WMS:HEC-HMS Frequency Storm

"The frequency storm method can be used to create a balanced, synthetic storm with a known exceedance probability. Automatic adjustments for storm area and series type are based on the exceedance probability. Depth-duration data are usually obtained from publications such as TP-40 (National Weather Service, 1961)." (HEC-HMS User's Manual) The options for defining a frequency storm are shown below:

HMS Meteorological Model dialog for the "Frequency Storm" method.

Follow the following steps (from the HEC-HMS User's Manual) to set up a frequency storm:

1. Select a storm exceedance probability from the list (Exceedance probability = (1 / Return Period) * 100%).
2. Set the series type for the desired output.
3. Select the maximum intensity duration and the total storm duration.
4. Enter the precipitation depths corresponding to the selected exceedance probability for the durations between the maximum intensity and storm durations.
5. Select the percentage of the storm duration that occurs before the peak intensity.
6. Enter the storm area. This is equal to the total drainage area at the point where the exceedance probability will be inferred for the computed flow.

Related Topics:

• Defining the Meteorological Model