|HydroClim Minnesota - August 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 persistent weather pattern in July produced conditions which favored the formation of geographically isolated thunderstorm complexes throughout the month. These clusters of thunderstorms were often short-lived, and covered relatively little area. Therefore, July rainfall was below normal in most Minnesota communities, falling short of historical averages by one half inch to one and one half inch. Very isolated heavy rains led to above normal July precipitation totals for a handful of communities, mainly in northern Minnesota.WHERE WE STAND NOW
- isolated episodes of severe weather swept through Minnesota on July 14th and 19th. There were many reports of hail, damaging winds, and tornadoes on these dates.
- July temperatures were near normal to slightly cooler than normal across Minnesota. Temperature extremes ranged from 96 degrees at Browns Valley on the 19th, to 34 degrees at Embarrass and Tower on the 18th.
- for the fifth time in the past six summers, areas of Minnesota suffered through July dewpoint temperatures in the 80's. On July 26th, the combined influence of high temperatures and high dewpoint temperatures created heat index values at or near 110 degrees.
- growing season precipitation totals to date (April 1 - August 4) are highly variable across Minnesota. For an eighty-mile wide band bisecting central Minnesota, growing season precipitation totals are 10 to 50 percent above historical averages. In these areas, April through July 2003 precipitation totals rank above the 90th percentile when compared with historical April-July values. Elsewhere around Minnesota, growing season precipitation totals make up a patchwork pattern of above, near, and below normal conditions across the landscape.
- as of August 5, the National Drought Mitigation Center - U. S. Drought Monitor indicates that portions of north central and northeastern Minnesota, and many of the counties in the southern one third of Minnesota, are judged to be in the "D0 - Abnormally Dry" category. The remainder of Minnesota is free of drought designation. 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 August 1, the state's topsoil moisture was 6% very short, 37% short, 56% adequate, and 1% surplus.
- stream flows diminished nearly everywhere across Minnesota over the last few weeks in response to the predominantly dry weather. The U.S. Geological Survey indicates that stream discharge values for most of Minnesota's rivers now rank near the middle of the historical distribution for the date, somewhere between the 25th and 75th percentiles.
- as of mid-summer, lake levels in many central and east central Minnesota counties are well above average values. This can be attributed to heavier than average precipitation amounts occurring over a two and one half year period, beginning in 2001. Precipitation totals for the 31-month period exceeded normal by more than 12 inches over large areas of central and east central Minnesota. Precipitation totals topped normal by more than 20 inches in some communities within this region.
, also see "NOTES FROM AROUND THE STATE" below)
- the potential for wildfires is rated by DNR Forestry as low throughout Minnesota.
- the August precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. August precipitation normals range from under three inches in northwestern and west central Minnesota, to over four and one half inches in southeastern counties. The August temperature outlook shows a tilt towards above normal conditions in far northwestern Minnesota, with no significant tendencies away from climatological probabilities elsewhere in the state. Normal August high temperatures are around 80 to start the month, dropping to the mid-70's by month's end. Normal lows are around 60 early in the month, falling to the mid-50's by late August.
- the 90-day precipitation outlook for August through October shows no significant tendencies away from climatological probabilities. The August though October 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
NOTES FROM AROUND THE STATE
- from Mike Mueller, DNR Hydrologist - CambridgeUPCOMING DATES OF NOTE
(July 21) In the past couple of months, I have been asked to assist in trying to alleviate high water table or surface flooding in several areas within my work area. Three areas in particular are smaller landlocked wetlands which have been unable to assimilate the above normal precipitation through normal infiltration and evaporation/transpiration. Most surface water basins are full, many lakes are at or above their "Ordinary High Water Levels". Of particular note is the expression of very high water tables in areas full of mature burr oaks situated on the Anoka Sand Plain. Soil borings taken in a grove of 18 to 24 inch diameter oaks found unmottled sand down to 24 to 30 inches but saturation as high as 18 inches.
The east central region is now entering the third year of above normal rain and, at least around Cambridge, the preceding two years were the wettest and 4th wettest in 70 years of record. Homes constructed prior to about 1980 appear to be the least able to withstand the impact of basement seepage, perhaps due to less restrictive building codes from that time period.
- August 21, 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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