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Appleton's Eye 
 
 
                      
 
 

Season Dates 

Every year there is considerable discussion and argument concerning the dates of the commencement of the various seasons. In particular the date of the first day of Spring seems to give rise to a number of differing ideas. To the best of my knowledge there are no official and universally recognised dates for the commencement and ending of the various seasons. For official climatological purposes the Met Office splits the year into four seasons, each of three month, with Winter starting on 1st December, Spring on 1st March, and so on. However, this division is an arbitrary one and relates mainly to convenience of handling statistics based on complete months. One of Britain's foremost climatological experts tends to split the year into five seasons which he designates Early Winter - from about 20th November to 19th January, Late Winter and Early Spring - from 20th January to 31st March; Late Spring and Early Summer - from 1st April to mid-June; High Summer - from mid-June to 9th September, and Autumn - from 10th September to 19th November.

There is, of course, considerable confusion concerning the March and September equinoxes (when day and night are approximately equal) which occur around the 21st March and 21st September. In recent years the habit has crept in of describing the March Equinox as the Spring Equinox, and the September Equinox and the Autumnal Equinox. This has led people to believe that the March Equinox marks the first day of Spring and the September Equinox as the first day of Autumn.

There is, in fact, no definite connection between the date of the March Equinox and the commencement of Spring, and it would probably be true to say that in most years the onset of Spring occurs before March 21st. If one reflects on the matter then it is clear that those parts of the northern hemisphere which lie to the south of the British Isles will have an earlier date for the commencement of spring-like conditions than those areas that are to the north. Yet the date of the March Equinox is the same for all areas.

Sometimes the dates of the Winter and Summer solstices, which occur around 21st December and 21st June respectively, are regarded as being seasonal milestones, in that they mark the shortest and longest days and, by inference, mid-Winter and mid-Summer. In terms of actual temperatures the coldest part of Winter occurs well after December 21st i.e., during January and February. In the same way warmest weeks of the summer usually occur after the Summer Solstice, i.e.; during July and early August.

June 24th is known as mid-Summer Day but it simply marks one of the old quarter days on which rents and other payments became due, (other quarter days include, March 25th - Lady Day and September 29th - Michaelmas Day). My personal impression is that the peak of summer usually occurs, very roughly, around mid-July, but a great deal depends on the character of the weather each individual year. The days do of course become shorter after the 21st June but initially it is a slow process and the loss of evening daylight only amounts to about 15 mins by 21st July (the loss of morning daylight during the same period is about 25 mins).

To sum up, that various dates which appear in our diaries and calendars have little or no connection with actual climatological seasons. Even over such a relatively small area as the British Isles there are obviously considerable differences in the dates for the onset of various changes in the general monthly patterns which we describe as the seasons. In a given year Spring-like weather might arrive over Southern England in early March, whereas over the mountains of Northern England and Scotland the grip of Winter might well persist weeks later than this.
 
 
Trevor Appleton
Contributing Weather Forecaster
Tuesday November 22nd 2011
 
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Summer Time

The clocks have gone back, but we could be in for summer time all winter long and double summer time in the summer half of the year if Mr Cameron’s latest idea gets the support of the Scottish Parliament.

The idea of Summer Time, or Daylight Saving Time, was first suggested in a whimsical article by Benjamin Franklin in 1784. In 1907 an Englishman, William Willett campaigned to advance clocks by 80 minutes, by 4 moves of 20 minutes at the beginning of the spring and summer months and to return to GMT in a similar manner in the autumn. In 1908 the House of Commons rejected a Bill to advance the clocks by one hour during the spring and summer months.
 
Summer Time was first defined in an Act of 1916 that ordained that for a certain period during the year legal time should be one hour in advance of GMT. The Summer Time Acts of 1922 to 1925 extended the period during which Summer Time was in force and so, from 1916 up to the Second World War, clocks were put in advance of GMT by one hour from the spring to the autumn.
 
During the Second World War, Double Summer Time (2 hours in advance of GMT) was introduced and was used for the period when, normally ordinary Summer Time would have been in force. During the winter clocks were kept one hour in advance of GMT. After the war Summer Time was invoked each year from 1948 to 1967. In 1968 clocks were advanced one hour ahead of GMT on Feb 18 and remained so until British Standard Time, during which clocks were kept in advance of GMT all year, came into force between Oct 27, 1968 and Oct 31, 1971.
 
The Summer Time Act 1972 defined the period of British Summer Time to start at 2 am (GMT) on the morning of the day after the third Saturday in March or, if that was Easter Day, the day after the second Saturday. It was to end at 2 am (GMT) on the day after the fourth Saturday in October. The duration of British Summer Time can be varied by Order of Council and in recent years has been changed so as to bring the date of the start of Summer Time into line with that used in Europe.
 
The European Union including the UK, has now adopted The Ninth European Parliament and Council Directive on Summer Time Arrangements in which it states that summer (or daylight saving) time will be kept between the last Sunday in March to the last Sunday in October. The changes will take place at 1am GMT.
 
Trevor Appleton
Contributing Weather Forecaster
Sunday October 30th 2011
 
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First Frost

 

When can we expect the first frost of the Autumn/Winter season, and what is the difference between an air frost and a ground frost which we often hear quoted by weathermen?

 

The dates of the first and last frosts are important to anyone who wants to grow anything outside. In general, the further south you are, and the nearer to the sea you are, the more frost free days you can expect, and the earlier you can put out (or later leave out ) those delicate plants.

 

The average date of first frost ranges from late September in Scotland’s Glens, to early October for Aberdeen, York and Oxford, late October for most of southern Britain, and December for the Scillies, Cornwall, west Wales and (perhaps surprisingly) the smaller Scottish Islands.

 

Air and Ground Frosts

 

Air temperatures are measured at a standard height (4 ft) above the ground (a grass surface), in a specially shaded and well ventilated screen (Stevenson screen). These standards are kept around the world in order that comparisons may be made.
 

Ground temperatures are made at ½ inch above short grass. At this level, temperatures on a still clear night are considerably colder than the air temperature - by as much 7 deg C.

 
Trevor Appleton
Contributing Weather Forecaster
Sunday October 16th 2011
 
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 To Autumn

 

SEASON of mists and mellow fruitfulness,

Close bosom-friend of the maturing sun…
 

 John Keats (1795–1821

 

There are several reasons for mist and fog to more prevalent in Autumn. Sea surface temperatures are still relatively high, lagging behind the highest summer temperatures (mid-July) by several weeks. Nights are longer, allowing for more cooling in the overnight period, and the sun is getting weaker, and less able to ‘burn’ off any mist or fog that has formed.

The word 'fog' is one whose origins are obscure. Its first use had nothing to do with mist or water, but was the name given to the new grass which grows up in a field after it has been cut for hay, or the long grass which is left standing in the field over winter. (There are various grasses even now with that element in their names, such as Yorkshire fog). In Scotland and the north, it could also mean moss, and hence a marsh or bog. The next step was to create the adjective foggy for places overgrown with long grass, or a place that was marshy or boggy.

Did you know? It would take 7 billion particles of fog to fill a teaspoon?
Trevor Appleton
Contributing Weather Forecaster
Wednesday October 12th 2011 
 
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Disclaimer.  The opinions expressed by the above forecaster are not necessarily those of Positive Weather Solutions.