Predictability of Tropical Cyclone Intensity Evaluated through 5-year Forecasts with a Convection-permitting Regional-scale Model in the Atlantic Basin

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Wednesday, 5 February 2014: 8:45 AM
Room C201 (The Georgia World Congress Center )
Yunji Zhang, Pennsylvania State University, State College, PA; and Z. Meng, F. Zhang, and Y. Weng

The practical predictability of tropical cyclone (TC) intensity in sense of mean absolute forecast error is explored through convection-permitting hindcasts of all Atlantic storms during the 20082012 hurricane seasons using the Weather Research and Forecast (WRF) model. Averaged over a total of 2190 simulations, the day-1-to-5 performance of these WRF hindcasts is comparable to the two operational regional-scale hurricane prediction models used by the National Hurricane Center (NHC) but is slightly inferior to the NHC official forecasts.

It is found that the prediction accuracy of TC intensity, both at the initialization time and the targeted forecast hours, is strongly correlated with the TC intensity. On average, for both the WRF hindcasts and the NHC official forecasts, stronger intensities lead to larger forecast errors. Intensity changes and initial biases also affect forecast errors similarly. A number of synoptic-scale environmental parameters, such as vertical wind shear, sea surface temperature (SST) and the underlying surface condition (land vs. sea), affect the intensity forecast errors of TCs in part due to their influence on intensity changes, while mesoscale parameters such as moisture and instability have comparably minor effect. The accuracy of the intensity prediction is also found to be sensitive to the translation speed of the TCs. A moderate TC translation speed of 1115 knots (kt) corresponds to the largest intensity errors during forecast lead-times less than 60 hours, while the slowest translation speed (< 7 kt) is associated with the largest errors after the 60-h forecast lead-time.