P50 Initial condition perturbation tests within Experimental Regional Ensemble Forecasting (ExREF) system

Jankov, isidora, Cooperative Institute for Research in the Atmoshpere, Tara Jensen, National Center for Atmospheric Research, Ligia Bernardet, Cooperative Institute for Research in Atmospheric Sciences, Jun Du, National Centers for Environmental Prediction, David Novak, Weather Prediction Center, and Zoltan Toth, National Oceanic and Atmospheric Administration

The development of an Ensemble Forecasting System (EFS) at NOAA/ESRL/GSD was initiated for supporting the Hydrometeorological Testbed (HMT) real time forecasts as well as research activities targeting better understanding and improvement of QPF. Since then, the EFS has been modified, tested, evaluated and tuned as a part of collaboration between NOAA/ESRL/GSD, NOAA/EMC, NOAA/WPC and the Developmental Testbed Center (DTC). The latest version of the system is covering North American (NA) area. This NA ensemble, named Experimental Regional Ensemble Forecasting (ExREF) system, in addition to supporting large projects such as HMT, the Hazardous Weather TeseTestbedtbed (HWT), and the WPC Flash Flood and Intense Rainfall Experiment, will serve as a testbed for future generations of operational ensemble forecasting systems. One of the recently implemented features into a parallel version of the ExREF is initial conditions perturbation through dynamic downscaling. The approach preserves coarser-resolution information from global forecasts and complements it with the high-resolution information provided by the output from a regional modeling system. At initial times, limited area models are initialized by the dynamically downscaled global forecasts. This approach is simple and computationally inexpensive, with a great potential to improve precipitation forecast especially during the first few forecast hours (00-06 h), which is crucial for flash-flooding events. After initial testing the approach will be submitted for a more extensive evaluation by WPC forecasters and testing by DTC. Depending on the results, the new initial conditions perturbation approach may be transferred to operations by collaboratively working with EMC colleagues.