Thursday 18th December
The past twenty-four hours have once again produced a topsy-turvy day and night when the coldest time was at 08.00 on Wednesday and the warmest at 08.00 on Thursday at which time the thermometer read 10.4C. The temperature trace has shown an almost continuous slow rise. This feature was due to a cold start that then saw cloud and rain bands cross the country in the evening and overnight bringing more moist and warm air on a brisk southwesterly breeze.
There has been another modest rainfall with a daily total of 11.0mm, which has taken the monthly rainfall to 96.0mm, just above my 42-year average of 93.1mm.
Thursday has still to wake up as the sky is dominated with very low, thick, dark cloud, which is the back edge of the first rain band heading eastwards that will link up with the next rain band that is likely to produce a significant rainfall total during daylight hours.
A secondary mini-depression has recently formed off the Brest peninsula that is associated with an arc of intense rain that at 08.00 was well into Cornwall and Britanny. The radar shows an area of very angry red and yellow colours indicating intense rain heading our way. We are likely to have as much as six hours of intense rain from mid-morning.
On Sunday there is an indication of a major variation in the wind direction following an almost complete month with wind coming off the Atlantic, which brought the warm and moist air. On Sunday the projected Jet Stream flow shows a major change as it becomes more fragmented and not streaming in a continuous wide band across the Atlantic. The wind is forecast to back into a southeasterly direction that will bring a cooler air and less moist flow of air.