|HydroClim Minnesota - September 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
- rainfall totals across Minnesota were generally below normal in August 2004. Rainfall was short of the historical average by one to two inches in many locations. Above normal precipitation was reported only in some areas of northwest, southwest, and south central Minnesota.
- the most intense rainfall event of August 2004 occurred on the 23rd and 24th over a small area of southwest Minnesota. A stalled thunderstorm complex dropped more than six inches of rain on portions of Yellow Medicine, Lyon, and Lincoln counties. The heaviest reported rainfall total was 8.75 inches near Porter of northeastern Lincoln county.
- heavy rains fell across much of Minnesota over the Labor Day weekend. In the northern half of Minnesota, two separate rainfall episodes dropped a cumulative total of three or more inches on locations such as Fergus Falls, Detroit Lakes, Brainerd, Grand Rapids, and International Falls.
- following a trend initiated in May and continuing throughout the summer, August 2004 temperatures were very cool. August monthly mean temperatures fell short of normal by four to eight degrees. For some communities, August 2004 was the coldest August on record. Many low temperature and cold daytime maximum temperature records were broken. The temperature extremes for August ranged from 91 degrees at Canby (Yellow Medicine county) on the 1st, to 20 degrees at Embarrass (St. Louis county) on the 21st.
- on three consecutive mornings, August 19 through 21, record low temperatures were reported around Minnesota. In some areas, the temperature dropped to near or below freezing. The extraordinarily cold temperatures led to substantial crop damage.
WHERE WE STAND NOW
- growing season precipitation totals to date (April 1 through September 7) are quite variable across Minnesota. Growing season precipitation totals over nearly all of southern Minnesota, west central Minnesota, and northwestern Minnesota rank above the 75th percentile when compared with past years. In some of these areas, growing season precipitation totals have exceeded the historical average by more than six inches. Conversely, growing season rainfall in sections of north central and northeastern Minnesota has fallen short of average by two to four inches. When compared with other April through early September periods in the historical database, this season's precipitation ranks below the 25th percentile in some of these locations.
- as of August 31, the National Drought Mitigation Center (NDMC) - U. S. Drought Monitor indicated that most of the state of Minnesota is free of drought designations. However, an area of north central and northeastern Minnesota is judged to be in the "D0 - Abnormally Dry" category. In spite of the heavy early-September rain, growing season precipitation deficits persist in this region. 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 September 3, the state's topsoil moisture was 2% very short, 19% short, 75% adequate, and 4% surplus.
- U.S. Geological Survey stream gauging indicates a patchwork pattern of stream discharge values across Minnesota. Due to very dry summer weather, stream discharge in many north central and northeast Minnesota rivers ranked below the 10th percentile when compared with historical values on August 30th. Heavy early-September rains in this region caused varying responses from the river systems. For those basins with deeper soils, gentle terrain, and numerous wetland complexes; much of the rain was absorbed by available buffers, and stream discharge did not show a dramatic increase. For other basins with steep terrain and shallow soils, significant rises in river levels were observed. The heavy early-September rain also fell upon west central Minnesota where some minor flooding was reported. As has been the case during most of the open water season, stream discharge remains high in far northwestern Minnesota.
- the potential for wildfires is rated by DNR Forestry as "low" across Minnesota.
- the September precipitation outlook from the Climate Prediction Center indicates a significant tilt towards above normal conditions across Minnesota. September precipitation normals range from near two inches in far western Minnesota to around three and one half inches in eastern sections of the state.
- the September temperature outlook shows a strong bias towards below normal readings. Normal September high temperatures are in the mid-70's to start the month, dropping to the low to mid-60's by month's end. Normal lows are in the mid-50's early in the month, falling to around 40 by late September.
- the 90-day precipitation outlook for September through November indicates no significant tendencies away from climatological probabilities across Minnesota. The September through November temperature outlook 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 many 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
- September 16, 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
- U.S. Geological Survey, Minnesota
- Minnesota Department of Natural Resources - Division of Waters
- 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
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