Workshop on Indices and Indicators for Climate Extremes, Asheville, NC, USA, 3-6 June 1997 - Breakout Group A: Storms

The Working Group on Storms considered tropical cyclones, extratropical cyc lones, thunderstorms and their associated winds and effects other than on t emperatures and precipitation (which are dealt with by the other working gr oups) to be in their purview. Changes in observing systems and distribution of observers and people impacted by these phenomena confound trend analysi s. In light of the difficulty of assembling homogeneous time series of smal l-scale phenomena such as thunderstorms, tornadoes and hail, and also the p roblems in wind measurements, the working group recommends that indices of wind be developed by taking advantage of long surface (or sea-level) pressu re measurements and analyses. Because wind is a vector, two pairs of readin gs that are orthogonal are desirable. Instantaneous values over about 1000 km scales are desirable to generate statistics relevant to wind extremes. R ecommendations are given on how the data might profitably be processed. Sev eral other recommendations are made concerning data acquisition and process ing, some of which apply to reanalysis of past data and some apply to futur e processing of data. Various "extremes indices" are also suggested.