Snow days bring welcome additional, unplanned holidays to children in Kent. They seem to happen most year. Folks are ready to believe that the weather related closure of schools is new and possible the result of over active and risk averse health and safety regimes.
The Guardian’s recent piece on Victorian weather related school absences suggests that this phenomena is not recent. Children often stayed away from school during cold and wet weather, probably because of the lack of decent clothing and foot wear.
The Reuters release on Friday about a toxic smog over Lahore present another dimension to school closures. Local forecasters predict that the smog will persist well into December.
I wonder if London ‘pea soupers’ ever forced schools to close.
Heavy rain and flooding has been a feature of the first half of November 2019. The UK weather has turned a corner now to more settled conditions. The reasons for this lie out in the Atlantic.
Some 300 nautical miles south east of Cape Farewell (southern tip of Greenland) there is an intense area of low pressure. Analysed by the UKMO at 967 mb last night it is very intense. The lowest recorded pressure ever was in 1979 when Typhoon Tip brought us down to 870 mb, but that was in the tropics; 967 mb is very low for the mid-latitudes.
The marvellous website Earth.nullschool.net gives us the opportunity to investigate the winds around this low at different heights. Current flows for the surface and top of the atmosphere are as follows.
Often these patterns are different; different winds at different levels are what causes changes in weather patterns. The fact the winds is uniformly circling the depression at all levels makes this a more static pattern.
The UK is somewhat to the West of this enormous system. The graphics show an intense stream of air piling south over us at the top of the atmosphere. Whole regions of air are being forced downwards causing high pressure and settled weather.
High pressure in winter can bring sunshine or settled gloom with. Sunshine is accompanied by frosts at night.
In general, the development of weather systems over middle latitudes will be driven by the upper winds which circulate around the earth. The mathematics and dynamics of these processes is complicated but after much work development areas can be related to the pressure pattern at 30 000ft or so.
The study of the mathematics is very rewarding and brings together the conservation of momentum (and angular momentum), Newton’s Laws and the rotation of the Earth.
For the moment, the following images show the relationship of the 300mb contour chart with convergence and divergence. The fact that air cannot be created or destroyed in the flow means that:
if upper level air is in CONVERGENCE the air is forced downwards causing subsidence, a build up of pressure and good weather, and,
conversely, if upper level winds are in DIVERGENCE air is sucked upwards causing condensation, droping of pressure and bad weather.
Applying the rules in these images to the latest 250 mb flow (300mb not available, but 250 mb close) and surface flow form Earth.nullschool.net and then looking at the latest forecast sequence from the UK Meteorological Office (weathercharts.org) will give you an insight into current atmospheric dynamics and weather development.
Folklore says St Martin’s Day, 11 November, brings with it a settled spell of weather known as St Martin’s Summer.
Disappointingly, the UKMO forecast chart for St Martin’s Day (weathercharts.org), 11 November 2019 leads to a text book forecast: blustery showers, some of which will merge to give longer outbreaks of rain.
History (wikipedia) tells us that St Martin was a Roman cavalry soldier who resettled as a Bishop on leaving the army. Leaving the Roman equivalent of brightly coloured trousers behind, his Christian career gained some meteorological notoriety in a snow storm. Turning the tools of his military career to pastoral use he cut his cloak in two in order to share half of it with a beggar.
Mid-latitude weather can always be relied upon to give some settled spells and there is enough lore out there to expect such a respite on many dates. In fact, Shakespeare connects St Martin’s Summer with a similar spell of calm weather, halcyon days, expected at the solstice. Henry VI, Part 1, act 1, scene 2, line 131:
Expect Saint Martin’s summer, halcyon days.
The current forecast from the Met Office doesn’t really promise summer:
with heavy rain for the commute. Tuesday and Wednesday seem better, but low pressure is not far away.
The time is always ripe for some continued Autumnal feasting as depicted in the featured image.
October 2019 was a typical Autumnal month of mobile UK-Atlantic weather with a succession of depressions, fronts and high-pressure systems bringing unsettled and changeable weather. At the at the start of the month the ‘eyeballed’ mean low pressure track was to the North West, with depressions moving to the North East through the Iceland/Hebrides gaps trailing fronts across the country giving rain with some settled spells in between. As the month progressed, this track gradually moved south, as befits the transition of the seasons. Slower moving complex lows were centred over the UK on and around the 20th. These were followed by some more intense areas of high pressure responsible for the hard frost in Scotland at the end of the month.
Beach hut owners on the North Kent Coast acquired their plots in the full knowledge that the once if fifty year storm would reduce their hut to broken planks. In fact the last weather disaster in the folk memory was the great flood of 1953. In fact, the University of Brighton’s Screen Archives South East supplies some photographic evidence of the aftermath:
The Met Office’s UK Sea Level Projections to 2300 reports that “at some locations the 1 in 10,000-year flood event of today could be expected more than once per year by 2300”. This seems to be bad news for beach hut owners; the once in fifty year storm might be expected every week!
These new sea level projections developed by the Met Office Hadley Centre have been published in a report by the Environment Agency. They show continued rise beyond 2100 under all climate change scenarios.
Important news for all; not just beach huts at stake.
September 2019 started and ended with an unsettled westerly flow of fronts and depressions but enjoyed a more settled, high pressure dominated, spell in the middle. Slightly warmer than the long term (1981-2010) average, with a little more rain and sunshine than normal.