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The ingredients for our Monday storm are stirring in the Atlantic, as shown by the sat pic from today.
The Mother of LOW pressures south of Greenland is whipping up hurricane force winds and 50 foot waves in the Atlantic.
A warm plume of tropical air is being brought up by a weakening ex-tropical depression Lorenzo.
They meet at the polar front where an extremely powerful 240mph jetstream is due to lower surface pressure rapidly forming the storm which will cross UK on Monday.  The birth of our storm is called cyclogenesis: it is rapid and will cross the UK rapidly overnight Sunday to Monday.  It will continue to fall in pressure and intensify as it does so.  Conditions will be worst along the south coast and SE where wind gusts could reach 80mph, inland gusts of 60mph will decrease north of the M25. The beaufort scale below shows what these winds mean to you and your house. Sustained winds around Reigate will probably hover around 20-30mph, which are certainly not damaging. Gusts are a different matter and these could lift tiles, bring down branches or even weak trees ready to fall.  Loose fences and garden furniture not tied down may also blow about in gusts and cause additional damage.  Umbrellas will certainly be “difficult to use”, (I love this description!) which is, of course, a critical meteorological threshold occurring when winds exceed Force 6, 25mph. 

Chart on left shows rain forecast for tonight (Fri-Sat).  Chart on right shows some interesting synoptic situation in Atlantic early next week.

Reigate and SE could see some heavy and even torrential rain from late afternoon / evening today and overnight clearing Saturday am. Totals could exceed 30mm in places, but more widely totals between 10-20mm. This LOW is moving from SW in the Channel and proceeding overhead across the SE with a complex of associated fronts. This system heralds the mother of all LOWS which is moving in on Sunday… sweeping an unusually cold Arctic blast across the whole country by early next week. Autumn is here and the Atlantic shows signs of greater activity with a more active jetstream and the appearance of the first ex-hurricane / extra-tropical storm Humberto on the Atlantic Charts next week too.  Humberto is delivering Tropical air to the Pole, while our cold Arctic blast does the opposite.

The big news this weekend is the start of the temperature drop-off which looks to last most of next week.  Saturday will start this process off as cooler air is set to sweep down across the country, mainly from Sunday onwards.  Tmax might reach 12c but in the wind it’ll feel 10c or so and with rain as well it’ll all look thoroughly Autumnal!  Later next week there are signs of high pressure building back in with better weather and a recovery of temps, but let’s wait and see on that one!

850hPa drop this weekend

weather balloon

Weather information is captured from satellites, surface weather stations, ships, planes and also weather balloons which are launched regularly from sites all over the world.  Weather balloons have instruments which continuously capture data during their ascent through the atmosphere on several weather parameters including temperature, wind speed, humidity, pressure etc. The map shows the track of a balloon launched today, that ascended to 40,000 m over Swindon. The car icon shows the chase vehicle used to collect the instruments when the balloon eventually falls to earth.  You can track more weather balloons live at

Anti-cyclonic stratocumulus cloud continues to blanket Reigate and the SE of England in a cold, gloomy weather underworld.  A temperature inversion (where temperatures rise with height, instead of fall) at 1000 metres is trapping any rising air which inhibits convection spreading out the cloud mass to cover the entire sky: good to reduce rainfall, bad for any views of the sun!  Regrettably no light at the end of the tunnel yet: the north-easterlies circulating round the HIGH pressure to the North are likely to continue for much of the week and bring in blankets of stratocumulus cloud from the North Sea. This spectacular view from the EU Meteosat satellite today at midday clearly shows the cloud blanket voering SE England from 22,300 miles away.
Temperatures will struggle to exceed 5C in the days to come; this time last year temperatures were well above 12C and even hit 17C on a few days.

The cold easterlies predicted have created interesting and unusual cloud patterns across the country. The satellite photo from today shows ripples in the breaking cloud to the west of the hills in Wales and the SW.  The easterlies driving the cloud are part of the cold sinking dry air created by the anticyclone to the north east of the UK.  The easterlies are  forced to rise over the hills and then sink the other side (the “lee-side”), creating this wavy cloud pattern.
Another feature of this cold snap is illustrated in the video below which shows how temperatures have changed over the last few days.  Notice how inland temperatures drop significantly lower than anywhere near the sea. The sea stays warmer for longer during winter as it takes 5x longer to cool down (and warm up) than land surfaces.  The video shows temperatures rapidly falling to low temperatures inland but coastal areas are moderated by the warmer seas surrounding the British Isles.

The cold easterly winds and some light snow flurries will continue over the weekend as a weak short-wave trough (a “blip” in the isobars surrounding the HIGH) passes to the north of our region.  The very cold pool of upper air is drifting away to the south, so temperatures will recover very slowly through to Monday.  However, spring is certainly on-hold at the moment and, despite being a mostly dry week,  temperatures will remain lower than average in the continuing easterly air flow.  Watch next weekend as a low passes to the north of the UK which could bring a “last hurrah” for real winter conditions as a cold northerly is possibly on the cards.  Longer range forecasts give little cheer for us in Reigate and the South East as HIGH pressure seems to stick around to the North and bring in Channel lows to the south of the country bringing wet and cool weather.

Not about the weather but arguably still just about in the atmosphere … the small dot here is the International Space Station taken from Reigate last night on my Lumix GX1 with 45-200 zoom; f8 1/1000, ISO1600. ISS ~300 miles away: population 6; Moon ~240,000 miles away: population 0; … amazing! p.s. light snow possible for Reigate at weekend with a trough circling round the HIGH pressure bringing cold easterlies. High pressure looks like continuing but shifts in wind direction will vary the temperature … signs of warmer conditions next week.: scrap that!!… latest charts show cold Arctic plunge on 5 March – keep watching!

Snow cover picks out the high ground over South East England prior to the big thaw on 25 January 2013. Note the snowy North Downs and a thin thread of snow along the crest of the South Downs, in contrast to the lack of snow in the London Basin and the Thames Valley. Contrails radiating from London airports are also visible. Note the lack of snow near coasts, showing how the sea retains sufficient heat even in January to turn snow to rain or melt it.  The English Channel sea surface temperature off Brighton is still over 8°C.

Beautiful satellite image of UK covered in snow

Happy New year! 2013 dawned bright and beautiful over Reigate for January 1st 2013 as the low pressure of recent weeks gradually gives way to an anticyclone (High pressure) building from the south west which will bring calmer and drier weather for us in Reigate for a week or so, after a final shower or two tomorrow.  It may not be that sunny though: anticyclonic gloom is common in winter.  Also, check the chart below as temperatures are due to take a slide (predictably for January!) from the weekend.

London weather January 2013

satellite photo UK new years day January 2013

A snap-shot of weather today reveals how diverse and extreme and fascinating our European weather actually is! The east – west split is obvious: freezing temperatures on the continent with everywhere east of Germany below freezing. To the west we are bathed in warm balmy Atlantic air which is over 10°C. Northern Italy is enjoying almost spring-like weather in the Po Basin, possibly due to air sinking and warming from the Alps.

Meanwhile, Iceland is due to be hammered by hurricane force winds over 76mph (>34m/s)with an intensifying LOW pressure bringing extremely high winds to the NW of the country on Saturday. This LOW pressure will have a central pressure of 942mb: which is extraordinarily low.  Winds blow from HIGH to LOW pressure (albeit deflected to the right by the coriolis force – more later on this).  The bigger the difference between HIGH and LOW pressure, the higher the winds.  See the weather map below and spot the isobars placed close together over NW Iceland: this indicates ferocious Force 12 winds.  The UK will be breezy, located on the edge of this LOW, but no where near as windy as Iceland, fortunately. Heads-up for a “heat-wave” in the UK next week :-)!!

intensifying LOW near Iceland