2009 National Hurricane Center Forecast Verification Report by James L. Franklin

Dienstag, 23. März 2010

It was a relatively quiet Atlantic hurricane season, with only 144 official forecasts issued in 2009; only 22 of these forecasts verified at 120 h. The NHC official track forecasts in the Atlantic basin set records for accuracy at 24-72 h in 2009. Official forecast skill was also at record levels at those times. On average, the skill of the official forecasts was very close to that of the TCON/TVCN consensus models, as well as to the best performing of the dynamical models. The GFSI and EMXI exhibited the highest skill, and the GHMI also performed well. For the second year in a row, NGPI and EGRI were the poorer performing major dynamical models. Among the consensus models, FSSE (a corrected consensus model) performed the best overall. The corrected versions of TCON, TVCN, and GUNA, however, did not perform as well as their parent models.

Official intensity errors for the Atlantic basin in 2009 were mostly above the previous 5-yr means. Decay-SHIFOR errors in 2009 were unusually large, indicating the
season’s storms were more difficult to forecast than normal. However, intensity forecast skill was at or just above historical highs. Among the individual intensity guidance models, the LGEM performed best in 2009 (its second year in a row as the top model) and its third consecutive strong showing. The dynamical models GHMI and HWFI performed poorly – so poorly that the ICON consensus could not surpass LGEM. ICON, however, fared as well or better than the corrected consensus FSSE.

There were 268 official forecasts issued in the eastern North Pacific basin in
2008, although only 45 of these verified at 120 h. This level of forecast activity was near average. NHC official track forecast errors set a new record at 12 h. The official forecast skill was very close to the TVCN consensus and the best of the dynamical models. Among the guidance models with sufficient availability, EMXI stood out, with GFNI and HWFI faring least well. There was a large southwestward bias in both the guidance and the official forecast.

For intensity, the official forecast outperformed all the Pacific guidance at 12, 36
and 48 h. Official intensity biases turned sharply positive at 96-120 h, in contrast to the negative long-range biases in 2007-8. The positive bias is partly attributable to the southwestward official track bias. The best model at most forecast times was statistical in nature, with DSHP and LGEM sharing the honors for best model. The four-model intensity consensus ICON performed well....

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