GFSwk12_Precip_Forecast -- GeoTiFF (mm/day) To view the GeoTiff in ArcGIS: Go to "Symbology" Classify the data Exclude the missing value (which is -999.0) GFS week1 (1-7 days) bias corrected total precipitation GFS week2 (8-14 days) bias corrected anomalous precipitation The data resolution is: 0.5x0.5 degree **** More Details about the forecast ************************************** The Global Forecast System (GFS) is a global numerical weather prediction computer model run by NOAA/NCEP/EMC. The forecasts presented here are the GFS Ensemble Forecasts. Bias Corrected Every day the week-1 and week-2 GFS precipitation ensemble forecasts have been corrected with the past N days mean forecast errors, defined as follows: Bias1 = 1/N SUM [ Pf (week1) - Po (week1) ] (1) Bias2 = 1/N SUM [ Pf (week2) - Po (week2) ] (2) where Pf is the NCEP GFS ensemble week-1 and week-2 precipitation forecasts, Po is the observed week-1and week-2 precipitation from CPC daily US and Global Unified Precipitation Analysis. N is number of days (e.g. 30 or 7 days). The choice of N is somewhat subjective. In general, the mean forecast errors calculated from larger N (e.g. 30 days) are more robust than those from the smaller N (e.g. 7 days or 1 day).