09-27-1989 Council Agenda - Laserfiche WebLink

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(released 10 -29 -86 by Jim Zandlo, State Climatology Office, 296 -4214) HYDROLOGIC YEAR AND 10 -YEAR WETNESS AND RECORD CONDITIONS --------------------------------------------------------- The hydrologic year ending September 1986 was extremely wet over portions of west central and east central Minnesota. Large areas encompassing parts of Carlton, Douglas, Grant, Kandiyohi, Meeker, Ottertail, Pine, Pope, Saint Louis, Stearns, Swift, and Todd and smaller areas within Aitkin, Goodhue, LeSueur, Nicollet counties received sixteen inches or more greater than the normal precipitation amount for that one year period. Such levels of departures indicate that record one year totals are likely within those areas. Known new 12 month records were set at New London with 49.39 exceeding 42.34 for the period ending July 1984, Saint Peter with 46.07 exceeding 44.86 for the period ending July 1908, and Cloquet with 43.92 exceeding 43.84 for the period ending April 1945. Alexandria set its new 12 month record in August 1986 with 41.52 inches which beat the old record of 40.28 for the period ending July 1972. Only the northermost tier of counties experienced below normal precipitation for the period with International Falls receiving 6.13 inches below its normal value. The new record at New London is particularly noteworthy in that 49 inches of precipitation in a twelve month period is an extremely rare event outside the southeasternmost portions of the state. Specifically, the only known occurances outside the southeastern corner were Duluth with 52.35 inches for the year ending July 1882, Worthington with 49.84 for the year ending July 1903, and Isle with 53.04 and Long Prairie with 50.68 both in 1972. Amounts exceeding 49 inches were recorded in the years 1903, 1912, 1952, 1969, 1973, 1981, and 1983 at one or more of the following places: Beaver, Caledonia, Grand Meadow, Harmony, Hokah, Lanesboro, Minnesota City, Preston, Wabasha, and Winona. (The 1972 extreme totals at Isle and Long Prairie accompanied the 'Grand Daddy of Minnesota Flash Floods' which produced amounts of up to 15 inches over that area. Interestingly, the Duluth and Worthington extreme 12 month periods follow the highest two years of precipitation for statewide average precipitation in Iowa, 1881 and 1902, whereas 1902 in Minnesota was only the 30th highest and 1903 the 5th highest statewide average annual totals with first and second highest occuring in 1977 and 1965, respectively. Statewide averages for Minnesota as supplied by the National Climatic Data Center are only available back to 1891.) The current wet year tops a prolonged wet spell for much of the state. Many places have already set new 10 year total precipitation records. The accompanying table 'Some New 10 Year Precipitation Records' gives place names where the January 1977 through the present (October 26, 1986 at the latest) precipitation total is known to already exceed any other 10 calendar year period in the station's record. The new 10 year record at Caledonia, at 385.54 currently, is particularly significant in that it is the highest 10 calendar year total EVER observed in the entire state. The old high total was 379.50 at Grand Meadow for the period 1902 -1911. Bear in mind that 1986 is not yet finished so the Caledonia total may be further increased. Page 66