Variability of storm-forced extreme sea levels along the U.S. West Coast

Hourly tide gauge records along the U.S. West Coast from Southern California to southern Alaska yield meteorologically-forced non-tide residuals (NTR), providing a record of the incidence of storm-forced extreme sea levels. NTR were obtained from tide-removed hourly data bandpass-filtered between periods of 10 days and 2.5 hr, thus focusing on synoptic variability and removing long period steric changes due to El Nin/spl tilde/o and changes in mean sea level. Comparisons were made for winter months (November to March) for stations having record lengths in excess of 50 yr, with the longest record at San Francisco from 1858 onward. The cumulative extreme positive winter NTR levels (above the 98th percentile level, i.e. the top 2%) generally increase from south to north. At individual stations, cumulative extreme winter NTR commonly fall within a relatively consistent range, with no dominant trend observed at any of the stations over the full duration of the record. Winter extremes observed during the great El Nin/spl tilde/os of 1982-83 and 1997-98 are generally not exceptional compared to prior strong El Nin/spl tilde/os. Extreme winter NTR also show relatively pronounced quasi-periodic decadal-scale variability that is similar to that exhibited in the Pacific Decadal Oscillation (PDO), with the pattern of variability apparently reflecting the dominance of El Nin/spl tilde/o/Southern Oscillation (ENSO) related storminess at more southern locations, while La Nin/spl tilde/a conditions tend to have increasing influence moving north.