|HydroClim Minnesota - August 2001
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
- continuing a dry spell that commenced during the second half of June, July precipitation totals were generally below average across most of Minnesota. Rainfall amounts during July generally fell short of historical averages by one to two inches. For a four week period from June 19 through July 16, precipitation totals were less than one half of normal for much of the state. Some areas received relief from the dryness in the form of spotty rains during the last two weeks of July. The exception to the general dryness has been far northern Minnesota where thunderstorms dropped significant rain in mid-July and again on July 31. A swath of two to six inches of rain was reported from Kittson county east to Cook county in the late July event. The heaviest rain fell in portions of Lake of the Woods, Beltrami, and Koochiching counties, where five inch storm totals were common.
- July average temperatures finished slightly above historical averages. However, the near normal monthly means were the result of very warm mid-month and month-end temperatures offsetting cool early July weather. Most of Minnesota suffered through three significant episodes of extreme humidity and heat (July 17-18, July 30 - August 1, August 4-8) in recent weeks. During these sultry spells; temperatures climbed into the 90's, dewpoint temperatures reached the upper 70's, and heat index values exceeded 100 degrees.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp ,
WHERE WE STAND NOW
- as of August 6, growing season precipitation totals (beginning April 1) continue to exceed 125 percent of normal across much of the state. In most areas, the above normal growing season rainfall reflects the lingering impact of the extremely wet spring. Due to very heavy late July rainfall, growing season precipitation totals exceed 150 percent of normal in many far northern Minnesota communities. Precipitation totals are near or above all-time records for the April through early August period in sections of north central and northeastern Minnesota. By contrast, portions of northwestern and north central Minnesota have received less than average growing season rainfall. Additionally, growing season precipitation shortfalls are developing in sections of central and southeastern Minnesota.
(see: http://climate.umn.edu/doc/weekmap.asp ,
- as of their August 9 release, the National Drought Mitigation Center classifies central and east central Minnesota in their "DO" category ("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 4 Palmer Drought Severity Index (PDSI) depicts southwestern and south central Minnesota as undergoing an "Unusual Moist Spell". The remainder of Minnesota falls in the "Near Normal" category. The Palmer Drought Severity Index is used for assessing long-term meteorological conditions.
- the Minnesota Agricultural Statistics Service reports that topsoil moisture as of Friday, August 3 was rated 12% surplus, 51% adequate, 27% short, and 10% very short. As of August 3, crop conditions were primarily rated as fair to good. However, in spotty areas with precipitation deficits, or for crops planted in coarse textured soils, crop stress is apparent and yield reductions are possible.
- the U.S. Geological Survey indicates that stream flows in northwestern, north central, and some sections of northeastern Minnesota rank above the 90th percentile for the date. For some streams in northwestern and north central counties, flows are at all-time highs for the date. Elsewhere, streams are primarily in the normal category (between the 25th and 75th percentile).
- the potential for wildfires is rated "moderate" in areas of central, north central, eastern central, and northeastern Minnesota. The fire danger is rated "high" in the blow-down areas of northeastern Minnesota. Elsewhere across Minnesota, fire danger is characterized as "low". Conditions have improved markedly from early July when some northern Minnesota counties ranked in the "very high" to "extreme" fire danger category.
(see: http://www.dnr.state.mn.us/forestry/fire/ )
- the August precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. August precipitation normals range from near three inches in western Minnesota to just under four inches in the eastern half of the state. 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 and Minnesota 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 will be produced near the middle of each month. The AHPS service will be available for the Mississippi River Basin in the autumn of 2002.
(see: http://www.crh.noaa.gov/fgf/ahps/ahpsmain.htm for the Red River basin,
http://www.crh.noaa.gov/mpx/ahps/ for the Minnesota River basin)
FROM THE AUTHOR
NOTES FROM AROUND THE STATE
UPCOMING DATES OF NOTE
- August 16, Climate Prediction Center releases 30/90 day temperature and
WEB SITES FEATURED IN THIS EDITION
http://climate.umn.edu - Minnesota Climatology Working Group
http://enso.unl.edu/ndmc/ - 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/daily_flow?mn - U.S. Geological Survey, Minnesota
http://www.dnr.state.mn.us/forestry/fire/ - Minnesota Department of Natural Resources - Division of
Forestry http://www.crh.noaa.gov/fgf - National Weather Service Forecast Office - Grand Forks
http://www.crh.noaa.gov/mpx - National Weather Service Forecast Office - Chanhassen
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