By March snow was piled up three to five feet burying fences in some areas.
Since we are breaking record high temperatures, it is a great time to remember and review our latest La’Nina Winter. What happened?
The Pagosa Springs area had a lot more then average snow during the recent winter of 2022/2023. In fact, it is tied with the winter of 2018/2019 for the third most snow at Wolf Creek Ski Resort in the last 46 years! Interestingly local myth holds that if we have a La’ Nina winter, we’ll have less snow than average and if it is an El Nino Winter, we’ll have more snow than average. This past winter exploded that myth!
So what happened? Why did we get so much of the beautiful white stuff? Let’s start by looking at exactly how snow we did get.
Note: My Seasonal Outlook forecast from October 2022 contains explanation of the oscillation patterns discussed in this article. https://pagosaweather.org/2022/10/13/pagosa-springs-winter-outlook-22-23/
Pagosa Springs Area
The total for the season was 124.7″ – 24.4″ above the average of 100.3″. Snowfall from October to December was less than average, as expected. Snow really picked up in January and it was our snowiest month.
Note: 1. There are inconsistencies in our historical data. 2. The location of our historical data moved around the Pagosa Springs area. Because of our terrain, just moving a mile or two in any direction results in significant differences. 3. We use an average from individual monthly CoCoRaHS totals that include at least 60% of the daily reports. This is not precise but gives us a good idea where we stand. 4. Stevens Field is the official observation point for Pagosa Springs but they do not record precipitation and they certainly do not measure snow.
Wolf Creek Ski Resort
January and March were big months up at Wolf Creek Ski resort in 2023.
Notes:
1. For years there was someone living at Wolf Creek Pass near where the transportation shed is now. Based on the records that we have, it was for 44 years from 1957 to 2001. However, there were often long period of times, where during the winter when no one was there measuring the snow. But based on the records that we have from that time period the average mean for annual winter snowfall at Wolf Creek Pass was 435 inches.
2. Wolf Creek Ski Patrol has records dating back to 1976 or the last 47 years. They only measure the snow when the Wolf Creek Ski Resort is open which varies wildly from year to year but it gives us a good consistent record during the big snow months from December through March. Their average mean is only 360″. Again, most years they’re missing the early and late winter months.
El Nino Southern Oscillation Study (ENSO)
Using the data from Wolf Creek Ski Resort, I did a study to determine if the myth of our area having more snow during an El Nino Winter and less snow during a La Nina winter is true. The results are very interesting…
From 1976 to 2023, we experienced 17 events that were considered La Nina events by the Climate Prediction Center. Of those events, only six winters were less than average snow and an equal amount, six winters were above average snow. That is not statistically significant.
Part of the answer is in looking at the average jet pattern during ENSO events. In both cases, if the polar front jet were to shift a little more south or a little more north it would impact our winter and snow accumulation significantly. That’s why I believe the answer in our seasonal forecasts lies in looking at how global oscillations are interacting with each other.
ENSO Interaction with other Oscillations
The following chart captures the last two winters that were classified as La Nina winters and how they interacted with other oscillations that could explain why different month had more than average snow.
In December of 2021 we had a very strong MJO event that impacted our area and actually accounts for a large percentage of our snow that winter in two weeks of time. In February there was a strong arctic outbreak that accounted for more snow. Other wise it was an average to less than average winter.
In 2023, the waters by February were starting to warm and the La Nina was weakening. In January, the MJO kept dissipating and reemerging in the western Pacific and marching over, impacting us, and then disappearing again. Normally it only impacts us every 30 to 60 days, not multiple times in one month. Finally, the Hunga Tonga volcano erupted in December, of 2021 in the southern Pacific. How much ash was dispelled up into the stratosphere? What sort of cooling took place based on that?
Quasi Biennial Study (QBO)
In the last 23 years we have had five winters that were classified as La Nina event winters and at the same time we had a westerly QBO. The other way we can assess the seasonal snowfall is to look at the Snotel sites that are located above each of the major river drainages throughout the west measuring the snow water equivalent. For this study I looked to see what the snow water equivalent as a percent of the 1991-2020 Median.
In each of these winters, though the myth says we should have less than average snow, the San Miguel-Dolores-Animas-San Juan river drainage is above 100% snow water equivalent on the first of April. The exception is 2021 when it was 94%. However, the Upper Rio Grande was at 110%!
Based on this study, there is a correlation between a La Nina Event and a westerly QBO. I will continue to build on this study over the years.
Closing Thoughts
We had a great winter! However, California had, as I heard one meteorologist refer to it, a “Unicorn” winter. They were slammed by one significant storm after another.
I participated in an American Meteorological seminar in which they discussed the winter in California. They discussed more the “what” of what happened as opposed to the “why”. They have been awarding a series of grants to a few universities to study what happened and to answer the “why” question. I look forward to their answers.
If you review my winter outlook forecast, my assessment of what would happen this winter was pretty close with the exception of January when we had an MJO that kept coming back to visit.
Now, next winter is going to be an El Nino winter. The westerly QBO should still be in place for the first few months. What will be the result of that? Check back with us in October!
