Europe October 2021 Outlook

Written by on October 1, 2021 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Through September 20th, the month has been incredibly warm and largely settled. Note in the below chart the stark west to east contrast though with a very chill NE Europe/NW Asia extending west into Scandinavia.

Credit: Michael Ventrice

For parts of Russia, Baltics and Finland, this may go down as one of the coolest September’s while it’s Britain’s 2nd warmest!

As you can see below, meteorological summer (JJA) has been dominated by above normal heights with one core on the north shore of the UK, the other over far east Europe.

Mean sea level pressure June-August 2021

Credit: ECMWF

September 2021 has literally been a continuation of summer with highly unusual persistence in ‘summer-like temperatures’. In fact the month has ‘averaged’ warmer than a typical July and August for the UK.

After a distinctly summer-like month, we end on a very different note and much more like the time of year. The transitions has been late but quickly arrived in the end.

The beginning of last week saw the remnants of tropical storm Odette sweep across Iceland bringing significant impacts.

Odette’s remnants remained in the form of a very deep low as it tracked up the eastern side of Greenland driving heat into the Arctic. Winds along the front gusted 60+ mph over the Outer Hebrides.

The transfer of heat into the Arctic forced heights to build over the high latitudes forcing the development of a -AO/NAO. This then forced the Atlantic storm track further south and essentially made for the eventual arrival of autumn.

Ahead of the true arrival if autumn and ahead of the strongest cold front since at least May saw an unusually strong late September heat surge which drove temperatures to 23C along the Moray coast and Tain bringing July-like warmth at a time 14-15C would be considered normal.

Credit: Meteoceil

The presence of the sultry subtropical air was courtesy of abundant sunshine and strong south winds.

The front separated July-like air to early October and the change came in a matter of 2-3 hours. The following day was more like what it should be for the closing days of September.

Credit: Meteoceil

Once the front swept through, we were left with a legacy of blustery showers and seasonable temps.

We’re now firmly under the influence of an active Atlantic jet stream which a series of lows and associated fronts piling in on a near daily basis.

The Atlantic low pressure pattern looks set to persist for the UK and Ireland through the first half of October.

Here’s the GFS ensemble 5-day mean 500mb height anomaly.

Day 1-5

Credit: Tropical Tidbits

Day 6-10

Credit: Tropical Tidbits

The ensemble is hinting at higher pressure building mid month which could attempt at edging north.

Credit: Tropical Tidbits

With the involvement of the tropics, we could see enhancement of both highs and lows.

With Hurricane Sam expected to take an eventual northward track over the Western Atlantic and makes contact with the mid latitudes uncertainly grows for the outcome over the UK. Some modelling indicates, ridging over France building north where as others suggest the remnants of Sam passes close to UK shores bringing further spells of wind and rain later next week. Depends upon several factors and when the time comes that Sam’s tropical energy meets the westerlies, the pattern remains highly uncertain beyond mid next week.

What is pretty clear is that October opening week to 10 day period looks unsettled with a potential spell of relatively stormy weather this weekend as a deepening low crosses the UK but beyond this, it’s tough to say and whether a spell of drier and more settled conditions holds.

Here’s the CFSv2 for October 2021.

500mb height anomaly

Credit: Tropical Tidbits

CFSv2 calls for a wetter than normal month for the west, drier east.

Precipitation anomaly

Credit: Tropical Tidbits

The CFSv2 suggests a warmer than normal month for much of the UK, Ireland and continent.

2m temperature anomaly

Credit: Tropical Tidbits

My hunch is that the unsettled remains for most of the month with brief (2-4 day) spells of drier and brighter. Temps should average near normal but with wind, rain and cloud, night temps may hold and tip the balance to a warmer than normal month, especially given any air coming from the west or south is warmer than average over the Atlantic.

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