COLUMN: Weather Wise with Gordon Currie

There has been a decline in the frequency of thunderstorms in our weather. (S)
There has been a decline in the frequency of thunderstorms in our weather. (S)

Gordon asks: where have all the thunderstorms gone?

If it sinks from the north

It will double its wrath.

If it sinks from the south

It will open its mouth.

If it sinks from the west

It is never at rest,

If it sinks from the east

It will leave us in peace.

This piece of ancient thunderstorm weather lore prompts some thought provoking theories by meteorologists at the end of this year’s summer, concerning the apparent decline in the frequency of thunder in our summer weather which has been noted over the past few years.

There seems to be no deep-rooted scientific reason for this, other than to 
accept the fact that the general pattern of our summer recently 
has not produced the requisite circumstances for classical thundery situations that we recollect many years ago.

This may sound slightly paradoxical, knowing that the past six years have produced high summer rainfalls and excessively unsettled conditions. In spite of this, research and general records have shown less frequency of thunderstorms.

We may pose the question: what sort of storms seem to be missing in recent years?

The classical situations which produce the most fierce and long lasting storms of high summer involve periods of very weak pressure systems with very warm, continental airstreams, capable of transporting medium and high level storms from France, northwards across the country.

The memorable events of July 9, 1984 were a replica if this typical situation as thunderstorms moved northwards from France, and became aggravated by the up-thrust of the North Yorkshire Moors, resulting in a bolt of lightning setting parts of York Minster on fire.

This marked the end of a particularly thundery phase of summers (with the exception of 1983) in the first half of the 1980s.

The summer seasons which are characterised by long periods of relatively cooler conditions with stronger westerly winds tend to create greater mobility of the atmospheric circulation, much less opportunity for the air to become stagnant and over-heated, are usually far less thundery.

Further back in time, the notorious summers of the 1960s were noted for very severe storms with damaging hailstones in three successive summers, 1964, ‘65 and 
‘66.

On the other side of the coin, the most stabilised, anticyclonic summers embrace our greatest heatwaves of the past, and they dispel the 
mistaken idea held by many people that the hottest 
summers are the most thundery.

The record-breaking heat of August 1990 ended almost rainlessly, without thunder, and just a gentle slide 
into cooler, westerly conditions.

The most prolonged thunderstorm on my records occurred on September 2nd-3rd 1961. It lasted for seventeen and a half hours.

This was a medium level storm, with the cloud layers above 8,000ft, filled with forked lightning which branched from cloud to cloud, instead of cloud to ground.

My particularly eerie experience of this storm came with early morning duty of gathering the milking herd from the fields at 4.30am.

Momentarily the moon came out between a cloud chink. For a few seconds, this thin slip of a crescent threw a mysterious sheen of orange light across a landscape full of electrical tension.

A few strands of lifted fog drifted quickly across its face, while all around lay the jagged, coppery borderline of what appeared to be a tormented thundercloud.

Alas, this celestial cloud rockery, festooned with fleshes and hammered with thunder, showed no signs of relenting, and bore down with even greater violence as dawn approached.

PROSPECTS FOR THE WEEK AHEAD

The low pressure system which developed over the continent and moved into the North Sea last weekend, completely upset the influence of the high pressure system to the north of the UK However, by the end of the current week, the offending low will have moved very slowly northwards, and is expected to be replaced by the influence of a much larger depression over the Atlantic, positioned to the west of Ireland. This will eventually introduce south-westerly winds, with brighter conditions. By this time, with rising pressure over southern Europe, there is just the possibility that southerly winds will begin to feed much warmer air into England, - but that is certainly a bit speculative at the time of writing!

Rather unsettled generally with some spells of rain or showers moving across from the west. Mist and fog on some nights, but some good sunny interludes during the week. Day temperatures seasonal normal, 55 F. (13 C.) possibly exceeding 61 F. (16 C.) on some days. Cool nights, but frost risks low.