Limit on the Tropical Cyclone Intensity Forecast Accuracy

This study examines the properties of tropical cyclone (TC) intensity forecast errors and related predictability for the operational Hurricane Weather Research and Forecasting (HWRF) model. Using real-time intensity forecasts during 2012-2016 seasons, two necessary conditions for a limited range of TC intensity predictability are demonstrated, which include 1) the existence of a stationary intensity error saturation limit, and 2) the faster intensity error growth rate for higher intensity during TC rapid intensification. Of further importance is that the intensity error saturation varies in the range of 14-18 kt in different ocean basins, suggesting the dependence of the intensity predictability on large-scale environments. These findings indicate that the current intensity forecast errors is not entirely due to the model deficiencies, but a substantial part of these intensity errors is related to the inherent dynamics of TCs. The limited predictability of TC dynamics prevents us from reducing the absolute intensity errors in the HWRF model below a certain threshold.