Model Discussion And Chat 19th Feb.2012

[Zakos]

wow, an amazing GFS 18z. Perfectly plausible scenario to me. Especially as the idea of a blocked pattern early march has been there in the GFS FI lately. Seeing as its the very first week of spring this could still deliver some very cold conditions. Lets hope this isn't an FI tease that will be gone come tommorow.

The GFS 18z is miles better than the 12z Gfs FI, but they both show the dissapereance of the Azores high. This is something I think we will see as march progresses although of course this does not guarantee cold for the UK e.g 12GFS

The ECM worryingly bears no resemblance whatsoever to the GFS at 240 hours. So no reason to get your hopes up, but equally the GFS is backed up by the CFS so the possibility of a cold/very cold start to march cannot be discredited.

Meanwhile, some very mild weather to come this week, it looks positively spring like for many.

[BlueHedgehog074]

Either the 18Z GFS has had too many drinks from the pub, or that its cold scenario in FI could be a warning as to what may just end up developing. The previous 12Z run seemed to have hinted at High-Pressure attempting to ridge North of us in FI, although had the High ending up going to the North-East/East not quite bringing in those colder uppers. While alot can still change in that period, I think the fact some of the models are starting to show this idea of High-Pressure trying to ridge North could be an indication of the Atlantic weather next week (especially for northern parts) being temporary affair.

[nick sussex]

Regarding the eastern USA troughing, although we don't have the forecaster input NOAA maps this evening, we do have the forecasters view upto 168hrs for the USA and Canada. This is their take on that trough:

http://www.hpc.ncep.noaa.gov/medr/day7nav.html

It certainly looks to support the ECM 12hrs/GFS 18hrs in terms of a deepish reasonably amplified troughing, unfortunately we can't see whether that trough phases with the low to the nw as in the ECM or if that low remains separated to the nw of the UK.

I think we have to be realistic here, that GFS 18hrs run is very long odds, the ECM does something different and probably more plausible by phasing with that low to the nw and driving some energy ne'wards allowing the ridge further north but the northern arm of the jet not relenting afterwards.

It does however come down to the exit speed of that trough and its amplitude, that really is our last hope to derail the zonal express.

[Cheese Rice]

A pleasing GFS run, one that doesn't come as a huge surprise considering the trend on the GFS ensembles with an evident scatter occurring recently. My post a couple of days ago sums up what I think will happen..

Encouraging signs that the Azores high may push north to link with the block over Russia. ECM having none of it though with the GFS repeatedly showing some sort of linkage in FI.

In the medium term I expect northerlies to become more of a feature as we head through the latter part of February. ECM/ GFS/ NOGAPS etc all show sufficient ridging at times over the Atlantic for transient cold snaps in the form of topples. I expect a northerly to show soon around T180 if the current trend is correct.

In the long term we are likely to be under or near high pressure leading to dry conditions as we head into March with a possible shot at an easterly if the high can position itself favorably.

Personally I would say the outlook isn't terrible, we still have a huge block over Russia which we can hopefully tap into with northerlies at times.

The northerly that I was pushing has indeed shown at T180, although its not really that cold there is still time for improvements. I firmly believe the Azores high will push north as we head into March, we are beginning to see cross model agreement of the high pushing North. ECM looks interesting at T168 but is quick to flatten the pattern. I'm happy to ignore past T168 and work from there.

[davehsug]

To be honest though, Easterlies rarely deliver anything that late in the winter or early spring. The only reliable route to cold & snow is a true Northerly, especially as convection increases. We only have to cast our minds back to 2006? (I think), to see what a waste of time they are for most.

[Cheese Rice]

To be honest though, Easterlies rarely deliver anything that late in the winter or early spring. The only reliable route to cold & snow is a true Northerly, especially as convection increases. We only have to cast our minds back to 2006? (I think), to see what a waste of time they are for most.

5 consecutive days of snowfall, each day totaling 5-10cm of fresh snow. Plus two other significant snowfalls. 2006 was great here.

[reef]

To be honest though, Easterlies rarely deliver anything that late in the winter or early spring. The only reliable route to cold & snow is a true Northerly, especially as convection increases. We only have to cast our minds back to 2006? (I think), to see what a waste of time they are for most.

http://www.wetterzentrale.de/archive/ra/2006/Rrea00120060311.gif

Widespread snow in March 2006 from that weak easterly when it broke down, especially in western areas. Northerlies are the most reliable, but an easterly can still be every bit as cold as in winter if there is a cold pool to dip into.

[nick sussex]

To be honest though, Easterlies rarely deliver anything that late in the winter or early spring. The only reliable route to cold & snow is a true Northerly, especially as convection increases. We only have to cast our minds back to 2006? (I think), to see what a waste of time they are for most.

I'd agree with this, unless you get a piece of the PV dropping into Russia injecting some deep cold into the flow as its advected west then it's hard to get that convective sunshine and snow showers easterly for the UK. It's especially evident now as that surface cold has been removed from the continent and its hard to develop cold pools as you head towards spring.

So a northerly or ne flow is much better especially as the increase in solar energy brings more widespread snow showers with those cold downdrafts bringing some lively weather.

[Cheese Rice]

Shouldn't really post in this thread but just to put an end to the 'snow is useless march' argument which seems to come round every year.

March 2006 brought a weak easterly, uppers weren't amazing yet inner city Leeds below 50m saw these scenes...

Rivers froze..

Freeze thaw, snow managed to stay till night then froze forming icicles

In the city center despite been an urban heat Island the rivers still froze, thick enough for lying snow....

Despite a week flow snow showers were actually heavy... and deep enough to make snowmen

Edited February 20, 2012 by Cheese Rice

[Duane S.]

GFS continues to tease, the 00z says yes. Certainly one to watch in the coming days

[Zakos]

Yes cheese, i struggle to see how as soon as the calender turns march its "curtains" for snow. Being the very first week of spring I see no reason at all that the current forecast from the gfs for the first week of march would not deliver cold and snowy conditions countrywide.

[KTtom]

Yes its miles away and yes its very unlikely to happen, however the chart posted above is pretty much a perfect easterly set up and demonstrates what was missing with the easterly at the start of Febuary, namely the low heights to the south west. We may not have the severe cold of the Febuary episode but for the other 66% of the country that missed out last time this set up has snow potential written all over it.

Edited February 20, 2012 by KTtom

[johnholmes]

6 out of the last 8 are nothing to do with the model output-why oh why can we not stay on topic? A large change for many this week as temperatures seem possible for sheltered eastern areas 13-16C. Less kind weather again for NW'ern areas to experience rain that the SE'ern areas so badly need.

Edited February 20, 2012 by johnholmes

[Polar Maritime]

The GFS continues to show a nice warm spring like week for all but the far North this week, where it will stop cool and wet at times. We realy need some rain...

Also of interest is the cold/blocked end to the month that the GFS&CFS has been showing for a good while now, and is slowly looking more and more likely to happen.

Edited February 20, 2012 by Polar Maritime

[MisfitDog3]

Oh dear! Mild spike then.....well something colder or much colder. Seems to be at least some interesting consistency on the cold FI outlook which is unusual this winter/spring. Will watch with interest over the next 72 hours and then see what the model runs are showing...and then also have a think if I switch tyres back to the norm!

[snowmadchrisuk]

Interesting that the No Gaps at +180 is showing what the 18z Showed at that time frame last night , That makes it the second Model to catch on to the Freezer idea, wouldn't expect to much from the 6z as it always seems to like dropping good ideas only to go back to them .. but let's watch and see what happens and how amplified that trough of USA gets . .

[KTtom]

Interesting that the No Gaps at +180 is showing what the 18z Showed at that time frame last night , That makes it the second Model to catch on to the Freezer idea, wouldn't expect to much from the 6z as it always seems to like dropping good ideas only to go back to them .. but let's watch and see what happens and how amplified that trough of USA gets . .

Do you have a link? I can only get NOGAPS to +144?

[snowmadchrisuk]

Do you have a link? I can only get NOGAPS to +144?

http://www.meteociel.fr/modeles/nogapse_cartes.php

The Chart I mean is below

[legritter]

nice to read some happy posts . GFS is running ,hope it keeps the cold theme going in later frames . im certainly banking what is being shown ,lets hope ECM STARTS TO COME ON BOARD ,ALL IN THE FUTURE THOUGH , JUST OFF TO POST A LETTER TO OUR FRIEND mr azores high , YOURE UNCLE FINLAND HIGH IS ARRIVING SOON GO AND JOIN HIM ,REGARDS LEGRITTER .

[johnholmes]

I’m afraid that as usual there is a fair amount of hope casting by those wanting cold and snow.

On a temporary basis, especially for the north, as we move into early March over the next 10-15 days, cold will extend south behind low pressure as it moves away east or NE from the UK. Probably not dissimilar to what happened Friday into Sunday just gone. Equally at times we may well have what seems most likely later this week, some pretty mild air being brought up from south of the UK but with fairly cloudy, windy and at times rather wet weather for more NW’ern areas.

The reason is that the upper ridge is very unlikely to be anywhere but west of and most of the time just SW of the UK.

Whilst the 500mb anomaly charts are not totally conclusive and solid in their positioning of the trough way west of the UK, at times over the eastern states, at other times over the western Atlantic and with differing orientation, nor its precise positioning of the upper ridge. Its really not suggesting the upper ridge to be far enough west for much other than brief cold nor anything that looks like it being positioned far enough NW to allow really cold air to move south. Nor is there any sign of it moving NE to position itself over Scandinavia in this time scale.

[snowmadchrisuk]

Looks to me like the 6z is going to say Yes , better than the 00z at this stage as the Setup is further West .

[KTtom]

http://www.meteociel...apse_cartes.php

The Chart I mean is below

Thanks. The 06z is actually very similar to the great NOGAPS at +168 for what its worth and similar to the GFS 00z.

Edited February 20, 2012 by KTtom

[Nick F]

Yes, the 06z continues the theme of buckling the jet to our west by this time next week, but whether it leads on to a colder evolution for the UK will be an unanswered question for a while yet. We need ECM to come on board aswell, because it's keeping a much flatter jet profile going on its operational.

[TEITS]

I’m afraid that as usual there is a fair amount of hope casting by those wanting cold and snow.

Really because to me it looks as though members are discussing the model output. Recent GFS runs have shown some interesting synoptics from around +168 onwards but as ever im not interested until the ECM shows the same.

Big difference between hopecasting and discussing the model output which is what this thread is all about.

[snowmadchrisuk]

. Its really not suggesting the upper ridge to be far enough west for much other than brief cold nor anything that looks like it being positioned far enough NW to allow really cold air to move south. Nor is there any sign of it moving NE to position itself over Scandinavia in this time scale.

Hehe , you admitted you got it wrong last Week , I wonder if you will be wrong again lol. Every Model has a wobble from time to time maybe the JH Long range is going through one of these right now . So you see no Undercutting that will enable the High to move further North ? It Seems to me with low pressure keep being shown to our SW it may be a possibility .