Atlas of Precipitation Extremes for the Northeastern United States and Southeastern Canada

Daniel S. Wilks and Richard P. Cember

NRCC Research Publication RR 93-5

Extreme precipitation events have the potential to produce localized or widespread flooding, with concomitant damage to property and potential loss of life. The climatology of these very large precipitation events is therefore an important component of engineering design for structures and facilities that must withstand or protect against such events.

The most widely used atlas of precipitation extremes in the U.S., Rainfall Frequency Atlas of the United States (Hershfield 1961), also known as Technical Paper 40, is more than thirty years old. This standard work was based on fitting the Gumbel probability distribution to extreme rainfall data from relatively few stations, with average record length of only 22.6 years. Operationally, it has been found that Technical Paper 40 often underestimates the largest extreme precipitation events (Angel and Huff 1991). It is not clear to what extent this systematic underestimation results from inadequacy of the Gumbel distribution for extrapolation to the important rare events (Jenkinson 1955), or from the insufficient length of record available in 1961. However, it is widely agreed that updating and revision of that document is warranted. This atlas presents updated statistics of extreme precipitation for the 12-state northeast region of the US.

40 pp.

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