An Analysis of the Biases in Traditional Cyclone Frequency Maps

Abstract

The traditional method of estimating cyclone frequency by counting the number of storms passing through latitude-longitude grid cells is known to be biased because it effectively overweights the lower latitudes. Here we show that it is also biased in that it preferentially weights certain storm track directions over others. An analysis of storm tracks affecting a few locations in North America and the North Atlantic shows that these biases can distort the frequency estimates by at least 14%. It is not possible to correct for these biases unless the prevailing storm track direction is measured at each location. Unbiased alternatives are discussed, however, which can be used when better accuracy is required.