More active pattern on the way, but probably not snowier for I-95

[Isotherm]

http://www.lightinthestorm.com/archives/484

Much of this winter we’ve seen a significant lack in major storm systems in the United States. A simple look at the NOAA watch/warning map for the US throughout the past few months reveals that weather events have been MIA in North America. This is largely because intense mid latitude cyclones feed off of baroclinicity and thermal gradients — we have NOT seen that most of the winter. Why? Temperature anomalies in North America tell the story:

Below are the temperature anomalies for January 2012 — if one were to produce a December 2011 or February 2012 map, it would look similar, as the same general temp pattern has prevailed.

Note the large expanse of warmth virtually everywhere – very little in the way of thermal gradients/temp contrasts. As a result, short waves have been relatively weak, and unable to produce much snow in the Great Lakes/Northeast. Furthermore, without strong low pressure systems, cold air cannot pour southeastward, and Lake Effect snow has been absent for the most part b/c of this. No polar outbreaks –> no lake effect snow, and no strong cyclones –> no arctic outbreaks in the Northeast. It’s been a benign, boring, winter from a meteorological stand-point in North America.

Not the case for Asia and Europe – that’s for sure. The AO transition in mid Jan yielded the development of a blocking feature on the Asian side of the north pole, resulting in record breaking cold and snows across Eurasia, down to Rome, Italy. As we move into the future, that pattern is changing, with a rise in AO values into the positive territory, meaning a return to lower than normal heights in the northern latitudes. What it also means is arctic air will FINALLY enter our side of the globe, with Canada becoming drastically chillier over the coming week.

Note below, the 10 day temp anomaly forecast for Canada. A major change from the map posted earlier. Believe it or not – COLDER THAN NORMAL AIR will overspread most of Canada in the week 1 to week 2 period. Unfortunately for the Northeast, a positive AO and NAO also means the Southeast ridge is robust, and one can see by the warmer anomalies in SE Canada, the resistance to this arctic air.

The above image is the 8-10 day ECMWF and GFS model forecast. Notice the strong SE ridge, typical of a La Nina, but also the big time negative height anomalies dominating in Canada, and down into the West/Plains.

The PNA will be transitioning negative over the coming week, another aspect typical for La Ninas. It seems we’re entering a pattern which is more normal for LA NINA event, one which many of us thought would be present the bulk of this winter.

Although we’re going to see temp anomalies reverse drastically in North America, as already mentioned, it’ll be difficult (once again) to get sustained cold into the Northeast. So in a local sense, the pattern for the I-95 BOS-DCA corridor may not change much at all due to the resistance from a strong SE ridge. However, the larger scale North American regime is undergoing that change, which will finally get an intense baroclinic zone going. We’re likely to see numerous, strong low pressure systems propagating SW-NE from the Plains into the Great Lakes/Interior Northeast, which could put down snows in the Plains, Lakes, and maybe interior New England. The inland storm tracks still means no snow for the big cities of the Northeast.

Surface temperature anomalies for Marches which featured a weak La Nina in place look like this — note the similarity to the above forecasts, big cold in Canada, into the West, and across the northern tier of the United States. Ridging in the South/East.

When we examine Marches with a slightly positive or greater AO values, this is what we get:

A similar picture, with cold in the north, warm in the South.

The one wildcard is the MJO — tropical forcing now in favorable phases for cold in Northeast, but since other teleconnectors are unfavorable — positive AO, positive NAO, negative PNA, the arctic air is likely to just “bounce” in and out of the region, if we get any at all. More probably is moderated shots of cold air behind storm systems, nowhere near as cold as what the Mid-west/West may see.

In closing, the pattern for the next few weeks into the month of March:

1.) Major reversal in North American temp anomalies, with arctic air building in Canada, should yield a strengthening baroclinic zone with powerful lows moving SW to NE across the United States, dropping snow in the MID-WEST, LAKES, and INTERIOR NORTHEAST. Lakes effect snow may get initiated as well.

2.) Continued warm pattern for I-95/East Coast due to the SE ridge and other unfavorable teleconnectors. We’ll see more cold shots due to the stronger lows moving to our NW, but the poor tracks means continued no snow.

3.) Early March regime of cold West/northern Plains/Lakes should prevail. Warmth in the southern plains, southeast and Northeast coastal plain.

4.) Nothing can be ruled out in weather, but chances are against a snowstorm in the I-95 corridor the next few weeks. If it does happen, it’ll be a thread the needle situation given there’s no downstream NAO blocking, or strong ridging in the Western US. Not much reason to forecast any change in the terrible snow pattern of winter 2011-2012. Will NYC see a 6″+ snow event this winter? It doesn’t look good for the next few weeks, but on the bright side, some more exciting times ahead in terms of tracking weather. Strong lows means big winds, severe weather in the Southeast US, snows to the NW of the storm systems.

5.) At this juncture, March should come in like a lion in the North and West, and like a lamb along the East coast.

[Brian5671]

Great post. AT this point, I'd be happy to track an inland runner or Lakes cutter-there's just been nothing for the reasons you state-no cold air to run up against and no baroclinic zones

[Isotherm]

Great post. AT this point, I'd be happy to track an inland runner or Lakes cutter-there's just been nothing for the reasons you state-no cold air to run up against and no baroclinic zones

Thanks, I'm looking forward to tracking some impressive winds later this week. The past few months have felt like spring or fall in terms of tracking wx events, in fact most springs and falls are much more interesting than this winter has been. Just an incredible expanse of warmth across the North American continent, preventing any major storm systems from developing.

[Thunderdude]

In the later spring and summer you got thunderstorms to track.

[CooL]

I'm looking forward to tracking some impressive winds later this week.

Euro has another bomb for later this week. Sub 980mb over Massachusetts and gives SE canada a raging blizzard. Very impressive, we should see some heavy winds and squalls

[Isotherm]

Marches in which the PNA was -0.5 SD or less.

Marches in which the NAO was 0.5 SD or greater.

Global teleconnectors plus current guidance and pattern trends are in good consensus on the cold Canada/Pac NW idea, with varying degrees of warmth from the central Plains to the East Coast

[Isotherm]

The pattern continues to look horrible in the medium to long range, a similar pattern sensible wx wise to the past few months, but there are key differences in North America as I noted in the original post and in a post on the main board. Canada is chilling drastically and that will aid in enhancing baroclinicity, thus more intense gradients and storm systems. This is already evidenced by this weekend's wind event, caused in part by a bombing low to < 980mb over Maine. The reason why we don't get much severe weather in the US with blowtorch patterns is the same reason for our lack of strong low pressure systems over the past few months. In order to get active weather, you need a gradient. If it's dominant cold or dominant warm, not much is going to happen.

The only conducive aspect for next week's "event" is the strong confluence across sern canada w/ plenty of surface high pressure. MJO has also been aiding the pattern w/ more favorable phases, although it still probably won't be sufficient for us. I do think this is the type of situation where we'll see slight corrections southward in future model runs concerning the Wed-Thurs storm, but the deepening trough out west and sfc low cutting into the lower lakes, quite frankly, is a bad synoptic set-up for significant snow from NYC southwestward. If I were in Boston right now, I'd be a lot more optimistic, as they can get decent snows even in a +AO/+NAO regime assuming good sfc high providing low level cold air drainage down the coast.

Keep in mind, these comments are mainly directed at the areas where most of us live -- NYC, LI, NE NJ, CNJ, etc. I would not be surprised to see another minor type event for NW NJ and the lower hudson valley (< 5"). I hope we can get some snow around here, but it just doesn't look good through early March. Maybe we can turn things around for mid to late March, though at this point I'm not sure if I even want that. This winter has been a frustrating one for all of us, a major forecasting headache, and I'm glad to see it come to an end on March 1st.

[Isotherm]

Look familiar? The only thing better is the cold across Canada which will give us more interesting weather to track. In a winter sense, the snow will be much closer but still miss us.

[Isotherm]

So far I continue to like the ideas presented in the original post. Interior sections of New England and the Northeast have benefitted from this pattern as anticipated, with most of I-95 left with cold rains.

Going forward, a warmer than normal temp pattern still appears likely, with virtually all teleconnectors lining up for a blowtorch in the Plains/Southern US eastward to the Mid atlantic coast. Early next week looks to be the last "polar" airmass for the forseeable future -- high temps around 40 with lows in the 20s in suburbia for a few days. But consistent w/ this entire winter - that cold shot will be zipping out of here due to the progressive, +NAO based pattern. A neg PNA, pos AO and NAO will dominate the medium range, D 7-15 period, which is when I'd expect the most significant pos temp departures in the Eastern US (March 8th-15). The one important caveat is high pressure positioning, and the potential for marine influnce/BD cold fronts for New England and the coastal Mid atlantic. Need to monitor wind direction closely, b/c a mainly southerly component will prevent readings much higher than 55-60 for coastal areas. For the bulk of the Mid atlantic, inland, should reach the 70s at some point in mid march, with 80s possible in the SE US.

Heading toward mid to late March, there are subtle indications of a PNA rise, but the AO/NAO look to be pretty stable in the positive modality. So I'd expect less dramatic positive departures in the East beyond the 15th, but probably still biased warmer than normal.

[easternsnowman]

So far I continue to like the ideas presented in the original post. Interior sections of New England and the Northeast have benefitted from this pattern as anticipated, with most of I-95 left with cold rains.

Going forward, a warmer than normal temp pattern still appears likely, with virtually all teleconnectors lining up for a blowtorch in the Plains/Southern US eastward to the Mid atlantic coast. Early next week looks to be the last "polar" airmass for the forseeable future -- high temps around 40 with lows in the 20s in suburbia for a few days. But consistent w/ this entire winter - that cold shot will be zipping out of here due to the progressive, +NAO based pattern. A neg PNA, pos AO and NAO will dominate the medium range, D 7-15 period, which is when I'd expect the most significant pos temp departures in the Eastern US (March 8th-15). The one important caveat is high pressure positioning, and the potential for marine influnce/BD cold fronts for New England and the coastal Mid atlantic. Need to monitor wind direction closely, b/c a mainly southerly component will prevent readings much higher than 55-60 for coastal areas. For the bulk of the Mid atlantic, inland, should reach the 70s at some point in mid march, with 80s possible in the SE US.

Heading toward mid to late March, there are subtle indications of a PNA rise, but the AO/NAO look to be pretty stable in the positive modality. So I'd expect less dramatic positive departures in the East beyond the 15th, but probably still biased warmer than normal.

For these times warmer than normal is the new average, it has been too consistent for too long to ignore.