Statistical Post-Processing of the Navy Nested Tropical Cyclone Model and the Operational Tropical Cyclone Model.
Final rept. Oct 80-Sep 81,
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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A statistical technique proposed by Elsberry and Frill 1980 for adjusting dynamical tropical cyclone motion forecasts is extended to the Two-Way Interactive Nested Tropical Cyclone Model NTCM and the operational One-Way Interactive Tropical Cyclone Model TCMO. The technique utilizes linear regression equations to reduce systemic errors. Backward extrapolation positions are presented as a less expensive, but inferior, alternative to the backward integration positions required by the original technique. A scheme is developed for applying the technique in storm-motion coordinates as well as zonal-meridional coordinates. Tests with 186 NTCM cases indicate moderate improvement in forecast errors by the zonal-meridional regression technique, and slight improvement by the storm-coordinate scheme. In TCMO tests with 212 cases, the zonal-meridional regression equations reduced the forecast errors, but the storm-coordinate equations did not. The technique failed to improve forecast errors in independent tests with NTCM 1981 data, presumably due to differences in error biases, which indicates a need for a larger sample size. Alternatively backward integration positions may be necessary to achieve consistent improvements from this statistical technique. The technique was able to improve 60h-72h forecast errors in TCMO 1981 cases. Author