Whilst debate rages over the veracity and accuracy of long range weather forecasts, it hasn't stopped the flood of seasonal outlooks being issued.
Showing posts with label Forecast. Show all posts
Showing posts with label Forecast. Show all posts
Monday, October 19, 2015
Peter O'Donnell and WSI issue winter forecasts
Whilst debate rages over the veracity and accuracy of long range weather forecasts, it hasn't stopped the flood of seasonal outlooks being issued.
Monday, October 12, 2015
Accuweather announces Winter 2015-16 forecast for Ireland and UK
The first comprehensive Winter 2015-16 forecast has bucked the trend of tabloid predictions of record breaking cold and has instead opted for less severe outlook.
Monday, September 24, 2012
Peter O'Donnell's Winter 2012-13 Forecast Summary
Based on my usual methodology and a consideration of the unusual ice-free anomaly expected to start the season, the following is my expected temperature and precipitation trend for DEC-JAN-FEB (following a November with expected mild temperatures 1-2 C deg above average, and near normal in precipitation ... October expected to be near normal for temperature and somewhat on the wet side of normal).
DECEMBER looks fairly close to normal (on the whole) with a roughly equal mixture of mild and cold days. There may be one relatively severe cold spell of 2-4 days around the middle of the month towards the 20th. This might not produce much snow as it could be a shallow incursion but some snow would be likely given the temperature anomalies indicating below zero temperatures briefly. Before that, the period 7th to 13th is expected to be quite mild (highs could reach 11-13 C), and the run up to Christmas increasingly mild with rain replacing any earlier sleet or snow in most areas but there would be a better chance for snow in north-central parts of Britain around Christmas. A stormy interval may develop just around or after Christmas Day. Numerical index values suggest a windy day on the 26th so there's one specific daily forecast to test out.
DECEMBER looks fairly close to normal (on the whole) with a roughly equal mixture of mild and cold days. There may be one relatively severe cold spell of 2-4 days around the middle of the month towards the 20th. This might not produce much snow as it could be a shallow incursion but some snow would be likely given the temperature anomalies indicating below zero temperatures briefly. Before that, the period 7th to 13th is expected to be quite mild (highs could reach 11-13 C), and the run up to Christmas increasingly mild with rain replacing any earlier sleet or snow in most areas but there would be a better chance for snow in north-central parts of Britain around Christmas. A stormy interval may develop just around or after Christmas Day. Numerical index values suggest a windy day on the 26th so there's one specific daily forecast to test out.
JANUARY looks relatively mild but with severe cold forming gradually off to the north and east of Ireland and the U.K., some intervals of modified cold could intrude, perhaps less forcefully in south and west regions of Ireland. The month may also become rather stormy at times especially in periods around the 10th and 25th. Some damaging winds would not surprise me given the developing thermal gradient across the Atlantic and a likely very strong zonal jet stream at times. A trend to much colder weather getting closer to Britain at least is likely near the end of the month although mild weather could hold on in Ireland and the southwest parts of England.
FEBRUARY is expected to be much colder than average by 1.5 to 3.5 degrees with considerable snow or sleet and frequent easterly winds. This will develop because of massive blocking to the north of Ireland and the U.K. extending from Iceland to Scandinavia. There is some indication of a very severe period of wintry weather. This severe cold may last some time beyond the end of the month.
I may update this seasonal forecast if I have any further results from ongoing research, but this is the output of the current research model with some consideration given to the ice anomaly. I suspect it will intensify the pattern that would have existed otherwise, so I have tended to amplify the numerical output on either side of normal. Once severe cold is established over snow cover it is hard to dislodge during the depth of winter, but would also warn that February is the least reliable of the three monthly forecasts not only because it's further out but also because it is more anomalous.
FEBRUARY is expected to be much colder than average by 1.5 to 3.5 degrees with considerable snow or sleet and frequent easterly winds. This will develop because of massive blocking to the north of Ireland and the U.K. extending from Iceland to Scandinavia. There is some indication of a very severe period of wintry weather. This severe cold may last some time beyond the end of the month.
I may update this seasonal forecast if I have any further results from ongoing research, but this is the output of the current research model with some consideration given to the ice anomaly. I suspect it will intensify the pattern that would have existed otherwise, so I have tended to amplify the numerical output on either side of normal. Once severe cold is established over snow cover it is hard to dislodge during the depth of winter, but would also warn that February is the least reliable of the three monthly forecasts not only because it's further out but also because it is more anomalous.
Peter O'Donnell is a Vancouver-based climatologist who specialises in providing long-range forecasts for Ireland and Britain.
Friday, August 24, 2012
Accuweather Releases Winter 2012-13 Forecast For USA
Following a snow drought during winter 2011-2012, the mid-Atlantic and southern New England will get a snow dump this winter. That is according to Accuweather in its provisional Winter 2012-13 Forecast for the United States.
UK August Bank Holiday Weekend Weather
With people having time off and travelling around the country, the weather will, as always, play an important part for those planning on heading out and about.
Thursday, August 16, 2012
Peter O'Donnell's Long Range Weather Forecast For Britain
TODAY ... Scattered morning showers more likely in Wales and western Scotland, afternoon thunderstorms in a few spots but some sunshine and highs near 23 C away from cooler west-facing coasts.
Tuesday, August 14, 2012
WEATHER ALERT - Summer Storm, Wednesday 15 August 2012
ALERT for storm force winds with hurricane force gusts in exposed locations and very heavy rainfalls sweeping north tonight and lasting much of tomorrow (Wednesday, 15 August 2012), with some blustery squalls embedded.
Tuesday, February 21, 2012
First Signs Of Spring This Week
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| GFS forecast for 850 hPa (1,500 m) temperature for 12UTC Thursday. Image courtesy of www.ogimet.com. |
As a very mild meteorological winter comes near an end we are set to see some very mild days in the run up to March. Snow-lovers look away now.
February is a month that can produce some of the coldest weather of the season, but this month has not lived up to that title, and the past seven days have seen mean temperatures running from 1 to 3 °C above average. With the Azores high sitting nearby, mainly westerly winds have kept cloud cover enough to prevent some of the harsh frosts that can occur during this month, and the rest of the month should see mild temperature push that warm anomaly up further.
Today (Tuesday), the mercury rose above 13 °C in the northwest, with Finner's 13.1 °C its warmest day since December 26th's 13.4 °C. The coldest station was Knock Airport at 9.8 °C.
1 Finner 13.1 °C
2 Oak Park, Carlow 12.9 °C
3 Shannon Airport 12.8 °C
4 Mullingar 12.7 °C
5 Dublin Airport 12.6 °C
6 Gurteen 12.6 °C
7 Casement Aerodrome 12.5 °C
8 Sherkin Island 12.3 °C
9 Malin Head 11.8 °C
10 Ballyhaise, Cavan 11.7 °C
11 Valentia Observatory 11.7 °C
12 Belmullet 11.2 °C
13 Claremorris 11.2 °C
14 Roches Point 11.1 °C
15 Cork Airport 10.5 °C
16 Johnstown Castle 10.5 °C
17 Mace Head 10.1 °C
18 Connaught Airport 9.8 °C
With a warm southwesterly airflow for the rest of the week temperatures will remain well above average. Thursday looks like being the warmest day of the week, with 15 °C looking likely in some areas of the midlands and south, and even above 16 °C possible in the lee of higher terrain. With the sun's rays now back as strong as they were in mid-October, any breaks in cloud could make things feel very spring-like away from the stiff southwesterly breeze.
It looks like a brief cooler interlude through Friday before milder air returns over the weekend, and there is the chance of a repeat of this Thursday's temperatures early next week.
Monday, November 15, 2010
Winter 2010-2011 Weather Forecast For Ireland
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.
Monday, November 8, 2010
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