1. Ensemble Prediction in the U.S.

2. NCEP Global Ensemble System Begun in 1993 with the MRF (now GFS) First tried “lagged” ensembles as basis…using runs of various initializations verifying at the same time. For the last ten years have used the “breeding” method to find perturbations to the initial conditions of each ensemble members. Breeding adds random perturbations to an initial state, let them grow, then reduce amplitude down to a small level, lets them grow again, etc. Give an idea of what type of perturbations are growing rapidly in the period BEFORE the forecast. Does not include physics uncertainty. Coarse spatial resolution..only for synoptic features.

3. NCEP Global Ensemble At 00Z: T254L64 high resolution control) out to 7 days, after which this run gets truncated and is run out to 16 days at a T170L42 resolution T62 control that is started with a truncated T170 analysis 10 perturbed forecasts each run at T62 horizontal resolution. The perturbations are from five independent breeding cycle. At 12Z: T254L64 control out to 3 days that gets truncated and run at T170L42 resolution out to 16 days Two pairs of perturbed forecasts based on two independent breeding cycles (four perturbed integrations out to 16 days.

4. Major Types of Ensemble Presentations

7. NCEP Short-Range Ensembles (SREF) Resolution of 32 km Out to 87 h twice a day (09 and 21 UTC initialization) Uses both initial condition uncertainty (breeding) and physics uncertainty. Uses the Eta and Regional Spectral Models and recently the WRF model (21 total members)

8. SREF Current System ModelRes (km) LevelsMembers Cloud PhysicsConvection RSM-SAS 4528Ctl,n,p GFS physics Simple Arak-Schubert RSM-RAS 4528n,pGFS physics Relaxed Arak-Schubert Eta-BMJ 3260Ctl,n,pOp FerrierBetts-Miller-Janjic Eta-SAT 3260n,pOp FerrierBMJ-moist prof Eta-KF 3260Ctl,n,p Op FerrierKain-Fritsch Eta-KFD 3260n,pOp FerrierKain-Fritsch with enhanced detrainment PLUS * NMM-WRF control and 1 pert. Pair * ARW-WRF control and 1 pert. pair