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JUNE 2005

ANNUAL SUMMARY

1773

TABLE 8. A homogeneous set of official and SHIFOR average intensity forecast errors in the Atlantic basin for the 2003 season for all tropical cyclones, including depressions. Ten-year averages for the period 19932002 are also given for the 12- through 72-h forecasts.

Forecast period (h)

12

24

2003 official error (kt) 2003 SHIFOR error (kt) No. of cases 19932002 official error (kt) No. of cases 2003 official error relative to 19932002 official error (%) 2003 official error relative to 2003 SHIFOR error (%)

5.2 6.9 362 6.2 2970 16% 25%

7.9 10.9 327 9.8 2711 19% 28%

36

9.5 14.5 291 12.6 2465 25% 3 4 %

48

11.6 17.3 256 15.2 2214

  • 24%

  • 33%

72

14.8 20.6 197 18.9 1818 22%

  • 28%

17.0

20.6

21.9

24.0

156

125

96

120

  • 22%

  • 14%

cast errors since 1961, for the 24-, 48-, and 72-h fore- casts. Linear trend lines are also plotted. Depressions are not included in this dataset, as it was not possible to obtain depression forecasts from the early part of the period. It is seen that the 2003 official track forecast errors are the smallest of record at all forecast periods. It is also noteworthy that the 2003 official 120-h track error of 223 n mi is about the same magnitude as 48-h errors from the early 1980s.

Table 8 lists the average Atlantic basin official inten- sity forecast errors for 2003, along with the average errors for the previous 10 yr. Official intensity errors are 16% to 25% smaller than the previous 10-yr averages. Table 8 also lists the average errors for the no skillStatistical Hurricane Intensity Forecast (SHIFOR) climatology and persistence model (Jarvinen and Neumann 1979). Average official errors are from 14% to 33% smaller than their corresponding SHIFOR errors.

Trends of intensity forecast errors have not been as large as those of track errors. There have been modest improvements of the 24- and 48-h intensity forecasts, but the 72-h official intensity errors have decreased very little. While global models have made dramatic advances in tropical cyclone track forecasting, these models are not yet resolving the inner-core structure, which plays such an important role in the intensification process. The current state-of-the-art operational inten-

sity forecast guidance is the statistical/dynamical Statis- tical Hurricane Intensity Prediction Scheme (SHIPS) model (DeMaria and Kaplan 1999).

Acknowledgments. Stephen R. Baig of the Tropical Prediction Center prepared the Fig. 1 season track chart.

REFERENCES

Aberson, S. D., 1998: Five-day tropical cyclone track forecasts in the North Atlantic basin. Wea. Forecasting, 13, 10051015. DeMaria, M., and J. Kaplan, 1999: An updated Statistical Hurri- cane Intensity Prediction Scheme (SHIPS) for the Atlantic and Eastern North Pacific Basins. Wea. Forecasting, 14, 326337. Franklin, J. L., L. A. Avila, J. L. Beven, M. B. Lawrence, R. J. Pasch, and S. R. Stewart, 2001: Atlantic hurricane season of

    • 2000.

      Mon. Wea. Rev., 129, 30373056.

  • ——

    , M. L. Black, and K. Valde, 2003a: GPS dropwindsonde wind profiles in hurricanes and their operational implications. Wea. Forecasting, 18, 3244.

  • ——

    , C. J. McAdie, and M. B. Lawrence, 2003b: Trends in track forecasting for tropical cyclones threatening the United States, 19702001. Bull. Amer. Meteor. Soc., 84, 11971203.

Hart, R. E., 2003: A cyclone phase space derived from thermal wind and thermal asymmetry. Mon. Wea. Rev., 131, 585616. Jarvinen, B. R., and C. J. Neumann, 1979: Statistical forecasts of tropical cyclone intensity for the North Atlantic basin. NOAA Tech. Memo. NWS NHC-10, 22 pp. Simpson, R. H., 1974: The hurricane disaster potential scale. Weatherwise, 27, 169186.

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