Rjs And Bftp Winter 2010/11 Lrf

[Roger J Smith]

I think it may seem more accurate to me than to some of you because I am also watching my North American LRF on a daily basis and it is verifying well this month with colder than normal gradually spreading from central to eastern regions. Places like Boston are now near normal but had two very mild days to start the month, have been modified cold ever since. A little further west, that mild spell was less of a factor and the month is about -2 to -4 F at present. This is somewhat against the run of standard La Nina forecasts, so I'm happy with that, also with the extreme cold over Yukon southeast into west-central Canada. And I'm even happier not to be included in it by a stroke of luck we have managed to stay mild most of the time despite the near-absence of strong ridges, just the wavelength being pulled fairly long by having that big block sitting around well to our north.

The January UK forecast so far suffers mainly from trends all coming and going a bit early, it's not so far off that I feel like it's a flawed model, after all we don't trash a day after tomorrow forecast if a cold front comes through three hours early and that's about the scale of this forecast error from sixty days. The mild spell was predicted which given the predominant bias to cold in our forecast is a good result within a week -- it came in around the 12th and lasted to about the 17th, was supposed to be keyed to the northern max (17th) and full moon (20th) which often show up in January as temperature peaks, even in the analogue set I studied for this LRF. So I will have to think about why that has taken place and why the second long-duration cold spell of the winter season (lumping the first two into part I) may also start up a bit early.

I was saying to Fred off-line that one forecast error is simply an editing and structural error, we basically say nothing about the last ten days of January except what you can infer from them being between a very mild week and a very cold month. However, I have posted thoughts since then which were still quite long-range if not technically part of the forecast to be validated. Also you have the agenda buried back in an early part of this thread showing the energy peaks and these have been very, very close to a full verification for North America's timing line one, as I'm showing in a thread here:

http://www.americanwx.com/bb/index.php?/topic/7018-major-east-coast-snowstorms-and-lunar-cycles/

This is a fairly complex piece of work but if you want to skim past all the historical storm data you should look at post #15 where I posted the storm agenda for timing lines (it applies to all) and have been editing in the actual results as we go along. Timing line three for your reference runs NW-SE through Valentia Ireland into central France. There has been a tendency most of this winter, until the recent mild spell, for the active events to cross timing line three in France or even east of Spain, but in the past week the events have been on a more normal Atlantic track. Looks like the track is shifting back south again.

I really think almost anything could happen in February, but severe cold seems the most likely bet because of the continued low energy flow combined with the tendency we've seen all through January for westward height shifts in eastern Russia. The Siberian high has now pushed its cold air west of Moscow and almost to the Baltic, so is getting close enough to start interacting with any blocking that does either continue or redevelop.

I will note that if February has any milder weather it would likely come around the 15th to 20th to coincide with the N Max and full moon events. A strong block could dampen even these events but it would not surprise me if February started very cold, had a brief breakdown to mild, then went back to very cold lasting to about 10 March.

And note (this from another discussion on here) I have 4-5 March, 19-20 March and 3-4 April down for stormy periods and the latter two could bring heavy rains and strong winds. The first of these three could still be in the colder period and might be a late season snowfall event.

My feeling is, this is turning into an exciting finish to the winter season with a number of reasonably good forecasts out there and a lot to play for in terms of ultimate bragging rights but everyone concerned should feel some justified pride in having put forward a good forecast and made the full effort -- I think it should be mandatory to post an LRF to comment on other LRFs -- that would soon change the tone I believe.

[Bristawl Si]

I think it may seem more accurate to me than to some of you because I am also watching my North American LRF on a daily basis and it is verifying well this month with colder than normal gradually spreading from central to eastern regions. Places like Boston are now near normal but had two very mild days to start the month, have been modified cold ever since. A little further west, that mild spell was less of a factor and the month is about -2 to -4 F at present. This is somewhat against the run of standard La Nina forecasts, so I'm happy with that, also with the extreme cold over Yukon southeast into west-central Canada. And I'm even happier not to be included in it by a stroke of luck we have managed to stay mild most of the time despite the near-absence of strong ridges, just the wavelength being pulled fairly long by having that big block sitting around well to our north.

The January UK forecast so far suffers mainly from trends all coming and going a bit early, it's not so far off that I feel like it's a flawed model, after all we don't trash a day after tomorrow forecast if a cold front comes through three hours early and that's about the scale of this forecast error from sixty days. The mild spell was predicted which given the predominant bias to cold in our forecast is a good result within a week -- it came in around the 12th and lasted to about the 17th, was supposed to be keyed to the northern max (17th) and full moon (20th) which often show up in January as temperature peaks, even in the analogue set I studied for this LRF. So I will have to think about why that has taken place and why the second long-duration cold spell of the winter season (lumping the first two into part I) may also start up a bit early.

I was saying to Fred off-line that one forecast error is simply an editing and structural error, we basically say nothing about the last ten days of January except what you can infer from them being between a very mild week and a very cold month. However, I have posted thoughts since then which were still quite long-range if not technically part of the forecast to be validated. Also you have the agenda buried back in an early part of this thread showing the energy peaks and these have been very, very close to a full verification for North America's timing line one, as I'm showing in a thread here:

http://www.americanw...d-lunar-cycles/

This is a fairly complex piece of work but if you want to skim past all the historical storm data you should look at post #15 where I posted the storm agenda for timing lines (it applies to all) and have been editing in the actual results as we go along. Timing line three for your reference runs NW-SE through Valentia Ireland into central France. There has been a tendency most of this winter, until the recent mild spell, for the active events to cross timing line three in France or even east of Spain, but in the past week the events have been on a more normal Atlantic track. Looks like the track is shifting back south again.

I really think almost anything could happen in February, but severe cold seems the most likely bet because of the continued low energy flow combined with the tendency we've seen all through January for westward height shifts in eastern Russia. The Siberian high has now pushed its cold air west of Moscow and almost to the Baltic, so is getting close enough to start interacting with any blocking that does either continue or redevelop.

I will note that if February has any milder weather it would likely come around the 15th to 20th to coincide with the N Max and full moon events. A strong block could dampen even these events but it would not surprise me if February started very cold, had a brief breakdown to mild, then went back to very cold lasting to about 10 March.

And note (this from another discussion on here) I have 4-5 March, 19-20 March and 3-4 April down for stormy periods and the latter two could bring heavy rains and strong winds. The first of these three could still be in the colder period and might be a late season snowfall event.

My feeling is, this is turning into an exciting finish to the winter season with a number of reasonably good forecasts out there and a lot to play for in terms of ultimate bragging rights but everyone concerned should feel some justified pride in having put forward a good forecast and made the full effort -- I think it should be mandatory to post an LRF to comment on other LRFs -- that would soon change the tone I believe.

Great post Roger - the detail is especially worthy in my book and i think it's great you're prepared to put in so much effort and post on NW. Cetainly one to watch for some of those dates - not too happy about the storm period around 19th-2oth March though - too close t Cheltenham week (horses) for me!

[BLAST FROM THE PAST]

Great post Roger - the detail is especially worthy in my book and i think it's great you're prepared to put in so much effort and post on NW. Cetainly one to watch for some of those dates - not too happy about the storm period around 19th-2oth March though - too close t Cheltenham week (horses) for me!

If it happens a couple days early then bet on the mud larks! [nice little tip there :smiliz19: ].

I am pleased at the way we have come out, coming out of this mild spell and how sluggish the Atlantic looks like becoming. This has encouraged me and consolidated confidence of calling Feb cold as the more sluggish the Atlantic the better the chance of that big Siberian/Russian HP backing further west and interracting with blocking this way. I have been watching it and as RJS has said it has backed west, indeed it can be readily sticking its nose westawrd on models...but at the moment it gets scissored away. But the more this building HP blocks the Atlantic, the more/better the chance we'll have a call from it.

BFTP

[Bristawl Si]

If it happens a couple days early then bet on the mud larks! [nice little tip there :smiliz19: ].

I am pleased at the way we have come out, coming out of this mild spell and how sluggish the Atlantic looks like becoming. This has encouraged me and consolidated confidence of calling Feb cold as the more sluggish the Atlantic the better the chance of that big Siberian/Russian HP backing further west and interracting with blocking this way. I have been watching it and as RJS has said it has backed west, indeed it can be readily sticking its nose westawrd on models...but at the moment it gets scissored away. But the more this building HP blocks the Atlantic, the more/better the chance we'll have a call from it.

BFTP

Nice one BFTP.

What's hacking me off in the Model Disc Thread is the number of posters who read the models right up to T384 as gospel - i prefer to read the thoughts of those who have the nous to call a trend and look beyond, say, chart T168 and then call their own forecasts rather than rely on charts past T168, for example, as exactly what's likely to happen.

I haven't got the expertise to try and make those calls but a number of you, like yourself, RJS, TEITS, Nick Sussex, Steve Murr have a go at interpreting 'beyond' what a model may be showing for say, T168 and further - i like that.

[yamkin]

I think it may seem more accurate to me than to some of you because I am also watching my North American LRF on a daily basis and it is verifying well this month with colder than normal gradually spreading from central to eastern regions. Places like Boston are now near normal but had two very mild days to start the month, have been modified cold ever since. A little further west, that mild spell was less of a factor and the month is about -2 to -4 F at present. This is somewhat against the run of standard La Nina forecasts, so I'm happy with that, also with the extreme cold over Yukon southeast into west-central Canada. And I'm even happier not to be included in it by a stroke of luck we have managed to stay mild most of the time despite the near-absence of strong ridges, just the wavelength being pulled fairly long by having that big block sitting around well to our north.

The January UK forecast so far suffers mainly from trends all coming and going a bit early, it's not so far off that I feel like it's a flawed model, after all we don't trash a day after tomorrow forecast if a cold front comes through three hours early and that's about the scale of this forecast error from sixty days. The mild spell was predicted which given the predominant bias to cold in our forecast is a good result within a week -- it came in around the 12th and lasted to about the 17th, was supposed to be keyed to the northern max (17th) and full moon (20th) which often show up in January as temperature peaks, even in the analogue set I studied for this LRF. So I will have to think about why that has taken place and why the second long-duration cold spell of the winter season (lumping the first two into part I) may also start up a bit early.

I was saying to Fred off-line that one forecast error is simply an editing and structural error, we basically say nothing about the last ten days of January except what you can infer from them being between a very mild week and a very cold month. However, I have posted thoughts since then which were still quite long-range if not technically part of the forecast to be validated. Also you have the agenda buried back in an early part of this thread showing the energy peaks and these have been very, very close to a full verification for North America's timing line one, as I'm showing in a thread here:

http://www.americanwx.com/bb/index.php?/topic/7018-major-east-coast-snowstorms-and-lunar-cycles/

This is a fairly complex piece of work but if you want to skim past all the historical storm data you should look at post #15 where I posted the storm agenda for timing lines (it applies to all) and have been editing in the actual results as we go along. Timing line three for your reference runs NW-SE through Valentia Ireland into central France. There has been a tendency most of this winter, until the recent mild spell, for the active events to cross timing line three in France or even east of Spain, but in the past week the events have been on a more normal Atlantic track. Looks like the track is shifting back south again.

I really think almost anything could happen in February, but severe cold seems the most likely bet because of the continued low energy flow combined with the tendency we've seen all through January for westward height shifts in eastern Russia. The Siberian high has now pushed its cold air west of Moscow and almost to the Baltic, so is getting close enough to start interacting with any blocking that does either continue or redevelop.

I will note that if February has any milder weather it would likely come around the 15th to 20th to coincide with the N Max and full moon events. A strong block could dampen even these events but it would not surprise me if February started very cold, had a brief breakdown to mild, then went back to very cold lasting to about 10 March.

And note (this from another discussion on here) I have 4-5 March, 19-20 March and 3-4 April down for stormy periods and the latter two could bring heavy rains and strong winds. The first of these three could still be in the colder period and might be a late season snowfall event.

My feeling is, this is turning into an exciting finish to the winter season with a number of reasonably good forecasts out there and a lot to play for in terms of ultimate bragging rights but everyone concerned should feel some justified pride in having put forward a good forecast and made the full effort -- I think it should be mandatory to post an LRF to comment on other LRFs -- that would soon change the tone I believe.

Roger J Smith what a great post. You and BFTP are a credit to NW with your LRF's At the Croydon Council an important memo has been released 'Double check grit/salt supplies'. This memo only comes out when there is a very cold period on the way. I believe the models are going to start showing tomorrow 'Wednesday' a much colder period on it's way to the UK.

[Alan Robinson]

Just out of interest, here’s how an accurate weather forecast for the period November 1^st 2010 to 18^th January 2011 would have looked for the Danish islands, 392 nautical miles across the North Sea from Scarborough.

NOVEMBER 2010

November is expected to display three distinct weather patterns.

Mild, maritime conditions will prevail for the first two weeks of November, with temperatures well in excess of normal. Depressions will approach southern Scandinavia both from the west and from the Mediterranean Sea, and towards the end of this period, a vigorous storm is expected to cross the United Kingdom and pass between Norway and Denmark.

The passage of this deep low will mark a significant change. Conditions are expected to become very quiet with slightly warmer temperatures than normal, until about the last week of November when extraordinary cold weather and snow will suddenly transform tranquil autumn into deep winter. Temperatures at the end of the month in Denmark will be the same as in Moscow.

DECEMBER 2010

December is expected to be severely cold, and may even become the coldest since records began well over 100 years ago. This will be the first time in 150 years that there occurs a white Christmas in two consecutive years.

The temperature and pressure patterns of November will be reversed, and from around 12^th December a steady decline in temperature will occur. Nonetheless, the month’s lowest barometer reading – though not very low - will occur on 17^th December, while on November 16^th, the month’s highest pressure will be recorded. Pressure will not “swell up over northern central Europe in the days before the full moon on the 21^stâ€, and there will be no “important storm event†in that connection.

This low pressure of the 17^th will occur in connection with a very extensive cold front laying almost east – west, from Ireland to Sweden, intensifying the harsh winter conditions all across western Europe. The sea will freeze between the islands towards the end of the month. Particularly, around Christmas, there will be severe snowfall with drifts disrupting road and rail traffic. On Bornholm, tracked military vehicles will be required to provide emergency services, and all normal activity on the island will come to a standstill.

JANUARY 2011

A slight thaw is expected around New Year, and from the second week of January, temperatures will rise to well above normal again. No sudden change of weather pattern is expected to take place around 12^th January, as happened around 12^th November and 12^th December.

Approaching the January full moon, a gradual cooling will occur to temperatures just slightly above normal.

OUTLOOK FOR JANUARY 19^TH TO MARCH 1^ST

?

[Interitus]

This will be the first time in 150 years that there occurs a white Christmas in two consecutive years.

Sorry that this is not really on topic but have to say that this is very surprising for Denmark if true.

[mcweather]

Hi RJS AND btfp.

I have followed your winter forecast with great interest and think you have caught the basic pattern of the winter very well. I wouldn't have expected any long range forecast to say we would have the coldest December for at least a hundred years because by their very nature they have to be lrfs have to be relatively broadbrush in their approach, going for periods of weather type.

What I am interested in now is how you see us getting from the current meandering high pressure impasse to the possible severe cold and snow you are suggesting as a possibilty for february. What do you see as the trigger for this and what do you feel we should be looking out for in the model output over the coming days if your february forecast is to come to fruition?

[Roger J Smith]

Interesting roundup for Denmark there, the Christmas high situation was certainly more home-grown than Scandinavian but at some point wasn't there a ridge connecting two highs? I don't remember the details. The storminess of the Dec 20-22 period was muted shall we say, probably a good thing given the synoptics, as the subsequent mild spell would have caused severe flooding if there had been tons of snow before Christmas.

To get from the current situation to severe and prolonged cold, you would need the following to happen -- walk out the door and stand outside for an hour. (this applies to about 75% of the UK and Ireland tonight).

But I am being semi-facetious there, without snow cover this high isn't quite "severe cold" especially now that all are hardened veterans of Dec 2010. So to get to the right synoptics, I think this high needs to hang around for a week to ten days, not sink, show some tendency to link to Iceland and/or Scaninavian centres, then probably for a longer-term lock-in, a linkage to retrograde high pressure from Siberia into Russia joining up with existing highs then to the north of the southern UK (not convinced this would be much further north than central Scotland).

I don't know how Fred sees it, but I don't envisage a total reload of the massive Greenland high or the December or a 1962-63 pattern, so much as what he was saying earlier, something like Feb 1942 or a weaker version (my words only here) of Feb 1947.

From my research, this was not a strongly backed call so much as perhaps the more likely of two outcomes, the other one being somewhat bland lower-latitude blocking and perhaps more of a southeast direction to the mean wind, but the two outcomes are not necessarily that different. I do hold out that a milder stormy interlude could interrupt cold around 15-19 Feb and perhaps to some extent resembling the now ended mid-January mild spell. The La Nina will have something to say about the total package and that would be its calling card. It could be that 2006 is becoming a better analogue as time goes on here, we have never since early November been running totally opposite to that winter season and so perhaps late Feb into early March could be the second most significant cold spell of the winter after the November-December freeze.

I would continue to be very surprised if severe cold does not return, but heck it's cold enough right now, I think I saw -6 C on a few hourlies in both Ireland and the U.K. Speaking of brutal cold, central North America is about to get hit by waves of severe cold and the winter is rapidly shaping up as among the coldest in many years, even December was frigid in many areas, but here on the west coast we have almost totally escaped with just two brief cold spells so far. It is not all that warm out today (3 C) but about to turn milder again.

[mountain shadow]

Thanks for the post Roger. I can't help but read between the lines though and feel your getting a bit nervous about your forecast for February?

Is this case? or are you still fairly confident?

[Alan Robinson]

Sorry that this is not really on topic but have to say that this is very surprising for Denmark if true.

The Danish Met Institute put it on their website. The Danish criteria for white Christmas is not snow laying over a certain proportion of the country, but snow falling. DKs climate is pretty much like Northumberland or eastern Scotland without the hills, except when the Scandinavian high sets in during winter and the sea in bays and between the islands freezes.

Edited January 20, 2011 by Alan Robinson

[Roger J Smith]

I'm always somewhat nervous about forecasts of all kinds beyond five days, we keep stressing that our track record is in the 60 to 70 per cent range right side of normal, so that opens up a lot of spaces where a forecast can be either wrong side of normal or not very close to actual values. I've also stressed on many occasions that the very best we can hope to do is grind out 1-2 per cent improvements each year which is perhaps a little less than the improvements from 2008 to 2011 so far, but not a lot less ... but on the other hand, I don't see any really obvious "uh-oh" signs in the complex pattern we have before us today, so I will stick to the plan and confirm also what was laid out here a few weeks ago about the period 20 Jan to end of Feb being generally cold.

For one thing, this current high is one stage removed from becoming a severely cold home-grown feature and perhaps already is in a few regions, by standards of most other winters this would be considered quite a cold day.

You veterans of 2010 probably find this somewhat tropical.

[BLAST FROM THE PAST]

I don't know how Fred sees it, but I don't envisage a total reload of the massive Greenland high or the December or a 1962-63 pattern, so much as what he was saying earlier, something like Feb 1942 or a weaker version (my words only here) of Feb 1947.

Yes 42 is the type of pattern/strength I still favour.

BFTP

[virtualsphere]

Yes 42 is the type of pattern/strength I still favour.

BFTP

These charts aren't too far apart:

The main differences being the strength of high pressure over the UK, and gradient of pressure over the Atlantic. Pressure also lower in Europe in the 1942 chart, though centred in similar places. I know it's the evolution that is important here though rather than one random set of charts.

[BLAST FROM THE PAST]

These charts aren't too far apart:

The main differences being the strength of high pressure over the UK, and gradient of pressure over the Atlantic. Pressure also lower in Europe in the 1942 chart, though centred in similar places. I know it's the evolution that is important here though rather than one random set of charts.

If one takes a look at Feb 42 ARCHIVE CHARTS one can see where I'm thinking towards re Feb and not Jan? Interesting point re the mild interlude Roger says, I think it could arrive a tad earlier like it did this month. Looking closer it would suggest that the coldest period will actually be the latter half. So pretty cold/mild blip/very cold bringing an overall cold to very cold month.

Re confidence of it coming off, well for me it has taken a little knock and it is up against the thoughts of some very good and respected forecasters.....but nothing has changed in the overall signal. Anyway it is what it is....we called it and must standby it.

If I do think it is going to be a blow out I will post that thought.

BFTP

Edited January 20, 2011 by BLAST FROM THE PAST

[geoffw]

can someone tell me what the weather like in feb 1942 and post some key weather charts from that month?

[Weather-history]

can someone tell me what the weather like in feb 1942 and post some key weather charts from that month?

Very cold with a CET of 0.1C

There was a February 1996 type snow event at the start of the month.

http://www.wetterzentrale.de/pics/archive/slp/1942/Rslp19420202.gif

Look at the anticyclonic block here

http://www.wetterzentrale.de/pics/archive/slp/1942/Rslp19420217.gif

[BLAST FROM THE PAST]

Very cold with a CET of 0.1C

There was a February 1996 type snow event at the start of the month.

http://www.wetterzentrale.de/pics/archive/slp/1942/Rslp19420202.gif

Look at the anticyclonic block here

http://www.wetterzentrale.de/pics/archive/slp/1942/Rslp19420217.gif

Cheers Kev.

Geoff go to datacentre and bottom right you will see chart archive. Find it all there on this site....saves cluttering up space.

BFTP

[Interitus]

The Danish Met Institute put it on their website. The Danish criteria for white Christmas is not snow laying over a certain proportion of the country, but snow falling. DKs climate is pretty much like Northumberland or eastern Scotland without the hills, except when the Scandinavian high sets in during winter and the sea in bays and between the islands freezes.

Sorry, I had to check this because it didn't ring true and it isn't snow falling like our white Christmas but lying snow. The DMI use a classification of a "nationwide white Christmas" generally meaning that more than 90% of Denmark is covered by more than a dusting of snow on 24 december - it is this that happened in consecutive years for the first time.

The DMI website shows for example that falling snow occurred in 1981 and 1982.

The same site give some statistics that maybe relevant on this side of the North Sea also -

Forecast for January 2011 - statistically speaking

After a temperature-related cold December, [as] in 2010, follows that statistically an average January in 50% of cases, in 35% of cases a cold January, and a warm January in 15% of cases.

[Alan Robinson]

The DMI use a classification of a "nationwide white Christmas" generally meaning that more than 90% of Denmark is covered by more than a dusting of snow on 24 december - it is this that happened in consecutive years for the first time.

Thanks for that, I must have had one too many bottles of my excellent pale ale, and put it back-to-front.

Indicentally, I'm going to stop quoting DMI, because their articles have a habit of disappearing from their website, such as the one around mid December that stated a mild period would set in just before Christmas.

[mcweather]

Some interesting signs from todays runs that as we enter the last full week of January that a gradual change to a colder evolution than has been shown recently, tentative signs that the PV may split and start pulling the high further north. From there all sorts of things could happen. Possibly even something along the lines of RJS AND BFTP's FEB forecast. Whatever happens it looks as though it will take place at a relatively sedate pace. Interesting if somewhat plodding chart watching over the coming week I thing however if I was BFTP or RJS I wouldn't be disappointed with tonight tonights output at all.

[mountain shadow]

Some interesting signs from todays runs that as we enter the last full week of January that a gradual change to a colder evolution than has been shown recently, tentative signs that the PV may split and start pulling the high further north. From there all sorts of things could happen. Possibly even something along the lines of RJS AND BFTP's FEB forecast. Whatever happens it looks as though it will take place at a relatively sedate pace. Interesting if somewhat plodding chart watching over the coming week I thing however if I was BFTP or RJS I wouldn't be disappointed with tonight tonights output at all.

I think they will be disappointed by this mornings run though. It is going to take a monumental shift for this forecast to come off now I would think. Not impossible, but very difficult to achieve.

[BLAST FROM THE PAST]

I think they will be disappointed by this mornings run though. It is going to take a monumental shift for this forecast to come off now I would think. Not impossible, but very difficult to achieve.

Indeed the time is approaching but do not take the models as gospel from t120 onwards, lots can and does change after that timescale. Look at this pretty cold easterly that has popped up....they took they tome to see that and 7 days prior it was an utter no no. Lets see where we are when we are very close or there....some chances still survive.

BFTP

[geoffw]

give it up blast ... your feb forecast is totally WRONG!!!

[Weather-history]

give it up blast ... your feb forecast is totally WRONG!!!

Unfortunately, geoffw, I do not have a time machine, February is still a week away for me.