Meteorologically Winter began on the 1st December and it felt like it. The very chilly air from Scandinavia meant a very cold day on Friday as the thermometer rose very, very slowly to a miserable 0.7C at exactly 14.00 on Friday that was a significant 7.2C below the 39-year average. The low cloud and misty conditions persisted throughout the day so no UV and no global sunshine.
The temperature slowly dropped during the evening, hovering around -1.0C, then after midnight began to fall further reaching a minimum of -4.1C at 07.37 Saturday. Daylight revealed freezing fog that became more dense after dawn with a minimum visibility of around 200m at 08.00 as the temperature reached its lowest.
The barometric pressure has been rising since Friday with a reading of 1016.7mb at 08.00 Saturday as the depressions ease away. This repositioning will mean the air that currently is very calm but from the northwest will slowly back during the day to initially the west, then south, and likely southeast by evening. That significant change in direction heralds a change in the temperature overnight so by dawn on Sunday the temperature is likely to be above freezing.
November 2023 review
Storm Ciaran arrived with heavy rain late on the 1st and strong winds on the 2nd. A record low barometric pressure of 957.1mb was recorded at 06.05 on the 2nd as the centre of the storm passed just to the north of our area.
This extremely deep, low-pressure system was caused by freezing temperatures over Canada and temperatures of 30C over California. The temperature discrepancy of over 30C that occurred over a modest distance spawned Storm Ciaran, that raced across the Atlantic on a Jet Stream travelling at over 200mph. The centre of the depression dropped rapidly, called meteorologically ‘explosive cyclogenesis’ or ‘weather bomb’. It was the lowest pressure over the UK for a November storm.
On 11th we had a more unusual weather pattern that had developed with a col centred over the UK. A col sits in the middle of two areas of opposing high pressure, north and south on that day, and two areas of opposing low pressure, west and east. That created relatively settled conditions, especially inland, with weakening winds and clearing skies allowing a short-lived ground frost and misty conditions to become established albeit temporarily on the Saturday morning.
Storm Frederico, not one of ours as named by the French Meteorological Organisation, stayed to the south of the UK producing much rain, 10.6mm, but not gale force winds, thankfully. This brief period also produced mild days with the warmest day of the month on the 18th when a maximum of 14.8C was recorded.
A few very welcome dry days arrived on the 22nd due to a very high-pressure system to the west of the UK. The temperatures were down a few degrees after the earlier very mild air but still just above average by day and night.
By the 24th the high pressure had relocated and formed an elongated system reaching from Iceland down to Spain. To the east was the remainder of a deep depression. The wind circulating clockwise around the anticyclone, and reverse around the depression, brought a change in wind direction from west to northwest then a blast of Arctic air on a strong northerly. Wind chill occurred in the gusty northerly making it feel a least 2C below that registered on a thermometer. During the evening, under clear skies and the cold air stream, the thermometer dropped below freezing at 20.11, then -1.0C at 22.20. However, it wasn’t until 05.00 on the 25th that the thermometer dropped more rapidly with -2.0C at 05.15, then -3.0C at 06.05 and -4.3C at 08.13 making it the coldest night since 10th February.
The month ended with the wind veering into the northeast so Arctic air was replaced by an air stream from Scandinavia, but it was just as cold! A maximum of only 4.5C was recorded on the 29th and just 2.1C on the 30th, which was a significant 8.1C below the 39-year average.
November was a relatively mild month overall with the mean temperature 0.42C above the long-term average.
The rainfall of 121.6mm was exactly equal to that recorded in October being 134% of the 39-year average or plus 30.7mm. The average November rainfall has shown an upward trend since this station started in 1984 when in the 1980s the average was 228mm, now risen to 242mm.The rainfall for the period January to November was 1007mm being 247mm above the long-term average.
There were four mornings that began with an air frost and one day with fog.
Autumn 2023
It was a mild and damp autumn with the mean temperature being 0.61C above the 39-year average and the rainfall of 347 mm being 104mm above the long-term average.
The average temperature in the 1980s and early 1990s was around 9.8C but this has risen steadily since 1996 to reach almost 10.4C by 2023. The trend for rainfall has also been upwards, rising from an average around 225mm in the 1980s and early 1990s to around 245mm over recent years.
A view into the future?
Artificial Intelligence (AI) could save lives by warning where a hurricane or storm will hit land much sooner than traditional forecasting systems, researchers say.
A new AI tool from Goole DeepMind predicted where September’s hurricane Lee would make landfall in Canada three days ahead of existing methods.
AI’s speed and ability to analyse past events to make predictions make it a game-changer, say scientists. AI models are trained from data that is generated by traditional approaches, so we will still need these to gather data.
Traditional weather forecasts take vast amounts of computing power. A new AI tool called GraphCast, created by Google DeepMind, produces its forecasts in less than a minute using a very different approach to current forecasts that currently involve estimates of hundreds of factors including air pressure, temperature, wind speeds and humidity at different levels of the atmosphere around the globe.
The best models now take on hundreds of millions of readings around the world every day. These come from a range of sources including weather stations, satellites, balloons sent up into the atmosphere, buoys on the oceans – even readings taken by sensors on the noses of commercial jet planes.
However, scientists warn that climate change will limit the predictive power of AI based tools and question if AI-based systems are able to pick up new extremes when these systems have only been ‘trained’ on previous weather conditions.