|HydroClim Minnesota - October 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
- September rainfall totals were generally below normal across much of Minnesota, most notably in western and northern sections of the state. In these areas, monthly rainfall totals fell short of the historical average by more than one inch. Exceptions to the general pattern of dryness could be found in central and east central Minnesota, where some communities topped normal by more than two inches. Much of the higher than normal precipitation observed in central and east central Minnesota was due to an intense rainfall event on September 5 and 6. During this event, two waves of thunderstorms deposited three to five inches of rain on portions of Benton, Stearns, Sherburne, Wright, Hennepin, and Dakota counties. The heavy rain led to urban flooding and some road washouts.WHERE WE STAND NOW
- September temperatures were generally above normal for the first half of the month, then cooled to somewhat below average readings during the month's second half. On average, September monthly temperatures finished three to five degrees warmer than the norm. Widespread frost occurred across the state on the morning of September 24.
(see: http://climate.umn.edu/cawap/monsum/monsum.asp ,
- warm season precipitation accumulations to-date (April 1 - October 7) are very high relative to historical values across northwest, central, and east central Minnesota. In these areas, precipitation totals exceeded historical averages by more than 50 percent for the season. In many communities, precipitation totals are near, or above, all-time record values for the April through September period. For some locales in the wettest areas, 2002 annual precipitation totals to-date are already approaching all-time calendar year records.
- as of October 1, 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 October 5 Palmer Drought Severity Index map from the Climate Prediction Center places central and east central Minnesota in the "Extremely Moist" category, the wettest designation. Northwest, south central, and southeast Minnesota are in the "Very Moist Spell" category. North central, and southwest Minnesota fall 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.
- the Minnesota Agricultural Statistics Service reports that as of October 4, the state's topsoil moisture was 20% surplus, 75% adequate, 4% short, and 1% very short.
- the U.S. Geological Survey indicates that stream discharge values are in the normal range for roughly one half of Minnesota's rivers. Streamflows for most of the rivers not in the normal category are high (above the 75th percentile for the date). Stream discharge measured in some northwest, central, east central and southeast Minnesota rivers exceeds the 90th percentile for the date. Discharge values for a few northeast Minnesota streams are low, ranking below the 25th percentile for the date.
- the potential for wildfires is rated as "Low" across nearly all of Minnesota. The fire danger is rated as "Moderate" in Cook county and the "blow-down" areas of Lake and St. Louis counties.
- the October precipitation outlook from the Climate Prediction Center shows no significant tendencies away from climatological probabilities. Normal October precipitation ranges from just over one inch in northwestern Minnesota, to just over two inches in the southeast. (** For many locations in the southern two thirds of Minnesota, early October rains have already matched or exceeded monthly October precipitation normals. **) The October temperature outlook shows no significant tendencies away from climatological probabilities. Normal October high temperatures fall from the low to mid 60's early in the month to the upper 40's by month's end. Normal October lows drop from the low 40's early in the month to the upper 20's by late October.
- the 90-day precipitation outlook for October through December shows no significant tendencies away from climatological probabilities. The October though December temperature outlook shows 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 climatological data. The climatological data are weighted by the 90 day 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
- warmer than average sea surface temperatures presently exist in the eastern and central equatorial Pacific. 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. The present El Niņo is relatively weak, and there is uncertainty in the forecasts about the timing and intensity of its peak. All forecasts indicate that it will be much 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
- noneUPCOMING DATES OF NOTE
- October 11, 10th Annual Kuehnast Lecture WEB SITES FEATURED IN THIS EDITION
- October 17, Climate Prediction Center releases 30/90 day temperature and precipitation outlooks
- 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 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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