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Extension > Mark Seeley's WeatherTalk > September 2017

Friday, September 22, 2017

A Flush of September Warmth and High Dew Points

A Flush of September Warmth and High Dew Points:


The trend toward above normal temperatures this month, which began on the 10th, continues in a big way through this weekend. Most observers now report September mean temperatures that are 2 to 4 degrees F warmer than normal, but have yet to see real extremes. This will change for Friday through Sunday as several areas of the state will see daytime highs soar into the 80s and 90s F, with nighttime lows in the 60s and 70s F. As a result, it is likely that some new daily temperature records will be set in terms of both warm daytime highs and warm nighttime lows. So far the highest temperature measured this month was 93 degrees F on the 14th at Browns Valley (Traverse County). This is likely to be surpassed.

According to the Minnesota State Climatology Office it is especially unusual to see a series of nighttime low temperatures in the 70s F so late in the month of September. In fact for the Twin Cities climate record consecutive nightly lows in the 70F during the month of September is rare indeed, having happened only in 1897, 1927, 1939, 1948, and 1955. Should nighttime lows remain in the 70s F both Friday and Saturday (Sept 22-23) it will be the latest ever such occurrence.

In addition, a significant feature of this September warm spell is the high dew points. A new daily high dew point record was set in the Twin Cities on September 21 (Thursday) this week with a reading of 70 degrees F at MSP Airport. As a result a Heat Advisory was released for many portions of Minnesota on Friday, September 22nd. Many new daily high dew point records are likely to be set on Friday and Saturday too, as dew points spike into the 70s F. Already a new record high dew point was set at 8am on Friday morning at MSP with a reading of 71 degrees F, while the record for Saturday, September 23 is 73 degrees F from 1945 and this may be threatened this weekend.

Weekly Weather Potpourri:


This week NOAA's Tom Di Liberto provides an analysis of the impacts of Hurricane Harvey on the Houston, TX area. It is an interesting article about the meteorology of the storm, but also the societal impacts.


The United Kingdom Met Office is celebrating 100 years of numerical weather forecasting this week. They trace the beginnings of their numerical weather forecasting back to the WWI era when Lewis Fry Richardson began to use spatial grids of meteorological measurements to calculate changes in forecast parameters such as temperature and moisture. What took him weeks to do back then, can be done by computers in less than one second today.


Earlier this week NASA reported that the extent of end-of-summer Arctic Sea Ice was the 8th lowest in the satellite record period going back to 1978. Arctic sea ice reached its annual minimum areal extent on September 13th, and is now starting to build again with the approach of the Northern Hemisphere winter season.

MPR listener question:


With this expected Heat Spell, what is the warmest overnight low temperature during September ever observed in Minnesota?

Answer:


In the Twin Cities climate record the warmest overnight low in the month of September was 77 degrees F on September 5, 1912. On a statewide basis the warmest September night was September 11, 1931 when the overnight low was 85 degrees F at Bird Island (Renville County). BTW that day was probably the warmest September day in Minnesota history with over 100 communities reporting afternoon highs in the 90s F and many places in western Minnesota well over 100 degrees F.

Twin Cities Almanac for September 22nd:


The average MSP high temperature for this date is 69 degrees F (plus or minus 10 degrees F standard deviation), while the average low is 49 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for September 22nd:

MSP records for this date include: highest daily maximum temperature of 95 degrees F in 1936; lowest daily maximum temperature of 49 degrees F in 1913 and 1983; lowest daily minimum temperature of 26 degrees F in 1974, 2007, and 2011; highest daily minimum temperature of 71 degrees F in 1937; record precipitation of 2.80 inches in 1895. No snow has fallen on this date in the Twin Cities.

Average dew point for September 22nd is 45°F; the maximum dew point on this date is 70°F in 1903; and the minimum dew point on this date is 20°F in 1974.

All-time state records for September 22nd:


The all-time state high temperature for today's date is 101 degrees F at Ada (Norman County) in 1936; the all-time state low for today's date is 10 degrees F at Thorhult (Beltrami County) in 1974. The all-time state record precipitation for this date is 4.84 inches at Cambridge (Isanti County) in 1968. Record snowfall is 2.0 inches at Baudette (Lake of the Woods County) in 1995.


Past Weather Features:


Strong thunderstorms brought three to six inches of rain to southern and central Minnesota over September 21-22, 1895. There were also many reports of hail. Fortunately crops had matured early that year and much of the harvest had already been completed. Widespread frost followed the thunderstorms.

By far the warmest September 22 in state history was in 1931 when over 40 Minnesota communities reported daytime highs in the 90s F. At seven locations the temperature reached 100 degrees F or greater.

The coldest September 22nd in state history was in 1974 when frost occurred in every corner of the state. Over two dozen climate stations in northern and western Minnesota reported morning lows in the teens F, and at Thorhult (Beltrami County) it was a nippy 10 degrees F. The high at Brainerd only rose to 41 degrees F.

An early autumn snow storm brought measurable amounts to western and northern parts of the state over September 22, 1995. Traces of snow were reported as far south as Luverne (Rock County), while in the north an inch or two was measured with temperatures in the upper 20s and low 30s F.

Strong and persistent thunderstorms brought record-setting rains to portions of southern Minnesota over September 22-23, 2010. Most southern Minnesota counties received over 6 inches of rain and parts of Faribault County received over 11 inches. Numerous roads were closed to flash flooding, and a week later the Mississippi River rose above flood stage.

Outlook:


Warm and humid over the weekend with chances for showers and thunderstorms. Continued chance for showers through early next week, but temperatures will decline near seasonal averages. Drier toward the end of next week.

Friday, September 15, 2017

Warm-up boosts crop maturation

Warm-up boosts crop maturation:


With the cold start to the month of September many farmers were concerned about corn and soybeans not reaching maturity before the first frost. The dramatic warm-up in temperatures this week (5 consecutive days with temperatures running from 6-12 degrees F warmer than normal) this concern has been mostly alleviated. Corn has matured rapidly this week, as have soybeans. In fact the degree of warm temperatures has been so persistent statewide that it has offset the cold start to the month, and now most climate stations are reporting mean September temperatures that are warmer than normal at mid-month. In addition warmer than normal temperatures are expected to prevail across Minnesota until near the end of the month. This may not only help with crop maturation, but accelerated dry-down before harvest season begins.

Rainfall has certainly been lacking this month, but I don't think this has had much effect on crop yields. The second half of September is supposed to be wetter than the first half.

Drought still present in parts of northwestern Minnesota:


Dryness has persisted most of the 2017 growing season in portions of northwestern Minnesota (canola, wheat, and sugar beet country). More recently portions of thirteen counties in the northwest have been designated to be in moderate drought (by the U.S. Drought Monitor), while portions of Marshall, Beltrami, and Lake of the Woods Counties have been designated to be in severe drought. Since May 1st or the start of the growing season many climate stations in this part of the state have measured 30 to 40 percent less than normal rainfall. A few areas have received less than half of normal rainfall for the growing season. In these areas they are hoping for a wet autumn season to replenish depleted soil moisture supplies.


Weekly Weather Potpourri:


The Minnesota State Climatology Office has recently developed climographs (monthly graphical depictions of temperature and precipitation normals) for all climate stations in the state. These are very useful for looking a different climates within the state, and also if you are traveling around the state. You can find these graphics and data under the header Climograph Portal.


Storm Aileen (not a tropical storm but a mid-latitude cyclone) brought high winds and rains to portions of the United Kingdom this week. This intense low pressure system produced winds of 55-65 mph across portions of Cheshire, Lancashire, Derbyshire, Yorkshire, and Nottingshire earlier this week. Some wind gusts close to 70 mph were reported.


Elsewhere in the East China Sea Typhoon Talim was churning with winds over 110 mph, producing wave heights of 30-35 feet. After bringing rains to parts of South Korea, it is expected to turn northeast and head towards Japan over the weekend. A second typhoon, Dokshuri, is expected to bring heavy rain to Vietnam this weekend.


A recent study from Indiana University documents that people affected by extreme weather or climate events do initially support policies to improve climate adaptation and resilience, but that response is relatively short-lived. Their longer term attitudes towards climate change are more heavily governed by their political beliefs or political party affiliations.


NOAA features an article this week on expanding malaria zones in Ethiopia as a result of warming temperatures, especially at higher elevations. This is mostly due to rising minimum temperatures rather than maximum temperatures.


AGU-EOS released an interesting paper this week about the warmer ocean temperatures and rising sea level measurements. These measurements clearly relate to global climate change, and the upward trends are substantial. Dr. John Abraham from University of St Thomas in St Paul contributed to this study.

MPR listener question:


The 91 degrees F at MSP on September 14 this week was the first reading of 90°F or higher here since July 22. How often does September bring 90 degrees F days following an August that does not bring any?

Answer:


This is rare and has happened only 8 times since 1871, the most recent year was 2011, when there were no 90°F days in August, but 3 such days in September.

MPR listener question:


Last week I heard you talk to Cathy about the September snow storms of 1912 and 1942. But, my grandmother wrote about having a snow storm interrupt the wheat harvest in Dakota County in September of 1916. Can you shed any light on that?

Answer:


Indeed, the crop harvest was later than normal in 1916 so wheat harvesting was underway in September when an early winter storm crossed the state on the 15th of September. Strong winds (>30 mph) and low temperatures pushed the wind chill into the 20s F statewide and a mixture of rain and snow fell in 18 counties, with the snow ranging from a trace to 0.3 inches. This disrupted the harvesting of all crops including wheat, corn, and potatoes. Widespread frost was reported as low temperatures ranged from 23 degrees F to 32 degrees F across half of the state. In many northern Minnesota communities the daytime high temperatures never rose above the low 40s F.

Twin Cities Almanac for September 15th:


The average MSP high temperature for this date is 72 degrees F (plus or minus 9 degrees F standard deviation), while the average low is 53 degrees F (plus or minus 7 degrees F standard deviation).

MSP Local Records for September 8th:

MSP records for this date include: highest daily maximum temperature of 98 degrees F in 1939; lowest daily maximum temperature of 46 degrees F in 1916; lowest daily minimum temperature of 36 degrees F in 1964, 2007, and 2011; highest daily minimum temperature of 72 degrees F in 1897; record precipitation of 1.97 inches in 1997. A trace of snow fell on this date in 1916.

Average dew point for September 8th is 48°F; the maximum dew point on this date is 72°F in 1994; and the minimum dew point on this date is 19°F in 2011.

All-time state records for September 8th:

The all-time state high temperature for today's date is 100 degrees F at St Peter (Nicollet County) in 1939 and at Tracy (Lyon County) in 1955; the all-time state low for today's date is 17 degrees F at Bigfork (Itasca County) in 1964. The all-time state record precipitation for this date is 4.98 inches at Winona Dam (Winona County) in 2004. Record snowfall is 0.2 inches at Warroad (Roseau County) in 1916.

Past Weather Features:


Snow blanketed much of the state on September 15, 1916. This was one of the earliest snows ever across so much of the state landscape. Snow flurries were even observed in the Twin Cities from 10:30 am to 12:30 am, with wind chill conditions that felt like 28 degrees F.

The hottest September 15th in state history was in 1939 when over 50 climate stations reported afternoon high temperatures in the 90s F, records that still stand. St Peter, Springfield, and New Ulm hit the century mark on the thermometer. In many areas the overnight low temperature never dropped below 75 degrees F.

The coldest September 15th in state history was in 1964, when approximately 90 climate stations reported low temperatures of 32°F or colder. More than 60 communities reported morning lows in the 20s F, bringing an abrupt end to the growing season.

September 14-15 brought thunderstorms and heavy rains to parts of southern Minnesota. Many communities reported 8 to 13 inches of rain, and flash floods were declared in 13 southern Minnesota counties. There were many road and highway closures. More on this historic storm can be found at the Minnesota State Climatology Office.

Outlook:


Generally cloudy over the weekend with a chance for showers and thunderstorms on Saturday. Highs will dip below normal on Sunday. Temperatures will warm up above normal beginning on Tuesday of next week, but the daily chance for shower activity will increase as well.



Friday, September 8, 2017

September starts cool and dry

September starts cool and dry:


The month of September has begun cooler and drier than normal across the state. This helped to boost attendance over the final days of the State Fair. Temperatures for the month so far are running from 2 to 6 degrees F cooler than normal, and over 20 northern Minnesota climate stations have already reported morning lows in the 30s F. The coldest spots so far are Fosston (Polk County) with a reading of just 30 degrees F on the 6th and Crane Lake (St Louis County) with a reading of 30 degrees F on September 8th.

On Labor Day, September 4th a strong cold front crossed Minnesota during the afternoon bringing some showers and rapid temperature change. In St Cloud the temperature dropped over 21 degrees F in less than an hour during mid-afternoon, while in the Twin Cities the temperature dropped 10 degrees F in just 10 minutes during the late afternoon. Winds gusted to between 40 and 50 mph with the cold front passage. Many people at the State Fair sought shelter from the rain as well as warmer clothes.

The Galveston Hurricane of September 8, 1900:


On Saturday, September 8, 1900 between 6,000 and 8,000 people perished in Texas as a result of the landfall of the famous Galveston Hurricane. This storm is the center piece in the famous and popular book "Isaac's Storm" which documents the efforts of Dr. Isaac Cline, Director of the Galveston Weather Office in his attempts to warm residents of Galveston about the risks of this storm.

Three days following the landfall of the Galveston Hurricane, its remnant low pressure center had migrated north into portions of Missouri and Iowa, and brought thunderstorms and heavy rains to many parts of southern Minnesota. Many climate stations reported 2 to 5 inches of rain over September 11-12, and parts of Blue Earth County reported nearly 6 inches, a record amount that still stands today. Fall harvest activity was very delayed that month as a result of wet soils.

More on hurricanes and Minnesota weather can be found at the Minnesota State Climatology Office web site.

Weekly Weather Potpourri:


The NOAA National Hurricane Center is obviously having a very busy week monitoring the movements and intensity of three hurricanes: Katia in the southwestern part of the Gulf of Mexico, off the coast of eastern Mexico; Jose in the Central Atlantic Ocean just east of the Lesser Antilles; and Irma now passing between Cuba and the Bahamas. Earlier in the week NOAA announced that Irma was one of the strongest and largest hurricanes to ever form in the Atlantic Ocean. It remains a very serious threat to Florida and the Carolinas as we head into the weekend.


A new study released by the United Kingdom MetOffice in cooperation with the Woodland Trust reveals that earlier spring budburst for nine of eleven tree species is clearly related to a signal of climate change, warmer temperatures in March. Larch and Alder are two of the tree species most affected by this.


A recent study from Scientific Reports documents that ice-ocean albedo (reflectivity) feedbacks play a critical role in the variation and long term loss of Arctic Sea ice. This is a significant factor year to year in the ongoing seasonal loss of Arctic ice cover, which appears to be declining rapidly in the summer season in each passing year.

Earth and Space Science News editor Mohi Kumar was in Houston, TX during the passage of Hurricane Harvey last week and wrote a day by day account of the storm. It makes for a very interesting read and is written as an accounting by a survivor.

MPR listener question:


What has been the biggest snow storm in Minnesota during the month of September?

Answer:


There have been two large ones which caused a great deal of disruption. Both occurred a long time ago. Over September 24-25, 1912 an early winter storm delivered a mixture of sleet and snow to northern Minnesota. Observers there reported 2 to 6 inches of snow, while parts of Polk County reported up to 7 inches of snow. Over September 25-26, 1942 a storm brought a mixture of rain, sleet, and snow to many parts of the state. In many areas the total snowfall ranged from 4 to 8 inches. Roads were even plowed in Renville County following this storm.

Believe it or not both of these late September snow storms were followed by 70°F and 80°F days in early October!

MSP Local Records for September 8th:

MSP records for this date include: highest daily maximum temperature of 99 degrees F in 1931; lowest daily maximum temperature of 54 degrees F in 1929; lowest daily minimum temperature of 36 degrees F in 1883; highest daily minimum temperature of 74 degrees F in 1931; record precipitation of 1.52 inches in 1885. No snowfall has occurred on this date.

Average dew point for September 8th is 55°F; the maximum dew point on this date is 73°F in 1947; and the minimum dew point on this date is 25°F in 1995.

All-time state records for September 8th:

The all-time state high temperature for today's date is 105 degrees F at New Ulm (Brown County) in 1931; the all-time state low for today's date is 20 degrees F at Red Lake (Beltrami County) in 2000. The all-time state record precipitation for this date is 5.54 inches at Young America (Carver County) in 1991. No snow has fallen on this date.

Past Weather Features:


The warmest September 8th for Minnesota was in 1931 when over 30 communities reported afternoon temperatures of 100 degrees F or higher. In western Minnesota the overnight temperature never dipped below 76 degrees F at Milan, Canby, and Montevideo. Some people slept on their porch or on the lawn outside.

The coldest September 8th was in 1956 when 15 Minnesota climate stations reported low temperature in the 20s F, bringing an early end to the growing season.

Thunderstorms brought heavy rains to many parts of the state over September 8-9, 1991. Many climate stations reported rainfall totals of 3 to 7 inches, with many flooded roads and highways. New London in Kandiyohi County reported over 8 inches of rain.

Outlook:



Partly cloudy with a warming trend over the weekend, and generally dry weather. Continued warmer than normal temperatures through much of next week with little chance for precipitation.
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