|HydroClim Minnesota - October 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
- September 2003 rainfall totals varied widely across Minnesota. September rainfall in southwestern, northwestern, and northeastern Minnesota counties exceeded normal by one to two inches. September precipitation was near normal across the central one third of Minnesota. September rainfall in north central, south central, and southeastern Minnesota communities fell short of normal by about one inch.WHERE WE STAND NOW
- much needed rain fell on many areas during a four-day period from September 9 to September 12. A very slow moving cold front dropped one to three inches of rain on southwestern, central, and northeastern Minnesota. Some areas of southwestern Minnesota received over four inches of rain during the event.
- no significant widespread rain events occurred in Minnesota during the eight-week period from mid-July through the first week of 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 8. Total rainfall for the mid-July through early September period fell short of normal by three or more inches. Rainfall deficits exceeded six inches in portions of southeastern Minnesota. When compared with other July 15 through September 8 time periods in the historical database, mid-July through early September 2003 rainfall totals rank among the lowest on record. Rainfall totals for most locations were 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.
- September monthly mean temperatures were very close to historical averages. A warm first half of the month was counterbalanced by colder than normal temperatures during the last week of the month. Temperature extremes during September ranged from 97 degrees F at Browns Valley (Traverse County) on the 6th, to 19 degrees F at Embarrass (St Louis County) on the 29th.
- warm season precipitation totals to date (April 1 - October 6) are highly variable across Minnesota. 2003 warm season precipitation totals are 30 percent below normal for portions of southeastern Minnesota. In these areas, warm season precipitation totals rank below the 10th percentile when compared with the historical data set. Warm season precipitation totals rank below the 20th percentile for sections of south central Minnesota and areas near the Mississippi River headwaters. For a 30-mile wide band bisecting central Minnesota, 2003 warm season precipitation totals are 10 to 25 percent above historical averages. In these areas, heavy rains during the first half of the growing season were offset by the extraordinary dryness of the mid and late summer. Elsewhere around Minnesota, warm season precipitation totals make up a patchwork pattern of above, near, and below normal conditions.
- as of September 30, the National Drought Mitigation Center - U. S. Drought Monitor indicates that much of the southern three-quarters of Minnesota is judged to be in the "D1 - Moderate Drought" category. West central and southeastern Minnesota counties are rated in the "D2 - Severe Drought" classification. For a small section of southeastern Minnesota the drought depiction worsened from "D2 - Severe Drought" to "D3 - Extreme Drought" this past week. 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 October 3, the state's topsoil moisture was 16% very short, 43% short, 41% adequate, and 0% surplus. Although September rains moistened the state's topsoil, the second and third foot of the soil profile remains extremely dry. 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
- the U.S. Geological Survey indicates that stream discharge values for roughly one quarter of Minnesota's rivers rank below the 25th percentile for the date. Those rivers with low streamflows include major watercourses such as the Red River, Rainy River, Minnesota River, and Mississippi River. Streamflows on most of the state's smaller rivers rank between the 25th and 75th percentile for the date.
- lake levels around Minnesota are below historical averages for the date. Unlike conditions in the mid-summer, lakes linked to river systems AND landlocked lakes now show low water levels.
- the potential for wildfires is rated by DNR Forestry as "high" for nearly all of Minnesota.
- the October precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. Normal October precipitation ranges from one and one half inches in northwestern Minnesota, to over two and one half inches in portions of north central and northeastern Minnesota. The October temperature outlook also shows no significant tendencies away from climatological probabilities. Normal October high temperatures fall from the low to mid 60's early in the month to the upper 40's by month's end. Normal October low temperatures drop from the low 40's early in the month to near 30 by late October.
- the 90-day precipitation outlook for October through December shows no significant tendencies away from climatological probabilities. The October though December 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 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
- many Minnesota communities received beneficial rains in mid-September. However, the rainfall did not erase the moisture deficits accrued during the months of July and August. Most of Minnesota can be categorized as experiencing some level of drought. Drought conditions during the autumn are often masked by the fact that the growing season has come to an end. Additionally, surface water levels are typically low even during average years.
NOTES FROM AROUND THE STATE
Autumn precipitation can efficiently recharge the soil moisture profile. Fall storms often bring gentle rains, leading to effective infiltration rates. Cool temperatures reduce evaporation potential, and plant transpiration is near zero. Given average October temperatures, the soils will remain unfrozen and receptive to precipitation until early November in the north, mid-November in the south. Therefore, October and early-November precipitation events are needed to rebound from the summer's moisture shortfalls and to improve prospects for the 2004 growing season.
UPCOMING DATES OF NOTE
- October 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
- 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
- Bob Potocnik, Surface Water Specialist, DNR Waters - St. Paul
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