WMOD00377

• Contract/Permit #: 14-06-D-5640
• Project Name: Park Range Atmospheric Water Resources Program
• Title: Park Range Atmospheric Water Resources Program - Phase II - Part A
• Date: 11/15/1966
• Weather Modification - Doc Type: Report

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centered along a line from Hayden to Steamboat Springs, and presumably on

eastward to the crest of the Park Range. To test the validity of these results,

a ten year retrospective study will be conducted during the summer of 1966.

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Since upslope orographic effects are the main control in storm total
precipitation over the Park Range, we next studied the 24-hour precipitation
averages versus speed and direction of the 700 mb wind, The data chosen
consisted of 24-hour total precipitation at Steamboat Springs for each day on
which measurable precipitation fell from November 1964 through April 1965.
On days with measurable precipitation at Steamboat Springs, the average 700
mb and 500 mb wind direction s were plotted yielding Figure s 27 and 28. For
the 1964- 65 season, the chance s of receiving more than O. 20 inche s are very
small unless the 700 mb and 500 mb wind direction lies between 2400 and 3000,

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Figure 29 - - a plot of the u-component (perpendicular to the Park
Range) of the 700 mb wind for days with measurable precipitation--shows a

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marked increase in average precipitation amounts for 700 mb u-components

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of 20 kts and,greater. The very high average of 0.75 inches for u-components
of 32-40 kts occurs only a few times per season. Figure 30 gives a picture
of the contribution of each 700 mb u-component category toward total season-
al precipitation a.nd suggests that winds of> 10 knot speed are the principal
contributor s.

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The following three synoptic case studie s illustrate typical storm
situations during the 1965-66 winter season. A condensed summary of pre-
cipitation and upper - air wind tempe rature characteri stic s for each precipita-
tion period of this season is given in Table V.

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