October’s rainfall passes the 100mm mark

We are just over halfway through the month, and October’s rainfall has topped the 100mm mark. With continuing forecasts of unsettled weather this month’s total will be well above the average of around 75mm. We have had a run of wet Octobers, with totals exceeding 100mm in 2012, 2013 and now 2014.

Our year-to-date rainfall total is 797.2mm, the highest total we have seen at this point in the year, so the recent wet spell has put 2014 back in the running to be wettest year since the station was set up (the first full year of operation was 2008).

September 2014 summary

As predicted, September 2014 has turned out to be an exceptional month in several ways – for its warmth, for the absence of low pressure systems, and consequently for the lack of wind and rain.

The average temperature for the month was 16C, about 1.5C above normal and the warmest September recorded here. The previous record holder was September 2011 with 15.4C, which was helped along by a remarkable high of 26.7C. This year the maximum was 26.2C but there was a good deal more warmth spread throughout the month, so the average was higher. Incidentally, September was 0.4C warmer than August.

The average pressure for the month was 1018.8hPa which is above average but not by much – there have been other Septembers with higher average pressures. What is more interesting is that the minimum pressure recorded in September was 1006.7hPa on the 18th, which is by far our highest minimum for September. This points to the absence of low-pressure systems – high pressure dominated throughout the month, and although the systems were not intense (hence the modest average) they were persistent.

An absence of low pressure systems also means an absence of frontal rain, and nor did we see as much convective rain as we did during the summer. Hence this was by far the driest September on record here with 17.4mm – about one-third of the average for September, and the third-lowest total for any month recorded here.

Perhaps the most remarkable record to fall in September was the absence of wind. The maximum gust recorded for the whole month was 15.7kts on 1st September – the lowest maximum gust recorded here in any month – and the wind run was just 309.4nm which is less than half the previous low figure. Win run is a very variable measure, but to put last month’s total into context the average for September is 1937nm, and the overall average since the station was set up is 2088nm. We have seen only two previous months with a total under 1,000nm, but September was quite remarkably calm.

Finally, 2014 is turning out to be a record-breaking year in all sorts of ways, not least for the rainfall in the early part of the year. The very high totals in January and February, followed by some heavy spells of rain in spring and summer, meant that until now we have had a record cumulative rainfall total for 2014. September has changed that – just. Up to the end of last month we had recorded 695.8mm, but at this point in 2008 we had recorded 701.8mm so, at this stage, we are no longer heading for our wettest year ever (but there’s plenty of time yet). For those who remember 2012 as the year of the deluge – at this point we had recorded 641mm, but the high totals for the last quarter of the year made that year the record-breaker for rainfall.

A record-breaking month in prospect

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.

Becalmed.

Almost halfway through September the total rainfall for the month is 4.6mm, all of which fell on the 1st: and the average temperature is 16.1C, about 0.7C above normal for this point in the month and warmer than the average for August this year.

The last time we saw such a warm, dry start to September was in 2007 (incidentally, the first full month of operation of this weather station). In that year, the first half of September averaged 16C and we recorded just 1.4mm of rain, all on the 2nd.

It has also been remarkably calm – the total wind run so far this month is just 62.3NM, and most of that was on the 1st. In an average September we might have expected to pass the 1,000NM mark by now.

The common feature of both periods is a consistent spell of high pressure blocking Atlantic lows, but in September 2007 we had seen a wind run of 553.9NM at the halfway point – it was not nearly as calm as the last two weeks have been. In fact there isn’t another fortnight in the records here that comes anywhere near this for absence of wind.

Probably not good weather for yachtsmen or wind turbines, then, but a very pleasant start to Autumn for the rest of us.

August 2014 summary

August provided a real contrast to June and July as far as temperatures were concerned. The first two months of the summer were warm, with our highest June recorded average and second-highest for July. August 2014 produced an average temperature of 15.6C, sharing the title of coolest August with 2011.

Recorded rainfall was 94.4mm, but a fault on the weather station on 6 August means that figure is lower than it should be. The true figure is probably about 100mm, which is well above average but not unprecedented – August rainfall exceeded 100mm in 2008 and 2012.

Although a short spell of high pressure put in an appearance in the middle of the month, August was dominated by low pressure systems. The average pressure was 1011.2hPa, our second lowest August figure – the lowest was in 2008, when we also recorded 125.2mm of rain.

The remains of Hurricane Bertha passed up the Bristol Channel on 10 August, but fortunately for us this deep low pressure system hadn’t really got going when it passed – there were some gales and flooding further east. We saw a few thunderstorms, with one on the 14th producing 10.6mm of rain in 10 minutes.

While the positioning of low and high pressure areas in July often drew in warm, moist air from the south, in August we saw the opposite – a deep low pressure system passed north of the country on 18 August, and then parked itself over Scandinavia while a blocking high pressure system formed to our west. The result was a stream of polar air making it feel decidedly chilly, with a minimum of 6.1C on 21 August – in Dorset it got down to around 3C. Finally, August was quite a windy month, but there were no exceptional wind speeds.

At the end of July were heading for a record summer temperature, but August took the edge off that – the summer of 2014 has to settle for second place with an average temperature of 16.9C, against the summer of 2013 with 17.0C. The rainfall total for summer 2014 was 205.6mm (or about 211mm if we take account of the error on 6 August), which is on the high side but not exceptional.

A cool August could lose this summer its temperature record

In contrast to June and July, this August is turning out to be decidedly cool with an average temperature so far of 15.8C, about half a degree down on our normal figure and, so far, the second coolest August since the station was set up.

At 0339 today the thermometer dropped to 6.1C. If this sounds chilly for August, it isn’t actually that unusual – August 2011 saw a minimum of 5.2C, and in 2010 the minimum was 4.5C. On the other hand, we have yet to see a decent maximum temperature this month – the best we have seen so far is 23C, and every August we have recorded has managed better than that.

Our coolest August so far was in 2011, which was also our coolest summer overall – it was a singularly uninspiring season. This year is quite different, in that the current cool month follows a warm June and July – so warm that this summer is still, at the time of writing, our warmest on record with an average temperature of 17.1C. The gap is closing, though, because the average for summer 2013 was 17C. If the current run of cool weather continues and the average summer temperature drops a little further, this might turn out not to be our warmest summer after all – maybe just an equal-warmest.

Rainfall so far this month is 73.2mm, about average for the whole of August with a week and a half to go. We have seen some high August totals, though – 125.4mm in 2009 and 104mm in 2012 – so at the moment this month is nothing exceptional.

ex-Hurricane Bertha, Part II

The wind is dropping here now. Once the low pressure had passed this morning, the wind settled into the west and reached an average of around 15kts between 1400 and 1630. There were two gusts of 30kts, at 1612 and 1620.

A 30kt gust in August is unusual but we recorded a gust of the same speed in August 2009, and we saw 29.6kts in August 2012. Not quite a new record today, then, but it was the highest August gust speed for five years.  Our highest gust speed on record was 46kts in February this year.

ex-Hurricane Bertha

The low pressure system that was Hurricane Bertha passed up the Bristol Channel this morning without much drama, and the centre passed very close to us at 1030 with a minimum pressure of 990.3hPa. The barometer is now rising again, and the very gentle south-easterly breeze that we had earlier this morning is now a north-westerly and gaining a little in strength.

We have escaped most of the rain associated with this system, with only 3.4mm falling since midnight – Wales has recorded rather more. As the low moves off to the north-east we can expect the wind to pick up here later in the day.

Weather station fault – update

A check of the rain gauge this morning revealed that a spider had made its home in the gauge’s mechanism, obstructing the water flow and causing the decidedly odd rainfall measurements for yesterday and early today.  The squatter has been re-homed and the gauge is working properly again, but I reckon that the rainfall total for yesterday and today will be down by something like 5mm as a result of this little mishap.

Meanwhile, a sharp tap with a screwdriver seems to have resolved the problem with the transmitter. I’ll replace it anyway as soon as the part arrives, but at the moment it’s all systems go.

Weather station faulty

A radio transmitter in the weather station is failing intermittently and the conditions reported on the site may not be up to date. A replacement part is on the way and normal service should be resumed by the end of this week. Apologies for any inconvenience this may cause.

July 2014 summary

July will be remembered for hot, often humid, weather and thunderstorms, and it was the second warmest July on record here with an average temperature of 18.6C – a degree or so above normal but still half a degree below last year’s record-breaking July. The maximum temperature we recorded was 30.2C on the 24th, but that too was beaten by last year’s high of 31.2C. It was really just the second half of the month that was hot – the first week of July was relatively cool, and it was only towards the end of the second week that the warm weather got going.

There was a good deal of unstable weather throughout the month, with some very localised downpours. On 8 June, for example, a lunchtime thunderstorm at Weston-super-Mare, 10 miles north of this station, produced 25mm of rain in an hour while we basked in sunshine. On the same day Bournemouth was flooded by heavy rain and funnel clouds were seen in the Bristol Channel, but our total rainfall for the day was just 0.6mm.

By the middle of July we were under the influence of warm, humid air from the south. It was uncomfortably hot and sticky, with reports of thunder over much of the country. We got our turn on 19 July, starting with a thunderstorm at 0530 that brought us 9.2mm in an hour. During the day a column of thunderstorms just to our east moved steadily northwards but, although we could see the towering clouds and hear distant thunder for most of the day, there was no further significant rain until the evening.

At 1927 a very lively storm that had tracked across Dartmoor and Quantock arrived here and produced 10.6mm of rain in just 20 minutes, including 7.6mm in six minutes – one of the heaviest rainfall rates we have recorded. That deluge brought the total for the day to 22mm, more than half the month’s total of 42mm. This was the last recorded rain of the month.

By the next day the humidity had dropped appreciably, making the heat more comfortable. The following week was warm and sunny with a gentle north-easterly breeze. The north-easterly airflow was significant because it blocked the formation of a sea breeze which often keeps our temperatures in check, and from 23rd-26th July we saw daily maximum readings in the high 20s. A year-to-date high of 30.2C was recorded late on the 24th.

For the last few days of July the breeze was from the south-west, temperatures moderated and there was increasing cloud as we saw a switch to Atlantic weather systems. On the 31st there were a few drops of rain, though nothing measurable. So ended a warm and lively month.

The warmth of July has brought the average temperature so far this summer to 17.5C. If that figure is maintained during August, this could be our warmest summer since the station was set up.

Hotter still today

Ah, well – both of the year-to-date temperature records set yesterday were broken today, with a maximum of 30.2C recorded at 1706 and an average daytime (0600-1800) temperature of 24.2C.

The average temperature for this month now stands at 18.2C, which is 0.9C below the average for July last year.

Warmest day so far in 2014

As we thought might happen, this afternoon saw a new high temperature for this year with 29.6C being recorded at 1706.

It has also been the warmest day (0600-1800) so far this year, with an average temperature of 23.7C – rather an appropriate figure for the 23rd of July!

Despite the recent high temperatures, this month is not yet a match for July 2013 – the average temperature so far this month is 18C,  compared with 19.1C for last year. Probably not our warmest July ever, then, but a firm favourite for second place.