MRF ENSEMBLES FOR DAYS 3 THROUGH
VALID Mar 31 - Apr 7, 2000.
The ensemble mean provides the first order advantage
of ensemble forecasting, i.e., a simple consensus
of a large number of forecasts. Even greater benefits
accrue through the use of the ensembles to assess
confidence, or uncertainty, in the forecast. The spread
provides the most direct measure of the likely skill,
and therefore the confidence, of the forecast.
The spread is the standard deviation among the ensemble
members, in units of meters. It varies both regionally
and seasonally, much like the actual standard deviation
of the height field. So, we expect high values in
high latitudes and in the "centers of action", low
values in low latitudes and moderate values in other
locations. A standardized version, i.e. the spread
as described above, divided by the climatological
standard deviation of the height field appropriate
to the date, is under development for the 6-10 day
and week 2 average forecast periods. According to
Whitaker, et al, 1997 (submitted to Monthly Weather
Review), spread is useful as a predictor of skill
when the spread is either very low (skill is likely
to be high) or very high (skill is likely to be low).
Note that the spaghetti diagrams are daily out to
day 7, then spaghetti maps for the five day mean covering
MRF forecast days 6-10 and the seven day mean over
MRF forecast days 8- 14 are provided.
The MRF based spaghetti maps were not available for
The updated maps were not available for this forecast.