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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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Currently Reigate and the SE is enjoying a settled sunny spell under the continental flow of a HIGH pressure sat directly over the UK.

Light surface easterly/SE winds and unbroken sunny skies under high pressure have brought temperatures up to 17C locally today.

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The 500mb chart above shows the upper southerly / SE flow bringing recently warm conditions in the daytime.  Unfortunately things change by the end of the week as the upper flow swings round to arrive from the north over the weekend and push temperatures well below average for the time of year.

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The jetstream will be arriving direct from Greenland by Sunday, as HIGH pressure builds over the Atlantic and falls to the east of the UK.

Airmass temperatures in this northerly polar flow (measured at 850hPa) could even be low enough for showery wintry precipitation.

Cold late Springs are not unheard of in the SE, 1981 was a cold Spring with snow, for example. Recent Springs over the last 25 years have been milder than the long term, so this event is still “normal” weather.

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The HIGH is set to regress NW into the Atlantic and merge with a high pressure over Greenland.  Pressure over the Poles is rising as well, shown by the swing to negative Arctic Oscillation and related NAO.

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The result of higher pressure over the Polar regions and low pressure in mid latitudes is to push cold Arctic air south.  If this was January it would be a truly cold period coming up.

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With LOW pressure over the North Sea the resulting funnel of cold northerly winds will dig south across the UK and into Europe especially from Sunday into next week.  Sunday is the London marathon and, whilst showers are forecast coming down the UK during the day, it looks a mostly dry but cool start for runners.

Most of the wintry action looks set for Benelux but here the Tmax during the daytime are likely to be around 10C, but fall to near freezing at night, with frosts under any clear skies.  Occasional wintry showers are possible, especially Monday. Note the Tmax temperatures on Monday daytime shown below.

Cool for the time of year for sure, as shown by the contrasting anomaly charts below between this week and next.

During this cold spell next week fresh falls of snow are expected across mountain regions of Europe, especially Norway and the Alps and the highlands of Scotland and Northern England.

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At lower elevations snow might fall at times during this cold spell, however, strong April sunshine (as strong as August) will quickly raise temperatures between showers so that, even with any wintry precipitation, ice and frost will melt rapidly away.  Icy roads overnight are also unlikely at lower elevations because soil and surface temperatures have risen well above freezing.  Nevertheless, gardeners should be aware of the chance of frost and 10cm soil temperatures will fall to near 5C over the course of next week.

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How long will this last?  Charts show the cool spell lasting for much of next week but with some amelioration throughout likely.  Stronger sunny periods will make it feel satisfactory out of any wind but night time on east coasts in heavy wintry showers, for example, will feel distinctly chilly!

Where’s the heat gone?  It’s worth pointing out the very high temperature anomalies over N Africa and Greenland at the moment.  The highest and earliest surface melt across the Greenland ice cap is likely to continue next week in the upstream flow around the Atlantic block. The build up of heat in N Africa (shown below) could, in the right conditions, bring continental heat to the UK later and, perhaps some decent thunderstorms, but this is all just speculation.

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The Atlantic is showing off some classic visible cloud features of cyclone birth and decay today.  Systems labelled 1-4 on the satellite photo above show different features including stages of cyclone / mid-latitude depression formation and decaying high pressure ridge all on one satellite picture.  The chart below shows the same view with fronts.

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Starting with LOW number #2 (why not?!): the spectacular classic cloud spiral of LOW #2 indicates a mature low occluding and filling.

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This maturing occluding LOW has a couple of interesting extra vortices near the low core.

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Despite their angry look, classic cloud spirals like this on satellite photos are actually decaying and filling lows, losing their strength as pressure rises in the low core.  This particular LOW has a spectacular cold front of over 1500 miles stretching from 60N to the sub-tropics. The red colours on the RGB false colour eumetsat image below shows the cold continental polar air surging in behind the cold front.

Low #1 is a rapidly intensifying LOW off the coast of Labrador.  It looks harmless as a smudge of cloud but this shape … a so called “baroclinic leaf” indicates the birth of an angry developing storm: rapid cyclogenesis.

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This will deepen and pressure will fall rapidly in the next 24 hours as frigid continental air collides with humid maritime air under the influence of an active 200mph jetstream.

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LOW #1 is expected to form a big storm in the Labrador Sea by Wednesday. The fronts on this storm are then forecast to stretch clean across the Atlantic and bring the SE our first frontal rain for over a week by later Thursday.

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System #3  on the top satellite photo shows the HIGH pressure lingering over the South of the UK but regressing into the Atlantic.  This ridge has dominated mid to late March weather in the UK but brought a lot of anticyclonic gloom to the SE.  The deflating ridge will allow a more unsettled Atlantic westerly regime to dominate late March and early April weather.

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Low pressure #4 is an interesting developing depression in the Mediterranean, courtesy of a southward limb of the jetstream. Currently a disturbance dumping snow over the N Atlas in Morocco, this LOW is set to deepen across the Mediterranean through the week.  It will track directly ENE through the Med and bring snow to the Atlas mountains, rain to N Algeria and foul wet, windy and wintry conditions to Italy and then more snow and wintry weather to the Balkans.

Finally, for the UK our weak ridge is deflating to the SW and this will open the door to zonal westerlies and frontal systems bringing rain and wind from later Thursday and into the weekend.  Ensembles below show the dry spell ending this week and some notable rainfall spikes in the days to come, especially over the weekend.

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After a pleasant dry and sunny day in the SE, the satellite photo from this evening spells trouble ahead for mid-week with a deep depression over Iceland and an increasingly active Atlantic with a long frontal boundary trailing across the ocean into thick bands of cloud.

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Reigate and the south of England are set for a potentially very wet day on Wednesday as shown on the Euro4 chart below showing just 12 hours of rainfall during the morning.

Unusually high rainfall totals could mount up, possibly to around 30mm for the day on some models. However, models usually exaggerate rainfall totals but it is likely to be soggy!

A strengthening Atlantic jetstream is causing the convergence of moist sub-tropical and polar air at the Polar Front over the Atlantic Ocean.  The winds can be seen converging on the Atlantic chart below.

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The convergence of Polar and Tropical airmasses can also be seen on this chart showing the trajectory of winds arriving in the UK on Wednesday.  Note the surface tropical airmass circulates round the Azores high and meets the incoming Polar air from Canada.  It’s the less dense moisture laden maritime tropical air which is lifted over the cold, enhancing rain on frontal boundaries.

The 850hPa (15oom) temperature chart below shows the steep temperature gradient between contrasting airmasses across the Atlantic.  The water vapour Meteosat satellite picture shows a broad sweep of moisture laden air crossing the Atlantic from the Sargasso Sea.

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The boundary of the contrasting moist Polar and humid Tropical airmasses causes lift and this is set to rapidly form a depression over the UK later on Tuesday into Wednesday courtesy of a jetstreak to the west of the UK.

Large amounts of Atlantic moisture are set to converge in this low pressure as airmasses meet at frontal boundaries.

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The result over SE England is an unsually steep rise in dew point to 6-7C, indicative of increasingly moist air.

The atmospheric column looks to become exceptionally moist on Wednesday and saturated through to a height of 25,000 feet.  Cloud depth will make it a very dull day.

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Rainfall charts look impressive and, at the moment, show the rain arriving on Wednesday morning. Here is a medley of rainfall charts from 3 different models showing the potential for a deluge, though do note that models tend to exaggerate these totals this far out.

The 6 hourly total chart from GFS shows an extraordinary 26mm over parts of SE on Wednesday morning.  This would lead to local surface flooding on roads.

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Note this is not a convective event so no thunderstorms are likely, which makes such high rainfall even more unusual. It could be the biggest daily rainfall total for quite a while, over 36.6mm of rain in a day was recorded on 24 August 2015. Keep posted on twitter and check MetOffice forecasts for updates if travelling.  Some disruption could occur if this comes off as models suggest.  Milder and settled conditions are expected into the weekend after our mini-monsoon!

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Wanstead Meteo

Over the next two weeks speculation on Christmas Day weather will inevitably build. Will Christmas be white or green?

Shoulder of Mutton lake, Wanstead PArk

At this range it is impossible to tell from standard meteorological models though from the 15th, 10 days before the big day and when models can start to be relied upon for at least a general trend, the pieces of the weather jigsaw will start to fall into place.

Latest odds offered by bookies William Hill for a single snowflake at London Heathrow are currently 5-1, slightly shorter than I’d expect at this time of year. With the predominance of the European high I’d expect those odds to start to come down.

In terms of proper snow falling and settling, there has not been a white Christmas in Wanstead for over 30 years. In 2010, we could still see the Christmas card Victorian snow scene in small patches if our gardens…

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