Winter 2010-2011 Winter Weather Forecast, by iWeather Online's Peter O'Donnell.
My long-range seasonal outlook calls for colder than normal temperatures for most of the winter months, and higher than normal snowall amounts.
(Note - Nov 16 update at bottom of page)
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 January.
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 can find one on Netweather posted by my research associate and friend, Blast from the Past as he is known to the weather forum world.
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.
UPDATE ADDED: 11PM, 18 November 2010
As we're seeing today, I think any milder interludes this winter could easily become very stormy. I've just posted this on our net-weather thread so will cross-post it here, it's from my research on event timing and would point to the sort of timetable for energetic low pressure events near Ireland over the winter. Ireland is close to one of nine timing lines in our research model, and so these peak energy situations normally translate to stronger low pressure being nearby, the further north they get, the further west they will be at event time because the timing lines tend to run NW-SE rather than N-S.
This is the information just added to the Netweather thread ...
Just wanted to add some timing for energy peaks in the research model -- these are dates we'll be watching for the strongest storm development, starting with today:
JC+SO ... 16 NOV, 13 DEC, 9 JAN, 6 FEB
Full moon 21 NOV, 20-21 DEC, 18-19 JAN, 17 FEB
N Max 25 NOV, 20-21 DEC, 16 JAN, 12-13 FEB
weaker "R" events about four days later than N Max
SC+JO ... 1-2 DEC, 29 DEC, 26-27 JAN, 23 FEB
new moon 5 DEC, 3 JAN, 2 FEB, 3 MAR
S Max ... 7 DEC, 2 JAN, 30 JAN, 26-27 FEB
another cycle of weaker "R" events four days later than S Max
Just note how this works in general, the main pulse of events at mid-winter is every 7-8 days with a weaker event thrown into the cycle in the longer gaps. The related full/N and new/S sets of events get further separated each month until by spring these are up to seven days apart. So the complex timing of the system has a monthly rhythm that tends to repeat but with one set of events separating out from the rest.
What makes this winter's timetable very interesting is that the SC/JO and JC/SO sets are well aligned and superimposed and also have a third energy peak that would form an independent moderate energy set on its own, so as seen with today's example, these disturbances may be very strong throughout the winter season. As the full/N and new/S events are usually the strongest of the set, this is more or less doubling up the chances for strong storms to develop all winter. I like the chances therefore for stormy tendencies to be increased over background, and so the question becomes, what kind of storms? For that we went to the background flow or circulation forecasts from another part (independent to some extent) of the model.
As this was pointing more to cold than mild (with mild most likely later January) we think a lot (not all) of these storm events will be tracking south either through or south of the UK.
Willing to speculate that this will all combine to create a very energetic winter circulation over Europe and if cold plays a dominant role, then it would be a really unlucky outcome for there NOT to be significant snowfall with all of that.
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 January.
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 can find one on Netweather posted by my research associate and friend, Blast from the Past as he is known to the weather forum world.
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.
UPDATE ADDED: 11PM, 18 November 2010
As we're seeing today, I think any milder interludes this winter could easily become very stormy. I've just posted this on our net-weather thread so will cross-post it here, it's from my research on event timing and would point to the sort of timetable for energetic low pressure events near Ireland over the winter. Ireland is close to one of nine timing lines in our research model, and so these peak energy situations normally translate to stronger low pressure being nearby, the further north they get, the further west they will be at event time because the timing lines tend to run NW-SE rather than N-S.
This is the information just added to the Netweather thread ...
Just wanted to add some timing for energy peaks in the research model -- these are dates we'll be watching for the strongest storm development, starting with today:
JC+SO ... 16 NOV, 13 DEC, 9 JAN, 6 FEB
Full moon 21 NOV, 20-21 DEC, 18-19 JAN, 17 FEB
N Max 25 NOV, 20-21 DEC, 16 JAN, 12-13 FEB
weaker "R" events about four days later than N Max
SC+JO ... 1-2 DEC, 29 DEC, 26-27 JAN, 23 FEB
new moon 5 DEC, 3 JAN, 2 FEB, 3 MAR
S Max ... 7 DEC, 2 JAN, 30 JAN, 26-27 FEB
another cycle of weaker "R" events four days later than S Max
Just note how this works in general, the main pulse of events at mid-winter is every 7-8 days with a weaker event thrown into the cycle in the longer gaps. The related full/N and new/S sets of events get further separated each month until by spring these are up to seven days apart. So the complex timing of the system has a monthly rhythm that tends to repeat but with one set of events separating out from the rest.
What makes this winter's timetable very interesting is that the SC/JO and JC/SO sets are well aligned and superimposed and also have a third energy peak that would form an independent moderate energy set on its own, so as seen with today's example, these disturbances may be very strong throughout the winter season. As the full/N and new/S events are usually the strongest of the set, this is more or less doubling up the chances for strong storms to develop all winter. I like the chances therefore for stormy tendencies to be increased over background, and so the question becomes, what kind of storms? For that we went to the background flow or circulation forecasts from another part (independent to some extent) of the model.
As this was pointing more to cold than mild (with mild most likely later January) we think a lot (not all) of these storm events will be tracking south either through or south of the UK.
Willing to speculate that this will all combine to create a very energetic winter circulation over Europe and if cold plays a dominant role, then it would be a really unlucky outcome for there NOT to be significant snowfall with all of that.