Record El Niño Possible, What It Means for Us

NOAA Expects A Very Strong El Niño, How Does That Affect Our Winter Weather?

About three months ago, the National Oceanic and Atmospheric Administration, also known as NOAA, announced that the world could be in for one of the strongest El Niño events recorded in history and that this even would rival that of the strongest El Niño ever recorded from 1997-1998. But what does that mean for our winter weather here in the KDLT Viewing area?

First we will start with the definition of an El Niño. An El Niño occurs when the surface temperatures of the eastern Pacific Ocean along the Equator are warmer than normal. The contrary is La Niña, which is when there is cooler than normal sea surface temperatures in the eastern Pacific. This progression of the Pacific Ocean water warming and cooling is called the El Niño Southern Oscillation, also known as ENSO.

El Niño can impact the weather across the globe, affecting rainfall, air temperature, drought conditions, and even the development of tropical storms around the world. Many believe that this could be just what the doctor ordered for California’s historic drought.

Earlier this year, sea surface temperatures in the Eastern Pacific began to rise, bringing on El Niño conditions. Now forecasters are calling for a possible record breaking El Niño this winter with sea surface temperatures of 3.6 degrees Fahrenheit, which equates to 2.0 degrees Celsius, above normal. To put that in perspective, there have only been THREE instances in which we have recorded a three month average Oceanic Niño Index (ONI) value of 2.0° C above normal. Those occurred in the El Niño events of 1972-73, 1982-82, and 1997-98.

Since 1950, there have been 23 El Niño events and 20 La Niña events recorded. We list each El Niño event into four separate categories based on how strong their peak ONI was. Those categories are listed as “Very Strong”, “Strong”, “Moderate”, & “Weak”. For the purpose of this study, the only events we will concentrate on are: Very Strong, Strong, and Moderate. Those years are listed in the table below.

The warmest/strongest El Niño ever record was the 1997-98 El Niño, which had a peak three month ONI of 2.3° recorded twice, once in the October/November/December time period, as well as the November/December/January time period.

Currently, the sea surface temperature anomalies are showing that the water along the Equator in the Eastern Pacific is 3.0° warmer than normal. This can be seen in the image below.

This has recently set the record for the strongest ONI for an El Niño all time, breaking the previous high mark set during the El Niño event in 1997-98. Below is a graph comparing the of the ONI for this year to the El Niño of 1997-98. As shown, we are already on track to blow the El Niño of 1997-98 out of the water, no pun intended.

Now that we have taken a look at some previous El Niño events, and have an understanding of what that means, we can now make a forecast on what we should expect for this winter.

Earlier in October, the Climate Prediction Center (CPC) issued their Winter Outlook, calling for warmer than average temperatures and equal chances for precipitation across the KDLT Viewing area for this winter.

While this forecast is close to what we have at KDLT, it is done on more of a National scale. I am going to dive in a little further, bringing it down to a local scale.

Some things that we need to know before moving too far. On average, Sioux Falls receives 44.5” of snow per year (Sept 1 – May 15) and sees an average temperature of 18.95° over the winter months (December – February).

In the two El Niño periods classified as “very strong”, we finished with above average snow totals. The strongest El Niño on record, 1997-98, produced a seasonal snowfall total of 49.0” and the second strongest, 1982-83, produced even more snowfall with a total of 70.5”. Both winters finished with an above normal average temperature. If we look at the “strong” and “moderate” categories, it shows more of a mixed bag. Out of the nine winters in these categories, four have finished with more snow than normal, while the other five have finished with significantly less than normal. The average temperature recorded was above normal in five of those winters, while it was below normal in four of them.

Our last moderate/strong El Niño was recorded in 2009-10 and brought us a colder than normal, as well as snowier than normal winter. That ironically, is the both the coldest and snowiest winter we have seen in Sioux Falls since the winter of 2000-2001.

After going through the previous El Niño years and their data, I have made a forecast for this winter for the Sioux Falls/southeast South Dakota area. While we don’t have too many years of moderate/strong El Niño conditions to use as comparison, we do have a handful to create a hypothesis for how this winter may go.

The following is my official winter forecast for the Sioux Falls and surrounding areas.

Snowfall Forecast:
ABOVE NORMAL – 45 to 55 inches of snow

Temperature Forecast:
ABOVE NORMAL – 23.0° to 25.5°

We have been off to a slow start to winter with the second warmest 15 day start to the month of November in Sioux Falls history. That all changes this weekend as our first snowfall of the season is expected to move in Friday, the 18th.

-Brandon Spinner
Chief Meteorologist