COLUMBUS (WCMH) - We are just five weeks out from the official start of winter 2017-18. However, in Central Ohio, snow can and does fall as early as October and as late as April, meaning the winter snow season covers a lot more time.
As of today, NOAA has a 65-75% chance of seeing La Niña continuing through the winter of 2017-18 here in the Northern Hemisphere.
What are they looking at?
Typically, what is looked at is the surface temperatures in different areas around the equator. Also, folks at NOAA also look at water temperatures at different depths in the same area. They use this data, along with other collected data to compare and follow trends that appear. This helps with the forecast certainty of a La Niña, El Niño, or a Neutral pattern.
Below is an image of Sea Surface Temperature anomalies, or the difference from normal in temperature. For example, if the normal temperature was 10C, and now it is only 8C the anomaly would be -2C
(the image below is from the Climate Prediction Center at NOAA)
Notice in this image that there is colder than normal waters along the equator (represented by the blue). The waters in this area are also getting increasingly cooler below the surface too, which may indicate an increasing chance of La Niña forming for this Winter.
What does this mean for SNOWFALL this Winter?
If you remember, last Winter we were forecast to have a weak La Niña and we did! As far as La Niña Winters go, it was the least snowy we have had on record.
During the 21 seasons on record of La Niña Winters, 12 of them have been considered "weak"
Notice in those Winter seasons, the average snowfall is just slightly above our normal of 26.7″ at 29.6″. In fact, in "weak" La Niña Winters we have had some of our wildest extremes and a lot of near normal snowfalls.
During these 21 seasons of records of La Niña Winters, we have had 6 back to backs that have occurred, and a 7th if you count the back to back to back.
Looking at this chart, it is even more confusing what to expect. I charted the 2nd season of the back to back La Niña Winters, and on the far right is the 3rd of the back to back to back La Niña Winter.
Notice the average of the 2nd season of back to back La La Niña Winter is almost identical to our normal snowfall for the season at 26.6″ vs 26.7″
However, of the 6 back to back La Niña Winter seasons, not all have been weak to weak. Below I have charted how the difference between the first winter and the 2nd winter in the back to back
- 1955-56 (+6.1″)
- 1971-72 (-9.8″)
- 1974-75 (+3.6″)
- 1984-85 (+7.3″)
- 1999-00 (-10.7″)
- 2011-12 (-16.7″)
So with the 2nd of back to back La Niña Winters up in snowfall from the first 50% of the time, that really isn't much of an indicator either.
But, when you look at the data, of those six occurrences, only 1 time have we had a weak to weak back to back La Niña Winter, in 1983-84/1984-85.
- 1955-56 (+6.1″) weak-moderate
- 1971-72 (-9.8″) moderate-weak
- 1974-75 (+3.6″) strong-weak
- 1984-85 (+7.3″) weak-weak
- 1999-00 (-10.7″) moderate-moderate
- 2011-12 (-16.7″) moderate-weak
What does the Winter outlook right now look like from the Climate Prediction Center?
Right now the 3 month outlooks for temperatures for November-December-January, and for December-January-February are both for above normal temperatures.
The 3 month temperature outlook for January-February-March is for near normal temperatures. The precipitation outlook does not favor wet or dry conditions at all during the entire Winter.
Bottom line what should we expect this Winter season?
It is still much too early to make an accurate Winter forecast for this upcoming season. I would say the likelihood that we see even less snow than last Winter is about 1%, so very slim.
The odds are that we will see more snowfall this Winter. At this point, I would put the range somewhere in the range of 16.6″ to about 26″ this Winter.
If I had to pinpoint a number as of Mid-September, I will put the number for this year in the middle of that range at 21″ for this upcoming Winter season.
Of course, we will be updating our forecast in the months to come, and if the upcoming Winter appears we might have a stronger La Niña Winter, then we will be adjusting the numbers up a bit to normal or slightly above normal snowfall this Winter.
If you ever have questions about climate, La Niña, El Niño, Winter, snow, or any other weather, email me, firstname.lastname@example.org
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