2016 winter seasonal climate forecasts over the western US Background. My graduate class (Stochastic Hydrology) is doing a final group project to forecast 2016 winter precipitation, temperature and snow water equivalence (SWE) at 10 sites in the western US. Specifically, (i) monthly total precipitation for January, February, March, and April; (ii) monthly average daily minimum and maximum air temperature for the same months; (iii) SWE for 10 snow course stations on April 1, They have been given the historical records for the above stations (which are shown in the next slide and listed in the table on slide 3.) They can use any forecast technique they wish. I assume some will use empirical statistical approaches, some will use NMME seasonal forecasts, some may use analogue years, etc. They must describe what approach they have used. Forecasts must be submitted by COB January 8, At Jin Huang’s suggestion, I may use CPC’s ‘official outlook’ as the benchmark forecast.

My proposal to the NMME Working Group and CPO Drought Task Force Make this effort into a community forecasting activity. Given the strong El Nino this year, how well can we forecast western US winter 2016 hydroclimate? If people accept to participate, then they will be included in a group paper discussing the forecasts and their skill with all the participants as co-authors. Marty Hoerling suggested that the DTF also may be interested in forecasting the area under drought. I suggest that we do this as follows: We will define a ‘drought’ as a forecast that is below the model’s 20 th climatological percentile for each grid and month for the monthly total precipitation; and above the model’s 80 th climatological percentile for each grid and month for the monthly average of the daily Tmin and Tmax. So a specific grid will be “in drought” or not (ditto for a ‘warm event’). We will compute the same using ½ degree gridded monthly data sets and estimate the 20 th (80 th ) percentiles. A Brier score will then be computed. This analysis will also be included in the paper. Again, forecasts due January 8, 2016 and forecasts for the same months as for the station forecasts.

Action Items if interested 1. me at at: if you want to participate with the subject line: “US winter 2016 seasonal 2.We will respond with the path to the station data. 3.Forecasts due January 8, 2016 using a form we will send to each group.

Selected Stations (pairs of precip, temperature and snow course sites)

Pair Prec/TempSnow water equivalent (SWE) Station IDLatLonStart dateEnd date Missing ratio 1 Station nameLatLonStart dateEnd date Missing ratio %TunnelAvenue_SC % %BentonSpring_SC % %PikeCreek_ST % %BlueMountainSpring_ST % %AnnieSprings_ST % %CssLab_ST % %BigBend_ST % %TimpanogosDivide_ST % %PANTHERMEADOW % %WebsterFlat_ST % Note 1.Missing ratio is calculated only for precipitation (Tmax and Tmin have similar missing ratio as Prec) 2.Missing ratio is calculated based on all the months (Jan-Jun) Site information

The.zip file contains the following: list.10.stns.PrecTemp.info –Information (lat, lon, station ID) for precipitation and temperature list.10.stns.SWE.info –Information (lat, lon, station name) for snow water equivalence (SWE) 10stns_PrecTemp: –This folder has 10 sites for precipitation and temperature –Each file contains: precipitation (col 4), tmax in C (col 5), tmin in C (col 6) –Data format is ASCII –Missing value is indicated as stns_SWE: –This folder has 10 sites for SWE –Each SWE site has 106 rows (years) and 6 columns (Jan-Jun) –Data format is ASCII –Missing value is indicated as Data description