So long as we keep El Nino at bay, I expect plenty of snow to be on the way

'Tis that time of year again. The days are darker and many are gloomy, the weather has gotten continuously colder and lots of snow has already been flying across the Vermont countryside. Though many don't share our collective enthusiasm, we remain steadfastly proud of our affinity for winter. Without the colder temperature and abundant snowfall, all that would be left is months of incredibly short days and an unskiable Mad River Glen. So yes, we throw out the welcome mat for another winter season on the mountain and another season of talking weather on the blog.  As always, its always a privilege discussing this stuff with this cohort of winter weather fanatics, many of them skiers at MRG but plenty of others who engage in an assortment of snow-related activities across the state. 

The scary blob of red off the coast early this fall

I will admit to harboring some rather serious trepidation about the coming winter season through much of September. It wasn't simply the continuous stretch of warmth that encompassed all of New England from July through September but rather what I believed to be the major cause of that warmth. Though never attaining any serious attention from my blogging efforts, sea surface temperatures, regionally speaking, like within several hundred miles of the New England coast, do play a rather significant role in the weather across all of of New England not just coastal sections. There's some neglect to go around for not discussing SST anomalies more often on a regional level but I don't recall ever witnessing a time where sea surface temperatures in the Atlantic achieved such a warm state in a relative sense. The impact was undeniable and several of our favorite regional weather personalities made a point to mention the number of days featuring 70-plus dewpoints or 65-plus dewpoints or the number of nights where temperatures failed to break 70 or 65. It may not have been the hottest summer on record, but was arguably one of the more humid summers in a generation and perhaps more. Furthermore, coastal areas were hit with a succession of heavy rain events, many of which caused localized flooding and have largely contributed to well-above normal rainfall amounts for the year. Vermont has largely avoided this and rainfall amounts of remained in the rather ordinary range during the summer and also during the autumn months. The anomalous warmth persisting in the coastal Atlantic Ocean waters and the apparent feedback resulting from it, on a regional scale, caused a bit of a fire alarm regarding my thoughts on the upcoming winter. We had to somehow rid ourselves of this warm blob in the Atlantic or else face some rather difficult headwinds. Fortunately, we have for the most part. Whether it be attributed to the pattern shift in mid-October, localized storminess or localized chaos of ocean currents, much  of the warmth that was focused along the New England coast has been swept well to the south and water temperatures have returned to normal, and with that, we can go back to our regularly scheduled programming. 

Sept SST's 

Nov SST's 

What's up with El Nino 

The state of the ENSO invariably plays a large role in pre-season outlooks and along with the aforementioned coastal Atlantic Ocean water temperatures, raised some alarms. Us Vermont powderhounds are likely still feeling pretty wounded after the 2015-2016 Super Nino abomination. Any talk of a coming El Nino is thus not likely to foster much positive energy. Though those feelings are quite understandable, large distinctions need to be made regarding various ENSO events and the stark differences between the varying intensities of El Nino and the overall impact it has on New England winters. The Super Nino years, particularly the last two ('97-'98 & '15-'16) both featured exceedingly mild temperatures and only in the former were we able to scrape out some halfway decent snowfall. Many of the El Nino years in our recent sample size however can be more accurately catorgorized as weak or garden variety and those have yielded considerably different outcomes for Vermont especially on the temperature side. The concern this year was that a weak El Nino would quikcly evolve into a much stronger event but those concerns, just in the last two weeks have eased as temperatures in the critical regions of the equatorial Pacific have relaxed somewhat.

This isn’t to say that garden variety El Nino winters or weak El Nino winters guarantee us a season of epic ness. The many in our sample size have yielded mixed results but one thing is clear in the aggregate, El Nino’s of the “weaker” variety have a much more subdued impact on temperature. Furthermore, a few in our sample size that I’ve shown below turned out to either somewhat or even more significantly epic. The key figure to watch are those actual SST anomaly values in the critical regions of the equatorial Pacific. If we can keep those numbers below 1.5 C or better yet 1 C above normal then we have a much better shot at avoiding the extended blowtorch that often accompanies stronger El Nino or Super Nino winter seasons. Let us not forget that there is one very positive byproduct of most El Nino, the revved up southern branch of the jet stream, responsible for juicy southern streamers that have been known to produce big east coast snows across both coastal areas and the interior. We’ve already gotten one of those and we aren’t yet though November. So long as we can keep El Nino somewhat alive there will be more to come. 

In the below graph, I color coded the temperature results and then gave a verbal description of how the actual snow season was. 

Watching the Pacific as always 

The next variable on our checklist is the PDO or the Pacific Decadal Oscillation. We’ve watched this “bad boy” every year. The PDO describes the configuration sea surface temperature anomalies across the mid-latitude more generally and geometrically as opposed to the ENSO (El Nino/La Nina) which specifically relates to whether water temperatures are above or below normal in equatorial regions. At first glance, the PDO doesn’t appear to tell us a lot this year. The last reading of .09 is pretty neutral on the scale of things. The super +PDO winter of 2014/15 had an index well above 2 by way of comparison. That said, water temperature anomalies, specifically in the Gulf of Alaska and over the Bering Sea have been especially noteworthy. 

The Bering Sea water temperatures have a lot to do with the incredible loss of sea ice in that region over the last years. Yes, some of it relates our warming climate which has had strikingly massive impacts at high latitude regions such as the Bering Sea. Some of it is also variability. The Bering Sea is just a particular region where sea ice has been running especially low recently, in other arctic regions, it has been higher. The loss of this ice however and persistent warmth in that region has created a blob of anomalous sea surface temperature warmth that is especially noteable. When climate scientists attribute mid-latitude cold waves to the warming climate, they are often referring to the altering of the polar air pathways that are induced by some of these sea surface temperature features. In the case of this year, much of this warmth in the Bering Sea extends to the Gulf of Alaska. If this blob of warmth remains in this locale, the pattern will tend to favor more high latitude ridging in western North America and troughing and general storminess focused on eastern North America. Interestingly, this is exactly what has transpired when this particular sea surface temperature pattern developed. 

Seasonal SST Animmations in Paciific Ocean

Snow and Ice expansion so far  

Last on the list of “measurable” variables is the build-up of snow and ice on a hemispheric scale. Though one can argue on the validity of some of the inferences drawn from using this data, I tend to be among the people that considers it an important item to watch. We’ve seen some very healthy build-ups of snow in the autumn months over the last 6 winters or so. A few of these winters turned out to be pretty cold, and a few were taken over by El Torchy. The build-up of snow actually got off to a pretty slow start this autumn but picked up substantially in October and the final number that month was 20.06 (millions of square KM’s). This is above the 50-year average but the lowest value since 2011. It’s probably not a good year to use this variable as a serious determinant and focus instead on other factors.

Snowcover departure  

Interactive Sea Ice Chart  

Any tells ? 

Lastly, I want to focus a little on any atmospheric “tells”. You know, how a seriously flawed Texas Holdem player might act when he gets dealt a pair of kings and manages to get the entire table to fold before any bets are placed. Mother Nature is actually a much more skilled poker player. She might reveal a few things about the way she might behave in advance of a winter but she can throw a bluff your way as well and lead you straight to prognosticator purgatory. Still, who can’t resist a game of poker with Mother Nature so lets play. 

The two things that stand out about the weather in the past 6 months is what was mentioned above about regional sea surface temperatures in the North Atlantic. We absolutely needed to rid ourselves of this plague and we did it in the nick of time. More importantly, it is the way we did it. An abrupt pattern change that allowed the weather to go from summer in Vermont with warmth and humidity in early October to snow and very chilly temperatures in late October. Since then the pattern has largely been driven by a very negative EPO or loosened Pacific Jet. Long gone is any hints of an “Evil Empire” in the Pacific and this has stood out to me and largely driven the very cold/snowy pattern in recent weeks. Basically, we needed something overwhelming eliminate some of that problematic ocean water on the Atlantic Coast and we got it. The EPO, the Andrew Benintendi of variables, coming through in the clutch turning around what appeared to be a less than mediocre winter outlook. 

The actual forecast for this season 

So lets get some of that “Andrew Benintendi” into a forecast for the winter. I still retain a bit of consternation on temperatures. El Nino is El Nino and most of those are on the warmer side of average, even the weaker ones. If we keep El Nino in check, the adverse effects on temperatures that we typically see in strong ENSO winters will be negated mostly by the EPO, which seems intent on assuming a more negative state for reasons discussed above though it will fluctuate. When the EPO does fluctuate we are likely to see some adverse conditions. Overall, I would still predict that temperatures come in on the above side of average aggregating over the entire ski season but not by much. If the forecast period begins on opening day, now slated for November 24^th and ends sometime in early to mid April, I would expect temperatures to come in between 0-2 above average. Last year came out about +1 over the same period which as you might remember, including both some very cold and some very warm. 

Where we should see a noticeable difference relative to last year is on the snow side. The winter storm which slammed the eastern seaboard on November 15th, foreshadows what I believe will be a very active winter full of juicy east coast storms systems. The combination of the weak El Nino and negative EPO will be the culprit for what I believe portends a stormy winter season. We have to expect a significant slump in conditions at some point and we also have to hope that the storm track is favorable enough to deliver us a chunk of the goods. My expectation however is that it will, we will have an above normal snow season, and a good ski season overall shared largely with other locations across the eastern United States. So with that, another season begins with the earliest opening I can remember in at least 15 years.Get after it !