Welcome to my 2020 / 2021 Winter Outlook. As many of you know, THIS is my favorite time of the year. We will answer questions such as, “Will it be a cold winter”?, or “Will it snow heavily”?
What I can tell you is as always, we will see a multitude of conditions throughout the winter season. This year we should get familiar with the phrase “La Nina”. Let me dig in and I hope you enjoy!!
What is La Nina?
La Niña is a weather pattern that occurs in the Pacific Ocean. In this pattern, strong winds blow warm water at the ocean’s surface from South America to Indonesia. As the warm water moves west, cold water from the deep rises to the surface near the coast of South America.
So... How will this Impact Our Winter?
A La Niña advisory is in effect and I believe that there’s an 85% chance that it will continue through the winter.
That could mean a snowy winter for the Hudson Valley, New York City, Long Island, New Jersey, and Connecticut region. But….. I have heard this before and then Woooomp Woooooomp. Nada.
The strongest signals from La Niña are with temperature. On the whole, La Niña winters result in warmer-than-average winters in NYC and this is the official forecast from NOAA for this winter.
Six out of the nine La Niña winters had above average temperatures and two of those winters ranked in the top 10 warmest.
The average winter temperature for NYC is 35.1 degrees. The average temperature for a La Niña winter in NYC is 35.9 degrees. With a warmer-than-average winter expected, you may think that would also mean a low snow year, but that might not be the case.
NOW, Let’s explore the snow stats for La Niña winters in NYC.
Let it Snow??
The snowfall numbers for La Niña winters may surprise you, but they also are a bit misleading. Last winter’s snowfall in NYC was only 4.8″. The average snowfall for NYC in a typical winter is 25.1″. The average snowfall for La Niña winters is 39.2″. On the surface, it seems like a closed case: La Niña equals a snowy winter for NYC.
When we look closer, though, we find that the small sample size can yield deceiving results. Five out of the nine winters in the study did result in above normal snowfall, but one winter was an anomaly.
In the winter of 2010-11, we had 63″ of snow. That’s the third-most for NYC. That winter skews the snowfall average greatly. If we eliminate the La Niña year with the most snow and the La Nina year with the least snow (8.1″ in 1988-89), we get an adjusted average of 24.5″.
So what are my Thoughts?
After looking through the trends and data, we are seeing that there isn’t a clear answer. A La Niña winter is a not clear indicator for a “bad” or “good” winter. There’s no 1+1=2 relationship.
However, the trends are clear that, on average, La Niña winters are warmer than normal and that snowfall is typically near normal. What we don’t know is if we’ll have an outlier year like in the past, when we had record snowfall or record warmth. This case illustrates the limitations of long-range and seasonal forecasts.
We can tell the trends but we can’t tell the precise future. This is similar to when forecasters come up with hurricane season forecasts in the spring. These are getting more accurate each year, but one thing we can’t determine is where the storms will make landfall until they actually form.
So, for winter 2020-21 in NYC, it’s a good bet that we’ll have warmer than normal temperatures and it’s almost a certainty that we’ll have more snow than last year.
- NYC– Average to Slightly Below Average Snowfall
- Westchester & Rockland- Slightly Above Average Snowfall
- Northern NJ- Slightly Above Average Snowfall
- Central NJ- Average to Slightly Below Average Snowfall
- Southern NJ- Below Average Snowfall
- Long Island- Average to Slightly Below Average Snowfall
- Connecticut- Slightly Above Average Snowfall