Saturday, February 15, 2014

Long Range Discussion: Severe Weather, Snowstorms To Kick Off March

This long range discussion will focus on the expected weather to end February and kick off March.

The image above shows the latest 500mb height anomalies across the Northern Hemisphere on the left, with cloud cover, pressure contours and high/low pressure denotations on the right. If you've been with The Weather Centre for a while, you know how we use a rule created by Joe Renken that states a storm system in East Asia then results in a storm in the United States 6-10 days later. This situation is no different- today, we saw ridging/high pressure emerge in East Asia. If we extrapolate that out 6-10 days, we arrive at a warm-up in the February 20-24 timeframe. I'll discuss this more a little later down this post.

Lately, as the image above shows, the weather pattern has been dominated by west-northwest to northwest flow, thanks to deep troughing in the Gulf of Alaska and suppressed ridging in the Southwest producing a pattern favorable for East Coast snow events. This whole pattern is expected to flip in the medium range.

The changes begin as ensemble members foresee strong ridging shifting east into far eastern Russia, which will then shift the Gulf of Alaska storminess to the east, resulting in the loss of high pressure in the Southwest US. That Southwest ridging then propagates east into the contiguous United States, producing mainly zonal flow, which keeps anomalous warm or cold outbreaks out of the picture. However, with the ridging now gone, the storminess in the Gulf of Alaska can drop south into the Western US. The result is a stormy West US, and a very warm East US.

Model guidance (with the exception of the CMC model on the far right) is in agreement on a pattern change evolving, where we see the troughing drop south into the West US, as high pressure prevails yet again in the Gulf of Alaska. The storminess in the West US isn't as well defined on the ECMWF forecast (left) or GFS forecast (center), primarily because this image shows projected 500mb anomalies over the 8-10 day forecast period. This means the forecasts may seem a little less 'intense' than they end up being, because the anomalies are averaged out over a 2 day period, rather than a 6 hour period like most models print out.

Regardless, the pattern will involve high pressure setting up along the East Coast in response to troughing out West, and this sort of pattern just screams for not only a snow event, but a severe weather event. We will see anomalously warm and humid conditions present across the Central and Eastern US as the jet stream bends north to accommodate for the ridging out East. This ridge also tells me we should keep an eye out for a storm system cutting north through the western Great Lakes, something model guidance is already picking up on. I have a feeling such a storm cutting north would result in not only a northern Plains snowstorm, but also a severe weather event for the Central US, something I discussed in yesterday's post.

As we head into the last days of February, ensembles give the Central and East US another shot of cold weather, as shown by the GFS Ensembles' portrayal of the trough at the 500mb level on the left panel. Again, the pattern we discussed above would strongly support this solution. It wouldn't surprise me to see additional chances for storms, both snowy and severe, before the month of February ends, apart from that other storm system we discussed yesterday in the link above.

For the opening days of March, I wouldn't be surprised to see us start on a chilly note before rebounding to rather seasonal temperatures. Depending on how the sudden stratospheric warming event continues to evolve, we could be looking at a cool March, though the chance of that would be maximized in the north-central US (primarily the Plains), and minimized along the East Coast and West Coast, where ridging and warm weather would be expected.

Andrew

14 comments:

Anonymous said...

Once again, Andrew, many thanks for this masterful analysis and presentation. And with each post, we get another opportunity to understand a wee bit better what will be happening and why. :)

Anonymous said...

Ok, everyone be very careful what you say and do. I was busy feeling felief that we in Illinois were finally finished with the snow and the East could have it, when WHAM, we're supposed to get 5-6 inches on Monday.
Ah, karma

Anonymous said...

How many times do i have to tell you that you are stuck in the winter mood. Its time for you to make a spring forecast and not already looking toward next winter. I'm sick and tired of you talking about winter and I'm ready to leave this blog for good. I have been looking at this blog for years and have liked all the posts until you started loving winter so much. I liked all the mixed posts about all subjects and now every post is about some sort of winter type thing. Don't tell me that its still the same cause its not. I'm very disappointed in my favorite weather blog. :(

Anonymous said...

anonymous at Feb 16 2:04 Why do you think that he would be talking about other seasons while we are in winter right now? Once spring comes he will talk about weather in the spring and the same for other seasons, and also we have been in the mist of insane weather patterns and life threating storms for weeks now so don't expect him to talk bout stuff that is still months away.

Anonymous said...

Yeah, why would you start talking about next winter before even talking about Spring? That isn't very professional. I too, like your blog, but lets get real here. Spring 2014 comes way sooner than Winter of 2014-2015. Make a Spring outlook, please. NWS releases there's very soon.

Anonymous said...

You realize that this blog's preoccupation with winter is because it's (a) still actually winter, and (b) been an unusually harsh winter for 2/3 of the country, right?

Anonymous said...

Do you live in the Chicago area. I f you do then you should go to Tom Skilling's Severe Weather and Tornado Seminar on April 5 at the Fermilab in Aurora,IL. It is a great presentation.

Anonymous said...

I so get its still winter & I so understand the continues posting about it, I really do..BUT..if you do not give us a glimpse of a warmer forecast in our hour of need then you have no heart!
Spring please!! I also really do appreciate you keeping us in the know on the coming winter storms also,I really do!! But can you not throw in a shimmer of glee for us and let us know when it may be turning around? Spring!
Thank you so much, I'm not meaning to get crazy on you, but my Prozac is almost gone!
bree

Anonymous said...

I'm anonymous at 2:04 , responding to anonymous at 5:44. Spring is not months away in fact. It Is only 1 month away and I think he should forecast about stuff that is close rather than 1 year out. Plus it is getting warmer this coming week and we are starting to slowly crawl out of winter. By the way I don't think they are life threatening. The Chicago blizzard was life threatening with 20 inches of snow, thundersnow, wind gusts to 85mph and insane drifting and blowing. That will go down in the record books. Not these storms. So publish a comment actually correct and don't make a fool out of yourself next time.

Anonymous said...

Have you seen that extended forecast by the spc. It goes so far north. What do you think about that storm system?

Anonymous said...

The problem is how Anonymous @2:04 made his comment. "How many times do i have to tell you . . ." Sounds like some creepy controlling stalker. It's a weather blog. The owner talks about weather. The weather, right now, is predominantly wintry. Get over it!

Anonymous said...

anonymous at 11:29 this is anonymous at 5:44 we are not crawling out of winter actually. Even though we will get a warm up it will be brief and the noaa issued its 8-14 day forecast recently and it shows that the east will see well below average temps and some long range models are shows a possible coastal storm in late Feb, early March esp since we will be seeing a +pna during that time and also the farmers almanac which in my opinion has been very accurate this year shows more frigid weather for mid march, or at least for the northeast area so we are not crawling out of winter.Plus he always issues a winter forecast for the next winter a year away around this time so that should not be old since you say that you have followed this website for a while.

Anonymous said...

I had to post to say I just received a call from my husband who asked: "what's Andrew saying about the Blizzard Iowa has been issued for February 20th?"
See.. this just goes to show you Andrew is the main conversation here in our household!! When Andrew does post we pay attention!
Keep up the good work Andrew! Even though I ask for a Spring forecast (so want that bad now) please do not let me stop you from posting what's heading our way now!! Not that I could stop you, you know what I mean!!
bree

Bobber said...

I wonder if you have an opinion on something a bit more localized. Might you have information on fronts moving through Northern California near Burney during the first half of March? Bob is my name and fishing is my game.