Minnesota Drought Situation Report - September 20, 2007

Drought Monitor - September 18, 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 one notable change from the previous week's map. The Severe Drought polygon in north central Minnesota was extended westward to depict the very dry conditions reported in these areas since mid-July.

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.

This week's weather:
The data deadline for the weekly U.S. Drought Monitor is Tuesday mornings at 7:00 AM CDT. Therefore, this week's Drought Monitor was produced without accounting for heavy rains on Tuesday, September 18 and Thursday, September 20. Precipitation totals of one to four inches have been reported in some of the most drought-stricken areas of Minnesota. It is still raining in these areas as of this writing. Next week's Drought Monitor will reflect these events and categorical improvements are likely. Radar-based rainfall estimates for this week's events can be viewed at http://water.weather.gov

Weekly Precipitation Map Last week's weather:
Rainfall totals for the week ending Monday morning, September 17 were generally less than one third of an inch in most Minnesota communities (see map at left). Sections of far northern Minnesota and far southeastern Minnesota received more than one half inch of rain. Long-term average rainfall rates rainfall totals are beginning to drop off at this time of year to around one half inch per week. Temperatures last week were very cool, averaging eight to ten degrees below normal. Most locations reported their first frost of the autumn last week.

Summer Dryness (June 5 - September 17):
Dryness has been entrenched across north central, northeastern, west central, and central Minnesota for much of the summer. Rainfall for the fifteen-week period from June 5 through September 17 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 seven or more inches short of the historical average (see map below). When compared with historical rainfall totals for the same fifteen-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 17 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 the heart of the summer 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 17 2007 Precipitation June 5 to September 17 2007 Precipitation Departure Map June 5 to September 17 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_070920.htm
Last modified: September 20, 2007