|HydroClim Minnesota - September 2006
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
- August 2006 precipitation totals varied widely across Minnesota. For the fourth consecutive month, rainfall was below average for much of the northern one half of Minnesota. Monthly rainfall totals fell short of average by one to three inches in many northern Minnesota counties. Conversely, August was a very wet month in portions of east central and southeastern Minnesota. Rainfall in these areas topped the historical average by two or more inches. Unfortunately, the heaviest of the August rains did not fall on those areas suffering the greatest from this season's drought.
- three extremely heavy rainfall events occurred during the month of August. Very heavy rain fell on south central Minnesota on August 1 and 2. Portions of Martin and Faribault counties received over five inches of rain in a 30 hour period. During the late evening of August 16 and early morning of August 17, nearly six inches of rain fell along a very narrow corridor in central Marshall county. On August 24, intense thunderstorms dropped over five inches of rain on portions of Dodge and Olmsted counties. This was the same storm complex that produced damaging winds and hail across much of the southern one half of Minnesota, and a deadly tornado in Le Sueur county.
- monthly mean temperatures for August 2006 were moderate, finishing near to slightly above historical averages. The month lacked the extraordinarily hot weather experienced in July, a relief to the drought-stricken landscape.
WHERE WE STAND NOW
- growing season precipitation totals to date (April 1 - early September) are well below historical averages for much of the northern two thirds of Minnesota. For the sixteen-week period from May 16 to September 5, rainfall totals were less than six inches in some areas of northwestern and north central Minnesota. The sixteen-week rainfall totals deviated negatively from historical averages by more than four inches across most of the northern two thirds of Minnesota. Rainfall deficits exceeded six inches in some northern and central Minnesota communities. This is the equivalent of receiving zero rainfall for the entire month of June and one half of July. When compared with other May 16 to September 5 rainfall totals in the historical database, this year's rainfall totals for the period rank among the lowest on record in some north central and central Minnesota locales. The situation is especially acute in north central Minnesota, particularly sections of Beltrami and western Itasca counties.
- in a product that will be released September 7, the National Drought Mitigation Center (NDMC) - U. S. Drought Monitor indicates that many counties in northwestern, north central, and central Minnesota fall in the "D3 - Extreme Drought" category. The remainder of the northern two thirds of Minnesota is rated as experiencing "D2 - Severe Drought" or "D1 - Moderate Drought". Most of the southern one third of Minnesota does not warrant a drought classification. The NDMC index is a blend of science and subjectivity where intensity categories are based on five key indicators and numerous supplementary indicators.
- the Minnesota Agricultural Statistics Service reports that as of September 1, the state's topsoil moisture was 12% very short, 29% short, 58% adequate, and 1% surplus.
- the U.S. Geological Survey indicates that stream discharge values for most rivers and streams in northern and central Minnesota rank below the 25th percentile when compared with historical data for the date. In many cases, stream flow in these areas ranks below the 10th percentile for the date. Watersheds with stream flow values below the 10th percentile are deemed to be in the "protected flow" category. Surface water appropriation permits may be suspended by the Minnesota Department of Natural Resources when stream flows reach this threshold. Stream discharge values for most rivers and streams in the southern one third of the state, and in the Red River basin, are near or above the historical median.
- the potential for wildfires is rated by DNR Forestry as "high" or "very high" across most of the northern one third of Minnesota. The fire danger potential is rated as "moderate" in western Minnesota and "low" in southeastern counties.
- the September precipitation outlook from the Climate Prediction Center indicates no significant tendencies away from climatological probabilities 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 from the Climate Prediction Center indicates a strong tilt towards above normal conditions across Minnesota. 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 most of Minnesota. The forecast leans towards above normal precipitation in far northwestern Minnesota and slants towards below normal precipitation in far southeastern Minnesota. The September through November temperature outlook indicates a tilt towards above normal conditions statewide.
FROM THE AUTHOR
- a wet autumn would greatly improve drought conditions in northern and central Minnesota. Fall rainfall is very efficient in replenishing soil moisture reserves and surface water systems. Fall rains are often gentle and widespread. Additionally, most native and agronomic plants have reached the end of their growing season and are no longer consuming water.
- drought situation reports are prepared frequently by this office. These reports, along with other drought information resources, are available at
NOTES FROM AROUND THE STATE
UPCOMING DATES OF NOTE
- September 21, Climate Prediction Center releases 30/90 day temperature and precipitation outlooksWEB SITES FEATURED IN THIS EDITION
- Minnesota Climatology Working Group
http://www.crh.noaa.gov/mpx - National Weather Service Forecast Office - Chanhassen
http://www.drought.unl.edu - National Drought Mitigation Center
- USDA, National Agricultural Statistics Service
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey
http://www.dnr.state.mn.us/waters - Minnesota Department of Natural Resources, Division of Waters
http://www.dnr.state.mn.us/forestry - Minnesota Department of Natural Resources, Division of Forestry
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
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