The westerly breeze on Thursday continued the run of warm, moist air from mid-Atlantic as it circulated clockwise around the anticyclone before crossing the UK. The thermometer rose to a maximum of 10.4C, which was 2.4C above the 39-year average and the warmest day since 14th January when we enjoyed a similar warm period.
It was essentially a dry day although there was moisture in the air from time to tine from low clouds, but not measurable. The UV level at 1.1 was still classed as ‘Low’.
The past night has been mild with the thermometer not sinking below 8.2C, which was 6.6C above the average, due to thick cloud cover restricting warmth being lost to the atmosphere.
Friday arrived with similar conditions to previous days, total cloud cover and a mild westerly air stream. The barometric pressure continues to rise with a reading of 1031.8mb at 08.00, the highest for a week.
January 2023 Review
The first half of January was dominated by a succession of depressions hurried along by the jet stream to the south of the UK. The mild, maritime air was brought from the Atlantic on a predominantly south-westerly breeze. Maximum temperatures were above the average for every day, until the 15th, often in double figures, with a peak of 12.1C on three days, namely 3rd, 5th and 10th, which were a significant +5.1C.
The mild, moist air meant rainfall every day until the 16th with significant falls of 13.8mm and 25.1mm on the 3rd and 11th respectively.
There was a dramatic change from the wet and windy conditions to cold, drier weather as a depression moved along the English Channel on the 15th / 16th that saw the wind begin to veer into the northwest. The first below average maximum in January of 6.9C (-01C) occurred on the 15th followed by a return to night frosts.
The next ten days brought intense cold by day and night with both maximum and minimum below average, some significantly below.
The coldest day was the 17th when the thermometer refused to rise above 1.2C, which was 5.8C below the 38-year average., The 22nd was not much warmer with a maximum of just 2.1C.
The nights became successively colder with the lowest temperature recorded in the early hours of the 24th when the thermometer dropped to -8.0C at 07.34, which was 9.3C below the average and the coldest night in January.
However, our very low temperatures were as nothing compared to -31C in North Korea and -53C in the town of Mohe, northern China this month!
This weather pattern was due to an extensive ridge of high pressure, reaching east to Russia, that brought calm days with very little wind movement, maximum of 2mph on the 22nd. The barometric pressure rose from a low of 986.6mb on the 16th to a maximum of 1040.8mb on the 24th. This very high reading was the highest since March 18th 2022 (1042.4mb). The air movement during this period slowly veered from the north to the east.
The only redeeming aspect of this very cold period were the many hours of sunshine, which contrasted with the gloomy, dark days at the beginning of the month. Also observed, indicating that we had passed mid-winter, was the UV level that began to show a slight rise to 0.8 from 0.5 or 0.6, although a small rise, the highest since 20th November.
During this continuous, very cold spell, the cold, not surprisingly, began to seep slowly into the ground. The soil temperature at a depth of 5cm was last above freezing on the 17th with a reading of +0.2C. However, this began to drop over the next 7 days to a low of -4.6C at 08.00 on the 24th.
There was a significant change in the weather during the night of the 24th/25th. During the evening the thermometer dropped steadily, as on previous nights, this night to -5.5C. At 00.34 the thermometer stopped falling and began to rise. This was due to the intense high-pressure system beginning to relocate that saw the air movement change from the easterly quadrant as in the previous week, to a westerly, a much warmer airmass from the Atlantic. By 08.00 on the 25th the thermometer had risen to -1.3C.
Subsequently the breeze came from the north-west then north, often a cool air mass, but this time the air came from mid-Atlantic riding around the top of an Atlantic anticyclone in a clockwise direction before falling back from a northerly quadrant, therefore the air originated from the warmer Atlantic, which also contained more moisture than previous days, 99% humidity on the 25th. Slowly the air temperatures began to recover as the ground began to lose its coldness after the severe frosts. The soil thermometer registered -3.7C at a depth of 5cm on the 22nd but at 08.00 on the 31st had recovered to +3.3C A maximum of 10.9C on the 31st was 3.9C above average and the warmest day since the 6th.
Those who regularly tap a wall barometer to see whether it is rising or falling, will have noticed that the needle had moved to the extreme right earlier in the month, on the 24th, as the barometric pressure of 1041.1mb was the highest pressure since 12th January 2022 under a large anticyclone that extended far to the east over Russia.
The mean temperature for January was 0.3C above the 39-year average principally due to the relatively warm days at the beginning of the month (+0.9C) whereas the frosty nights (-0.6) reduced the monthly mean. The extremes were +12.1C on both the 3rd and 5th and -8.0C in the early hours of the 24th.
Almost all rainfall was limited to the first fifteen days in the month with the wettest occurring on the 11th with 25.1mm and 13th with 22.8mm. The monthly rainfall amounted to 104.6mm being 117% of the 39-year average or +15mm. From the 16th to the end of the month every day was dry except for a minimal amount of 0.1mm on both the 18th and 26th.
There is a definite upward trend for January rainfall over the past 39 years that has seen it increase by 5mm.
An air frost was recorded on 12 days being average over the past 39 years.
Analysing the diurnal range of temperatures over the past 39 years there is again a definite upward trend. In the 1980s the average range between day and night was 10C, however that has slowly increased to produce an average range of 12C.
The soil temperature at a depth of 5cm saw considerable variation with a temperature of +10.2C at 08.00 on the 4th, during the mild spell, dropping to -4.6C at that time on the 24th following the intense overnight frosts.
Selected statistics from 2022:
Hottest day: 36.7C on 19th July
Hottest night: 18.2C on 31st July
Coldest night: -9.4C on 16th December
Coldest day: -0.6C on 14th December
Rainfall: 712mm (Av. 850mm)
Daily evaporation: 5.23mm on 22nd June
Recently I came across an interesting, readable article that explained the two meteorological events of La Niña and El Niño that are often referred to when extreme weather events are discussed.
New data shows that 2022 was the fifth hottest year for Europe since records began.
But scientists are warning that 2023 could be even warmer, as a climate phenomenon called La Niña – which has been suppressing global temperatures – comes to an end.
La Niña is part of a climate phenomenon called the El Niño Southern Oscillation (ENSO) system.
It has two opposite states – El Niño and La Niña – both of which significantly alter weather patterns across the globe.
For the last few years, the world has been in successive La Niña periods, which have lowered temperatures and brought heavy rains to Canada and Australia.
Winds blowing along the Equator above the Pacific Ocean – from South America in the east towards Asia in the west – were stronger than normal.
These “trade winds” piled warm water off the coast of Asia, raising the sea surface level. In the east, near the Americas, cold water flowed upwards to the surface.
During El Niño the opposite happens – weaker trade winds mean the warm water spreads out back towards the Americas, and less cold water rises towards the surface.
The phenomenon was first observed by Peruvian fisherman back in the 1600s.
They noticed that warm waters seemed to peak near the Americas in December, and nicknamed the event “El Niño de Navidad”, Christ Child in Spanish.
How do El Niño and La Niña change the weather?
Not every El Niño or La Niña event is the same, but scientists have observed some typical effects:
Temperatures
Global temperatures increase by about 0.2C during an El Niño episode and fall about 0.2C during La Niña.
El Niño means warmer water spreads further and stays closer to the surface. This releases more heat into the atmosphere, creating wetter and warmer air.
The hottest year on record, 2016, was an El Niño year.
Between 2020 and 2022, the northern Hemisphere had three La Niña episodes in a row.
Despite the La Niña triple, the EU’s climate monitoring service says that 2022 was the fifth warmest year on record.
Prof Adam Scaife from the Met Office said: “Global average temperature over the last three years has been at near record levels, but it would have been even higher without the cooling effects of a prolonged La Niña.”
A 0.2C temperature rise would add about 20% to the existing global temperature rise from climate change.
The Met Office expects La Niña to end later this year, “raising the prospect of even higher global temperatures”.
Changes to rainfall
During El Niño events, the warmer water pushes the Pacific jet stream’s strong air currents further to the south and the east.
This brings wetter weather to southern US states and the Gulf of Mexico, while the north of the US and Canada remain drier.
Asia, Australia, and Central and Southern Africa typically experience drought.
In La Niña events the opposite is seen: drought in the southern US, and heavy rains in Canada and Asia.
In October 2022, Australia experienced record rainfall and flooding driven by La Niña.
Tropical storms
La Niña also generates more hurricanes in the Atlantic – affecting Florida and other southern states of the US – but fewer tropical storms in the Pacific.
The opposite is true of El Niño events.
How often do these episodes happen?
El Niño and La Niña episodes typically occur every two to seven years, and usually last nine to 12 months.
They don’t necessarily alternate: La Niña events are less common than El Niño episodes.
How do these events affect us?
The extreme weather events caused by El Niño and La Niña affect infrastructure, food and energy systems around the world.
The drought in Canada and Asia caused by the 2014-16 El Niño phase resulted in crop failure and damaged the food security of more than 60m people, according to the UN Food and Agricultural Organisation.
During El Niño events, less cold water rises to the surface off the Americas which brings fewer nutrients from the bottom of the ocean.
That means there is less food available for marine species like squid and salmon, in turn reducing fish stocks for South American fishing communities.