000
AXPZ20 KNHC 082137
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC MON SEP 08 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LOWELL...AT 2100 UTC...CENTERED NEAR 19.8N 112.1W 
...OR ABOUT 100 MILES NW OF SOCORRO ISLAND AND ABOUT 255 MILES 
SW OF THE SOUTHERN TIP OF BAJA CALIFORNIA. LOWELL IS MOVING NW 
OR 315 DEG AT 10 KT. ESTIMATED CENTRAL PRESSURE IS 1000 MB. 
MAXIMUM SUSTAINED WINDS ARE 45 KT WITH GUSTS TO 55 KT. NUMEROUS 
MODERATE TO STRONG CONVECTION IS NOTED WITHIN 240 NM OVER THE SW 
AND WITHIN 60 NM OVER THE NE SEMICIRCLES OF CENTER. SCATTERED 
MODERATE ISOLATED STRONG CONVECTION IS ALSO OBSERVED WELL E OF 
THE CENTER...WITHIN 15 NM EITHER SIDE OF LINE FROM 16.5N102.5W 
TO 22N109W. LOWELL IS FORECAST TO REMAIN A  TROPICAL STORM 
MOVING NW TONIGHT...TURNING TO THE N TUE...THEN TRACK NE TOWARDS 
THE BAJA PENINSULA ON WED AND CROSS THE SOUTHERN BAJA PENINSULA 
THU...AND INTO THE GULF OF CALIFORNIA FRI AND EVENTUALLY INTO 
MEXICO SAT. PLEASE REFER TO THE LATEST NHC PUBLIC ADVISORY UNDER 
AWIPS HEADER MIATCPEP3 OR WMO HEADER WTPZ33 KNHC AND THE FULL 
FORECAST ADVISORY UNDER AWIPS HEADER MIATCMEP3 OR WMO HEADER 
WTPZ23 KNHC FOR MORE DETAILS. 

...ITCZ...

ITCZ AXIS ALONG 07N80W TO 06N90W TO 11N107W TO 07N135W TO 
08N140W. SCATTERED MODERATE ISOLATED STRONG IS NOTED N OF 04N 
BETWEEN 84W AND 87W AND ALSO WITHIN 60 NM 05N96W AND WITHIN 45 
NM EITHER SIDE OF LINE FROM 10N118W TO 07N133W.

...DISCUSSION...

AN UPPER TROUGH LIES ALONG THE NORTHERN BOUNDARY OF THE 
DISCUSSION AREA...FROM 33N116W TO 31N129W TO 29N140W THEN TURNS 
SW INTO A SMALL UPPER CYCLONE AT 24N150W. IMMEDIATELY TO THE S 
OF THIS TROUGH...AN UPPER ANTICYCLONE IS CENTERED AT 23N135W 
WITH A RIDGE SW TO 16N143W. A RIDGE ALSO EXTENDS E TO NEAR 
25N121W...BUT IS RETRACING WESTWARD WITH TIME AS A SECONDARY 
UPPER TROUGH SWINGS SE REINFORCING THE TROUGH MENTIONED ABOVE 
AND EVENTUALLY MERGING WITH YET ANOTHER UPPER TROUGH THAT HAS 
NEARLY STALLED ALONG LINE 32N110W TO 22N122W. AN UPPER 
ANTICYCLONE IS CENTERED OVER THE WESTERN OLD MEXICO NEAR 23N106W 
WITH ITS RIDGE EXTENDING SW THROUGH ANOTHER SMALL UPPER 
ANTICYCLONE OVER TROPICAL STORM LOWELL. THESE UPPER FEATURES ALL 
COMBINE TO DRY OUT THE UPPER LEVELS OF THE DISCUSSION AREA TO 
THE W OF A WELL DEFINED LINE FROM 32N104W TO 21N119W TO 12N140W. 
AT THE LOW LEVELS...A BROAD SURFACE RIDGE LIES ROUGHLY ALONG 
32N143W TO 24N122W. 

THE UPPER FLOW IS NE TO E...IN RESPONSE TO THE COMBINED UPPER 
RIDGES DESCRIBED ABOVE...OVER THE TROPICAL E PACIFIC BETWEEN 96W 
AND 130W. THE ASSOCIATED UPPER DIFFLUENCE ENHANCED CONVECTION 
OVER THE WESTERN GULF OF MEXICO AND OF COURSE NEAR TROPICAL 
STORM LOWELL. THE RESULTANT DEBRIS MOISTURE IS ADVECTED SW 
ROUGHLY WITHIN 600 NM EITHER SIDE OF LINE 22N98W TO 08N120W... 
WITH SOME SPREADING S OF THE EQUATOR BETWEEN 110W AND 120W.  

A BROAD UPPER TROUGH IS NOTED OVER THE DEEP TROPICS TO THE S OF 
08N ALONG 88W. CONVECTION IS ENHANCED FROM 04N TO 10N E OF 
85W...WITH THE DEBRIS MOISTURE BEGINNING TO SPREAD W OVER THE 
AREA N OF 03N E OF THE UPPER TROUGH. A CLUSTER OF MODERATE 
CONVECTION HAS FLARED WITHIN 30 NM OF 05N96W...DECREASING AT THE 
MOMENT.

OUTLOOK...THE SECONDARY UPPER TROUGH DESCRIBED ABOVE IS EXPECTED 
TO AMPLIFY S ALONG 122W BECOMING THE PRIMARY STEERING MECHANISM 
FOR LIFTING TROPICAL STORM LOWELL N AND LATER NE ACROSS THE BAJA 
PENINSULA AND GULF OF CALIFORNIA. 

$$
NELSON