Monday, December 1, 2008

"Wicked Ridge of the West"

After a big start we finished Nov. with 81% of normal precip and 2.5 degrees above normal. That is the first time since 2002 that we had over 50% of normal precip in Nov. We had 3 inches of snow in town. The only time we ever had more than a foot of snow in the past 10 years is Nov. 2003 when we got 14 inches, which all fell on the first day of the month. We have averaged about 1.4 degrees above normal for Nov. over the past 10 years. These figures are kept for the town of Truckee.

We normally don’t get cold and snowy till the Boreal Winter season kicks in the third week of December. Last year I had run figures that showed over the past 10 years in each month Dec-Feb we have averaged a few degrees below normal.

I had a conversation with one of the meteorologists with the National Weather Service this week about the upcoming winter and our prospects for getting out of what he even referred to as “The Wicked Ridge of the West from Hell”. Let me quote his response to me. “What I will be monitoring is for convection to initially intensify across S. Africa then shift into the SW and central Indian Ocean during the next few weeks. Tropical forcing then may become focussed ~80-120E as part of a quasi-stationary state. I think one of the better possible scenarios for the west coast is continued retrogression (as a response) such that cold troughs may then dig to your west by mid-late December.”

I will get into details about the next 10 days of weather at the bottom but to save you time a quick summary, Sunny with Big Inversions.

I want to focus on the middle of December forward. There is a lot of discussion going on about the retrogression of the ridge going into the middle of the month. The tropical forcing as per above should cause the ridge to retrograde out to about 140 longitude by the middle of next week. 150 is the magical spot for storms. 140 will allow the cold being seen by most of the country to be able to start spilling back into the West. The coldest airmass so far this season is set to pour into the middle of the country the middle of next week. If this retrogression pans out hopefully we can get our hands on some of that.

What could follow for the second half of December is summed up well in this paraphrase from Ed Berry’s atmospheric discussion from Saturday. “By the latter half of December suggests a continued westward shift of the ridge perhaps to 150W and troughs initially impacting the USA West Coast. The latter should bring welcome precipitation to hopefully most of the West Coast (be patient out there – good things come to people who wait!). What is unclear is what’s in store for JFM; however, a rendition of what was observed during the winter of 2007-08 with added subtropical westerly wind flow may be an option.” That would mean last years non-stop snow Jan-March on steroids. This option has been in the cards for a couple of months already.

The next ten days will feature a storm brushing us to the north and cooling us by ten degrees as compared to today, for the rest of the week. Temps will be cold in the valleys but strong inversions will form. High pressure takes back over for the weekend which should warm us a few degrees. It gets a lot more interesting there after. Keep praying, I’ll be the first to let you know about cold and snow. I do see storms on the models for the week of the 14th, but that is to be thrown in the trash right now as the models are not to be completely trusted until we get into true winter. BA


WeeDiddy said...

Just found your blog today. Nice work. Thanks for decrypting all that. I heard the Ed Berry forecast before but couldn't understand what the heck he meant by all that.

BA said...

It is not easy to understand. You have to take the stuff you don't understand and look up what it means or how it works and then keep reading. Or just skip to the end of his blogs where he summarizes.