Sunday, 14 December 2008
Yesterday was the wettest day of the year with 25.4mm (exactly 1 inch) of rain falling in the 'Rain day' that stretches from 09 to 09 GMT. It was not a record breaker, nearly 32mm fell in December 2002 and almost 30mm fell in 1995. Boxing Day 1886 appears to have been the wettest December day, but as some of the totals included melted snow a cynic may question the validity of the readings. The numbers for that day included 46mm for Kensington and Brixton and 60mm for Hampstead. In recent years, 34mm fell in parts of southwest London during December 1979. Interestingly, the whole rainfall event this December covered 2 'Rain days' and the total came to nearly 36mm. It commenced around 0100 hours on the 13th and then rained continuously until 2300 hours, a total of 22 hours. That in itself is not a record. During June 1903 parts of north London had over 58 hours of continuous rain. By the way, a few days after that rain a three week 'drought' commenced!
Monday, 1 December 2008
Tuesday, 11 November 2008
Yesterday (10th November) nearly 24mm of rain fell. This made it the wettest day of the year so far and the wettest day since November 19th last year. November ranks, on average, as the wettest month of the year in many parts of the country, but in the last 20 years, in this area, October has been a wetter month. A daily rainfall total of 24 mm in November is actually not uncommon here. It has occurred 4 times during the last 20 years, and 3 of those occasions have been during the last 8 years. On each of the last 3 very wet November days, more than 30 mm of rain have fallen. The wettest day was the 5th November 2000 with 33 mm of rain. The wettest day in the area from historic records appears to have been the 25th November 1938 when nearly 42mm of rain was measured.
Saturday, 25 October 2008
Sunday, 12 October 2008
Time to get the potatoes in before Autumn truly arrives. Although temperatures above 20 Celsius in October are not unusual, after the disappointingly cool September in London, this short warm spell is much welcomed. The maximum temperature of 22.2 Celsius today is over 1 degree warmer than any maxima recorded during September, and is the highest this late in October since 2001. There were only 4 days during August that were warmer, 13 days in July and 7 in June. In October 1921, the first 11 days of the month had maximum temperatures above 21 Celsius, and on the 5th and 6th of October in that year the high was close on 29 Celsius at several places in London, including Kensington Palace, Greenwich, Camden Square and St James's Park.
Tuesday, 23 September 2008
Although rain threatens for the next couple of days, it's now 11 days since any measurable rain fell in Morden. With little, if any, rain likely during the last week, it looks as if September is going to be another dry month. That will make 3 out of the last 4 months with below average rainfall; and 6 out of the last 7 months have had temperatures below the 20 year average. The scientific community regularly assure us that the very wet weather (but not everywhere!) is part of global warming, and the El Nino is responsible for the lower temperatures. Of course, the threat of Global Warming cannot be ignored, but perhaps the trend towards sixties fashions has been followed by a return to sixties weather. Let's hope not. Apart from the severe winter of '62/63 most of the weather was instantly forgettable. Some of the fashions and much of the music appear to have lasted in the memory somewhat longer.
Wednesday, 20 August 2008
Thursday, 7 August 2008
To put it simply, there are 3 main types of thunderstorm in this country. The most common of these is the all-year-round storm which starts with a build up of cloud during the morning, a couple of rumbles from a cumulonimbus cloud in the afternoon, followed by a fine evening. In the winter months this type of storm is usually found on windward coasts. The second type is formed by the destabilisation of the air well above the surface, usually 6,000 feet AMSL or higher. This commonly occurs when cool Atlantic air is about to bring an end to a hot spell. In recent years this form of storm has been fairly uncommon, although one occurred here on the 28th July. The first sign of these type of storms is usually several afternoon reports of thunder from Brittany, followed by a quick migration northeastwards, reaching Southampton in the early evening and London bewtween 9 and 10 pm. For the good folk of Kent last night's storms were closest to the second category. Although very little surface wind blew in association with the storms, it was certainly not true that they were slow moving. In fact the storm clouds were moving at around 35 knots. Rather than one storm lasting a long time, it was a series of storms generating within a band that ran from the East Sussex coast towards Essex. Now, the third type of storm is the 'swing-seat' one. This occurs on a warm summer's evening when several storms develop or move into the area, produce a vivid display of lightning, numerous rumbles of thunder, but are never overhead. Thus, it remains dry and warm, and a free display of nature's power can be observed accompanied by a glass of claret and a packet of peanuts. That was the thunderstorm that occurred over this part of South London yesterday evening.
Friday, 25 July 2008
Thursday, 3 July 2008
The first rain of the month has just fallen but there's a long, long way to go before we reach last July's total of 124mm. It was the second wettest July for at least 100 years in South London, with only July 1956 wetter. Perhaps surprisingly, none of the top 10 wettest Julys correlate with the top 10 coolest Julys. During the wet Julys, rain is often of a thundery nature, and although the weather may be cyclonic, there are often spells of warm sunshine between the downpours. However, out of the 9 Julys when 100mm was exceeded, only the Julys of 1925 and 1941 could be described as rather warm. In association with all the wet Julys, the following Augusts were cool, and sometimes very cool. Let's hope it's not another wet July this year.
Friday, 6 June 2008
Wednesday, 28 May 2008
Wednesday, 21 May 2008
Now it's warming up again, the risk of air frost has probably gone until the autumn. The minimum temperature (2.2 Celsius) that occurred the night before last, was the equal lowest during the second half of May in Morden for at least 20 years. A similar minimum occurred on the night of the 28th/29th May 1994. An air frost did occur in a few places on Monday night, with minus 0.3 Celsius recorded at Farnborough (Hants). The cold air originated north of the Arctic Circle, and when it crossed Finland, minima of minus 10 Celsius occurred, resulting in much damage to apple blossom.
Friday, 16 May 2008
Sunday, 11 May 2008
Nearly one third of the month has gone and temperatures are heading towards a new record, but are they? The year 1992 had the warmest May on record in south London, with May 1989 only a fraction of a degree cooler. In May 1992, most of the very warm days occurred during the second half of the month, with several decidedly chilly days during the first fortnight. It is very unlikely that the present warm spell will persist, but a very pleasantly warm May, so far.
Tuesday, 6 May 2008
The temperature exceeded 22 Celsius for the third consecutive day today. The last time this happened was between the 5th and 7th September last year. During May last year there were 4 consecutive days late in the month with highs above 22 Celsius and there were also 3 consecutive days above 22 in April. The longest sequence during the last 20 years of 22+ days (9) in May occurred during 1998, from the 8th to the 16th. After a maximum temperature of 21.4 on the 17th, there were then another 3 consecutive days with highs above 22 Celsius. By way of contrast, in May 1994 the temperature failed to rise above 22 Celsius all month!