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Friday, April 21, 2017

April continues trend of warm and wet

April continues trend of warm and wet:

So far this month most Minnesota climate observers are reporting warmer and wetter than normal conditions. Temperatures are averaging 5 to 7 degrees F warmer than normal. Through April 19th eight daily record maximum temperatures have been tied or set within the climate observation networks, while thirty-nine daily record warm minimum temperature records have been tied or set.

Precipitation this month has been in surplus across much of central and southern Minnesota, but deficit in west-central and northwestern counties. Thunderstorms have brought new daily precipitation records to nine climate stations so far, including 2.45 inches to Winona Dam on April 19th. A number of areas have reported measurable precipitation on over half of the days of the month and a total of over 3 inches. Some other observers in southeastern Minnesota report over 5 inches for the month. The abundant precipitation this month has prohibited farm field work in many areas as soils are too wet for equipment.

Clearly this month is following a trend from the last two years (24 months) during which 22 months have been warmer than normal, and 16 months have been wetter than normal.

Look at early growing season:

One of the more recent forecast models deployed by NOAA is the North American Multi-Model Ensemble (NMME). This approach takes a composite from many different models to assess the probability of monthly and seasonal climate anomalies being above or below average values. For Minnesota, the recent NNME output favors warmer than normal conditions across the state for the May through July period, and less than normal precipitation. The precipitation outlook if it verifies would break the trend of wetter than normal which we have experienced over the past two years.

March for Science:

This year, Earth Day, April 22 (Sat), will also see widespread activity around the nation and state of Minnesota associated with the "March for Science." This is about demonstrating and speaking out for how important science is to understanding the world we live in, managing our natural resources, our societal infrastructure, and our care for each other. I will be part of the March for Science in St Paul at the State Capitol starting at 11am Saturday. Please join in if you care about science. There will be comments from many people advocating for science based knowledge to be used by our policy makers at all levels.

Larson-Allmaras Endowed Lecture:

The Annual Larson-Allmaras Endowed Lecture will take place at 2pm in Rm 335 Borlaug Hall on the University of Minnesota St Paul Campus. This annual public lecture will focus on the Red River and Lake Winnipeg this year. Speakers include Dr. David Lobb and Dr. Donald Flaten from the University of Manitoba, and Aaron Buesing,from the District Office of the Army Corps of Engineers, and project engineer for the Fargo-Moorhead Diversion on the Red River.

Weekly Weather Potpourri:

There is an excellent article this month by NOAA's Caitlyn Kennedy about changing Plant Hardiness Zones and how those who garden should give this consideration when they decide about their spring planting. There is an interactive map to show how these zones have changed over time. For many parts of Minnesota Zone 4 and Zone 5a plants can now be planted in the landscape with minimal risk of winter injury. This NOAA analysis was done with the collaboration of the American Public Garden Association.

Romania, Hungary, Austria, and Ukraine reported winter-like conditions this week with cold temperatures, heavy snows, and strong winds. Travel and business were disrupted in those countries by a strong low pressure system that ushered in some Arctic air which dropped temperatures by 30 degrees or more.

A recent paper "Savor the Cryosphere" published by the Geological Society of America highlights the visible evidence of climate change through a temporal series of photographs of ice sheets and glaciers as they are retreated significantly over recent decades. This strong visual evidence dovetails nicely with the upward trend in temperature records at most of these places.

MPR listener question:

Getting anxious about planting corn here in Blue Earth County. Any idea when we might see a few dry, sunny days to do so? In recent years we have been able to get some of our corn planting finished by late April.


If you have tile drainage, it will definitely be an asset this month in drying out wet soils. The next best opportunity appears to be Friday through early Wednesday, as we will see several sunny days with little chance of precipitation. Unfortunately from Wednesday (April 26) through the first few days of May looks to be a rainy period.

Twin Cities Almanac for April 21st:

The average MSP high temperature for this date is 61 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 40 degrees F (plus or minus 7 degrees F standard deviation).

MSP Local Records for April 21st:

MSP records for this date include: highest daily maximum temperature of 95 degrees F in 1980; lowest daily maximum temperature of 34 degrees F in 1893; lowest daily minimum temperature of 22 degrees F in 1966; highest daily minimum temperature of 59 F in 1885 and 1926; record precipitation of 0.74 inches in 1912. Record snowfall on this date is 6.6 inches in 2002.

Average dew point for April 21st is 34°F; the maximum dew point on this date is 60°F in 1952; and the minimum dew point on this date is 11°F in 1984.

All-time state records for April 21st:

The all-time state high temperature for today's date is 100 degrees F at Ada (Norman County), Montevideo, Georgetown, and Campbell in 1980; the all-time state low for today's date is -14 degrees F at Embarrass (St Louis County) in 2013. The all-time state record precipitation for this date is 2.49 inches at Warroad (Roseau County) in 1974. The all-time state record snowfall for this date is 15.0 inches at Lynd (Lyon County) in 1893.

Past Weather Features:

Perhaps the worst ever storm on this date (April 21) occurred in 1893. A large late season winter storm brought rain, sleet, ice, and snow to the state over three days from the 19th to the 21st. Snowfall totals ranged from 10 to over 30 inches for the 3-day storm, which shut down the railroad for a time. Blizzard conditions prevailed in parts of central Minnesota, where St Cloud reported an all-time record of 36 inches.

The hottest April 21st in state history occurred in 1980, a very dry, sunny month. At least 40 Minnesota climate stations reported a maximum temperature of 90°F that day, while Ada, Montevideo, Georgetown, and Campbell reached 100 degrees F, the earliest known date in Minnesota for such a reading. Even International Falls and surrounding areas reached 90 degrees F.

By far the coldest April 21st in state history was in 2013. Eight northern Minnesota communities reported subzero morning low temperatures, ranging from -1°F to -14°F. As far south as Worthington it was just 17 degrees F, while many daytime high temperatures only climbed up to the freezing mark.


Sunny and warmer than normal temperatures for the weekend over most of the state. More clouds in the north with some chance for rain or snow showers later on Saturday and into Sunday. Mild temperatures will prevail. Somewhat cooler on Monday with a slight chance for showers, drier Tuesday and Wednesday, then chance of rain Thursday through Saturday.



Friday, April 14, 2017

April Snow and a Temperature Rebound

April Snow and a Temperature Rebound:

Thunder and showers later on Sunday gave way to cooler temperatures and snow on Monday across portions of Minnesota. At times Monday night (April 10) into early Tuesday morning, snow showers were heavy for brief periods of time. Total snow accumulation across portions of central and southern Minnesota ranged from 1 to 3 inches in many spots. Observers in North Branch (Chisago County) and New Hope (northern Hennepin County) reported over 5 inches. Following the snow, the coldest temperatures of the month so far were reported, Many northern observers reported morning lows in the teens, while Embarrass and Seagull Lake went down to 12F. However a quick warm-up followed and the heavy, wet snow melted rapidly with temperatures climbing into the 50s and 60s F.

Over the first 9 days of April, the temperature pattern was consistently warmer than normal, with reports of four new record maximum temperatures set, including 81 degrees at Marshall on the 9th, and reports of 16 new daily record warm minimum temperature records. With the generally warmer than normal weather this month, soil temperatures have climbed into the upper 40s F and low 50s F around much of the state. This has motivated farmers to think about planting, and some spotty field activity was observed around the state this week. I suspect next week will bring a significant amount of corn planting.

An Apology for Comments on Temperature Trends:

Last week I made a gross error in judgement in describing the change in monthly values of temperature using percentages. This was stupid! There are at least three scales used for measuring temperature (Celsius, Fahrenheit, and Kelvin) all giving drastically different answers in terms of percentage changes which don't really make any sense. My point in writing about temperature change was simply to illustrate that the changes in value have been larger in the months of December, January, February, and March (3°F to 6°F) than they have in other months. And further that the change in July has been relatively minor (1F). It is important to understand that the measured climate changes in our states are not equal in all months. I am sorry for creating confusion by referencing percentages.

Weekly Weather Potpourri:

Tropical Cyclone Cook struck New Zealand this week with very heavy rains and strong winds. This large storm cut a wide swath of damages due to flooding and wind. Some areas reported wind speeds up to 100 mph and gusts to 125 mph causing broken trees and down power lines. Several inches of rain fell in widespread areas, and flooded roads and highways were closed. Initial assessment was that Cook is the strongest cyclone to hit New Zealand in decades.

NOAA scientists described a new satellite based tool for assessing the onset of drought across the American landscape. It is called the Evaporative Stress Index (ESI) and is derived from GOES satellite measurements. With this imagery areas where drought may be developing can be assessed and compared to the weekly Drought Monitor maps.

The Climate Explorer, a NOAA web-based tool for examining climate maps, graphs, and data tables at the county level has been nominated for the annual Webby Awards in the Best Visual Design Category. It is interesting to compare the climates of different regions with each state.

A new international research study finds that climate change will thaw about 20 percent more permafrost landscape than previously thought. Scientists from the United Kingdom Meteorological Office discussed these findings earlier this week. When permafrost thaws greenhouse gases are released into the atmosphere, and in addition the soil becomes less stable and there is often damage to structures built on it. Approximately 35 million people live on permafrost landscapes.

MPR listener question:

It was difficult driving in the snow storm Monday night this week, very heavy at times. What is the largest amount of snow we have received in the state during the month of April?


Well, I will answer that in two different time frames. On a daily basis, the largest amount ever was 28 inches at Pigeon River (Cook County) back on April 5, 1933. For a monthly total snowfall, several climate stations have reported over 40 inches in April, with Duluth and Two Harbors getting over 50 inches of snow during April of 2013. So a few inches in April is "nuisance snow."

Twin Cities Almanac for April 14th:

The average MSP high temperature for this date is 57 degrees F (plus or minus 11 degrees F standard deviation), while the average low is 37 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for April 14th:

MSP records for this date include: highest daily maximum temperature of 89 degrees F in 2003; lowest daily maximum temperature of 32 degrees F in 1928; lowest daily minimum temperature of 18 degrees F in 1926 and 1928; highest daily minimum temperature of 64 F in 2003; record precipitation of 1.56 inches in 1983. Record snowfall on this date is 13.6 inches from the same storm in 1983.
Average dew point for April 14th is 31F; the maximum dew point on this date is 61F in 1976; and the minimum dew point on this date is 7F in 1928.

All-time state records for April 14th:

The all-time state high temperature for today's date is 94 degrees F at Benson (Swift County) and Milan (Chippewa County) in 2003; the all-time state low for today's date is -5 degrees F at Roseau in 1950. The all-time state record precipitation for this date is 2.95 inches at Northfield (Rice County) in 1886. The all-time state record snowfall for this date is 16.0 inches at Farmington (Dakota County) in 1983 and at Mankato (Blue Earth County) in 1928.

Past Weather Features:

By far the most significant historical weather event on April 14th in Minnesota history was the devastating EF-4 tornado that destroyed Sauk Rapids on the afternoon of April 14, 1886. This tornado, at times 800 yards wide passed over the Mississippi River and sucked it dry for a few minutes. It destroyed a school, a post office, two churches, and a bridge in Sauk Rapids injuring over 200 people and killing 72 others, including several members of an outdoor wedding party.

The coldest April 14 occurred in 1950 when morning lows ranged from single digits to the teens across most of the state. Places in the north like Roseau and Warroad saw subzero temperatures and daytime highs did not reach the freezing mark.

A spring snow storm brought heavy snow to many parts of the state over April 14, 1983. Heavy, wet snow covered portions of southern and central Minnesota, bringing down large tree limbs, as well as power lines. In St Cloud a 90 foot tall tower was toppled by over 50 mph winds. Some roads were closed due to blizzard conditions as some climate stations in southern and central Minnesota reported 12 to 19 inches of snow.

The warmest April 14th was in 2003, when 25 Minnesota communities saw the mercury climb to 90°F or greater. Even Warroad up by Lake of the Woods reached an afternoon high of 80 degrees F.


Warm and wet on Saturday with widespread showers and a chance for thunderstorms. Cooler and breezy for Easter Sunday, with highs in the 50s F, somewhat near normal. Chance of showers again by Tuesday, with temperatures averaging a few degrees F warmer than normal most of next week.

Friday, April 7, 2017

Dissecting climate trends in Minnesota month by month

Dissecting climate trends in Minnesota month by month:

Several people have asked me in recent years if our Minnesota climate is changing more in certain months of the year than others. This is difficult depending on which climate attribute you are looking at. On a statewide basis I have looked at monthly temperatures and monthly precipitation and their measured changes over the past 100 years. Taking each value I have looked at the net change in mean monthly temperature and mean monthly precipitation per decade over the past 100 years and compared this net change to the 100 year average. Here are some examples:

For temperature, the biggest change has occurred in January with the monthly mean value now (most recent decade) that is 3.7°F higher than it was a century ago. This is a 57 percent increase relative to the 100 year mean monthly value for January temperature of 6.5°F (from a statewide calculation). By most statistical criteria this is a significant change in mean monthly temperature. Another example is the change in average February temperature. It is now 5.8°F greater than it was a century ago, and this represents 48 percent of the 100-year mean value for the month of 12.1°F. Some other months with significant changes in mean temperature are:
December: +3.0°F increase
March: +4.2°F increase
November: +2.9°F increase
The month with the least change in mean temperature is July, which shows a plus 1°F or about 1 percent of the 100-year mean monthly value. Overall on a statewide basis the mean annual temperature in Minnesota has increased by 2.4°F over the past 100 years, which is about 6 percent of the 100-year mean annual temperature (40.1°F).

The pattern of temperature increase in the Twin Cities climate record is somewhat similar, but with different magnitude. For example February is the month that has increased the most in the Twin Cities Metro Area with a rise of 5.2°F.

A similar analysis for monthly precipitation shows some significant disparities of change between months on a statewide basis. Here are some of the results: October has seen an increase in total monthly precipitation of 0.52 inches, which represents 27 percent of the 100-year mean value (1.92 inches). April has seen a rise of 0.42 inches, which represents 20 percent of the 100-year mean monthly value, and December precipitation has increased by 0.27 inches, which represents 33 percent of the 100-year mean monthly value (0.81 inches). Overall on a statewide basis mean annual precipitation has increased by 2.82 inches, about 11 percent of the 100-year annual mean (25.98 inches).

For the Twin Cities, there are some different changes in precipitation. August has seen the largest change in mean monthly precipitation increasing by 1.02 inches over what it was a century ago. April monthly precipitation has increased by 0.91 inches, a value that represents nearly 43 percent of the 100-year monthly mean (2.12 inches). And September is the only month in the Twin Cities climate record that is now less than it was 100 years ago. There has been a decrease of 0.59 inches in mean September precipitation, a decline that represents 20 percent of the 100-year monthly mean value (2.90 inches). Overall the Twin Cities mean annual precipitation has increased by 3.51 inches, about 13 percent of the 100-year mean value (27.38 inches).

Clearly the pace of change in these climate attributes shows some differences depending on what month of the year is examined.

Kite Flying Time:

Though peak wind speeds in Minnesota are associated with the tornadoes and severe thunderstorms of summer, "average daily wind speeds" peak in the month of April. Most communities around the state report average wind speeds of 12 to 15 mph during this month. This makes for great kite flying weather, but also has implications for the farmer and the home gardener as exposed soils and vegetation can dry out very rapidly in the absence of adequate rainfall. The atmosphere in April can also be so dry that sometimes when combined with higher wind speeds the National Weather Service will have to issue "Red Flag Warnings" with their daily forecasts. Perhaps we don't need to worry about this as it looks like it is going to be a wetter than normal month.

Weekly Weather Potpourri:

For the first time the National Adaptation Forum is coming to Minnesota. It will be held over May 9-11 at the St Paul River Center. There will be 80 symposia and 30 working group/training sessions focusing on the practice of climate adaptation. Mayor Chris Coleman of St Paul will be a featured speaker on the first day, and a number of Minnesota scientists and citizens, along with state and local units of government will be featured. Might be worth a look for those interested in the practice of climate adaptation.

NOAA scientist recently offered a map viewer to examine the extent of sea level rise and its effect on coastal communities. It provides a tool for examining the impact in the most vulnerable areas. More information can be found at the NOAA Digital Coast web site.

Tropical Cyclone Ernie was churning off the northwest coast of Australia this week, packing wind gusts over 120 mph and producing sea waves of 30 to 35 feet. It was expected to grow stronger over the weekend but remain out to sea.

There is an interesting article in the current AGU EOS issue about the role of nitrous oxide in the atmosphere, especially in high latitudes. More study is needed to determine its potential role in future climate change.

MPR listener question:

This time of year you and your colleagues in the National Weather Service always remind us about severe weather season. When is Severe Weather Awareness Week this year?


Severe Weather Awareness Week in Minnesota will be from April 17 to April 21. There will be daily announcements that week about types of severe weather, communications protocols, and recommendations to protect yourself and your family. In addition there will be "tornado drills" on April 20th at 1:45 pm and 6:45 PM.

Twin Cities Almanac for April 7th:

The average MSP high temperature for this date is 53 degrees F (plus or minus 12 degrees F standard deviation), while the average low is 33 degrees F (plus or minus 8 degrees F standard deviation).

MSP Local Records for April 7th:

MSP weather records for this date include: highest daily maximum temperature of 83 degrees F in 1991; lowest daily maximum temperature of 25 degrees F in 1923 and 1936; lowest daily minimum temperature is 6 degrees F in 1936; highest daily minimum temperature of 54 degrees F in 1991; record precipitation of 1.72 inches in 1919; and a record snowfall of 8.3 inches also in 1923.

Average dew point for April 7th is 27°F; the maximum dew point on this date is 54°F in 2001; and the minimum dew point on this date is 0°F in 1936.

All-time state records for April 7th:

The state record high temperature for this date is 91 degrees F at Canby (Yellow Medicine County) in 1991. The state record low temperature for this date is -16 degrees F at Tower (St Louis County) in 1982. State record precipitation for this date is 3.52 inches at Blue Earth (Faribault County) in 2006; and record snowfall is 24.0 inches at Tower (St Louis County) in 2008.

Past Weather Features:

A rare late winter storm brought heavy snow to parts of Minnesota over April 6-8, 1923. Many central Minnesota communities reported 5 to 12 inches of snow. Though plagued by much colder temperatures, northern residents reported only traces of snow from this storm.

Following a snow storm on April 6, 1936, a polar air mass brought the coldest April 7th in state history. Over 30 Minnesota communities reported subzero morning temperatures and daytime highs barely climbed into the 20s and 30s F. It was short-live as temperatures returned to normal two days later.

April 7, 1991 was the warmest in state history, as over 60 communities reported daytime highs of 80°F or greater. Many climate stations never fell below 60 degrees F even at night, and Winona reported a balmy low temperature of 70 degrees F.


Much warmer on Saturday under mostly sunny skies. Temperatures will reach the 60s in the north, and the 70s F and 80s F in the south. More clouds on Sunday and a chance for rain and even thunderstorms by later in the day. Continued chance for rain, and even some snow in the north on Monday. Near normal temperatures again by Tuesday, then another warming trend with a chance for showers next Thursday.


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