Meteorology Section Report: 2008-09

By Philip Eden

Both the electronic and traditional instruments at the Society's weather station have continued to function satisfactorily during the last twelve months and there have been no faults or breakages during that period. As a result, the logging of data every five minutes has continued without a break, not just for the last year, but since December 2002. The monthly summaries previously required by the Meteorological Office have been superseded by a more flexible approach to the submission of data, and I know send the data online each day for most of the time, and in bulk at the end of any period when I have been away.

A request to replace the manual rain-gauge, which is in a state of moderate disrepair, was declined by the Met Office as their budget wouldn't allow for it. However, we are due one of our three-yearly inspections later this summer (funnily enough three years after the last one) and I shall make the plea again.

Monthly reviews of Hampstead's weather have been posted on my website, and linked to from the Society's website, by the 4th of the following month, and the summaries extend back to the mid-1950s. The intention remains to extend the data online further and further back when time permits.

The Society has continued to supply data to Haycock Associates, a firm of civil engineers, who have established a web-based system for collecting and displaying environmental data in respect of the Hampstead ponds for the City of London corporation, and we have now received annual payments sufficient to cover the costs of servicing the automatic weather station.

Let me now summarise the weather we've experienced during the last year.

SUMMER 2008 was second successive poor summer with an excess of rain, a shortage of sunshine; daytime temperatures were slightly below the long-term mean but nights were often rather warm, so that mean temperatures for the quarter were close to the average. In marked contrast to 2007 when the wettest weather occurred in June and July, those two months in 2008 were actually pretty average. It was August 2008 that took the biscuit. Rainfall was 60% above normal, while the month's sunshine aggregate was barely half the normal amount. The sun shone for a mere 97 hours, an average of little more than three hours per day, and during 2008 only January, November and December brought less sunshine. The real statistical contrast was with February which had delivered 135 hours of sunshine in spite of a considerably shorter length of daylight as well as two fewer days.

AUTUMN 2008 began where August left off, and the first twelve days of September brought more heavy rain and a continued marked shortage of sunshine. But from the 13th onwards the weather changed, and the remainder of September, and also the bulk of October were characterised by spells of warm sunshine. October, though, had a sting in its tail: on the evening of the 28th snow fell heavily for three hours, leaving 5cm on the ground. This was Hampstead's first October snowfall since 1974, and was arguably the most widespread and heaviest such fall in October in southern England since 1880.

WINTER 2008-09 was rather drier and sunnier than average with near-normal temperature. There were cold spells early and late in December, in early-January, and in early-February, which were balanced by lengthy mild periods in mid-December, mid to late-January and the second half of February. The most interesting feature of the winter was the heavy fall of snow on 2nd February when the maximum snow depth was 16cm. This was certainly our heaviest snowfall since 1991, when the snow depth at Hampstead Observatory reached 27cm.

SPRING 2009 was warmer, drier and sunnier than average. It was not uniformly so, however, and there were occasional interruptions of cool, blustery and showery weather. But the warmer periods were sufficiently dominant that the spring quarter ended up the fourth warmest in our 99-year history. It also ranked 10th driest, and 7th sunniest.

Philip Eden 24 June 2009


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