[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 271705
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1645 UTC.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED ABOUT 800 NM E OF THE BARBADOS ALONG
46W/47W S OF 17N MOVING W NEAR 15 KT. THE WAVE CONTINUES TO
DISPLAY A SHARP AND WELL-DEFINED LOW-LEVEL CIRCULATION IN
SATELLITE IMAGERY BUT DEEP CONVECTION IS LIMITED AND POORLY
ORGANIZED. SCATTERED MODERATE CONVECTION FROM 6N-14N BETWEEN
40W-47W.

TROPICAL WAVE OVER THE CENTRAL CARIBBEAN JUST W OF THE ABC
ISLANDS ALONG 70W S OF 16N MOVING W NEAR 15 KT. THE WAVE IS
CURRENTLY INTERACTING WITH A MIDDLE TO UPPER LEVEL TROUGH AND
ATTENDANT FRONTAL BOUNDARY TO THE NORTH OVER THE W ATLC. LOWER
LEVEL MOISTURE ASSOCIATED WITH THE WAVE IS BEING PULLED NWD
WITHIN THE LARGER SCALE TROUGH/FRONT.  THIS COMBINED WITH UPPER
LEVEL DYNAMICS/LIFT IS PRODUCING AN AREA OF SCATTERED TO LOCALLY
NUMEROUS STRONG CONVECTION FROM 14N-18N BETWEEN 62W-71W. THE
STRONGEST OF THIS ACTIVITY LIES JUST S OF PUERTO RICO...THE
VIRGIN ISLANDS...AND THE LEEWARD ISLANDS IN LINE WITH THE BEST
UPPER LEVEL DYNAMICS.  HOWEVER...CURRENT ACTIVITY IS MOVING
NWD AND SCATTERED SHOWERS/THUNDERSTORMS WITH LOCALLY HEAVY RAIN
COULD OVERSPREAD THESE AREAS LATER THIS EVENING AND TONIGHT.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N10W 6N30W 7N45W 7N60W 11N70W
8N80W. SCATTERED MODERATE CONVECTION WITHIN 180 NM S OF THE ITCZ
FROM 10W-25W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
WITHIN 250 N AND 150 S OF THE ITCZ FROM 25W-33W.

...DISCUSSION...

GULF OF MEXICO...
THE GLFMEX REMAINS UNDER THE INFLUENCE OF A LARGE MIDDLE TO
UPPER LEVEL ANTICYCLONE NEAR 24N91W WITH A HIGH AMPLITUDE RIDGE
EXTENDING NWD OVER THE E UNITED STATES ALONG THE MISSISSIPPI
VALLEY.  THIS PATTERN IS PRODUCING STRONG SUBSIDENCE AND FAIR
WEATHER OVER MOST OF THE GLFMEX. THE ONLY ACTIVITY OF NOTE IS A
SMALL AREA OF SHOWERS ALONG THE COAST OF MEXICO BETWEEN VERACRUZ
AND TAMPICO IN ASSOCIATION WITH MID/UPPER LOW E OF MEXICO CITY.
THE OVERALL PATTERN IS EXPECTED TO REMAIN ESSENTIALLY UNCHANGED
OVER THE NEXT 24 HOURS FOLLOWED BY A SLOW WEAKENING OF THE
RIDGE. A FEW SHOWERS MAY ACCOMPANY THE AFOREMENTIONED MIDDLE TO
UPPER LOW OVER MEXICO AS IT MOVES NWD AROUND THE W AND NW
PERIPHERY OF THE ANTICYCLONE.  AT THE SURFACE...RIDGING OVER THE
E UNITED STATES EXTENDS SWD OVER N FLORIDA AND THE N GLFMEX
PRODUCING PLEASANT NE BREEZES OVER FLORIDA AND RETURN FLOW OVER
THE W GLFMEX.

CARIBBEAN...
HIGH AMPLITUDE MIDDLE TO UPPER LEVEL TROUGH REMAINS THE PRIMARY
WEATHER MAKER WITH AXIS EXTENDING FROM THE W ATLC OVER
HISPANIOLA TO CENTRAL AMERICA NEAR PANAMA/COSTA RICA. DRY NLY
FLOW AND SUBSIDENCE BEHIND THIS TROUGH IS SUPPRESSING
SIGNIFICANT CLOUDS/CONVECTION PRODUCING GENERALLY TRANQUIL
WEATHER. E OF THE TROUGH...UPPER LEVEL DYNAMICS AND COPIOUS
TROPICAL MOISTURE IS PRODUCING UNSETTLED/STORMY WEATHER ACROSS
MOST OF THE E CARIBBEAN. SHOWERS/TSTMS ARE MOST NUMEROUS EAST OF
A TROPICAL WAVE ALONG 70W AND NEAR A REMNANT FRONTAL BOUNDARY
WHICH CLIPS THE NE CARIBBEAN NEAR PUERTO RICO/VIRGIN ISLANDS.
CURRENTLY...SCATTERED TO LOCALLY NUMEROUS STRONG CONVECTION IS
LOCATED FROM 14N-18N BETWEEN 62W-71W. THIS ACTIVITY IS MOVING
NWD AND MAY OVERSPREAD PORTIONS OF THE LEEWARD ISLANDS THIS
EVENING AND TONIGHT.  THE OVERALL PATTERN WILL REMAIN DRY/STABLE
OVER THE NW CARIBBEAN AND WET/UNSETTLED OVER THE E CARIBBEAN
DURING THE NEXT 2 DAYS.

SUBTROPICAL ATLANTIC...
A LONGWAVE RIDGE-TROUGH-RIDGE PATTERN PREVAILS IN THE MIDDLE TO
UPPER LEVELS WITH A RIDGE EMERGING FROM THE E UNITED STATES INTO
THE EXTREME W ATLC...TROUGH OVER THE W ATLC FROM 32N60W TO
HISPANIOLA...AND A BROAD/FLAT RIDGE OVER THE CENTRAL AND E ATLC
E OF 50W. CONFLUENT FLOW AND STRONG SUBSIDENCE ON THE UPSTREAM
SIDE OF THE ATLC TROUGH CONTINUES TO BLANKET MUCH OF THE W ATLC
PRODUCING DRY/STABLE CONDITIONS. OVER THE CENTRAL ATLC...THE
SHORTWAVE DISTURBANCE WHICH ROUNDED THE BASE OF THE LARGER SCALE
TROUGH LAST NIGHT IS EXITING THE AREA NEAR 50W WITH ONLY A SMALL
AREA OF SCATTERED SHOWERS/THUNDERSTORMS REMAINING FROM 27N-32N
BETWEEN 32W-45W. STREAKS OF BROKEN HIGH CLOUDS ACCOMPANY A 70-90
KT SUBTROPICAL JET FROM PUERTO RICO NEWD TO 32N50W. THE MAIN
DYNAMICS ASSOCIATED WITH THE JET ARE PRIMARILY CONFINED OVER THE
E CARIBBEAN BUT WILL BEGIN TO EXPAND INTO THE CENTRAL ATLC
DURING THE NEXT 36 HOURS AS THE TROUGH SHARPENS/AMPLIFIES AND
THE JET LIFTS NWD. THE SUBTROPICAL JET AND ASSOCIATED HIGH
CLOUDINESS CONTINUES EWD OVER THE E ATLC AROUND THE N PERIPHERY
OF AN E/W ORIENTED MIDDLE TO UPPER LEVEL RIDGE ALONG 28N/29W.  S
OF THE JET...AN UPPER LEVEL CYCLONIC SHEAR AXIS ALONG 24N/25N IS
PRODUCING CONFLUENT FLOW AND SUBSIDENCE EFFECTIVELY CAPPING
SIGNIFICANT CLOUDS/CONVECTION. AT THE SURFACE...REMNANT FRONTAL
TROUGH ASSOCIATED WITH LOW PRES N OF AREA EXTENDS INTO ATLC
ALONG 32N51W SWD TO PUERTO RICO.  STATIONARY 1019 MB HIGH IS
CENTERED OVER THE E ATLC NEAR 25N35W.

TROPICAL ATLANTIC...
WELL-DEFINED MIDDLE TO UPPER LEVEL LOW CONTINUES TO DRIFT SLOWLY
WESTWARD OVER THE CENTRAL ATLC ALONG 40W WITH DIVERGENT UPPER
LEVEL FLOW FAVORING ITCZ CONVECTION TO THE EAST WHILE CONFLUENT
UPPER LEVEL FLOW AND SUBSIDENCE RESTRICTS ITCZ CONVECTION TO THE
WEST.

$$
RHOME









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