The Value of Storm Typing in Hydrologic Hazards Assessments – Experience Across Various Climates

The storm typing approach in precipitation-frequency estimation has been applied in various climate regimes across North America. This approach provides for a direct link between watershed precipitation-frequency and the storm spatial, temporal, and seasonal characteristics and has allowed greater insight into the statistical behavior of precipitation for the various storm types.
An automated methodology has been developed to create storm type-specific annual maxima precipitation datasets using meteorological information. The storm types included local convective thunderstorms, mesoscale storms with embedded convection, synoptic-scale Mid-Latitude Cyclones, and Tropical Storms.
The importance of storm typing for evaluating hydrologic hazards is illustrated across various climates. Results have shown that storm typing is essential for precipitation-frequency estimation for tropical storms because they are inherently a mixed distribution, where some years do not contain a significant tropical storm event. It is also particularly beneficial in more arid climates where 24-hour and 48-hour data are often a mix of synoptic scale storms and convective storms of shorter duration (mesoscale or local in size).