Earliest widespread snow in Britain for 17 years apparently. Third day in a row of snow here and after a dry day a sudden heavy shower as I was driving home from work turned the city roads white. Despite care, appropriate speed and engine braking, I skidded to a halt approaching traffic lights down a hill. That was fun (thankfully I can say that).
The cold is set to last for at least another week in the UK, and it is strange to have it cold so early. Although the Met Office is no longer making seasonal forecasts since the much ridiculed “BBQ Summer”, this seasonal forecast by its Norwegian counterpart, the Meteorologisk Institut, caught my eye.
The seasonal outlook for Norway for the period December 2010 – February 2011 is temperature above the normal for the whole country. The greatest deviation from the normal is 2.5 °C above and this is located to the inner part of Southern Norway. For most of the coastal areas the seasonal outlook is 1.5-2 °C above the normal. For the rest of the country it is ca. 2 °C above the normal. The normal period 1961-1990 is used here. It is important to keep in mind that the values presented in the map are three monthly averages. Information about the different months is not given. The seasonal outlook is only made for the temperature at present and does not give any information about expected precipitation.
This has been higher profile in the news in Norway than normal since the country, like the rest of Scandinavia, is in the grip of very cold temperatures. Earlier in the week an Aftenposten article set this forecast against the potential for record breaking cold this week. [Update: even lower temperatures forecast for next week]
Record Cold? According to a State Meteorologist at the Norwegian Meteorological Institute the cold wind from Siberia sets old (November) records at risk:
- Blindern in Oslo, in 1965 measured 16 degrees (C) below freezing. For Thursday and Friday minus 13-14 degrees is predicted.
- In Bergen, the record from 1985 is 8.9 degrees below freezing in the centre. Towards the end of the week Bergen expects 7-8 below.
- Tromsø measured -12.5 degrees in 1955. Here, minus 10 degrees is forecast.
However, experts, scientists and meteorologists are not unanimous in prediction of seasonal temperatures. In contrast to the Norwegian forecast, senior scientist and climatologist John Cappelen at the Danish Meteorological Institute (DMI) suggests a cold winter ahead. He sees the characters in the higher layers of air that remind him of conditions that last year provided stable and cold weather.
“We are now in a phase where NAO is very strong and negative, just like last winter. Continuing the trend, so it may mean that there is a chance for another cold winter in the north-western Europe” says Cappelen.
But he is not so sure of a cold winter as it appears in the media – “The conditions can rapidly change.” A negative NAO means that the wind blows steady from the east and the winter weather is dry and cold, has remained stable for a year. It has the not been this way for 40 years. “It was this tendency that gave the cold winter last year” says Cappelen. The open question is how long and how strongly the phenomenon continues.
His employer, DMI, has a forecast for the first three months indicating that the temperature is 0.4 degrees warmer than average for the period 1961-90. If this bears out, the winter will be milder than last year, but colder than in recent years. The Aftenposten article also mentions a report on yr.no (Met.no equivalent of BBC weather news) of a Russian scientist who expects “the coldest winter in a thousand years, because the Gulf Stream has weakened.” Others believe that winter will be cold because of unusually extensive snow cover over the northern part of Russia in the late autumn; heavy snow forms the high pressure that tends to move across to Norway.
Erik Kolstad, climate scientist at Bjerknessnteret (The Bjerknes Centre for Climate Research (BCCR) said
“I think most of the last theory, but dare not say anything about what kind of winter we have in store: – there are so many things that influence winter climate that it is incredibly difficult to notify in advance. Right now the NAO is slightly negative, and a warning from U.S. researchers suggests that it may remain so for a while. But beyond that it is impossible to say anything. There does not appear to be anyone who dares to create alerts for an entire winter season any more” said Kolstad to yr.no.
In Sweden the press also picks up the theme – from Svenska Dagbladet “The North Atlantic Oscillation (NAO) is in a negative phase, which, before last year’s winter had not occurred in years. The previous default mode was an NAO positive phase with the warm southwest winds which resulted in mild, almost snow-free winters in northern Europe. ”
“Now it looks like last winter. If it continues, it means cold. But you never know when the market turns” said meteorologist and researcher Per Kållberg at SMHI. Meteorologists around the world are now discussing how long the negative phase continues. It started in December 2009 and has persisted since then, which is the longest period of 40 years, according to Sydsvenskan (Southern Swedish newspaper and website). “The fascinating thing is that [we have] known about this phenomenon for a long time but have no idea why it occurs” says Per Kållberg.
On Wednesday northern Lapland had minus 36.6 degrees – the season’s lowest temperature so far, according to SMHI. It is also the lowest November temperature in Sweden since 1995, when it was minus 37.0 degrees in Central Lapland.
Going back to the Norwegian seasonal forecast, the Met.no site helpfully explains the origins of the forecast:
- The starting point is 40 different projections (“ensemble”) from the European weather center (ECMWF) in Reading, England.
- Out of these, the deviation from what is normal temperature. (Deviations are called “anomalies”).
- When deviations are estimated, are calculated the mean value (in our case the most probable temperature) for a specific location (ie Oslo). 40 calculations are thus boiled down to a value / a forecast.
The European Centre for Medium-Range Weather Forecasts (ECMWF) is funded by 33 countries. The UK contribution is 16% of the £37M for 2010. So does this mean it was the ECMWF that was at fault for the BBQ Summer, but that the Met Office just took the flak for it? Or was it the Met Office interpretation for the UK?