LRF or attempting them

[phil nw.]

Thanks John-well presented as ever.

I do hope that forecast is correct.I`d love a bit of seasonal snow.

[PB22]

Thank you Mr Holmes, an absolute pleasure to read and I recommend this 100% to anyone who wants to learn about the future.

[johnholmes]

thank you mate, it might even be near to being correct, not that the GFS runs today, which I try to ignore, do anything to boost its credability.

Its a lot of work as your daily output is but its also fun and a great learning curve.

just wish I could get someone to do full checks on them rather than me although I do try to be as objective with them as I can.

[johnholmes]

Brief update No 39 for the period beyond Xmas over the New Year and beyond; 10-15 January

This was the text from the last lrf and similar to the previous issues from early in December.

SUMMARY

To me, ignoring the furore the recent GFS and ECMWF runs are creating, the overall patterns shown by other data continues to show a similar outcome to the last two LRF's. The actual date of onset probably still before the New Year.

FORECAST for 26 December- 2 January

On or about this start date the building blocks look like being in place for a fairly major development of high pressure, first over the Uk, then extending north east and linking with pressure rises to our north east to start with. As the period progresses the idea of this, after low pressure, perhaps more than one, has skirted around northern Norway, then the high seems likely to retrogress westwards with a fairly major polar outbreak. This probably happening just before the New Year. All areas will be in the 'cold' category, some in the north and east perhaps 'very cold', as compared to the values quoted at the start of this lrf.

Detail is not for an lrf but snow and frost will occur for many areas in this period; dry at first but becoming less anticyclonic and therefore rather more unsettled as time goes on. No major wind problems expected anywhere in the UK.

Well the above was posted almost a week ago and I see no real change in it. Yes the actual getting to the colder air, at height as well as at the surface looks like being a few days adrift, more like over New Year rather than before. But the overall trend into colder conditions is well set and about to start with the high being where it was predicted. Almost all the signals from all the sources I look at seem to suggest a similar outlook. Cold weather will predominate from just after Christmas until well into January. Slowly the upper air will become colder as will the surface. The 500mb anomaly chart issued by NOAA last evening probably illustrates this as well as any. Notice that it has started to shift the large +ve values north west of the UK. It has taken 7-10 days for this to start happening. –ve heights are again suggested for areas to the south and south west of the UK. Upstream over the States/Canada a large +ve area sits around 150 west with the 500mb trough still over much of north America. Other indicators also suggest this pattern is the most likely one well into January.

Just how long the cold will persist is problematical but certainly I would anticipate it could be beyond this lrf time scale. At some point we will get a milder interlude as the Atlantic pushes unsettled milder air north east into this cold block and it may temporarily extend over the whole UK. However cold looks to predominate. No lrf, can give details of precipitation this far out but it would be unlikely that most if not all parts of the UK will see snow at some point in this period. A northerly incursion seems very probable and at some point, a 'snow' event from milder air trying to push in from the south west is also a strong possibility. Frost will occur widely with few places not recording air frost during this period. The possibility of an ice day or days is fairly real it would seem.

I will do a full update on New Years' Eve for the period 9-16 January 2009

[Snowaddict]

Sounds great John and is certainly a great read.

Thanks a million.

[ukmoose]

You have stuck admirably to your guns John about the prospect for late December/early January for some time now.

Still looking good at the moment and I do hope you are right.

Great read anyway - thanks for all your long range input and for your continuous and sensible moderating voice of reason. A gentleman forecaster from the old school.

Happy Christmas.

[sunny scunny]

An excellent read john

[johnholmes]

You have stuck admirably to your guns John about the prospect for late December/early January for some time now.

Still looking good at the moment and I do hope you are right.

Great read anyway - thanks for all your long range input and for your continuous and sensible moderating voice of reason. A gentleman forecaster from the old school.

Happy Christmas.

thank you, that is very kind, I hope you have a peaceful and enjoyable Christmas and that the cold and snow arrives; judging by the number on site, as I type, well over 400, the 06z I've not seen yet, must have been good!

John

ps

the current average for 36 of the lrf's done since early February is 72% for the first half of their period and 62% for their second half, so fairly encouraging and worth continuing, hopefully with an improving average in 2009. It would be good if someone would undertake to do the marking?

[Mark Bayley]

A very good read John, as always

[johnholmes]

sorry this will not get done until tomorrow morning - family commitments through yesterday and today. All, or almost all the data is in, but not got more than a draft ready; I only give a low weighting to the routine 4x or 2x model outputs anyway.

[johnholmes]

No 40 issued Wednesday 31 December for the period 9-16 January

not issued until noon on Thursday 01/ January 2009-01-01

Average afternoon temperatures for the uk range from 6C for all Scotland to 7C for Northern Ireland and 6C for northern England rising to 7C for most other parts of England and Wales and 8C for the far south west.

Taking the usual list of drivers/teleconnections/charts with the Stratospheric being dealt with after the general summary

ENSO

ENSO update 18 Dec

Currently, the models see very little possibility of developing El Niño conditions, but indicate probabilities of slightly less than 50% for La Niña conditions. The sub-set of the models that see the possibility of developing La Niña conditions are primarily dynamical models, 3 out of 23 of which even indicate moderate La Niña conditions (anomalies stronger than -1.0C). All things considered, during the Dec-Jan-Feb season there is a 48% probability for La Niña conditions, 52% probability for ENSO-neutral conditions, and a near-zero probability for El Niño conditions.

Other links from the Equator/Tropics

There is some evidence that tropical activity is aiding the probable development/continuance of high pressure over middle latitudes, so parts of the Atlantic may see high rather than low pressure dominating?

AO

I've put in 3 here over the past week or so to show the changes.

NAO

Similarly with the NAO

Both of them show a rise in the second half of their forecast period in all 3 cases.

NOAA forecast comments out to 14 days

Throughout the past week they have almost all the time preferred the ECMWF output to GFS, both operational and ensemble, with GFS relegated at times to almost a 'non role.

Their overall assessment from 31 December said,

'8-14 DAY OUTLOOK FOR JAN 08 - 14 2009

FOR THE PAST FEW DAYS, THE ENSEMBLE MODEL SOLUTIONS FOR THIS PERIOD HAVE BEEN GENERALLY CONSISTENT WITH THE EXPECTED 500-HPA HEIGHT PATTERN THROUGH THIS PERIOD, AND THIS REMAINS THE CASE TODAY. THE ENSEMBLE MODEL CONSENSUS CONTINUES TO FORECAST A MEAN TROUGH OVER THE EASTERN CONUS, A BUILDING RIDGE OVER THE WESTERN CONUS, A TROUGH ENTERING WESTERN ALASKA AND A DEAMPLIFYING RIDGE OVER THE FAR NORTHEAST ATLANTIC.

The comment about the north east Atlantic being of immediate interest but note also the pattern expected over north America for its effects over our part of the world.

NOAA 500mb anomaly charts

Again showing a couple, one from early in the assimilating data period and one last evening. The one on the left for the period 6-12 January and on the right for

I made this comment when running the various charts back and forth before this lrf

the ridge in far west has moved from 160+ to about 130-140 between 25-31 December and 07-13 January predict!

the ridge (+ve area) near the UK has gone from over uk to ne Canada in same time scale.

ECMWF/GFS 500mb anomaly charts

Once more two to compare; the left hand one was valid for 2 January so is the nearest to what any chart should be showing now, so I've dropped the GFS at 06Z this morning alongside it.

The block to the north/north west of the UK shows up reasonably well as doe the areas of surface low pressure beneath the –ve areas on the 500mb anomaly chart ( over The Atlantic and off the eastern seaboard of the States/Canada.

Below is its predict from 31 December; and the change, from that above (both ECMWF and GFS) being predicted for 10 January is clear to see. The similarity between the latter NOAA and the ECMWF on its latter one is also quite clear.

Comments on the daily model output from GFS and ECMWF

When assessing these I rarely give more than a slight weighting to them, and then, only if they have shown a good deal of consistency over the past week. So I think it will be no surprise to read I attach little weighting from them to this lrf. ECMWF has been rather more consistent than GFS but not by that much.

Summary

Putting the above together and the general 'signal' is reasonably firm from most, but as almost always not entirely. The AO and NAO along with both sets of 500mb anomaly charts seem in broad agreement. However, the ENSO and Tropical signals seem somewhat different in their suggested outcome for weather patterns for the north Atlantic/Europe/Scandinavia.

Forecast

This is for the period 9-16 January and the last one (No 39), a brief outlook to 10-15 January, continued with the cold theme and it turning to a flow more from the north than it had been. In this we look to be heading for the transition zone from a cold set up to one less so.

There are two schools of though over how this may happen. One that suggests the Atlantic will become the main player, so milder cyclonic. The other suggesting it will become another anticyclonic set up with a surface high somewhere close by or over the UK.

Difficult but I would favour the former by, about, 60:40, so its far from clear.

In terms of weather then snow seems likely as the milder air slowly works its way east and cold or very cold to start with, so frosty for central and eastern areas at first. Forecasting amounts over a week down the line is impossible so I'm not even going to attempt it. Milder I would imagine for all by the period end and possibly fairly windy for the more northern and north western areas. Further south this effect less marked as I see surface high pressure over the near continent.

Further ahead with the Stratosphere data

The 30mb temperature plot has recently shown the largest and longest sustained fall thus far in the winter season. As a total beginner this suggests to me that we will have a much more unsettled spell of weather once the cold breakdown, indicated above, gets going, probably lasting towards the end of January.

Next lrf will be issued Wednesday 7 January to cover the period 17-24 January.

I'll try and verify this one on 9 and 16 January.

added 2 January 0930

There is no doubt that the breakdown is being predicted quite well. Some doubt over just how it will occur but occur it will

.

Some of the teleconnections have been showing this as likely to begin by between 10-12 January for some time; my very amateurish reading of the 30mb temperature profile, the NOAA 500mb anomaly charts, the ECMWF and GFS similar charts, and the developing signs on both the AO and NAO. All of these suggest about the same dates to me, 10-12 January. This is several days earlier than I first thought.

Looking at just the 30mb temperature profile it would suggest, once started, it may last until almost the end of January, indeed the length of the more mobile westerly is uncertain at this time.

[johnholmes]

No 41 issued Wednesday 7 January for the period 16-23 January

Average afternoon temperatures for the UK range from 6C for all Scotland to 7C for Northern Ireland and 6C for northern England rising to 7C for most other parts of England and Wales and 8C for the far south west.

The usual check through the various links

ENSO and Tropical

There has been no update since the last message on 18 December, the final sentence quoted this; 'All things considered, during the Dec-Jan-Feb season there is a 48% probability for La Niña conditions, 52% probability for ENSO-neutral conditions, and a near-zero probability for El Niño conditions. '

There is nothing I have seen that really alters anything around the Tropics since my last lrf. Minor changes yes, but nothing that causes me to comment in here.

AO

These have returned to +ve over the period as the two below show and are predicted to remain largely +ve although with a return to around zero.

NAO

This is also showing a marked trend towards a +ve sign, the first since the mid December period

In both the AO and NAO cases the general trend has been consistent though the past week.

NOAA comments

This is their issue this evening and is pretty similar to what they have been saying since late on last week before the weekend. Marking is now 4/5 for the whole period

8-14 DAY OUTLOOK FOR JAN 15 - 21 2009

THE GFS AND CANADIAN ENSEMBLE MEAN PROGS INDICATE A SLOW PROGRESSION AND

DEAMPLIFICATION OF THE CIRCULATION PATTERN FROM THAT FORECAST FOR THE 6-10 DAY PERIOD

NOAA 500mb anomaly charts

The first one show the 8-14 day period forecast for 7-11 January; it has the UK still (just) on the forward side of the upper ridge, the 'cold' side. The one on the right (above) is the NOAA prediction of 500mb flow and the anomalies for 15-20 January. As for the UK area note that the blocking high to our north west has disappeared. The one showing to the south west is not the same one having moved. It is a new development, the Azores upper ridge appearing. Over in the far west both the upper ridge in the far west and the upper trough in the east have tended to amplify a little, not by a lot though. They have also shown some eastward movement, again not a lot though.

They too, as with the AO and NAO seem to me to be believable consequential changes one would expect within the time scale of 7 days from the issue of the left hand one to the right hand one.

ECMWF and GFS similar charts (but only out to day 10-NOAA goes out to day 14)

The left hand chart is for 12 January; both ECMWF (lhs) and GFS show a similar +ve anomaly over the far west of USA. Less so for the +ve area over Canada and Greenland, but have a +ve area, especially ECMWF predicted over the central/southern area of the Atlantic.

Remember this is a prediction made 2 January, and if anyone looks at ECMWF GFS or UK Met you can see its not that far from their current T+144 ideas.

The one on the right is for 17 January (issued 7 January=this morning); both to me suggest events over USA much as the NOAA version shows, both +ve and –ve areas showing similar changes, a somewhat more ridge/trough development. In the UK area and they have some differences but not large ones. Both show a largish +ve anomaly west south west of the UK with –ve to the north west and both suggest a 500mb flow west of north. Again these charts show reasonable continuity over the past 7 days.

General GFS and ECMWF 4x and 2x daily comments on them

Remember these comments are for the period 16-23 January not for the T+48-120 period. These changes, predicted recently by both ECMWF and GFS were anticipated in earlier LRF's, with a date around 10-14 January being suggested.

For 16-23 January the two main models are, as they often are at this range, somewhat uncertain, even at T+240 (the furthest range for ECMWF). Having said that, to be fair to them both, they have for most of the runs over the past 7 days tended to suggest a westerly flow, sometimes more cyclonic, sometimes more anticyclonic, but generally with a lean towards Pm rather than Tm air (Polar rather than Tropical).

Summary

Not conclusive support from the various areas but to me tending towards a similar solution.

Forecast

By the start we will obviously be clear of the present long lasting cold block with a more mobile flow from the west. Windy at times in the west and north and also unsettled again especially the further north you live in the UK. Precipitation totals away from the south east nearer to the norm for this time of the year. Temperatures varying a shade below to a shade above average for most of the time. Behind one, possibly two of the lows then a briefish spell of colder weather with hill snow, possibly for some lower ground briefly, again for areas in the northern half chiefly. Frost about average but certainly less so than recently especially for the south.

By the end of the period then the signals seem to me even more mixed; see my comments below on the 30mb temperature pattern.

30 mb temperature pattern

The first one on 2 January and the right hand one for yesterday. The fall below average is the largest this autumn/winter period; its all very new to me but I would suggest that any major northern blocking is not likely, using this as a guide, before early February. This is of course only one factor and it is possible for it to be over ruled by enough of the others. I think it's a very long shot, no more than 15-20%, but it is just possible towards the end of January that the Azores high may have a ridge over the UK which, if events upstream are suitable; trough/ridge pattern, might just allow a build into Scandinavia.

The is a very small chance, looking at the evolution of the NOAA 500mb charts of a ridge moving east out of the USA and possibly briefly linking with any hint of rising pressure over the far north but I would rate that at less than 20% currently.

The next issue will be No 42 on 14 January for the period 23-31 January.

No verification as I'm away, and the next routine lrf is due Wednesday 11 February. I will try and do brief updates on 19 January and 6 February.

[Snowaddict]

A very well explained forecast as ever John, and an excellent read.

Very well put together.

Looking forward to the next update.

Rgds, SA.

[johnholmes]

No 42 issued Wednesday 14 January for the period 23-31 January

Average afternoon temperatures for the UK range from 6C for all Scotland to 7C for Northern Ireland and 6C for northern England rising to 7C for most other parts of England and Wales and 8C for the far south west.

The usual check through the various links

ENSO and Tropical

This is the issue on 12 January from NOAA

•Atmospheric and oceanic conditions reflect La Niña.

•Recently, negative equatorial SST anomalies have strengthened across portions of the central and eastern Pacific Ocean.

•Based on recent trends in the observations and model forecasts, La Niña conditions are likely through early 2009.

AO

Over the past 7 days the first dip has changed somewhat with the second dip showing a slightly more definite trend down.

NAO

Has shown a tendency over the same period to trend down towards the end.

NOAA comments

They have tended to slowly back some retrogression of the western +ve area and high over the far west. But are unsure on how certain this is and have marked their level of trust down over the period its now only 2/5 into day 14 from Tuesday (day 14=27 January). Overall they seem content with the ridge position but uncertain what may happen downstream over their area let along further east.

NOAA 500mb anomaly charts

Three charts below, from top to bottom; 15-21; 18-24; and 20-26 January

These show how the +ve area and upper ridge have steadily been predicted to edge north west; the upper trough over the east of the states has changed orientation so that it is predicted by 26 January to be more east west towards the UK area (north of it), with the –ve area has transferred from fairly well west of the UK to just north of the UK. The effect is to veer the 500mb flow slightly to one just north of west.

ECMWF and GFS similar charts (but only out to day 10-NOAA goes out to day 14)

The first one below is for the 19 January and the second one for 23 January.

It shows how the flow has been predicted to alter over the states with some retrogression of the western upper ridge (much as in the NOAA charts) and the deepening and extension into Europe of the –ve area, again showing the slight veer of the 500mb flow to just north of west.

General GFS and ECMWF 4x and 2x daily comments on them

There have been the usual variations between the models and in their runs but overall they seem to have the 'message' of the summary below. With such cold air to the north and an active jet stream then the difficulties of trying to know just where surface centres will be has been amply demonstrated in my view.

Summary

Most signals, so far discussed, show a degree of similarity. A long 500mb flow from the states/Canada into Europe with little suggestion of any buckling over the past 7 days of forecasts in the overall upper flow. Following signals from around the Tropics both the AO and NAO are showing signs of turning more negative than for a little while. The one factor, albeit at a somewhat longer time scale, which does not fit this pattern is the 'short hand' method I use.

That is the 30mb temperature levels. They are further below the normal plot than at any time since we started looking at them way back in the autumn;

See below; the first onefor the 9th and the second one for the 13 January.

Again I stress trying to interpret this factor is a new departure for me. However, I would expect the effect of this to start having some effect before the period end of this lrf, and to continue for some time afterwards. Whether this effect can be 'masked' by the others mentioned above I am unsure, possibly so, at least at first.

Forecast

I see the fast flowing 500mb flow, just north of west, continuing, with jet strength at times from around 24000ft-40000ft. This will bring deepening depressions across the Atlantic and, slowly, with time, a touch further south. Temperatures will range from a bit below to rather cold at times in the far north to a bit above to slightly below in the far south. Temporary changes to milder air ahead of depressions for much of southern Britain. No real sign to me of a strong sustained northerly outbreak. There may well be temporary northerly or more likely north westerly flows behind lows but 24-36 hours duration only.

Snow will fall at times, especially on the western flank of lows from about the Midlands northwards, 200m in the south and more likely nearer sea level at times in the far north. Over the mountains of Scotland blizzard conditions are likely now and then.

Winds will be a feature across the country, strong to gale force at times with severe gales for the more north western and northern areas.

Frost, as a result of the wind should be no more than the average for this time of the year.

No full updates until about Friday 7th February – annual snow pilgrimage!

[J10]

Excellent as always John, i hope you have a lovely time on the piste.

[johnholmes]

ah, such a phrase Julian, a few beers after being on the left trouser leg, sorry piste - just make sure you send sub zero 850mb temps, 6 days unbroken sunshine then 1 day of heavy snow each week!

not much to ask for

[johnholmes]

A quick update on Monday 19 January to about 7 February

As is often the case there are conflicting signals from the different areas I look at.

The most notable I suppose is the 30mb temperature in the Stratosphere, see below.

In spite of various forecasts from different centres of an expected and fairly dramatic rise, following on from wind changes, so far, its stuck well below and showing little sign yet of a marked rise to even average.

From this, quick snapshot, and remember it is only one, I would suggest any significant northern blocking is unlikely this month and it may well be into the middle of February before we see any.

That is not to say that other factors cannot cause, at least, temporary blocking sufficient to give markedly deeper cold air from a northern rather than a western point. The fact that the fairly prolonged westerly (500mb) flow we are having, has given relatively cold conditions compared to previous westerly flows at this time of the year may suggest that the northern hemisphere is behaving rather differently than we have seen over at least the past 6-8 years.

Both the AO and NAO are predicted to show a dip towards zero see below, AO on the left NAO on the right, and this has been a consistent feature of them both over the past week or so

Both show a more marked fall today than previously although in line with what they have been showing over the past week. They are not in phase though one being about a week ahead f the other. The PNA is showing an overall fall through the same period to well below zero but shows some signs of recovery towards the end of the forecast period. This tends to tie in the, now, anticipated fall in both AO and NAO. Whether one is the result of the other I do not know. They could all be tied in with the forecast sharp rise in the 30mb temperature.

The 500mb anomaly charts have all continued to support the fastish 500mb flow over the Atlantic and this tending to look like a flow across much of north America of the same direction, that is becoming zonal over there away from the far west ridge over the north east Pacific. There are signs of a building ridge well north, from north Russia across over/north of Svalbard and in towards north east Greenland. Again this may support the idea of that 30mb rise in temperature?

Overall, through this month, apart from temporary northerlies to the rear of depressions I see no real deep cold northerly. Still rather below for most, away from the south of the UK, rather than above average values. In the south nearer average for more than half that time. Snow really in the main for hills and the northern half and also windy at times, again especially for the north and west.

Any real cold, northerly, from whichever direction either side of north (I have no real indication of which that might be if it happened) before the very end of this quick update and more probably after it.

The next full update I hope to do on Friday 6 February for the period 16-26 February

[J10]

The continued lack of any real northerly blocking is a big disappointment as we do well out of NNW winds, and this hasn't really delivered since the 2005-06 winter.

[johnholmes]

very interesting Phull770 but what has it to do with the thread title?

also attempting to open your link caused problems on my computer, anyone else?

[7andY]

very interesting Phull770 but what has it to do with the thread title?

also attempting to open your link caused problems on my computer, anyone else?

Have reported this guy for multiple postings...

[johnholmes]

This is the first lrf of the 09-10 season to me. I started them last year after skiing so this seems a good time to start with No 1.

No 1 Update from Friday 6 February for 16-26 February

The average temperatures for the country in February are: - 5C in the Northern Isles to 7C for most of Scotland, Northern Ireland and England, 8C for some of the cities and Wales and up to 9C for the south west.

As always taking the various factors in turn and showing what the latest comments are from the acknowledged experts along with the changes predicted between mid January and now.

Tropical data

The extract below is the latest NOAA comment re ENSO conditions

Atmospheric and oceanic conditions reflect La Niña.

•Negative equatorial SST anomalies persist across the central and east-central Pacific Ocean.

•Based on recent trends in the observations and model forecasts, La Niña conditions are likely to continue into Northern Hemisphere Spring 2009.

and below is the mid January IRI update

The most recent weekly SST anomaly in the NINO3.4 region is -1.1 C, indicating La Niña conditions in the tropical Pacific. What are the probabilities for developing a La Niña event (i.e. an "event" refers to La Niña conditions persisting for approximately 5 months) in early 2009? Persistent and large-scale easterly wind anomalies along the equator in the western-to-central Pacific since early October now appear to be coupled to changes in the upper ocean, but after two months of relative oceanic unresponsiveness. The thermocline, which constitutes the main element of the tropical Pacific system imparting ENSO predictability, is shallow in the eastern part of the Pacific, but deep anomalies in the west loom ready to reverse the current cooling.

It is possible that the negative anomalies in the east-central Pacific could strengthen to some extent as the recently stronger sub-surface anomaly structure influences the surface in the coming one to two months. However, as the ITCZ moves closer to the equator, the Trade Winds weaken and the seasonal warming of the eastern Pacific ensues, it will become more difficult for the atmosphere to maintain cold oceanic conditions. The models, both dynamical and statistical, suggest a tendency towards neutral conditions beginning from the first season.

Currently, the models indicate probabilities greater than 50% for La Niña conditions, and very little possibility of developing El Niño conditions for the coming season. All things considered, during the Jan-Feb-Mar season there is a 55% probability for La Niña conditions, 44% probability for ENSO-neutral conditions, and a near-zero probability for El Niño conditions.

AO

On the left side as it was around my last update – 18 January and on the right as of today – 6 February

NAO

similarly with the NAO, left shows 18 January and right as of today

30mb temperature profile;

mid January and on the right as of now

NOAA 500 anomaly charts

26 January-1 February and the latest for 14-20 February on the right

The +ve area is still sw of Alaska in the west; the other major +ve area has apparently moved in that time, to ne Canada with an extension now showing right out into the UK and towards Iberia. The main –ve areas are nw of Alaska into Mexico and off the eastern seaboard.

EC-GFS similar charts

NOAA comments

on wed=4/5 falling to 3/5 in 8-14 day period

8-14 DAY OUTLOOK FOR FEB 12 - 18 2009

THERE IS GOOD AGREEMENT AMONG MODEL SOLUTIONS FOR THE MEAN 500-HPA HEIGHTS

PREDICTED OVER NORTH AMERICA FOR THE 8-14 DAY PERIOD. MODELS AGREE THAT A

BUILDING HIGH LATITUDE BLOCKING RIDGE JUST WEST OF GREENLAND

and they say much the same tonight (Friday)

and their monthly output on 31 Jan

SAT JAN 31 2009

30-DAY OUTLOOK DISCUSSION FOR FEBRUARY 2009:

an extract at the end which may have some relevance to events in our area.

THE ANTICIPATED PHASES OF THE MJO DURING THE

SECOND HALF OF THE MONTH WOULD FAVOR BELOW-AVERAGE TEMPERATURES ACROSS MUCH OF

THE NORTHERN HALF OF THE CENTRAL AND EASTERN US. IN ADDITION, THE POTENTIAL FOR

AN EXTENDED PERIOD OF NEGATIVE AO CONDITIONS LATER IN THE MONTH IN PART

ASSOCIATED WITH THE RECENT SUDDEN STRATOSPHERIC WARMING FURTHER INCREASES THE

UNCERTAINTY FOR THE MONTHLY MEAN TEMPERATURE FOR FEBRUARY IN THESE REGIONS.

They are discussing the north and north east region of the USA.

Overall comments

Both AO and NAO are suggestive of a cold rather than a mild period. The tropical influences would also seem to support this idea. There is still some doubt it seems to me as to how much if any milder air will occur in the UK area.

Forecast for the period 16-26 February with a quick overview, first of all, of what I think will be the pattern up to the start of that period.

There is much to speculate about even in this first time scale. Two of three models are rather similar with a continuance of relatively cold air for this country. GFS sees things rather differently. I would opt for the ideas of Met UK, and their Fax charts, along with ECMWF.

To the main forecast

I take the view that there are too many factors tending to point in a similar direction for the period to have much mild weather in it. Overall, in the strict definition by UK Met, rather cold to cold for most for much of the period. With a probability, maybe 30% of it turning into very cold for some eastern, central and northern areas. Snow and frost seem likely to occur with more than the 71-00 frequency, indeed perhaps more like the mid 80's frequency might be nearer the mark. No real sign of any storms but with a mainly blocked Atlantic flow north of 50N that is to be expected. The possibility of a deepish low tracking towards south western areas through this period is about 25% in my view. The longer the cold goes on then the more probable something like this may occur. It is after all getting towards the end of February and temperatures to the south of our interest will be on the rise creating an increasing difference between the zone 35N and 60N. From another perspective this fact is sufficient grounds, along with the uncertainties of just where the Tropospheric warming will impact and how, to suggest that a milder interlude is possible, I would rate it as about 20%.

[Yeti]

Another excellent forecast JH and no doubt it will be avidly read on here, as always :o

We missed you over the last few weeks and it's nice to have your informative and objective forecasts back

Hope you had a good (and well-earned) holiday.

[johnholmes]

very kind Yeti

thank you

yes and no

[PB22]

Thank you Mr Holmes, a top class read as always. :o

[Snowaddict]

Excellent forecast John, as always extremely well reasoned and supported.

Your knowledge certainly was missed in anticipation of the most recent wintry outbreak!

Regards,

SA. :o