Environmental Modeling Center (EMC)

Short-Range Ensemble Forecasting (SREF) Project

OBJECTIVE: Develop a multi-regional model, short-range (0-3 days)
ensemble prediction system to provide operationally relevant and useful
guidance on the probability distribution of weather elements or events,
especially for quantitative precipitation forecasts (QPFs).

IMMEDIATE GOAL: Commence routine production and evaluation of a
regional model based ensemble system and product suite (SREF-I) in April
2000. The initial system consists of: (1) Eta plus RSM multi-model,
(2) 10 members, (3) 48km horizontal resolution, (4) Eta North America
domain with grib output on Grid 212 (40km), (5) run twice per day (09z
and 21z) to 63hr and output available every 3h, (6) regional bred initial state
perturbations (note: SREF-I has no perturbations on model physics). The
product suite contains: (1) ensemble mean and spread charts, (2) spaghetti
charts, (3) probability charts, (4) meteograms (to be done), and (5) clustering
(to be done).

SREF STATUS MILESTONES: (1) conduct pilot studies (10/96-3/98),
(2) participate in Storm And Mesoscale Ensemble eXperiment (SAMEX)
(3/98-11/98), (3) system modification and code conversion to IBM SP
(1999-Mar. 2000), (4) routine runs and systematic evaluation (from April 2000),
(5) the SREF system has been tested, modified and introduced into NCEP's
production suite as Real-Time Testing and Evaluation (RTTE) as well as
basic SREF products were developed and displayed on the SREF web site
to be used by forecasters (04/00 -- 05/01).

SOME ISSUES: (1) perturbation strategies (both initial conditions and model),
(2) model configurations/tradeoffs (resolution, ensemble size, domain etc),
(3) product development, (4) validation procedures, (5) data and product
dissemination, (6) education and training