March heatwave was a record breaker
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MARCH 2012 was Wick and district’s warmest since reliable records began in 1914.
The month, with an impressive average temperature of 7.97C (46.35F), seized this meteorological trophy from March 1938. The a corresponding mean temperature for that year was 7.65C (45.77F).
March 1961 was also outstandingly mild. The mean temperature for March of that year was 7.05C (44.69F).
The theme of the town’s weather was overwhelmingly anticyclonic. Certainly the most compelling evidence of the profound "blocking" influence exerted by a powerful area of high pressure being situated close to and at times over the UK for much of March was the exceptional dryness. The high pressure either effectively fended off the rain-bearing Atlantic frontal systems or weakened those that did manage to impinge and then move across the British Isles. March 2012 was the second driest since 1914. March 1973 retained the laurels for being the town’s driest but only just.
By the last week of the month the centre of a "ballooning" Azores anticyclone had migrated northeastwards from the Bay of Biscay to the southern North Sea where crucially it became stationary and strengthened.
The result was a relatively short-lived but unprecedented spell of summer warmth that broke the town’s long-standing record for highest-ever daytime maximum air temperature on two consecutive days.
Wick’s mean temperature for March was an eyebrow-raising 7.97C (46.35F). This is far removed from the established long-term temperature during March, 4.5C (40.1F).
The town’s average daytime air maximum was 11.05C (51.89F), representing a very substantial anomaly of plus 4.05C from the established March norm. The corresponding average daytime maximum for March 1938 – Wick’s second driest March on record since 1914 – was 10.95C (51.71F). Scrutiny of the statistics for daily maxima for March 2012 show a seasonally mild 10C (50F) was reached or exceeded on a dazzling 22 days.
Perhaps the most sensational meteorological event so far this year was the very memorable heat wave. Between the 25th and 27th Wick – in common with the whole of the Far North – basked in summer-like weather. In Wick the temperatures realised were without parallel for March and would certainly have been considered very agreeable in July.
Wickers witnessed the town’s record for the highest daytime temperature for March broken on two consecutive days. Dense fog that had engulfed the town during the night of the 24th/25th had dissipated by morning.
On the Sunday afternoon the temperature soared to 19C (66.2F) in a gentle southerly breeze and unbroken, albeit hazy, sunshine.
Similar conditions on the 26th hoisted the mercury even higher with a spectacular peak reading of 19.9C (67.8F) attained shortly after 2.30pm. The maximum on the 26th was an incredible 13C higher than Wick’s average daytime maximum for March.
The readings on the 25th and 26th easily usurped the town’s previous highest maximum of 17.3C (63.2F) – recorded on March 9, 1961. The 27th was also ridiculously warm with a maximum of 19.1C (66.4F) noted.
The maximum of 19.9C in Wick on the 26th was higher than in Gibraltar and Istanbul. Tripoli and Tunis were also cooler. The conditions were the consequence of a large and powerful anticyclone that had formed over the subtropical North Atlantic that subsequently migrated northeastwards from the Azores.
Crucially, as it did so, it also started to import increasing amounts of air from over the hinterland of North Africa. The extraordinary weather experienced in the Far North from the 25th to 27th was effectively guaranteed when this high became stationary over the southern North Sea.
The corresponding strong subsidence of the upper air over the centre of the high that had originated mostly from the north-western region of the Sahara was then modified to become even warmer and drier by the time it had descended to the ground.
The pronounced temperature inversion (increase in temperature and decrease in its humidity with altitude) created by the steady downward motion of this air warming from regions aloft, coupled with its corresponding gradual outward movement away from the centre of the high, were uniquely combined for delivering the exceptionally high and frequently record-breaking daytime temperatures.
The centre of the anticyclone had retreated to the west of Ireland by the end of the 28th allowing a weak but marked cold front to slip southwards over the Far North. Brisk westerly winds in its wake gusted up to gale-force eight at times and introduced much cooler Atlantic air.
Wick’s lowest daytime maximum temperature of 6.9C (44.4F) was certainly not unreasonable for March.
Wick’s average overnight minimum air temperature was 4.89C (40.80F). The established long-term figure is just 2C (35.6). The highest overnight minimum was 8.3C (46.9F) recorded on the 9th and equalled on the 21st.
There were two air frosts. The lowest overnight air reading was minus 1.9C (28.6F), noted on the18th. A ground frost occurred on 12 dates. The lowest value over the grass was minus 5C (23F).
The rainfall total was 15.8mm or just 28.7 per cent of the long-term average amount for the month. The wettest day was the 6th when 4mm (0.16 of an inch) was measured.
Wickers experienced winds that reached or exceeded gale-force eight (33.9 knots/39 mph) on 12 dates. The windiest day was the 30th when a force-eight west-north-westerly wind gusted up to 53 mph/46.1 knots, severe gale-force nine on the Beaufort scale.
?
The definition of an Indian summer – stated in "Lorry jackknifes at Latheron" in the Caithness Courier on April 4 – was inaccurate.
An Indian summer is a meteorological event exclusively associated with the autumn months of September to November. There is also no prerequisite temperature of 21C or more required to define an Indian summer.
Further, it does not necessarily follow a cold spell but, when it does occur, it can simply be defined as a period of relatively warm weather until the end of November.
