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Process - Peak forecasts are produced using the Ensemble Streamflow Prediction (ESP) forecast technique. ESP combines current model states for snow, soil moisture, streamflow, and reservoir conditions with historic pairs of observed temperature and precipitation since 1981, to generate future hydrologic traces. For each ensemble member (trace), the maximum instantaneous discharge across the future period 4-month period is used to construct the peak flow distribution. Predicted stages use the current rating curve. Peakflow predictions on this page use daily statistics and are limited to four months into the future. |
Table 1: Peakflow Exceedance. This table summarizes all ensembles produced by the ESP procedure. Exceedance probability is the chance of a stage and/or discharge being exceeded in the next four months. Probable Date of Peak is the most likely date of occurrence for a given exceedance probability. Pink shading indicates forecast peaks expected to exceed flood stage. In this table, the Stage and Discharge values for a given probability do not directly correspond to the Probable Date of Peak for the same probability. The magnitude of the peak for a given exceedance probability and the timing of the peak at the same exceedance probability are independent.  |
Plot 1: Peakflow Forecasts. This plot displays ranked peaks from individual ensembles to determine the probability of flows exceeding a certain stage. The chances for exceeding minor flood stage can be determined by locating the intersection of the ranked peaks and the plotted flood threshold (where available) along the x-axis.  |
Plot 2: Comparison of Historical Annual Peaks to RONI (Relative Oceanic Nino Index). RONI is used by NOAA to make official ENSO phase classifications (El Nino and La Nina). Select the desired three-month ENSO period to the right of the plot.  |
Plot 3: Probability of Historical Annual Peaks. This product ranks historical observed annual peaks and plots them against their exceedance probability to show how often annual peaks exceed flood stage. Note that annual peaks do not represent all flood events, as a river can reach flood stage multiple times a year.  |
Plot 4:
Historical Annual Peaks. This plot shows all historical observed annual peaks plotted in chronological order. Note that annual peaks do not represent all flood events, as a river can reach flood stage multiple times a year. Stage estimates are based on current rating table information |
