MODEL QPF GUIDANCE VERIFICATION BY REGIONS
WARNING: SITE DISABLED -- NO LONGER UPDATING
SITE SUPPORT AND UPDATE PROCESSING TERMINATED JUL 26, 2021
ADDED ECM FOR 24, 48, AND 72 HOURS; TEXT UPDATED DEC 1, 2008
ADDED SREF MEAN, REMOVED ODDS RATIO, POD, & FAR; TEXT UPDATED MAY 5, 2006
GRAPHICS UPDATED WEEKLY AS OF FEB 14, 2005
NEW REGIONS: TEXT AND REGION MAP UPDATED JAN 13, 2004
TEXT UPDATED MAR 19, 2003
This web site compares the performance of the NAM, SREF, and GFS for the prediction
of 24-h accumulations of precipitation ending at 12 UTC. The European Center model (ECM)
performance is included for projection hours 24, 48, and 72. The ECM forecasts are
available to users in the U.S. later than comparable forecasts from NAM, SREF, and GFS.
US has been broken into 14 regions in consideration of approximate uniformity
of climatology and terrain. The verification was done on a 40-km grid.
Graphical displays are generated for each region,
each of six projection times (24, 36, 48, 60, 72, and 84 hours), and each
of two time ranges (beginning one month and three months prior to the present).
There are a total of 156 graphics to look at. A new set of graphics is
generated every week.
Two measures of performance are displayed on each graph as a function
of accumulation threshold. These measures are computed from the following
traditional contingency table of event counts over a multitude of forecasts:
In the following discussion, N=a+b+c+d. The computation of the performances
measures displayed is described below:
b (false alarm)
d (correct rejection)
In the graphs, the bias values are plotted along the axis on the right
side of the plot.
Equitable Threat Score = the number of correct forecasts minus number expected
by chance divided by the same quantity plus the number of erroneous forecasts
= [a - (a+b)(a+c)/N] / [a + b + c - (a+b)(a+c)/N]. This score ranges
from less than 0 to 1; a perfect score is 1.
Bias = the ratio of the total number forecast to the total number observed
= (a+b) / (a+c).