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 (El Nino)||Primary Storm Tracks (Neutral)||Primary Storm Tracks (La Nina)|
(Click on any of the above images for a larger sized pop-up)
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. 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 2012-2013 Season
Looking at this upcoming winter, it has a lot more challenge to it, because as you saw in the previous post in this series, we're entering a more bland neutral ENSO phase, instead of a previously expected El Nino that was being advertised this summer. Also, the current NAO picture is a-w-e-s-o-m-e for snow lovers, and has already resulted in two crazy out-of-season snow events, which is quite rare this far before Thanksgiving. The reason why that is a problem, is that the NAO typically remains in its various phase only for several weeks, and is poised to return to a more positive phase right when ski resorts around the east are chomping at the bit to open early. This is not a knockout blow though, as (a) it hasn't happened yet; and (b) as 'Captain Obvious' would say, "it does snow in winter".
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 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.
Storm Track #1 - The Coastal Nor'easter
We've already seen what can happen in our area when a coastal Nor'easter slides too far east of us (we get completely missed). However, in a situation where a weak El Nino environment is changing toward neutral conditions, the storm tracks start moving northward a little bit, giving us a better shot at a piece of the action. 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. Current ocean temperature anomalies make this storm track one with great blockbuster potential this year (oh, right, we've already been there).
Storm Track #2 - 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. I'm anticipating that anomalously warm water to take the approaching system and redevelop it off the Jersey coastline into a more significant storm. This has more implications for New England, but the idea is that if this happens early enough in the storm's life cycle we could get a better moisture field back across the Appalachians along with cold air advection instead of a more climate-neutral temperature profile.
Storm Track #3 - The Ohio Valley Soaker
With every ebb there's a flow, and with all deep troughs that develop over the eastern seaboard there will undoubtedly come the occasional recoil that puts the upper-air trough out to the west, dragging storms through the Ohio Valley. Now, the reason for the development of low pressure in the Ohio Valley can be many-fold, but the primary result will be rainfall (sorry). There are ways to get snow out of the mix though. The best would be post-frontal Lake Effect snow if a system can carry with it a good fetch of northwest wind after it passes through. A rarer variety would be a farther south storm trajectory (like with what we had in February of 2003), but even this one is challenging to get heavy snow in the lowlands. This highly variable storm track is a manifestation of the more neutral ENSO picture.
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. It certainly is interesting to note that from my first post in this series through to now we've already seen verification on the Nor'easter storm track (and with what a negative NAO can do to amp up any previously mundane weather pattern). Going forward, I don't think we'll have the opportunity to capture another hurricane into a winter storm jet stream. That privilege only comes once every 20 years or so.
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 :-)