000
AXPZ20 KNHC 091553
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE SEP 09 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 21.0N 
113.5W...OR ABOUT 265 MILES W SW OF THE SOUTHERN TIP OF BAJA 
CALIFORNIA AND ABOUT 275 MILES S SW OF CABO SAN LAZARO MEXICO.
LOWELL IS MOVING NW OR 315 DEG AT 06 KT. ESTIMATED CENTRAL 
PRESSURE IS 1002 MB. MAXIMUM SUSTAINED WINDS ARE 40 KT WITH 
GUSTS TO 50 KT. SCATTERED MODERATE TO STRONG CONVECTION IS NOTED 
WITHIN 90 NM OVER THE SW QUADRANT. LOWELL IS FORECAST TO REMAIN 
A MINIMAL TROPICAL STORM MOVING N TONIGHT...WEAKENING TO A 
TROPICAL DEPRESSION AND TURNING TO THE NE TOWARDS THE BAJA 
PENINSULA ON WED AND CROSSING THE SOUTHERN BAJA PENINSULA EARLY 
THU...AND INTO THE GULF OF CALIFORNIA AS A REMNANT LOW PRES FRI 
AND EVENTUALLY DISSIPATING OVER INTERIOR NW OLD MEXICO ON 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 06N77W TO 07N100W TO 09N115W TO 08N140W.
SCATTERED MODERATE TO STRONG CONVECTION IS NOTED WITHIN 75 NM OF 
05.5N78.5W AND WITHIN 60 NM OF 05.5N87W.

...DISCUSSION...

AN UPPER TROUGH HAS PUSHED SE INTO THE DISCUSSION AREA ALONG 
POINTS 34N119W TO 31N124W MERGING WITH ANOTHER STALLED UPPER 
TROUGH EXTENDING FROM 31N135W TO 29N142W WHERE THE TROUGH TURNS 
SW INTO AN UPPER CYCLONE AT 26N149W. IMMEDIATELY TO THE S OF 
THESE UPPER TROUGHS...AN UPPER ANTICYCLONE HAS SHIFTED W TO NEAR 
22N136W WITH ITS EASTERN RIDGE ERODING WESTWARD AS THE STRONG 
UPPER TROUGH AMPLIFIES S ALONG 122W. AN UPPER ANTICYCLONE 
ASSOCIATED WITH TROPICAL STORM LOWELL IS CENTERED NEAR 22N114W 
AND HAS BECOME THE DOMINATE ANTICYCLONE...WITH ITS RIDGE 
EXTENDING NE ACROSS NORTHERN OLD MEXICO CRESTING AT 27N103W. A 
RIDGE ALSO EXTENDS SW TO A SMALL UPPER ANTICYCLONE AT 19N129W. 
THESE UPPER FEATURES ALL COMBINE DRYING OUT THE UPPER LEVELS OF 
THE DISCUSSION AREA TO THE W OF A WELL DEFINED LINE FROM 32N107W 
TO 22N120W TO 13N140W. AT THE LOW LEVELS...A BROAD SURFACE RIDGE 
LIES ROUGHLY ALONG 32N138W TO 25N118W. 

THE UPPER FLOW IS NE TO E...IN RESPONSE TO THE COMBINED UPPER 
RIDGES DESCRIBED ABOVE...OVER THE TROPICAL E PACIFIC BETWEEN 96W 
AND 140W. THE ASSOCIATED UPPER DIFFLUENCE IS ENHANCING 
CONVECTION AGAIN OVER THE WESTERN GULF OF MEXICO ALONG THE E 
COAST OF OLD MEXICO FROM 18N TO 26N. CONVECTION IS ALSO ENHANCED 
UNDER THE UPPER RIDGE ALONG THE W COAST OF OLD MEXICO FROM 19N 
WELL UP INTO THE GULF OF CALIFORNIA NEAR 27N. THE RESULTANT 
DEBRIS MOISTURE IS ADVECTED SW...MERGING WITH DEBRIS FROM 
LOWELL...INTO A PLUME ROUGHLY WITHIN 540 NM EITHER SIDE OF LINE 
23N102W TO 06N129W...WITH SOME OF THE MOISTURE SPREADING S TO 
THE EQUATOR BETWEEN 112W AND 130W.  

A BROAD UPPER TROUGH IS NOTED OVER THE DEEP TROPICS TO THE S OF 
08N ALONG 100W. CONVECTION IS ENHANCED FROM 04N TO 10N E OF 
90W...WITH THE DEBRIS MOISTURE BEGINNING TO SPREAD W OVER THE 
AREA N OF 03N E OF THE UPPER TROUGH. A SMALL CLUSTER OF MODERATE 
CONVECTION HAS FLARED WITHIN 15 NM OF 05N99W.

$$
NELSON