Minnesota Drought Situation Report - August 16, 2007
(August 14 report modified for recent changes in U. S. Drought Monitor)

Drought Monitor - August 14, 2007
Drought Monitor Map
Drought Monitor Legend

Drought Status
The latest U. S. Drought Monitor (see map at right) now places Minnesota's Arrowhead region and portions of central Minnesota in the Extreme Drought category. This is a one-category deterioration of drought conditions from the previous week. This week's map shows improvement in drought conditions in southeastern Minnesota. Overall, the U.S. Drought Monitor continues to depict much of northeastern Minnesota and most of the southern one half of Minnesota in the Severe Drought category. Elsewhere in Minnesota, most areas are classified as experiencing a Moderate Drought or described 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 Friday and Saturday across sections of central and southeastern Minnesota. Rainfall totals ranged between one and two and one half inches in these areas (see map at left). Small sections of northwestern and north central Minnesota also received more than one inch of rain for the week. Elsewhere in Minnesota, rainfall was spotty, totaling less than one-quarter inch in most locales. Monday evening rain, occurring after the Monday morning map deadline, exceeded one inch in many central, east central, and southeastern Minnesota counties. In some east central Minnesota counties, rainfall totals topped two inches in this event. Weekly temperatures were generally above the long-term mean last week.

The combined impact of the Saturday and Monday rain events kept the drought situation from deteriorating further in central Minnesota, and greatly improved drought conditions in southeastern Minnesota. The situation continues to worsen in southwestern and south central Minnesota, and in far northeastern Minnesota.

Mid-summer Dryness:
Dryness has been entrenched across most of Minnesota for much of the summer. Rainfall for the ten-week period from June 5 through August 14 totaled less than four inches in many locations in the southern two thirds of Minnesota (see map below). In these areas, rainfall totals for the period were five or more inches short of the historical average (see map below). When compared with historical rainfall totals for the same ten-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 - August 14 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, led to deteriorating crop conditions, lower stream flows and lake levels, and increased wildfire danger.

June 5 to August 14 2007 Precipitation June 5 to August 14 2007 Precipitation Departure Map June 5 to August 14 2007 Precipitation Ranking Map

Growing Season (April 1 to present) precipitation totals, departure, and ranking:
Rainfall totals since April 1 are less than ten inches across portions of central, east central, and southwestern 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 spotty areas of central, east central, and south central Minnesota. 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 counties in the southern two thirds of Minnesota, and portions of Minnesota's Arrowhead region (see map below).

April 1 to August 13 2007 Precipitation Map April 1 to August 13 2007 Precipitation Departure Map April 1 to August 13 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_070816.htm
Last modified: August 16, 2007