The NAO is returning to neutral later this week and perhaps even positive in days 7-14 but before then, we’re looking at cold followed by an East Coast storm. Any storm is bad news of course so this will be closely monitored and I will keep you updated on potential impacts.
Unfortunately, models suggest this storm to have a sizeable impact to a region which cannot afford to see even a small storm. This will be nothing like Sandy but will need to be followed closely here as ANY sort of storm will cause further problems to a very fragile infrastructure. Lack of protective sand dunes means more damage potential to coast and properties with ocean overwash likely.
Expect strong wind, coastal rains, heavy snows and even a small storm surge with the Wed/Thurs storm. The storm will deepen the trough and so arctic air will get drawn in on the backside. As the low works up the coast, so the rain/snowline may work all the way to the coast. Don’t be surprised to see snow in the big cities.
This snow would come following 1-2 inch rains.
Here’s the ECMWF chart for Friday.
The below chart is for next Sunday. Notice not only the height rises over the Northeast but the warmer air lifting north through the Plains as the next Pacific storm system carves out a trough over the Southwest.
Following the cold shot to start and end this week with highs even in the big cities perhaps struggling to reach 40F next weekend, we could see temperatures between the 10-15th reach the 70s between DC and Boston.
The mid-mouth pattern suggests western troughiness and eastern ridging with storms exiting through the Great Lakes. The coldest departures from normal will be in the west, warmest in the east between Nov 10 through 25. A less amplified period should allow Pacific air to free flow across the Lower 48 but beyond the 15th, troughiness should begin to develop and intensify with increasing cold. I expect this cold and trough to migrate east late month. The NAO should then flip back. The AO likewise should begin to return to negative.
Stubborn NW Flow Shuts Down For UK, Pattern Becomes ‘Progressive’
Here’s the ECMWF chart for today!
Following the lockdown trough and stubborn NW flow, the breaking down of the Greenland block means a much more free flowing west-east pattern and less cold for the UK . Milder air should reach the UK by Wednesday with temperatures managing to get back above 11 or 12C for much of Scotland.
Here’s the ECMWF chart for Wednesday.
Without the blocking high over the North Atlantic and Greenland the jet becomes zonal and freeflowing. With this pattern readjustment, storminess should increase for the UK. The convergence of warm and cold intensifies the Atlantic jet.
The return to a more positive NAO coincides well with the return to a positive AO and this will shrink the coverage of arctic air over both North America and Europe.
With a positive NAO and AO, don’t be fooled. Cold and snow can still impact. As storms depart Canada and make their way across the Atlantic, once they get southeast of Greenland they tap very cold air at the same time their tapping mild air from the subtropics. By the time they reach the UK, their deep storm centres which can bring gales, heavy rains and on their backside, cold and even snow. This is a setup I’ve been saying for the month of November since August.
For those, like myself who love cold and snowy patterns brought by a strongly negative NAO/AO, don’t fret at this return to positive indexes. If we look at the trend throughout this year and what we saw last year, the NAO and AO will flip and this positive phase won’t be long lasting.
This period will reload the arctic reservoir and once the NAO/AO flips, watch out. Cold weather lovers, be patient. This setup over the next 2-3 weeks should support a December cold outbreak!
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