A Pressure-Based Reanalysis of Historical Western Pacific Typhoons

Intensity estimates of western Pacific typhoons from 1950 to 1987 are investigated. Aircraft reconnaissance into typhoons during the time period was poorly suited, often relying on direct observation of the ocean surface to measure maximum surface wind speed. This technique was unreliable due to uncalibrated estimation techniques and lack of visibility. Aircraft reconnaissance was much better equipped to make direct dropsonde measurements of minimum central pressure, which could then be used to estimate the wind speed using a wind–pressure relationship (WPR). It is hypothesized that these central pressure measurements were more reliable and accurate than observed surface wind speed. This hypothesis was tested through investigation of aircraft flight records and typhoon reports directly from the Joint Typhoon Warning Center, the main U.S. entity in the western Pacific. A new pressure-based wind record was created using the WPR developed by Knaff and Zehr (2007). While other WPRs existed throughout the time period in question and were used operationally to produce intensity estimates of western Pacific typhoons, more extensive studies such as the above mentioned have been shown to produce superior WPRs. The current and new intensity records are compared. It is recommended that past studies on temporal trends in western Pacific typhoon intensity are reexamined using the updated intensity record.