Author: Eric Gilbert

Friday 9th October
After a bright and sunny morning on Thursday cloud drifted across around 13.00 for an hour or so before that cleared and the sun reappeared resulting in a maximum of 14.9C at 15.38, which was exactly average for October.

Increasing cloud overnight was due to a warm front crossing the area that resulted, unusually at night, in the thermometer making an about turn after a minimum of 9.6C at 22.48 and then rising 6C by dawn.

Friday arrived with the residual cloud from the warm front and a temperature of 15.7C at 08.00, which was already 0.9C above the average maximum for October and made it the warmest start to a new day since the end of September. Another weather front has started to cross the country, this time a cold front, with the air stream originating around Iceland, that will bring rain later this morning and into the afternoon, that could be heavy for a short time. Under the cloud and rain it will be a cool day.

The forecast pressure charts show an absence of weather fronts over the weekend as the barometric pressure begins to build. Under the temporary high pressure we are likely to enjoy a fine weekend with sunny periods although occasional shower clouds might arrive during Saturday afternoon thanks to a trough of low pressure that is forecast to briefly form over Northern England. Any shower activity will be minimal but accompanied by the breeze increasing in strength.

We are well into the hurricane season but until now there has been an unusual absence of disturbances forming off the west coast of Africa that as they head westwards can develop into hurricanes. That changed from yesterday, as the named storm of Isaias has developed into a hurricane that will result in a life-threatening storm surge and damaging hurricane force-winds over the Florida Panhandle. There is the suggestion that the unusually strong El Niño over the Pacific is moderating the development of storms in the Atlantic.

Isaias came one day shy of tying a 121-year-old record for the latest-forming initial hurricane of the Atlantic season.

Thursday 8th October
Wednesday began wet and cool, and got cooler as the day progressed, thanks to the strengthening breeze from the north also the cold airstream behind the weather front. The morning began with a temperature of 12.9C at 08.00 and instead of getting warmer, the temperature steadily fell away to reach 10.6C at 15.14 then continuing to fall again until reaching a minimum of 4.1C at 07.39 early Thursday. The drizzle and light rain continued for most of the afternoon although the cloud did thin and allow weak sunshine to break through at 16.40.

Thursday dawned bright and clear with welcome sunshine soon after sunrise. A temporary ridge of high pressure has pushed in overnight that will give us a fine, dry and sunny day. But it will be all change again on Friday as another cold front is forecast to cross the country that will mean a wet and breezy day until later in the afternoon. As the day progresses the breeze will back from the northwest to west-southwest, a return to an Atlantic pattern of weather with a warmer airstream.

Over the weekend the forecast pressure charts indicate a lack of weather fronts arriving from the west so a pleasant couple of days with temperatures retaining to around the October average with the wind predominantly from the west. However, the pressure charts indicate a disturbed Monday as at the moment at least three weather fronts are likely to cross the country.

Part two of the Met Office article on El Niño. Their view on recent disturbing headlines on possible extreme weather.

A spokesperson said: “Through the latter part of the winter, following a peak in El Niño, the stratospheric Polar Vortex can become weaker, leading to an increased chance of Sudden Stratospheric Warming (SSW) events unfurling, increasing the potential for cold weather.”

The forecaster said “it was too far away to give any forecast information” about how this might affect the UK and it remains “just one possible outcome dependent on many competing factors”

This year’s “super El Niño” has already shattered global records to become the most powerful event in history.

Professor Adam Scaife, head of long-range predictions, said: “We have been signalling for months that the developing El Niño will be an unprecedented event.”

“The fact that it has already exceeded previous records – with several weeks to go before it peaks later this year – shows the enormity of this El Niño.”

Wednesday 7th October
Tuesday was the last of the warm, dry and sunny days that saw the thermometer rise to a maximum of 20.6C at 14.34, after a slightly cloudier period around midday. The high was 5.7C above my October average. The cloud began to build in the evening as a weather front edged closer that meant another mild night with the thermometer not sinking below 12.2C at 04.49, which was 4.4C above average.There were a few spots of rain observed around 23.00, from the first broken and light showery activity ahead of the main rain band, but not measurable.

First light on Wednesday revealed a wet and gloomy outlook. The weather front is currently passing over the UK that produced the first measurable rainfall at 04.03, slightly heavier just before 05.00 and then light but continuous into the morning that had produced a fall of 11.6mm by 08.00. The rain will likely peter out early afternoon.

The weather front is a cold weather front that is bringing behind it a cooler air stream with the very light wind already having veered into the northwest. Wednesday will be a cool day under the rain, cloud and cooler air flow that will see a maximum well below average for October.

The cloud will thin and clear overnight. Behind the weather front a minor ridge of high pressure will push back across the country giving us a fine day on Thursday with the daytime temperature recovering to around the October average.

The forecast pressure charts indicate another weather front will cross the UK on Friday, resulting in a mainly cloudy day with possible light shower activity.

The extended period of consistent high pressure, that gave us the warm and dry conditions for so long, has now given way to a more unsettled and cooler period with the wind veering back into the southwest on Friday with a more moist airstream coming off the Atlantic over the weekend.

With a wet morning and the early autumn colours still muted, I will pause the images of Savernake Forest in full colour and start a new sequence of early Autumn in Exbury Gardens, Hampshire.

Met Office issues polar vortex warning as ‘largest El Nino in living memory’ threatens winter of snow and storms

The Met Office has weighed in on whether this year’s El Niño – which could be ‘unprecedented’ and the ‘largest in living memory’ – will trigger a polar vortex and send Britain into a deep freeze

Snow and bitterly cold temperatures could soon hit the UK as the Met Office weighs in on whether this year’s El Niño might trigger a polar vortex.

El Niño could, the Met Office warned, “potentially unleash cold snaps, heavy snow, and storms across the country”.

It’s also feared the weather phenomenon could destabilise the polar vortex, potentially sending Britain into a deep freeze.

This leads to a weakened jet stream, sending severe, freezing Arctic air into North America and Europe.

But according to the Met Office, a polar vortex-driven cold snap or snow remains unlikely this autumn, with freezing temperatures more likely to hit later on during winter.

Tuesday 6th October
Monday was another dry and warm early Autumn day with the thermometer still rising above the average, +5.6C, with a peak of 20.5C at 15.10. The last night was also mild with a minimum of 11.9C at 06.16 early Tuesday being 4.4C above average.

Af first light on Tuesday there was no evidence of fog but just after 07.00 a whisper of radiation fog began to form in the River Og valley that thickened as the temperature began to rise and then fall again around sunrise. By 08.15 the fog had thinned and lifted from the valley.

The barometric pressure continues to ebb away, down another 5mb since yesterday, as the high pressure withdraws westwards and the depression to the north begins to replace it. Later this afternoon there will be a significant change in direction from a general southwesterly to north, as a result of these pressure changes.

A depression has recently been forming over the Bay of Biscay and Portugal that will emphasise the change in weather pattern. This evening and tomorrow it will push northwards with the moist, warm air from the south colliding with the cooler air from the north. There is now considerable confidence that this meeting of opposing air streams will produce a significant fall of rain over southern England during Wednesday morning. The first light rain is likely to arrive just after midnight and become heavy around dawn.

During late Wednesday afternoon the weather front will move away eastwards that will see the clouds thin and the rain stop. By Thursday the wind will have backed into the northwest resulting in sunny intervals appearing, but the maximum temperature will below average, making it feel chilly compared to recent days.

Part 2 of the Met Office article on the HadUK-Grid using data from numerous weather stations across the UK

From observing points to a continuous map

To fill the spaces between weather stations, HadUK-Grid uses a commonly-used statistical technique known as interpolation. This extends information from observing sites across the surrounding area and accounts for geographical influences such as distance, terrain, altitude and proximity to the coast.

The result is a continuous map that reflects the varied geography of the UK rather than simply presenting a series of isolated observations. In order to represent the UK on a grid, the dataset divides the country into grid squares measuring one kilometre across. Each square contains a scientifically derived estimate of the climate at that location.

These estimates cover a broad range of climate variables, including maximum, minimum and mean temperature, rainfall, sunshine and frost days. Because they are brought together in a consistent system, the data can be studied at several different scales. Users can examine local detail, create regional maps or calculate averages for the UK as a whole.

This flexibility is particularly valuable when describing the UK’s climate. A national average temperature, for example, does not mean that every part of the country experienced the same conditions. Instead, it is a spatial average calculated using the grid squares across the UK, summarising a complex national picture in a single statistic.

Putting today’s weather into historical context

HadUK-Grid is not limited to recent conditions. For some climate variables, its records extend back for well over a century, provided there are enough robust observations available. This creates a consistent historical record that is less dependent on the opening or closing of any individual weather station.

That long-term view allows scientists to compare current conditions with the past in a consistent way. It helps provide the evidence behind statements such as “warmest year on record”, “wettest winter” or “sunniest month”. These assessments are not based on one station or one part of the country. They draw on a robust, peer-reviewed method that brings observations together to represent the UK more completely.

Monday 5th October
Sunday was a very pleasant autumn day with plenty of sunshine, although a slightly cloudier period occurred between 12.00 and 13.00, which limited the eventual maximum to 21.4C, even so, this was 6.5C above average. Initially the sky was clear in the evening, however, advance cloud from another weather front began to edge across from the west just after midnight, that meant the drop in temperature was limited, with a minimum of 12.9C at 06.55, this low was 5.4C above average. Both day and night were exceptionally mild for early October.

First light on Monday revealed the extent of the weather front and its associated cloud with misty conditions draping the Marlborough Downs and Savernake Forest. The air was very humid with moisture being felt in the air but no measurable precipitation. There is a slight possibility of some brightness as the afternoon progresses, if the cloud cover thins, with hopefully a sunny interval or two. Whatever, the flow of humid, warm air on a light south-southwest air stream will mean another mild day and night ahead.

Tuesday will follow a similar pattern although any sunshine is likely to be minimal, however, this will be the last very mild day and night.

The barometric pressure is slowly falling indicating the change in the weather pattern, having dropped 5mb since yesterday with a reading of 1025.7mb at 08.00.

As the high pressure relocates further southwestwards, the air will come around its northern flank on Wednesday and arrive from a more northerly direction, which will be a much cooler airstream that will result in a maximum probably just below the October average, perhaps a fall of six or seven degrees below the recent highs, so feeling chilly. A weather front will traverse the country in the morning with its associated cloud. There is increasing confidence that the cold front will produce several hours of possible light rain.

The forecast charts for Thursday indicate it will be a bright, dry and sunny day as the cloud from the weather front will have cleared and the wind beginning to veer a few degrees to come from the northwest but still a chilly day. By Friday, the forecast carts indicate that the wind might have backed further to return us to a pattern of moist, warmer air stream from the southwest with possibly further light showers, especially in the morning, early days for much confidence.

The trees are beginning to show signs that autumn is arriving with limited change in colour appearing on the leaves. For the next few days I will attach images taken in SavernaKe Forest, that as the weeks progress, will reveal the full colour of the beech trees in their transformation, before winter arrives.

HadUK-Grid: assessing the UK’s climate over time
Author: Met Office

Part 1
Every day, weather stations across the UK record the conditions around us.

They measure temperature, rainfall, sunshine, wind and much more, creating a vast collection of observations that helps us understand the weather as it happens.

But weather stations cannot be located everywhere. There is no instrument on every hillside, in every valley or on every street. The observing network also changes over time as stations open, close or move. So how can we bring individual measurements together to understand the climate of the whole country?

The answer is HadUK-Grid.

HadUK-Grid is a digital representation of the UK’s climate, built using observations from hundreds of weather stations. It turns measurements taken at individual locations into a complete and consistent picture covering the country, allowing scientists to examine conditions across space and through time in a consistent manner.

More of this article tomorrow