|HydroClim Minnesota - May 2004
A monthly electronic newsletter summarizing Minnesota climate conditions and the
resulting impact on water resources.
Distributed on the Wednesday following the first Monday of each month.
State Climatology Office - DNR Waters
WHAT HAS HAPPENED
- April 2004 precipitation totals were generally below normal across Minnesota. While some welcome rain did fall during the month, rainfall totals were generally one half inch to one and one half inches short of the historical average. April was extremely dry in sections of west central and northwestern Minnesota where monthly precipitation totals were less than 20 percent of normal.
- the most significant precipitation event of April occurred when a series of thunderstorm complexes dropped one half inch to two inches of rain south and east of a line from Worthington to Duluth. The thunderstorms also brought high winds, very large hail, and at least two tornadoes.
- April 2004 mean monthly temperatures were two to three degrees above normal in the southern two thirds of Minnesota, near normal in the northern one third of the state. April temperature extremes ranged from a high of 95 degrees at Benson (Swift county) on April 28, to a low of 7 degrees at Embarrass (St. Louis county) on April 2. Dozens of daily maximum temperature records were set on April 28 when an extraordinarily hot and dry air mass swept into Minnesota from the southwest.
WHERE WE STAND NOW
- in eight of the ten months from July 2003 through April 2004, precipitation totals in Minnesota fell short of the historical average. For large sections of western and southern Minnesota, precipitation totals were six or more inches below normal over the period. For a significant portion of southeastern Minnesota, precipitation deficits exceeded eight inches. When compared with other July through April time periods in the historical database, the July 2003 through April 2004 combined rainfall totals rank among the driest on record for many areas of western and southern Minnesota. The ten-month totals ranked at or below the 5th percentile in many counties within these regions. A ranking at the 5th percentile indicates that July through April precipitation totals have been lower than July 2003 through April 2004 values in only five out of one hundred years.
- as of April 27, the National Drought Mitigation Center - U. S. Drought Monitor indicated that most of Minnesota was judged to be in the "D1 - Moderate Drought" or "D2 - Severe Drought" categories. The "D2 - Severe Drought" designation encompassed much of western and north central Minnesota. The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators.
- the Minnesota Agricultural Statistics Service reports that as of April 30, the state's topsoil moisture was 10% very short, 32% short, 57% adequate, and 1% surplus. Soil moisture data gathered at University of Minnesota research sites in Lamberton (Redwood county) and Crookston (Polk county) reflect the precipitation deficits reported in those areas. Soil moisture content at these locations are below historical averages, and well short of field capacity. By contrast, soil moisture data gathered at the U. of M. facility in Waseca (Waseca county) indicate that the rooting zone is amply supplied with water.
- the U.S. Geological Survey indicates that stream discharge values for nearly one half of Minnesota's rivers rank below the 25th percentile for the date. Low stream flows are most common in western and southern sections of Minnesota. Stream discharge rates in some of these areas rank below the 10th percentile for the date. Elsewhere, stream flow values are nearer the middle of the historical distribution.
- the potential for wildfires is rated by DNR Forestry as "very high" to "extreme" across much of Minnesota.
- nearly all of Minnesota's lakes are now free of ice. Some lakes in northern Lake county and in Cook county remain all or partially ice covered. Lake ice-out in 2004 was five to twelve days earlier than average across most of Minnesota. Only in north central and northeastern counties did lake ice out occur near historical average dates.
- the May precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. May precipitation normals range from just over two inches in northwestern Minnesota to just less than four inches in southeastern counties.
- the May temperature outlook indicates a tilt towards below normal temperatures across Minnesota. Normal May high temperatures are in the low to mid-60's early in the month, rising to the low to mid-70's at month's end. Normal May low temperatures are in the mid-30's to near 40 to start the month and climb to the mid-40's to low 50's as the month ends.
- the 90-day precipitation outlook for May through July shows no significant tendencies away from climatological probabilities. The May though July also indicates no significant tendencies away from climatological probabilities.
- the National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. A hydrologic model is initialized using current conditions of stream flow and soil moisture across a basin. The model is allowed to run into the future with multiple scenarios using multiple years of historical climatological data. The climatological data are weighted by 90-day climate outlooks for temperature and precipitation trends. Model output offers a complete range of probabilistic values of stream stage and discharge for numerous forecast points. The product provides a risk assessment tool which can be used in long-range planning decisions involving flooding or low flow concerns. These products are part of the National Weather Service's Advanced Hydrologic Prediction Service (AHPS) and are produced near the middle of each month.
FROM THE AUTHOR
NOTES FROM AROUND THE STATE
UPCOMING DATES OF NOTE
- May 17, Climate Prediction Center releases 30/90 day temperature and precipitation outlooksWEB SITES FEATURED IN THIS EDITION
http://climate.umn.edu - Minnesota Climatology Working Group
http://www.drought.unl.edu/ - National Drought Mitigation Center
http://www.nass.usda.gov/mn/ - Minnesota Agricultural Statistics Service
http://swroc.coafes.umn.edu/ - University of Minnesota Southwest Research and Outreach Center, Lamberton
- U.S. Geological Survey, Minnesota
- Minnesota Department of Natural Resources - Division of Forestry
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://www.crh.noaa.gov/ahps - National Weather Service, Central Region Headquarters
Dr. Mark Seeley, Professor of Climatology/Meteorology, University of Minnesota - St. Paul
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