000 AXPZ20 KNHC 101546 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC WED SEP 10 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 1515 UTC. ...SPECIAL FEATURES... TROPICAL DEPRESSION LOWELL CENTERED NEAR 22.3N 112.1W OR ABOUT 125 NM WSW OF THE SOUTHERN TIP OF BAJA CALIFORNIA AT 10/1500 UTC MOVING NE OR 035 DEG AT 06 KT. ESTIMATED CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WINDS ARE 30 KT WITH GUSTS TO 40 KT. LOWELL HAS PASSED THE WESTERN END OF A LARGE SUBTROPICAL RIDGE OVER NORTHERN MEXICO AND IS NOW BEING STEERED NE AS IT ENCOUNTERS INCREASING MID-LATITUDE WESTERLY FLOW BEGINNING TO DIG SOUTHWARD OVER THE WESTERN CONUS. A COMPARISON OF LOWELL'S RECENT PROGRESS AND ITS FORECAST TRACK WITH A RECENT SNAPSHOT OF SEA SURFACE TEMPERATURES ACROSS THE REGION INDICATES THAT LOWELL IS RIDING CLOSE TO IF NOT JUST E OF THE 26.5C ISOTHERM. WITH STILL RELATIVELY WARM WATER ALONG ITS PATH AND CIMSS SHEAR ANALYSES INDICATING UNDER 10 KT OF S TO SW SHEAR...DISORGANIZED CONVECTIVE CLUSTERS HAVE CONTINUED DEVELOPING WITHIN ABOUT 100 NM OF THE NORTHERN SEMICIRCLE. HOWEVER...THE WEAKENING TROPICAL CYCLONE IS FORECAST TO REMAIN ON A NE PATH THROUGH SOUTHERN BAJA CALIFORNIA...INTO THE SOUTHERN GULF OF CALIFORNIA BEFORE FINALLY DISSIPATING OVER NW MAINLAND MEXICO ON FRI. MID- TO UPPER-LEVEL MOISTURE ASSOCIATED WITH THE REMAINS OF LOWELL ARE EXPECTED TO SPREAD INTO THE DESERT SW AND SOUTHERN ROCKIES IN ADVANCE OF AN AMPLIFYING MID- TO UPPER-LEVEL TROUGH FRI AND 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 LIES 09N85W TO 06N96W TO 08N110W...THEN RESUMES FROM T.D. LOWELL TO 16N116W TO 11N128W TO 06N140W. NUMEROUS MODERATE ISOLATED STRONG CONVECTION WITHIN 90 NM N OF AXIS BETWEEN 128W AND 130W. NUMEROUS MODERATE CONVECTION WITHIN 330 NM SW OF MANZANILLO MX. SCATTERED MODERATE WITHIN 30 NM EITHER SIDE OF LINE FROM 15N96W TO 10N93W. ...DISCUSSION... THE WESTERN END OF THE ITCZ OVER THE TROPICAL EAST PACIFIC EXTENDS SOUTHWEST FROM TROPICAL DEPRESSION LOWELL TO AROUND 11N128W AND FINALLY TO 06N140W. SATELLITE PICTURES INDICATE THAT A WEAK LOW-LEVEL CYCLONIC CIRCULATION HAS FORMED WITHIN THE ITCZ IN THE VICINITY OF 11N128W AND IS DRIFTING SLOWLY WESTWARD. A BURST OF DEEP CONVECTION WITHIN 90 NM OF THE SW QUADRANT IS EVIDENT...WITH THE MAIN CIRCULATION MOSTLY EXPOSED ON THE NE SIDE. CIMSS SHEAR ANALYSES REVEAL MORE THAN 20 KT OF E TO ENE SHEAR OVER THE SYSTEM...WHICH SHOULD PROVE TO BE A STRONG INHIBITING FACTOR FOR FUTURE DEVELOPMENT. PERHAPS THIS IS A REASON WHY NO GLOBAL MODEL IS FORECASTING DEVELOPMENT FROM THIS AREA OVER THE NEXT FEW DAYS. TO THE E...AN ANOMALOUS LOW-LEVEL WESTERLY FLOW REMAINS IN PLACE MOSTLY S OF 20N E OF 120W...AS HAS BEEN THE CASE FOR MOST OF THE LAST WEEK OF AUGUST AND NOW THE FIRST 10 DAYS OF SEPTEMBER. THIS PATTERN SUPPORTS A MONSOON TROUGH-TYPE FEATURE...DISPLACED N OF ITS CLIMATOLOGICAL POSITION...FROM CENTRAL AMERICA NORTHWEST THROUGH MUCH OF SOUTHERN MEXICO TO NEAR TROPICAL DEPRESSION LOWELL. SCATTERED TO LOCALLY NUMEROUS TSTMS ARE OCCURRING WITHIN ABOUT 330 NM OF THE SW COAST OF MEXICO NEAR MANZANILLO THIS MORNING...IN AN AREA WHERE LOW-LEVEL NORTHWESTERLY FLOW IS INTERSECTING SOUTHWEST TO WESTERLY FLOW. MODELS SHOW LITTLE CHANGE TO THE WESTERLY LOW-LEVEL EXCEPT TO CURB IT TO THE WEST AND HIGH PRESSURE OVER THE NE PACIFIC BUILDS INTO THE REGION BETWEEN 110-120W BY EARLY THIS WEEKEND. ELSEWHERE...LONG PERIOD SOUTHWEST SWELL ARRIVING FROM THE SOUTHERN HEMISPHERE CONTINUES TO ENGULF MUCH OF THE TROPICAL EAST PACIFIC WATERS...EXCEPT OVER THE W OF 120W WHERE SOUTHEAST SWELL PREVAILS. MODEL GUIDANCE ALREADY SHOWS WAVE HEIGHTS PEAKING AROUND 7 TO 9 FT OVER THIS ENTIRE REGION TODAY AND THEN SUBSIDING TO 5 TO 8 FT BY FRI. $$ KIMBERLAIN