Southern hemisphere tropical cyclone intensity forecast methods used at the Joint Typhoon Warning Center, Part I: control forecasts based on climatology and persistence

Abstract

The development of a simple statistical tropical cyclone (TC) intensity forecast model is described. The primary purpose of this model, called southern hemisphere five-day statistical typhoon intensity forecast scheme (SH ST5D), is to provide a skill/no-skill control forecast for verifying other TC intensity forecasts. However, it also provides useful and always-available forecasts of TC intensity in the southern hemisphere. The model is created by fitting an optimal combination of factors related to climatology and persistence (or CLIPER) using multiple linear regression. These CLIPER factors are determined from the best track tropical cyclone dataset produced by the United States of America’s Joint Typhoon Warning Center (JTWC) in the years 1980-2002. In 2004 the SH ST5D model became part of the operational suite of tropical cyclone intensity guidance run at JTWC. The forecasts from the model since that time have outperformed both climatology (i.e. a constant 65 knots or 33 ms -1 forecast) and the persistence of initial conditions in a statistically significant manner in independent testing during 2004-2007. This documentation is provided to promote the use of this model’s output and provide adequate background for the development of similar models.