1. Brian J. Etherton Developmental Testbed Center Survey and summary of ensemble systems 21 November 2011

2. HFIP Regional Ensemble Team As alluded to in talk by Carolyn Reynolds, HFIP Regional Ensemble, formed by consensus, to be put into real-time (stream 1.5) for 2012. To develop consensus, bi-weekly conference calls have been held during the past 2 months, with eight presentations on ensemble systems. Most presentations from these calls also featured this morning Collection of presentations to form foundation of plan for ensemble system design

3. DA Accurate estimate of the state of a system Estimate of error variance - GSI does not provide this Ensemble Dynamically conditioned forecast error covariance Initial error variance reflecting analysis error variance Regional DA & Ensemble systems fully consistent with global DA / Ensemble Functions/Requirements for DA/Ensemble Hybrid System

4. Initial Perturbations Most ensemble systems presented earlier account for uncertainty in initial conditions, with differing approaches EnKF Cycling of Perturbations Vortex Uncertainty Consideration of growth rate of initial perturbations? Some ensemble systems have moving nests, and thus, each ensemble member may have the nest in a different location, and these differences can impact covariance information Default to coarser nest Make inner nest fixed, larger area

5. Model Perturbations Some, but not all, ensemble systems presented earlier include a method for incorporating model error into the ensemble Convective parameterization Cloud Microphysics (parameter and scheme) Aerosols/radiation Boundary layer Since not all ensembles include model error, is it not as important as initial condition error? Number of ensemble members (different for DA than for forecast? can HWRF/EMC do this?)

6. Ensemble metrics Want to improved predictability of… Rapid Intensification? Size? Intensity? Track? Will we investigate the error statistics from the ensemble... Innovations as a means of assessment?

7. Summary of the Summary For the HWRF regional ensemble – must work towards: Domain (moving inner nests used for DA? Just outer?) Ens Initial perturbations (the flow, the vortex) Ens Model perturbations (physics schemes, physics parameters) As applied to the GSI-Hybrid, additional issues: Observations (the more the better: radar, TCvitals, but how?) GSI itself (localization, balances) Maintain operational needs while allowing for research testing and evaluation – modularity and flexibility Robustness for operations Flexibility for research

8. Next Steps Conclude introductory talks (Mon Dec 12): Zhan Zhang, EMC Altug Askoy, AOML Resources for testing and evaluation (FTEs and CPUs) Reach consensus on ensemble system For DA, DTC will start with ESRL version of GSI-Hybrid for HWRF For the ensemble, a few more questions to be answered