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Extension > Mark Seeley's WeatherTalk > Dryness continuing into September

Friday, September 7, 2012

Dryness continuing into September

Dryness continuing into September

Not only was the 12-day run of the State Fair dry (only .08 inches), but the drought picture worsened across the state according to the latest US Drought Monitor. Some southwestern and south-central counties (9 in total) were placed in the Extreme Drought category this week, while many others continued to be in the Severe Drought category (another 23 counties). Little widespread rainfall has occurred across the state since the week of August 22nd. Normal amounts of September rainfall range from 2.50 to 3.50 inches, but the first week of September brought little relief to most places. Only Orr (1.12"), Rushford (1.15"), Lake City (1.16"), Preston (1.34"), and Lanesboro (1.40") reported over an inch during the first week, while Caledonia received 2.57 inches. Much of this fell with the thunderstorms that crossed the state on September 4th bringing high winds and hail to many areas.

Minnesota Agricultural Statistics reports that topsoil moisture is short or very short for 63 percent of their respondents, and measured soil moisture values in the top five feet of soil at the University of Minnesota Research and Outreach Centers remains historically low for this time of year.

Signals of warmth

Pete Boulay of the MN State Climatology Office pointed out this week that the Twin Cities climate record for this year show 30 days with a daytime maximum temperature of 90 degrees F or higher. The annual average is about 13 days, and further this is the most since 1988 when there were 44 such days. Currently the 30 days with 90 F or better ties for 9th in the Twin Cities climate records back to 1871. You can read more about this here.

Another interesting signal of warmth is the number of nights that the temperature has not fallen below 70s degrees F in the Twin Cities. This year that number is 23 nights. Further, this is the 7th year since 2001 (58 percent of all years) that 20 or more nights have not seen the overnight low drop below 70 degrees F. Such occurrences used to be a rarity, as from 1871 to 1999 (129 years) there were only 12 years when the number of nights that remained at 70 F or above totaled 20 or more (about 8 percent of all years). This is a striking shift in climate pattern that may be associated with both urbanization and climate change.

Fall brings mixed emotions

The month of September brings very perceptible changes....declining day length (roughly 20 minutes per week), falling temperatures (average temperature declines about 3-4 degrees F per week), onset
of foliage color change, and for some areas the first frost.

Many people are concerned about the first fall frost. Those suffering from the high pollen (asthma) would prefer to see a frost soon, while many gardeners hope that a frost holds off until the end of the month or later. Average first frost dates range from the September 7th to the 14th in far northeastern counties to the first and second weeks of October in many southern counties.

Fall color changes are eagerly anticipated by many Minnesota residents who like to admire the beauty of nature in the northern woods or from a drive along some of the major river valleys. The Department of Natural Resources web site keeps abreast of color changes around the state.

The first September overnight lows in the 30s F were reported from Embarrass, Crane Lake, Pine River, and Hibbing on Thursday morning this week. Such temperatures will accelerate the autumn color change in those areas.

Weekly Weather potpourri

The NOAA National Hurricane Center was tracking hurricanes Leslie and Michael (the 12th and 13th named storms this season) over the North Atlantic Ocean this week. Leslie was expected to pass over Bermuda on Monday next week, while Michael is expected to remain far away from any land.

Contrary to most of the central USA, the United Kingdom reported its 2nd wettest summer in history (trailing only 1912). The average June-August rainfall total was nearly 15 inches across that country, following a wetter than normal spring season for most.

Scientists from Cornell University reported this week that the glacial ice fields of southern Patagonia in the Andes of South America are diminishing at an accelerating rate. In southern Chile the volume of runoff released annually from these ice fields in recent years is 50 percent higher than it was prior to the year 2000. You can read more about this study here.

MPR listener question

What was the highest dewpoint in the Twin Cities this summer?

Answer: The highest dewpoint reported from the MSP Airport this summer was 77 degrees F on July 4th. That was a sticky, hot day, as the air temperature reached 101 degrees F and the Heat Index reached 108 degrees F, both setting new 4th of July records for the Twin Cities. The overnight low was also a record warm 81 degrees F. There were 180 hours this summer when the dewpoint in the Twin Cities reached 70 degrees F or higher. This number was not record-setting but was a bit above average.

Twin Cities Almanac for September 7th

The average MSP high temperature for this date is 76 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 56 degrees F (plus or minus 7 degrees F standard deviation).

MSP Local Records for September 7th

MSP weather records for this date include: highest daily maximum temperature of 98 degrees F in 1976; lowest daily maximum temperature of 52 degrees F in 1911; lowest daily minimum temperature of 40 F in 1956; highest daily minimum temperature of 75 F in 2002; and record precipitation of 2.16 inches in 1964.
 
Average dew point for September 7th is 54 degrees F, with a maximum of 75 degrees F in 1985 and a minimum of 34 degrees F in 1956 and 1995.

All-time state records for September 7th

The state record high temperature for this date is 104 degrees F at Wadena (Wadena County) in 1931. The state record low temperature for this date is 20 degrees F at Tower (St Louis County) in 1986. State record precipitation for this date is 4.65 inches at Remer (Cass County) in 1991; and there has not been any snowfall reported on this date.

Past Weather Features:

September 7th brought a Heat Wave to Minnesota in 1931, 1976, and 1978. In 1931 a 7-day Heat Wave began on September 7th bringing multiple 100 degree F days to many areas, the hottest September spell of weather in history, peaking with 111 degrees F at Beardsley on the 11th. In 1976, a shorter 2-day Heat Wave prevailed over September 6-7, bringing 90 F temperatures to dozens of cities, peaking with 104 degrees F at Luverne on the 6th. In 1978 an 8-day Heat Wave prevailed in southern Minnesota counties over September 5-12 bringing consecutive days with 90 F and higher temperatures. The peak of the heat produced 103 degrees F at Montevideo and Redwood Falls on the 7th.

September 7, 1986 brought an early frost to many northern Minnesota communities. Cotton, Tower, Isabella, and Cloquet saw overnight lows fall into the 20s F. Temperatures rebounded in classic Indian Summer fashion and brought daytime highs in the 70s and 80s F for much of the rest of the month that year.

September 6, 1995 brought four tornadoes to Steele and Rice Counties in southern Minnesota. The worst one, an F-2 (winds 113-157 mph), was on the ground for two miles around Morristown. It destroyed a number of farm buildings, overturned some wagons of grain, and damaged a home. Fortunately there were no deaths or injuries.

Outlook

The weekend will start out with near seasonal average temperatures on Saturday, then warm Sunday and Monday. Little chance for rainfall until next Wednesday and Thursday, followed by cooler temperatures.

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