Despite the ‘chilly’ conditions covering much of continental Europe and your typical ‘in between low pressure frosts’ over the UK, there’s consistency in the models for a mild, zonal December pattern not just for Europe but throughout the mid-latitudes of the hemisphere.

The recent southward plunge of arctic air will gradually decay in the coming days as Atlantic air makes steady progress east. The North Atlantic trough reflective of the strong positive NAO/AO essentially cuts off the arctic door to Europe and even the cold dam over east Asia, well it’s got nowhere to go given the ridging over eastern Europe and strong Atlantic-Europe jet stream.

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The polar vortex is strong and positioned within it’s source region (over the pole). Modelling suggests this remains strong through at least the first half of December and therefore low pressure to the north and high pressure to the south supports stronger westerlies across both Pacific and Atlantic, maritime influence is the result on BOTH sides of the Atlantic.

Note the strong polar vortex out 10 days from now.

Despite the warm outlook, snow cover across Eurasia and the northern hemisphere is very extensive and above normal for late November. This ‘above normal’ snow cover has been linked to a -AO winter but as Dr Judah Cohen states in a recent publication, a lot depends on how active the energy transfer is from troposphere to stratosphere in December. Not a strong enough transfer will mean there’s little disruption for the PV and therefore it stays strong.

This years record breaking El Nino may already be having big global influence on the mid and upper atmosphere by releasing a lot more heat north, boosting the mid-latitude region which forces lower heights further north. Essentially holding back cold.

The jet stream is fast flowing not just from North America to Europe but around the hemisphere. A faster west-east jet drives maritime air across the continents and holds back the arctic air from diving south.

GFS ensemble shows the low height field over the high latitudes and positive underneath through December

EPS control shows a mild outlook for Europe into mid December.

2m temp anomalies on the rise through the period.

I urge caution with the above! Remember what was said in both the Winter Forecast and December Outlook. December was likely to be relatively mild and uneventful. The ocean sea surface temperature profile is very different now compared to 1997. The North Atlantic is opposite.

2015

1997

Notice in the animation below how waters are expected to warm around Greenland and north of the UK into the heart of winter. This at least supports blocking highs.

Another positive factor for us winter lovers here is the models show a stronger Aleutian low/trough this season, something not seen during the past 2 winters and this could suggest a weaker Icelandic low/trough and therefore more positive in the place we want it… Greenland/Iceland…

The Met Office model shows just that for the December-February period.

See video for today’s discussion.

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