Sunday, December 28, 2008

Let's Talk...........

Let's talk about the long range pattern as today marks the end of week 1 of official winter. Still have 11 weeks to go. Dare I say the Wicked Ridge of the West may ride again over the next few weeks. This will be my detailed discussion of what is ahead for us and then I will tweak if anything changes this week, plus my december recap on temps will be on Thursday.

I always like to start with all the positives first. So far this season, basically in the past two weeks, we have gotten about 13 feet unofficially up on the Western Crest here in Tahoe. Interesting to note that we are already ahead of yearly snowfall for 1881 in which the whole year there was 12 feet. We are just shy of 1977 which had 15 feet and 1924 which had 16, and winter is only 1 week old. (Just an aside for those of you keeping track of Global temperature data. The average global temperature fell .75 degrees last year and .25 this year, which has erased any of the warming of the 20th Century.) Of course we are a far cry from 1938 & 53 which saw nearly 70 feet, almost double the average. Those are the years they use for pictures to make you think it snows a lot less now, which it doesn't.

I am noticing a pattern here with 1996. That year was very dry like this year up until mid December. Then it dumped till about Christmas, and rained, which we narrowly avoided last week. Then it stopped again. By mid January Northstar had laid off 20% of its employees. Then it starting snowing and didn't stop. 1996 ended up being the biggest snow year in the past 25 years with 50 feet of snow! Not saying we will have the biggest snow year in 25 years, but we should be getting back into lots of snow by the second half of January.

Watching the models you can clearly see that after a possible short lived cold front next weekend and a little snow (and I emphasize little), a huge trough digs into the Eastern half of the country. Most of the time if you want to know what are weather will be just look at the East and we will have the opposite. That will be the case the first half of January as the negative NAO sets up its blocking pattern and has storms going up the East Coast and driving cold down into the middle and Eastern half of the country. In reading the discussion of long range forecasters they actually seem to agree that this will be an extreme but short lived event. That is good for us because when the East gets warm we are usually cold and snowy.

Let me paraphrase a quote from long range forecaster Joe Bastardi in his blog today. Keep in mind that by "Nation" he means the Heartland to the East, so we are looking for them to have the opposite of what we want, Cold and Snow. "I wish to stress that the kind of pattern coming will bring the coldest 10 day period for the nation between the 5th and 25th, something we have not seen in many years in January, but it will flip and the warming that comes after this period will mean the worst of winter is over for the nation. It is my firm belief that this will evolve into a much warmer pattern after around Jan. 20." What that would mean for us is that when the Heartland and East is getting severe cold the first half of January caused by the negative NAO and AO, there will be a ridge over the West Coast with mild air and no storms. When the pattern reverses around the 15-20 of Jan. the door should re-open to allow troughs with cold air and storms to return.

That is just one of the factors leading to our warm up and shutdown of the storm door, but it's a good one. The PNA, which I have many times explained is how amplified up and down the jetstream over the Pacific Ocean is, will be going Positive(way up and down). This will help to pump a ridge over use for a couple of weeks and a trough into the East. Good news is that Ed Berry agrees that this pattern is short lived. Once we can get the NOA to reverse over the East Coast and allow the cold to come back over the West, the PNA should go Negative and we should be in business.

Let me just paraphrase a quote from Ed Berry's latest blog this weekend. "JFM I think some rendition of a superposition of tropical and extratropical circulation(rainfall) for phases 3-4 of both the MJO and GWO are a possibility. That suggests a continued loose preference for a central Pacific Ocean ridge-West and Central North American trough. There will be some variations, case in point the west coast ridge/eastern states trough predicted by many week-2 models is not unrealistic (a feedback in this case)." So as you can see he thinks things are still set up for a favorable position of tropical activity to feed our storms and possibly the MJO becoming a factor in increasing that feed, which is what triggered almost all of our big storm outbreaks last season. He thinks that the West Coast ridge and East Coast Trough is a temporary feedback issue in the pattern.

So we will have to watch and look for the sign of the change back to stormy for the second half of the month. Hopefully we can squeeze out some snow from next weekends cold front before our 2 week Wicked Ridge. I'll keep you posted.

No changes to this weeks weather with lots of clouds and some sun from the 3 big storms pounding the Pacific Northwest. Temps in the 40's and lows in the 20's with inversions setting up. Cold front should come thru Friday night with colder weather and some snow showers for the weekend. BA

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