What Is Average?

Halfway through April and it is looking like another colder than average month.  December, January, February, and March have all been significantly colder than average.  April will likely make five months in a row.  Last October and November were also colder than average but only by an insignificant fraction of a degree. September was warmer than average but the summer months last year were only slightly warmer than average.  Average is only the average of the past.  There is no rule that weather has to conform to averages either by remaining near average or by swinging equally one way and then the other.  In this sense, our weather is non-linear, which means it does not converge to an average over time.  We present weather averages only as a way to roughly compare.  For most weather records, what we call, “average” is only the average of the past three full decades.  So what constitutes average weather actually changes over time as our climate goes through changes.      Meteorologist John Wheeler

Ancient Weather Record?

Two scholars at the University of Chicago’s Oriental Institute have translated an ancient Egyptian inscription on a six-foot stone block which seems to be a 3.500 year old weather report. The writing on the block refers to rain, darkness and “the sky being in storm without cessation, louder than the cries of the masses.”  This is now believed to be the oldest weather report ever found. It is possible that this terrible weather may be a result of the Minoan eruption of Thela in the Mediterranean Sea, on the island now known as Santorini.  The Thela eruption is thought to be one of the strongest and most devastating volcanic eruptions of the past several thousand years.  Climate scientists have found evidence of sudden and severe climate change throughout the Northern Hemisphere, including tree ring data in Greenland, bristlecone pines in California, and reports of crop failures in China.  Such massive volcanic eruptions can change climate by ejecting huge amounts of sulphur dioxide into the upper atmosphere where it blocks sunlight for years. Meteorologist John Wheeler

AMO / NAO

March was the sixth month in a row with below average temperatures across the Lower 40 states, according to satellite data.  The satellite-based report resolves global temperatures based on infrared measurements of the atmosphere from the surface up to an altitude of about five miles above sea level.  March was the seventh consecutive cooler-than-average month in Fargo Moorhead, although October and November were only marginally below average.  Interestingly, this is in contrast to most of the Northern Hemisphere, which has been generally warmer than average during this winter and spring,  As explained in this space yesterday, the warmer locations are mostly over the oceans, particularly the Atlantic Ocean, which is undergoing a period of warming known as the Atlantic Multidecadal Oscillation (AMO), a weather pattern which at times can allow for sharp intrusions of Arctic air into central and eastern North America and Europe. Meteorologist John Wheeler

Cold Winter, Mild Winter

A new study recently published in “Environmental Research Letters” shows that the extremely cold winter just experienced across the central and eastern U.S. is likely due to a natural variation is Atlantic sea surface temperature known as the Atlantic Multidecadal Oscillation (AMO). The positive phase of the AMO (a phase of warmer Atlantic temperature) when combined with the negative phase of another circulation pattern, the North Atlantic Oscillation (NAO), a stronger than usual semi-permanent low pressure system near Iceland, results in a much greater frequency of arctic air intrusions into the central and Europe. The AMO changes over decades whereas the NAO changes over periods of weeks or months. The study found that the present positive phase of the AMO when combined with the positive phase of the NAO is likelier than average to yield a mild winter, which could explain our recent run of winters being either extremely cold or extremely mild. This suggests we should expect the winter variability to continue for another decade or two.         Meteorologist John Wheeler

Winter 2013-2014 Statistics

The National Climatic Data Center (NCDC) released their analysis of the winter of 2013-2014 last week.  NCDC ranked the period from December 1 through February 28 as the 25th coldest on record for North Dakota.  You may recall locally it was the 16th coldest on record, but western North Dakota was not as cold making the average for the entire state lower in the cold rankings.

Minnesota on the other hand recorded a more evenly spread cold winter throughout that state.  Taken as a whole, NCDC ranked this past winter as the 6th coldest on record in Minnesota.   The past 119 winters are used in these rankings.  Nationally, NCDC ranked the past winter as the 34th coldest on record.

Using other datasets and analysis puts that ranking closer to the Top 10, but no matter what the ranking; most Americans east of the Rocky Mountains experienced a winter that will not soon be forgotten.

First 50 of 2014

The average date of the first 50 degree high in Fargo Moorhead is March 18.  The high temperature this past Thursday was 58 degrees which was our first 50 (and nearly our first 60 degree) reading of the season.

One of the keys to reaching 50 degrees is snow cover.  Although within the city limits of Fargo Moorhead many areas, particularly the older parts of town there was still plenty of snow on the ground that day, outside of the metro, especially to our west there has been very little snow on the ground for the past few weeks. A west wind off that bare ground helped the temperature reach 58 degrees that afternoon.  If you are curious, the average first 60 degree high is on April 3 and the first 70 is on April 18.

Although the pattern still looks to be producing more cold days than warm ones in the short term, the lack of snow will at least keep temperatures warmer than what it would be with a whiter landscape.

The End of Negatives?

Our last below zero reading was a -1 degree temperature that occurred around 2:30 AM on March 5.  The temperature was well above zero much of that night, but the sky cleared just after midnight, the temperature briefly dropped below zero, then the clouds moved back in and the temperature rose to nearly 10 degrees before most people headed to work or school.  In other words, that below zero reading was hardly even noticed.

Yet, that -1 degree reading did push the seasonal total for days with a low below zero to an even 70 days.  Those 70 days would rank the cold season of 2013-2014 as tied for the 14th highest such total on record.  Although, another negative morning is certainly possible, historically after this point they tend to only occur with a deep snow cover, which we currently lack.

Therefore, with any luck, our next negative morning in Fargo Moorhead will be near November 28, which is the average date of our first below zero reading of our next cold season.

Leap Day Troubles

Leap day.  It is what we call February 29, the day added onto February every fourth year to keep the seasons from slowly drifting through time as the earth takes slightly longer than 365 days to revolve around the Sun.  Leap day on occasion does impact climate statistics and this past winter was possibly one of those times.

Our recently completed winter was the 16th coldest on record, but the National Weather Service recently released a statement that this past winter was the 17th coldest on record.  The difference?  February 29, 1904.  Including that day makes the winter of 1903-1904 average temperature 4.4 degrees.  Without that day, the average temperature is 4.2 degrees.  The winter of 2013-2014 that we just completed had an average of 4.3 degrees meaning that depending on if you include that leap day this winter’s ranking changes by one position.   Is one statistic more accurate than the other?

Not necessarily, but leap day seems to get little respect, so I always include in all my analysis and most other researchers do as well.

Cold, Not Snowy

This past winter season was definitely cold, but it certainly was not snowy.  From December 1 through February 28, the official snow total from our cooperative observer in north Moorhead totaled 27.3 inches.  That is 2.1 inches below the average of 29.4 inches for that time period.  It was the second year in a row with snowfall being very close to the average during the three principal months of winter as last year 28.7 inches was recorded.

More important than the amount of snow is the water content in that snow.  The 27.3 inches of snow that fell in the past three months contained 2.09 inches of liquid, right at the average of 2.14 inches.  Meaning, this past winter was about as average as average gets for winter precipitation.  The driest of the three winter months was February as only 1.5 inches was measured last month, the 8th lowest total on record for that month.

That snow contained only 0.11 inches of liquid making February 2014 the 7th driest since records began in 1881.

The Winter of 2013-2014

The average temperature this past winter (December through February) was 4.3 degrees.  That ranks as the 16th coldest winter of the 133 winters on record in Fargo Moorhead (records began on January 1, 1881, therefore the first winter has incomplete data, meaning the first winter of record was the winter of 1881-1882).

The last colder winter in Fargo Moorhead was back in 1981-1982 when the average temperature was 3.3 degrees.  Other fairly recent colder winters were in the late 1970s.  The winter of 1978-1979 the average temperature was 0.6 degrees and the winter of 1977-1978 the average was 2.8 degrees.  Those were the two coldest back to back winters since the 1880s.  Even with such a cold winter being recorded, no record lows were set.  Of interest, the coldest temperature of winter was just -25 degrees on January 2 which is 3 degrees above the average coldest temperature recorded in a year locally.

There have been colder winters, but if you are under 30, it was the coldest winter in your lifetime.