Early sharp frost,but no record

The air temperature here fell to minus 2.7 Celsius last night.This was the lowest temperature in October since 28th October 2003 when a similar value was recorded. No monthly record was broken but the lowest temperatures have usually been logged during the last week of the month, and only on the 19th October 1926 has there been such a cold night in this area so early in the autumn during the last 110 years. At that time this area was given over to farmland!

The lowest temperatures measured in south London occurred relatively recently in October 1997. After a very dry September, some heavy rain occurred between 6th and 14th October and this took the monthly total above average. However, after mid month, rainfall totalled less than 2mm with sunshine helping to dry out the ground. The drying process accelerated during the last week as high pressure became established, the air descended and from the 28th until the end of the month the low-level inversion dissipated and all cloud, apart from some cirrus on the 30th, disappeared.

Very low humidities, light winds and dry soils combined to produce the perfect recipe for frost. Nature didn't disappoint with record-breaking low night-time temperatures on both the 28th/29th and 29th/30th. Wallington and Twickenham both recorded minus 5.2 Celsius on the 28th/29th, and here in Morden, after a minimum of minus 4.7 Celsius on the 28th/29th, the following night had a low of minus 5.0 Celsius. Perhaps more remarkable were the grass minima. Values of minus 13.2 and minus 12.8 over the 2 nights remain the lowest 2 consecutive grass minimum temperatures of ANY month since records began here in 1988. By the way, the grass minimum temperature last night was only minus 4.9 Celsius.

Today marks the 15th consecutive day without measurable rain (defined as 'no daily rainfall equal to, or exceeding, 0.2mm/0.01 ins.'). Up until the 1980s this 15-day period was known as a 'drought'. However, the rise of the mocking tabloid press, the general decline in exactitudes, and comparisons with life-threatening water shortages in the Third World quite correctly brought about the abandonment of the term 'drought' by all but a few diehards.

Nevertheless, it's interesting to examine these lengthy dry spells. The previous one occurred here from the 16th September to 2nd October 2009 (a total of 17 days), but lack of rain is generally less common during the Autumn and Winter months. A good Summer often produces a prolonged period of dry weather. In 1959 this area had 37 consecutive dry days (15th August to 20 September) and in 1976 parts of southwest England had no measurable rain for 45 days. Perhaps surprisingly there was no 15-day dry spell in 2003, but the rainfall deficit for the period February to October in that year was well over 50%.

The Spring months seem to have the most frequent dry spells. In recent years there have been several in mid Spring. In 1995 there were 19 dry days (29th March-16th April), in 1997 it was dry from the 25th March to 17th April (24 days). A total of 27 dry days occurred between 21st March and 16th April 2002, and in 2007 there was dry weather between 31st March and 22nd April (23 days).

Is there any way of connecting dry Aprils to the following Summer? Fortunately the answer is no. In 1912, parts of London had no measurable rain during April and the following Summer was one of the coldest and wettest on record! By the way, the previous 4 mid Spring dry spells were equally divided between good Summers and decidedly indifferent ones.

So how bad has the winter been?

Days are still chilly, and there was even a flurry of snow early this afternoon. However, the push from winter to spring is well under way.

For statistical purposes, winter covers the 3 calendar months of December, January and February. In this area, December was the 29th coldest since 1900, but in recent years the Decembers of 2002, 1997 and 1996 were colder. January was slightly more interesting. It rated as the 12th coldest since 1900, with colder Januaries occurring back in 1987, 1985 and 1979.

A third consecutive winter month with temperatures significantly below average is quite rare. The last occasion this occurred was during the memorable winter of 1962/3. In more recent years, the winter of 1984/5 was the 10th coldest since 1900 despite a relatively mild December. Similarly, December 1978 was not cold overall, and the winter of 1978/9 was only rated 7th coldest.

Although this current February is only ranked 50th coldest at the moment, it does look as if this figure will rise towards the top 20 over the next few days. However, the trend to milder weather later in the month is apparent from some forecast charts. If, therefore, the mean temperature at the end of the month is similar to the current value (4.9 Celsius), This February will have been the coldest since 1996 and the winter will have been the coldest since 1990/1. However, if this February is cold enough to rise to 20th, it will have been the coldest February since 1991, the 9th coldest winter since 1900, and making it the coldest winter since Jim Callaghan's 'Winter of Discontent'......1978/9.

We await with interest!

The end of the dry spell

After 17 days without measurable rain, the 0.2 millimetres that fell yesterday evening was enough to break the dry spell. Most years have a prolonged dry spell (15 days or longer) with Spring and Autumn months most likely to see one. September and the beginning of October have had 3 dry spells in recent years. 1997, 2002 and 2007 each had between 15 and 17 consecutive dry days, and back in 1969 only 3 millimetres of rain fell throughout September. The most prolonged autumn dry spell in the London area occurred from the 14th September to 9th October 1921 (26 days). However, there were several lengthy dry periods that began in August, notably 23rd August to 28th September 1929, and 15th August to 20th September 1959, both 37 days. In the extended good summer of 1959 there was a further 17 days of dry weather from the 23rd September until 9th October.

Not a vintage August.....but

In recent weeks there have been less grumblings about the poor summer. In fact, in the London area August has been a month of consistently warm weather. The temperature has reached, or exceeded, 20 Celsius on every afternoon since 20th July, a total of 30 days! If maxima reach 20 Celsius on each of the next 9 days, then this August will be record-breaking. Even in the hot Augusts of 1995 and 2003 there were days when the temperature failed to reach 20 Celsius, and further back the August of 1976 had some cool days during the last week. It remains to be seen if this month produces a record, but in this so-called poor summer there have been 72 days (including April and May) with highs of 20 or more. In the memorable summer of 2003 there were 117 warm days, including 22 maxima above 20 Celsius during September.

A barbecue summer

As the baying pack from the media continue to taunt the rather disingenuous attempt by the Met. Office to tell us it almost is a 'barbecue summer', let's find a few facts ........at least for this part of the country where 15 million potential barbecuers live.

There is a reason why barbecues are more common in Mediterranean countries and the USA than here. They have warm and dry summers, and we don't. Up until the mid 70s plastic macs donned for a trip to the pub were more common than plastic plates and cups on the patio, but then the summer of '76 arrived. The general public realized that the sky didn't leak every day, and suddenly al fresco hit London. The barbecue grills rusted for a while in the late 70s and 80s, but from the end of the decade onwards a barbecue grill became a 'must have' along with the 4-wheel drive and a mobile phone. In many years the weather co-operated, but in this summer, like in its two predecessors, plastic mac days returned.

The official statistics put an emphasis on the mean temperature and the total rainfall, but if the nights are cloudy and windy they're often milder than after warm and sunny days. Perhaps more relevant are 'days' with rain falling and daily maximum temperatures, and these paint a poorer picture of the summer weather so far this year.

May, perhaps perceived as a tad early for a trip outside, did produce a few reasonable days during the last week, and June was a pleasant month in London. However, using maximum temperatures, it ranked cooler than the recent Junes of '76 , '89, '92, '96, '03, '04 and '06. Although rainfall totals were below average, the number of days when rain was recorded was above normal

For many people in Southeast England July was a poor month. After the 2nd, winds were from the southwest on nearly every day. The breezes were brisk at times and on the south coast they were often fresh or strong. The temperature has failed to rise above 21 Celsius since 3rd July on the Sussex coast, and although it has been somewhat warmer at times inland, in south London there have only been 4 cooler Julys (based on maximum temperatures) in the last 20 years! The other interesting statistic is with regard to rainfall. Okay, it was a wet month around London, but not exceptionally so. However, measurable rain fell on 20 days.....4 more than the previous July record during 20 years of observations, and what's more 6 of the remaining 11 days had some rain, but not enough to measure.

The Met. Office have 'revised' their forecast for the rest of the summer, but while they keep digging their hole, it remains to be seen if nature has the last laugh and produces a warm and dry August.

The Summer when the grass turned brown.

For many parts of southern England June looks like being the 4th consecutive month with below average rainfall, but at the moment the fields and gardens are as green as in the Emerald Isle. Not so in June 1976. March and April were both very dry in that year, with monthly rainfall totals in southwest London below 10 millimetres. May was slightly wetter, but still with a total rainfall more than 50% below average. It was a sunny Spring, but May was actually cooler than this May (2009). June 1976 began fairly cool and changeable. The temperature on the 1st only reached 19 Celsius and nearly 2 millimetres of rain fell overnight. The following 2 days were even cooler with highs of only 16 Celsius, but then pressure rose and so did the temperatures. The maximum on the 9th reached 30 Celsius, and although temperatures then fell closer to average, it remained largely dry with sunny spells. During the third week it was rather cool and changeable, and on the 20th nearly 7 millimetres of rain fell, but the last 10 days of the month were dry, hot and sunny. On the 22nd the temperature reached 27 Celsius, but then daily maxima read:- 30,31,33,33,34,33,29 and 29. It came as no surprise that the grass turned brown. It was not even a surprise that pubs around London ran out of beer. The Summer of '76, a record-breaker.