Winter Starts Next Week….
On the calendar anyway. Still scouring the long-range models looking for signs of Winter to show up on the weather maps. There are some interesting things starting to take shape in the long-range. First let’s start with this map of the 5 day precip forecast.
It’s sad but you can’t help but laugh. I have been saying that the storms keep circling us with the split flow but a picture is worth a 1000 words. Some times we get 6 weeks of non-stop snow here in Tahoe and other times we get 6 weeks of the worst luck.
The pattern just doesn’t want to let go and with the flow starting to slow around the globe and wavelengths beginning to shorten it looks like the pattern change is going to be delayed another week. The models are showing a more Western track for Thursday’s storm which means we should see some light snowfall but not more than a dusting to a few inches on the mountains.
Next week the Eastern Pacific ridge tries to hold strong and we have no help from the teleconnections. The MJO died right before it made it far enough East to bring the convection into the Western Pacific and a chance at affecting our weather pattern. We still have the Positive PNA pattern in place although it is weaker now.
There will be a storm hitting the Pacific NW the middle of next week as the ridge does pull back West in the Eastern Pacific briefly. But it looks like the ridge will move back in quick enough to keep the storm to our North. The ridge does look like it will become flatter towards the end of next week which will allow a chance for the next storm to come South into CA Christmas weekend.
In yesterday’s post I mentioned the Euro showing ridging building in over Alaska and the Aleutians where the trough has been and the trough shifting into the Gulf of Alaska. That would shift the jetstream coming underneath into Western Canada Southward into the Pacific NW and Northern CA. The long-range GFS showed a similar scenario today. Look as this map for the 29th. This is the pattern we want for a return of big snow.
There has been a lot of buzz this week in the weather blogosphere about a possible stratospheric warming event being underway. The upper levels of the troposphere and lower levels of the stratosphere have begun to warm pretty quickly over the Bering Sea and the forecast models show it shifting Northward towards the pole.
What that does is disrupts the Polar Vortex holding in the Arctic Air around the pole and sending it Southward in pieces. The question is always where does the cold go? It loves to come over land and into the US, a lot of the time into Alaska then the West and eventually the East. This is a slow process so we wouldn’t see the cold come into the country until 3 weeks out in January.
This will also turn the Arctic Oscillation negative like it was much of last Winter. As the cold comes into Alaska and Canada we could see the blocking setup holding the trough in the Northeast Pacific and bringing us a series of storms coming underneath. This may be what the models are starting to see in the long-range at the end of the month with the cold air mass showing up in Alaska.
For now we have another 10 days or more without a big storm. All we can do right now is watch and grasp at straws. Let’s hope Winter is a lot better than the Fall. It won’t have to do much to do that. BA
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