Europe January 2019 Outlook

Written by on December 22, 2018 in Rest of Europe, United Kingdom & Ireland with 0 Comments

The month of December has panned out pretty much as expected, predominantly mild, often wet and driven by a mainly +AO/NAO.

In the 30 day animation below, you can see the initial blocking then return to negative heights across much of the arctic (+AO) which has led to mild over the continents but note the build up of pressure at the end of the loop over Scandinavia.

Despite the clear and ongoing stratospheric warming, the models remain uncertain with regards to both the AO and NAO. Both oscillations have been positive then neutral for much of December with polar air locked over the Arctic and east Asia.

The reason for the +AO/NAO can be attributed to the maddan julian oscillation and it’s enhanced phase 3 which throws off large scale thunderstorm activity over the Indian Ocean. This leads to a mild and oceanic driven pattern across much of North America and Europe.

For the month so far it’s been cool over Scandinavia but warm for much of the rest of the continent.

Credit Michael Ventrice

So, what next? I made mention of the Scandinavia ridging at the end of the loop above for a reason. This could be the initial signs to a developing pattern which may turn very cold.

First we need to see the stratospheric warming progress from Asia to North America and most importantly for us, over Greenland.

Below is the 10mb warming crossing the arctic between now and Boxing Day.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

This warming by as much as 70C within just 5 days forces the stratosphere to expand and the troposphere to contract and this process takes a week or so for the 10mb shift to be felt down to 500mb. When the reaction is felt we can expect strong build up of heights over the Arctic.

Another indicator for a colder pattern is the eastward progression of the MJO pulse which has been active, amplified and worth tracking through last summer and indeed now.

Note in the below 3 charts how the convection (greens) shift through Indonesia and over the west Pacific while widespread sinking takes over the Indian Ocean. This indicates the progression through phases 3, 4, 5 towards 6, 7 and 8 which are more favorable for cold at this time of year further north.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

The shift from Indian to Pacific Ocean in convection shifts the upper air pattern throughout the hemisphere and often correlates to a colder North America and Europe with the a negative AO/NAO.

In the above loop, height rises late over Scandinavia and appears to be expanding west towards Greenland and could be the initial signs of change, essentially the beginnings of a developing cold pattern.

A 3rd positive sign in recent weeks has been the flip in SSTA’s surrounding southern Greenland.

Dec 22

Credit: Tropical Tidbits

Nov 1

Credit: Tropical Tidbits

This warming looks healthier for the support of a -NAO which pretty much all models are now showing.

Given the ongoing stratospheric warming event, warming SSTA’s surrounding Greenland within a modoki El Nino and low solar, I really like what the CFSv2 is showing in it’s weeklies as we progress through January.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

While the hemispheric 500mb hemispheric pattern looks favorable for an eventual locked in cold pattern on both sides of the Atlantic, particularly from the 2nd week of January onward, the temps aren’t that cold at the surface. The models are far too warm and suggest that they don’t not see much cold air around. This is an increasing problem.

The test will be 1) whether the above with Alaska/Greenland/Arctic blocking materialises and 2) how cold it becomes. Keep in mind that usually the models are slow to the party when there’s an initial SSWE with delayed reaction at 500mb, then another delayed reaction to cooling the air. 3) If/when the cold arrives, how cold are we talking? Modelling has been known to under do the depth of cold within air masses as they go from pole southwards.

Another thing worth noting, the evolution to a true cold pattern can take a couple of weeks to complete. The initial starts over the pole with incredible warming which expands to strat and in turn forces the contraction of the troposphere. Then the cold that was once within the strat needs to descend through our atmosphere (troposphere), this takes 1-2 weeks to complete. The very cold air often arrives initially over eastern Europe and then migrates westwards as the blocking highs shift and eventually lock into position.

So, Christmas looks dry but seasonably cool with frost and fog, perhaps much the same for New Year and into the first 5 days of January but beyond the first week I can see some significant changes to an increasingly cold and snowy pattern for Western Europe. The period to watch in January 10 through 25.

There is of course room for error and significant error IF the blocking doesn’t position themselves in the right places. Take 2011-12, remember how bitter Europe turned but the UK was stuck beneath the block and so the cold never made it across the North Sea. That scenario even if all of the above materialises, cannot be ruled out.

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