000
AXPZ20 KNHC 071604
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN SEP 07 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 17.2N 
108.1W...OR ABOUT 410 NM S SE OF THE SOUTHERN TIP OF THE BAJA 
PENINSULA...MOVING W NW OR 300 DEG AT 10 KT. ESTIMATED CENTRAL 
PRESSURE IS 998 MB. MAXIMUM SUSTAINED WINDS 40 KT WITH GUSTS TO 
50 KT. NUMEROUS MODERATE TO STRONG CONVECTION NOTED WITHIN 180 
NM OF 16N110.5W. LOWELL IS FORECAST TO STRENGTHEN...BUT REMAIN A 
TROPICAL STORM THROUGH MON THEN TURN NE TOWARDS THE BAJA 
PENINSULA ON TUE. 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 05N77W TO 09N110W TO 08N140W. SCATTERED MODERATE 
ISOLATED STRONG CONVECTION WITHIN 120 NM OF 06N79W.

SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 60 
NM OF 21N107W.

...DISCUSSION...

AN UPPER TROUGH LIES ALONG THE N AND NW PERIPHERY OF THE 
DISCUSSION AREA...FROM 34N117W TO 33N129W TO 29N138W THEN SW 
INTO A SMALL UPPER CYCLONE AT 22N146W. THIS UPPER TROUGH SPLITS 
TWO UPPER RIDGES...ONE ORIENTATED NE TO SW AND ORIGINATING FROM 
AN UPPER ANTICYCLONE AT 33N148W...WITH THE SOUTHERN CREST OVER 
HAWAII. THE SECOND UPPER RIDGE LIES E TO W ACROSS MOST OF THE 
DISCUSSION AREA. UPPER ANTICYCLONES ARE CENTERED AT 24N123W AND 
AT 21N131W WITH A RIDGE EXTENDING SW TO A CREST NEAR 11N145W. AN 
UPPER TROUGH NOW EXTENDS S OVER WESTERN MEXICO FROM 32N113W TO 
23N114W. THIS TROUGH HAS SEPARATED THE ANTICYCLONIC FLOW 
DESCRIBED ABOVE OVER THE PACIFIC FROM ANOTHER ANTICYCLONE OVER 
THE WESTERN GULF OF MEXICO. THIS TROUGH IS EXPECTED TO AMPLIFY S 
ALONG 120W BECOMING THE PRIMARY STEERING MECHANISM OF TROPICAL 
STORM LOWELL. FOR NOW...THESE UPPER FEATURES COMBINE TO DRY OUT 
THE UPPER LEVELS OF THE DISCUSSION AREA TO THE W OF A LINE FROM 
31N103W TO 22N110W TO 14N140W. AT THE LOW LEVELS...A BROAD 
SURFACE RIDGE LIES ROUGHLY ALONG 32N143W TO 27N115W.

AN UPPER TROUGH OVER THE SE GULF OF MEXICO CONTINUES SW ACROSS 
OLD MEXICO ALONG 20N96W INTO THE E PACIFIC NEAR 17N105W TO NEAR 
09N100W WHERE IT LOSES IDENTITY. IT APPEARS AN ANTICYLONE IS
FORMING OVER TROPICAL STORM LOWELL WITH A RIDGE SW TO NEAR 
14N128W. THE UPPER FLOW IS NE TO E OVER THE TROPICAL E PACIFIC 
BETWEEN 92W AND 105W. THE ASSOCIATED UPPER DIFFLUENCE IS 
ENHANCING CONVECTION OVER THE BAY OF CAMPECHE AND OF COURSE 
ENHANCING CONVECTION NEAR THE TROPICAL STORM...WITH THE DEBRIS 
MOISTURE ADVECTED SW BETWEEN 94W AND 120W...WITH SOME SPREADING 
S OF THE EQUATOR NEAR 100W. CONVECTION IS ALSO ENHANCED ALONG 
THE PACIFIC COAST OF COLOMBIA...WITH THE DEBRIS MOISTURE 
BEGINNING TO SPREAD W OVER THE AREA N OF 03N E OF 83W.

$$
NELSON