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

First Teen, First Freezing High

Our first low temperature in the teens this season arrived Wednesday when the low reached 17 degrees at the airport.  Our average first teen of autumn is on October 28, so we achieved that milestone close to that average date.  Our average first high temperature at or below freezing is November 9 and we may hit that next week.

Last year our first freezing high occurred on Veteran’s Day, we also recorded one inch of snow that day as well.  In the autumn of 2009 we did not record such a day until December 2.  That was also the latest such occurrence on record. Of note,  the weather turned cold quickly after date and the winter of 2009-2010 ended up finishing with a below average temperature.  On the other extreme, the earliest freezing high in autumn occurred on October 12, 1909.  

If you are curious, that winter also finished with a below average temperature, although, neither winter finished exceptionally cold by our standards.

Correlation

One of the most common questions that come into the weather center deals with correlation.  We are often asked if because this season is – insert hot, cold, dry or wet – does that mean the next season will be – insert hot, cold, dry or wet—and usually the reference is that the next season will be the opposite of what is currently occurring. 

In other words, is there a correlation between what is occurring now and what we can expect in the future?  Our cold spring have many people inquiring if a hot summer is coming as that would then “balance” the weather.  There can be some correlation between seasons, especially when dealing with El Nino or La Nina events, yet even in those instances the relationship is no where near 100% accurate. Therefore, as a general rule a pattern from one season, does not correlate very well with future seasons. 

Meaning, this summer will not necessarily continue to be cold, or end up extremely warm based on what has been occurring these past few months.

El Nino Fixation

The Climate Prediction Center (CPC) released an updated winter forecast last Thursday.  Most of the year they were forecasting a higher than normal probability of a warmer than average winter, but with their latest forecast, they are now predicting a higher than normal probability of a colder than average winter.

Why the change?  I can not say for sure, but it is probably because the El Nino the CPC thought was going to form, in turn, has not yet formed and there are significant doubts one will form in the upcoming months.  An El Nino, the warming of the equatorial waters in the Pacific Ocean, often brings warmer than average winter temperatures to this area, although, the last El Nino in 2009-2010 did not.

Seasonal weather patterns tend to be dominated by a number of factors, not just one and most of those influences are very difficult or impossible to forecast more than a couple of weeks in advance.

Here is the latest forecast from the CPC.

The Last Hurrah?

In the spring, we are often looking forward to recording our first 60, 70 or 80 degree day of the year. In the autumn on the other hand, it is difficult to know when we have experienced the last such day of the year.

This past Saturday, the official high temperature was 88 degrees and based on a few conversations, many of you probably felt that was the last hurrah of the season.  The average last 80 degree day is September 29, yet, historically an 80 degree high temperature has been recorded approximately every other year during the month of October.  Plus, the last day with a record high in the 80s is on October 25.

Although we have cool off in recent days, considering how dry the top soil continues to be, plus the overall warmth we have experienced much of the year, another day or two in the 80s will likely not surprise any of us.

Thoughts of Winter

With most North Dakota schools starting this week and Labor Day weekend just a week away, many of you are perhaps thinking about autumn and winter more than the last remnants of summer that we have been experiencing lately.  This has been evident in numerous short conversations I have had in recent days as nearly every place I go, the same question comes up.  “What will our winter be like?”

With an El Nino developing in the Pacific Ocean you will likely hear that the upcoming winter will be another mild one in this area.  Yet, the winter of 2009-2010 was an El Nino winter that ended up very cold and snowy because one single parameter does not guarantee certain weather conditions as many forecasters learned that year.

Therefore, it is too early for a prediction, but one thing I can almost guarantee is this area will probably not experience another record breaking warm winter, meaning, that even if temperatures are near normal this cold season, it is going to feel brutal in comparison to last year.

Forecasting the War

At a recent speaking engagement I had the opportunity to have a brief but fascinating conversation with a World War II veteran that was a meteorologist in the Pacific Theatre during the war.  Even with modern technology, forecasting in thePacific Oceanis difficult because of the lack of weather information due to the shear size involved and the few reporting stations.

Satellite data in combination with computer modeling makes for respectable forecasting in the modern era, but of course in the 1940s neither was available.  But the combination of some pilot reports, station reports from ships and islands and good old fashioned experience made for a useful 24 hour forecast.

I often tell students that by simply paying attention to the weather, especially the sky, you can make a respectable forecast for the next day.  The clouds tell a story, their structure, type and movement give hints to the future; you just need to look up.  Sometimes we forgot that old techniques can be more valuable than looking at a computer screen.

Cool Summer?

The phenomenally warm temperatures that we have been and will continue to record this month has many wondering if this has any implications for the upcoming summer. With every year being unique you can never make a definitive forecast.  What happens in the upcoming months will be unlike any other year, yet, it will probably at least resemble or as I like to refer to it, rhyme with other years.

Looking back to the 20 warmest Marches on record, 16 of them, or 80%, in turn were followed by a summer that finished with a below average temperature.  Granted, several of those years were close enough to the average to be considered “near normal”, but nevertheless finished on the low side of the average.  Plus, for those of you who like hot summers, only 1 of those 20 years did the summer finish with a well above average temperature.  Precipitation wise, only 2 of those twenty years finished with excessive rainfall contrary to many recent summers.

This should not be considered a forecast, but just an observation.

Spring Outlook

Once again I was asked by the State Climatologist in North Dakota to write a summary to what I expect for the upcoming season.  What I wrote can be found below.  It can also be found in the State Climate Bulletin to be published soon.

 

Spring and autumns are always the most difficult to forecast because of large swings that can and do occur on both daily and weekly time scales.  Plus, with so much cold elsewhere on the planet, this spring in particular has the potential for giant swings from warm to cold.  These temperature swings can also lead to prolong periods of dry weather intermixed with brief periods of significant precipitation.

Using that as a backdrop, after a mild March that may end up as one of the warmest on record for the region, April looks to be transitioning to colder weather, followed by a near average May.  That would mean, overall, an above average temperature for the season, but we always need to remember, that does not mean consistently above average and a poorly timed cold front can easily hamper the planting season.

Although historically when a La Nina is present is the Pacific, this area has a higher than normal likelihood of recording above average precipitation in the spring, the current La Nina is fading quickly and therefore, the odds favor this season to finish nearer to the long-term average for rain and late season snowfall.  If that forecast holds, it would be a welcome change from the excessive spring moisture many areas have recorded in recent years.

The latest spring outlook from the Climate Prediction Center (CPC) for the next three months can be seen below.The CPC is forecasting a slightly higher than normal probability of above average temperatures and equal changes of above, below or normal precipitation. You can find the current and future outlooks, when new ones become available, athttp://www.cpc.ncep.noaa.gov/products/predictions/90day.

 

Also, the North Dakota State Climate Office has links to the National Weather Service’s local 3-month temperature outlooks for the upcoming year. Those forecasts can be found at:http://www.ndsu.edu/ndsco/outlook/L3MTO.html.