[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 051803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI OCT 05 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...TROPICAL WAVES...
AN ATLANTIC OCEAN TROPICAL WAVE IS TILTED ALONG 18N50W
4N48W...THAT HAS A WEAK 1011 MB LOW ALONG THE AXIS NEAR
12N49W...MOVING W 10-15 KT. DISORGANIZED SCATTERED SHOWER AND
TSTM ACTIVITY IS FROM 9N-18N BETWEEN 43W-49W...WHICH IS MOSTLY E
OF THE AXIS DUE TO APPROX 30 KT OF WLY SHEAR OVER THE AREA. THE
SFC LOW ALONG THE WAVE MAY DISSIPATE OVER THE NEXT DAY OR SO DUE
TO THE HOSTILE ENVIRONMENT.

...THE ITCZ...
AXIS CENTERED ALONG 9N12W 5N26W 11N44W 9N53W 8N61W. ISOLATED
CLUSTERS OF MODERATE CONVECTION ARE WITHIN 250NM EITHER SIDE OF
THE AXIS E OF 17W. SIMILAR ACTIVITY IS N OF THE AXIS FROM 6N-9N
BETWEEN 18N-26W.

DISCUSSION...

THE GULF OF MEXICO...
A 1009 MB SFC LOW IS OVER THE NW GULF NEAR 28N93W JUST OFF THE
COAST OF LOUISIANA AND THE UPPER TEXAS COAST. THERE IS A LITTLE
MORE TSTM ACTIVITY ASSOCIATED WITH THIS LOW THIS AFTERNOON.
SATELLITE...LIGHTNING...AND RADAR DATA DEPICT A SMALL CLUSTER OF
MODERATE CONVECTION WITHIN 60 NM E SEMICIRCLE...WITH ISOLATED
MOSTLY LOW TOPPED SHOWER ACTIVITY ELSEWHERE N OF 27N W OF 91W.
THE LOW IS EXPECTED TO MOVE INLAND OVER SOUTHWESTERN LOUISIANA
OR SOUTHEASTERN TEXAS TONIGHT. INTERESTS IN TEXAS AND LOUISIANA
SHOULD CONTINUE TO MONITOR THE PROGRESS OF THIS SYSTEM UNTIL IT
MOVES INLAND. THE ONLY OTHER TSTM ACTIVITY OVER THE GULF IS JUST
S OF THE FL PANHANDLE THROUGH SE LOUISIANA...WITH ISOLATED CELLS
NOTED N OF 27N BETWEEN 84W-90W. THIS ACTIVITY IS ASSOCIATED WITH
LOW LEVEL CONVERGENCE BETWEEN THE SLY FLOW E OF THE LOW OFF WRN
LOUISIANA...COLLIDING WITH MODERATE ELY WINDS OVER THE NE GULF
AROUND RIDGING FROM NEW ENGLAND. AN UPPER COL REGION IS ALSO
OVER THE N CENTRAL GULF...BETWEEN AN UPPER HIGH NEAR THE YUCATAN
CHANNEL AND ANOTHER UPPER HIGH CENTERED ABOVE TEXARKANA. DRY AND
MOSTLY STABLE CONDITIONS NOTED OVER MUCH OF THE GULF S OF 27N.
ELY FLOW EXPECTED TO INCREASE OVER THE ERN GULF AS BROAD LOW
PRESSURE FROM THE NW CARIBBEAN INTERACTS WITH PERSISTENT RIDGING
FROM THE MID ATLC COAST.

THE CARIBBEAN SEA...
ACTIVE WEATHER PERSISTS BETWEEN COLOMBIA AND CUBA THIS
AFTERNOON...WITH A SFC TROUGH EXTENDING OVER THE NW PORTION
ALONG 21N82W 13N77W. VISIBLE IMAGERY ALSO DEPICTS A WEAK LOW MAY
BE FORMING JUST WSW OF THE CAYMAN ISLANDS NEAR 19N82W. UPPER
RIDGING DOMINATES MUCH OF THE BASIN THIS AFTERNOON FROM THE
UPPER HIGH JUST NW OF THE YUCATAN CHANNEL IN THE SRN GOMEX. IN
ADDITION TO THE MENTIONED SFC AND UPPER FEATURES...COLLIDING
CONVECTIVE BOUNDARIES ARE ALSO HELPING TO SUPPORT WIDESPREAD
CLOUDINESS AND SHOWER ACTIVITY WITH EMBEDDED TSTMS BETWEEN
71W-85W. THE MOST PRONOUNCED TSTM ACTIVITY IS BETWEEN THE COAST
OF COLOMBIA AND SE JAMAICA BETWEEN 73W-78W. QUITE A BIT OF
SHOWER ACTIVITY WITH EMBEDDED TSTMS ARE ALSO AFFECTING THE NORTH
CENTRAL AND NORTHEAST CARIBBEAN. THIS ACTIVITY IS VERY EVIDENT
FROM THE SAN JUAN RADAR...AND IS AFFECTING HISPANIOLA E THROUGH
THE LEEWARD ISLANDS. THE DRIVING FORCE BEHIND THIS ACTIVITY IS
PRIMARILY THE ELONGATED SFC TROUGH EXTENDING THROUGH THE BAHAMAS
AND SW NORTH ATLC...THOUGH THE UPPER LOW N OF THE MONA PASSAGE
IS ALSO PROVIDING ADDITIONAL FUEL. A WEAK 1011 MB LOW IS ALSO
ANALYZED JUST N OF THE VIRGIN ISLANDS NEAR 19N65W AS DICTATED BY
THE SAN JUAN RADAR AND THE SURROUNDING SFC OBSERVATIONS. THERE
IS SOME DEBATE ON IF SOME OF THIS ENERGY COULD BE ASSOCIATED
WITH THE EX-TROPICAL CYCLONE KAREN.

COMPUTER MODEL GUIDANCE SUGGESTS THAT BROAD LOW PRES WILL SLOWLY
CONSOLIDATE OVER THE NW CARIBBEAN OVER THE NEXT COUPLE OF DAYS
WITH WEAK RIDGING OVER THE ERN CARIB. TRADE FLOW WILL THUS
REMAIN DISRUPTED...WITH LIGHT TO MODERATE SE/S WINDS OVER THE
CENTRAL AND ERN PORTIONS...AND WINDS OVER THE NW PORTION
DEPENDENT ON THE DEVELOPMENT OF THE SFC LOW ANTICIPATED.

THE ATLANTIC OCEAN...
A VERY MESSY AND COMPLEX WEATHER PATTERN DOMINATES THE SW
PORTION OF THE AREA. THE OVERALL SFC PATTERN CONSISTS OF AN
ELONGATED AREA OF LOW PRESSURE WITH MULTIPLE VORTICITY MAXIMUMS.
AT 1200 UTC A TROUGH WAS ANALYZED FROM FAR SE FLORIDA TO JUST N
OF THE VIRGIN ISLANDS...WITH A MEAN 1010 MB LOW NEAR 23N74W AND
ANOTHER 1011 MB CENTER JUST NE OF PUERTO RICO NEAR 19N65W. THE
LATTER APPEARS TO BE THE DOMINANT FEATURE AND MORE SIGNIFICANT
WEATHER PRODUCER...WITH WIDESPREAD SHOWER ACTIVITY WITH EMBEDDED
TSTMS S OF 24N BETWEEN 60W-70W. MORE ON THIS SYSTEM FOUND IN
CARIBBEAN SECTION. TROUGHING N OF THE BROAD LOW PRESSURE AREA IN
ADDITION TO DIFFLUENT FLOW ALOFT IS SUPPORTING SCATTERED
SHOWER/TSTM ACTIVITY OFF AND ALONG THE COAST OF FLORIDA W OF
77W. THE INTERACTION BETWEEN THE BROAD TROUGHING NEAR THE
BAHAMAS AND HIGH PRES RIDGING S FROM THE MID ATLC COAST WILL
PRODUCE MODERATE TO STRONG ELY WINDS AND STEEP WIND WAVES/SWELL
OFFSHORE FLORIDA OVER THE NEXT COUPLE OF DAYS.

THE CENTRAL ATLC SFC PATTERN DOES NOT GET MUCH MORE CLEAR CUT
THAN THE MESS NEAR THE BAHAMAS. AN OLD FRONTAL ZONE ENTERS THE
AREA NEAR 32N20W AND CONTINUES SW TO 25N32W THEN W TO 27N56W.
MEANWHILE...THE REMNANTS OF MELISSA ARE NOW ANALYZED AS A TROUGH
ALONG 25N52W 20N56W. THIS CIRCULATION APPEARS TO BE GETTING
ABSORBED INTO THE BAROCLINIC ZONE FURTHER N THOUGH.
FURTHERMORE...MOISTURE FROM THE TROPICAL WAVE NEAR 50W IS ALSO
SPREADING INTO THIS OVERALL AREA. THE END RESULT IS WIDESPREAD
DISORGANIZED CLOUDINESS AND SHOWERS N OF 18N BETWEEN
37W-55W...WITH THE MOST PRONOUNCED TSTM ACTIVITY NOTED FROM
20N-27N BETWEEN 40W-48W. THIS IS ALSO BEING SUPPORTED BY LIFT
AHEAD OF THE MID TO UPPER TROUGHING IN THE VICINITY. THE
REMAINDER OF THE E ATLC IS MUCH QUIETER...WITH STABLE CONDITIONS
AND A PAIR OF 1020 MB SFC HIGHS OVER THE AREA NEAR 22N27W AND
30N12W.

$$
WILLIS


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