HydroClim Minnesota - August 2009

A monthly electronic newsletter summarizing Minnesota's 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 8/5/2009

What happened in July:

With a few exceptions, July 2009 was a dry month across nearly all of Minnesota. Many Minnesota locales reported July precipitation totals that fell short of the historical average by one to three inches. However, some central and east central Minnesota counties, along a line that extends from roughly Brainerd to Moose Lake, received near to above-average rainfall. The overall dryness in Minnesota extended a rainfall shortfall that began in early April and continues to the present.
[see: July 2009 Climate Summary Table | July 2009 Precipitation Departure Map]
The most sigificant widespread rainfall event of the month occurred on July 14 when more than two inches of rain fell along a 30 to 50 mile-wide band that stretched from Breckenridge to Brainerd to Cloquet. More than four inches of rain was reported in portions of Cass, Crow Wing, and Aitkin counties. Localized flooding was reported in communities such as Staples and Aitkin. Heavy downpours were also reported at Sauk Rapids on July 14 (3.11 inches) and Lakefield on July 9-10 (3.53 inches).
[see: Heavy Rain - July 14]
July 2009 was the third coolest July in Minnesota's historical climate record. Mean monthly temperatures for the month finished three to seven degrees below the historical average statewide. Nearly all Minnesota reporting locations failed to reach 90 degrees during the month of July, a very rare occurrence. Extreme temperature values for July ranged from a high of 90 degrees at Wild River State Park (Chisago County) on the 10th, to a low of 31 degrees in Brimson (St. Louis County) on the 13th. Between July 12 and July 19, many temperature records were set for coldest maximum or coldest minimum daily temperature across the state. The seasonally cool temperatures prolonged a trend that began in northern Minnesota in May and throughout the state in June. The cooler-than-normal temperatures reduced evaporation and transpiration rates, partially counterbalancing the precipitation deficits and keeping drought conditions from worsening at a more rapid pace.
[see: July 2009 Climate Summary Table | Chilly July 13 | Cool July 16-17 | Lack of 90-degree days | Cool July]

Where we stand now:

The U. S. Drought Monitor, released on July 30, placed areas of west central, central, east central and southeastern Minnesota counties in the Moderate Drought and Severe Drought categories. Large portions of the rest of Minnesota are considered to be Abnormally Dry. The drought designations are the result of two spells of dry weather, one short-term and one longer-term. The shorter-term dryness has persisted since early April and impacts much of the state. The long-term dry spell commenced in mid-June 2008 and has persisted in east central and southeast Minnesota, producing 14-month precipitation deficits of eight or more inches. The U. S. Drought Monitor index is a blend of science and subjectivity where intensity categories are based on several indicators.
[see: Drought 2009]
DNR Waters and the U.S. Geological Survey report that stream discharge values are low for many locations in south central, east central, and northeastern Minnesota. Flow rates at these locations rank below the 25th percentile in the historical distribution for early August. By contrast, many points along the Red River and its tributaries report flow rates well above the historical median for this time of year.
[see: USGS Streamflow | DNR Streamflow]
The Lake Superior water level is down three inches from last year at this time and remains below the long-term average. Water levels on many central and east central Minnesota lakes and wetlands are very low.
[see: Corps of Engineers Great Lakes Water Levels | White Bear Lake Water Level | Lake Minnetonka Water Level]
The Minnesota Agricultural Statistics Service reports that as of August 2, topsoil moisture was 13% "Very Short", 33% "Short", 54% "Adequate", and 0% "Surplus". Topsoil moisture shortfalls exist across much of the central and southern Minnesota.
[see: Agricultural Statistics Service Crop Progress and Condition]
The potential for wildfires is currently rated by DNR Forestry as "Low" throughout Minnesota.
[see: Fire Danger Rating Map]

Future prospects:

The August precipitation outlook offers equal chances of above, near, and below normal rainfall. August precipitation normals range from under three inches in northwestern and west central Minnesota to over four and one half inches in southeastern counties.
[see: Climate Prediction Center 30-day Outlook | August Precipitation Normal Map]
The August temperature outlook also depicts no significant tendencies away from historical climatological probabilities. Normal August high temperatures are around 80 degrees to start the month, dropping to the mid-70s by month's end. Normal lows are around 60 degrees early in the month, falling to the mid-50s by late August.
[see: Climate Prediction Center 30-day Outlook | August Temperature Normal Map]
The 90-day precipitation outlook for August through October shows no significant tendencies away from climatological probabilities except for a tilt towards above-normal rainfall in far southwestern Minnesota. The August through October temperature projection leans towards below-normal conditions statewide.
[see: Climate Prediction Center 90-day Outlook]
The National Weather Service produces long-range probabilistic river stage and discharge outlooks for the Red River, Minnesota River, and Mississippi River basins. These products are part of the National Weather Service's Advanced Hydrologic Prediction Service (AHPS).
[see: National Weather Service River Forecast Center]

From the author:

Last week, DNR Waters released the first installment of a new monthly product that provides general information on the quantitative status of water resources across Minnesota. The monthly Hydrologic Conditions Report places current measurements of precipitation, stream flow, lake levels, and ground water levels in historical context.
[see: DNR Waters Monthly Hydrologic Conditions Report]

Notes from around the state:

None

Upcoming dates of note:

August 20: National Weather Service releases 30/90 day temperature and precipitation outlooks

Web sites featured in this edition:

http://climate.umn.edu - Minnesota Climatology Working Group, Minnesota DNR Waters and U of M Dept. of Soil, Water, and Climate
http://www.drought.unl.edu - National Drought Mitigation Center
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey
http://mndnr.gov/waters - Minnesota Department of Natural Resources, Division of Waters
http://www.lre.usace.army.mil - US Army Corps of Engineers, Detroit District
http://www.nass.usda.gov - USDA, National Agricultural Statistics Service
http://mndnr.gov/forestry - Minnesota Department of Natural Resources, Division of Forestry
http://www.cpc.ncep.noaa.gov - National Weather Service, Climate Prediction Center
http://www.crh.noaa.gov/ncrfc - National Weather Service, North Central River Forecast Center

Acknowledgements

None

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