Recent increase in summertime extreme wave heights in the western North Pacific

Recent increase in summertime extreme wave heights (H10, June–August average of the highest 10% of significant wave heights at each month) in the western North Pacific is found by applying an empirical orthogonal function analysis to H10 derived from 3rd–generation wave model forced by 6‐hourly sea surface wind fields of NCEP‐NCAR reanalysis over the period 1980–2004. The leading principal component of H10 demonstrates that the highest four years of H10 during 1980–2004 occurred in the last 10 years. It is found that the recent increase in H10 corresponds to the recent increase in total duration of intense tropical cyclones (ITC, with central pressure below 980 hPa) in the western North Pacific. Time series of the total duration of ITC reveals that the highest three years of the total duration of ITC during the last three decades occurred in the last 10 years.