Minnesota Drought Situation Report - September 13, 2007

Drought Monitor - September 11, 2007
Drought Monitor Map
Drought Monitor Legend

Drought Status
The latest U. S. Drought Monitor (see map at right) places portions of Minnesota's Arrowhead region and portions of central Minnesota in the Extreme Drought category. Much of the rest of the northern two-thirds of Minnesota falls in the Severe Drought or Moderate Drought designation. Most of northwestern Minnesota is described as being Abnormally Dry. This week's Drought Monitor map includes two notable changes from the previous week's map. Drought conditions in sections of northeastern Minnesota were improved by one to two categories due to a heavy rain event on Thursday, September 6. By contrast, conditions continue to deteriorate in west central Minnesota. A one-category decline in drought conditions is indicated for portions of Becker, Otter Tail, and Wadena counties.

The drought situation in the northern one third of Minnesota is the result of the lingering impacts of a very dry 2006, a snow-sparse 2006-2007 winter, and dry 2007 mid-summer weather. The drought situation in the central third of Minnesota is due to an extremely dry 2007 growing season (see: 12-week U.S. Drought Monitor animation).

The U. S. Drought Monitor index is a blend of science and subjectivity where intensity categories are based on several indicators.

Weekly Precipitation Map Last week's weather:
Rainfall totals for the week ending Monday morning, September 10 were quite large in northeastern Minnesota (see map at left). All, or most, of Koochiching, Itasca, St. Louis, Lake, and Cook counties reported at least two inches of rain for the week. Five or more inch totals were common in central St. Louis, northern Lake, and western Cook counties. In drought-stricken areas of west central Minnesota, rainfall totals for the week were small, generally less than one quarter of an inch. Sections of already-soggy southeastern Minnesota received one to three inches of rain last week. Temperatures last week were very warm, averaging three to eight degrees above normal. Many locations reported at least one temperature of over 90 degrees.

Summer Dryness (June 5 - September 10):
Dryness has been entrenched across north central, northeastern, west central, and central Minnesota for much of the summer. Rainfall for the fourteen-week period from June 5 through September 10 totaled less than six inches for many locations in west central and central Minnesota (see map below). In these areas, rainfall totals for the period were six or more inches short of the historical average (see map below). When compared with historical rainfall totals for the same fourteen-week time frame, 2007 values ranked at or below the 5th percentile (one year in twenty occurrence) for many counties (see map below). In a few areas, the June 5 - September 10 rainfall totals were near all-time record low values. The period from May through September is historically the wettest time of the year in Minnesota. Long-term average rainfall rates during this time interval are around one inch per week. Very dry weather, occurring during a time of year when ample rain is typical, leads to the rapid intensification of drought. The lack of precipitation, along with very high evaporation rates, led to deteriorating crop conditions, lower stream flows and lake levels, and increased wildfire danger.

June 5 to September 10 2007 Precipitation June 5 to September 10 2007 Precipitation Departure Map June 5 to September 10 2007 Precipitation Ranking Map

Sector briefs:

More drought information resources are found at http://climate.umn.edu/doc/journal/drought_information_resources.htm.

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URL: http://climate.umn.edu/doc/journal/drought_situation_report_2007_070913.htm
Last modified: September 13, 2007