ECPC's June 2000 Forecasts

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

As previously discussed by Roads et al. (2000a,c), 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. 1999a). 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. 1999, 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 can force a corresponding nonhydrostatic mesoscale spectral model (MSM; Juang 1999) for the Hawaiian Islands (Stevens et al. 1999). 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. Since the global atmospheric model is now forcing an ocean model (Auad et al. 1999), forcings and corresponding output from the ocean model will be presented in later ELLFB issues.

Fig.s 1,2,3,4 show the GSM seasonal anomaly forecast for June-Aug. 2000 along with the corresponding RSM monthly anomaly forecast for June 2000 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 a deleterious effect on the RSM anomalies discussed below. We are currently trying to develop a more suitable RSM climatology for the RSM simulations. Above normal seasonal temperatures (Fig. 1) are expected for most land areas in the Northern Hemisphere, along with the lower maritime temperatures which extend southward to the land regions of the southern hemisphere. Although somewhat lower temperatures occur over the US Southwest in the GSM (The RSM temperature forecast was not available for this month) during the first month, subsequent months return the initial lower temperatures, which may be related to lower than normal soil moisture in this region, to anomalously high seasonal temperatures.

GSM seasonal and RSM monthly precipitation forecasts (Fig. 2) demonstrate some lingering effects of a cold tropical episode, including below normal precipitation in the tropical Eastern Pacific and above normal precipitation in the tropical western Pacific and western Amazon. Over the US, above normal precipitation is expected in the currently dry New England area. However, the Southeast is still forecast to remain dry. Soil moisture (Fig. 3) is generally coincident with the global and US precipitation and temperature anomalies, which reflects the strong influence of precipitation on soil moisture as well as potential feedbacks by the soil moisture on precipitation and temperature. Many potential drought areas in the US southeast, southern Brazil, and central Africa are indicated. The FWI (Fig. 4) is generally coincident with the precipitation and soil moisture over the western Amazon, northern China, and Afghanistan. Over the US, the FWI is relatively high along the Rocky Mountain Front Range and low over the Rocky Mountains and Southwest during June. Again, this RSM anomaly pattern is affected by our current use of our GSM climatology, which we will soon replace with an RSM climatology. Other experimental GSM and RSM forecast fields (wind speed, relative humidity) and additional forecast months)can be found at http://ecpc.ucsd.edu/projects/ellfb/. Other forecast ranges and other regions can be found at http://ecpc.ucsd.edu/m2s/m2s_ECPC_forecasts.html/.

Anderson, B.T., J. O. Roads, S. (C. Chen, and H. (M. Huang, 1999: Regional Modeling of the Low(level Monsoon Winds Over the Gulf of California and Southwest United States: Simulation and Validation, (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.

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, 1996.

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., S. Chen, M. Kanamitsu, H. Juang, Surface water characteristics in NCEP global spectral model reanalysis. J. Geophys. Res., 104, 19307(19327, 1999a.

Roads, J., S. (C. Chen, J. Ritchie, 2000a: ECPC's Weekly to Seasonal U.S. Forecasts of FWI, Soil Moisture, and Precipitation. ELLFB bulletin, Mar. 2000.

Stevens, D. D. Funayama, J. Roads, S. Chen, W. Smith, C. McCord, H. Juang, F. Fujioka, 1999: Experimental short(term weather forecasts for Hawaii. MHPCC application briefs 1999. (Available from MHPCC, Kihei, Maui, HI 96753), 19.