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Extension > Mark Seeley's WeatherTalk > September 2012

Friday, September 28, 2012

Preliminary September climate summary

Preliminary September climate summary

Mean monthly temperature values for most southern Minnesota observers ranged from 1 to 2 degrees F warmer than normal, while several northern Minnesota communities reported monthly means that were 1 to 2 degrees F cooler than normal. The extremes for the month were 98 degrees F at Brownton (McLeod County) on the 12th and just 16 degrees F at Warroad on the 21st. Many observers reported overnight lows in the teens and 20s F and some reported new record lows (for example 19 F at Warroad on the 18th and 16 F there on the 21st were both new daily record lows). Killing frosts were widespread in nearly all areas during the month, but crops were fully mature and suffered little damage. Minnesota reported the coldest temperature in the 48 contiguous states on six days during the month.

The real story for September was the dryness due to absence of rainfall. Many observers reported measurable rainfall amounts on only 2-3 days, resulting in one of the driest Septembers in history on a statewide basis. The driest September was 1952 when the statewide average rainfall was just 0.57 inches. This year's statewide value will be close to that one. Many observers clearly reported their driest September in history, including Windom (0.30"), Moorhead (0.19"), Willmar (0.14"), Collegeville (0.08"), and Morris (0.03"). For Morris and Collegeville it was one of their driest months in history as well.

At the University of Minnesota Research and Outreach Centers located at Crookston, Morris, and Lamberton, measured stored soil moisture values in the top 5 feet of soil were at or below the all-time lowest values ever measured for the end of September. In addition the flow volume measured on many Minnesota rivers was below the historical 10th percentile, indicating extremely low water levels.

As of the end of September the U.S. Drought Monitor placed all or parts of 45 Minnesota counties in severe to extreme drought, most notably in southwestern, south-central and northwestern Minnesota. In total over 35 percent of Minnesota's landscape was designated to be in severe or extreme drought, the largest fraction of the state since the fall of 2006. The only Minnesota county not designated to be drier than normal is Cook in the far northeast.

The DNR reports very high wildfire danger ratings in many western and northwestern counties. A number of counties in northwestern and north-central Minnesota have burning restrictions in place. The National Weather Service issued a number of Red Flag Warnings during the month due to high fire danger ratings. Wild fires were reported this week near Warroad, Park Rapids, Cloquet and Little Falls.

Peak wind gusts over 40 mph were reported from a number of observers during September. Rochester reported peak winds of 55 mph on September 4-5.

Weekly Weather potpourri

From Brad Rippey, Office of the USDA Chief Economist, USA highlights for the drought-monitoring period ending on September 25 include:
-Nearly two-thirds (65.45%) of the contiguous U.S. is in drought. This is a new U.S. Drought Monitor record (January 2000 to present).
-Corn in drought stands at 84%, down from a July peak of 89%.
-Soybeans in drought are at 80%, down from a July high of 88%.
-Hay in drought continues to rise (currently 69%), due to the westward shift of the core drought area into the Plains’ major hay production areas.
-Cattle in drought continues to rise (currently 76%), due to the westward shift of the core drought area into the Plains’ major cattle areas.
-Winter wheat in drought stands at 73%. Nationally, planting is one-quarter (25%) complete. Soil moisture shortages are most acute across the northwestern half of the Plains.

NOAA is seeking citizen interested in helping to classify the intensity of historical tropical storms and hurricanes. In a project titled CycloneCenter.org NOAA describes the need for citizens to analyze color-enhanced satellite images from 30 years of tropical storm monitoring. They hope to use the resulting data sets to gain a better understanding of the intensification and dissipation of tropical storms and enhance forecasting capabilities. If you want to participate in the CycloneCenter.org project you can learn more about it here.

Super Typhoon Jelawat was spinning in the western Pacific Ocean this week off the east coast of Taiwan. It was producing winds of 150 mph with higher gusts, and sea wave heights near 50 feet. The storm is expected to bring high seas, strong winds and heavy rains to Kyoto, Japan this coming weekend.

The NOAA Storm Prediction Center has filed only 26 reports of tornadoes in the USA so far in September. This is less than half the historical average for September and continues the trend of low tornado numbers that started in the month of July. The record lowest year for September tornadoes in the USA was 1952 when only 1 report was filed.

An article published this week in Science provides an analysis of paleo-climates in Utah and Nevada (14,000 to 20,000 years ago) that supports the hypothesis that a stronger summer monsoon season in the desert southwest fed and maintained the massive glacial lakes that were on the landscape then. Clearly the North America weather pattern was vastly different when ice occupied much of Canada. In this wetter period the earliest settlements were established by native people in much of the desert southwest. You can read more about this study here.

MPR listener question

You mentioned the high winds observed around the state this year. But have there also been an unusual number of days with south or southeast winds?

Answer: Examining the climate of wind direction for southern Minnesota using monthly wind roses, I find that wind blows from the south to southeast direction about 20 to 30 percent of the time during the April through September period. The peak month for southeast winds is August. Taking the data from this year (2012) south to southeast winds were more frequent and stronger than average during the months of April, May, June, and July this year. The S-SE winds have been less frequent than average during August and September. The peak strength of south-southeast winds occurred in May and June as several days brought winds from that direction at peak wind speeds over 40 mph.

Twin Cities Almanac for September 28th

The average MSP high temperature for this date is 65 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 45 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 28th

MSP weather records for this date include: highest daily maximum temperature of 91 degrees F in 1898; lowest daily maximum temperature of 43 degrees F in 1908; lowest daily minimum temperature of 26 F in 1942; highest daily minimum temperature of 64 F in 1905; and record precipitation of 1.21 inches in 1891; Record snowfall is a trace in 1907 and 1945.

Average dew point for September 28th is 44 degrees F, with a maximum of 70 degrees F in 1971 and a minimum of 24 degrees F in 1942.

All-time state records for September 28th

The state record high temperature for this date is 97 degrees F at Argyle (Marshall County) in 1952. The state record low temperature for this date is 15 degrees F at Pipestone (Pipestone County) and Tower (St Louis County) in 1899 and at Grand Rapids (Itasca County) and Alborn (St Louis County) in 1942. State record precipitation for this date is 3.65 inches at St Peter (Nicollet County) in 1901; and the state record snowfall for this date is 2.0 inches at Ada (Norman County) and Detroit Lakes (Becker County) in 1899.

Past Weather Features:

An early season snow storm crossed northern Minnesota on September 28, 1899 bringing snow from Fergus Falls to Mount Iron in the northeast. Ada, Park Rapids, Moorhead, and Detroit Lakes all received over 1 inch of new snow. Following the snow storm, temperatures plummeted into the teens F in some areas.

Thunderstorms brought heavy rain to parts of southern Minnesota on September 28, 1901. Fairmont and Winnebago received over 1.50 inches of rainfall, while St Peter received a record-setting 3.65 inches.

September of 1952 was the driest in state history. In addition over the 27th and 28th strong south winds brought unusually warm weather for so late in the season. Over 20 Minnesota communities saw the mercury reach 90 degrees F or greater over these two days. There were a number of wild fires reported that month.

September 28-29, 1965 brought thunderstorms and heavy rains to southern Minnesota. Over 2 inches of rainfall was reported in Winona, Spring Grove, Preston, Lanesboro, Austin, Caledonia, Slayton, and Bricelyn. Over 4 inches of rain fell in Harmony, producing some local street flooding. In fact Harmony reported their wettest September in history with 13.43 inches of rainfall.

Outlook

Warm and dry, with plenty of sunshine to end the month of September this weekend. And warm early next week as well, with a chance for showers in the northeast. Much cooler by Thursday and Friday as a more fall-like air mass invades the region.

Friday, September 21, 2012

Cold temperatures, dry air

Cold temperatures, dry air

Both Tuesday and Wednesday brought cold temperatures to many northern Minnesota communities. High pressure, clear skies, and a dry air mass were conducive to significant overnight drops in temperature. Some communities set new low temperature records, including

For Tuesday, September 18th:
32 degrees F at Grand Forks, ND
28 degrees F at Wright
27 degrees F at Floodwood
26 degrees F at Kabetogama
24 degrees F at Orr
22 degrees F at Hibbing
21 degrees F at Babbitt
20 degrees F at International Falls and Embarrass
19 degrees F at Warroad (this was the lowest reading in the nation on September 18th)

For Wednesday, September 19th:
27 degrees F at Silver Bay and Grand Marais
25 degrees F at Kabetogama
23 degrees F at Orr
21 degrees F at Warroad
20 degrees F at Embarrass (this was the lowest in the nation on September 19th)

The air was so dry that dewpoints were in the low 20s F, far more typical of late November than mid-September. After relative humidity in many places ranged from 20 to 30 percent. As a result of the very dry air and windy conditions during the day, the National Weather Service issued a number of Red Flag warnings this week around the state.

More overnight temperatures in the 20s and 30s F are expected over the coming weekend.

Windy Wednesday

A moderately strong low pressure system passing across southern Canada on Wednesday brought high winds to Minnesota. Most locations reported winds up to 30 mph or greater, while a few saw winds exceed 40 mph. Those reporting winds between 40 and 45 mph included Glenwood, Park Rapids, Detroit Lakes, Thief River Falls, Madison, Willmar, and Windom. Winds were strong enough to temporarily stop field harvesting of the corn crop in some areas during the late afternoon period.

New climate outlooks

On Thursday of this week the NOAA Climate Prediction Center issued new seasonal climate outlooks. The temperature outlook for Minnesota favors above normal values over the October-December period. Actually this trend is seen for about 75 percent of the USA based on dynamical models and past trends. Little emphasis is placed on El Nino at the moment because it remains in a neutral state. The precipitation outlooks shows equal chances for above or below normal values over the October-December period across most of the USA except the southeastern and mid-Atlantic states which are expected to see above normal values.

Weekly Weather potpourri

Excerpt from this week's report out of USDA/OCE-World Agricultural Outlook Board......
"Crops and cattle in drought continued to rise. Overall, drought has shifted toward the north and west in recent weeks.
-U.S. corn in drought stands at 85%, up a percentage point from a week ago. The corn harvest is underway, 26% complete nationally by September 16.
-Soybeans in drought also rose a point – to 82%. The soybean harvest has accelerated, and stood at 10% complete nationally as of September 16.
-Hay in drought likewise rose 1 point to 67%, eclipsing the 66% high set on July 17 and 24.
-Cattle in drought reached a new high, rising 1 point to 75%.
-Winter wheat in drought was added last week, as planting is underway (11% complete). Nearly three-quarters (74%) of winter wheat areas are in drought.
-Due to expansion of drought in the nation’s mid-section, contiguous U.S. drought coverage reached a record-high 64.82% on September 11, eclipsing last week’s mark of 64.16%. The former record of 63.86% had been set earlier in the summer on July 24.
-The forecast features little if any rain over the next 5 to 7 days in most of the severe-to-extreme drought areas, particularly the Great Plains."

A new analysis of climate models published this week reveals both their strengths and their weaknesses.....according to the Science Daily web site..."the study is one of the first to systematically address a long standing, fundamental question asked not only by climate scientists and weather forecasters, but the public as well: How good are Earth system models at predicting the surface air temperature trend at different geographical and time scales?" This paper, written by Dr. Xubin Zeng (University of Arizona) and his research colleagues is published in Journal of Geophysical Research-Atmospheres shows that climate models have skill in depicting climate patterns across multiple decades (at least 3 or more), and at continental spatial scales. The models are not so good at year by year, or decadal scales. You can read more here.

The International Cloud Appreciation Society is advocating for the naming of a new cloud type, "undulatus asperatus" (aka "agitated waves") which have been photographed in a number of places, including Cedar Rapids, Iowa. It is distinctive looking wave form cloud which Gavin Pretor_Pinney, President of the Cloud Appreciation Society thinks is deserving of recognition in the world cloud atlas published by the World Meteorological Society. You can read more about it here.

Incidentally, the Cloud Appreciation Society announced recently the availability of its 2013 Cloudspotting Calendar. You can order one online by going to their web site.

The National Snow and Ice Data Center (NSIDC) in Colorado announced this week that satellite monitoring of the Arctic Sea this month showed the lowest level of sea ice measured in the satellite monitoring era (since 1979). The new record minimum is almost 300,000 square miles less than the previous record low amount measured in September of 2007. You can read more here.

MPR listener question

I saw where Paul Huttner mentioned a chance for snow showers earlier this week. I have never seen a September snow here. How often does the Twin Cities see a September snowfall?

Answer: In the modern National Weather Service records for the Twin Cities which date back to 1891, there are 13 reports of September snowfalls of a trace or greater, three of which came in September of 1942. In the older Pioneer Era records for the Twin Cities (1820-1890) there were only 4 reports of a trace of snowfall in September. The most recent measurable amount of snowfall was September 24, 1985 when 0.4 inches was reported at MSP International Airport. So historically you could say that September brings at least a trace of snowfall to the Twin Cities only about 8-9 percent of the time, once every 12 years or so.

Twin Cities Almanac for September 21st

The average MSP high temperature for this date is 70 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 51 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 21st

MSP weather records for this date include: highest daily maximum temperature of 94 degrees F in 1937 lowest daily maximum temperature of 46 degrees F in 1913 and 1995; lowest daily minimum temperature of 32 F in 1974; highest daily minimum temperature of 66 F in 1891 and 1908; and record precipitation of 2.07 inches in 1986; Record snowfall is a trace in 1995.

Average dew point for September 21st is 46 degrees F, with a maximum of 69 degrees F in 1924 and 1970 and a minimum of 22 degrees F in 1974.

All-time state records for September 21st

The state record high temperature for this date is 101 degrees F at Wheaton (Traverse County) in 1937. The state record low temperature for this date is 13 degrees F at Alborn (St Louis County) in 1934. State record precipitation for this date is 3.95 inches at Lamberton (Redwood County) in 1968; and the state record snowfall for this date is 0.5 inches at International Falls (Koochiching County) and Walker (Cass County) in 1974 and at Park Rapids (Hubbard County) in 1995.

Past Weather Features:

Heavy late season thunderstorms brought very heavy rains to some parts of Minnesota on September 21, 1870. Ft Snelling reported 1.70 inches, while Ft Ripley reported 3.06 inches and Litchfield received 3.80 inches, still a record for the date in that community.

September 21-22, 1895 saw heavy thunderstorms cross the southern part of the state dropping 2 to 5 inches of rainfall and flooding many fields around Hutchinson, Worthington, and St Cloud. Harvest was delayed for many days in those areas.

September 21, 1904 brought an abrupt end to the growing season with many observers reporting temperatures in the 20s F. Pokegama Dam fell as low as 15 degrees F. Near Worthington the temperature dropped to 29 degrees F damaging some recently harvested potatoes.

September 21, 1934 brought another hard freeze to the state with many observers reporting temperatures in the 20s F, as far south as St Peter. Pokegama Dam reached a low of 15 degrees F, tying their record for the date.

September 21, 1937 was the hottest on record with over 24 communities reporting daytime highs between 90 and 98 degrees F. For many it was the latest seasonal reading of such high temperatures.

September 21-22, 1986 was notable for the thunderstorms which disrupted harvesting in many southern Minnesota counties. Areas from Austin and Zumbrota, north to Farmington were his with 2-4 inch rainfalls. Zumbrota (11.72 inches) and Red Wing (11.51 inches) ended up with record amounts of September rainfall that year.

September 21, 1995 was cold with temperatures in the 30s and 40s F in northern Minnesota communities. Brief snow showers brought some areas a trace up to 1 inch of snowfall. Baudette reported a record amount of 2.0 inches.

Outlook

Cooler than normal weekend coming up, with a chance for frost/freeze on Saturday night in many areas (that have yet to see one). Warming up on Monday to near normal temperatures with little chance for significant precipitation next week under mostly sunny skies.

Friday, September 14, 2012

Last gasp for summer September 11th?

Last gasp for summer September 11th?

Strong south winds ushered in some very hot air across much of the state on Tuesday, September 11th. Many observers reported afternoon temperatures reaching into the 90s F, and in some locations new record high temperatures were set, including:

99 degrees F at Madison, 97 degrees F at Marshall, Owatonna, and Mankato, 96 degrees F at St Cloud, Lamberton, and Sioux Falls (SD), 95 degrees F at Luverne, and 94 degrees F at Waseca (tied record from 1948). MSP Airport reported 95 degrees F, just 1 degree F shy of the record for September 11th, and the first time a temperature that high has been recorded so late in September since 1939. A cold front caused temperatures to drop by 30-40 degrees F on Wednesday (Sept 12). At Madison in Lac Qui Parle County, the temperature fell from 99 degrees F at 3:30 pm on the 11th to 59 degrees F at 3:30 am on the morning of the 12th. On the St Paul Campus temperatures fell by 36 degrees F in less than 12 hours.

Small dose of rain

September 12th brought some much needed rainfall, albeit generally light, to parts of southern Minnesota. Those getting more than a quarter of an inch included: Preston (.45), Luverne (.45), Austin (.50), Caledonia (.75), La Crescent (.55), Spring Grove (.65), Harmony (.70), and La Crescent (.44). Much more rainfall is needed to recharge soils in most of the state, as the US Drought Monitor update released on September 12th still shows all or portions of 37 Minnesota counties to be in severe or extreme drought. You can read more about this here.

Coldest of the season up north

On Friday morning, September 14th the coldest temperatures of the fall season so far prevailed in northern communities. Both Grand Forks, ND and Tower, MN reported 29 degrees F, while Waskish, International Falls, Hibbing, Cook, Crane Lake, Bigfork, and Babbitt reported lows of just 28 degrees F. Embarrass, MN fell to 26 degrees F, coldest in the state. A warm up is seen for the weekend before another round of cold temperatures intrudes on Monday and Tuesday of next week.

Weekly Weather potpourri

A national drought perspective was provided this week by Brad Rippey of the USDA World Agricultural Outlook Board, highlighting the major features of the USA drought. Excerpts include:
Crops and cattle in drought have begun to rise again. Overall, drought has shifted toward the north and west in recent weeks.

- U.S. corn in drought stands at 84%, up a percentage point from a week ago. The corn harvest is underway, 15% complete nationally by September 9.
- Soybeans in drought also rose a point – to 81%. The soybean harvest is underway in a few areas, 4% complete nationally by September 9.
- Hay in drought rose 3 points to 66%, tying the high set on July 17 and 24.
- Cattle in drought reached a new high, rising 2 points to 74%.
- Winter wheat in drought is added this week, as planting is underway (4% complete). Nearly three-quarters (74%) of the winter wheat area is in drought.
- Due to expansion of drought in the nation’s mid-section, contiguous U.S. drought coverage reached a record-high 64.16% on September 11. The former record of 63.86% had been set on July 24.

The World Meteorological Organization (WMO) in Geneva, Switzerland issued a news release this week which invalidates the former world record high temperature reading of 136.4 degrees F from El Azizia, Libya (southwest of Tripoli) on September 13, 1922. The WMO Commission on Climate Extremes thoroughly investigated the record and found a number of concerns, including problematic instrumentation, observation site that was over a paved surface, and poor matching to surrounding measurements. With this declared invalidation, Furnace Creek in Death Valley now holds the world record high temperature with 134 degrees F, measured on July 10, 1913. On July 11 this past summer Death Valley reported a high of 128 degrees F, with an overnight low of 98 degrees F.

Dr. Nir Krakauer of City College of New York published a recent study to show that the Plant Hardiness Zones in the USA are shifting with climate change. His work suggests that the Plant Hardiness Zones released by the USDA earlier this year are really out of date as climate continues to change and winters become milder. You can read about his analysis here.

September is National Preparedness Month and there are many resources available at the FEMA website to assess your community's ability to deal with emergencies. You can get involved in regional discussions about disaster preparedness, read about building a supply kit for emergencies, join the national preparedness coalition, or get recommendations for developing a business emergency plan.

Super Typhoon Sanba in the Western Pacific Ocean was gathering strength this week and heading towards southern Japan and eventually South Korea. It packed winds of 165 mph with higher gusts and it was producing wave heights over 50 feet. It is expected to bring very heavy rains and high winds to Kadena, in southern Japan by the weekend.

MPR listener question

A number of people have recently asked whether we recorded above normal sunshine during the 2012 summer season in Minnesota.

Answer: The answer to this question is yes. Based on June-August sky conditions reported from MSP Airport, there were 11 percent more clear sky days, 39 percent more partly cloudy days, and close to 80 percent less totally cloudy days. In addition, the measurements of solar radiation (total solar energy) from the University of Minnesota Research and Outreach Center at Waseca show 11 percent more solar radiation than average in June, 6 percent more than average in July, and 7 percent more than average in August. Of course there is a historical correlation between drought and more sunshine, and that was evident this year.

Twin Cities Almanac for September 14th

The average MSP high temperature for this date is 71 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 52 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 14th

MSP weather records for this date include: highest daily maximum temperature of 98 degrees F in 1939 lowest daily maximum temperature of 48 degrees F in 1903; lowest daily minimum temperature of 33 F in 1996; highest daily minimum temperature of 74 F in 1939; and record precipitation of 1.60 inches in 1994.
 
Average dew point for September 14th is 47 degrees F, with a maximum of 73 degrees F in 1994 and a minimum of 25 degrees F in 2011.

All-time state records for September 14th

The state record high temperature for this date is 103 degrees F at Redwood Falls (Redwood County) in 1939. The state record low temperature for this date is 18 degrees F at Cook (St Louis County) in 1964. State record precipitation for this date is 9.22 inches at Bricelyn (Faribault County) in 2004; and the state record snowfall for this date is 0.3 inches at International Falls (Koochiching County) in 1964.

Past Weather Features:

Light frost was reported in the Twin Cities area on September 14, 1873. The official temperature dropped to 35 degrees F. It was the first of 9 nights when the temperature fell into the 30s F during September, one of the coldest in state history.

A trace of snowfall was measured in both Minneapolis and St Paul back on September 15, 1916. It was the start of the worst snow season in the Twin Cities since that of 1880-1881 (estimated 110 inches in St Paul). Twin Cities snowfall for 1916-1917 totaled 84.9 inches. In fact, statewide it turned out to be a very challenging winter, with nearly 82 inches of snowfall at Duluth and 99 inches at Stillwater.

September 14, 1923 brought a killing frost to Minnesota, with a number of observers reporting morning lows in the 20s F. Campbell, New Ulm, and Zumbrota all reported temperatures in the 20s F as the growing season came to an abrupt end.

An autumn Heat Wave had a grip on the state over September 13-15, 1939, as most observers reported temperatures in the 90s F. New Ulm, St Peter, and Tracy reached 100 degrees F. Fortunately a strong cold front ended the hot spell of weather on the 16th, dropping temperatures by 25-20 degrees F.

An F-2 tornado (winds 113-157 mph) touched down about 3:45 pm on September 14, 1941 near Gilman in Benton County. It was on the ground for 8 miles and torn the roof off many homes. it also destroyed barns and out buildings on at least three farms.

On September 14-15, 2004 a stalled frontal boundary over southern Minnesota produced a series of thunderstorms which created widespread flash flooding in Martin, Faribault, Freeborn, Mower, and Dodge Counties. In those areas from 8 to 13 inches of rainfall was received over a 36 hour period. There were many mudslides and road closures in one of the largest flash flood events in state history.

Outlook

Warmer over the weekend with highs from the lower 70s to lower 80s F. Increasing clouds late Sunday and a chance for showers and thunderstorms into Monday, then cooler for Tuesday and Wednesday next week. There will be another chance for rainfall by late next week.
 

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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