Fire in the West Sponsors:

Seasonal forecasts of two-category probabilistic temperature and precipitation anomalies were produced for geographic areas across the United States related to wildland fire management. Forecaster consensus was reached by combining several monthly and seasonal forecasts produced at the International Research Institute for Climate Prediction (IRI), the Scripps Institution of Oceanography Experimental Climate Prediction Center (ECPC), the NOAA/NCEP/NWS Climate Prediction Center (CPC), and the NOAA/CIRES Climate Diagnostics Center (CDC). The process was facilitated in conjunction with a wildfire and climate workshop held on March 5, 2002 organized by the University of Arizona and Desert Research Institute. The primary purpose of the consensus forecast was two-fold; 1) to produce seasonal climate forecasts for geographic areas relevant to wildfire management, and 2) determine whether or not additional probabilistic information could be provided for areas where individual forecasts showed little confidence.

The forecast periods were March-May (MAM) and June-August (JJA) 2002. A combination of dynamical and statistical models from the respective organizations, and forecaster judgment were incorporated in producing the forecasts. Specifically, the IRI contribution was their most current seasonal forecasts based on the CCM3.2, ECHAM4.5, NCEP-MRF9, and NSIPP models and SST predictions (Mason et al. 1999). The ECPC contribution included current monthly forecasts from the Global Spectral Model (GSM, Roads et al. 1999; 2002). The CPC contribution was the current seasonal long-lead outlooks based on a dynamical model, a statistical model, and long-term trend (http://www.cpc.ncep.noaa.gov/products/predictions/90day/). The CDC contribution was based on a newly developed statistical model and analysis for precipitation forecasts in the southwest U.S. (http://www.cdc.noaa.gov/~kew/CO.predictions/FEB.html). These objective forecasts were then combined with forecaster judgment including model forecast skill, temperature versus precipitation correlations and SST prediction opinions. The forecasts were produced via a round-table forum during the workshop. For each forecast, discussion was followed by more or less counting who was in favor of warm/cool, dry/wet, etc., and then determining the highest probabilities for all four forecasters leaning in one direction.

Figs. 1 – 4 show the seasonal U.S. consensus forecasts for MAM temperature, MAM precipitation, JJA temperature and JJA precipitation, respectively. Since only two categories were forecast for, the probabilities simply represent the chance of above or below normal. A 7.5% probability change for the median is roughly the same as a 5% change in tercile probabilities (e.g., 65% is similar to +10% for terciles). Given the current state of art for climate prediction, we equate probabilities of 65% and larger to fairly high confidence.

Since this is the first effort to produce a consensus forecast by combining forecasts from different organizations, skill results cannot be offered at this time. However, the skill has been established for most of the inputs, and it is likely that the consensus forecast skill will be equal to or slightly larger than individual forecasts, depending on the region and the number of “ensemble” members that were in agreement. Skill results related to some of the individual forecasts can be found in (Barnston et al. 2001; Roads et al. 2001; http://www.cdc.noaa.gov/~kew/CO.predictions/FEB.html).

Acknowledgements:

These forecasts were created as part of the Fire in the West 2002 workshop organized by the Climate Assessment for the Southwest (CLIMAS). CLIMAS (a NOAA-funded Regional Integrated Science Assessment) is housed at the University of Arizona, Tucson, Arizona. Other workshop sponsors included the Institute for the Study of Planet Earth (ISPE), University of Arizona, Tucson, Arizona; The Laboratory of Tree-Ring Research, University of Arizona, Tucson, Arizona; The Program for Climate, Fire, and Ecosystem Applications (CEFA), Desert Research Institute, Reno, Nevada; and the National Weather Service Weather Forecast Office, Tucson, Arizona. Dr. Narasimhan Larkin (USDA-Forest Service/PNW/FERA) produced the map graphics during the workshop. ECPC is funded by the NOAA/OGP/CDEP/ARCs program NOAA-NA77RJ0453.

References:

A. G. Barnston, L. Goddard and S. J. Mason, 2001: Verification of IRI's Seasonal Climate Forecasts. Proceedings for the 26th Annual Climate Diagnostics and Prediction Workshop, La Jolla, California, October 22-26, 2001.

Mason et al., 1999: The IRI seasonal climate prediction system and the 1997/98 El Nino event. BAMS, 80, 1953-1873

Roads, J.O., S-C. Chen, M. Kanamitsu, and H. Juang, 1999: Surface Water Characteristics in the NCEP Global Spectral Model and Reanalysis, J. Geophys. Res. 104 (D16) 19307-19327.

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

Roads, J., S-C. Chen, J. Ritchie, 2002: ECPC's March 2002 Forecasts. Experimental Long-Lead Forecasts Bulletin, March 2002, Vol. 10, 6 pp.