Model Output Discussions 12z 08/03/17

[Winter Cold]

Well good agreement between ECM and UKMO at T144 which as we know is a very strong combo to have. GFS showing something similar to this about a day later so strong indications still that April may end quite cool:

Having a look at the GFS ensembles from the 12z shows pressure dropping as we head towards the last week of the month with the mean coming down to around 1010mb. Lowest its been for a long time, so although it may not be nice, we do have to admit that southern areas especialy need the rain! You can see the precipitation graph responding to the drop in pressure accordingly around the 25th, this for London:

[lassie23]

I can't see this having any affect down south, 11c by day maybe a zero at night.

Edited April 18, 2017 by lassie23

[Guest]

1 minute ago, Eugene said:

Wow my heating hasn't come on for a long time, it's hardly been that cold has it with temps mainly in double figures by day and no harsh frosts for over a month.

we have had some harsh frosts here in the peak district and doubles figures on a few days but nothing of any note apart from the other weekend when it was warm my heatings been on since October. I would add the wife has health issues and feels the cold..

[gottolovethisweather]

1 hour ago, Eugene said:

Wow my heating hasn't come on for a long time, it's hardly been that cold has it with temps mainly in double figures by day and no harsh frosts for over a month.

My last Air Frost was, in fact, 10th February, Eugene. So we did have front-loaded winter when it came to frosts but certainly not the magical white stuff. That never arrived apart from a few flakes, so I guess it'll probably arrive when few would want to see it. The irony of our changed climate. 

Edited April 18, 2017 by gottolovethisweather

[gottolovethisweather]

1 hour ago, lassie23 said:

I can't see the this having any affect down south, 11c by day maybe a zero at night.

-4c in prone spots tonight, so I take it you're speaking from an urban context there. Certainly some impressive diurnal ranges might be in the offing when the flow backs to the South, eventually.

[damianslaw]

Strong cross model agreement today, theme remains a dry one overall and quite chilly, with a northerly shown for early next week, and a full on turbo charged northerly with strong Greenland heights and deep long wave trough - frost and wintry showers would be the order of the day at least in the north. UKMO and ECM very similar at the 144 hr timeframe.

Things can change, but there is now a strong signal for such developments, resulting in the first period of below average temps since mid-late Jan.

We are at the time of year when northerlies reach their yearly maxim i.e. late April and May is when we are most likely to see a northerly, the chances of such synoptics verifying now are far higher in terms of probability than any other time of year.

[lassie23]

26 minutes ago, gottolovethisweather said:

-4c in prone spots tonight, so I take it you're speaking from an urban context there. Certainly some impressive diurnal ranges might be in the offing when the flow backs to the South, eventually.

Yes i meant London, I can see the home counties getting pretty cold though

[snowray]

4 minutes ago, lassie23 said:

Yes i meant London, I can see the home counties getting pretty cold though

Central London rarely gets very cold though lassie, even in colder winter weather temps generally hold up pretty well. Although just north of London is entirely a different matter, in fact even Hampstead Heath could still get some snow I would think if next weeks charts were to verify, is that near you?

 

 

[lassie23]

20 minutes ago, snowray said:

Central London rarely gets very cold though lassie, even in colder winter weather temps generally hold up pretty well. Although just north of London is entirely a different matter, in fact even Hampstead Heath could still get some snow I would think if next weeks charts were to verify, is that near you?

 

 

NW London, so not far from me. I think the northerly showing in the models would actually produce more active weather in April here, than in December.

[Cheshire Freeze]

This looks quite cold from the GFS 18z at 144 hours

[KTtom]

This looks even colder from the UKMO from 144...now that's what you call a northerly

 

 

[Matthew.]

Spot the difference

[Sky Full]

So this is the situation predicted by the ECM in six days time:

   

and GFS agrees:

   

Wintry looking charts or what!   This would bring colder than average conditions for most, perhaps lasting until the end of the month, but snow would surely be unlikely away from the highest ground?  Some low lying areas will no doubt continue to see some overnight frost, but hopefully the last of the season.  We have avoided any frost locally over the last couple of days so I'm hoping we might get through the Spring now without any more.

[Summer Sun]

Here's the UKMO 850's at t120

The 850's don't go to t144

[snowray]

-10c uppers getting into northern Scotland on the 06z. -12c's not far away.

[snowray]

Widespread snow showers effecting even the South West.

[Methuselah]

5 minutes ago, snowray said:

Widespread snow showers effecting even the South West.

Even if it doesn't snow convection might still be spectacular?

[snowray]

5 minutes ago, Ed Stone said:

Even if it doesn't snow convection might still be spectacular?

I would think so.

Look at this little feature moving down from the north sea, now that would produce lots of rain, sleet and certainly snow in the north, particularly in Scotland. Even the SE gets a bit of the white stuff before it moves away south.

[MP-R]

9 minutes ago, Ed Stone said:

Even if it doesn't snow convection might still be spectacular?

Yes! Very much the case on April 26th-27th last year. Snow wasn't brilliant but gorgeous cbs all around and thunder. For the south I reckon it'll be hard to achieve proper snowfall from the charts shown but some good old April showers most certainly.

[Summer Sun]

15 minutes ago, snowray said:

Widespread snow showers effecting even the South West.

 

Snow accumulation charts for that timeframe

[weirpig]

For late April at night it will feel cold with a significant windchill

[comet]

The cold spell that I posted about occurring post Easter rather than the Easter period itself really seems to be gaining momentum now. Large temperature drops in heavy convective wintry showers likely almost anywhere I would imagine and if the 06z gfs is on the money (that's a big if) then perhaps a more prolonged period of sleet and wet snow working its way down the country.

Edited April 19, 2017 by comet

[Summer Sun]

April 2016 left and April 2017 right at t168

Looking like we'll see a northerly around the same time 2 years running

[Scandinavian High.]

Hello everyone i back I thought I would come out of my  hibernation in November but not mid April so looks like turning much colder with frost ice and sleety snow hail showers...

[Summer Sun]

GEM has the high a bit further east on this run which will restrict any showers to the east coast mainly

00z

UKMO has other ideas though - if only charts like this arrived in winter when they could be of more use

 

Edited April 19, 2017 by Summer Sun