NCEP 250/500/850 HPa Streamline & Spread Details

The 250, 500 and 850 HPa streamlines shown on this page are taken from the T126
MRF 00Z run only. The two "spread" plots are derived from the ensemble
forecast runs as follows:

1) For the v-comp spread, the mean value of the 17-member ensemble forecast
is calculated at each grid point for the v-component of the wind. The values that
are plotted at each grid point indicate the standard deviation, or spread, of the 17
members around this mean.

2) The spread for the kinetic energy ((u**2 + v**2)/2) is calculated using the same
method as for the v-comp, desribed above.

These plots of the spread help in identifying areas of lesser and greater confidence
in the MRF wind forecasts.