Applying the National Weather Service Hydrologic Ensemble Forecast Service in Soil Moisture Forecasting across the Arkansas-Red River Basin.

Applying the National Weather Service Hydrologic Ensemble Forecast Service in Soil Moisture Forecasting across the Arkansas-Red River Basin

by

Eric Jones and Lee Crowley

NOAA/National Weather Service

Arkansas-Red Basin River Forecast Center

The National Weather Service (NWS) River Forecast Centers (RFC) have been using their Hydrologic Ensemble Forecast Service (HEFS) to predict streamflow forecasts since 2012. The HEFS system employs RFC forecasted temperatures and rainfall, Global Ensemble Forecast System (GEFS) temperature and rainfall, and Climate Forecast System temperature and rainfall as inputs. These inputs are bias adjusted, downscaled, and assigned spread probabilities for use in the RFC Community Hydrologic Prediction System (CHPS) and subsequent hydrologic models.

The Arkansas-Red River Forecast Center (ABRFC) has taken byproducts from HEFS and used it to forecast basin soil moisture forecasts for its area. The ABRFC also issues Ensemble Streamflow Prediction (ESP) based on climatological forcings. Results were observed from soil moisture states from the CHPS hydrologic model for both ESP and HEFS runs. The HEFS soil moisture state forecasts are then compared to the historical ESP soil moisture states runs to provide a magnitude on how much wetter or dryer soil moisture should be versus climatology in the lower and upper soil depth column. These forecast are provided at monthly and seasonal intervals.

Verification has also been performed on these forecasts. Retrospective forecasts were run for a period from 1985-2010. These forecasts were then compared to simulated soil moisture states during the same time period. Results of these validation hindcasts have shown skill in soil moisture forecasts in the monthly and seasonal timeframe.