Model Discussion And Chat 19th Feb.2012

[damianslaw]

Few posts tonight - perhaps indicative of the rather 'uninteresting' synoptics with the azores high ruling the roost for the foreseeable future and a rather ineffective atlantic - late feb/early march can be a very exciting time of year with sudden northern plunges or it can be a very benign period with few extremes bringing spring conditions - 2009, 2011 and now 2012 are certainly bringing the latter type of weather, 2010 also delivered quiet but much colder conditions.

Next week - models keen on stronger ridging of the azores high NE- whether it moves into scandi remains to be seen. I suspect what we will see is a strong trough feature developing over the mid atlantic ahead of the ridge mid week, will the atlantic finally kick the azores high into touch as we head into March?

Signs the jet will be taking a more southerly path in early March which is the key to removing the influence of the azores high coupled with a weakening PV it holds prospects for much more cooler conditions as we go further into March with northerlies and easterlies much more likely than blow torch southwesterlies or flat westerlies. This is the time of year when the atlantic and PV quieten down rapidly and northerlies and easterlies become much more likely.

[Geordiesnow]

Signs the jet will be taking a more southerly path in early March which is the key to removing the influence of the azores high coupled with a weakening PV

Theres seem to be very little signs of the PV weakening if anything it will strengthen quite substancially and a very strong PV will form for the time of year, this normally means for us a spell of SW'lies and that what it looks like we will experienced apart from some detail differences. As I said previously, I won't be surprised if a deep low forms with all that cold heading into the Northern Atlantic, it can quite often make the jet stream stronger and deep low pressure systems forming, of course a deep low could head stright into us or if there is kinks in the jet, it may help produce a ridge and perhaps something a bit colder might come on the horizon.

Apart from a cooler blip on Friday/Saturday into Northern areas, the outlook is looking mild and will turn very mild again for the first part of next week, what happens after that seems alot more uncertain though.

[damianslaw]

Theres seem to be very little signs of the PV weakening if anything it will strengthen quite substancially and a very strong PV will form for the time of year, this normally means for us a spell of SW'lies and that what it looks like we will experienced apart from some detail differences. As I said previously, I won't be surprised if a deep low forms with all that cold heading into the Northern Atlantic, it can quite often make the jet stream stronger and deep low pressure systems forming, of course a deep low could head stright into us or if there is kinks in the jet, it may help produce a ridge and perhaps something a bit colder might come on the horizon.

Apart from a cooler blip on Friday/Saturday into Northern areas, the outlook is looking mild and will turn very mild again for the first part of next week, what happens after that seems alot more uncertain though.

The PV is unlikely to hold its strengthened position for any lengthy time mind... it may exert some energy in early March but should wane markedly as we head through the second half of the month.

Less than 60 users in this thread - a far cry from those record values a couple of weeks or so back.. it feels like the depths of summer or those long uninteresting spells of weather we seem to get in october. I didn't look at the models from sunday-wednesday and I think I am going to refrain from looking at them again for a few days - can't see much of a pattern change in the short-medium term, but the outlook as we enter March is far from certain.

[reef]

If theres anything that can be taken from tonight's models its that its looking very dry indeed for the areas which need it most:

http://www.wetterzen..._London_ens.png

Very few members showing anything in the way of rainfall. This coupled with the mild and at times windy weather will also serve to dry out the ground and help evaporation rates, increasing the problems further.

Rinse and repeat, high pressure anchored to the south-west with the familiar NW/SE split of dull, damp weather and cloudy, bright but dry weather:

http://cdn.nwstatic....120/h500slp.png

Very mild yet again aswell.

http://cdn.nwstatic....0/ukmaxtemp.png

[Cheese Rice]

Interesting trend appearing on the GFS.

It seems lows may be tracking in a more southerly direction. Although the PV seems to be in full swing it should allows heights to build to our north east. The outlook hasn't gone the way I expected though with high pressure in-charge. Instead we have interesting solution where if we see a low positioned favorably we could see periods of snowfall across any parts of the UK.

Highlighted below..

Illustrating the southerly track.

Of course there are numerous factors involved and its not even worth considering where is favorable at this point. Nonetheless it is still an interesting pattern. One which could strike gold anywhere.

Looking at the London 850 ensemble highlights how snow could fall on a northern flank of lows even in the far south

The further north an even greater chance

PM incursions seem quite probable too judging by the latest ensemble.

Issues arise though as to whether the high over central Europe can sink, otherwise will be stuck in a NW/SE split, one which will have to end at some point. Regardless of the 18Z the GFS can underestimate the Azores high, though as I said earlier it has to crack at some point.

Its worth noting the ECM doesn't seem too keen on the idea of lows tracking southerly although there is cross model agreement of height rises across the UK/NE as we head into March. The UKMO/GFS etc are broadly similar with lows taking a more southerly track.

Overall as we move into March the settled spell I expected looks to have been delayed by a touch. I expect a more amplified pattern with PM incursions and southerly tracking lows for the remainder of Feb, with that a risk of snowfall on the northern flank and some wintry showers across NW parts at times. It's a pattern that promises much but delivers little, although not always the case. As we head into the first week of March a rise in pressure seems very likely. Height rises across North East Europe with again a likely-hood of a severe cold spell plunging into Eastern Europe. Perhaps the cold air can be advocated West, but this is too far ahead to forecast although the ensembles suggest a chance of cold affecting southern england later in the period.

Edited February 24, 2012 by Cheese Rice

[Frosty.]

The final insult to this most feeble of winters is now being delivered through the latest model output, temps reached 18.7c 65f in birmingham yesterday, closely followed by 17.7c in lincolnshire and most of next week looks every bit as warm, maybe a notch warmer with high pressure to the southeast, the charts next week look more like summer than the end of winter. This weekend will see a cooler blip with temps nearer 9-12c across the uk from north to south but then back to 16-18c through the majority of next week and no relief for the southeast drought. The warmth will probably crumble by next friday with temps sliding back towards average but remaining mainly anticyclonic. The Gfs 00z shows a bit of a mexican stand off towards the end with a cold block to the east and the atlantic flexing it's muscles but it's all a bit limp even then, with a relatively cold pool over the uk and yet temps of 6-8c.

Edited February 24, 2012 by Frosty039

[Nick F]

Looks like becoming very mild again on Tuesday, as heights build from the SW and we draw in Tm air from way to the SW - similar values to yesterday for England and Wales probably.

Cooling off across central and north areas by the end of next week on the 00z GFS, as it builds a high to the NE which allows a cooler and drier continental feed from the east (which is still cold) to develop.

Apart from rain crossing most areas on Monday, it does look very dry across England for much of the week, as Atlantic fronts stall to the west.

[nick sussex]

More concrete signs today that high pressure will be edged further north with time and better agreement on some mid Atlantic troughing at 144hrs.

The PV which was shown very strong just a few days ago has been toned down with some fragmenting of this and the NH pattern seems to look a little better for those looking for some colder weather during March.

Still hard to see this coming from the north and it looks like we'd have to be looking to the ne or east for a change and that again depends on whether any cold pooling can be advected west, we've seen just how difficult this is with the northern arm of the jet often throwing a spanner in the works.

[lorenzo]

A little variance from the ECM position at 216 and we could see some change... http://www.meteociel.fr/modeles/ecmwf/runs/2012022400/ECH1-216.GIF?24-12

Still don't think we are heading straight into spring at all, acknowledge that there may be a definitive NS divide..

Was wondering if this was the most positive AO winter on record..? Seems like we paid this year for the storming -5 session last winter..

[nick sussex]

A little variance from the ECM position at 216 and we could see some change... http://www.meteociel...1-216.GIF?24-12

Still don't think we are heading straight into spring at all, acknowledge that there may be a definitive NS divide..

Was wondering if this was the most positive AO winter on record..? Seems like we paid this year for the storming -5 session last winter..

These two links give the AO and NAO monthly readings back to 1950:

http://www.esrl.noaa.gov/psd/data/correlation/ao.data

http://www.esrl.noaa.gov/psd/data/correlation/nao.data

I'm not sure about data before that period, maybe someone else has a link to before that.

[MP-R]

I think in light of how dry and boring the winter has been overall, perhaps a slight weakening of the PV with LPs tracking further south is what we need for the southern half of the country to get some much needed rain. March always produces an Atlantic spell for at least a third to half of the month (2005 and 2011 being exceptions) so fingers crossed the pattern will follow this year.

The models do seem to bring the jet further south into FI with a mix of mild and cool zonality, especially on the GFS. Little sign of a cold spell currently save for perhaps frosty nights if high pressure moves to the NE. A fairly benign picture across the board for the next few days though at least.

[Frosty.]

The Gfs 06z op run has rather stunted the very mild springlike week the ecm 00z is showing for next week and now has next monday and especially tuesday as the warmest day before it turns cooler from wednesday onwards, the overall pattern is very similar with pressure generally high and therefore rainfall amounts look trivial. Into FI shows more high pressure but with normal or above average temps, some brutal cold heading into eastern europe and some colder zonal weather approaching from the west but nothing wintry for the uk.

Edited February 24, 2012 by Frosty039

[Frosty.]

It's like the decks of the titanic on here today, are the models really that bad? FI shows a risk of cold weather from the east as heights rise to the northeast of europe and maybe some kind of battle will evolve between the atlantic and the cold block. There is strat warming in march to factor in although this has so far failed to have any impact on the near timeframe.

Edited February 24, 2012 by Frosty039

[MisfitDog3]

@Frosty...I think you answered your own question there! Anything remotely cold looking is out there in FI and even then looks fairly halfhearted! Saying that, it is surprising quite how dependent on the promise of colder weather this particular thread is for any serious activity.

[cooling climate]

It's like the decks of the titanic on here today, are the models really that bad? FI shows a risk of cold weather from the east as heights rise to the northeast of europe and maybe some kind of battle will evolve between the atlantic and the cold block. There is strat warming in march to factor in although this has so far failed to have any impact on the near timeframe.

I do not think many are up for another will it or wont it easterly after the last episode where a lot of folk missed

out. Also with it being in March if any easterly did ocurr we would need some very cold uppers to make it

worthwhile. Even in this very mild winter the UK came so close to something special which could have given

Jan 87 a run for its money for both cold and snow.

Still something to watch and you never know it might work favorably for us as March is still not to late as

long as you get the right synoptics.

[lorenzo]

Thanks for the links Nick, nice and quick to decipher.

Looking at the NAO ones there are only 3 years that displayed a similar NAO regime.

Sept Oct Nov Dec Jan Feb Mar Apr

Sept 1956 > Feb 1957 0.38 1.47 0.40 0.00 0.71 -0.32

Sept 1999 > Mar 2000 0.50 0.73 0.55 1.40 0.19 1.48 0.40 -0.18

Sept 2007 > Mar 2008 0.85 1.00 0.48 0.23 0.53 0.38 -0.32

Sept 2011 > Jan 2012 0.67 0.94 1.30 2.25 0.86

GFS today and in 2008 below.

The other positive years above are here.. 57 and 2000.

2008 looking like a better fit. So in respect of that looking at the archives found this from March in that year.. Finally an elusive Greenland High via a Scandi High earlier in that month..

Time will tell..(puts away box of straws )

Edited February 24, 2012 by lorenzo

[Cheshire Freeze]

Thanks for the links Nick, nice and quick to decipher.

Looking at the NAO ones there are only 3 years that displayed a similar NAO regime.

Sept Oct Nov Dec Jan Feb Mar Apr

Sept 1956 > Feb 1957 0.38 1.47 0.40 0.00 0.71 -0.32

Sept 1999 > Mar 2000 0.50 0.73 0.55 1.40 0.19 1.48 0.40 -0.18

Sept 2007 > Mar 2008 0.85 1.00 0.48 0.23 0.53 0.38 -0.32

Sept 2011 > Jan 2012 0.67 0.94 1.30 2.25 0.86

GFS today and in 2008 below.

The other positive years above are here.. 57 and 2000.

2008 looking like a better fit. So in respect of that looking at the archives found this from March in that year.. Finally an elusive Greenland High via a Scandi High earlier in that month..

Time will tell..(puts away box of straws )

Yes as I have stated I think we are en route to a cold March/April.....something that I was much more confident of than a cold winter period. Could be some nice convective potential should it come off. Analogues and stratospheric indicators suggest that vortex disruption and dissipation should be favourable for us coldies as March progresses

[glosteroldboy]

Not sure if this is allowed but as it's so quiet can anyone give their interpretations of the models for Newfoundland, specifically the Avalon peninsula over the coming weeks. I see you can usually see Newfoundland in the images people post but am useless at interpreting anything. I'm a Brit staying there if it counts for anything, we have become snow starved (like much of Canada this winter) over the past 3 weeks and everything is falling as mainly rain since early Feb in the Avalon now which is unusual here at this time year.

Edited February 24, 2012 by glosteroldboy

[Milhouse]

Very dry is the theme that comes out of the models today with an emphasis on a lot of high pressure in the coming couple of weeks. There seems decent support for a blocking high to form over Europe which would deliver very dry southeasterlies to the UK. This wouldnt be such a cold direction either with temperatures likely to remain around average. The Atlantic will attempt to break through but a fairly lengthy spell of dry weather seems quite likely looking at the ENS mean into FI. Variations in rainfall will occur with the NW seeing the wettest conditions and the SE seeing very little rain. Very typical of the pattern of the last 6 months.

[summersnow]

Well folks! I reckon in broad trend terms (which is what model watching is all about) the models have actually performed very well this winter and primarily in their ability to show the dominance of the Azores HP. In late January, I stated that I reckoned the models were making it more than clear that the Azores HP would remain the dominant theme and I suggested then that we might be in for an early spring. That is exactly what has happened despite an enormous amount of conjecture suggesting much colder scenarios.

As regards, the current model outlook, it still looks like the Azores HP is going nowhere in a hurry but I would expect some sort of change by mid March as this is when the sun starts to exert a very different effect on the north Atlantic while at the same time sea ice starts to melt meaning that one of the main drivers behind the NAD is often disrupted.

Of course quite what this effect will be is still pretty much pot luck, anything from warm dry continental airstream through to chunks of seriously cold arctic air. Any cold from an easterly direction will certainly subside as the continent begins to warm, so it will need to come from either the north or northwest. I think the much more likely scenario however, is HP setting up over N. Europe/ S Scandi and giving us mainly dry and pleasant conditions through March - the exception being possibly the far northwest of Scotland.

By the way, if anyone considers our mild winter is anything to do with Global Warming, UAH Global average temps have recently dropped to the lowest ever on the satellite record!

Edited February 24, 2012 by summersnow

[lorenzo]

A more amplified GFS here http://modeles.meteo...nh-0-180.png?12

Where did that Jet go??? http://modeles.meteociel.fr/modeles/gfs/runs/2012022412/gfsnh-5-180.png?12

Albeit 12 hours before the zonal 192 switch kicks in..

Edited February 24, 2012 by lorenzo

[Milhouse]

GFS 12z much as i expected with HP blocking over the continent and low pressure skirting north across the far west of the BI.

[Summer Sun]

ECM is giving us some nice mild weather for early next week,

Temperatures look like dropping after

[Summer Sun]

WOW! Thats one big area of high pressure

[summersnow]

GFS 12z much as i expected with HP blocking over the continent and low pressure skirting north across the far west of the BI.

Agreed! I don't see this pattern changing much over the next couple of weeks or so. After mid March however, anything could happen as I explained above. Watch this space! Edited February 24, 2012 by summersnow