1. ECPC’s Forecast System

The Scripps Experimental Climate Prediction Center (ECPC) currently uses the reanalysis I version (Kalnay et al. 1996) of the National Centers for Environmental Prediction’s (NCEP’s) medium range forecast (MRF) model or global spectral model (GSM; Roads et al. 2001a) to make routine experimental global forecasts. These global forecasts (daily out to 7days and weekly out to 16-weeks) start from the NCEP operational 00UTC global analysis. The GSM then forces a regional spectral model (RSM; Juang and Kanamitsu, 1994; Juang et al. 1997; Chen et al. 1999, Anderson et al. 2000, Roads and Chen 2000; Roads et al. 2002) in order to gain increased spatial resolution (50-25 km resolution) for several selected regions (US, CA, SW, Brazil). At even smaller space (2-km resolution) and time scales (8xdaily to 2 days) either the NCEP analysis or GSM forces a corresponding nonhydrostatic mesoscale spectral model (MSM; Juang, 1997) for the Hawaiian Islands. All atmospheric models are based upon the same physics used in the GSM and can, in principle, be updated as the GSM is updated. Output products from the atmospheric models include a fire weather index (FWI, see Roads et al. 1997) and associated variables such as 2m-temperature, relative humidity and 10m-windspeed as well as precipitation and soil moisture. The global atmospheric model is now forcing an ocean model and corresponding ocean forecasts are discussed in Auad et al. (2002).

2. Forecast Skill Evaluations

Four years worth of forecasts (208 forecasts) have now been used to develop a GSM forecast climatology dependent upon season as well as lag. Both means and standard deviations were derived in order to provide normalized (by the standard deviation) anomalies. As discussed by Roads et al. (2001a,b), Roads and Brenner (2002), Chen et al. (2001), the GSM provides skillful forecasts of temperature, precipitation, soil moisture and a fire weather index at long forecast ranges. Although the greatest skill occurs initially and then decays, monthly and seasonal averages demonstrate significant skill (see Reichler and Roads 2002), which may be comparable to empirical long-range forecast methodologies. A recent evaluation of the corresponding RSM seasonal forecasts indicated similar skill (Roads et al. 2002d).

3. Global seasonal GSM forecasts and US monthly RSM forecasts

Fig.s 1,2,3,4 show the GSM and RSM seasonal forecast normalized anomalies normalized (by GSM or RSM standard deviations) of 2-m surface temperature, precipitation, soil moisture and the FWI for the 2002 Dec., 2003 Jan., Feb. time frame.

Above normal seasonal temperatures (Fig. 1) are now being forecast for the central and northeaster Pacific, Caribbean, Brazil, South Atlantic, South Africa and Austral-Asia regions. Below normal temperatures are being forecast for the North, equatorial and South Atlantic and northwest Pacific. Over the US, the forecast temperatures are close to normal, with slightly above normal temperatures in the West and slightly below temperatures in the Mississippi River Basin.

Above normal seasonal precipitation forecasts (Fig. 2) are indicated for Europe and the Middle East, South Asia, the central equatorial Pacific and the high southern hemisphere latitudes. Below normal precipitation is indicated over Canada, Northeast Brazil, Siberia, and the Indian Ocean. Over the US, forecasts are indicating the US West will be above normal and below precipitation will occur over the Gulf and eastern seaboard.

Seasonal soil moisture (Fig. 3) forecasts are indicating that the eastern Amazon, Russia, South Africa, and Australia will be dry and that wetter than normal regions will occur in the eastern Amazon, Argentina and East Asia. Over the US, above normal soil wetness is forecast over the north central and Great Lakes states, which is not fully consistent with the precipitation, indicating a possible transition during the upcoming season.

The seasonal FWI (Fig. 4) is indicating potential fire danger in Northeast Brazil and Peru, Central Africa and Australia. Below normal fire danger is forecast for Canada, Argentina. Over the US, the South Central region is indicating above normal fire danger, whereas Southern California is indicating less fire danger, presumably due to the increased precipitation and soil moisture being forecast for this region.

References

Anderson, B.T., J. O. Roads, S. -C. Chen, and H-M.H. Juang, 2000: Regional Simulation of the Low-level Monsoon Winds Over the Gulf of California and Southwest United States. JGR-Atmospheres 105 (D14) 17,955-17969.

Auad, G., A. Miller, J. Roads 2002: Ocean Forecasts. JGR (submitted)

Chen, S. -C., J.O. Roads, H. -M. H. Juang, M. Kanamitsu, Global to regional simulation of California's wintertime precipitation. J. Geophys. Res., 104(24), 31517-31532, 1999.

Chen, S-C. J. O. Roads, and M. Wu, 2001: ECPC’s Asia forecasts. Journal of Terrestrial-Atmosphere-Oceanography, 12, 377-400.

Juang, H. -M. H., and M. Kanamitsu, 1994: The NMC nested regional spectral model. Mon. Wea. Rev., 122, 3-26.

Juang, H. -M. H., S. -Y. Hong and M. Kanamitsu, 1997: The NCEP regional spectral model: an update. Bulletin Amer. Meteor. Soc., 78, 2125-2143.

Kalnay, E. et al., 1996: The NMC/NCAR reanalysis project, Bull. Am. Meteor. Soc., 77, 437- 471.

Reichler, T. and J. Roads, 2002: Role of initial and boundary conditions in seasonal predictability. Nonlinear Processes in Geophysics (in press)

Roads, J.O., S. -C. Chen, F. M. Fujioka, H. Juang, and M. Kanamitsu. 1997. Global to Regional Fire Weather Forecasts. Int. Forest Fire News, 33-37.

Roads, J.O. and S-C. Chen, 2000: Surface Water and Energy Budgets in the NCEP Regional Spectral Model. JGR-Atmospheres. 105 (D24) p. 29, 539.

Roads, J.O., S-C. Chen and F. Fujioka, 2001a: ECPC’s Weekly to Seasonal Global Forecasts. Bull. Amer. Meteor. Soc., 82, 639-658.

Roads, J., B. Rockel, E. Raschke, 2001b: Evaluation of ECPC’s Seasonal Forecasts Over the BALTEX Region and Europe. Meteorologische Zeitschrift, 10 (4) p. 283-294.

Roads, J. and S. Brenner, 2002: Global Model Seasonal Forecasts for the Mediterranean Region. Israel Journal of Earth Sciences. 51 (1), 1-16.

Roads, J., S. -C. Chen, J. Ritchie, 2002a: ECPC’s Weekly to Seasonal U.S. Forecasts of FWI, Soil Moisture, and Precipitation. ELLFB bulletin, June. 2002.

Roads, J., S.-C. Chen, M. Kanamitsu, 2002c: US Regional Climate Simulations and Seasonal Forecasts. Journal of Geophysical Research-Atmospheres (in press).

Roads, S. Chen, M. Kanamitsu, 2002d: Experimental US Seasonal Forecasts. (submitted)