Dramatic change in wind direction overnight

Wednesday was the last of the very warm days as the thermometer rose to a peak of 18.9C being 8.5C above the 37-year average in the light southerly air stream.

Overnight the temperature slipped downwards to a minimum of 7.6C. However, just after 04.15, following a calm night, the wind suddenly changed from southerly to northeasterly and by 08.00 wind chill was evident making it feel at least 1C cooler outside than indicated on the thermometer. The high pressure in the Atlantic, to the north west of the UK, is intensifying bringing the air from around Iceland.

A totally cloudy sky greeted Thursday with the northeastery wind currently gusting to over 20mph making it feel very chilly.

March 2021 Review

A relatively dry month.

March began with persistent winds from the northeast that meant temperatures were depressed. Thick cloud carried in overnight from the North Sea blanketed the area that on one morning limited visibility to 200m. On the 4th the thermometer struggle to reach just 4.4C, which was 6C below the 37-year average.

There followed several nights when an air frost occurred, the coldest being in the early hours of the 8th with a minimum of -3.3C being 5.7C below the long-term average. However, just after dawn the temperature had risen to 0.7C with no evidence that a hard frost had occurred.

The wind direction changed significantly from the 8th backing into the west and then south as the anticyclone eased away and a depression approached from the Atlantic driven on by a strong jet stream. A peak gust of 42mph was recorded in the early hours of the 11th.

The succession of weather fronts during this period gave us three days of rain with the wettest on the 12th with 8.5mm.

A welcome anticyclone approached on the 13th and intensified over the UK for ten days reaching a peak pressure of 1035.8mb. This brought fine weather and minimal rain with daytime temperatures above average but due to clearing skies many cool nights.

Several rain bands crossed the country on the 25th and 26th adding another 8.3mm on the latter day, the second wettest day in what proved to be a relatively dry month.

The month ended with a flow of Continental Air on a southerly air stream that arrived from North Africa and Iberia. The 30th saw the thermometer soar to a maximum of 22.1C, which was 11.6C above my 37-year average and a record for this station set up in 1984. I understand that it was the warmest March day since 1968. The 30th didn’t reach such heights but a peak of 18.9C was the second warmest for March.

Overall March gave a mean temperature 0.4C above average that was principally due to the last three days of unusual warmth. By contrast, we had 6 nights when an air frost occurred with -3.3C during the early hours of the 8th the coldest.

March 2021 was a relatively dry month with only 36.6mm of precipitation recorded. The total was 23.2mm below the 37-year average and the driest match since 2015 that followed a below average total for February. There were 20 totally dry days when the long-term average is 16.

Although it was an above average month for temperature it was not thanks to many hours of sunshine as the solar energy total was only 82% of the 12-year average. The UV level reached a ‘Moderate’ level on just 6 days.

It is interesting to analyze the diurnal temperature range for March since 1984 when I find that in the latter 1980’s the average was 15C but recent years have seen the average range increase to 17.5C. On the 30th our human frame had to adjust to a diurnal range of 22.5C.

I came across an interesting item recently, having commented in a recent monthly review about the importance of accurate data when monitoring the oceans with regard to CO2 and the rise in sea level. A new era of sailing for science began in January with support for vital ocean observations from the high-profile round-the-world Vendée Globe yacht race. Ten of the skippers took with them scientific instruments including either drifting buoys that gather climatological information or Argo floats that analyse seawater. During the race they deployed all the drifting buoys and almost all the Argo floats at agreed co-ordinates in the Atlantic. The World Meteorological organization stated recently that “We cannot stress enough the importance of the oceans, without them there would be no life on earth. As major players in our climate system, they store over 90% of the excess heat from radiative forcing and absorb about a quarter of the human-produced CO2 emitted annually”.

Seven meteorological buoys and 3 profiling floats, operated respectively by Météo-France and Argo France, were deployed by the IMOCA skippers at agreed positions in the Atlantic Ocean.  Four skippers also carried onboard equipment to measure essential ocean variables such as sea surface salinity, temperature, CO2, atmospheric pressure, as well measure the microplastics pollution at sea. The article concluded that “usually, the deployment of ocean observing instruments is done through research oceanographic ships, which are very costly and not able to sail everywhere throughout the ocean regardless of the season. Racing yachts can reach remote and not yet well sampled areas of the ocean, filling critical observational gap”.