Now that we have swapped the long-lasting high to our east for another that has come in from the west, the weather has an altogether fresher feel – no longer are we in a stream of warm, humid air from the tropics. In fact there is almost no wind at all today, but high pressure to the west means air drawn down from the north – not warm, but clearer and drier. We are also seeing plenty of sunshine to keep daytime temperatures up, but nights are likely to be much cooler now.
Early this morning we recorded the lowest temperature so far this month, 5.4C at 0530 – it was also the coldest night (1800-0600) of the month so far with an average of 9.8C. Once the sun broke through the early mist things warmed up rapidly, and at lunchtime as I’m typing this it is a respectable 18C. Expect another cool night tonight, though – autumn has arrived.
The spell of warm, humid weather that lasted almost for the first three weeks of September has given us an average temperature so far of 16.3C – around 2C above normal for September. That may drop a little in the last week of the month, but it is still likely to be our warmest September on record. The maximum temperature so far this September is 26.2C and that is unlikely to be beaten this month, but we did see higher temperatures in September 2013 and 2011. It is the length of the warm spell that will make this month a record-breaker.
The other feature of this month is, of course, rainfall – or the lack of it. So far this September we have recorded just 7mm, with rain recorded on only two days. The driest month we have recorded here is May 2010 when the total was 12.4mm. We are three-quarters of the way through this month with only just over half that total, so a new record is certainly on the cards. However if the warm weather continues and creates some heavy convective rain, or the high pressure breaks down and allows the Atlantic to do its stuff, things could change quite quickly.
Finally, with all this high pressure, September looks likely to be our least windy month by a long way. The wind run currently stands at 92.1nm – at this point in the month a figure of well over 1,000nm would be normal, and over 2,000 wouldn’t be out of the way. The lowest wind run figure we have seen for any month is 691.6nm in October 2007, so we can see that it really has been exceptionally calm this September.
With record rainfall to start with, record high temperatures during the summer and now several records set to fall this month, 2014 is turning out to be quite a year.