Tuesday, January 27, 2009

Too Cold to Snow!.....

The first half of January we had a negative NAO & positive PNA pattern. The negative NAO causes a block to form over Greenland which forces storms up the East Coast. Once into Canada the storms help to drive frigid air from the Arctic down the Eastern half of the country. This forms a huge trough of cold air that can’t progress off the coast because of the block over Greenland. There is also a huge polar vortex this year, which is the mass of growing frigid air in the arctic. This will only help to make the cold air stronger.

Meanwhile the colder than normal water in the Pacific (La Nina) causes high pressures to form in the Eastern Pacific all winter, one after the next. This causes storms to be bumped north, which is why in La Nina years the Pac NW is usually above normal for precip. and the Southwest is below. As storms get stronger Jan-Mar they have better luck pushing the high pressures out of the way. With the block in place over Greenland and the trough stuck over the East, it causes the high pressures to get stuck over the West. Adding to the problem can be a positive PNA which causes larger high pressures over the Central & Eastern Pacific. This sends the storms north towards Alaska which limits their ability to squash the high pressures or sneak over them.

Good news is that the PNA is forecast to trend negative most of February. The bad news in the short term is that the NAO is forecast to go negative as well. There is a currently a train of huge storms lined up across the Pacific headed towards the West Coast. These storms will slam into the high and try to move it. Last week the high wasn’t expected to be as strong and the block wasn’t forecast to be in place, so the storm coming for Friday looked to just roll right into us. With the strong high being locked in place by the trough to the East, the storm will get demolished and whatever is left will just bring some cooler air.

The block over the East looks to finally move by the middle of next week. A storm on Wed. will push the ridge East but may also split and lose some energy as it hits the back of the strong high. Another Storm for the first weekend of Feb. looks to have better success but a high building back over the Eastern Pacific could keep the heaviest moisture to the north. One thing that may help the storms to be stronger and more effective is the possibility of an MJO circulation moving into the Western Pacific. This adds lots of fuel to the jetstream.

The flow of storms should be consistent without any blocks from next week and beyond. The only problems will be the constant re-emerging of a high in the Eastern Pacific taking the punch out of storms and trying to bump them North. La Nina was not forecast to be this strong the beginning of the season which is why season projections were so favorable. In La Nina our season can go either way since we are between the Northwest and Southwest. We need neutral conditions. Good news is that the ocean temps warmed a little in the past week.

The models aren’t very accurate more than a week out. That is why I wanted to do a post describing what patterns are happening globally. Things should get stormier for us in the next couple of weeks so continue to monitor the patterns and don’t get stuck on the dismal model forecasts for now. I am going to wait and post again when the models finally catch on to the pattern change and possible MJO influence for next week. Meanwhile, get out and enjoy the fresh snow and sunny skies! BA

7 comments:

Anonymous said...

Hi again. Love your blog..very helpful and obviously studied. What is the outlook for Northstar 2/7-2/14? Our family vaca is that week. Thanks much and keep up the good work.

Anonymous said...

Nice write up...I' coming up the 6th, 7th and 8th of Feb. Do you think there will be some storms during that time?

BA said...

I was very elusive on this post. Reason being that the models show storms next week and into the weekend, but they aren't as strong as I think they can be and some models have them going north of us. I want to wait a few days to see if some of the patterns cause the models to change their tunes by this weekend. Sit tight.

Chris Stobing said...

I have moved to Tahoe from almost 250 miles away for the first time in my life, sacrificing my summer vacation at school for snowboarding. Your blog is one of the only things giving me hope in the idea that I had the right idea. I know you cant change the weather but you certainly soften the blow, keep it up man, you give me reason to come back next year and do it all over again.

Rob Green said...

First off, love your blog. The crazy amount of detail you give in your posts really helps in understanding what factors are important in bringing snow to the mountain.

You said that the ridge is going to push the storms north for the next week or so. How far north do you see them going, and will they lose a lot of energy and/or moisture as they go up? I'm heading to Whistler on the 7th and right now the snow there is hard pack bordering on ice. The official forecast has snow off and on for the next week but I was wondering if you see anything bigger in your models. Thanks.

-Rob

questforpizza said...

Thanks for the detailed post! I enjoy reading your blog.

BA said...

The West Coast of Canada should continue to get dumped on the next two weeks.