[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 041800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU OCT 04 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.

...SPECIAL FEATURES...

AS OF 1500 UTC...A 1007 MB LOW PRESSURE SYSTEM IS OVER THE
NORTH-CENTRAL GULF OF MEXICO NEAR 27N91W MOVING W-NW NEAR 10 KT.
SHOWER AND THUNDERSTORM ACTIVITY ASSOCIATED WITH THIS SYSTEM IS
CURRENTLY LIMITED. A WELL DEFINED SWIRL OF LOW CLOUDS IS EVIDENT
WITH THIS LOW...BUT SATELLITE AND LIGHTNING DATA ARE ONLY
DEPICTING ISOLATED TSTM ACTIVITY WELL E OF THE CENTER FROM
26N-29N BETWEEN 87W-90W. NONETHELESS...THERE IS STILL SOME
POTENTIAL FOR THIS SYSTEM TO BECOME A TROPICAL OR SUBTROPICAL
DEPRESSION OVER THE NEXT DAY OR SO AS IT APPROACHES THE TEXAS
COAST.

A BROAD 1011 MB LOW PRESSURE AREA IS JUST E OF THE BAHAMAS
NEAR 26N73W...MOVING SLOWLY SW. THIS AFTERNOONS VISIBLE IMAGERY
SHOWS MORE THAN ONE LOW LEVEL VORTICITY MAXIMUM IN THE
VICINITY...SO HAVE OPTED WITH A MEAN CENTER FOR THE 12 AND 1500
UTC MAPS. SHOWER AND TSTM ACTIVITY IS MOSTLY S/SE OF THE LOW
LEVEL CIRCULATIONS DUE TO UPPER NLY FLOW OVER THE AREA. THE
DISORGANIZED SCATTERED SHOWER AND ISOLATED TSTMS ARE MOST
CONCENTRATED FROM 20N-26N BETWEEN 64W-74W. ANY DEVELOPMENT OF
THIS SYSTEM IS EXPECTED TO BE SLOW TO OCCUR

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 45W S OF 17N MOVING W 10-15 KT. A 1012 MB
LOW IS ALONG THE WAVE AXIS NEAR 10N. DISORGANIZED SCATTERED
SHOWERS AND TSTMS ARE WITHIN 150 NM EITHER SIDE OF THE AXIS
MAINLY N OF 7N. UPPER LEVEL WINDS HAVE BECOME LESS FAVORABLE FOR
THIS SYSTEM TO BECOME A TROPICAL CYCLONE...WITH W/SW FLOW ALOFT
STRETCHING THE CLOUD TOPS OVER THE AREA TO THE E/NE.

TROPICAL WAVE IS ALONG 55W SOUTH OF 15N MOVING WEST 10-15 KT.
THIS REMAINS DIFFICULT TO LOCATE IN SATELLITE IMAGERY AND THE
SURROUNDING BUOY/SHIP OBSERVATIONS...AND HAS BEEN THIS WAY FOR
THE LAST COUPLE OF DAYS. THUS...THE WAVE MAY NEED TO BE DROPPED
OR RELOCATED ON FUTURE MAPS. SHOWER ACTIVITY REMAINS MINIMAL IN
THE AREA.

...THE ITCZ...
AXIS CENTERED ALONG 10N13W 5N25W 10N43W 10N54W 9N62W. ISOLATED
MODERATE CONVECTION IS WITHIN 150NM S OF THE AXIS BETWEEN
16W-23W. SCATTERED MODERATE IS WITHIN 180NM N/90NM S OF THE AXIS
BETWEEN 23W-33W.

DISCUSSION...

THE GULF OF MEXICO...
THE SPECIAL FEATURE OVER THE NORTH CENTRAL GULF IS THE DOMINANT
WEATHER MAKER IN THE BASIN...THOUGH IS GENERATING MINIMAL
SHOWER/TSTM ACTIVITY AT THE MOMENT. WINDS ASSOCIATED WITH THE
LOW ARE MOSTLY 15 KT OR BELOW EXCEPT 15-20 KT NE OF THE CENTER
WHERE THE LOW IS INTERACTING WITH HIGH PRESSURE RIDGING SW FROM
THE MID ATLANTIC COAST. THE WELL DEFINED UPPER LOW THAT HAS BEEN
AT LEAST PARTLY SUPPORTING THE SPECIAL FEATURE HAS
FRAGMENTED...WITH ONE LARGE UPPER LOW NOW ALONG THE COAST OF
MEXICO NEAR 19N96W...AND ANOTHER MID TO UPPER CYCLONIC
CIRCULATION NOTED IN WV IMAGERY NEAR 27N89W. THE LATTER IS
SUPPORTING ALMOST THE ONLY SHOWER/TSTM ACTIVITY OVER THE GULF AT
THE MOMENT...AND AS NOTED ABOVE IS WELL E OF THE SFC LOW FROM
26N-29N BETWEEN 87W-90W. THE NEXT ITEM OF INTEREST WILL BE THE
LOW PRES E OF THE BAHAMAS...WHICH IS EXPECTED TO MOVE SW ACROSS
W CUBA BY SAT AND BE NEAR THE YUCATAN CHANNEL SUN AND MON. WINDS
WILL INCREASE OVER THE NE GULF SAT THROUGH MON AS THE GRADIENT
INCREASES BETWEEN THE LOW AND A RIDGE TO THE N.

THE CARIBBEAN SEA...
ACTIVE WEATHER PERSISTS BETWEEN THE COASTS OF COLOMBIA AND CUBA
THIS AFTERNOON...WITH SCATTERED MODERATE CONVECTION NOTED N OF
11N BETWEEN 74W-81W. THIS ACTIVITY IS BEING SUPPORTED BY THE
NEWLY FORMED SFC TROUGH THAT EXTENDS ALONG 82W FROM 12N-20W...IN
ADDITION TO DIFFLUENT FLOW ALOFT AROUND THE PERIPHERY OF THE
UPPER HIGH NEAR THE STRAITS OF FLORIDA. THE SFC TROUGH IS
EXPECTED TO MOVE LITTLE OVER THE NEXT DAY OR SO...WHICH WILL
KEEP SCATTERED SHOWER AND TSTM ACTIVITY IN THE VICINITY.
SCATTERED SHOWERS/TSTMS ARE ALSO AFFECTING THE LEEWARD ISLANDS
AND NE CARIBBEAN N OF 15N E OF 63W. A SFC TROUGH EXTENDS THROUGH
THIS VICINITY AS WELL...FROM THE ATLC NEAR 21N62W TO THE NE
CARIB NEAR 16N65W. THE LOW LEVEL CYCLONIC TURNING IN THIS
VICINITY MAY BE ASSOCIATED WITH SOME OF THE ENERGY ASSOCIATED
WITH THE REMNANTS OF KAREN. THE REMAINING NOTABLE CONVECTION IS
OVER THE FAR SW PORTION S OF 10N...ASSOCIATED WITH THE ITCZ.
ELSEWHERE CONDITIONS ARE FAIRLY QUIET. TRADE FLOW HAS BEEN
DISRUPTED QUITE A BIT OVER MUCH OF THE BASIN DUE TO THE
TROUGHING OVER THE NW AND NE PORTIONS. THE EXCEPTION IS MORE
TYPICAL MODERATE ELY WINDS BETWEEN SOUTH AMERICA AND HISPANIOLA.

THE ATLANTIC OCEAN...
THE SPECIAL FEATURE E OF THE BAHAMAS DOMINATES THE PATTERN OVER
THE WRN ATLC AS DESCRIBED ABOVE. THIS IN ADDITION TO VERY
DIFFLUENT FLOW OVER THE AREA...BETWEEN THE UPPER HIGH NEAR
24N79W AND AN ELONGATED UPPER LOW NEAR 26N56W...IS SUPPORTING
WIDESPREAD CLOUDINESS AND SHOWER ACTIVITY S OF 27N BETWEEN
60W-75W. ELY FLOW AND THE ASSOCIATED WIND WAVES/SWELL ARE
EXPECTED TO INCREASE AGAIN OVER THE WRN ATLC INTO THE FIRST PART
OF THE WEEKEND...AS HIGH PRES NEAR THE MID ATLC COAST BUILDS S
AND INTERACTS WITH THE BROAD LOW NEAR THE BAHAMAS.

THE REMNANTS OF MELISSA ARE NEAR 22N51W ANALYZED AS A
1015 MB LOW. THE EX-TROPICAL CYCLONE IS INTERACTING WITH AN
APPROACHING FRONTAL SYSTEM TO PRODUCE SCATTERED MODERATE
CONVECTION FROM 22N-26N BETWEEN 41W-52W. SIGNIFICANT
REDEVELOPMENT IS NOT EXPECTED DUE TO STRONG UPPER-LEVEL W/SW
WINDS AHEAD OF AN UPPER TROUGH. THE LINGERING COLD FRONT
BOUNDARY ENTERS THE AREA NEAR 32N26W AND CONTINUES SW TO 25N43W
THEN WNW TO 29N59W. SCATTERED SHOWERS/ISOLATED TSTMS ARE
ELSEWHERE WITHIN 90 NM OF THE FRONT. THE REMAINDER OF THE E ATLC
IS DOMINATED BY A PAIR OF 1020 MB HIGHS...ONE NEAR THE CANARY
ISLANDS NEAR 29N13W AND THE OTHER NEAR 24N26W. THIS ALONG WITH
STABLE AIR AND A SURGE OF AFRICAN DUST ARE PRODUCING FAIRLY
QUIET CONDITIONS E OF 35W..EXCEPT FOR THAT AREA JUST AHEAD OF
THE FRONT AS OUTLINED ABOVE.

$$
WILLIS


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