“Polar Vortex” warning

Winter Update

There are a few weather events that tend to be over-hyped and mostly misunderstood.  El Nino, Monsoon Season, and the dreaded “Polar Vortex” to name just a couple. A few years back the media loved to do stories about the Polar Vortex, to the extent that it became synonymous with cold and people would use the two terms interchangeably. Sometimes it was cold but if it was really cold it was the Polar Vortex. Most of the month many weather geeks like myself have been tracking this outbreak. The Polar Vortex is nothing more than a very low-pressure system that sits above the poles (both poles) high in the upper atmosphere. Certain events can trigger the air to be pulled south. It is typically a stratospheric warming event. I am not going to go into a “strat warm” discussion right now but it is nothing unusual they have been happening for millions of years and will continue to happen long after we are dead.

These events usually occur in the upper midwest to the northeast part of our country and Canada. They rarely reach the west but they do modify the air so that technically by the time it reaches us it simply an arctic outbreak. Being in the southwest part of the state it is even rarer for the modified air to reach us, it is more common in the northern half of the state and east of the divide. It is common in Wyoming and Montana.

So cold air is coming to much of the United States and it is too early to determine how much of impact it will have on our weather because we don’t know how far west and south (deep) the air mass will settle in.  This is important because it changes the storm path. Usually, when this happens a ridge goes up in the west based on how far west the cold air and low pressure settle in. The storms will either ride up over the ridge and down into the trough (cold air and low pressure) within the arctic airmass missing us. Or if they are very strong storm they could just slam into us and provide moisture to fuel a big storm. It is all determined by the strength(height) and positioning of the ridge. Typically it is more common for the first scenario to happen. But nothing has been typical in the last three weeks.

This outbreak has been expected for a long time and it has taken longer to get here than the long term forecasters expected. Relying on the ones I follow the most, I have been expecting a cold winter above average snowfall winter for our area since I wrote about it in September and October. I may have to adjust the average up to above average given the last three weeks. But two of the years I compared this season to were 2009-2010 and 1977-1978 which were substantially above average winters.

The Euro model has historically been the most accurate global model in the world. All of the models are constantly backtested and results determine the rating,  both independently and by the governments who own and operate them.

Twice a week the Euro has a very long term run which uses 51 ensemble model members to predict 46 days into the future. This is different than the daily ensemble run, they refer to these as the “Euro Weeklies”

Here the temperatures relative to normal through yesterday for North America

ncep_cfsr_noram_t2m_anom

Here are what the temperatures look like compared to the average over the next 46 days for the US. These are in Celsius. Between now and March 3rd.

eps_t2m_1104h_conus_185

This does not mean every day will be colder, there will be some warmer than average days, some average days and colder than average days. The time period as whole ends up below average.

Monday/Tuesday next snow?

Great question, this coming storm has never looked like a good set up for us. It has been more for the northern and central mountains and to a certain extent Telluride. The models have been trending lower on the storm for everywhere, to the extent that it is questionable that areas in or near town will get anything.

The whole thing I have been leading up to is that we are going to be in a very uncertain pattern for a few or several days largely dependent on the arctic air masses.  So my “Polar Vortex” warning simply means that, uncertain times ahead.

Stay tuned.

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