We’re in the transition of patterns at the moment after the storm on Monday. We’ve stopped the Monday storm pattern that we had been in for several weeks, and we’re rather quiet until the middle/end of next week.
There is a lot of inconsistency in that system, which I’ve noted for a couple days in the discussion. A lot of this stems from the speed of the cold air intrusion and how that plays into the track and progression of the developing low — and how its able to evolve (ie, if it just moves up the coast, if it stalls a bit, if there’s a parent low and coastal low…etc). Right now there’s quite a bit of variation. The impulse responsible for driving the cold air in comes onshore in AK Saturday.
Beyond that storm, we’re in the thick of the cooler pattern heading into Days 7-14. The GFS Extended was updating as I began the blog, therefore it’s on the right side for this time period, but the subsequent graphics are switched.
This is certainly a chilly pattern for us. The AO trends negative after December 25 (which makes sense with incoming cold air) and NAO trends neutral through December 31 before shifting negative. The EPO trends negative after Dec 29. These are all cold signals for the northeast.
The stronger the arctic impulse, the less likely we’ll see an active pattern with it, which is also inconsistent in the long range. The PNA stays crosses the neutral line around Jan 5/6, which means if we were to see some coastal systems develop, it would likely be before that time frame.
Days 14-21…There’s now positive anomalies surrounding the arctic circle, which is not surprising given we’re supposed to be cold in this time period. When you hear about the Polar Vortex coming to visit the United States, it’s basically the polar jet breaking down and weakening. It’s the weakening of that jet that allows the intrusion of cold to leave the arctic and come south. Therefore you’d expect the reversal in anomalies. The Great Lakes and mid-section of the country are now out of the warmer pattern at this point as well.
As I’ve said for most of this season, I don’t put a lot of stock into anything over 14 days (and that’s even a stretch lately), but here’s Day 21-28.
For what it’s worth, the Euro and GFS Extended keep the AO/NAO neutral to negative beyond MLK weekend, and the PNA nudges back positive around 1/11.