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2016-07-22_15-53-56

Reigate June 2016 weather statistics

  • T average 16C
  • Tmax 25.6C
  • Tmin 8.5C
  • Total rainfall 100mm
  • Max gust 28mph
  • total sunshine 114 hours

June 2016 was wet in Surrey with over 246% of normal rainfall.  SE England as a whole received 113mm of rain, 208% of long term average.  At 118.4mm, Surrey was the wettest county in the UK regarding anomalously high precipitation. Despite this, both 1971 and 2012 were wetter months.

The rain was delivered in a number of distinct heavy showers and convective thunderstorm events, notably on 23 June when parts of South London were especially badly flooded in flash flooding during torrential rainfall of more than 50mm in one storm.

http://www.huffingtonpost.co.uk/entry/uk-weather-flood-warnings-as-torrential-rain-falls-on-london_uk_576b9225e4b0b1f1704feabb?7liv7jj9ylkz3q5mi&

The heaviest rainfall was characteristically patchy so not every part of Surrey experienced the same soaking, some parts were a lot wetter than others. For example, while Caterham received over 40mm in one thunderstorm, Reigate received only 10mm from the same storm.  In total, Reigate received 100mm of rain in June which compares with 15mm for June 2015 and 30mm for 2014.

“Surrey with 118.4mm of rain endured the worst rainfall of any county, relative to its average. The June average rainfall for Surrey between 1981 and 2010 is just 50.7mm. This month’s total was 246% of normal.” MetOffice

A thunderstorm on 23 June brought an amber warning and local flooding and lightning damage to some places in the SE. Below are some news reports from the time.

A shelf cloud was spotted over Reigate, one of the first observed over the town.

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Horsham experienced intense lightning and one bolt struck a conifer at 2am which was destroyed in a spectacular explosion.  Fortunately no one was hurt, but cars and property was damaged.

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convective June 2016 Priory Park

June started well but pressure fell from 10 June and the month remained mostly unsettled thereafter.

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Due to the unsettled conditions and rainfall and associated cloud, June was less sunny than usual, with only 114 hours of sunshine recorded in Reigate. June 2015 had 192 hours of sunshine in comparison.

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June was just about 1C above the long term 1981-2010 UK average at 13.9C.  Reigate recorded a monthly average of 16C which is considerably higher than the UK average being located in the warmer SE.

Globally June 2016 was the warmest June since records began in 1880 and was the 14th month in a row to beat global long term average temperature. The charts below show NOAA, NASA and UAH global temp anomaly maps for June. All agree that June was hot.

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With one month after another breaking heat records, 2016 is easily on target to be the hottest year on record despite a waning El Nino.

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This continues the inexorable rise in global temperature in recent years.

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2016-06-12_06-35-12

Reigate May 2016 summary statistics

  • Tmax 27.4C
  • Tmin 0.3C
  • Tav 13.8C (UK 11.3C)
  • total rainfall 42mm (town) 45mm (Hartswood)
  • max gust 36mph
  • average wind direction NNE
  • sunshine 181.7 hours (May 2015 161 hours)

Whilst there were fortunately no severe weather events in Reigate and few across the UK in May, the weather we experienced more widely could be linked tenuously to climate change.  Of course, caution is required with such speculative statements but attribution studies on the May floods in Paris, not so far away, have concluded that they were made 90% more likely due to climate change. The same stalled low pressure system delivered our easterly winds so we were influenced, albeit on the edges, by the same blocked weather pattern.

People attempting to climb Snowdon in North Wales in May were lucky to experience sunnier-than-usual conditions for much of the month (south wales had more thunderstorms which reduced the sunshine totals there).  Meanwhile, in Surrey, we experienced occasionally warm conditions with an unusual mean monthly wind direction from the NNE.

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Reigate pressure rose hesitantly mid-month

Pressure fell across the UK to start May but then rose mid-month, especially to the North, bringing a relatively unusual easterly flow into Reigate and the south.  Whilst there were few severe weather events during the month, this post briefly explores some of the wider factors that may have contributed to this Easterly flow and the possibility of it being linked to climate change.

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Whilst mostly dry for the UK as a whole, occasional showers, some thundery, brought Reigate rainfall totals to just above average at around 42-45mm as recorded from our two weather stations respectively in and out of town.  SE England as a whole recorded rainfall at 111% of normal rainfall, mostly falling in thundery showers, more common in SE wind regimes.

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With relatively dry Easterly winds, sunshine totals for the UK were accordingly above average given the relatively high pressure overall.  Reigate experienced 182 hours of sunshine in total for the month.

Unusually, the sunniest places in the UK were in the North and West given the easterly winds bringing occasionally cloudier conditions off the North Sea to the south and east.  May 24 shows a typical scenario with the higher pressure to the North dragging in E/NE winds across the southern part of the UK with cloud across eastern areas and clearer conditions to the west.

Some great sunny days were recorded in the mountains of Wales, Cumbria and Scotland!

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Sunny Snowdonia with kelvin-helmholtz type wave clouds trying to form over Ogwen Valley

The higher than average rainfall patches shown below in the south were associated with showers on occasionally unstable warm and humid SE winds.  Reigate reached a Tmax of over 27C in this warm flow.

The wider pressure pattern across the northern hemisphere was characterized by anomalously high heights over the Arctic and LOWER than normal pressure in mid-latitudes including Europe. This situation is called “northern blocking” and in winter could cause cold conditions in mid-latitudes.  In Spring, as the continent rapidly warms up in stronger sunshine, easterly winds can be warm or even hot for the UK.

northern blocking over Pole

northern blocking over Pole

Northern Hemisphere pressure patterns are measured by the Arctic Oscillation which, as can be seen below, remained unusually negative through much of April and May showing high pressure persisting over the Arctic relative to low pressure in the mid-latitudes.  This pressure pattern turned winds from the usual westerlies into easterlies in the UK and Europe.

negative arctic oscillation Spring 2016

negative arctic oscillation Spring 2016

The causes of this reversal of the usual mid-latitude zonal westerly wind set-up have been linked to low sea ice extent in the Arctic, especially the Kara and Arctic Gateway seas. Warmer influxes of air into the Arctic builds air pressure which then links to higher chances of Easterly winds in mid-latitudes.

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low Arctic sea ice cover March 2016

The very low sea ice extent this year was brought about by much warmer-than-usual conditions during the Polar winter, where monthly average temperatures in the Arctic (>60N) were at times 3.5C or more above average during the cold season of 2015-16. This Arctic amplification is widely accepted as being caused by human induced climate change.

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It turns out that Spring Arctic sea ice extent is some of the lowest recorded in the 38 year satellite series.

 

So, unusual sunshine in North Wales, a warm NNE mean wind direction in Reigate and cloudy conditions on the east coast can be linked to the above tele-connecting weather patterns which, in turn, can be linked to climate change in the far flung Arctic.

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Meanwhile, the strong 2015-16 El Niño declined rapidly through May and ENSO conditions were neutral by early June. Models suggest the chance of La Niña (cool Pacific) conditions by Autumn 2016 are as high as 60%.  Some forecasters bring La Nina through the summer.  La Nina, and the warmer SSTs of the tropical Atlantic, are associated with more frequent hurricanes in the Atlantic basin.  In turn, high hurricane accumulated energy transfered to the North Pole during such seasons can build Polar heights in Northern Hemisphere winters, warming the Arctic and further melting sea ice.  Whilst this is just outrageous long term amateur speculation, it is nevertheless interesting to ponder the potential for feedbacks to accelerate further climate change in the near future.

The turning down of the vast heat engine of the El Nino might be linked to the slightly lower May global average temperature, though confirmation from expert sources has not verified this as yet.

 

Local data for May and all months stretching back to 2012 can be found on our data page here

http://www.metoffice.gov.uk/climate/uk/summaries/2016/may

 

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How can there possibly be a link between a modestly cool month in Reigate and the earliest start to the melt-season in Greenland, the devastating wild fires in Canada and the seventh hottest-ever global month in succession?

April summary weather statistics for Reigate

  • Average Temp 8.2C
  • Tmax 17.7C
  • Tmin 0.1C
  • precipitation 43.4mm (local Reigate) SE PPT 55mm
  • sunshine 140.4 hours
  • Max wind gust 30mph
  • average wind bearing 199 degrees

Reigate, like the UK as a whole, had a cooler than average April at 8.2C. The town even experienced some unusual snow showers on 26 April in a cool northerly air flow.

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The cool month for the UK is in stark contrast to the bulk of the planet which experienced a much much warmer month than average, at over 1.1C warmer than any previously measured April.

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Astonishingly, this is the seventh month straight that has brought record breaking global temperature anomalies.  This continuing succession of warm months globally should be of concern to everyone.  More on this below.

Back to the UK… The Central England Temperature came out at 7.5C,  0.4C below average, and the UK mean was even lower at 6.5C, 0.9C below the long term average.

Rainfall was about average in Reigate with around 40mm of rainfall.  The MetOffice SE figure came out at 55mm.

April was sunnier than usual with a total of 140 hours of sunshine.

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This continues the trend of drier and sunnier Aprils in the UK in recent years.

The first half of April was unsettled with most of the rain falling associated with low pressure systems and fronts. The second half of April saw an unusual cool period as northern blocking over the Arctic sent cool northerly winds south with attendant sunshine and showers.

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Globally April was the warmest ever April on record.  An anomaly of 1.1C sent the Paris target of keeping global temperatures below 1.5C into grave doubt as this is the 7th month in succession to yield much higher temperatures than ever. This is now being dubbed a “Climate Emergency” because of the sudden and rapid increase in global temperature to levels not expected to occur so soon.

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The UK / NW Europe was about the only part of the planet, with NE Canada, to record below average temperatures.

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The cool spot over the UK  was due to northern blocking (high pressure) over the Arctic. As pressure rose over the Arctic, cold air pushed out into mid-latitudes.

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It is a matter of chance where high pressure and low pressure set up that determines where cold polar air penetrates in these northern blocking scenarios.  This time the pattern sent the cold air to the UK and N Europe.  The Northern Hemisphere as a whole saw anomalously low snow cover as a result of incredibly high temperatures elsewhere.

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Arctic Amplification, where the northern latitudes experience highest rates of warming, is well documented and of increasing concern to climate change.  It is acting as both a response and a further driving force behind rapid climate change.

Temperatures rocketed over the Arctic this cold season with temperature departures over 3C widely across the Polar regions.  The Greenland ice sheet experienced one of the earliest starts to the ice melt season on record.

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Arctic Sea cover also recorded another record low maximum winter extent.

“On March 24, Arctic sea ice extent peaked at 5.607 million square miles (14.52 million square kilometers), a new record low winter maximum extent in the satellite record that started in 1979. It is slightly smaller than the previous record low maximum extent of 5.612 million square miles (14.54 million square kilometers) that occurred last year. The 13 smallest maximum extents on the satellite record have happened in the last 13 years.” NASA 

This is both a response and a further catastrophe for climate change.  As snow and ice melt in the Polar regions there are connections with further warming as darker sea and land surfaces heat up more readily.

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This Polar warming itself is connected with a weaker jetstream as latitudinal temperature gradients in the atmosphere decline.  It is temperature gradient, especially in Mid-Latitudes, that generates the driving force behind the jetstream.  A weaker jetstream is said to cause more blocked atmospheric conditions as it meanders with greater amplitude in a meridional pattern that locks in swoops of northerly and southerly winds. More extreme weather is caused as these pressure patterns persist for longer.  Sweeps of warmer air penetrate into the Arctic, melting more ice over Greenland and, for mid-latitudes, cooler dry Polar air leaks out causing damaging late frosts and wild fires.

So, whilst it seems tenuous to connect these far-off events to our own rather benignly cool April, it is still important to think globally when considering how our own weather links to increasingly extreme weather elsewhere.

http://www.theguardian.com/environment/2016/may/16/april-third-month-in-row-to-break-global-temperature-records?CMP=share_btn_tw

http://www.bbc.co.uk/news/science-environment-36212145

2016-03-12_13-32-30

February 2016 weather statistics for Reigate, Surrey, England.

  • Tmax 13C
  • Tmin -3C
  • T Average 5.3C
  • Rainfall total (CoCoRaHs) 48.2mm
  • Sunshine 99.6hours
  • Average MSLP 1010mb
  • rain days 18

Feb CET 4.9C (anomaly +1.1C)

Mean UK temp 3.9C

Storm Henry opened February weather with inclement wet windy conditions for the far NW but no significant impact here in the SE.

Storm Imogen on the 8 Feb impacted Wales and the SE more with the highest gusts of the month exceeding 41mph here in Reigate, with a max gust of 81mph on the Needles, Isle of Wight.

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February was another mild winter month, though not on the scale of record breaking December 2015.  February UK average was 3.9C, the Central England temperature (CET) for Feb was 4.9C, an anomaly +1.1C above the long term average. Locally our February average was 5.3C showing that the SE was warmer than the rest of the UK.

February was the sunniest winter month with nearly 100 hours of sunshine, compared to 94 hours in January and a dull 80 hours in December.

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The mean 500mb heights for the month (above) shows a trough placed over the UK for much of February and an overall Atlantic flow bringing milder than average temperatures, mainly to the south and SE. The continent was even warmer with some anomalous temperatures exceeding 10C in E Europe and Russia.

Rainfall for February was about average for the month at 48.2mm, similar to the MetOffice official SE England precipitation figure of 49mm.

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Global mean temperatures turned out warm again for February, in fact 0.47C warmer than the previous record.

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stratospheric warming February 2016

A notable atmospheric event that went mostly unnoticed at the surface was a significant stratospheric warming in February (and March).  The sudden warming of temperatures high in the stratosphere, much anticipated by the weather community and long range forecasters as a key tool to forecast winter conditions in the Northern Hemisphere, came too late to cause much cold winter weather in Europe.  El Nino winters are often accompanied by Sudden Stratospheric Warmings (SSW) events in late winter.  Such events can cause cold weather in mid latitudes as pressure eventually rises in the troposphere some 2 weeks after a SSW.  The warming during an SSW is truly remarkable, with temperature rises exceeding 80C in a matter of days at 10hPa (30km), from -80C to +10C in some SSW events.

An SSW is like inflating a balloon in the high atmosphere, pressure is expected to propagate down and eventually rise in the lower atmosphere some weeks after an SSW. Importantly, the pressure rise often disrupts the zonal westerly flow of the jetstream.  This appears as negative anomalies on the zonal wind chart below (blue colours). Unfortunately for this winter, the SSW came too late for much significant winter cold to penetrate into Europe.  You can spot that the anomalous easterly winds only got going in March… too late for deep cold to push into Europe.

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The JMA snow charts below also show how February came out as an anomalously un-snowy period for much of Europe.

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http://www.metoffice.gov.uk/climate/uk/summaries/2016/february

 

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Reigate, Surrey January 2016 summary weather statistics

  • Tmax 12.8C
  • Tmin -5.1C
  • T av 5.2C
  • Total rain 137.2mm
  • sunshine hours 94.1 hours
  • mean pressure  1009mb
  • max gust 35mph

January 2016 was a modestly unsettled month in Reigate with frequent wet days (21 in total with >1mm) and total rainfall amounting to 137.2 mm, this was some 160% of normal expected rainfall totals for the SE as a whole for January.  This caused some surface water flooding and soggy fields but, whilst a few flood alerts were issued, the River Mole behaved itself as no one rainfall event occurred with sufficient intensity to cause significant flooding problems in the Mole catchment.

In comparison with recent years, January 2016 turned out moderately wet sitting between the very wet January 2014 183 mm and the drier Jan 2015 69mm.  Of note locally was a spectacular display of mammatus cloud on 10 January as a squall line brought a thundery trough that passed over the area bringing some hail and cumulonimbus cloud.

It was a mild month with average temps 5.2C, Tmax 12.8C and only 7 days with minimum temperatures dipping to or below freezing. The highest January max temp ever recorded occurred in N Ireland. Whilst no weather record was broken in Reigate it was still a mild month with about average sunshine.

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sunshine Reigate January 2016

At 5.4C the CET temperature for the UK was 1.6C above the long term average. At 1.13C the global average January temperature turned out to be another record breaking warm month.

Returning to local events, one brief marginal wet snowfall event occurred in Reigate and Surrey overnight 16-17 January.

Snow lay during the morning of 17 January and was just sufficient to allow families to enjoy sledging and snowman building in Reigate and Priory Park for a few hours before it all melted by midday.

 

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The mean 500mb pressure anomaly pattern for January shows the UK in a mostly stormy Atlantic regime with storms rattling through especially the NW bringing high rainfall totals there. Storm Gertrude at the end of the month did not impact the sheltered SE much. As usual the SE was relatively protected sitting nearer the higher pressure over S Europe.

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Reigate December 2015 summary statistics:

  • Tmax 15.5C
  • Tmin 1.6C
  • Average temperature 10.1C warmest on record (2014 5.3C)
  • Total rainfall 79mm
  • max gust 37mph
  • sunshine 79.8 hours

Like the rest of England and Wales, Reigate had an exceptionally warm December and the warmest on record by a huge margin.

Central England Temperature December records smashed!

2015 warmest December CET ever recorded: 9.7C
December 1934, 1974: 8.1C

This is warmer than any March CET.
Warmer than any November barring 1994
There have been 171 colder Octobers
There have been 26 warmer Aprils
There have been 34 cooler Mays

The CET mean minimum was higher than any April mean minimum ever recorded.  It was higher than the May’s CET minimum

The gap between September and December’s CET was less than 3.0C, the gap between their respective minima was just 1.1C!

The CET mean maximum was 1.8C higher than the previous record of 1974.

(source CET data from UKWW)

In Reigate the average temperature was 10.1C compared to 5.3C, 5.8C and 6C in 2014, 2013 and 2012 respectively.  Whilst our own Reigate records only go back to 2012 (neighbour stations extend this locally back further to 2009), the Central England Temperature record extends back to 1772 and, at 9.8C monthly average, December 2015 smashed all previous mean monthly temperatures by a long way. The official Central England Temperature anomaly (temperature departure from normal long term average) came out at a whopping  5.2C above average, way above previous warm Decembers of 1934 and 1974.

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The chart above shows the monthly average data in Reigate this year as an anomaly departure from the long term average for SE England – (source MetOffice Hadobs 1910-present).  It starkly shows how much warmer December was from the long term average extending back to 1910, Reigate was a full 5.6C above normal!  How much is this down to El Nino? As discussed in previous posts the El Nino ENSO Pacific warming natural cycle cannot explain all of this extraordinary warmth.  In fact, there is little established link between El Nino and UK winter weather.  This is shown in the charts below for previous mega-El Ninos in 1982 and 1997 which had markedly different impacts on our December winter weather.  So there appears to be no real solid link between El Ninos and any crazy warm winter / December weather here.

Remember that the recent Paris climate change conference has sought to set a target of limiting global temperature rise to no more than 2C temperature increase over pre-industrial levels.  Locally we can expect spikes in temperature of course but this 5C anomaly for December, and the fact that 2015 will certainly be the warmest on record globally, shows the huge challenge that lies ahead in keeping temperatures down to less than 2C globally.

It was so warm for so long that wild flowers and plants around Reigate such as daffodils, camelias, forsythia and rhododendrons came into flower as if it was Spring.  This was a lot to do with minimum temperatures being so high with no frosts recorded at all.

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Many records were broken across the UK for highest minimums overnight, which frequently stayed in double figures. Indeed, this December has had a similar mean temperature to that expected in May. Our own station recorded the highest December Tmax at 15.5C on 19 December and the highest overnight Tmin at 12.4C on 26 Dec.2016-01-01_15-28-59

Despite the record breaking deluge further North which made this the UK’s wettest December of record overall), rainfall in Reigate came out around or even a tad below average at 79mm.

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Whilst 2014 was drier still at only 49.4mm, 2013 saw 110mm.  Regionally, South East England got around the average rainfall normally expected in December.  Like November 2015, December continued the sun-less theme with only 79.8 hours of sunshine.

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Apart from the incredible and perturbing warmth (which extended to the North Pole at the end of the month courtesy of Storm Frank) December 2015 was not remarkable for much else weatherwise locally.   Unfortunately, in Cumbria, Yorkshire and North Wales, there was extensive flooding which caused much misery and disruption especially over the Christmas period.  For more on the flooding and other weather stories please check this Flipboard magazine account.

Have a Happy New Year!  Data for Reigate and 2015 has been updated in the data page. 

http://www.metoffice.gov.uk/news/releases/archive/2015/early-dec-stats?WT.mc_id=Twitter_News_Pressrelease

http://www.getreading.co.uk/news/reading-berkshire-news/december-breaks-warm-weather-records-10673765

http://www.independent.co.uk/environment/uk-weather-why-the-recent-devastating-floods-will-become-the-new-normal-a6793291.html

https://xmetman.wordpress.com/2016/01/01/phenomenal-december-of-2015/

https://wansteadmeteo.wordpress.com/2016/01/01/december-2015-exceptionally-mild/

http://www.carbonbrief.org/analysis-how-december-2015-topped-chart-as-uks-wettest-month-on-record?utm_content=bufferf8440&utm_medium=social&utm_source=twitter.com&utm_campaign=buffer

http://www.metoffice.gov.uk/news/releases/archive/2016/december-records

http://blog.metoffice.gov.uk/2015/12/31/whats-been-happening-to-our-weather/

2015-12-13_12-13-56

November 2015 statistics for Reigate, Surrey

  • Temperature average 10C
  • Tmax 16.3C
  • Tmin -2.6C
  • Rainfall 66mm
  • Max gust 40mph
  • Sunshine 69 hours

In the UK November 2015 was the third warmest on record since 1910 and averaged 10C in Reigate with Tmax 16.3C and Tmin -2.6C.  The overall CET (Central England Temp) for November came out at 9.5C, nearly 3C above the long term average.

The month started with a trough in the Atlantic and HIGH pressure to the east bringing a mild wet southerly //SW flow to our area in the south.

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November 2015 mild SW flow

Rainfall was about average for our area at a total of 66mm for the month, though this is significantly drier than the MetOffice SE data shown below which shows the SE being wetter than average as a whole.

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South East rainfall Nov 2015

A number of named MetOffice storms impacted the UK but did not significantly affect the SE.  Ex-Tropical storm Kate swept unnoticed across the South on the 14/15 Nov and brought some blustery weather to the Downs.

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Pressure and wind gusts Reigate November 2015

Temperatures took a brief dip later in the month when a short-lived Arctic plunge brought brief wet snow which fell and settled momentarily in Reigate on the morning of 21 November.

November rain was about average for Reigate, though wetter in the NW.

November was the dullest ever on record especially here in the south.

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Some other pics of Reigate during November

Here is the MetOffice summary and blog records for the month

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

http://blog.metoffice.gov.uk/2015/11/

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Reigate July 2015 statistics

  • Average temperature 17.4C
  • Tmax 35.1C
  • Tmin 7.4C
  • Total rainfall 51mm
  • Max gust 27mph
  • Sunshine  161 hours

July 2015 in Reigate started hot, reaching 35.1C on July 1st due to a Spanish Plume.  The first day of July broke the record for the hottest July day when Heathrow spiked at 36.7C as cloud cleared around the airport allowing sunshine to heat the surface through an already very warm airmass.  This caused a heat spike at Heathrow and elsewhere that allowed the MetOffice to announce 1 July 2015 as the “hottest July day since records began and the hottest day since 2003”.  This set climate / weather data skeptics in a whirl as they spotted that the nearby Kew Gardens weather station did not correlate with the same heat spike at the same time allowing them to claim it was simply due to hotter local conditions from the local airport tarmac, a change of wind direction or even heat from a passing plane.

The photos below show the locations of the Heathrow weather station adjacent to the Northern Perimeter Road west and the Kew Gardens weather station.

In response to the doubt, Mark McCarthy, a climate scientist at the metoffice, was quoted in this article explaining that the heat spike was neither due to passing aircraft, nor a change of wind direction or any micro-climatic influence from tarmac and that the temperatures from Heathrow are representative and so the record stands.  In discussion with RGSweather on twitter, Mark also explained that the last 10 years of daily Tmax observations from Kew Gardens and Heathrow differ only by <0.03C on average.  This debate was akin to the wider global warming debate where met agencies present data that is then questioned by skeptics who present data that appears to contradict the claim. In any case, July 2015 started hot!  Unfortunately, July temperatures then promptly collapsed across the UK and the CET came out around average as westerlies returned from an anomalously cold North Atlantic.  Despite a lack-lustre July in the UK, globally, July turned out as the hottest month ever recorded.

Reigate and the SE had an average month being just nearer the European heatwave that dominated July.  Overall the monthly temperature came out a tad below the CET long term average, continuing a run of 3 cool months.  Further north and west July became a decidedly cool wash-out, especially in Scotland where snowfall occurred over some mountains.  Night time minimums were cooler than usual and some records were broken for lowest ever July night time minima.  In Reigate we recorded a Tmin of just 7.4C at the end of the month.

Here are metoffice anomaly charts showing how Reigate and the SE stayed warmer and drier than elsewhere.

SE rainfall overall came out above average mainly due to thunderstorms delivering locally heavy precipitation.  Reigate at 51mm came out nearer average because most heavy rain missed us. Although not local to our area, a thunderstorm over the Brecon Beacons in early July killed two people on top of Pen Y Fan and Cribyn.  The photo below shows this thunderstorm.

Globally, NOAA and JMA (Japanese met agency) reported that July 2015 was the hottest month ever recorded.

More from the metoffice on JUly 2015 here: http://www.metoffice.gov.uk/climate/uk/summaries/2015/july

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June 2015 Reigate summary

June in Reigate, Surrey continued the Summer 2015 theme of mostly cool, dry and sunny but with an unsettled start and THREE attempts at continental heat from Spanish Plumes in one month. (please note that the chart above hugely exaggerates the rainfall.. check the rain scale in mm.  I have yet to fix down the scales month on month!). 

  • Average Temperature  15.7C
  • Tmax 30.6C (25.6)
  • Tmin 5.5C (6.2)
  • Total rainfall 15mm (30)
  • sunshine 192 hours (175)
  • max gust 28mph

(Figures in brackets are from June 2014)

The month started unsettled with a deep low pressure 976mb crossing Scotland from a very much cooler-than-usual North Atlantic bringing brisk winds for the time of year and comparatively cool temperatures.  Another Atlantic LOW crossed Scotland through the first week 991mb (see satpic).

A weak first attempt at a Spanish Plume 5-6 June developed ahead of an Atlantic cold front and gave some limited thundery activity early morning on 5 June, these cells went on to become more significant further north east over E Anglia.

Pressure rose thereafter as an anticyclone built firmly over the UK.   This HIGH eventually slipped north and a heat LOW from Iberia brought the threat of a second Spanish Plume around 12-13 June.  This misfired and caused little convective activity over Reigate at least.  This turned out to be a significant mis-fire for convective forecasters, despite some limited activity here and there the overall level of activity was low and certainly nothing occured over Reigate except very late in the day when some congestus puffed up.

2015-07-09_11-19-46

Spanish Plume mis-fired 12 June 2015

High pressure built again with weak fronts skirting across the SE bringing some pleasant mid-level and upper level cloud, nice sunrise and sunsets and some good atmospheric optical phenomenon at times.

Towards the end of June a third attempt at a Spanish Plume yielded more heat and more purposeful thundery activity that eventually spilled over into decent thunderstorms into the start of July.  This was a modified Spanish Plume and more details can be found on the post written up here and here.

The end of June 2015 heat spike produced some 30C+ temperatures and in Reigate 30.6C was recorded on 30 June.  Overall the month was sunny but a shade cooler than average according to the CET central england temperature record.

2015-07-09_11-27-25

The UK anomaly charts reflect the overall dry pattern with notably little rainfall for the month.  In Reigate the total rainfall measured was 15mm.

Although this June was not consistently hot tp push up the CET (central england temp), we did nevertheless have episodes of unusual heat, especially at the end of the month with the end of June / early July heat spike.  This heat wave was more severe and prolonged in Europe.  A “cause” of the Euro heat wave, with significant heat in Spain and Portugal, was an OMEGA BLOCK or “shruggie”  that built through June and lasted into early July.  This Omega Block pattern may also be linked to rapid melting of the Greenland icecap that has been recently reported as heat builds there under high surface pressure.

A weather pattern that resembles an atmospheric version of the shruggie — ¯\_(ツ)_/¯ — is directing furnace-like heat toward Spain, France and England on Wednesday, with high temperatures near 40 degrees Celsius, or 104 degrees Fahrenheit, as far north as Paris.

The heat wave is also affecting southern parts of England, with temperatures in the upper 30s Celsius, or mid-to-high 90s Fahrenheit. Those temperatures on Wednesday were the warmest recorded in the UK in at least nine years, according to the UK Met Office.

Andrew Freeman, Mashable 1 July 2015

heat wave / mini!

heat wave / mini! south east England Surrey

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

http://www.climatecentral.org/news/maps-greenlands-melt-season-19196

http://mashable.com/2015/07/01/england-france-spain-heat-wave/

2015-06-07_11-16-50

May weather summary Reigate Surrey SE England

May 2015 summary data for Reigate

  • Average temp 12.1C
  • Tmax 20.7C
  • Tmin 4.1C
  • Total rainfall 62.7mm (CoCoRahs manual rain guage)
  • average wind speed 21mph
  • Max gust 38mph
  • total sunshine 161.2 hours

At 12C the May average temperature in Reigate was a tad cooler than long term average, as it was for the whole of the UK at a mere 9.6C, (0.4C below the long term average for the SE).  May was the first month since August 2014 to be below CET long term average. The chart below shows the mean monthly 500mb geopotential height for May and shows a big LOW to the NW of the UK.  This pattern would generally cause a cooler than average W/NW flow across the UK, especially the northern part of the country.

2015-06-07_16-24-04

May mean monthly 500mb geopotential height reanalysis

The culprit causing the slightly cool / unsettled May was a LOW pressure in the Atlantic to the N/NW of the UK that caused a NW airflow which also reduced sunshine hours below average, at 161 hours.

May rainfall in Reigate was 53mm.  Frontal rainfall from occluding Atlantic LOWS brought rain early in the month when it was quite windy too, with max gusts over 35mph on May 6-7.  Sunshine totals were low during the first half of the month but picked up mid month and later.

A trough disruption May 13-15 caused a particularly wet 24 hours 13-14 May.  Trough disruptions are notorious for causing unpredictable weather events, including causing poor model forecasts for rainfall.   The charts below show the trough disruption progress.

2015-05-14_16-57-19

trough disruption May 14 2015

The satellite picture below shows the LOW resulting from the disrupted trough and the band of cloud associated with the fronts.  In Reigate this single event caused the highest daily rainfall total for May, at over 15mm (CoCoRahs manual rain gauge).

occluding LOW May 2015

occluding LOW from trough disruption 14 May 2015

A thundery event occurred on 19 May and brought heavy showers across the SE.  Here is the synoptic chart for that occasion.

Some impressive mammatus clouds were spotted locally as the cumulonimbus clouds moved away.

More details here from MetOffice

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