High Pressure Brings Big Temperature Swings To Scottish Highlands

Written by on April 20, 2020 in Rest of Europe, United Kingdom & Ireland with 0 Comments

A persistent high pressure system anchored between Scotland and Scandinavia has led to a complete shutdown of ‘weather’ and produced significant April rainfall deficits from UK through Central Europe as a result. This blocking high has re-routed all weather north into Scandinavia and south into Iberia.

500mb height anomaly for April so far.

Credit: Simon Cardy

Rainfall anomaly mirrors the above well.

Credit: Simon Cardy

On the periphery of the high, it’s been and remains windy from the Central Lowlands of Scotland southward. Here’s it’s coolest in the east, especially down North Sea coasts, warmest the further west you are. However, underneath the high (central and north Highland), with less wind, lowest humidity, and now ‘dry ground’, we’ve seen quite impressive daily temperature swings.

Today’s (Monday) pressure chart.

Credit: Met Office

Why the big swing in temperature under the high?

As you may well be aware, a sunny, windless and dry atmosphere (helped further by dry ground), aids those big thermal swings with strong solar heating by day (August strength) but equally strong radiational cooling by night (nights still long enough).

The month of April in particular is classic for cold, frosty nights but warm to very warm afternoons. The combination of DRY ground/atmosphere and lack of wind is key to maximizing the level of daytime heating and nighttime cooling!

Air heats and cools slower if wet or windy, more so when there’s both.

Credit: North Carolina State University

Aviemore was both coldest and warmest place in the UK on Saturday

Located just west of the Cairngorm Plateau and sheltered on all sides, the village of Aviemore is probably closest to observing a ‘continental climate’. In other words it’s central Highland location and ‘bowl-like’ geography makes it quite the ‘cold nook’ in winter (-26.2C set in 1995) but equally quite the sun trap in summer (31.3C set in 2018).

Physical Location Map of Aviemore
Physical Location Map of Aviemore

At this time of year, beneath stable high pressure it can still receive winter-like nights followed by near summer-like afternoons.

Saturday was a perfect example of this when Aviemore stoll the show as being the UK’s coldest and warmest place. The morning started off at -5.4C but not even 12 hours later topped 16.5C.

The 20+C swing within 12 hours has been just confined to Aviemore. Altnaharra had a bigger swing Sunday with -5.1C to start and ended the afternoon with 17.2C. 22.3C of a difference.

Yesterday morning’s lows

Credit: Meteoceil

Afternoon highs

Credit: Meteoceil

Like Saturday, Scotland was the place to be for cold then warm during Sunday with Aboyne, Aberdeenshire starting off at -6.9C. Kinlochewe, Sutherland ended up at 19.7C. An impressive range of 26.6C.

Today has been a near carbon copy of the past 3 days. 100% sunshine over nearly 100% of mainland Britain!

Credit: NASA

It was yet another cold start.

Credit: Meteoceil

Temperatures by mid afternoon.

Credit: Meteoceil

Notice a more distinct east-west split thanks to a stronger wind blowing off the cold North Sea.

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