Accuracy of NHC Track and Intensity Forecasts for Tropical Disturbances and Weak Tropical Cyclones

During the 2011 Atlantic and eastern North Pacific Hurricane Season, the National Hurricane Center conducted an experiment to determine the feasibility of issuing deterministic track and intensity forecasts for systems that were not yet tropical cyclones. NHC forecasters produced 5-day track and intensity forecasts for tropical disturbances that were assessed to have a high chance (>50%) of formation during the following 48 h. This study will provide a brief assessment of the NHC experimental disturbance forecasts along with a detailed look at the accuracy of recent NHC forecasts of weak tropical cyclones. A comparison of the rate of improvement of forecasts for hurricanes versus weak tropical cyclones will also be shown. The study will conclude by examining the relationship between the accuracy of the first few track and intensity forecasts of a tropical cyclone versus the overall forecast errors for that system.