SSWE has occurred, we now await split & downward response, CFSv2 sluggish with -AO/NAO through Jan 25

The sudden stratospheric warming has now crucially progressed across the pole and headed towards the Davis Straits as we entered 2019.

Credit: Michael Ventrice

A split in the vortex is expected over the next day or so.

Now we all know that there’s a delay or lag between the initial SSWE at 10mb and by the time the reaction descends into the troposphere and raises pressure over the high latitudes from 500mb down.

However, the models aren’t showing a particularly cold pattern and in fact suggesting the opposite pressure pattern to what you’d expect. The newest run of the CFSv2 (below) shows a colder, blocky pattern towards the end of the month. These ‘all over the place’ model solutions can be expected and remember that I don’t see the big shift until the 2nd week of January but the models are sluggish.

So, why am I pushing the cold so much now compared to back in November when at one point the models showed a nice cold pattern? The difference is clear. Back in November, there was nothing large scale to support a cold pattern and indeed that turned out true whereas now, all the main players you look towards are coming together with strat warming and MJO within a modoki El Nino/low solar year and at the coldest time of the year.

The timing looks good between the peaking of the SSWE and the MJO entering cold phases.

Which is favorable for blocking and UK cold too.

There’s still a lot of warm air across the hemisphere and especially over the continents with mild Pacific and Atlantic air flooding the land masses. So, the models only see the warmth right now. The last few runs of the CFSv2 weeklies have flipped positive from negative at 500mb throughout the arctic. Complete opposite of what you’d expect with what’s happening right now.

The big test comes over the next 2 weeks. Of course we need the strat warming to couple and as it does, I’d expect initial height falls as the cold drains into the lower atmosphere but then a steep and large scale height rise which pushes the fresh load of polar air southwards. The much anticipated vortex split takes one piece into North America and the other into east Europe while heights build over Greenland.

The last strong SSWE’s which occurred in late December were in 1965, 1984, 1993 according to Joe Bastardi of Weatherbell. All these produced strong arctic outbreaks into the US he states and we can recall January 1985 right?

The big error in all this which could make for a big bust in this years forecast would be if the blocking high didn’t park over Greenland but nearer to the UK which stopped the easterly flow from making it to the UK.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Tags: , , , ,

Follow us

Connect with Mark Vogan on social media to get notified about new posts and for the latest weather updates.

Subscribe via RSS Feed Connect on YouTube

Leave a Reply