The Experimental Regional Ensemble Forecast (ExREF) System
August 9, 2013
An updated and state-of-the-art regional ensemble forecast system suite has been constructed by NOAA/ESRL Global Systems Division to support the mission and activities of HMT to research high-impact precipitation events and weather conditions that can lead to flooding. The Experimental Regional Ensemble Forecast (ExREF) System not only serves as a tool for researchers to improve existing operational models but also provides high-temporal and spatial experimental guidance to operational forecasters. Through forecast evaluation and comparison against existing operational models, the HMT numerical weather prediction (NWP) suite has the potential to significantly improve quantitative precipitation forecasts (QPF).
The ExREF was tested over the 2012-2013 cool season along the west coast of the United States (HMT-West) and will now be employed over the southeast (HMT-SE). It uses release v3.4.1 of the Weather Research and Forecasting (WRF) model and the Advanced Research WRF (ARW) dynamic core. This North American ensemble has eight members with 9-km grid spacing, initialized four times a day, and run out to 84 h. A variety of forecast fields, including QPF, are sent to the NWS West Coast Weather Forecast Offices. The ensemble uses a variety of initial and boundary conditions created using the Local Analysis and Prediction System (LAPS) and components from the Global Forecasting System (GFS) and its ensemble. Additionally, a diversity of physical parameterizations is used to increase ensemble spread and to account for the uncertainty in forecasting extreme precipitation events.
In addition to providing numerical guidance for HMT, ExREF will be used by the NOAA Weather Prediction Center (WPC) during the Flash Flood and Intense Rainfall Experiment. Moreover, new ensemble methodologies employed in ExREF are being tested by the Developmental Testbed Center (DTC) for possible inclusion in the NOAA operational Short-Range Ensemble Forecast (SREF) system.
Contact: Ligia Bernardet
