This post builds upon the work of the previous in this series on the upcoming Winter Season Forecast.
Check out the previous blog post in this series to get a good idea of what we can glean from the large climate-influencing Pacific Ocean pattern known as the "El Nino - Southern Oscillation (ENSO)" and that of the "North Atlantic Oscillation (NAO)". These are always big weather players in a three-month time-scale.
The subject of this blog post builds on the first, in which we look at what storm tracks will become most assertive for this upcoming winter. In a given ENSO / NAO scenario, one set of tracks can come to the forefront over another set, and potentially give us more clues in to what the big precipitation events are going to look like (and therefore, what our snow situation will be). In a full-on El Nino scenario, the primary big-storm track originates out of the Gulf coast states and carries up along the eastern seaboard. Strong La Ninas instead have their predominate storm tracks cut across the Ohio Valley and the Great Lakes. In more neutral events, the storm tracks are less predictable and more all over the place, but also could be said to get some of the bigger tracks from each (and thus average out to a smear across the Ohio Valley to New England).
Primary Storm Tracks in an El Nino Environment
In El Nino years, it gets a little dicey for snowfall, as the primary storm track would put a good chunk of the tri-state on the 'shadow' side of the mountains (where the mountains would block the Ohio Valley and keep it relatively dry). However, storm tracks can certainly come a lot closer to the mountains, and we can still get a pile. This fall we have not had this kind of southern-track high-precipitation system yet. Not that it won't happen soon, but it's going to take a change in the pattern to bring it about.
Primary Storm Tracks in an ENSO Neutral Environment
Primary Storm Tracks in a La Nina Environment
As we shift toward La Nina events, notice how the coastal storm tracks get pushed off-shore more quickly, and we see a lot more Ohio Valley tracks (where indeed most of the moisture falls, both rain and snow).
Now, we've also talked about the NAO as well, and the main take-away from its influence is that a negative NAO will take any storm track and shade it toward its most wintry variant, and a positive NAO will take any storm track and turn it crappy ;-)
Anticipated Primary High-Precipitation Storm Tracks for the 2013-2014 Season
This is another challenging forecasting year for consulting the tea-leaves of teleconnection patterns and long-form climate indicators. Ocean temperature anomalies, sea-ice / arctic snowpack, and what has already gone on are good indicators.
The NAO has been unfavorable for snowstorms so far this early-season, but as we discussed in the last blog post on the subject there could be an opening come December for the wintry thumb-on-the-scale.
One other bit of information that I find helpful for this particular winter season is that the coastal Atlantic Ocean temperatures are quite warm for this time of year, and have been anomalously warm since May.
NHC - Atlantic Ocean Temperature Anomalies
The 2013 Hurricane Season in the Atlantic, though getting up to the letter "M" as of this writing, was still rather lame. Many storms never reached hurricane status and more still never came close to the US mainland. The anomalies are prohibitive close to the Carolina coast, which would normally be looked for to encourage explosive storm growth. That would have to change, in my opinion, before those deep coastal systems really take off.
The cooler anomalies closer to the Atlantic coastline from Jersey shore straight south of the Carolinas can easily be explained by Superstorm Sandy and the coastal Nor'easter that came through within the span of just a week (even now, I wouldn't be surprised to see these anomalies south of Cape Cod to be knocked down a bit following this last storm). These storms actually use the ocean for an energy source, so when it strengthens, the water temperature goes down. Moreover, when they churn the seas, a phenomenon known as 'upwelling' occurs, whereby colder water from below is forced to mix with the warmer water above to result in a cooler average temperature. The point of this map however, is to demonstrate the anomalously greater availability of Atlantic Ocean storm energy.
Rutgers - October Snow Cover Anomalies
Due to that record-setting snow storm in the Black Hills of the Dakotas, we're running anomalously above normal for snowfall as of October. I think this itself is a little outlying given the lack of snowpack in western Canada and Alaska. Things are looking a lot better on the other side of the Arctic Circle. By the way, our sea ice was incredibly low last year, permitting deep swings of cold air early on in the season. This year featured a strong recovery of sea ice, and also one of the warmer Octobers globally in the Northern Hemisphere.
So let's talk 2013-14 Storm Tracks...
Storm Track #1 - The Colorado Low
The "Colorado Low" has been active from the get-go this early season, with the November 1st and November 17th large-scale storms both of this variety. What essentially happens here is that a low pressure center forms in the vicinity of Colorado, and then rapidly strengthens as it heads northeast through the Great Lakes. For our area, we can get a somewhat complicated picture of its effects, but often it has that same risk of a rain-only soaker with the risk of the thunderstorms. Following the passage of the cold front, we would typically enter the potential for lake-effect snow. This is mainly for the WV mountains, but everyone would be in the running for at least some, especially when the wind flow would bring Lake Michigan into the fold.
Storm Track #2 - The Coastal Nor'easter
This year has been quiet for such storm systems, but it's always a potential for our area. Most of the blockbuster snowstorms we've seen have been of this variety. The Carolina coastline will be the best spot to see the start of the "Bombing out" of the cyclone (rapid intensification). Areas farthest west would have to depend on the most westward storm tracks to get good precipitation and avoid the mountain "shadow" effect. Speaking of the mountains, they would clean-up in these storm events, like they did in 1993 and 1996. Again, a change in the weather pattern and ocean temperature anomalies would have to occur before this kind of option becomes more likely.
Storm Track #3 - The "Clipper" to Coastal
The "Alberta Clipper" is a storm type that can (and does) happen in any winter, whereby a quick moving modest area of low pressure drops in and cuts across the Great Lakes before heading up into Canada/northern New England. Initially, these are primarily rain-makers for our area, with the possibility of giving us a few flakes on the back end. That changes deeper into winter, and the "Clipper" system is often good enough to close school a time or two. The best regime for active clipper systems would be closer to La Nina, but in neutral conditions these start showing up more. The reason why I added the "to Coastal" to the name of this track, is that the bigger Clippers may not stay as a clipper system the whole way through. Ocean temperature anomalies would encourage coastal redevelopment from New Jersey northward. This system storm track is retained from last year also given our current weak La Nina / ENSO Neutral position.
In truth, I'm sure there will be others, and obviously "weather" in general is known to throw curveballs in winter, but I did want to give you my "Top 3" to watch for as we go into this winter season. The Colorado Low weather pattern has already been pretty active, and the Alberta Clippers look favorable to get cranking as well. The southern-track coastal bombs I'm more holding out for the second-half of the season, but we'll just have to see.
As with the other posts on this subject, feel free to ask any questions or make any comments in the discussion section below. I will be happy to get to as many as I can. Finally, remember our Winter Weather Forecast special airs on Thanksgiving Day, on WSAZ Newschannel 3 :-)