Biggest 'high' for months

Mild spring continues
by Philip Eden

The main feature of last week's weather was the steady, long-lasting increase in barometric pressure. At midday on Monday the 18th in London it stood at 989 millibars but by midday Saturday the reading was 1034 millibars.

Such a prolonged rise in pressure is quite unusual and marked a major change in the weather pattern over western Europe and the north Atlantic. During the first half of last week a very moist southwesterly airflow brought copious amounts of rain especially to southwest England; at Bastreet on Bodmin Moor the rainfall between March 10 and 20 totalled 104mm of which 33mm fell on Sunday night 17th/18th, and there was almost as much in other parts of Cornwall and Devon. By Thursday the 21st high pressure was gradually gaining control, much of the country became dry with intermittent sunshine, and it was a very warm day in m any southern and central districts. The temperature approached 17C in places as far apart as Torquay and Chester on Thursday afternoon, and similar readings were reported on Friday afternoon along the coasts of Sussex and Hampshire and also in inner London.

There is an old saying, well known to mariners, which runs:

Long foretold, long last;
Short notice, soon past.

It is different from run-of-the-mill weather lore because it was devised, not by 'anon', but by Admiral Robert FitzRoy. He was famous for captaining HMS Beagle around the coastline of South America with Charles Darwin on board, and he subsequently became the first superintendent of the Meteorological Department of the Board of Trade - the embryonic Met Office - in the 1850s. FitzRoy's rhyme relates to changes indicated by the barometer, and it is surprisingly accurate for such a simple statement. Thus a prolonged rise in barometric pressure is likely to be followed by a lengthy period with high pressure in charge.

This certainly appears to be the case this time, the output of the Met Office's very expensive computers confirming FitzRoy's rather cheaper one-liner. High pressure is expected to persist throughout the present week before declining over the Easter weekend. Although nights continue to be frosty in many parts of the UK, afternoon temperatures are above the seasonal norm, though not by much. For the record Britain's highest March temperature was 25C in Norfolk on March 29, 1968.