Check with King County, Washington (was Surface Water Management and now is Bureau of Land Management). They developed a reduced set of 8 years, I think, of rainfall data that contained what they felt was a statistically representative selection of storms from a 50 year record in order to analyze stormwater systems there. After developing the representative years, they also reprogrammed a stripped down version of HSPF and canned it so they could actually make developers size detention vaults with it. They called the program KCRTS for King County Runoff Time Series. I don't have a specific reference, but I believe Dr. Steve Burges and Dennis Lettenmeier of University of Washington assisted King County with this.

http://dnr.metrokc.gov/wlr/dss/kcrts.htm