Tuesday 7th April
The change to the wind direction, with air coming from the southeast on Monday, brought several hours of warm sunshine between breaks in the limited cloud that lifted the maximum temperature to 14.8C at 15.48. This was the highest temperature this month and in fact the first above average for April. It was another dry day with peak UV in the middle of the ‘Moderate’ category. The minimal temperature overnight was also above average, just at +0.2C, with a low of 4.1C logged at 06.33 early Tuesday.
Tuesday began with glorious sunshine after sunrise that had lifted the temperature to 6.8C by 08.00. Our weather is now dominated by high pressure centred to the east of the UK that will continue to feed a warmer and drier air steam from Southern France and Iberia, who have been experiencing very warm weather. The breeze will be ;lighter than recently and from the southeast or east-southeast.
The anticyclone will will be with us until Thursday when it will give way to low-pressure systems edging in from the Atlantic. Thursday onwards, after a fine day, a cold weather front will sweep across the country that, as it’s name suggests, will pull in a cooler air stream. This will see temperatures drop to around average from Friday but continue dry. However, as the wind then veers into a southwesterly quadrant, the air will not only be cooler but carry more moisture due to its travels across the ocean resulting in cloudier conditions that might bring the first rain for a week on Monday.
There is hope that high pressure will return on Friday that will moderate the low pressure systems and weather fronts heading in from the northwest.
N.B. I am delighted that the flow of data has now resumed to my equioemtn and that the live feed has been up and running since last night. I understand from David Instruments that they are having to rewrite some software for particular graphics as a result of the recent Apple upgrade. At least I have the vital numerical data.
More on the Met Office release regarding April showers.
Not all April showers arrive from the Atlantic. Many develop much closer to home through a process known as convection. On days with sunshine, the ground warms quickly, especially after the darker winter months. This warmth is transferred to the air above the surface, causing it to rise.
As this rising air cools, water vapour condenses to form clouds. In spring, these clouds are often cumulus clouds, recognisable by their tall, puffy appearance. Unlike layered cloud associated with frontal rain, cumulus clouds grow vertically. If they grow tall enough and become saturated, they can produce showers.
These showers can form rapidly, sometimes within an hour or two of sunshine developing, which explains why April weather can change so quickly from bright and pleasant to wet and blustery.
Why showers can be heavy and localised
A defining feature of showers is their hit-and-miss nature. Because they fall from individual clouds rather than long, continuous bands, rainfall can vary dramatically over short distances. It may be pouring with rain in one town while a nearby area remains completely dry.
Showers also tend to be short-lived but intense. As a cloud develops, produces rain and then collapses, it can release a burst of heavy rainfall before clearing just as quickly. This is why April showers are often described as “passing through” rather than settling in for the day.
In some cases, showers can also be accompanied by hail or thunder, particularly later in the spring when the atmosphere becomes more unstable.