El Nino

Friday, July 31, 2015

El Nino continues to make weather news.  This change in atmospheric and sea-surface conditions in tropical regions of the Pacific happens every few years or so, but the one building now has the look of being a strong one.  El Nino’s impacts in the middle latitudes are more pronounced during the colder months.

What will the impacts be here?  It depends on other factors, of course.  This is weather which is highly dynamic.  But a strong El Nino can be statistically correlated to a stormier fall season, a much warmer than average winter with below average snowfall, and a colder but drier than average spring.

But it is important to understand that other factors can overwhelm the El Nino signal.  Of particular interest this winter is a large region of unusually warm water in the northeastern part of the Pacific Ocean.  What role this will play is interesting but unknown.

Meteorologist John Wheeler

El Nino 2015-16

A very strong El Nino appears to be developing in the Pacific Ocean. El Nino is a reversal of weather conditions across the tropical Pacific.  Areas near South America get warmer and wetter while areas near Australia become very dry.  This affects the weather around the world by deflecting the Jet Stream.

But the effects around the world (including around here) are hard to predict because other large-scale patterns also influence the storm track.  The biggest concern for our area would be the potential development of a blocking pattern which could bring either persistently wet weather or drought, depending on the shape of the Jet.

At present, a large region of anomalously warm water off the coast of Oregon, Washington, and British Columbia, adds to the uncertainty.  If the strong El Nino continues to develop in conjunction with this warm blob, it could mean a very interesting winter for some parts of the world.

Meteorologist John Wheeler

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.

No Weather Guarantees

Certain terms gradually build into the common vernacular.  Each year the new words that are added to the Oxford Dictionary usually make big headlines on local and national news.  In weather, although many terms have been around for decades within the weather community, in recent years, certain terms have become common place in society.

The term Doppler would be a great example of this.  Another term that garners wide use is El Nino (the warming of equatorial waters in the Pacific Ocean).  The National Oceanic and Atmospheric Administration (NOAA) this past summer issued a forecast that an El Nino was likely to develop for this upcoming winter which prompted many individuals to email and talk to me about our upcoming mild winter.  Yet, there are serious doubts if an El Nino will develop (so far it has not), plus as we learned during the 2009-2010 winter, an El Nino is no guarantee of a “soft” winter.

The weather is far more complicated than a fancy term.

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.

Will it be 4?

The equatorial Pacific Ocean continues to cool at a very rapid rate.  The transition from last year?s El Nino to our current La Nina was one of the fastest transitions observed.  An El Nino, in simple terms, is when the water along and near the equatorial Pacific is warmer than average and a La Nina is present when the water temperatures are running below average.   Right now the La Nina conditions in the Pacific Ocean are the strongest since 1955.  The weather we have been experiencing in recent weeks has been fairly typical of other La Nina autumns in the past.

I have written before that no one variable will guarantee this area any type of weather for our upcoming cold season. With that in mind, in the past 60 years, all the winters that had La Nina conditions of this magnitude ended up with temperature averaging below normal except one.

Therefore, at the moment, the odds favor another colder than average winter for this area.

Spring Forecast

I was asked to write a spring outlook for the North Dakota Climate bulletin which covers our past winter season in the state of North Dakota.  I am posting my thoughts here as well:


The North American continent during the winter of 2009-2010 was dominated by two principle players; an El Nino in the central Pacific Ocean and a strong negative Arctic Oscillation. An El Nino occurs when the waters of the equatorial Pacific are warmer than normal. This extra heat energy into the atmosphere tends to enhance the sub-tropical jet stream making the southern tier of the United States cooler and wetter than normal, whereas the polar jet stream that impacts North Dakota tends to shift into southern Canada bringing above average winter temperatures and below average precipitation (snowfall) to the state.

Although the southern tier of the United States generally saw winter weather typical of most El Ninos, North Dakota and other northern states did not. Although in a complex atmosphere there are always numerous unknown reasons that could be players, one reason this area finished colder than would otherwise be expected could be blamed on a phenomenon referred to as the Arctic Oscillation (AO). The AO is a climate pattern characterized by winds circulating counterclockwise around the arctic. When the AO is in its positive phase, a ring of stronger winds circulating around the North Pole tends to keep the coldest air in the higher latitudes. In the negative phase of the AO, this belt of winds becomes weaker allowing arctic air to more readily move southward bringing bitterly cold air to the state.

In recent months the Arctic Oscillation has been strongly negative several times which not only impacted our weather, but also conditions throughout the lower 48 states. The Arctic Oscillation can impact seasons besides winter; it was a strong negative AO that helped produce the cold summers in 2004 and 2009 and could also be a player during the spring of 2010.

According to research being done by Rob Kupec a meteorologist at WDAY-TV in Fargo, ND as well as a graduate student at North Dakota State University, spring seasons in North Dakota when an El Nino is still present, like this year, tend to finish with slightly warmer than normal spring seasons. But a three-month average often means little if the warmer conditions come in March or early April before the planting season begins. Also, if the warmer Pacific Ocean does not fade by May, wetter than average conditions often arrive during the spring planting season.

These factors as well as the Arctic Oscillation continuing to be a player seems to be increasing the odds for the latter half of the spring being cooler and wetter than normal during the beginning of the growing season after the warmer than average start to the season.

The North Dakota State climate Office has links to the National Weather Service’s local 3-month temperature outlooks for the upper coming year. Those outlooks can be found here:


The latest spring outlook from the Climate Prediction Center is giving equal chances for the spring season to be either average, above average or below average for both precipitation and temperatures throughout the state and considering the wide weather fluctuations we will likely experience in the coming weeks, that seems to be a valid analysis.

Those outlooks can be found at http://www.cpc.ncep.noaa.gov/products/predictions/.

Mild January?

I have been asked frequently in the past couple of weeks if I thought warmer weather would return in January. Most of these questions originated with comments on how September was warm, October turned cold, then the warm weather returned for November and of course, this month then turned cold. Granted, we have been in a four week pattern the last several months, but that in no way means that January will magically end up above average.

Two factors that may limit any potential warm up in January is the extensive snow cover over the Northern Hemisphere and general colder than average temperatures being experienced in both North America and Eurasia in recent weeks. El Ninos tend to have their greatest impact on the northern tier of the United States during January and February. That at least gives us some hope that more temperate air may move into the area in the coming weeks.