Verification of Gridded Morning Temperatures at NWS Miami, FL

Grid-based comparisons of official NWS forecasts with numerical model guidance and objective analyses of observed weather can enable forecasters to assess in real time the accuracy of their forecasts. This paper describes a technique developed to compare forecasts from the NWS National Digital Forecast Database with guidance from the National Digital Guidance Database and analyses from the Real Time Mesoscale Analysis. The parameter used was the 1200 UTC (morning) temperature forecast, and the difference grids were processed with a Geographical Information System. Gridded departures from the climatological normal temperature were also generated.

Graphical examples will be shown at a regional scale (the NWS Southern Region) and at a local scale (the State of Florida), together with the results of additional detailed statistical comparisons. The method allows forecasters to identify forecast or model errors and, through the use of an archive of the difference grids, trends in forecast or model errors over the past week, month, and/or season. With this information readily available in graphical format, forecasters and researchers can easily recognize model or forecast biases, with the ultimate goal being more accurate forecasts.