SYRACUSE (WSYR-TV) - Here are the short headlines for the Storm Team’s 2018-19 Winter Outlook
- Snowfall will average a bit above normal (120”-140”)
- Temperatures over the heart of winter (December-February) turn out below normal
- While winter will not drag on as long as last year, Spring will not arrive early.
Here is the more in depth reasoning behind our forecast.
El Nino Returns
We believe the biggest driver of this winter’s weather is a developing El Nino.
El Nino is described as warmer than normal sea surface temperatures in the equatorial Pacific Ocean. This happens every 3 to 7 years and can impact jet stream patterns across the globe. The last El Nino occurred during the Winter of 2015-16.
Not all El Nino’s are equal. Some are stronger than others. In other words, the Pacific waters are warmer for some El Nino events compared to others. The last time an El Nino happened in 2015-16 it ended up as one of the strongest (or warmest) El Ninos on record. Scientists have been tracking the development of the current El Nino for months and all signs point toward there being a ‘weaker’ El Nino this winter. The latest forecast from earlier this month put the odds of an El Nino up to 75%.
While there are no ‘slam dunks’ when using past weak El Ninos to make winter forecasts for central New York there are definitely some ‘trends’
When it came to seasonal snowfall we are playing the law of averages. Looking back at our sample of 10 weak El Nino winters since 1950, seven of those winters (70%) had near or above normal snowfall. Only three of the winters had below normal seasonal snowfalls and only one of those winters (1979-80) came after the mid 1950s. We feel our seasonal snowfall for 2018-’19 will run between 120”-140”
One of the reasons we issue our Winter Outlook this late into November is because we like to see how weather patterns unfold in the Fall. One of the more reliable Fall predictors we have found for Syracuse winters is that a wet October tends to be followed by a snowy winter.
Syracuse had 4.19” of rain this past October making it the 17th wettest since records have been kept at the Syracuse airport.
Looking at the top 20 wettest Octobers since 1949, 65% of the following winters had 130” of snow or more. Only 15% of the winters had less than 100 inches. That makes us more confident in a slightly above normal snow forecast.
We don’t know exactly the underlying cause for this connection; perhaps it is the overall October patterns that bring us wet weather are ones that tend to repeat during the winter months.
When it came to making the temperature forecast for the winter, we struggled a bit. While some computer models we look at are pushing above normal temperatures for the winter, a look back at past weak El Nino winters tells us something else.
Six out of the 10 weak El Nino winters (60%) ended up with December through February periods with temperatures that were below normal. Even in two of the overall warmer than normal winters (1953-’54 and 2006-’07) one of the three winter months ended up with substantially below normal temperatures. In other words, even in warmer than normal weak El Nino Winters there is some variability in temperatures with some prolonged cold stretches.
Because of what we see from past weak El Nino Winters we are going to go with a colder than normal winter overall.
As an added bonus, we are forecasting the number of below zero days this winter to come in at between five and ten days. That puts us in the normal range for a typical winter which is 7 days.
Late Winter Trends
While we don’t think winter will drag on for as long as last winter, for those hoping we are due for an early Spring (i.e. early to mid March) , that doesn’t seem to be in the cards. A large majority of past weak El Nino years (80%) had cooler than normal temperatures in March. Interestingly, though, only two of those winters had significantly more snow than normal in March.
However, the odds of us having a colder than normal April are low so even if we don’t catch a break in March at least by April things will turn to more Spring-like weather.