Saturday 18th October
Friday turned out to be a pleasant, dry day with some brightness and minimal breeze from the east that saw the thermometer slowly climb to a peak of 14.7C at 15.08, which was 0.2C below average. The past night has once again been mild with a minimum of 10.2C at 06.55 early Saturday being 2.8C above average.
Today, Saturday, will be the last of the dry days under the influence of the recent dominant high pressure as it has been declining and heading towards Scandinavia and the Continent. The barometric pressure has been slowly falling significantly over these last two days with a current pressure of 1023.9mb at 08.00, down 9mb since its peak exactly a week ago.
It will be all change on Sunday as the anticyclone will be well to the east and the depression steadily moving in across the UK to be overhead on Monday. The first significant rain for over two weeks is likely to arrive on Sunday morning as weather fronts, associated with the depression, begin to make their way across the country. The centre of the depression will continue to ease towards the UK over the next twenty-four hours that will result in a significant pressure gradient and thus winds will increase and become very strong.
The current rainfall total for October is 19.3mm set against my 41-year record of 91.2mm for October from my long-term 5″ copper rain gauge, thus well below, which is likely to change significantly over the coming week as we will be subject to unsettled weather. This is the result of the changing track of the Jet Stream. For two weeks it has formed a loop to the north over the UK, the Omega loop, that meant the UK was on the warmer south side of the steam allowing high pressure to develop from the Azores region. Over the last two days the track has repositioned to now be to the south of the UK, thus we are on the cooler, north side of the track and it will hustle low-pressure systems in from the Atlantic. Rain arrived over west Cornwall before dawn and is edging very slowly eastwards, however, we should have a dry evening for the Mop Fair although there might be some drizzle towards midnight.
It is the Big Mop Fair weekend thus an appropriate image.