Minnesota Drought Situation Report - August 7, 2007

Drought Monitor - July 31, 2007
Drought Monitor Map
Drought Monitor Legend

Drought Status
The latest U. S. Drought Monitor (see map at right) places portions of northeastern Minnesota, and most of the southern one half of Minnesota, in the Severe Drought category. With the exception of northwestern counties, the remainder of Minnesota is classified as experiencing a Moderate Drought or depicted as being Abnormally Dry. 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 southern two thirds 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:
Welcome rain fell this past Saturday across the southern three tiers of Minnesota counties. Rainfall totals ranged between one and two inches in these areas (see map at left). Unfortunately, the weekend rain does not markedly change the overall drought picture. The water will be quickly consumed by the mature row crops that dominate the landscape in southern Minnesota. Elsewhere in Minnesota, rainfall was very light last week, totaling less than one-quarter inch in most locales. The lack of rainfall in these areas worsened an already serious situation. Weekly temperatures were generally above the long-term mean last week.

Seasonal weather overview:
Dryness has been entrenched across the southern two thirds of Minnesota for much of May, June, July, and early August. Rainfall for the eight-week period from June 5 through July 30 totaled less than three inches over much of the southern two thirds of Minnesota (see map below). In most of these areas, rainfall totals for the period were four or more inches short of the historical average (see map below). When compared with historical rainfall totals for the same eight-week time frame, 2007 values ranked at or below the 5th percentile for many central and southern Minnesota counties (see map below). In a few areas, the June 5 - July 30 rainfall totals were near all-time record low values. The timing of the dry weather is unfortunate. 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, has led to deteriorating crop conditions, lower stream flows and lake levels, and increased wildfire danger.

June 5 to July 30 2007 Precipitation June 5 to July 30 2007 Precipitation Departure Map June 5 to July 30 2007 Precipitation Ranking Map

Growing Season (April 1 to present) precipitation totals, departure, and ranking:
Rainfall totals since April 1 are less than nine inches across much of central Minnesota (see map below). Growing season rainfall totals have deviated negatively from historical averages by more than four inches across many central, east central, southwestern, and south central Minnesota counties (see map below). This is roughly the equivalent of missing all of June's rainfall. Seasonal rainfall deficits exceeding six inches are reported in a band that extends from Litchfield in central Minnesota eastward into portions of the Twin Cities metropolitan area. Six-inch shortfalls are also in place in some south central Minnesota counties. When compared with other seasonal rainfall totals-to-date in the historical database, this year's rainfall for the season ranks just above the 10th percentile (one year in ten occurrence) in many southern Minnesota counties (see map below).

April 1 to August 6 2007 Precipitation Map April 1 to August 6 2007 Precipitation Departure Map April 1 to August 6 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_070807.htm
Last modified: August 7, 2007