contributed by J. Roads, S. Chen, J. Ritchie

As previously discussed by Roads et al. (2001a), 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. 1999). These global forecasts (4xdaily-7 days and weekly to 12-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) in order to gain increased spatial resolution (50-25 km resolution) at shorter time scales (4xdaily-7 days and weekly to 4 weeks) 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 (Auad et al. 2001) and corresponding ocean forecasts are shown in Auad et al. (2000).

2 years worth of forecasts (104 forecasts) have been used to develop a GSM forecast climatology dependent upon season as well as lag. As discussed by Roads et al. (2001b,c, d) and 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 toward zero, daily, weekly or monthly forecast skill does not ever reach zero and forecasts averaged into monthly and seasonal averages demonstrate significant skill (see Reichler et al. 2001), which may be comparable to empirical long-range forecast methodologies. Similar evaluation efforts are underway for the regional forecasts, which currently use the GSM to start the forecasts.

Figs 1,2,3,4 show the GSM and RSM seasonal anomaly forecasts for 09/2001-12/2001 of 2-m surface temperature, precipitation, soil moisture and the FWI. It should be noted that both the GSM and the RSM use the same GSM climatology to calculate the anomalies, which may have an effect on the RSM anomalies discussed below. We are still trying to develop a more suitable RSM climatology for the RSM simulations.

Above normal seasonal temperatures (Fig. 1) are being forecast for most areas in the Northern Hemisphere. Europe, Northwest Canada and parts of the Sahel are exceptions. Lower temperatures are forecast over South America, Australia and most of the Southern Hemisphere.

GSM seasonal precipitation forecasts (Fig. 2) indicate potentially above normal precipitation in the eastern Tropical Pacific, and Atlantic, and Indian Ocean. Above normal precipitation is also being forecast over the US Gulf Coastal waters, the east Asian coastal waters. Potential dry regions include the east coast of Central America and the adjacent Caribbean, the east coastal waters of Africa. The US RSM forecast indicates wet conditions for the eastern half of the nation, with especially wet conditions near the Gulf Coast.

Soil moisture (Fig. 3) forecasts are somewhat coincident with the global and US precipitation predictions, which reflects the influence of precipitation on soil moisture as well as potential feedbacks by the soil moisture on precipitation and temperature. Dry areas are being forecast for the western US, parts of Brazil, South Africa, India and Russia. However, the dryness over Northeastern China seems to be associated with the high temperature over this area. RSM forecasts indicate wet regions in the South and Great Lakes regions.

The seasonal FWI (Fig. 4) is forecast to be above normal in central Russia, Middle East, Sahel, and the US West. Above normal FWI is now being forecast over parts of the West, especially Nevada, Idaho, Montana during June, This dryness extends to California and Oregon during the subsequent summer season.

Fig. 1 Temperature (C) 09/2001-12/2001 anomalies: (upper) GSM forecast; (lower) RSM forecast.

Fig. 2 Precipitation (mm/day) 09/2001-12/2001 anomalies: (upper) GSM forecast; (lower) RSM forecast.

Fig. 3 Soil Moisture (mm) 09/2001-12/2001 anomalies: (upper) GSM forecast; (lower) RSM forecast.

Fig. 4 FWI 09/2001-12/2001 anomalies: (upper) GSM forecast; (lower) RSM forecast.