5.0 HEFS Examples » 5.1 HEFS vs. Single-value Operational
Let’s return to the standard 10-day forecast time series from the HEFS for the Little River case in Tecumseh, Oklahoma. The overlays show the single-value (deterministic) operational forecast in black, and the observations in green.
Question 1 of 3
What does the operational single-valued forecast show compared to the observations? (Choose all that apply.)
The correct answers are b, d.
The single-valued forecast had an earlier initial rise and more peaks than the observations.
Question 2 of 3
What does the HEFS probabilistic guidance show? (Choose all that apply.)
The correct answers are a, d.
The HEFS probabilistic guidance shows that the observed stage fell within the 10-25% exceedance probability at the time of observed peak. During the period of high flow, the observations were well above the ensemble median, and the probabilistic guidance showed at least a 5% chance of reaching moderate flood stage.
Question 3 of 3
The operational single-valued forecast has higher discharge values than all of the probabilistic guidance at the time of the peak observed discharge. (Choose the best response.)
The correct answer is b.
In this case, the operational single-valued forecast was higher than the observed value throughout the period of high flows through 28 December.
Ensemble Traces issued 26 December 2015
Probabilistic Guidance from the HEFS with Single-valued Forecast and Observations
In the HEFS plot through 28 December, the single-valued forecast was at a greater or equal discharge value than the blue shaded areas. However the single-valued forecast was not greater than all of the probabilistic guidance. Recall that a few ensemble members lie in the unshaded area above the 5% exceedance probability. In the ensemble traces plot, we can see that at least one member peaked at a discharge level that was greater than the single-value forecast.