Archives For Greenland

The well-advertised cool-off this week arrives in Reigate late Monday and through Tuesday with the coolest days being mid-week: some remarkably cold upper air temps are due to cross the SE this week. While Tuesday will be cold and bright under a brief ridge of high pressure over SE, the coldest feel will be in more windy and damp conditions Weds night – Thurs am.  Whilst this is far from an early winter-Armageddon we are certain to see chilly temps during the day staggering to maybe 5 or 6c Tmax with night temps dropping below freezing: car scraping, road gritting with cold days and chilly nights, if you happen to be out, will be the norm in Reigate from Tuesday on wards, but must stress nothing outrageous, just chilly, especially when wind picks up with arrival of a LOW skirting down from N of Scotland and journeying south down the North Sea mid-week: sticking tightly to the East coast.  This will eventually introduce a COOL POOL low over the near continent which will form the basis of weather in the SE for later this week and into the weekend with cool and, usually gloomy, NE and E winds off N Sea, whilst a frosty HIGH builds over the north of the country. 

A meridional (wiggly) North-South jetstream is responsible for dragging down frigid air from the Poles… the distance from the Greenland Ice sheet to Reigate is some 2000 miles, so this Polar air will warm up over the comparatively warm North Atlantic Ocean courtesy of the warm ocean current, North Atlantic Drift. Nevertheless, a series of cold fronts Monday and then again Weds will introduce successively colder air from N-S down the country, with accompanying rain (snow for north and northern hills).  These fronts will also bring down rain, occasionally “icy” / sleety mid week, possibly with dusting of snow too for higher ground locally.  The complicating factor in this Arctic plunge scenario is a vigorous area of LOW pressure regressing down the North Sea, driven by the northerly jetstream, which has some cold polar air from Greenland wrapped into the circulation.  The North Sea is about 9c so this will have warmed up considerably since its departure from the Ice Sheet but the warming from below could invigorate wintry showers for the East coast. The GFS model has the additional possibility of the cold front dusting the SE with snow overnight Weds into Thursday am as this cold air sweeps over and freezing levels touch down on the Downs. As usual, check back for updates as this interesting wx takes shape this week as models are hinting at further COLD for next weekend. Follow @RGSweather on twitter too! 

So, prepare for the arrival of the Queen of Freezer!

The Greenland ice sheet always melts in summer.  Snow and ice especially melts around the lower altitude edges, coastline and often the “saddle” region between the north and south ice caps. The ice sheet snow cover always reaches a maximum at the end of winter when the entire land mass is covered in snow, 100%. The minimum snow cover reached by late summer (i.e now) is of greatest interest to climate scientists because summer snow cover varies each year and is therefore a more critical indicator of climate change. While the Greenland 2012 melt season was intense, the 2013 melt started late (May). Greenland currently has a greater coverage of snow than average for this time of year.

Of greater interest is the longer term trend. This is more of a climate paradox. While the cover of Arctic SEA ice in summer is reducing in extent and thickness, the snow cover over Greenland at the end of summer appears to have increased since satellite measurements began in the 60’s. Note the downward spikes on the graph… they have reduced in size showing a greater cover of snow over Greenland surviving and occasionally falling during summer. 

So… paradoxically, whilst summer minimum Arctic Sea Ice cover is reducing, the cover of snow over Greenland in summer appears to be increasing. Nevertheless, before we consider this as an indicator of less global warming (AGW), a glance at a global map of 2013 snow cover departures from the average shows that Greenland is alone amongst snowy parts of the globe in this increasing trend of summer snowiness.  Most high mountains which hang onto snow through the northern hemisphere summer are showing markedly LESS snow than average: Himalayas, Rockies, Alps and Pyrenees are all displaying lower than average snow cover for July.  This paradox of more summer snow cover in Greenland while summer Arctic Sea ice reduces in extent and thickness is another illustration of the complexity of global climate and how easy it is to pick out data to suit any agenda.

Meanwhile, forecast for today: Greenland ice cap today light winds, snow, cloudy, -25ºC; Reigate +22ºC, sunny, light winds.

greenland temp

sources

http://nsidc.org/greenland-today/

http://climate.rutgers.edu/snowcover/index.php

http://www.climate4you.com/

The cool pattern of winter weather we have experienced in Reigate during February has not been reflected everywhere across the Northern Hemisphere.  Greenland, in particular, has been warmer than usual. Whilst Reigate has experienced Polar air incursions pushing temperatures 2ºC colder than average, Greenland has experienced more frequent warm southerly air masses than usual and it’s HIGH pressure has not developed so strongly this month to keep out the warm air, until recently. The Greenland ice sheet doesn’t usually start melting until April or May (average 1980-2010). In 2013 surface melting has started already in SE Greenland. So, the 2013 Northern Hemisphere winter climate appears to be acting strangely with extreme storms in the USA (Sandy and Nemo), heavy snow in Russia, severe storms in the Atlantic and now the early onset of melting on the Greenland ice sheet being startling reminders that weather patterns have been far from “average”.  Reigate is fortunate to have  escaped any severe weather on this scale!

Arctic air travelling courtesy of the jet stream will blow in from Greenland and deliver frigid temperatures and snow to Reigate for the first part of this week. Precise details of snowfall are still changeable but temperatures are certainly due to take a fall during this week but getting there will not be straightforward!

13-01-2013 08-21-08Light snow on Monday (see map left) currently forecast to start falling in Reigate early am (updated sun07:30), could reach 6cm (update 8pm sunday:unlikely – looks much less now) but, oddly, temperatures may rise considerably above freezing Monday afternoon (+4°C?) and bring rain for a while probably melting any fallen snow before cooling down Monday night with more snow possible: a v complex situation which will change hourly! A developing LOW along an occluded front later on could bring more snow to the SE on Tuesday when air temperatures will probably stay below freezing all day and wind chill at midday could be as low as -9°C. The reason on Monday & Tuesday … a strong jet stream blowing direct from Greenland at over 100mph, 9km above our head, will bring Arctic air (-50°C at 9km) direct to Reigate in less than 24 hours journey time from “ice sheet to high street”!  A BLOCKING HIGH sitting out west in the Atlantic is preventing milder air from making progress further east.  The cold weather will continue so long as the HIGH stays put.  The situation is likely to remain much the same for a while, though at the moment forecasts are uncertain beyond a few days ahead due to the “sudden stratospheric warming” which is taxing every super-computer weather forecasting model including the UK Met Office, let alone your friendly RGSweather station enthusiasts!

Update! by mid-week the HIGH will slip over to the north of the UK and drag in bitterly cold easterlies from the continent (see map wednesday thursday) Snow showers likely for eastern England.