It was prudent on my part to offer cautious reasoning on the conflicting guidance on a substantial cold outbreak for this week back on 1/9. Some models were too hasty in bringing the brunt of cold air up in Canada southward into the Lakes. I summed up the blog with the following statement:
While colder weather should arrive after our "January Thaw" don't break out the extreme cold gear just yet! This is something to watch for the next week or so, to see if the models change their consensus thinking and surge colder air into our neck of the woods!
It was a potent January thaw followed by colder, more seasonal temperatures that arrived for this week. For the near term; look for near seasonal temperatures for the rest of this week (1/14-19) with normal variability but briefly colder weather about Thursday. That being said; the coldest of air that remains locked-up in Canada now looks like it will finally get a more southward push late next weekend (1/19-20) on the heels of an Alberta Clipper/Saskatchewan Screamer type of storm. More on that bugger later this week!
_____________________________________________________________________
1/9/2013
Over the past several years, meteorologists have studied the weather and climate high over the Polar Region. It's been noted when a sudden, sharp warming occurred high up in the stratosphere over the Polar region, it foretold of a change in the subsequent weather at the lower levels of the atmosphere... a sharp, notable COLD change to those areas affected.
A fascinating paper appeared in the Quarterly Journal of the Royal Meteorological Society entitled The association between stratospheric weak polar vortex events and cold air outbreaks in the Northern Hemisphere by Erik W Kolstad, Tarjei Breiteig and Adam A. Scaife. Basically 51 winters were researched to discover the relationship between the sudden stratospheric warming and subsequent cold outbreaks. Over eastern North America it was found it occurred about 50% or more of the time at peak phase.
This phenomenon, sudden stratospheric warming /SSW/ has occurred in the Arctic region during the past week or so (see chart below as of 1/7/12). The stratosphere is located roughly between 6 miles and 30 miles above the ground. After this occurs, many times in the past it forced cold air to build in the lower layers of the atmosphere. After the pooling of the frigin air (yes I know it says frigin rather than frigid - a mistake I chose to keep - a little levity there ;-) generally 10 to 14 days later, the cold air drives south but where it will go presents bigger problems. The exact location(s) of this cold or Arctic outbreak depends largely on the upper air jet stream at the time and other influences. Stratospheric warming events do lead to temperature drops in the Arctic, they don't necessarily have to have a core effect on the Great Lakes and Southeast Lower Michigan. Again, note the big warming on the chart!
Therefore; this is definitely an initial alert for the possibility of much colder temperatures in the offing BUT more must follow. Another tool that I've posted many times in previous articles/papers at the NWS and now here in my blog, is the projection of the Arctic and North Atlantic Oscillations.
More often than not; when the Arctic Oscillation and larger encompassing North Atlantic Oscillation show a decline (or become negative) in the forecast, colder air is likely to invade the U.S. So step two, is to examine that data.
The projected AO and NAO is extremely erratic in the next 7-14 days. More so in the latest runs so NO assurance the coldest of air will be delivered here. While both show a general trend down or negative; the NAO has a few members that are completely opposite while the projection of the AO is extremely unstable! One of the widest ranges I've observed over the years, ranging from a +3 to a -6!
Taking a jaunt over the our friendly experimental NAO/AO projection page of Kyle MacRitchie at Albany (mentioned in earlier blog) for more clarification pretty much tells the same story.
While again, the NAO is projected to go negative, the extent of that negativity becomes more questionable because of the ensemble variance. Likewise and to a larger extent, so does the AO projection, below. Note as you get further out into February; it is very variable with the negative outlook. Why does it become less variable way out? I would imagine because the model has returned more to climate averages and thus; projects near average in March and early April. In any event in the near term; the NAO/AO are at odds as to the extent or magnitude of the trough expected to develop over eastern Canada and the States.
Another ensemble to take a gander at is the NCEP ENSEMBLE GFS 500H mean which shows the animated projected 500 MB flow for the next 360 hours over North America. Important; note the link I posted here started from Jan 9th's data and subsequent runs after are likely to vary as updated. To account for that, I also posted some of the maps in the Jan 9th time lapse.
So; Does what happens in Canada, stay in Canada?
As you can see; it is very cold up in eastern and central Canada but the brunt of the cold at the 500 MB (Jet Stream) level, stays mainly up in Canada on this run. Ok, most of the data I've presented has been of GFS origin; what about the latest European?
At 120 hr, they look pretty similar:
At the 192H below; the Euro shows extreme low or cold heights up over James Bay but note the "bowling ball" is fairly contained (meaning the coldest of air stays up in Canada).
At the 240H; the Euro moves the "ball" east and it moderates significantly!
While colder weather should arrive after our "January Thaw" don't break out the extreme cold gear just yet! This is something to watch for the next week or so, to see if the models change their consensus thinking and surge colder air into our neck of the woods!
| Making weather fun while we all learn, Bill Deedler -SEMI_WeatherHistorian |
No comments:
Post a Comment