[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU 21 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
1715 UTC.

...TROPICAL WAVES...
CENTRAL ATLANTIC TROPICAL WAVE ALONG 57W SOUTH OF 20N MOVING
WEST 15 KT. THE WAVE IS CURRENTLY ENCOUNTERING MODERATE WLY
SHEAR AND MIDDLE TO UPPER LEVEL SUBSIDENCE. THIS UNFAVORABLE
ENVIRONMENT IS DISPLACING SCATTERED MODERATE CONVECTION TO THE
EAST FROM 18N-22N BETWEEN 50W-57W AND LIMITING DEVELOPMENT.
HOWEVER...THE WAVE AND ASSOCIATED MOISTURE WILL ENCOUNTER A MORE
DIVERGENT UPPER LEVEL PATTERN AS IT MOVES INTO THE E CARIBBEAN
WHICH SHOULD ALLOW FOR MORE CONVECTION.

WESTERN CARIBBEAN SEA TROPICAL WAVE ALONG 79W SOUTH OF 20N
MOVING WEST 10 KT.  THE WAVE IS NEARING THE BASE OF A LARGE
MIDDLE TO UPPER LEVEL TROUGH STRETCHING ACROSS THE CENTRAL
CARIBBEAN.  RESULTING STRONG SW FLOW IS SHEARING ASSOCIATED
CONVECTION AND RESTRICTING DEVELOPMENT.  SCATTERED
MODERATE/ISOLATE STRONG CONVECTION OVER THE SW CARIBBEAN AND
PORTIONS OF COSTA RICA/PANAMA S OF 12N BETWEEN 74W-80W.

...ITCZ...
ITCZ AXIS IS ALONG 15N15W 5N30W 16N50W 10N60W 7N80W.  WIDELY
SCATTERED MODERATE CONVECTION FROM 2N-6N BETWEEN 15W-35W.
SCATTERED MODERATE CONVECTION FROM 10N-15N BETWEEN 35W-42W AND
FROM 15N-18N BETWEEN 45W-48W.  SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 9N-13N BETWEEN 59W-63W AND FROM 7N-10N
BETWEEN 65W-73W.

...DISCUSSION...

GULF OF MEXICO...
MIDDLE TO UPPER LEVEL SHORTWAVE TROUGH WHICH MOVED OVER FLORIDA
LAST NIGHT IS NOW E OF THE AREA ALONG WITH ITS ASSOCIATED
CLOUDS/CONVECTION. THE GLFMEX IS NOW PRIMARILY DOMINATED BY A
WELL-DEFINED ANTICYCLONE ALONG THE COAST OF MEXICO NEAR TAMPICO
WITH DRY NW FLOW AND MODERATE SUBSIDENCE OVER THE ENTIRE AREA.
THIS PATTERN SHOULD KEEP THE BULK OF THE AREA UNDER A
DRY/TRANQUIL WEATHER PATTERN DURING THE NEXT FEW DAYS AS THE
RIDGE AMPLIFIES NWD INTO THE CENTRAL AND E UNITED STATES
EFFECTIVELY BLOCKING UPSTREAM DISTURBANCES FROM ENTERING THE
AREA.

CARIBBEAN SEA...
THE PRIMARY FEATURE OVER THE CARIBBEAN CONTINUES TO A HIGH
AMPLITUDE MIDDLE TO UPPER LEVEL TROUGH STRETCHING FROM THE W
ATLC WATERS OVER CUBA AND HISPANIOLA TO THE SW CARIBBEAN NEAR
THE COAST OF NICARAGUA/COSTA RICA.  AS HAS BEEN THE CASE FOR THE
LAST FEW DAYS...DRY NLY FLOW IN THE MIDDLE TO UPPER LEVELS
DOMINATES THE CARIBBEAN WEST OF THE TROUGH WHILE MOIST SLY FLOW
KEEPS THE AREA E OF THE TROUGH UNSETTLED AND WET. SATELLITE
IMAGERY INDICATES SEVERAL AREAS ACTIVE CONVECTION OVER N
PORTIONS OF S AMERICA IN ASSOCIATION WITH THE ITCZ.  A SECOND
AREA OF SCATTERED CONVECTION IS LOCATED OVER THE NE CARIBBEAN
ALONG A LOW LEVEL REFLECTION OF AN UPPER TROUGH FROM THE MONA
PASSAGE TO LAKE MARACAIBO IN NW COLOMBIA.  A 50 KT SW JET FLANKS
THE E SIDE OF THE UPPER TROUGH OVER HISPANIOLA WHICH IS FOCUSING
THE BULK OF THE ACTIVITY ALONG THE N EXTENT OF THE LOW LEVEL
TROUGH...N OF 15N BETWEEN 62W-68W... OR IN THE VICINITY OF
PUERTO RICO/VIRGIN ISLANDS AND N PORTIONS OF THE LEEWARD
ISLANDS.  LATEST SATELLITE IMAGERY INDICATES NEW DEVELOPMENT S
OF THE ISLANDS WHICH IS TRAINING NWD AND AND WILL PRODUCE
LOCALLY HEAVY RAINFALL AND POSSIBLE FLOODING TODAY AND TONIGHT.
LOOKING UPSTREAM...A POTENT MIDDLE TO UPPER LEVEL SHORTWAVE
TROUGH DROPPING SEWD OVER THE BAHAMAS AND W CUBA WILL REINFORCE
THE LARGER SCALE TROUGH DURING THE NEXT 24 HOURS WITH LITTLE
OVERALL CHANGE IN THE UPPER PATTERN.  AS THE SAME TIME...A
TROPICAL WAVE WILL BE ENTERING THE E CARIBBEAN TONIGHT AND
TOMORROW BRING INCREASING LOWER LEVEL MOISTURE.  THIS EVOLUTION
SHOULD KEEP MUCH OF THE E HALF OF THE CARIBBEAN UNDER A
WET/STORMY SCENARIO DURING THE NEXT FEW DAYS.  MEANWHILE...MOST
OF THE NW CARIBBEAN WILL REMAIN UNDER DRY NLY FLOW.

SUBTROPICAL ATLANTIC...
AMPLIFYING MIDDLE TO UPPER LEVEL TROUGH-RIDGE-TROUGH PATTERN
PREVAILS OVER THE SUBTROPICAL ATLC WITH A LARGE TROUGH OVER THE
W ATLC BETWEEN 65W AND THE SE COAST OF THE UNITED STATES...BROAD
RIDGE OVER THE CENTRAL ATLC BETWEEN 20W-65W...AND TROUGH OVER
THE E ATLC NEARING THE CANARY ISLANDS.  THE W ATLC TROUGH IS THE
PRIMARY WEATHER WITH LARGE SCALE LIFT AND COPIOUS TROPICAL
MOISTURE COMING TOGETHER TO PRODUCE AN IMPRESSIVE AREA OF
SCATTERED MODERATE CONVECTION S OF 23N BETWEEN 60W-68W.  WIDELY
SCATTERED MODERATE CONVECTION IS ALSO LOCATED NE OF THE BAHAMAS
N OF 24N BETWEEN 69W-73W.  A MIDDLE TO UPPER LEVEL SHORTWAVE
TROUGH IS CURRENTLY DROPPING INTO THE W SIDE OF LARGER SCALE
TROUGH RESULTING IN AN AMPLIFICATION OF PATTERN. THIS SHOULD
KEEP MUCH OF THE CENTRAL ATLC UNDER A CLOUDY/STORMY PATTERN
DURING THE NEXT FEW DAYS.  BEST LIFT/DYNAMICS WILL BE FOCUSED
PRIMARILY BETWEEN 45W-65W. ELSEWHERE...EXTENSIVE HIGH CLOUDINESS
FROM W ATLC CONVECTION IS STREAMING NEWD AND COVERS A GOOD
PORTION OF THE CENTRAL TO E ATLC.  OVER THE FAR E ATLC...MIDDLE
TO UPPER LEVEL TROUGH IS APPROACHING THE CANARY ISLANDS BUT MOST
OF THE SIGNIFICANT WEATHER WITH THIS FEATURE IS N OF THE AREA.
AT THE SURFACE...W COLD FRONT IS ENTERING THE AREA ALONG 30N W
OF 70W WITH PREFRONTAL TROUGH EXTENDING FROM 30N73W TO S FLORIDA
NEAR PALM BEACH. THE COLD FRONT WILL CONTINUE TO PENETRATE THE W
ATLC DURING THE NEXT 24-36 HOURS AS THE SUPPORTING MIDDLE TO
UPPER LEVEL TROUGH AMPLIFIES.  ELSEWHERE...SUBTROPICAL RIDGE
EXTENDS E/W ALONG 28N WITH A 1020 MB HIGH NEAR 40W.

TROPICAL ATLANTIC...
LARGE MIDDLE TO UPPER LEVEL ANTICYCLONE NEAR 12N33W DOMINATES
MOST OF THE TROPICAL ATLC E OF 50W. DIVERGENT UPPER LEVEL FLOW
OVER THE EQUATORWIDE SIDE OF THE ANTICYCLONE IS ENHANCING ITCZ
CONVECTION BETWEEN 30W-55W. ELSEWHERE...A WEAK SHORTWAVE TROUGH
IS LOCATED ALONG 52W BUT IS NOT PRODUCING ANY SIGNIFICANT
WEATHER.

$$
RHOME




This weather bulletin was brought to you by:
www.nashvilleweather.net