|HydroClim Minnesota - December 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
- precipitation in November was extraordinarily light across all of Minnesota. November precipitation totals ranged from only a trace at Olivia to 0.47 inches at Alexandria. Precipitation totals for the month fell short of historical averages by one to two inches. In many communities, November 2002 was among the driest Novembers on record.WHERE WE STAND NOW
- November mean temperatures were within one degree of historical averages in most locales. Temperatures in northeastern Minnesota were a bit cooler, averaging around three degrees below normal. Temperature extremes ranged from -17 degrees at Embarrass on November 26, to 69 degrees at Canby, Morris, and Montevideo on November 8.
- as of November 27, a modest snow cover blanketed portions of north central and northeast Minnesota. Two to four inches of snow depth was reported east and north of a line from Roseau to Wadena to just north of Duluth. Portions of Lake and St. Louis counties had four to eight inches of snow on the ground. The snow cover pattern and depths are consistent with historical averages with the exception of the north shore of Lake Superior. Snow depths along the Lake Superior highlands typically exceed 10 inches by November 30. A lack of on-shore winds have thus far inhibited "lake effect" snowfalls.
- as of November 26, the National Drought Mitigation Center - U. S. Drought Monitor shows that all Minnesota counties are free of drought designation. The NDMC index is a blend of science and subjectivity where intensity categories are based on six key indicators and numerous supplementary indicators.
- the November 30 Palmer Drought Severity Index map from the Climate Prediction Center places central Minnesota in the "Extremely Moist" category, their wettest designation. East central Minnesota falls in the "Very Moist Spell" category. Northwest, south central, and southeast Minnesota are in the "Unusual Moist Spell" category. Other Minnesota regions are classified as "Near Normal". The Palmer Drought Severity Index is used for assessing long-term meteorological conditions.
- in their final report of the season, the Minnesota Agricultural Statistics Service indicates that as of November 22, the state's topsoil moisture was 7% surplus, 91% adequate, and 2% short. Subsoil moisture conditions were rated 12% surplus, 84% adequate, and 4% short.
- the U.S. Geological Survey indicates that stream discharge values are in the normal range for roughly 60 percent of Minnesota's rivers. Streamflows in most rivers not in the normal category are high (above the 75th percentile but below the 90th percentile for the date). Discharge values for a few northeast Minnesota streams are low, ranking below the 25th percentile for the date.
- soil temperatures near the surface are now at or below freezing across all of Minnesota. Frost depths under sod are around 6 to 8 inches in the north, 2 to 4 inches in the south. Frost depths under bare soil are a few inches deeper. Soil frost typically reaches maximum depth in late February.
(see: http://climate.umn.edu/doc/observatory.htm , http://www.mvp-wc.usace.army.mil/projects/reservoirs.shtml
- nearly all of Minnesota's smaller and shallower lakes are ice covered. Most of Minnesota's larger lakes have sizeable areas of ice cover. High winds over the Thanksgiving holiday weekend opened some lakes in western and southern Minnesota, but frigid temperatures led to a quick refreeze. Ice thickness is highly variable and ice safety remains marginal.
- the DNR Wildfire Information Center reports that the potential for wildfires is rated as "Low" across all of Minnesota.
- the December precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. December precipitation normals range from around one half inch in western Minnesota to just over one inch in eastern sections of the state. The median snow cover at the end of December ranges from over 10 inches on the ground in northeastern Minnesota (20 inches in the Lake Superior highlands), to under 5 inches in the southwest. Normal December high temperatures are in the mid-20's to upper 20's to start the month, dropping to the near 20 by month's end. Normal lows are around 10 degrees early in the month, falling to near zero by late December.
- the 90-day precipitation outlook for December through February shows no significant tendencies away from climatological probabilities for the western three-fourths of Minnesota. The 90-day precipitation outlook for eastern counties tilts towards below normal conditions. The December though February temperature outlook indicates a strong bias towards above normal conditions.
- 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 historical climatological data. The climatological data are weighted by 90-day climate outlooks for temperature and precipitation trends. Model output offers a complete range of probabilistic values of stream stage and discharge for numerous forecast points. The product provides 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
- (repeated from last month) warmer than average sea surface temperatures presently exist in the eastern and central equatorial Pacific Ocean. This phenomenon, known as "El Niņo", can have a significant influence on winter weather in the United States and elsewhere. In Minnesota, El Niņos correlate highly with above normal winter temperatures, but have little correlation with winter snowfall totals. At present, the conditions are indicative of a moderate El Niņo episode. All forecasts indicate that this episode will be weaker than the 1997-1999 El Niņo event, and therefore the corresponding impacts should be weaker than those observed during the winters of 1997-1998 and 1998-1999.
NOTES FROM AROUND THE STATE
- from Terry Lejcher, DNR Waters Area Hydrologist - Fergus Falls UPCOMING DATES OF NOTE
(November 12) The first full week in November saw some reopening of our small wetlands and shallow bays in the lakes as it was mild. On Sunday November 10, we had another narrow band of snow amounting to only 1.5 inches accumulate about 5 miles south of Fergus Falls and in an east-west direction for an unknown distance. The water temperature on Otter Tail Lake was 38.5 degrees on November 9.
- December 19, 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://swroc.coafes.umn.edu/ - University of Minnesota - Southwest Research and Outreach Center
http://water.usgs.gov/cgi-bin/dailyMainW?state=mn&map_type=weekd - U.S. Geological Survey, Minnesota
- Minnesota DNR
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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