North West England Regional Discussion 11/01/13 ------->

[johnwirral]

rain on monday for west on nae http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=-&VAR=prty&HH=42&ZOOM=0&ARCHIV=0&RES=0&WMO=&PERIOD=

[karyo]

Here comes the slider, for our region we need the block further North as well as further West, so that we tap into tighter isobars before they sink in order to get any convection over the pennines.

Yes, in the long run it is looking lovely!

[damianslaw]

Its now very much a case of nowcasting, tomorrow should deliver snow to most parts of the region away from western coastal parts, how heavy and long lasting remains to be seen, however, some western parts may struggle to see a cover even if the snow is falling, inland parts shouldn't have a problem, M6 could be the dividing line between who sees a cover and who doesn't.

As for Monday - yes it does look marginal for much of the region, unless you have some height, east lancashire and Pennine regions look best placed to see further snowfall with a decent cover, and I doubt the warmer uppers behind the front will be sufficient enough to induce a thaw, colder uppers qill be quickly waiting on their heels from the NE.

Next week in the main looks very cold, freezing fog and ice are likely to be the key hazards for much of the region, Pennine districts could very easily stay sub-zero thanks to snow cover, and I wouldn't be surprised if many see temps regularly between -5 and -10 degrees from Tuesday onwards, with some favoured spots possibly getting below -10 degrees.

I've mentioned snow prospects for Cumbria in the Far N England thread.

[Bartlett Low]

Nae better than I was expecting tbh. Not much in it for game on everywhere in the region

[The Northern Ramper]

As much as the Nae is showing a snowfest for me it is far too close for my liking.

[feb1991blizzard]

The thing is though it's easy to criticise the NAE as we all watch the projection of snowfall like a hawk, the GFS outputs are really in the most broadest terms when it comes to PPN type, so no one ever criticizes this side of its output. There's a similar discussion on the Yorks thread where I posted this....

I'd put my bet on the higher resolution models no doubt about it.

As a general rule the NAE has the following tendencies-

- Overestimate snowfall potential

- Poor timing of fronts by generally 2-3 hours (a surprisingly common occurrence)

- Project precipitation on a broad scale rather than pinpointing small features

The NMM

- Underestimate snowfall potential

- Over analysing the intensity of fronts leading to incoherent outputs

Overall yes a fair assesment, i would wager that any model like that will have a better strike rate than the GFS with its poor resolution, i cannot speak for NMM, i was going to order it for this winter but severe financial difficulties look to have put the kiabosh on that idea.

[RainyNWales]

How close is this.....

Either way the Pennines will get buried

Since i live on the North Wales coast is there any reason why it has snow in the middle with rain all away round it or is it just not very accurate? We normally get rain anyway haha

[feb1991blizzard]

As much as the Nae is showing a snowfest for me it is far too close for my liking.

Yes i was just thinking that.

Good amplification of the trough out West, could be a mid 80s run coming up here.

[Cheshire Freeze]

Since i live on the North Wales coast is there any reason why it has snow in the middle with rain all away round it or is it just not very accurate? We normally get rain anyway haha

No idea but a 50 mile jog west would do us all a favour. However, if anything, the trend is east.

[Bartlett Low]

Colder uppers could easily shift the 50 miles needed.

Although at this range history not on our side. Looks like drying up for a while on MOnday afternoon which might preserve any snow cover though until the colder uppers return. Looking forward to it myself.

[Bartlett Low]

Right out at 177hrs on the 18z gfs looks a bit for Ireland.

Gotta feel sorry for snw lovers over the pond, worse place to live than the NW.

[martinj2]

As promised, my analysis of the upcoming fronts:

First off, starting with tomorrow afternoon, the front will be making inroads from the north west, Northern Ireland is out of the picture for snow, the ECM makes it clear why, uppers of just 0C for the most part, for our region we're looking at uppers of around -6C, maybe a little lower.

As you can see from the two charts below, the first being the ECM, the second the GFS chart at T+24

There are in fact some minor differences, even at this time frame. The ECM seems to have a slightly more westward shift than the GFS, and because of the higher resolution the ECM is run at, I would expect the GFS to fall in line with it's higher resolution partner, giving a slight correction westwards (benefiting us). The more westward correction reflected by the charts, the better as the mild sector will stay out west, although on the ECM, the mild sector is virtually non-existent.

Compare the minor differences to the UKMO, which has a much greater westward correction, and NO mild sector. Ideally, this is the outcome we would like to come into fruition.

That's how it's looking before the fronts arrive. Now the first front will arrive at T+30, so let's take a look at that.

For this we will be using only the GFS & UKMO as the ECM's closest is the 24hr chart as seen above. The first chart is the GFS, the second the UKMO.

As you can see, there's no problems with the first front's arrival, the uppers are convective to snow even right on the coast, being around the -6/-7C mark, all fine and dandy here. Not going to bother posting the precipitation charts for this time frame as they can and will change right up to the final hour, although right now the initial front looks like delivering mainly light snow to the region as it decays moving eastwards, not expecting much of a covering from this one, I'd say 1-2cm at best from this, a little more over the higher ground.

Now this is where the problem lies, a mild sector at 850hpa, and possibly further down in the atmosphere. Not all of the models show this mild sector, in fact the GFS is pretty much on it's own with regards to the sector, although this does not mean it can be discounted, there is some support for it, this will most certainly be a case of 'watch the lamppost'.

The secondary, more problematic, 'beefier' front arrives at T+45.

Starting firstly with the GFS:

Already with this chart you can see where the problem lies, that -2C isotherm line (over the entire region at one point on the GFS a few hours earlier) is dangerously close to causing a nasty freezing rain event. The GFS has a much worse eastern tilt to the isotherms. Compare this to the higher resolution ECM at +48

As you can see, that milder isotherm is WELL to the south west, suggesting that the secondary front does not draw in milder air with it for us in the west.

Next up, the UKMO:

Notice the correlation with the ECM? It has us under even colder air, -6C 850hpa temperatures, meaning there would be no rain at all, even for coastal regions.

Myself, I would probably go somewhere in between the ECM and UKMO, I cannot see the GFS outdoing these two models at such a close time-frame. Not only this, other models such as the GEM & NOGAPS also say no to a milder sector.

FAX not looking too bad too, evident why the Met Office have the warning out for our region, there is some real potential here.

The FAX has us inside the 528 DAM line the whole time, although as you can see from the below GFS, we're just on the boundary between rain & snow. At T+48 when the front arrives, a little iffy, but even if the GFS proves to be correct, it should stay as snow for a time during Monday morning.

And finally the precipitation charts. UKMO offering the heaviest precipitation up the NW England from the first front.

We then move on to the second front with the T+48 & T+60 charts

A good few hours of wintryness to be had, especially if the NAE is correct! (I'm told the Met Office do actually use this model)

It then just goes into overdrive and gives us an absolute PLASTERING

Beyond then it's anyone's guess. Good luck all.

Brilliant commentary BT-thanks for that. Helped a lot in understanding how to read the charts.

[Backtrack]

Brilliant commentary BT-thanks for that. Helped a lot in understanding how to read the charts.

No problem, shame it probably isn't correct now, I should of waited until the 18z

[Darren Bown]

There's a couple of people on the models thread suggesting a more widespread snow event and a 'westward shift' aswell?

[Cheshire Freeze]

There's a couple of people on the models thread suggesting a more widespread snow event and a 'westward shift' aswell?

The latest hi res NMM model I've just viewed reduces the snow risk pretty much everywhere west of about Lincoln!

[feb1991blizzard]

The latest hi res NMM model I've just viewed reduces the snow risk pretty much everywhere west of about Lincoln!

By how much does it reduce it, are you talking a complete collapse?

Edited January 12, 2013 by feb1991blizzard

[Cheshire Freeze]

By how much does it reduce it, are you talking a complete collapse?

Major mild sector involved. Snow level up at 600m by 9am. Don't know if Paul would let me post a chart.

[feb1991blizzard]

Major mild sector involved. Snow level up at 600m by 9am. Don't know if Paul would let me post a chart.

Ok no worries i believe you, you dont need to, thanks.

[Backtrack]

Major mild sector involved. Snow level up at 600m by 9am. Don't know if Paul would let me post a chart.

Yeah you're allowed to post NMM charts on the forum as long as you don't post the entire run.

[Cheshire Freeze]

Ok no worries i believe you, you dont need to, thanks.

I'll just add dew points up between +2 and +4 at same timeframe. Rain I'm afraid for low ground below 150m.....even the first band is shown as nothing more than sleet west of Manchester.

[Bartlett Low]

Shocking news

[Cheshire Freeze]

Yeah you're allowed to post NMM charts on the forum as long as you don't post the entire run.

[Barmada Casten]

Anioher last minute downgrade - same old story every single year.

simply pathetic. Suprised? Not any more.

[Bartlett Low]

Not gonna ask up to post it but hows it llooking the frame before?

Anyway sort of prefer it when you simply didn't know?

[feb1991blizzard]

I'll just add dew points up between +2 and +4 at same timeframe. Rain I'm afraid for low ground below 150m.....even the first band is shown as nothing more than sleet west of Manchester.

Thanks for the info, what a collapse. I cannot believe it!!!