Friday 12th December
Thursday was a pleasant, mild and dry day during daylight hours that meant a maximum of 10.9C was logged at 12.45, which was 3.4C above my long-term average. The warmth slipped away during the early evening with a low of 9.2C at 18.20 being 7.3C above average. The usual pattern is for the temperature to continue downwards during the night but last night the thermometer stabilised then crept upwards a little over the next two hours to reach 9.8C at 21.00 and hovered around that temperature until another slight rise after 03.00 when a temperature of 9.9C was recorded.
A narrow, fragmented rain band arrived just after 06.00 that produced just 0.6mm of light rain by 08.00. Hopefully, by late morning, the back edge of the weather front will be clearing and some sunshine might appear, which is more than can be said for yesterday.
The barometric pressure is rising steadily due to a nose or ridge of high pressure edging our way from an Azores high. This will produce a brighter afternoon and likely clear skies overnight, which will mean temperatures will drop significantly below recent nights, likely down to just above freezing. The bonus will be a dry and sunny day on Saturday.
The forecast track of the jet stream, whose position and strength as it crosses the Atlantic from America, dictates much of our weather, shows little sign of any major change well into next week and up to the weekend. As a result there is likely to be the mix of relatively mild and moist air stream with temperatures by day and night close to above average.
The rainfall total for December currently totals 65.5mm, which is 70% of my 42-year record. I noted that at 10.45 yesterday, the level of water in the River Kennet at Winterborne Monkton, registered on the Thames Water gauge close to the sources of the river, had again dropped to zero. We will need much more winter rain to fully refill the aquifers if next year the summer turns out to be drier than average.