HydroClim Minnesota - October 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 10/7/2009

What happened in September:

September 2009 rainfall was very light across much of Minnesota. Monthly rainfall totals fell short of historical September averages by one to three inches in the eastern two-thirds of the state. Some east central and southeastern Minnesota communities received no measureable rainfall during the first three weeks of the month. Rainfall deficits, along with very warm September temperatures, amplified the drought situation in many locations..
[see: September 2009 Climate Summary Table | September 2009 Precipitation Departure Map]
Although this product is intended to summarize September 2009 climate conditions, a notable turn of events during the first week of October must be mentioned. Over three inches of rain has fallen thus far in October across much of the southern two-thirds of Minnesota. The heavy rains have substantially eased many concerns regarding soil moisture deficits that would have impacted agricultural, horticultural, and forestry interests in spring 2010.
[see: Total Rainfall - October 1 through 7]
Monthly mean temperatures for September 2009 were very warm, averaging four to eight degrees above the historical average. It was Minnesota's fifth warmest September on record, even though the month ended with record-setting cold days. The warm September temperatures contrasted with the seasonally cool temperatures that persisted through the summer. Extreme temperature values for September ranged from a high of 88 degrees at Marshall on the 18th, to a low of 20 degrees in Embarrass (St. Louis County) on the 30th. Many low temperature records were set in northern Minnesota during the morning of September 30. Interestingly enough, no high temperature records were set during September in spite of the persistently warm weather during the first three weeks of the month.
[see: September 2009 Climate Summary Table]

Where we stand now:

The U. S. Drought Monitor, released on October 1, placed areas of east central Minnesota in the Severe and Extreme categories. An area of north central Minnesota, centered on the Mississippi headwaters region, was also depicted as experiencing Severe drought. Elsewhere across the state, many counties were described as Abnormally Dry or undergoing Moderate drought. The drought designations are the result of two spells of dry weather, one during this year's growing season, and one longer-term. The shorter-term dryness began in April 2009 and persisted through September over nearly all of Minnesota. April through September precipitation totals in many locations fell short of the historical average by more than four inches. The longer-term dry spell commenced in mid-June 2008 and most profoundly affects east central Minnesota. In this area, 16-month precipitation deficits of ten or more inches have led to a significant impact on hydrology. The U.S. Drought Monitor product to be released on October 8 will reflect the impacts of the heavy early-October rains. Large-scale categorical changes can be expected. The U. S. Drought Monitor index is a blend of science and subjectivity where drought categories (Moderate, Severe, etc) are based on several indicators.
[see: Drought 2009]
DNR Waters and the U.S. Geological Survey report that stream discharge values for roughly 15 percent of Minnesota measurement sites rank below the 25th percentile in the historical data distribution for the date. Some measurements fall below the 10th percentile when compared with historical early-October values. Some of the lowest stream flow values, relative to historical data, are observed along the upper reaches of the Mississippi River and in northeastern Minnesota. By contrast, very high seasonally-weighted stream flow values are reported along the Red River and the upper Minnesota River.
[see: USGS Stream Flow | DNR Stream Flow]
The Lake Superior water level is up one inch from last year at this time but remains below the long-term average. Water levels on many south central and east central Minnesota lakes are very low. White Bear Lake, on the Ramsey/Washington county border, is near its all-time recorded low level.
[see: Corps of Engineers Great Lakes Water Levels | White Bear Lake Water Level]
The Minnesota Agricultural Statistics Service reports that as of October 4, topsoil moisture was 4% "Very Short", 13% "Short", 70% "Adequate", and 13% "Surplus". Additional rain falling after the October 4 reporting deadline continued to bolster soil moisture supplies.
[see: Agricultural Statistics Service Crop Progress and Condition]
The potential for wildfires is currently rated by DNR Forestry as "Low" across Minnesota.
[see: Fire Danger Rating Map]

Future prospects:

The October precipitation outlook tilts towards above-normal precipitation in the southern two-thirds of Minnesota. Events during the first week of the month have already validated this projection. Elsewhere, the outlook offers equal chances of above, near, and below normal precipitation. 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.
[see: Climate Prediction Center 30-day Outlook | October Precipitation Normal Map]
The October temperature outlook depicts no significant tendencies away from historical climatological probabilities. Normal October high temperatures fall from the low to mid 60s early in the month, to the upper 40s by month's end. Normal October low temperatures drop from the low 40s early in the month to near 30 by late October.
[see: Climate Prediction Center 30-day Outlook | October Temperature Normal Map]
The 90-day precipitation outlook for October through December shows no significant tendencies away from climatological probabilities. The October through December temperature projection indicates a strong tendency towards above-normal temperatures.
[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:

Please join us for the 17th Annual Kuehnast Lecture in Meteorology and Climatology on October 15. This year's guest lecturer is Dr. Dennis Baldocchi from the University of California - Berkeley. His topic: Breathing of the Biosphere: How Physics Sets the Limits and Biology Does the Work.
[see: 17th Annual Kuehnast Lecture]
The DNR Division of Waters prepares a monthly product providing 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:

October 15: National Weather Service releases 30/90 day temperature and precipitation outlooks
October 15: 17th Annual Kuehnast Lecture

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://water.weather.gov - National Weather Service, Advanced Hydrologic Prediction Service
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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