Thunderstorms and hail days probabilities in Nevada

A computer program was developed to provide probabilities for selected number of thunderstorm days in a month and in a year. In addition, probabilities for selected number of hail days in a year were determined. Two distribution models were tested in the analysis: (a) Poisson and (b) negative binomial. The program determines which of these two models is appropriate. Furthermore, if the negative binomial mode is selected, tests are conducted to determine whether estimation of the parameters is to be made by the method of moments or by the method of maximum likelihood. A procedure for estimating efficient estimates of the parameters utilizing reiterative process and the curvilinear model is described. Estimates by this procedure compare favorably with those obtained "by eye". The program was applied to five locations in Nevada. Results show that for Nevada, the Poisson distribution fits the monthly thunder-storm days for the months November through April, while the negative binomial fits this variable better from May through October. The negative binomial model also fits the annual thunderstorm days in Nevada. Annual hail days distribution favored the Poisson distribution where the frequency was small. The negative binomial fitted the annual hail days distribution at Ely and Elko. Cumulative probabilities are presented for these variables at the five sites, including Elko, Ely, Las Vegas, Reno, and Winnemucca. Clarence M. Sakamoto. Includes bibliographical references (page 8).