NWS Gridded Forecasts

I have been trying to understand better the gridded forecasts that are available from the NWS (millions of grid point forecasts updated every few hours). These forecasts are easily accessed from the Forecast Office websites under the graphical forecast links. The grid point forecasts cover seven days at 1-hour time intervals. The NWS contracts with esri to provide the graphics for the mind-boggling set of products being generated (i.e., environmental system research institute of Redlands, California).

Shown above is the current digital forecast for high temperatures today across our region.

Another graphic (above) shows the gridded digital forecasts for wind gusts valid at 2:00 pm MST tomorrow (Thursday, April 19th). The display below shows the grid point forecast extracted from the massive data base by clicking on a point location (the interactive forecast map provided on NWS web pages). The wind forecast is for San Simon, Arizona - a location where I-10 in eastern Cochise County is frequently closed during blowing dust situations.

How accurate are these deterministic, point forecasts out through 7-days? Good question, and my experience watching them leads to my subjective appraisal - not very good, especially at longer time periods - but sometimes distressingly bad at only a few hours. When I tried to access verification data for the gridded forecasts, I found that that NWS link is restricted for only visitors having a noaa.gov email - so no luck there.

My digging has been stimulated by a question from Jack D, currently located in southern Illinois. Simply put his question was: Why are the NWS point forecasts so bizarre?

More on this issue in next post.