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2015-10-11_10-34-53

September 2015 Reigate weather summary

Reigate September summary weather statistics

Tmax 22.4C

Tmin 3.9C

Average temperature 13.3C

Total rain 79.8mm (CoCoRaHs)

Max gust 25mph (14 Sept)

Mean SLP 1016mb

Sunshine 132.9 hours

September in Reigate turned out to be cooler than average with rainfall amounting to around average totals mostly falling in showers so that there were relatively long dry sunny spells, especially towards the start of the month, with HIGH pressure in charge or nearby for much of the time.

It was sunnier than usual for September at over 130 hours. This was good news for Run Reigate which turned out to be a beautiful day for the runners.

Much of the September rainfall fell in heavy showers, especially in some storms mid-month.  This meant 2015 September rainfall at nearly 79.8mm turned out wetter than 2014, at a mere 22mm.  Despite this it was still just about equal to the long-term average rainfall according to MetOffice anomaly charts.

At a mean temperature of 13.4C September was slightly cooler than average and the CET came out at 1C below the long term average. Globally, September was 0.31C warmer than the long term average.

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Reigate August 2015

August Reigate Summary Statistics

  • Average temp 16.7C
  • Tmax 29.5C
  • Tmin 7.1C
  • Total rainfall 99mm
  • Sunshine 116.4 hours
  • Average pressure 1014mb
  • Max gust 29mph
  • average wind 16mph
  • dominant wind direction SOUTH

August in Reigate, like the rest of Southern and SE England, came out slightly cooler than average at nearly 17C with about twice as much rainfall than the long term average with a rainfall total of 100mm.  (Possibly* half of this fell in one deluge on 24 August when the town centre flooded quite notably from intense rain falling in a few hours (see post below)).

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South East England rainfall August 2015: 177% of long term average

Across SE England the MetOffice official records showed the rainfall total of 103mm was 177% of the August 1961-1990 long term average, so nearly double the usual total in some locations, especially near the south coast (100% being the average monthly total for August in this case). Don’t forget that August is often a wet month and that August 2014 had 84mm.  Nevertheless, if you think our Summers are getting cooler and wetter then, yes, you could well be right!  Read on to find out more.

The mean 500mb pressure pattern for August above shows a deep trough in the Atlantic, dug unusually far to the south for the time of year, and a continuation of the dominant high pressure over Europe from July, nudged further east maintaining the heat wave in Europe, especially Central Eastern Europe.  This looks like it should have promised a hot August for SE England with an average upper flow from the south and a surface mean flow from the SE. Unfortunately this pattern did not deliver any heat of note, but it did deliver occasional heavy showers and some thunderstorms, with notably torrential rain showers delivering big precipitation totals in a matter of hours.

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August 2015 heat stayed in Europe and away from UK

Despite the average southerly and SE flow bringing occasional thundery Spanish Plumes, the real heat stayed stubbornly on the continent and only fleetingly wafted temperatures exceeding 25C across the SE.  While France regularly baked in 30C+ daytime heat, Reigate and the SE could only struggle to Tmax temperatures of 25C and only once nudged 30C. Notably, the mean temperature was a tad below the 1981-2010 average but above the 1961-1990 average, showing how recent decades have been warmer.  So August was either above or below the long term average, depending on what LTA you choose. This is a small example of how weather statistics can be presented by the media to suit any argument regarding climate change.

The August monthly Central England Temperature (CET) came out at 0.1C above the long term average but this hides the cooler than average Tmax attained in a disappointing month.  This again illustrates how headline figures hide many subtle interpretations of weather statistics.  Overall, August was nearly average from the perspective of long term Central England Temperatures, with the East coming out slightly above average compared with a cooler West.  Maximum temperatures were widely lower than usual for August.

At 116.4 hours, sunshine was also only average or a tad below the 1961-1990 average.

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2015-09-05_23-09-16

sunshine duration August 2015

The dominant wind direction this August was from the SOUTH (i.e. a southerly wind).  The highest rainfall totals experienced in Reigate are brought, on our 4 year “long term average”, by southerly winds.  This makes sense because mean southerly winds are from warm source regions, travelling across Biscay and the Channel, and are frequently associated with humid warm sectors that precede fronts where heavy thundery showers can occur.

Our more frequent prevailing Westerly / SW winds bring our familiar frontal rain but this often peters out before reaching the South East as most rain is dumped over the western hills of the UK.  In contrast, warm southerly winds containing more water vapour arrive laden with precipitable water (PWAT) ripe for torrential convective downpours across Southern and SE England. The Downs (both the North and especially the South Downs) can also have a marked orographic effect enhancing this southerly rainfall pattern, whereas they have little impact on frontal rain from the west.  This warm humid southerly set-up was responsible for the Reigate deluge on 24 August, also known as a Spanish Plume.

Finally, research shows that UK Summers have got cooler and considerably wetter since 2000.  Cooler by just 0.4C (this despite some warm years) but total summer precipitation has increased by some 50mm over the last 15 years and the 10 year moving rainfall average is on the rise, most likely due to torrential rainfall events. This change to rainfall being delivered in torrential but sporadic events is in-line with climate change predictions.

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Reigate summers have got cooler and wetter since 2000

Rainfall challenge! *Our local rainfall totals are proving mighty tricky to verify at the moment.  We use three sites for measuring rainfall locally: an automatic tipping bucket rain gauge at RGS, a manual CoCoRaHs rain gauge at the same site and a local sister site in town. Unfortunately they rarely agree and sometimes vary quite considerably. Also, the manual rain gauge is used to measure monthly totals because emptying it everyday (during the holidays for example) is not always possible. Calibration of the AWS and regular rain gauge measurements is therefore an immediate target. Meanwhile, all rainfall figures are available on request and posted in these summaries along with official MetOffice rainfall figures for the South East.

Refs

https://xmetman.wordpress.com/2015/09/04/summers/

http://www.metoffice.gov.uk/climate/uk/summaries

http://www.metoffice.gov.uk/climate/uk/summaries/2015/august

2015-05-11_10-22-47

April 2015 Reigate weather chart

April in Reigate was a mostly dry, very sunny, rather calm and relatively warm month.  However, the settled weather came at a price with a significant air pollution event on 10 April. Also, April showers were conspicuous by their almost complete absence so convective weather fans were left disappointed.

Here are some April details for Reigate:

  • Tmax 14.4C
  • Tmin -1.9C
  • Average Temperature 6.8C
  • Total rainfall 23mm
  • Max gust 46mph
  • sunshine total 136 hours (sunniest April on MetOffice records!)

April was 43% drier than average across SE England and this shows up in the diminutive 23mm of rain in Reigate.  Pressure rose early in the month and so April turned out 150% sunnier and about 1C warmer than average too. The central England temperature for April came out at 1.1C above long term average.

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It was the SUNNIEST April on record for the UK according to the MetOffice.  In Reigate we enjoyed 136 hours of sunshine in April.

sunny April 2015

sunny April 2015

The significant downside of this calm weather was high AIR POLLUTION. There was a high pollution warning for a time when easterly / south easterly winds brought high levels of PM2 particles into the SE and across London from Benelux countries.

Here are some photos from Reigate during April showing what a mostly very pleasant month it was.

http://www.metoffice.gov.uk/climate/uk/summaries/2015/april

2015-01-01_14-19-40

Reigate December 2014 (2013)

  • Tmax 12.7C (11.4)
  • Tmin -2.9C (-1.9)
  • Average temp 5.3C (5.8)
  • Total rainfall 49.4mm (CoCoRaHs) (110mm)
  • Max gust 38 mph (47)
  • Total sunshine 100 hours  (92.8 hours)
  • No snow

For Reigate and the whole of SE England, December 2014 was drier, warmer and sunnier than the long-term average (1961-90), but was it less windy than December 2013?

2015-01-05_17-52-33

In Reigate and for much of Southern England a HIGH pressure moved over to create a cool calm frosty end to the year with more sunshine than usual with a total exceeding 100 hours (92 hours 2013).  Rainfall was also less than usual for December at only 49.4mm (SE Dec average 96mm).  This was despite two low pressure systems this month labelled as “bombs” in the media.  Notably there was no snowfall recorded for Reigate in December and it maintained the warmer-than average theme making 2014 the warmest year on record for England, in the longest running continuous temperature record stretching all the way back to 1772 (more on this later).

2013 was remembered for being extremely stormy for good reason as gales and rain swept the UK through the winter period causing floods and travel chaos.  However, was December 2014 really so much less windy? One storm worthy of note struck this month but the weather “bomb” on the 12 December hardly caused a stir in the SE, with most of the impact being restricted to the NW of the country. The diminutive December max wind gust in Reigate of 38 mph was caused by the non-bomb LOW that sank SE across the UK that introduced the cold final days to 2014, the so-called “arrival of the queen of freezer”!

2015-01-01_15-07-49 december 2013-14 highest av wind speed

The chart above shows the daily highest average (10 minute) wind speed for each day through December 2013 (red line) and 2014 (blue line) as measured in Reigate. The chart shows that December 2013 seems to have started less windy than 2014 but caught up and finished on a more consistently breezy note.  Nevertheless, the difference is perhaps less than might be imagined considering the stormy label given to December 2013, though of course Reigate never experienced the highest gusts nationally which were reserved for coastal areas.  Nevertheless, equally surprising is that there were 14 days when average winds exceeded 10 mph in 2014 while only 11 days exceeded 10mph in the supposedly windy 2013.  The data for 20 mph starts to show the difference between 2013 and 2014: only 1 day exceeded 20 mph in Dec 2014 while 2 days exceeded 20 mph in 2013.

The data with respect to max wind gusts also confounds the idea that Dec 2013 was windier than Dec 2014.  The average maximum wind gust in Dec 2014 was 23 mph whereas the average maximum wind gust in Dec 2013 was 22 mph, no significant difference.  Of course, this all hides the crucial MAX GUST data (peak wind gust in 24 hours): but this doesn’t help either much because there were 18 days with max gusts exceeding 20 mph in 2014 while only 15 days exceeded 20 mph in 2013.  It is left to the absolute value for maximum wind gust to distinguish the two years because it is only in this category that December 2013 markedly exceed values in 2014 with 2013 max gust being 47 mph and 2014 just 38 mph. So it is these maximum gusts that people remember and associate with “storminess” because they do the damage, even if they are only brief moments in more average wind events.  On all the other data December 2014 was windier than 2013!  This also shows, of course, how different weather data can be used to illustrate different angles on a story.

  • Max Gust 2013 47 mph
  • Max Gust 2014 38 mph

It could be concluded that the collective memory of “severe weather” is often down to a few key events that raise public awareness, more than the weather itself.  There might also be thresholds which hit the news and chime with our collective severe weather memory: flooding and snow being the obvious triggers.  December 2013 was as much to do with heavy rain as it was to do with gales, especially for the sheltered inland areas of SE England.  Rainfall this December has certainly been lower than the long term average. The chart below shows the December precipitation average as 75mm for England and Wales and just 56mm for South East England, December 2014 in Reigate is lower still at 50mm, half as much as 2013.

 

So December 2014  has been an unremarkable month for Reigate and SE England although it was nearly as windy as 2013,  but it didn’t quite hit the extremes that make headlines!

More widely December caught the imagination as freezing weather sank south across Europe and the USA where huge snowfalls were recorded in Buffalo NY and in parts of the Alps.  It snowed in Algeria while Iceland experienced balmy December days as warm as 15C.  In the SE we were stuck under a very HIGH pressure (record breaking 1044mb) that gave us the sparkling final days in 2014 with pleasant winter sunshine and some cold temperatures as low as -7C in Redhill airport.  In Reigate our lowest temperature for December of -3C shows how a town location can ameliorate extreme temperatures.  Happy New Year!

2014-10-02_20-39-59

September was a warm and unusually dry month.  Central England temperature (CET) came out officially as 15.1C which is 1.5C above the 30 year average (Hadcet) and made September the 4th warmest since 1910. In Reigate our average September temp was 16.5C, not unexpected as we are in the warmer SE of the country.  In 2013 the average for September was 14.4C but the range of temperature was greater: 2013 Tmax 30.9C and Tmin 4.6C were both more “extreme” than the respective Tmax 26.7C and Tmin 5.2C of 2014.  Whilst the remainder of Autumn looks to be cooling down markedly now, 2014 remains on target to be an exceptionally warm year overall.  Despite a cool August all the other months have been above average.

The UK average rainfall for September 2014 was 19.4mm for the month, the driest since 1910.  In Reigate we had 22mm of rain recorded (CoCoRahs) compared to over 47mm in 2013.  The rainfall we got in Reigate this September was restricted to a few heavy thundery showers: many of these moved over London and missed us completely.  However, a notable thunderstorm overnight on 19 Sept delivered some cracking thunder and lightning at about 1am and brought 10mm of rain in less than 20 minutes, and woke quite a few people up!

Overall, however, the month was dry: 16 consecutive days of no rainfall at all came early in the month and mostly dry days with just odd showers characterised the rest of the month.  Sunshine hours totalled 120 hours. Pictures below are a medley of photos from an “extreme” month due to the exceptionally dry conditions, the driest in 100 years in some places.  September in Reigate.

 

Here are some charts and figures from our Vantage Pro2 weather station summarising 2013 weather in Reigate.  All data is posted on our data page for you to download freely and use, but please credit RGSweather for any subsequently produced materials.  Excel pivot tables have been used to generate some of the more fun charts and statistics below.

Our overall conclusion from 2013 is that Reigate has some of the best weather in the UK, probably!  Read on to find out why…

Reigate Temperature

Reigate topped the charts for recording the highest temperature in the UK at times during 2013 summer.

Average temperature 9.9C

Highest Tmax 33.5C on 1 August at 4:22pm. (Heathrow recorded 34.1C)

Lowest Tmin -5.9C on 22 January at 3:37am.

Lowest wind chill -11.9C on 12 March at 5:03am.

The chart below shows daily average temperatures in Reigate throughout 2013 as a full circle.  Note the annual average temperature for Reigate (10c) is shown as a red circle.

Reigate Rainfall

Despite recent experiences, it doesn’t usually rain that much in Reigate compared to elsewhere in the UK.  The extraordinary rainfall of 23-24 Dec recorded a rare 70mm for that period on our manual rain gauge. The graph shows that this rainfall total is unsual for Reigate.

Total 654mm (VP2 rain collector; uncalibrated on site; intended calibration v soon; we suspect some under-reading of totals at this stage)

Average daily rainfall 1.8mm per day

The wettest day of the week, overall, in 2013 was… Friday (but not significantly) with Thursday being a significant driest day.

Highest rainfall intensity 182mm/hr (briefly!) on 22 November at 8.38am.

Reigate Wind

The strongest gust recorded in 2013 was 48mph, more exposed hills and places locally recorded 60-70mph (e.g. Redhill aerodrome).  Reigate is sheltered from Northerly winds by Reigate Hill and from more common gales from the South or SW by high ground at Priory Park and woodlands.

Average highest daily wind speed  8.7mph

Max gust 48mph from WSW on 28 October at 6:15am

Dominant wind direction WSW.

The windiest months were October and December in respect of highest maximum wind gusts measured.

Wind run is a measurement of how much wind has passed a given point over a period of time. A wind blowing at three miles per hour for an entire hour would give a wind run of three miles.  Wind run is a measure of the persistence and duration of a particular wind direction.  The longest wind runs for Reigate in 2013 were associated with NE winds in March, which were persistent.  The fateful Channel Blizzard wind run that met warm SW winds and caused such unusual snowfall in the Channel Islands recorded the longest wind run of 267 miles. It’s interesting to note that our most common westerly and SW winds achieve relatively short wind runs, this is probably because our prevailing winds are associated with LOW pressure systems that cause rapid changes in wind direction as they pass through.

Rain and Wind

Most of the heaviest rainfall totals for Reigate in 2013 arrived on South (S) and West-South-West (WSW) winds.  The wind direction bringing highest average rainfall intensity (rainfall rate mm/hr) in 2013 was SSW.  There looks to be a strong correlation between rainfall rate and wind speed.  The chart shows that the heaviest rain tends to occur at lower wind speeds.  The strongest gales it seems often just precede, or arrive soon after, warm or cold fronts, prior to arrival of or just after the heaviest rain has passed.  This was certainly the case in the October StJude storm when the, now infamous, stingjet winds followed after the heaviest rain on the cold front had well and truly passed through Reigate.

Wind and Temperature

The wind direction bringing coldest temperatures to Reigate in 2013 were those bitter Easterlies in our cold 2013 Spring.  An interesting element of SSW winds also brought in cold minimum temperatures to Reigate, possibly ahead of fronts from the Atlantic when chilly continental air can be dragged in as “polar returning air” from a frigid winter continent.  Interestingly, the dominant wind bearing bringing the lowest wind CHILL temperatures was NNE, different from the winds bringing lowest average air temperature.  More on wind chill here 

Reigate Sunshine (*sunshine recorder added April 27)

Sunshine total hours *1058 hours (from April 27)

Longest daily sunshine hours 11.4 hours June 6

Shortest daily sunshine within recording period 0 hours on 21 December (shortest day)

In conclusion: Reigate, Surrey has the best weather in the UK, probably!  It is one of the driest, least windy, least stormy (we get few thunderstorms compared with many places) and sunniest and warmest places in the country.  Reigate was one of the warmest or nearly-warmest places in the UK a number of times in 2013.

Some factors making Reigate weather some of the best in the country are to do with the uniquely well-placed location of the town.  So, thanks to the Normans we are:

  • south facing: nestled at the foot of the North Downs: sheltered from cold Northerly and NE wind and rain
  • sheltered from S and SW gales by Priory hill and woods.
  • low altitude: 100m above sea level: not exposed.
  • inland from exposed coasts which experience higher winds and, sometimes, more rain
  • on the lowland East of the UK: enjoying a regionally sheltered location from cold easterly winds (Kent gets these) and westerly gales and heavy rainfall.
  • in a location that usually avoids extreme convective thundery activity (2013): Reigate missed several thunderstorm events that passed to the north of London from a SW direction; this may or may not be usual.
thunder monday

Reigate missed the big 2013 thunderstorms which often drifted from SW to NE in lines of convective activity, missing the SE

We plan to post full meta-data describing the location of our Vantage Pro and the data required to get the most our of our records in 2014. Other plans for 2014 include:

  • Calibrate the tipping bucket VP2 rain gauge before Easter.
  • Further outreach to other schools and interested parties regarding all-things weather, via this blog and @RGSweather.
  • Expand the school club and further engage students in the wonders of weather.
  • Expand the use of data in school to include more departments.
  • Provide a local service to help forecast and understand extreme weather, when we can, via Twitter.
  • Engage with the Press and media where we can provide useful information
  • Encourage readers to post comments and together contribute to the wider understanding of weather locally.

A sincere thank you to all readers for making this such a success in 2013 and please come back for more in 2014!