179 replies to this topic

[THE EYE IN THE SKY]

Rather than using graphs to look at the NAO i've taken the old fashioned approach of looking at the actual recorded SLP over Lisbon & Reykjavic.

Recorded SLP in Lisbon on the 1st Feb was 1019mb. Recorded SLP in Reykjavic on the 1st Feb was 1014mb. Although very little difference with pressure, due to being slightly higher over Lisbon suggests to me the NAO was neutral. At no stage during Feb so far has pressure ever been higher across Iceland compared to Lisbon.

Here are a few more interesting stats from these areas.

Across reyjavic this winter the SLP has often been around or below 1000mb with the exception of a few days recently when the pressure rose to 1025mb. See diagram below.



Across Lisbon the SLP has often been around 1025mb with the highest recording being 1036mb and the lowest at 1017mb. See diagram below.



If you live in NW England, SW England, Scotland, Ireland, Wales and you're wondering why this winter has been such a disappointment then your answer lies above!

Edited by THE EYE IN THE SKY, 14 February 2012 - 18:15 .

[Bristle boy]

A bit early yet to pass judgement on GP's winter forecast in my view, as Winter hasn't finished.

Seems to be pretty accurate so far - December and January pretty much spot on - February good start, but looking shaky for remainder.

I think, generally, even though i believe it wasn't 'officially' published, the MetO has been pretty good as well.

Winter '11/'12 hasn't delivered in terms of 'wants' in these parts though - in fact poor from a snow perspective - come to think of it v poor!
Question for the more knowledgeable on NW - whatever has happened to those Channel Low events the South West used to see in many a winter? - sometimes only 1 or 2 each winter (and not every winter i know) but they weren't uncommon 25+ years ago. I've seen archive news stuff that documents these events as quite common from the 19th century and up to the 1980s.

[Seven of Nine]

IMO GP got December, January, and the first half of this month spot on, although the cold certainly wasn't as widespread as forecast. On a separate note the Strat thread has been a revelation this winter, and certainly highlights the importance of having stratospheric warmings earlier in the season.

[Glacier Point]

So here's the really interesting analysis so far.

The forecast was premised on the 2nd half of the winter being different to the first in terms of pressure and temperature anomalies, the first half forecast to be relatively mild with south westerly winds and lower pressure to the north, higher pressure to the south.

The second half was forecast to be colder with pressure higher to the north than normal and lower than normal (remember wind flow is relative between pressure differences) to the south with winds from the east.

So here we go.

1st half temperature and pressure anomalies



2nd half temperature and pressure anomalies



Striking don't you think ? The key question will be how much these will get eroded in the next two weeks. I would suggest that given the magnitude of both, they'll still be present by months end. Indeed, the current temperature anomaly for the UK suggests the southern half to be 5C below average.



It's interesting that during the December of 2010 there was some criticism that even though December was singled out as the month where below average temperatures were forecast, this failed to identify a huge negative anomaly. This February, I'm currently too warm against the -5C anomaly. So ironically a slighter mild period will do just the ticket. If February comes in below average (suggest more than 0.5C below average), with a pressure anomaly with high pressure over Scandinavia and lower pressure over southern Europe, that is all that will be required for the forecast for Feb to verify. Also note where the original forecast analogues suggested the cold air to come from and the difference across the UK north-west to south east.

THE EYE IN THE SKY, on 14 February 2012 - 18:13 , said:

Rather than using graphs to look at the NAO i've taken the old fashioned approach of looking at the actual recorded SLP over Lisbon & Reykjavic.

Recorded SLP in Lisbon on the 1st Feb was 1019mb. Recorded SLP in Reykjavic on the 1st Feb was 1014mb. Although very little difference with pressure, due to being slightly higher over Lisbon suggests to me the NAO was neutral. At no stage during Feb so far has pressure ever been higher across Iceland compared to Lisbon.

Here are a few more interesting stats from these areas.

Across reyjavic this winter the SLP has often been around or below 1000mb with the exception of a few days recently when the pressure rose to 1025mb. See diagram below.

Reyjavic.gif

Across Lisbon the SLP has often been around 1025mb with the highest recording being 1036mb and the lowest at 1017mb. See diagram below.

Lisbon.gif

If you live in NW England, SW England, Scotland, Ireland, Wales and you're wondering why this winter has been such a disappointment then your answer lies above!

Dave - you need to supplement your analysis with the mean pressure for each area and then the standard deviation for both data sets to work out the real value of the NAO, after all, pressure and wind flow is relative to areas of high and low pressure.

[Isolated Frost]

Good analysis there GP.

Btw for further reference do you have a link to that normalised GPH anomaly 65N-90N chart? Thanks.

[chionomaniac]

Stewart, I think that you have correctly predicted the pattern of winter so far and do not think that you need to spend so much time reasoning and providing a retrospective analysis whilst winter has not finished yet. If I remember rightly there are a lot of other forecasts that were well out before December was two weeks old.

[damianslaw]

Good analysis from GP - will we be treated to a spring forecast as well in the coming days?

[feb1991blizzard]

The main point here is that what ever little holes that can be picked in the forecast (which you are always going to be able to do with any seasonal forecast), it has been the most accurate out of all the ones for this winter that i have seen, added to the fact that last winters was also very good, and the fact that the MO refuse to publish a seasonal forecast anymore, which with all the money and resources at their disposal must suggest that seasonal forcasting is still very difficult and in its infancy, then i have to say hats off to GP, quite a staggering effort really, especially to predict exactly where and when blocking would occur (backed up by sound reasoning), the fact that it didnt end up the dream Easterly from an IMBY perspective doesnt detract from how good a winter forecast it was, and as you say GP, its ironic that a spell of mild muck now will mean that your temperature anomaly prediction will be even more accurate than it would of otherwise of been, many thanks for sharing your knowledge of teleconnections and the stratosphere and same goes for chionomaniac.

[BLAST FROM THE PAST]

jethro, on 14 February 2012 - 17:38 , said:

Blast - when you edit your posts to answer subsequent questions, it all gets a bit messy and confusing. It reads much better for everyone if you respond with a separate answer, otherwise the questions I, or other people ask are left hanging in mid-air.

Editing is needed sometimes, depends what computer set up one is at. I too think GP doesn't need to explain too much at present....although it isn't as accurate as some are proclaiming as for me Jan anomalies according to GP's post seem a wee bit different and are worth looking at again as its interesting how it didn't fall into line...why?. Most accurate thus far? Could very well be/probably.....top effort


BFTP

Edited by BLAST FROM THE PAST, 14 February 2012 - 23:14 .

[johnholmes]

BLAST FROM THE PAST, on 14 February 2012 - 23:06 , said:

I too think GP doesn't need to explain too much at present....although it isn't as accurate as some are proclaiming. Most accurate thus far? Could very well be.....top effort


BFTP

have a look at my quick summary of the lrf issues last autumn BFTP-you will see GP is way ahead of anyone else even if the 2nd half of February turns out not as his forecast suggested

[BLAST FROM THE PAST]

johnholmes, on 14 February 2012 - 23:13 , said:

have a look at my quick summary of the lrf issues last autumn BFTP-you will see GP is way ahead of anyone else even if the 2nd half of February turns out not as his forecast suggested

Indeed John, I'm clearly not disputing that GP's forecast is about the best, but its going very wrong now and Jan isn't synoptically as forecast? Why?...and why has the warming in the stratos NOT provided the blocking anticipated. Reasonable non confrontational questions...even the best has / is failing /breaking down. Let's see if these can be answered over time

BFTP

[Osbourne One-Nil]

The things I like about GP's forecasts are that they're clear, concise and unambiguous. I also like how he lets the forecasts stand on their own feet, doesn't spin them to his advantage, and doesn't gloat when he gets things right.

[THE EYE IN THE SKY]

chionomaniac, on 14 February 2012 - 21:29 , said:

Stewart, I think that you have correctly predicted the pattern of winter so far and do not think that you need to spend so much time reasoning and providing a retrospective analysis whilst winter has not finished yet. If I remember rightly there are a lot of other forecasts that were well out before December was two weeks old.

I do agree GPs forecast has been the most accurate out of all the LRFs I have read. However whilst Dec, Jan and the 1st week of Feb appear spot on, the model output at the moment for the medium range appears to spoil GPs forecast.

Sorry if im coming across as argumentative but im a little frustrated at the moment and I shall explain why. I will add my post is on topic because im discussing the rest of Feb which is related to GPs winter forecast.

Only recently I was accused of being biased due to my negativity of the model output because some suggested I was only referring to my region. Here is a selection of posts and my response.

Glacier Point, on 12 February 2012 - 09:19 , said:

Our ridge to the west is replaced with a trough and heights build somewhat over NW Europe. Note that the anomalouse ridge over NW Russia is persistent (this has been an omnipresent feature this winter) and shifts its position west. That is a good signal for easterly winds to re-establish over Europe.

The next move for angular momentum looks downward, and we should see the models start to play catchup in building heights to our NE and possibly north towards Iceland, particularly as AO and NAO variables look to be near average values.

THE EYE IN THE SKY, on 12 February 2012 - 10:04 , said:

Trouble is though GP any NW,ly looks to be brief before being replaced by a W,ly flow. Im not sure even below average conditions would occur because upper temps during this NW,ly phase appear to be only around -5 to -7C and due to the time of year I would expect max temps to still reach between 4-7C.

johnholmes, on 11 February 2012 - 12:37 , said:

I think what we should all try to do, regardless of our geographic position in the UK, in this thread is try NOT to view life out of our own window, there are regional threads where discussions of the model outputs and how it may affect our area san be had. Surely the model thread is for UK wide; fine to comment on specific aspects but its not fair to do a summary from a local point of view.
My area has had one of the coldest starts to a February in a long time, better than a few years ago, and I have had a snow cover for 8 consecutive days(7 mornings). Folk further north and west have not.
So a less biased view folks if possible please?
IF the models are correct then obviously northern areas will do better than southern areas but its a case of swings and r-a-bouts in my view.
Certainly the 6-15 day 500mb charts show absolutely no sign of any mobile Atlantic weather which suggests blocking thus further cold shots seem probable.

THE EYE IN THE SKY, on 11 February 2012 - 12:58 , said:

I disagree with John because blocking doesn't look likely. When I refer to blocking I mean either a GH or a Scandi HP and neither are these suggested. If you have an Atlantic HP bringing NW,lys then with low heights across Greenland this cold is unlikely to be maintained.

Now considering the amount of flak I recieved and what the models are now showing you can see why im rather annoyed from a forecasting perspective. Like I say I take my forecasting seriously but it appears some are more impressed with technical posts rather than accuracy!

Edited by THE EYE IN THE SKY, 14 February 2012 - 23:46 .

[Solar Sausage]

BLAST FROM THE PAST, on 14 February 2012 - 23:06 , said:

Editing is needed sometimes, depends what computer set up one is at. I too think GP doesn't need to explain too much at present....although it isn't as accurate as some are proclaiming as for me Jan anomalies according to GP's post seem a wee bit different and are worth looking at again as its interesting how it didn't fall into line...why?. Most accurate thus far? Could very well be/probably.....top effort


BFTP

Because it's based on science, rather than wishful thinking?

[BLAST FROM THE PAST]

Solar Sausage, on 15 February 2012 - 09:58 , said:

Because it's based on science, rather than wishful thinking?

And there we have it, science isn't infallible....a trifle condescending too? There have been some decent efforts around so they're all wishful thinking....hmmm


If one reads the LRFs again it would seem that Feb is falling more in line with RJS

BFTP

Edited by BLAST FROM THE PAST, 15 February 2012 - 12:23 .

[johnholmes]

BLAST FROM THE PAST, on 14 February 2012 - 23:20 , said:

Indeed John, I'm clearly not disputing that GP's forecast is about the best, but its going very wrong now and Jan isn't synoptically as forecast? Why?...and why has the warming in the stratos NOT provided the blocking anticipated. Reasonable non confrontational questions...even the best has / is failing /breaking down. Let's see if these can be answered over time

BFTP

so he gets Dec and Jan correct, the first 10 days of February correct, leaving, unless my maths is dodgier than I thought, about 19 to go which may well be wrong and its a wrong forecast!
A touch more dificult maths, 71 days correct out of 91 makes about 79% correct and its judged as not good enough forecast-oh well you live and learn.
I feel quite chuffed if I can regularly get about 70% correct in a forecast out to day 20 let alone day 91!

[BLAST FROM THE PAST]

johnholmes, on 15 February 2012 - 13:56 , said:

so he gets Dec and Jan correct, the first 10 days of February correct, leaving, unless my maths is dodgier than I thought, about 19 to go which may well be wrong and its a wrong forecast!
A touch more dificult maths, 71 days correct out of 91 makes about 79% correct and its judged as not good enough forecast-oh well you live and learn.
I feel quite chuffed if I can regularly get about 70% correct in a forecast out to day 20 let alone day 91!

Look at post 140 by GP, the air pressure anomaly and temp between forecast and observed are different. So how is that correct? On that individual post January is not anywhere near as being right or spot on. Sorry, a very good forecast thus far with good overall rhythm is my verdict thus far.

BFTP

Edited by BLAST FROM THE PAST, 15 February 2012 - 16:22 .

[johnholmes]

I am not getting involved any further, folk can see who wrote what and how I marked it including your own post months back and how I marked it.
Time to move on in my view.

[DiagonalRedLine]

Feel like I've learnt a bit of a lesson from all of this - not to take forecasts from those who seem to over-hype them a bit (such as James Madden), too seriously.

Back in October and November I saw how the forecaster mentioned there being widespread snowfalls and cold weather for November, December, January and February. At first (and because of hopecasting-wise), I thought it was going to be right. But when I saw that November was not quite panning the way he predicted, I was beginning to lose a bit of faith with his forecasts. I then thought I would see how Dcember pans out before making any conclusions. Although there had been some snowy weather for North-Western areas for the first part of the month, I still feel it wasn't going the way he predicted.

While this was happening, I remember reading some great posts from Glacier Point who, if I rememebred correctly, expected the blocking to the East during November to be hard to shift. This, off course, seemed to be the case, and then he predicted the CET in December to be around average, which also seemed to happen, although perhaps the cool/cold spell in early December was probably under-estimated just a slight.

Though it's true Glacier Point may have got one or two elements wrong with his forecast, I think compared to some other Winter forecasts I have read from the net, I would say he has been pretty accurate so far. I know it wouldn't be the end of the world he had got his forecasts wrong as you can learn from errors anyway. But one particular reason I now take his forecasts more seriously (and I wish I did in the first place, although amazingly I took much notice of his Summer forecast last year) is thanks to his informed reasonings as to why the weather and pressure systems behave the way they would - although I admit, sometimes, I find his post a tad too technical (but I think this is due to my lack of understanding, and the way I process information).

I suppose, to be fair, I think it would obviously be impossible for a Long-Range forecaster to get the weather 100% correct. Even within 24 hours, for example, a Low Pressure system could end up tracking 20 miles further South than what was modelled/predicted.

[Dorsetbred]

Does this still need to be "pinned" or can it now die a slow death as it descends the threads, given we are past the season and all discussion has now ceased for well over a month?

Edited by Dorsetbred, 05 April 2012 - 05:00 .