Southern Hemisphere Application of the Navy Nested Tropical Cyclone Model,

The Navy Nested Tropical Cyclone model is evaluated for performance on southern hemisphere storms in the Australian region. East of 135 E the model exhibits mean forecast errors of 246, 467 and 694 km at 24, 48 and 72 h, respectively. West of 135 E the mean forecast errors are 214, 511 and 745 km at 24, 48 and 72 h. The NTCM tends to have a poleward directional bias in the predicted tracks. This bias may be attributed to the lack of current data, which causes the analysis scheme to revert to climatological values. The NTCM also did not forecast storm tracks well near the Australia coast, especially in the western cases, presumably due to lack of consideration of landsea effects. In a homogeneous sample comparison with TYAN78, the NTCM performed worse in terms of forecast error at early forecast times and better at late forecast times east of 135 E. West of 135 E, the model performance is generally poorer than the analog scheme at all forecast times. The regression post-processing technique of Peak and Elsberry 1981 when applied to the NTCM forecasts results in a reduction of the eastern region sample forecast errors by as much as 150 km at 72 h. The western region forecast improvement is even greater, such that the regression modified NTCM forecasts are superior to TYAN78 in both test regions. Author