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March 2013: “In like a lamb and out like a lion!”  

March 2013 in Reigate recorded an average temperature lower than January and a minimum temperature lower than February and the lowest dew point of -7.1°C so far this year. It was an exceptionally cold month and got colder and colder from the the one lovely day at the beginning.

The opposite of what should happen, did happen.  March started with rapidly rising temperatures reaching over 16°C in the first week but things deteriorated rapidly after that as a Polar blocking HIGH built to the North and pushed vigorous easterlies and north easterly winds towards the UK for much of the month.  A number of Atlantic LOWS tried to bust the BLOCK but were pushed to the south of the country where fronts between freezing polar air and milder air created exceptional blizzard-like conditions for some areas.  The Channel Blizzard created exceptional snowfall on 11 March for the Channel Islands but Reigate got away with 1cm of lying snow which melted in the town quite rapidly and left a day of severe wind chill down to -12ºC at 5am.  Mini snow drifts persisted on the North Downs and Reigate Hill for several days.  Arctic air arrived later on the 12 March as the LOW drifted SE and dragged northerly winds in creating brighter conditions with spectacular cumulus snow and sleet showers through to the 13 March.  Reigate had episodes of heavy sleety rain mid-March and even a clap of thunder (first recorded since Christmas Day!) on 18 March as milder air met colder air creating unstable conditions on complex fronts.  March 23 saw another snow event over the UK: record-breaking snow fall occurred to the NW over the Isle of Arran, Cumbria and Wales but Reigate again escaped the worst with a few cm falling but melting rapidly while a covering of snow lingered for a few days over the Downs.  Cold easterlies then dug-in and pushed dew points to -6°C with temperatures hovering around freezing through to the end of the month.  Dull blanket layers of stratocumulus caused by a persistent isothermal layer at around 900m in the easterly winds brought occasional flurries of sleet and snow grains and severe wind chill but little sunshine.  Temperatures fell throughout the month and Spring was delayed in the coldest UK March since 1962. 

Very low dew points (down to -7ºC) show that dry air persisted for much of March.  People with lots of hair to manage may have had a difficult time through March with curly hair going straight or fly-away due to drying out in the low humidity and dry, skin-cracking north-easterly winds.  Low dew points have a bad impact on curly hair, dragging out the moisture from the hair into the dry air.   Whilst dew points in the UK are usually high in our moist humid climate which is good for keeping curly hair curly, anyone with lots of hair to manage should check dew points on weather forecasts very carefully, especially in winter and avoid expensive hair-dos on days with low dew points… just a thought.  More seriously, farmers across the UK struggled with lost livestock in deep snow and delayed sowing of spring crops.  The weather sparked some debate over climate change and the possible causes of the cold which gripped the whole of the northern hemisphere.

January av 3.7ºC; HIGH 11.9ºC LOW -5.9ºC RAIN 58.4mm
February av 3ºC HIGH 11.6ºC LOW -2.4ºC RAIN 42.9mm
March av 3.3ºC HIGH 16.2ºC LOW -3.3ºC  RAIN 67.8mm

A medley of photos showing Reigate today: heavy snow in the morning melted rapidly as air and surface temperatures remained above freezing most of the day.  Colder air is on the way overnight and tomorrow.  Read on to find out why…

Here is the weather synopsis for this week: HIGH pressure to the north, LOW pressure to the south and a weak jetstream well to the south of the UK: result = POLAR NORTH EASTERLIES flood across the UK…again! Crazy low temperatures for March are forecast early/mid week with 850hPa temps at 1500m as low as -8°C over Reigate and surface temps struggling above freezing: wind chill as low as -9°C possible at night, daytime wind chill as low as -5ºC with winds up to 20mph feeling outrageously cold for this time of year, or any for that matter!

Sunday: watch out for snow streamers developing across the SE and East Anglia as the cold easterly wind crosses a comparatively warm North Sea. The 12°C difference between sea surface temps (+6°C) and air mass temps (-6°C at 1500m) could cause instability on decaying fronts lingering near the SE. This could cause the formation of perky showers in “lines” (snow streamers) which could mean some areas get prolonged snow whilst others, a few miles away, see none at all.
Monday and Tuesday: colder, drier, brighter; but snow showers always possible.

update Sunday 24: Big uncertainty about the end of the week: less uncertainty now: COLD set to continue: snow storm for Easter? 😦

Tuesday 11 March in Reigate started with very cold wind chill temperatures down to -12°C at 5 am brought by strong NE gusts of +30mph blowing snow wildly into mini-drifts, especially on the North Downs.  Arctic air arrived from the North by mid-morning and, with slackening winds and breaking cloud, brought a much warmer and brighter end to the day with max temps of 4.4°C. The satellite photo shows the advancing Arctic air mass changing the cloud pattern as it nudges the cold NE winds to the south.
Calmer, brighter, drier HIGH pressure will remain in Reigate for a few days until a POLAR LOW from the NW brings rain and wind for the weekend. The arrival of this low from Greenland, wrapped with cold air, will not bring respite from the cool weather but temperatures will rise to 5-7C max so it will seem mild compared with our recent icy Polar experience!  More later on a potential re-arrival of Spring on 20 March!

Today illustrated how observing changing cloud types can help predict an approaching front and rain. If you look up, you can often have a good shot at forecasting the weather several hours away. Today, a warm front approaching Reigate rapidly from the west was heralded by a series of cloud formations. In case you missed the drama, here is a round up of the best bits:

A bright blue sky and a frosty calm morning quickly gave way to a milky sky with the appearance of high cirrus cloud building into a thicker blanket of milky cloud called cirrostratus. These indicate increasing moisture in the upper atmosphere, which is often a sign of deteriorating weather and frontal rain approaching. A “halo” might appear around the sun with thickening cirrostratus: again, a sign of deteriorating conditions aloft. Cirrostratus clouds continued to thicken and lower into a blanket of middle altitude clouds called altostratus. These turn the sun into a fading white disc. Altostratus clouds are rarely thick enough to cause rainfall. As the front approaches low level stratus clouds appeared scudding above Reigate Hill in the 50mph winds aloft. Persistent rainfall started in Reigate mid-afternoon when thicker featureless nimbostratus clouds moved overhead, marking the arrival of the front proper. The temperature rose throughout the day, from 0°C at 8am to 10°C by 10pm, another indication of an approaching warm front.  The front travelled 200 miles in about 4 hours, a 50mph race across the UK and, despite the gathering wind and gloom, brought a wonderful lesson in meteorology, hope you had a moment to enjoy it!