There’s been nothing normal about the polar vortex over the past 10 months. After being record strong throughout the past winter, producing the 4th warmest winter for the UK, 6th warmest for the US and warmest on record for Europe as a whole, the final stratospheric warming has now finally unraveled. Perhaps late due to strength and resilience during the winter.
Credit: Weatherbell
The final springtime stratospheric warming typically occurs during the 2nd half of March, early April but it’s taken until the end of April and beginning of May for it to finally breakdown. The final demise of this years ‘polar vortex on steroids’ has led to a split and downward stratospheric to tropospheric coupling. This sends air from the top down.
Here’s the initial 50-hpa temperature profile over the Arctic. Note the warmth!
This warmth has almost completed it’s downward transfer from stratosphere to troposphere and has split the polar vortex thanks to ridging migrating up towards the pole. One piece of the vortex is currently over Hudson Bay and the other near Svalbard.
The North Atlantic Oscillation will follow the Arctic Oscillation by going negative as ridging over the UK migrates NW over Iceland and Greenland.
Ridging over and just east of the British Isles will initially pump warm air north from Africa but that same high will then get pushed N/W this weekend and dramatically flip the temperature pendulum the opposite way.
This could be one of the most dramatic May flips in quite some years coming as we go from 21C in parts of Scotland and 25C for England to highs of 5-10C widely two afternoons later.
As you can see from the below GFS ensemble 850mb temperature anomalies, the UK high slides retrogrades WNW opening the freezer door for BOTH sides of the Atlantic.
Credit: wxcharts.eu
Credit: wxcharts.eu
Credit: wxcharts.eu
Credit: wxcharts.eu
Check out the flip at 850mb.
Credit: wxcharts.eu
Credit: wxcharts.eu
Credit: wxcharts.eu
Here’s the GFS forecasted 2m temperature over Scotland for the same time each afternoon. Note the drop off this weekend.
With relatively light winds, clear sky and dry air, we should see more big diurnal swings from freezing or below to 20C or above AHEAD OF THE POLAR FRONT!
These numbers are likely a touch lower than what they’ll be. I expect 20-22C in spots including Glasgow, Aviemore and Aboyne. NOTE THE DIFFERENCE BETWEEN 3PM FRIDAY AND SATURDAY!
Credit: wxcharts.eu
Credit: wxcharts.eu
Credit: wxcharts.eu
Credit: wxcharts.eu
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