Confidence Growing In Cold Solution For January-February

(Post made on January 10, 2013) Confidence is indeed growing in the possibility of a cold end of winter, starting with the impending polar vortex collapse. Let's see what will get the ball rolling here:

Today's ECMWF model shows the polar vortex being escorted out of the Arctic by a massive high pressure system building over Greenland in a negative North Atlantic Oscillation (NAO) scenario. The vortex appears to be squeezing southeast amidst high pressure in the Arctic and in the West US-Rockies. Recent model runs have shown it bombing out directly over Nova Scotia, Canada, in a situation that could bring insane cold and snow to that region. We want to analyze the situation a little further than just the polar vortex, however. Going back to the negative NAO, it looks to have the highest point of high pressure in the center of Greenland towards the west of that land mass, meaning it could be neutral to slightly west-based. Such a placement of the high pressure would put the most cold and snow over the Northeast US by the polar vortex sliding into the region (more on the cold than the snow).

Moving ahead to Hour 240 of the ECMWF model run, we see that the main part of the polar vortex has gone over New England, over Nova Scotia and is now south of Greenland. However, another piece of energy that appears to be related to the polar vortex is present in southern Canada, with below normal height anomalies stretching from that area all the way to the Plains. These below-normal height anomalies signify the potential cold weather that would then intrude upon the Plains, Midwest and east Rocky Mountains. It would be mostly centered in the northern Plains. Note that the negative NAO now has the ridge centered west of Greenland, inducing west-based negative NAO conditions that would enhance potential for cold and storms in that region. High pressure stretching across the Northeast Pacific and West Coast suggests a positive Pacific-North American index (PNA) phase, something that enhances cold weather potential for the Plains and Midwest into the Ohio Valley.

I want to take a moment now and talk about the stratosphere and how the models have been having trouble with the incoming cold pattern. The models already have many issues forecasting here at the troposphere, and thus are bound to have many more problems forecasting conditions tens of thousands of feet up in the air. The ECMWF has been consistent with the polar vortex being pushed out of its Arctic domain and high pressure building over the same area. This would lead to cold air being forced south. Additionally, incoming sudden stratospheric warmings appear in the cards, meaning the cold weather would only be reinforced.

But the big thing i'm really excited about is the already-proven Siberian correlation with North American temperatures. There is a theory that snow cover anomalies in October can form a correlation with the Arctic Oscillation in the following winter. In October 2012, we saw below normal snow cover for the first half of October, hence the warm temperatures in December and mild start to January. However, the middle of October (and especially end of October) brings about neutral to much above normal snow cover, meaning conditions would turn favorable for cold to anomalously cold conditions for late January into February, coinciding with these sudden stratospheric warmings and polar vortex collapse. Since this theory has already been working well this winter, I see no reason to stop believing it now.

Andrew

Notice - January 9, 2013

Hello, everyone-

I have been a thorough and dedicated weather blog for the past few years, and have managed to keep a good balance of my life and this blog. However, there is business that requires my complete and undivided attention for a while.

That said, I will not be posting anything from January 10 - January 12, 2013. I will resume posting January 13, 2013.

Andrew

Third Stratospheric Warming In Sight; Fourth Warming Incoming?

The long range GFS model has consistently been putting a third sudden stratospheric warming in the forecast, with the upper stratosphere forecast to experience unusually warm temperature anomalies over Canada and the New England area.

The presence of a third sudden stratospheric warming after a significant warming that ended several days ago and an incredible ongoing SSW (link) would surely penetrate the inner core of the polar vortex, pushing it further and further to the breaking point, a.k.a. collapse. I have been heralding such a collapse for weeks now, and I am not backing down with its potential. While the collapse may be pushed back a bit, I am confident that a collapse (the Arctic Circle is no longer dominated by the polar vortex) is imminent in at least some parts of the stratosphere.

Let's turn our attention to the next potential Fourth SSW. This one has me very excited, because it could feature a prolonged warming event, which would only further enhance the vortex's collapse, possibly into oblivion if we're lucky, keyword "if".

This is a forecast image of the Madden-Julian Oscillation, composed of several forecast models and ensembles. The Madden-Julian Oscillation, known as the MJO, involves placement of wind anomalies and convection from the Indian Ocean, across the Pacific and into the Caribbean. Phase 1 starts in the Atlantic and Indian oceans, and transitions east from the Indian Ocean from Phases 1 to 8, as seen in the image on the left. I am in to finding correlations between certain indices, and this is no exception. Upon some hard research, I found data suggesting that a sudden stratospheric warming can be predicted days- even weeks- in advance just by using the MJO. Here's a quick rundown of MJO phase to possible SSW in days:

Phases 2, 3: 25-36 Days
Phases 4, 6, 7: 13-24 Days
Phase 7, 8: 12 Days

So, if we use that MJO forecast graphic, we see the models going from Phase 5 to Phase 7, which is roughly a 13-24 day lag time from MJO phase to SSW. But here's the catch: the models start to circle in Phases 6 to 7, meaning the convection in the image on the left stays in the areas just east (and inside) of Micronesia. What this ALSO means is the potential for a prolonged stratospheric warming event starting in the next 13-24 days and continuing for as many days as the MJO can stay in the designated Phases.

This is all very exciting, but a major caveat is that the MJO does not necessarily always provoke sudden stratospheric warmings- it helps them along, so to speak. In this environment, an SSW would be easy to establish.

Andrew

Snow Prospects Dim For Next Several Days

The prospects for accumulating snow over much of the nation are unusually low for the next several days, and there is one big factor causing this: the Negative PNA.

The image above depicts the typical atmospheric set-up in a negative Pacific North American (PNA) phase. We see high pressure build in the Gulf of Alaska, causing a depression of pressure to form in the Rockies. This then brings cold air to the region, as well as the North Plains. However, high pressure then forms in the Southeast and East Coast due to the presence of low pressure in the West. This high pressure redirects the storm track to favor precipitation along the Gulf Coast or in the Northern Plains. We already saw this pattern earlier this winter, and now it's returning.

This 500 millibar height anomaly forecast for the next 6 to 10 days clearly shows a defined negative PNA pattern, with high pressure in the Gulf of Alaska, low pressure in the Rockies and high pressure in the Southeast. However, because the high pressure in the Gulf of Alaska is so unusually strong, the low pressure in the Rockies also strengthens and expands, meaning the cold would then push into much of the Plains and parts of the Midwest (i.e. Iowa, Missouri). The storm track would then also push east, meaning any storms that took the southern route would affect the Midwest and Ohio Valley. But Mother Nature prefers to leave the United States snowless, as model forecasts have the North Plains storm track on overdrive and the Gulf Coast/Ohio Valley storm track running on empty.

There is some hope, though:

This is the Day 10 forecast from the ECMWF model's ensembles, commonly called the EPS. The EPS shows the majority of the polar vortex collapsing into the Northeast in a fashion that would inspire frigid temperatures and a very windy period in the entire East US. A negative North Atlantic Oscillation (NAO) is present with high pressure over Greenland, and a positive PNA appears with high pressure on the West Coast. I'm not too keen on buying into this idea at the moment, as other forecasts have the PNA in negative territory for a while to come.

Please do not ask if your area will receive snow, this is a general overview, not a precise snowfall timing forecast.

Andrew

Announcements for January 9, 2013

Announcements:

The reason I have not been posting about the snow is because of the scope of the warming stratosphere and it's forthcoming implications, there's just no winter storms to track. I'll bring up the snow topic on a post later today.