THE FINLEY AFFAIR - A SIGNAL EVENT IN THE HISTORY OF FORECAST VERIFICATION

In 1884 a paper by J. P. Finley appeared in the American Meteorologica l Journal describing the results of an experimental tornado forecastin g program in the central and eastern United States. Finley's paper rep orted ''percentages of verifications'' exceeding 95%, where this index of performance was defined as the percentage of correct tornado/no-to rnado forecasts. Within six months, three papers had appeared that ide ntified deficiencies in Finley's method of verification and/or propose d alternative measures of forecasting performance in the context of th is 2 X 2 verification problem. During the period from 1885 to 1893, se veral other authors in the United States and Europe, in most cases sti mulated either by Finley's paper or by the three early responses, made noteworthy contributions to methods-oriented and practices-oriented d iscussions of issues related to forecast verification in general and v erification of tornado forecasts in particular. The burst of verificat ion-related activities during the period 1884-1893 is referred to here as the ''Finley affair.'' It marked the beginning of substantive conc eptual and methodological developments and discussions in the importan t subdiscipline of forecast verification. This paper describes the eve nts that constitute the Finley affair in some detail and attempts to p lace this affair in proper historical context from the perspective of the mid-1990s. Whatever their individual strengths and weaknesses, the measures introduced during the period from 1884 to 1893 have withstoo d important tests of time-for example, these measures have been redisc overed on one or more occasions and they are still widely used today ( generally under names assigned since 1900). Moreover, many of the issu es vis-g-vis forecast verification that were first raised during the F inley affair remain issues of considerable importance more than 100 ye ars later.