Wednesday 21st January
The weather front associated with a deep depression in the eastern Atlantic on Tuesday brought a wide band of rain that held off during daylight hours with the first precipitation logged at 17.40. The automatic rain gauge indicated that rain fell steadily until just before 03.00. The second half of cloud associated with that depression brought rain starting again at 06.40 on Wednesday morning. The rainfall for the past twenty-four hours amounted to 11.8mm.
The variable sunshine during Tuesday morning allowed the temperature to rise to a maximum of 8.9C at 12.43 before the cloud began to thicken, that low being 1.8C above average. During the afternoon and early evening the temperature fell away very slowly but accelerated after 21.00 as the sky began to clear behind the back edge of the weather front. That all changed as the cloud began to arrive again ahead of the next weather front that saw the thermometer make an about turn and rise again after 05.00. The minimum of 3.8C was logged at 04.13.
My 42-year record for rainfall collected in Met Office recognised 5″ copper rain gauge stands at 89.6mm. The total recorded this month is now 88.5mm, with more to follow today and over the next few days.
First light on Wednesday revealed the thick, low cloud associated with the weather front and rain falling, with a slight break just before 08.00.The barometric pressure is still falling rapidly as the deep depression edges closer to the UK with a pressure reading of 989.3mb at 08.00. Later this morning the depression will begin to move north towards Ireland and then off the west of Scotland.
The wind that has come from a southeast or south-southeasterly direction over recent days will continue until late on Saturday. It has been bringing the moist, mild Atlantic air that has been circulating around the southern area of the depression before crossing France and arriving over the UK. The cooler air is likely to arrive later on Saturday as the wind backs a few degrees to come from the east, indicating the arrival of cooler air that will continue into next week. The severity of the cooler/colder air is not yet clear, however maxima and minima are likely to drop below average for late January.
Rainfall gauges
For 42 years I have maintained the daily rainfall at my weather station using the Met Office recognised 5” copper gauge, the standard for many years, and of course before electronic automatic rain gauges were developed, which are now widespread. It was introduced in the 1940’s as a standard Meteorological Office design. The design was recommended as a standard device in the 1860’s by the British Rainfall Organisation.
My rainfall data has been, and will be, updated using that source of information to maintain my 42-year record. The minimum amount recorded in the measuring jar is 0.1mm, thus quite accurate for small amounts of precipitation.
My weather instruments, since 1984, have been read at 08.00, a standardised time for the data I send to a national weather organisation, linked to the Met Office.
My Davis automatic rain gauge has a diameter of 6.5”, which is displayed on the live feed on my website. This rain gauge is designed to meet the guidelines of the World Meteorological Organisation for accurate rainfall measurement. No data for the introduction of this type of gauge can be found. The gauge has a greater minimum measurement of 0.2mm, compared to the copper rain gauge of 0.1mm.
The data on the live feed of my website uses a different twenty-four-hour period from midnight to midnight, this sometimes will obviously show a variation between data for the previous twenty-four hours.
An automatic rain gauge has the advantage that it can be accessed remotely so doesn’t need a person to read the daily rainfall, it also has the advantage of a live read of the rate of rainfall.
I keep both sets of very useful data.