|HydroClim Minnesota - August 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
compiled 8/8/06 early distribution by one day
WHAT HAS HAPPENED
- July 2006 precipitation totals across Minnesota fell short of historical averages by one to three inches. For most communities, it was the third consecutive month of below average rainfall.
- July 2006 was exceedingly hot. Monthly mean temperatures were three to five degrees above the historical average. For many Minnesota communities, July 2006 was among the five hottest months on record. The temperature climbed above 90 degrees on numerous occasions and many Minnesota communities reported at least one occurrence of 100 degrees. The hottest temperature reported was 107 degrees on July 30 at Browns Valley in Traverse county.
WHERE WE STAND NOW
- growing season precipitation totals to date (April 1 - early August) are well below historical averages for much of the northern two thirds of Minnesota. Minnesota's drought conditions commenced in mid-May due to a significant and long-lasting change of pattern in the upper atmosphere. For the twelve-week period from May 16 to August 7, rainfall totals were less than five inches in many counties and less than three inches in some northwestern Minnesota communities. This is compared to a historical average of around ten inches for the period. Twelve-week rainfall totals deviated negatively from the historical averages by more than four inches in most areas. Rainfall deficits exceeded six inches in many Minnesota communities. When compared with other May 16 to August 7 rainfall totals in the historical database, this year's rainfall totals for the period rank among the lowest on record in some locales. The situation is especially acute in northwest and north central Minnesota where near-record low precipitation totals are common across a multi-county area.
- as of August 1, the National Drought Mitigation Center (NDMC) - U. S. Drought Monitor indicated that 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 falls in the "D0 - Abnormally Dry" 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 August 4, the state's topsoil moisture was 28% very short, 32% short, 40% adequate, and 0% surplus.
- the U.S. Geological Survey indicates that stream discharge values for many rivers and streams in the northern and central Minnesota rank below the 25th percentile when compared with historical data for the date. In some 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 are near the historical median.
- the potential for wildfires is rated by DNR Forestry as "extreme" in northwestern Minnesota. The fire danger potential is rated as "high" or "very high" in all other locations in the northern two thirds of Minnesota. Wildfire potential is depicted as "low" or "moderate" across the southern one third of Minnesota.
- the August precipitation outlook from the Climate Prediction Center indicates no significant tendencies away from climatological probabilities across Minnesota. 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 from the Climate Prediction Center indicates a tendency towards above normal conditions across Minnesota. Normal August high temperatures are around 80 degrees to start the month, dropping to the mid-70's by month's end. Normal lows are around 60 degrees early in the month, falling to the mid-50's by late August.
- the 90-day precipitation outlook for August through October indicates no significant tendencies away from climatological probabilities across Minnesota. The August through October temperature outlook indicates a tilt towards above normal conditions statewide.
FROM THE AUTHOR
- rainfall totals for this time of year historically average around one inch per week. Widespread rainfall totals of one inch per week will keep the drought situation from deteriorating further and bolster agricultural concerns, but will not greatly improve surface water (rivers, streams, lakes, wetlands) conditions. Surface water conditions will only improve in the near term if rainfall totals far exceed historical averages. In the longer term, a wet autumn would greatly improve surface water conditions. 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 will be prepared frequently. These reports, along with other drought information resources, are available at
NOTES FROM AROUND THE STATE
UPCOMING DATES OF NOTE
- August 17, Climate Prediction Center releases 30/90 day temperature and precipitation outlooksWEB SITES FEATURED IN THIS EDITION
- Minnesota Climatology Working Group
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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