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<br />Generalized Estimates of Probable Maximum Precipitation
<br />for the United States West of the I05th Meridian
<br />
<br />for Areas to 400 Square Miles and Duratious to 24 Hours
<br />
<br />INTRODUCTION
<br />
<br />Assignment. Generalized estimates of prob-
<br />able maximum precipitation have been available
<br />for the United States east of the lO5th meridiau
<br />for several years. [1]. The need for similar data
<br />for the planning and design requirements of the
<br />Soil Conservation Ser"ice in the region west of the
<br />105th meridian led that agency to cooperate with
<br />the 'Veather Bureau in the preparation of like
<br />estimates for that area. This report presents
<br />gene,ralized estimates of probable maximum pre-
<br />cipitation for areas from a point to 400 square
<br />miles and for durations up to 24 hours.
<br />Scope. The engineer who will be using the
<br />generalized estimates of probable maximum pre-
<br />cipitation presented herein will naturally want to
<br />know what these values represent, how they were
<br />obtained, how they should be used, and how accu-
<br />rate they are. For these reasons, this report not
<br />only deals with the final results but goes into as
<br />much detail as appea,rs necessary to provide the
<br />engineer with an adequate background for intelli-
<br />gent use of the results.
<br />Accuracy of resnlts. The generalized estimates
<br />of probable maximum precipitation presented in
<br />this report are the most accurate that can be de-
<br />rived on the basis of the a vaila,ble data and the
<br />current stage of meteorologiC&1 knowledge,
<br />particularly concerning storm structure or meeh-
<br />a.nism. Both these factors will increase and
<br />improve with time. It should not be astonishing,
<br />therefore, if future data and developments in t.he
<br />field of meteorology should indicate a need for
<br />revision of the estimates.
<br />
<br />Acknowledgments. The project was under the
<br />general supervision of 'V. T. 'Wilson, Chief of the
<br />Cooperative Studies Sect.ion of the Hydrologic
<br />Services Division, W. E. Hiatt, Chief. The proj-
<br />ect leader was J. F. ~Iiller of the Cooperative
<br />Studies Section, who personally directed the stud-
<br />ies related to the meteorological phase of the
<br />project. The statistical phase was developed and
<br />the related work conducted by D. ;\1. Hershfield,
<br />L. L. Weiss, and 'V. T. Wilson, all of Cooperative
<br />Studies Section. Conferees included Dr. C. S.
<br />Gilman, V. A. Myers, and J. T. Riedel, a,ll of the
<br />Hydrometeorological Section; M. A. Kohler,
<br />Chief Research Hydrologist; J. L. H. Paulhus,
<br />Division Staff Hydrologist; A. L. Shands,
<br />Assistant Chief of Division; and R. D. Tarble,
<br />Radar Hydrologist. Coordination with the Soil
<br />Conservation Service was maintained through H.
<br />O. Ogrosky, Chief, Hydrology Branch, Engineer-
<br />ing Division. Collection and processing of data
<br />were performed by R. L. Bi,rchfie1d, S. L. Briggs,
<br />M. R. Caspar, D. .J. Foat, N. S. Foat, R. L. Gotts-
<br />chalk, R. B. Holleman, E. C. I'Anson, A. E. Lar-
<br />kin, W. E. Miller, C. Mundt, C. E. Koboa, S.
<br />Otlin, C. L. Smith, G. W. Sohns, J. B. Tucker,
<br />and A. J. Weinstein. Typing was done by L. L.
<br />Nelson and N. S. Foat; drafting by K. Calub,
<br />V. Campbell, and C. 'V. Gardner. The final
<br />draft of the text was written by J. L. H. Paulhus
<br />and edited by Mrs. L. K. Rubin of the Hydro-
<br />meteorolo,,"ical Section.
<br />
<br />I
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