|HydroClim Minnesota - September 2003
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
- a persistently dry weather pattern that began in July continued throughout the month of August. August 2003 rainfall totals across most of Minnesota rank among the lowest of the modern record. August rainfall totals were generally below one and one half inches, with many communities reporting less than one inch of precipitation for the month. Precipitation totals fell short of the historical average by one and one half to three and one half inches.WHERE WE STAND NOW
- no significant widespread rain events occurred in Minnesota during the seven-week period from mid-July through early September. Large areas of northwestern, west central, central, and southeastern Minnesota received less than one and one half inches of rain for the interval from July 15 through September 2. Total rainfall for the mid-July through early September period fell short of normal by two to five inches. Rainfall deficits exceeded five inches in far southeastern Minnesota. When compared with other July 15 through September 2 time periods in the historical database, mid-July through early September 2003 rainfall totals rank among the lowest on record. Precipitation for the period ranks below the 5th percentile (1 out of 20 years) across large areas of Minnesota. Rainfall totals for many locations are at or below the 1st percentile, indicating that rainfall for mid-July through early September 2003 was near or below all-time minimum values for the date span.
- August temperatures were warmer than normal across Minnesota. August average monthly temperatures ranged from two to five degrees above normal. A preliminary calculation of a statewide average monthly temperature indicates that August 2003 ranked as the sixth warmest August of the modern record. Temperature extremes during August ranged from 101 degrees F at Browns Valley (Traverse County) on the 18th to 32 degrees F at Tower (St Louis County) on the 12th.
- growing season precipitation totals to date (April 1 - September 2) are highly variable across Minnesota. For an 50-mile wide band bisecting central Minnesota, 2003 growing season precipitation totals are 10 to 50 percent above historical averages. In these areas, April through August precipitation totals ranked above the 75th percentile when compared with historical April-August values. Heavy rains during the first half of the growing season were dramatically offset by the extraordinary dryness of the mid and late summer. Elsewhere around Minnesota, growing season precipitation totals make up a patchwork pattern of above, near, and below normal conditions.
- as of August 26, the National Drought Mitigation Center - U. S. Drought Monitor indicates that much of the southern two-thirds of Minnesota is judged to be in the "D1 - Moderate Drought " category. The remainder of Minnesota is rated in the "D0 - Abnormally Dry" category. The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators. Impacts associated with a "D1 - Moderate Drought" designation include crop and pasture damage, high wildfire risk, and low surface water and surficial aquifer levels.
- the Minnesota Agricultural Statistics Service reports that as of August 29, the state's topsoil moisture was 48% very short, 36% short, 16% adequate, and 0% surplus. Crop conditions continued to deteriorate throughout the month of August. Yield reductions in row crops such as corn, soybeans, and sugar beets now appear certain. Early autumn rainfall will not benefit this year's crop, but soil moisture recharge before soil freeze-up is crucial to the success of next year's growing season.
(see: http://www.nass.usda.gov/mn/cwmn.htm , http://mrcc.sws.uiuc.edu/Watch/Drought/moisture.htm
- stream flows continue to diminish everywhere in Minnesota in response to the predominantly dry weather. The U.S. Geological Survey indicates that stream discharge values for roughly 30 percent of Minnesota's rivers now rank below the 25th percentile for the date. Stream flows rank below the 10th percentile in some locations.
- the potential for wildfires is rated by DNR Forestry as "very high" in a small section of central Minnesota, "high" across the southern two-thirds of the state, and "moderate" across the northern one-third of Minnesota.
- the September precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. 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 also shows no significant tendencies away from climatological probabilities. 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 shows no significant tendencies away from climatological probabilities. The September though November temperature outlook also indicates no significant tendencies away from climatological probabilities.
- a cursory investigation of years with the driest Augusts on record indicates that late-summer dryness does not foreshadow a dry autumn. In seven of the ten years with the driest Augusts, September through November precipitation totals were within one standard deviation of the long-term mean (6.12 inches). Two autumns out of the ten were wet, and one autumn was dry.
- 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 the current conditions of stream flow and soil moisture across a basin. The model is allowed to run into the future with multiple scenarios using more than 30 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 18, 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
- Minnesota Agricultural Statistics Service
http://mrcc.sws.uiuc.edu/ - Midwestern Regional Climate Center
http://swroc.coafes.umn.edu/ - University of Minnesota Southwest Research and Outreach Center, Lamberton
- U.S. Geological Survey, Minnesota
- Minnesota DNR Division of Waters
- Minnesota DNR 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, Meteorologist and Climatologist, University of Minnesota
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