Glasgow, Paris, Brussels, Amsterdam see 1st snow but why no North Atlantic/Greenland block? Blame the MJO!

Written by on January 22, 2019 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Many parts of Scotland including myself woke this morning to the first blanket of snow ahead of potentially the coldest night of winter tonight. However, many may be asking, what happened to the ‘beast from the east’ or Greenland block? After all our weather continues to come in from the west.

Instead of this…

Credit: wxcharts.eu

Credit: wxcharts.eu

We’ve got this…

Credit: wxcharts.eu

Credit: wxcharts.eu

With the aid of an Atlantic flow streaming into the cold pool over Europe, many across Scotland, parts of England, Wales, Northern Ireland, France, Belgium and Netherlands are witnessing their first snow. But it’s from a northwest flow not from the continent or north as expected…

Glasgow

Oldham

Amsterdam

Brussels

Paris

The GFS shows the expansion of snow cover, particularly from central France up to the Netherlands by tonight.

Credit: wxcharts.eu

Tomorrow AM

Credit: wxcharts.eu

Milder air moves in Thursday-Friday but shall be followed by more polar maritime winds blowing from the northwest by the weekend.

Why no block?

It seemed everything was coming together just beautifully for a classic blocked up, prolonged cold pattern for both eastern North America and Western Europe.

It would appear the MJO or Maddan Julian Oscillation could be to blame on the pattern refusing the block up and shut off the Atlantic. The MJO is currently in phase 4 as seen from the below chart.

As you can see from the below chart put together by Marco Petagna that phase 4 in January favours a positive NAO. The reason for the chill in a seemingly mild pattern is the negative AO and entrained cold flow coming off Canada and Greenland but this air mass is tempered by the Atlantic.

With the above in mind and looking at the current storm exiting North America, a split has occurred in the Atlantic jet stream forcing a flatter amplification downstream into Europe.

Credit: Tropical Tidbits

On a positive note, all may not be lost. It looks like (according to models!!) the MJO will progress into phases 5, 6 and 7 and this does favour a -NAO and colder pattern. Recall the model suggestions of very cold weather by month’s end and beginning February? This is still on the table and modelling may have seen the MJO progression into more favourable phases.

Notice by the 31st in the below chart, the GFS has another storm exiting North America but this time the jet stream remains intact as it bulges north forcing steep height rises out ahead. It does eventually split but with the presence of a stronger ridge which extends further north, deepening the trough over Western Europe.

Credit: Tropical Tidbits

This would either force a direct north or if the blocking progresses north and east into Iceland, a northeast or easterly to develop.

Notice the position of the bulge more into Iceland. This shows winds over the UK turning northeast or east.

Credit: Tropical Tidbits

The 500mb anomaly for the same time confirms this.

Credit: Tropical Tidbits

ALL projection and open to shifts and let downs of course but this is merely explaining what’s going on and potential.

IF there’s a long enough lag in downward propagation of the SSWE and we enter more favorable phases of the MJO then I still believe a lot of winter remains ahead of us.

The CFSv2 weeklies show this.

500mb anomaly day 1-7

Credit: Tropical Tidbits

8-14

Credit: Tropical Tidbits

2m temp anomaly Day 1-7

Credit: Tropical Tidbits

8-14

Credit: Tropical Tidbits

However, we’ve been here plenty of times before right and one crucial factor needs to be the MJO progressing into phases 5, 6 and 7. If this were not to happen then we’re likely to see the repeat of models going from block to no block. Let’s wait and see.

FEATURED IMAGE: Hazel Strachan @StrachanHazel

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