN UPPER LOW OVER THE CANARY
ISLANDS TO 20N40W. MODERATE SUBSIDENCE COVERS THE AREA POLEWARD
OF THE TROUGH AXIS WHILE A 40-60 UPPER JET TO THE SOUTH OF THE
TROUGH PRODUCES SOME HIGH CLOUDINESS.

THE TROPICAL ATLANTIC OCEAN...
MID/UPPER LEVEL RIDGE LIES OVER MOST OF THE TROPICAL ATLC BUT
REMAINS DISPLACED S OF ITS TYPICAL POSITION ALONG 11N/12N. AS A
RESULT...STRONG UPPER LEVEL WLY FLOW COVERS THE AREA E OF 45W N
OF THE RIDGE INTO W AFRICA.  THIS IS PRODUCING A GENERALLY
UNFAVORABLE ENVIRONMENT FOR TROPICAL CYCLONE DEVELOPMENT. WEST
OF 45W...A WEAK UPPER LOW NEAR 11N49W DISRUPTS THE RIDGE WITH
MODERATE SUBSIDENCE ON ITS BACK/WEST SIDE PENETRATING WELL INTO
THE TROPICAL ATLC.

$$
RHOME



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