It’s that time of year again when your favorite meteorologists take a stab at predicting an entire season. And like always, we have to remind you that seasonal forecasting is still a very early science-meaning, it’s based on a lot of theory and still has a way to go before becoming ‘good’.
That being said, we are learning new things every year and this year there are several good indicators leading us to a higher confidence in our outlook.
So here goes…
For the science lovers, here’s what we are looking at to make our forecast:
A weak to moderate El Nino is forecasted for this winter, however, the concentrated warmth of this El Nino is more toward the central Pacific and not the eastern (typical El Nino). This is called a central-based or Modoki El Nino. (See Image)
El Nino years bring about a stronger southern Jet Stream and can mean more storms for the East Coast. Typical El Nino years bring New England more wet than white winters, but the central-based El Ninos tend to bring us a bit more snow. It’s also important to note that the second half of El Nino tends to be a busier time for the East Coast(which is getting into February and March).
We are at a solar minimum in the cycle (which spans 11 years). With the lack of sunspots, theory suggests there is a greater risk for a colder than normal winter in the US. (See Image)
Research scientists recently found a correlation between the advance of snow cover over Siberia in October to a weakened polar vortex and bursts of cold and snow for the Eastern US. This year, the snow advance began slow, then dramatically sped up at the end of the month. In fact, the snow advance continues to be rapid in November as well. There is speculation on what this means for the East, but signs point to a colder and snowier result.
North America Snow Pack
Fall snow has really taken off across North America and into the Northeast. Cold air tends to follow where the snow cover has advanced, so this has helped to keep November quite cold in the Northeast. This trend should continue into the start of the winter season. (See image)
QBO-Quasi Biennial Oscillation
The “Quasi-Biennial Oscillation” occurs in the stratosphere, and it tends to shift direction every few years. During the transition periods, blocking patterns in the upper atmosphere occur more often. Blocking patterns, especially in El Nino years, favor more (and stronger) Nor’easters. If it happens to be cold enough, that means snow.
The QBO index tends to have a steady trend, and it is trending toward the transition period.
The AO or Arctic Oscillation is a measurement of surface air pressure difference from normal at the high latitudes over and north of Greenland. When the pressures are lower and the Polar Vortex is stronger, we are in the positive phase. When the opposite is true, we are in the negative phase.
When the AO is positive, Arctic air gets trapped closer to the poll and the Northeast tends to get milder conditions. When the AO swings negative, the Polar Vortex weakens and lobs of Arctic air sink farther south into the lower 48.
The NAO or North Atlantic Oscillation is the measurement of the differences in air pressure over the North Atlantic Ocean. When the NAO is positive, the sub-polar low and subtropical high are stronger than average, which results in quieter, milder weather. When it is negative and the high and low over the North Atlantic are weaker, the result will be stormier and more cold outbreaks.
For the Northeast, these oscillations are the biggest game players. When both the AO and NAO are negative, it’s a very likely bet we are going to get hit with some cold and snow. Most of the big snow storms occurred when these were both negative. (See Images)
Forecasts for these are tricky and can really only be seen a few weeks in advance. Other big items help to give us an idea about an AO/NAO trend, like Eurasian snow, the Blob, etc.
The ‘Blob’ is a nickname given to a large pool of warm water off the coast of Alaska and Northeast Pacific Ocean. In the past, when this water is unusually warm, a ridge of high pressure will form over western North America and a trough hangs tough in the East with colder, stormier weather (what we’ve seen this November!).
Long Range Forecast Models
These are always to be taken with a grain of salt, however it has been noticed that there is a good amount of agreement with several long-range models for a colder, snowier pattern to persist in the East.
Our forecast for western Mass for the winter is trending colder and snowier than normal-but remember this spans over all of December, January and February and doesn’t tell the whole story.
Breaking it down a bit more…
December is looking to trend colder than normal, but should have some breaks of milder air in the mix too. Snowfall should be near to slightly above normal.
January is looking to vary with shots of cold and shots of mild air. Snow should be near normal. And rainfall may be above normal.
February is looking like the busiest month with more Arctic outbreaks and bigger snow events. If we end up with a ‘big’ snow, it should be this month.
While meteorological winter ends with February, snow of course will continue for New England and March is looking potentially busy as well with an active storm track. If enough cold air can come through (which it should) we could see more snowstorms and Nor’easters.
(See seasonal snowfall prediction image)