Garrett’s Blog: El Niño in Arkansas
If you been following the news recently, El Niño is all the buzz. The discussion started when a climatologist for NASA’s Jet Propulsion Laboratory said the upcoming event had the potential to be the “The Godzilla of El Niños”.
Godzilla aside, it does appear that this warming phenomena could be one of the strongest on record if the computer modelling verifies… and there is high confidence that it will; instead of just a few models showing the warming, all of them are showing it to some degree.
So what is El Niño and what does it mean for Arkansas?
El Niño is a warming event that occurs in the Pacific Ocean. The Southern Oscillation Index is calculated by determining the pressure difference between Tahiti and Darwin, Australia. The pressure difference drives abnormally wet or dry conditions which affect temperature. The affect on temperature causes upwelling leading to cooler than normal conditions and also affecting the micronutrients that exist into the lower portion of the ocean which affect plant and fish life in both positive and negative ways which in turn affect economies & ecosystems across the Pacific.
I went back to 1975 and pulled the 3-month winter average of the El Niño Index. I omitted most low values with the exception of the last few years to show you some of the stronger El Niños in recent memory compared to this winter. The effects of El Niño are most apparent in the winter months. You can see how this upcoming event is strong.
There are many effects of El Niño but I included the most basic on this map. The warming in the Pacific causes a stronger than normal subtropical jet stream. This is why California gets hammered with rain and mudslides in El Niño years. The influence of the southern jet causes wetter than normal weather in Arkansas. El Niño will typically limit the Arctic Intrusions and massive southern plains cold air outbreaks with the Polar Jet bottled up in the north east.
That doesn’t mean there’s a 100% guarantee this winter will be warm and snowless. A lot of it will depend on two other global features: The Arctic Oscillation & the North Atlantic Oscillation and those values are more difficult to forecast months in advance.
In the past two strong El Niños in Arkansas it did snow very little snow in the months of November thru Feburary. These values are for Fort Smith, Arkansas but Fayetteville recorded only 1.3″ in ’82-’83 and only 2.5″ in ’97-’98.
I noticed that some of the moderate El Niño events still produced an average of around 6″ of snow for the entire winter in our area. But none of them produced above average snowfall.
One thing that is more certain is a wetter than normal winter. When averaging all of the El Niños in Arkansas, we typically receive over 100% of normal rainfall. The ’82-’83 El Niño is more impressive with some locations in the Natural State picking up rainfall 248% of normal!
There is some research that shows a lower frequency of tornadoes in Arkansas during the winter season.
This image is from a recent study that shows a DECREASE in tornado activity in Arkansas during El Niño years (Top Map) The bottom map is La Niña which is a cooling in the Pacific and the opposite of El Niño. (Allen et al., Nature Geoscience, 2015 which was cited on a Weather Channel Blog recently).
This comparison animation appeared in the LA Times this week and prompted the discussion about the increased likelihood of an El Niño winter. You can see computer simulations are showing an increased warming greater than 1997-1998 which was one of the strongest on record. The warming is the bright white along the equator.
If you’d like to read more, this website has a great history of past year’s events.
The Climate Prediction Center has a great discussion, too.
More about the Climate in Arkansas and El Niño’s affects can be found by downloading the state climate report .
I know this is a lot of information with a lot of unknowns.
The bottom line is that this winter will probably have more rain than average and probably a lower number of snow days. The severe weather in the winter should be less; however, if El Niño continues into Spring a more active southern jet could mean a more active spring severe weather season.