The High Resolution Ensemble Forecast (HREF) system: Applications and
Performance for Forecasting Convective Storms
Abstract
In November 2017, the High Resolution Ensemble Forecast version 2
(HREFv2) system was implemented by the U.S. National Oceanic and
Atmospheric Administration (NOAA). The HREFv2 is NCEP’s first
operational convection-allowing model (CAM) ensemble and runs twice
daily at ~3-km horizontal grid spacing. Coinciding with
the operationalization of the HREFv2, the NOAA National Weather
Service’s Storm Prediction Center (SPC) launched its HREF Ensemble
Viewer (https://www.spc.noaa.gov/exper/href), a public web display for
real-time HREF data. In addition to products traditionally used in
operational forecasting, the HREF Ensemble Viewer also employs
post-processing and visualization techniques which leverage the
convective structures explicitly modeled in CAM ensembles. This
presentation describes and illustrates products from the SPC viewer
unique to CAM ensembles which are targeted at forecasting convective
storm coverage, intensity, and evolution. A key aspect of HREF’s
ensemble design is membership diversity with respect to model cores and
parameterization schemes, in conjunction with a time-lagging approach.
Verification is performed on ensemble fields related to explicitly
modeled convection for various modified configurations of the HREF
membership, illustrating how each dimension of membership diversity
contributes to the system’s skill in forecasting convective evolution.
These results help to illuminate potential tradeoffs entailed in
configuring future HREF iterations beyond version 2 as CAMs using new
dynamical cores and parameterization schemes become available.