TPC Evaluation

• We endorse the operational implementation of the experimental NAM (NAMEXP). Specific comments- 1) In an example of a rerun of the NAM from last year’s hurricane season, the NAMEXP exhibited less of a tendency for spurious tropical cyclone-like spinup over the Caribbean, which has been a chronic problem with the operational NAM. 2) A limited sample of tropical cyclone (Noel and Olga 2007) track forecasts from the NAMEXP showed mostly a slight degradation in comparison to the operational NAM. However it should be noted that the NAM has historically performed much worse than models such as the GFDL, HWRF, the GFS, etc. for track. 3) The NAMEXP forecasts seem to depict a slightly faster and more accurate progression of frontal systems in the Gulf of Mexico region. 4) NAMEXP appears to make slightly more realistic forecasts of gap wind events, in particular Gulf of Tehuantepec gale events. Forecast maximum winds are slightly higher that the operational run of the NAM and closer to the observed winds.