Let's cut to the hunt. We are looking for a cold and snowy winter. But how much snow? And how low will the temperatures go? I measure several important factors to reach that conclusion.
It started in 1997 with a look at something I had just seen a couple of times earlier. A large area in the tropical Pacific, larger than the US size, became much warmer than normal. They called it an "El Nino". I had just read research showing the potential link between strong El Nino and hot, wet and untouched winters in eastern United States
So I went to the air and predicted an oseasonably warm winter with very little snow. We had a record warm winter and our total snow was less than an inch. It got some attention. Now a winter forecast is expected each year in November.
Few winter forecasts are as simple as 1997. Major El Nino can still count to give us warm winters with little snow. But most years are not so.
"It's just like …"
We have learned that there are many more factors in the ocean and the atmosphere that can help us with seasonal forecasts. We also know that no two winters are the same. There is always a part of the ocean that is different. So there is no such thing as a perfect "analogy" year. But some have many similarities.
Whether we have an El Nino or the opposite, La Nina, it often makes a big difference. But it's not clear when it's on the weak or moderate side (like in most years).
1. EL NINO
It's not just about El Nino vs. La Nina anymore. Where El Nino is most concentrated is also important. Most El Nino covers much of the Tropical Pacific. Less often, Central Tropical Pacific has the most concentrated heat. It is called a "Modoki."
While many El Nino lead to warmer winters, Modoki Nino tends to be cooler and snowier, especially if it's in the weak or moderate category.
This winter: Weak to moderate MODOKI El Nino …
FAVORS COLDER AND SNOWIER NORMAL
2. NORTH PACIFIC "BLOB"
We have seen it several times this decade. A large area above normal ocean temperatures in the North Pacific. This leads to higher pressure developing around Alaska and Northwest Canada, which forces the Arctic air into the eastern US
The red colors on top, just outside Alaska and Western Canada, show the current "Blob". It is an important factor in what our winter will look like.
This winter GET MORE ARCTICAL INVISIONS
3. EURASIAN SNOW IN OCTOBER
It's more of an indirect impact, but a fast snowfall in October halfway around the world is linked to winter cold and snow in the eastern US
This year, snow protection in Eurasia began very slowly, but advanced rapidly towards the end of the month. My research shows that the combination as the most beneficial for winter is snowing for us.
So, this winter GET MORE SNOW
"Quasi-Biennial Oscillation" appears far up the stratosphere, and it tends to move the direction a few years back. During the transition periods, blocking patterns occur more often in the upper atmosphere. Blocking patterns, especially in El Nino years, benefit more (and stronger) Nor & # 39; easters. If it happens to be cold enough, it means snow.
The QBO index tends to have a steady trend, and the trends towards the transition period.
This winter GET MORE SNOW
5. SOLAR ACTIVITY
This is a little controversial among the meteorologists, but there seems to be a correlation between particularly low sun protection potential on the sun and colder and snowier winters in the United States
The picture below shows the clear sun protection area in recent decades. Some of our cruel winters have occurred near the bottom of the bike, when there are hardly any sun rays. We happen to be right near the bottom of this year.
This winter GET MORE COULD AND SNOW
6. AO, & NAO
What happens in the Arctic and the North Atlantic can be as important as the Pacific. But things like the Arctic oscillation and the North Atlantic oscillation have been almost impossible to predict months in advance (unlike El Nino, QBO and "The Blob"). So they are always considered a "wild card"
A negative AO means unusually high pressure on high levels across the Arctic. This forces the coldest air south in Canada and the United States and forces the Polar Jet Stream further south than normal. The record winter 2013-14 contained several giant snowstorms with a strongly negative AO.
When NAO is negative, high pressure is centered near Greenland. This pattern favors slower coastal storms in eastern United States. A negative NAO is often one of the ingredients in our largest Norwegian snowstorms.
The aforementioned Eurasia snow connection can be connected to -AO. So maybe it can be predicted.
7. MELTING ARCTIC ICE & CLIMATE CHANGE
It has become increasingly evident to many forecasts and climate scientists that the massive Arctic ice melting affects weather patterns. One of the consequences is in more blocking patterns, including -AO and -NAO.
It is probably not a coincidence that 3 of the 4 largest snowstorms in Philadelphia occurred in the last decade or so (2009, 2010 and 2016). The combination of more blockage and more water vapor due to the warming climate is a recipe for large snow storms – if it's cold enough. And -AO can help with that. These latest changes must be considered when making seasonal forecasts.
8. SEASONAL COMPUTER MODEL FORECASTS
Until recently, specific forecasts for computer models are not considered useful by most forecasts. But as our knowledge about the atmosphere and models improves, the forecasts have. Now, I really care what they are showing (of course, the American model GFS is least trusted in this area). The European and UKMET models have recently predicted patterns that favor cold and snow for us. And so, they have Canadian and Japanese models. There is a lot of agreement.
This winter FAVORES MORE COLD & SNOW
The forecast (finally!)
So you see, almost all the important factors that I'm looking at lean towards more cold and snow in winter. The only questions in my mind are: "How cold and snowy do I go?"
The answer lies in looking at previous years with similar conditions called analogues. The analogues for this year show a dramatic pattern, especially for February.
The first map is February average about 20,000 feet up in the atmosphere – a key level for forecasters. The lower pressure in the northeastern US is extreme for a map like this. And the very high pressure across Greenland proposes a strong NAO. The combination SCREAMS East Coast Snowstorms!
And the above map showing February temperatures follows the upper air pattern: oseasonably cold in eastern US
Based on the above reasoning and watching analogue years …
First, highlight some
* colder than "normal" winter
* snowier than usual winter
* called in relation to normal: February
* Snowstorm: February (by far)
* 2 big snowstorms in February
* A cold december with over normal snow
December 7 "-2.0 degrees
8 "January 1.0
FEB 16 "-3.0
4 "March -1.0
TOTAL 30-40 "(" Normal "is 22.4")
For other cities in our area, here are my estimated seasonal forecasts:
Allentown 50 "
Downing 45 "
Wilmington 32 "
Atlantic City 28 "
Millville 26 "
Poconos 85 "
Believe it or not, it's possible that I could be too conservative with this forecast – not enough snow or cold. But the patterns that look good looking now can change in the coming months. In any case, this should be a winter worth watching, as some will love and some will hate.