Products on this page are considered experimental. A water year is defined as the 12-month period beginning October 1 of any year and. The calculation was also made for the probabilities of reaching 75% of normal by end of water year, 125%, etc., for these figures.Ĭontribution from Dr. More information about the quality of precipitation data is available. Rainfall totals are given for the past 7, 10, 14, 30, 60, and 90 days up to the current date, as well as the total for the current month, year, and previous year. The fraction of years that at least reached that threshold is the probability estimate. The Recent Rainfall table shows the total rainfall (in inches) for each Mesonet site. To arrive at the probabilities shown, the precipitation totals for the remaining months of the water year were tabulated in the long-term historical record (WY1948-2017 in these figures) and the number of years in which that precipitation total equaled or exceeded the amount still needed to reach normal were counted. Thus the odds of reaching normal by the end of the water year are just the odds of precipitation during the remaining of the year equaling or exceeding that remaining amount. How the probabilities above were estimated:Īt the end of a given month, if we know how much precipitation has fallen to date (in the water year), the amount of precipitation that will be required to close out the water year (on Sept 30) with a water-year total equal to the long-term normal is just that normal amount minus the amount received to date. The bottom plots show the probability of reaching 100% (and other exceedances) of normal two year precipitation by the end of the next water year (combining the current and next water years). The top plots show the probability of reaching 100% (and other exceedances) of normal two year precipitation by the end of the current water year (combining the current and previous water years). The plots below combine the current water year with either the previous or the next water year. The above methodology can be applied to time periods spanning multiple water years. Odds of Two Water Years Reaching Various Fractions of Normal Precipitation Totals Below uses the same methodology above, but is calculated for various fractions (including 100%) of water year total precipitation.īelow flips the analysis and shows what water year total precipitation percentage has a 50% (and other exceedances) chance of being equaled or exceeded this year.
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