000 AXPZ20 KNHC 030928 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC WED SEP 03 2008 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0915 UTC. ...SPECIAL FEATURE... TROPICAL DEPRESSION KARINA 1002 MB CENTERED NEAR 20.0N 113.7W AT 0900 UTC MOVING W AT 6 KNOTS WITH MAXIMUM SUSTAINED WINDS OF 30 KT GUSTING TO 40 KT. SCATTERED MODERATE ISOLATED STRONG CONVECTION HAS RETURNED TO WITHIN 150 NM IN THE W QUADRANT OF KARINA. HOWEVER CIMSS ANALYSES STILL INDICATE 20 TO 25 KT EASTERLY SHEAR OVER THE SYSTEM. IN ADDITION KARINA IS IN THE PROCESS OF MOVING FROM 28C TO 25-26C SEA SURFACE TEMPERATURES WHICH SHOULD CAUSE ANY CONVECTION WHICH PERSISTS TO DECREASE. THE COMBINATION OF A HIGH SHEAR ENVIRONMENT AND COOLING OCEAN TEMPERATURES SHOULD RESULT IN DISSIPATION WITHIN THE NEXT 24 HOURS. ...ITCZ... ITCZ AXIS ALONG 10N86W TO 11N105W TO 10N120W TO 07N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 120-180 NM N OF AXIS BETWEEN 86W AND 98W. WIDELY SCATTERED MODERATE CONVECTION WITHIN 90-180 NM S OF AXIS BETWEEN 95W AND 111W...AND WITHIN 90 NM EITHER SIDE OF THE AXIS BETWEEN 130W AND 135W. ...DISCUSSION... DEEP TROUGH OF LOW PRESSURE DROVE A STRONG COLD FRONT RATHER FAR S IN THE NE PACIFIC AND THEN INTO THE WESTERN STATES THIS PAST WEEKEND AND LEFT A STRONG SURFACE RIDGE IN ITS WAKE. THE ENHANCED PRESSURE GRADIENT BETWEEN LOW PRESSURE OVER THE SW CONUS AND THE SURFACE RIDGE OVER THE NE PACIFIC BROUGHT ABOUT THE DEVELOPMENT OF NW TO N GALE FORCE WINDS OFFSHORE THE NRN CALIFORNIA COAST WHICH PERSISTS EVEN NOW. A WELL-DEFINED NORTHERLY SWELL TRAIN HAS SINCE PROPAGATED WELL S INTO THE TROPICAL E PACIFIC WATERS...WITH THE WAVE FRONT NOW REACHING A LINE FROM ROUGHLY 22N110W TO 16N140W. SEAS OF 8 TO 11 FT IN LONG PERIOD NW TO N SWELL PREVAIL NW OF THAT LINE E OF 127W WHILE N TO NE LONG PERIOD SWELL LIES W OF 127W. MODEL GUIDANCE INDICATES THAT THE SWELL SHOULD CONTINUE TO SPREAD SOUTHWARD OVER THE BASIN...BUT WAVE HEIGHTS SHOULD BEGIN TO SUBSIDE AS GALES OFFSHORE THE U.S. W COAST ABATE. ELSEWHERE...EARLIER QUIKSCAT DATA SHOWED A BROAD AREA OF S TO SW WINDS OF 20 KT LYING S OF THE ITCZ TO NEAR THE EQUATOR FROM 88W TO 130W. MEANWHILE...LONG PERIOD SW SWELL COMING OUT OF THE SOUTHERN HEMISPHERE CONTINUES TO ARRIVE OVER THE FAR SOUTHERN WATERS AS WELL AS THE MEXICAN AND CENTRAL AMERICAN COASTS. NOAA WAVEWATCH III GUIDANCE SUGGESTS THAT 8 TO 10 FT WAVE HEIGHTS LIE ROUGHLY S OF 12N BETWEEN 90W AND 130W. THE SW SWELL SHOULD GRADUALLY SUBSIDE OVER THE NEXT DAY OR TWO...MODELS SHOW ANOTHER WELL-DEFINED AREA OF LONG PERIOD SW SWELL REACHING THE FAR SOUTHERN WATERS LATE THIS WEEK AND WEEKEND. IN ADDITION TO THE SW SWELL...MODEL GUIDANCE STRENGTHENS LOW PRESSURE NEAR AND JUST OFFSHORE THE S COAST OF MEXICO THE NEXT FEW DAYS...WHICH RESULTS IN A CONTINUATION OF THE ANOMALOUS LOW- LEVEL SW TO W FLOW WHICH HAS DOMINATED MUCH OF THE SOUTHERN HALF OF THE BASIN SINCE LAST WEEK. THE SW TO W FLOW SHOULD BE IN THE 20 KT RANGE. $$ COBB