|HydroClim Minnesota - August 2002
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
- with some exceptions, July was a wet month across much of the northern three quarters of Minnesota. Rainfall totals exceeded historical July averages by two or more inches in many locations. Precipitation totals surpassed the normal by four or more inches in sections of west central, central, and east central Minnesota. In the southern one quarter of Minnesota, and in far northeastern Minnesota, July rainfall fell short of normal by about one inch. WHERE WE STAND NOW
- two very intense rainfall events doused Minnesota during the first half of July. In the first event, heavy thunderstorms drifted across central Minnesota on Saturday July 6 and continued in waves into the early morning hours of Monday July 8. The first wave of heavy rain fell on the July 6 when one to four inches fell in east central Minnesota. On Sunday July 7, rainfall totals of two to six inches fell in an arc from Todd County to Pine County. The highest multi-day totals were 10 inches in northern Kanabec County and 9.5 inches in southwestern Aitkin County. In July's second intense downpour, heavy rains fell on northwestern, central, and south central Minnesota on July 9 and 10. Rainfall totals exceeding four inches were reported in some communities. The largest rainfall total from July 9 and 10 was 8.33 inches near Climax in western Polk County. Street flooding was reported in St. Cloud, Sauk Centre, Foley, Fergus Falls, and northern metropolitan Twin Cities suburbs on the morning of the July 10.
- July monthly temperatures were generally two to four degrees warmer than normal around the state. This continued a pattern of warmer than average summertime temperatures established in June. Maximum temperatures topped 90 degrees numerous times during the month of July, and minimum temperatures above 70 degrees were common. The average minimum July temperature in the Twin Cities (68.2 degrees F.) was the fourth warmest in the modern climate record (1891-2002). The sweltering weather reached its peak on July 20 when a handful of locations in west central and southern Minnesota reported dew point temperatures in excess of 80 degrees. The high dew point temperatures combined with air temperatures in the mid-90's to create heat index values topping 110 degrees.
- growing season precipitation totals to date (April 1 - August 5) are very high relative to historical values across a broad band that extends from northwestern Minnesota, through central Minnesota, and into southeastern Minnesota. In these areas, precipitation totals have exceeded historical averages by more than 25 percent for the season. In some northwestern and central Minnesota counties, growing season rainfall totals top historical averages by more than 75 percent. When compared to all other historical data for the same period (April 1 - August 5), precipitation totals for many communities in northwestern, central, and east central Minnesota are near, or above, all-time record values. By contrast, some sections of southwestern, north central, and northeastern Minnesota are reporting rainfall deficits for the season. In a few southwestern and northeastern Minnesota communities, growing season precipitation totals have fallen short of the historical average by 20 to 40 percent.
- as of July 30, the National Drought Mitigation Center - U. S. Drought Monitor shows that nearly all Minnesota counties are free of any drought designation. Far southwestern Minnesota is rated as "Abnormally Dry". The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators.
- the August 3 Palmer Drought Severity Index map from the Climate Prediction Center places central and east central Minnesota in the "Very Moist Spell" category. All other Minnesota counties are in the "Near Normal" category. The Palmer Drought Severity Index is used for assessing long-term meteorological conditions.
(see: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/regional_monitoring/palmer.gif )
- the Minnesota Agricultural Statistics Service reports that as of August 2, the state's topsoil moisture was 5% surplus, 76% adequate, 12% short, and 7% very short. Quantitative soil moisture measurements are rare. However, early-August measurements from University of Minnesota research locations in southern Minnesota indicate that soil moisture values in those areas are near historical averages.
- the U.S. Geological Survey indicates that stream discharge values are high (above the 75th percentile but less than the 90th percentile for the date) over much of the state of Minnesota. Stream flows in some rivers in northeastern, southwestern, and southeastern Minnesota are near historical averages.
- the potential for wildfires is rated as "Low" across nearly all of Minnesota. The fire danger is rated as "Moderate" in portions of Wadena and Cass counties, and rated as "High" to "Very High" in Cook county and the blow-down areas of Lake and St. Louis counties.
- the August precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. August precipitation normals range from just under three inches in northwestern and west central Minnesota to just over four inches in eastern counties. The August temperature outlook also shows no significant tendencies away from climatological probabilities. 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 shows 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 upper 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 climatological data. The climatological data are weighted by the 90 day outlooks for temperature and precipitation trends. The model output offers a complete range of probabilistic values of stream stage and discharge for numerous forecast points. The product offers 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
- noneUPCOMING DATES OF NOTE
- August 15, Climate Prediction Center releases 30/90 day temperature and precipitation outlooks WEB SITES FEATURED IN THIS EDITION
- Minnesota Climatology Working Group
http://www.drought.unl.edu/ - National Drought Mitigation Center
http://www.cpc.ncep.noaa.gov - Climate Prediction Center
http://www.nass.usda.gov/mn - Minnesota Agricultural Statistics Service
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey, Minnesota
- Minnesota DNR Waters
http://www.dnr.state.mn.us/forestry/fire/ - Minnesota DNR Forestry
http://www.crh.noaa.gov/ahps/index.html - National Weather Service - Central Region Headquarters
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