Model output discussion - 20th Feb onwards

[johnholmes]

21 minutes ago, feb1991blizzard said:

But John on that chart it looks to me (by looking at 500mb) that the mid level lapse rates wouldn't be steep enough for anything significant, could you please confirm or deny whether the chart I posted above would give more than a few light showers.

Tell me the date/time you are quoting then we can have a look at the skew-t on Extra for that time. I can then give an opinion for you?

 

[johnholmes]

8 minutes ago, bigdog1 said:

Why are people arguing over charts that are five days away there will be lots of upgrades and downgrades before we get there 

Indeed, forecasting snow or rain, assuming the model show ppn over your locality, is fraught with problems. Sorry to repeat myself but to get snow prediction correct one needs a further 5 out of another 7 or 8 variables to be in the right area.

[Methuselah]

I've seen some posted charts suggesting 850s of around -8C which, in Feb-March 2013 produced nowt more than light snow/snow grains and a stratus-fest; but, however, SSTs were far lower than they are now, around 10C above the 850s??

This year, the situation is different: SSTs might be upwards of 12C warmer than the 850s  - more active convection but greater coastal warming? Then again, any showers that do develop might penetrate further inland...

I really don't know; it's yet another potentially marginal situation...

[feb1991blizzard]

2 minutes ago, johnholmes said:

Tell me the date/time you are quoting then we can have a look at the skew-t on Extra for that time. I can then give an opinion for you?

 

Saturday 27th Feb at 12 midday, its the GFS 12z run from today.

[johnholmes]

ok will take a look and drop the link (oops cannot do that), will copy-paste in paint on my pc and get back with what it shows.

Edited February 22, 2016 by johnholmes

[feb1991blizzard]

Just now, johnholmes said:

ok will take a look and drop the link (oops cannto do that), will copy-paste in paint on my pc and get back with what it shows.

Thanks John.

[johnholmes]

For Saddleworth 12z 27 Feb

surface T=4 Td=-2C; 850mb=-7/8

cloud tops 6000ft with inversion above and also very dry above.

depth of convection would seem insufficient for anything much be it rain, sleet, soft hail or snow.

 

[winterof79]

7 minutes ago, feb1991blizzard said:

Saturday 27th Feb at 12 midday, its the GFS 12z run from today.

why 12z? The flow is forecast for 12-24 hours maybe longer.Also Saddleworth could be completely different to other areas as it was in 2013 as you pointed out.

TBH ill just wait and see how it pans out.Its not life or death.

Edited February 22, 2016 by winterof79

[johnholmes]

very rough and ready but gives idea of 3 dimensional prediction from GFS via Net Wx Extra

The precip chart for that time has NO precip inland indeed very little anywhere

Edited February 22, 2016 by johnholmes
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[Liam J]

Cold air digging south midweek bringing wintry showers to the favoured places in a northerly flow. 

Cold with widespread frosts for many.

[marksiwnc]

Just now, *Sub*Zero* said:

Cold air digging south midweek bringing wintry showers to the favoured places in a northerly flow. 

Cold with widespread frosts for many.

The precipitation shown on Friday moving from Northern Ireland through the Irish Sea needs watching especially for hills but I would imagine the snow line to quite low levels.  what do you think? 

[Liam J]

3 minutes ago, marksiwnc said:

The precipitation shown on Friday moving from Northern Ireland through the Irish Sea needs watching especially for hills but I would imagine the snow line to quite low levels.  what do you think? 

Looks like mostly rain atm on the latest GFS charts anyway but still 5 days away so time for changes.

Less cold air out west with higher dew points associated with the front.  

[Polar Maritime]

A cold run throughout the 12z GFS again, With -9/-10 850's over Central UK by Wednesday and -6c/-10c uppers dominating from a N/NE flow with severe frosts for the North at times. 

Edited February 22, 2016 by Polar Maritime

[MR EXTREMES]

1 minute ago, *Sub*Zero* said:

Looks like mostly rain atm on the latest GFS charts anyway but still 5 days away so time for changes.

Less cold air out west with higher dew points associated with the front.  

If that's Friday's low pressure it was mentioned today by the bbc weather and they suggested snow for the moors 

[feb1991blizzard]

23 minutes ago, johnholmes said:

very rough and ready but gives idea of 3 dimensional prediction from GFS via Net Wx Extra

The precip chart for that time has NO precip inland indeed very little anywhere

Thanks very much, Much appreciated.

[feb1991blizzard]

32 minutes ago, winterof79 said:

why 12z? The flow is forecast for 12-24 hours maybe longer.Also Saddleworth could be completely different to other areas as it was in 2013 as you pointed out.

TBH ill just wait and see how it pans out.Its not life or death.

because that's the time that someone else posted and suggested widespread snow showers.

Anyway GEFS Has some decent members, lets hope the ECM continues the wintry theme and locks in cold but gives decent PPN.

[The Enforcer]

1 hour ago, feb1991blizzard said:

Ok then - I actually think that pressure chart with similar uppers and 500mb profile is very likely to verify so we will see what showers we get, what do you think will be showing on the graphics on the BBC forecasts on Friday night? if its any more than a few white dots on the East coast then I will walk down the high street stark naked.

It doesn't really matter what it is showing, because recent experience (I have examples) is that 'Dougal' struggles to correctly plot distribution of rain at T+0, so it is not hard to imagine snow distribution, with all its many additional parameters, turning out completely different on Friday night when the T+0 forecast is compared with the actual radar, for better or worse. As a telling example, the only settling snow I had last winter was not picked up by BBC graphics at T+0.

Edited February 22, 2016 by The Enforcer

[terrier]

To be honest looking at the gfs ukmo so far this evening we see very little in the way of precipitation. Apart from a few flurrys down the coasts. Anyone thinking this will be a March type 2013 event are setting themselves up for disappointment. Looks to me from the output some harsh frosts and crisp sunny days with maybe the odd wintry flurry nothing out the ordinary for late Feb early March. 

[feb1991blizzard]

11 minutes ago, The Enforcer said:

It doesn't really matter what it is showing, because recent experience (I have examples) is that 'Dougal' struggles to correctly plot distribution of rain at T+0, so you it is not hard to imagine snow distribution, with all its many additional parameters, turning out completely different on Friday night when the T+0 forecast is compared with the actual radar, for better or worse. As a telling example, the only settling snow I had last winter was not picked up by BBC graphics at T+0.

Anyway, looking at the ECM and its earlier output, I think I might change my mind anyway, the GFS may not verify, will it start its usual correction southwards tomorrow like at least 2 of the Easterlies in 2013.

[snowice]

Ecm cold frosty mainly dry mixing out of cold uppers there after!

[Daniel*]

1 hour ago, Jason M said:

Tbh, it doesn't look anything special to me at the moment. I think those expecting ice days and deep snow are going to be disappointed.

I thought Steve Murr nailed it earlier today when he said there was a good chance of falling snow at sea level, but maybe not settling. IMHO we are looking at a bog standard UK cold spell based on current output. Basically, what Fergie seemed to allude to earlier.

It could change, but after such a warm winter (both in NW Europe and in the northern hemisphere more generally) I simply can't see anything severe on the horizon. Probably best case scenario is an area of snow moving northwest out of France associated with low pressure to our SE. Maybe we could get a covering from something like that.

In any case, no point in getting wound up about it. We will find out who is right or wrong over the next week or so.

 

 

Definitely not, are you having a laugh - I'm not quite sure how you could say that over the last odd few winters the best we have mustered is a potent PM lasting a matter of days, ultimately only substance has been up north the cold spell would hold more significance if it was mid winter alas we're approaching March so you have to face reality in your expectations, there is a threat of signicant snow for southwest fri/sat I assume this is muted amongst it all, but the risk is there interesting model watching to come. Regarding temperatures anything from an easterly orientation with -7C uppers will not be marginal inland, furthermore SST are on warm side the Thames Estuary in particular, thus this reduces the need for exceptional upper air temps, under showers temperatures would take a tumble yes during daylight accumulations will be limited but by nightfall snow will settle readily. 

[Polar Maritime]

Sensible posts about what the models are showing with charts/data to back them up where possible please. There is a ramping/moaning thread already open, Thanks.

Edited February 22, 2016 by Polar Maritime

[Nick L]

ECM continues the cold and dry theme. A few light sleet/snow showers here and there but nothing significant. The annoying thing is though this easterly may just bring in overcast skies for the majority after the sunny week ahead.

[snowice]

  well south east England -8 uppers from +96 to 138 should see snow showers in the easterly flow

Edited February 22, 2016 by snowice

[fergieweather]

8 minutes ago, snowice said:

  well south east England -8 uppers from +96 to 120 should see snow showers in the easterly flow

Hmm. Not yet convinced. All the forcing has run away SE, perhaps a few PV strips/filaments aside, circulating in the flow N of the departing low centre. Last UKMO profiles I saw for E coast (but not 12z data) looked like StCu of limited depth, under a lot of higher cloud... all unlikely to yield ppn. 12z EC has no snow at all anywhere south of Pennines all the way from T+24 to T+240, but much can and doubtless will change even by Sat. 

Edited February 22, 2016 by fergieweather