Originally Posted by M.T. Cranium - 15th Nov 2010
Time to confirm what I've been hinting at here and in the daily forecast thread.
My long-range seasonal outlook calls for colder than normal temperatures for most of the winter months, and higher than normal snowall amounts.
Expect periods of very cold weather to develop late November and through much of December as blocking high pressure becomes well established over the Baltic regions. While the Atlantic will occasionally push back and bring milder, wet conditions, the frequency of east winds and cold combined with a storm track close to the south coast of Ireland and into the southern half of the U.K. should make for frequent snowfalls in many parts of Ireland and the U.K. Predicting temperatures to average 1.5 to 2.0 C below normal in December and some stretches possibly sub-freezing, with snowfall likely before Christmas making for a white Christmas for many.
The January outlook calls for this cold to deepen for part of the month before a brief reversal indicated by some of the research index values. Therefore the month may feature some major winter storms mid-month as this pattern reversal begins. Despite the milder end, the month is likely to continue to average below normal by about the same amount as December, 1-2 C and possibly more.
February was less conclusive from the research index values but unless the January reversal is highly energetic, could see the blocking redeveloping and leading to a colder than normal February as well.
Given the strength of cold in the outlook and the dependence of mean winter temperatures on snow cover near the lower end of the spectrum, one cannot rule out a sort of near-extreme or even extreme outcome, since mean monthly temperatures below 2.0 tend to promote continuous snow cover and therefore a fairly easy slide down to sub-freezing values from the same air masses as are present for 2-3 C.
In other words, I'm predicting a cold winter with lots of snow, that could become an epic winter. Stay tuned.
One other detail to note, the storm frequency from my research should be on a fairly well-modulated 3.5-day cycle with stronger events every seven days or so (this is not exact so it won't work out to the same day every week). The stronger events are likely to produce their share of slow-moving but deep "Channel" or French lows promoting a strong east wind and outbreaks of snow. One of the better scenarios I foresee for snowfall comes with the December full moon and "northern max" event of 21 December. This is bound to produce an intense storm over western Europe and I am giving something like 2-1 odds for this to be a cold weather storm event with at least some snow or sleet in the mix for Ireland, whereas if the pattern happens to be stuck on mild then, look for a very mild and windy sort of event followed by much colder weather.
In general, through the mid-winter period, the stormy episodes will fall at full and new moons, and approximately mid-way between them with a second set of high-energy peaks. This pattern will continue into late winter but with the secondary energy peaks decoupling from the primary (full/new) this gives a more frequent distribution of storms that, if coupled with a cold pattern in February, could lead to a steady parade of disturbances around the southern flanks of blocking high pressure to the north and northeast.
Anyone interested in a more detailed forecast could find one later today on Net-weather posted by my research associate and friend, Blast from the Past as he is known to the weather forum world. That will be UK-centric but after all, the winter patterns are bound to be quite similar, and the general theme appears to be cold winning out over mild again this winter.
Looks like this pattern could be setting up gradually later this month, and I would not be surprised if there is some snow even in late November.
