000
AXPZ20 KNHC 081559
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC MON SEP 08 2008

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

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1545 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LOWELL...AT 1500 UTC...CENTERED NEAR 19.0N 111.2W 
...20 MILES NW OF SOCORRO ISLAND AND ABOUT 280 MILES S SW OF THE 
SOUTHERN TIP OF BAJA CALIFORNIA. LOWELL IS MOVING NW OR 305 DEG 
AT 08 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 180 NM OVER THE SW 
QUADRANT. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS ALSO 
OBSERVED WELL E OF THE CENTER...WITHIN 15 NM EITHER SIDE OF LINE 
FROM 20.5N105.5W TO 24N109W. LOWELL IS FORECAST TO REMAIN A  
TROPICAL STORM MOVING NW THROUGH TUE...TURNING TO THE N TUE 
NIGHT...THEN TRACK NE TOWARDS THE BAJA PENINSULA ON WED AND 
CROSS THE SOUTHERN BAJA PENINSULA THU...AND INTO THE GULF OF 
CALIFORNIA FRI INTO 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 LIES ALONG 07N80W TO 06N90W TO 11N107W TO 07N135W TO 
08N140W. SCATTERED MODERATE ISOLATED STRONG IS NOTED N OF 04N
E OF 85W AND ALSO WITHIN 30 NM OF LINE 10N120W TO 08N131W.

...DISCUSSION...

AN UPPER TROUGH LIES ALONG THE NORTHERN BOUNDARY OF THE 
DISCUSSION AREA...FROM 33N118W TO 31N135W TO 28N144W THEN TURNS 
SW INTO A SMALL UPPER CYCLONE AT 22N149W. IMMEDIATELY TO THE S 
OF THIS TROUGH...AN UPPER ANTICYCLONE IS CENTERED AT 22N133W 
WITH A RIDGE SW TO 16N133W. A RIDGE ALSO EXTENDS E TO NEAR 
27N119W...BUT IS WEAKENING AND RETRACING WESTWARD AS A SECONDARY 
UPPER TROUGH SWINGS S AND ABOUT TO MERGE WITH YET ANOTHER UPPER 
TROUGH THAT HAS NEARLY STALLED ALONG LINE 32N116W TO 25N117W. AN 
UPPER ANTICYCLONE IS CENTERED OVER THE WESTERN OLD MEXICO WITH 
ITS RIDGE EXTENDING SW THROUGH ANOTHER UPPER ANTICYCLONE OVER 
TROPICAL STORM LOWELL...WITH THE RIDGE CONTINUING SW TO A CREST 
AT 17N122W. THESE UPPER FEATURES ALL COMBINE TO DRY OUT THE 
UPPER LEVELS OF THE DISCUSSION AREA TO THE W OF A WELL DEFINED 
LINE FROM 31N106W TO 22N120W TO 12N140W. AT THE LOW LEVELS...A 
BROAD SURFACE RIDGE LIES ROUGHLY ALONG 32N143W TO 26N117W. 

THE UPPER FLOW IS NE TO E...IN RESPONSE TO THE COMBINED UPPER 
RIDGES DESCRIBED ABOVE...OVER THE TROPICAL E PACIFIC BETWEEN 90W 
AND 130W. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING 
CONVECTION ALONG THE EASTERN COAST OF OLD MEXICO FROM 18N TO 
26N...AND OF COURSE ENHANCING CONVECTION MOSTLY SW OF TROPICAL 
STORM LOWELL. THE RESULTANT DEBRIS MOISTURE IS ADVECTED SW 
ROUGHLY WITHIN 600 NM EITHER SIDE OF LINE 20N100W TO 08N120W... 
WITH SOME SPREADING S OF THE EQUATOR BETWEEN 106W AND 120W.  

A BROAD UPPER TROUGH IS NOTED OVER THE DEEP TROPICS TO THE S OF 
10N ALONG 92W. 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 88W. A CLUSTER OF INCREASING CONVECTION HAS 
FLARED WITHIN 30 NM OF 05N95W.

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