Ensemble prediction systems and forecasts of extreme events
Gregory
Byrd, William Bua, and Timothy C. Spangler
UCAR/COMET
In natural disaster preparedness, the longer the lead time
before an extreme event occurs, the greater the opportunity to mitigate damage
and loss of life. One tool that has become important in assessing the risk of
occurrence for extreme weather events is the ensemble prediction system (EPS),
which uses uncertainty in numerical weather forecasts and the initial conditions
of the atmosphere to make multiple individual forecasts for a forecast. The
subsequent EPS forecast can be used to quantify the probability of an extreme
weather event, based on the percentage of forecasts in the EPS that predict the
event.
To help the forecaster learn how to intelligently use EPSs
in the forecast process, the Co-Operative Program for Meteorological Education
and Training (COMET) has developed several training aids, which will be
reviewed. These may include:
·
A webcast (Introduction to Ensemble
Prediction, found at http://meted.ucar.edu/nwp/pcu1/ensemble_webcast/)
that provides an audiovisual introduction to the scientific concepts and
forecast tools used in ensemble forecasts, along with warm and cold season case
examples.
·
A web-based module (Ensemble
Forecasting Explained, found at http://meted.ucar.edu/nwp/pcu1/ensemble/)
with an introductory section explaining ensemble prediction concepts, and
subsequent sections discussing ensemble forecasts generation, important
statistical concepts, tools used to summarize the ensemble forecast data and
its verification, and finally some case applications.
·
A table or matrix of information on
current ensemble prediction systems available through the U.S. National Centers
for Environmental Prediction (NCEP) that can be found in the EPS matrix (http://meted.ucar.edu/nwp/pcu2/ens_matrix).
We will apply the training information to the forecast of
some extreme events that occurred over the past year, including a land-falling
tropical cyclone and a heavy snow event.