The Impact of the MJO on NHC Tropical Cyclone Genesis Forecasts

The National Hurricane Center has been making probabilistic 2-day tropical cyclone genesis forecasts for the Atlantic and eastern Pacific basins since 2007 and probabilistic 5-day genesis forecasts since 2009. While these forecasts have generally been well calibrated over the course of a year, significant variability exists in these predictions, with periods of high and low skill noted compared to model guidance. It has been speculated at NHC that the forecast errors are linked to the MJO or other intraseasonal oscillations, but no research has shown whether this type of large-scale variability explains some of the forecast successes and failures. This study examines the reliability and bias of individual NHC disturbance forecasts, in terms of raw probabilities and lead time before formation, and compares them to the phase of the MJO.