Model Output Discussions 12z 08/03/17

[Summer Sun]

Arpege has struggled with cloud amounts for this morning as well

[Captain Shortwave]

Regarding cloud cover forecasts and reality, looking at it all of this was mostly in relation to high level cloud and to be fair, there was quite a bit of high cloud in the south yesterday, I was in Chelmsford and until mid-afternoon there was a fair amount of high cloud before this moved away southwards, it didn't spoil the day at all. Again today the models do show high level cloud across the UK, this seems reasonable as I look out of the window, again no cloud predicted for nearly the whole of the UK so unless this high cloud is pretty thick then it is unlikely to spoil the day, well except for that nagging wind in the south.

      

Moving beyond this, the models still moving along the same page, an unsettled spell across most of the UK at the end of this week and into the first part of the weekend before high pressure builds back into the south at the very least, rain could be possible in the north though at times, conditions do look to be on the mild side for the most part.

 

[Frosty.]

Looking further ahead, following a brief cooler unsettled atlantic blip later in the week, the GEFS 00z mean shows the azores high again ridging into the uk with another warm settled spell for the south..in the meantime, enjoy the current perfect spring weather.

Edited March 26, 2017 by Frosty.

[AWD]

Agreed CS.  That's what I was trying to say but in an overcomplicated way.

The cloud cover forecast by some NWP models is mainly high level cloud doing nothing but making the sunshine a bit hazy in places at times.  Hence why the cloud cover is only forecast around the 20% mark for most.

Cloud cover forecasts are never going to be spot on due to topographic local conditions for which the grid of most modelling won't be fine enough to take into account.

To put it bluntly, most modelling is modelling some degree of high level cloud for many, but nothing that is going to ruin a few pleasant & sunny days so all in all, it's pretty negligible.

[Singularity]

I suspect models like GFS in particular overdo the blocking or scattering effect of high cloud on solar rays; yesterday it was a massive 4.5*C too low with the maximum here - the worst error in a very long time - having only depicted mostly high cloud.

Another factor for places within 10-30 miles of the coast is likely the inland extent of cooling by the sea being overestimated. Reality sees inland heating becoming dominant sooner inland than the model shows. I have also seen WRF-NMM do this to an even greater extent.

[knocker]

This doesn't get covered by the models either.

It's a nice day here, albeit the wind is a bit of a nuisance gusting 35mph. I suspect it's the usual problem with the wind in this direction where the SW tends to be enhanced by flowing over the carns that are to the  ESE. The low level inversion almost certainly has something to do with it as well. Assuming it's still there on the 12z sounding

 

[Frosty.]

Nice end to the Gfs 6z with high pressure dominant and plenty of mild / very mild weather during the week ahead.

Edited March 26, 2017 by Frosty.

[knocker]

Currently about 5/8 Ci here, gusting 40mph and haze with temp of 11C. Oh GFS you are sorely maligned.

High res. Modis 1233 courtesy Dundee Sat.

Edited March 26, 2017 by knocker

[Nick L]

I've been critical of the GFS plenty of times, but I think some are being harsh regarding its cloud forecasts. There are a fair few sheets of thin, wispy high cloud here making the sunshine hazy at times, and going by the GFS there was a reasonable amount of high cloud forecast (all charts in oktas): 

However, it correctly forecast that there would be no medium or low cloud (GFS is very poor at predicting low cloud, it should be noted):

In fact, I'd say it has done better than the EC in terms of the high cloud

Edited March 26, 2017 by Nick L

[Frosty.]

Following an unsettled blip towards the end of the week ahead the GEFS 6z mean shows high pressure building in again, at least across southern uk with a return to predominantly fine and pleasantly warm conditions..so it becomes a north / south split with the north generally more changeable..in the meantime, enjoy the glorious weather..and the wispy cirrus

Edited March 26, 2017 by Frosty.

[frosty ground]

Plenty of high cloud today and the wind has a real edge to it but if we ignore these observations we can say it's a perfect day.

 

[I remember Atlantic 252]

Good charts Frosty, but I'm still monitoring April 3, has shown up on many runs as a shocker, as on the 00Z, a strong possibility I think

[cheese]

Just now, frosty ground said:

Plenty of high cloud today and the wind has a real edge to it but if we ignore these observations we can say it's a perfect day.

 

14C, sunny, light winds. Yes, it's a great day.

[Frosty.]

3 minutes ago, cheese said:

14C, sunny, light winds. Yes, it's a great day.

Even warmer through the next week..plenty of fine and sunny weather too, until later in the week, best for longest further SE.

 

Edited March 26, 2017 by Frosty.

[knocker]

4 hours ago, knocker said:

This doesn't get covered by the models either.

It's a nice day here, albeit the wind is a bit of a nuisance gusting 35mph. I suspect it's the usual problem with the wind in this direction where the SW tends to be enhanced by flowing over the carns that are to the  ESE. The low level inversion almost certainly has something to do with it as well. Assuming it's still there on the 12z sounding

 

 

Further to this the Camborne 12z sounding Not only that it's quite moist at 30,000 feet.

Sidney took advantage of a gap in the Ci and a lull in the wind

Edited March 26, 2017 by knocker

[Frosty.]

Somewhere in the SE would reach 19 or 20c on thursday according to the Gfs 12z..maybe even the first 70f of the season!..roll on summer 

Very pleasant for most of the week ahead, temperature wise at least. There will be some warm sunshine but an increasing risk of showers on tuesday before atlantic weather and a drop in temperatures pushes across the uk towards the end of the week.

P.S...some Highland Glen's reached 20c this afternoon.

Edited March 26, 2017 by Frosty.

[knocker]

Not much to add to this morning's brief synopsis. With the upper trough continuing to head east the weather will become more unsettled from around Wednesday with low pressure in situ by Friday. So some showery interludes but temps remaining on the up so not unpleasant before ridging once more on Sunday before the next Atlantic fronts arrive early next week.

Edited March 26, 2017 by knocker

[I remember Atlantic 252]

1 hour ago, Frosty. said:

Somewhere in the SE would reach 19 or 20c on thursday according to the Gfs 12z..maybe even the first 70f of the season!..roll on summer 

Very pleasant for most of the week ahead, temperature wise at least. There will be some warm sunshine but an increasing risk of showers on tuesday before atlantic weather and a drop in temperatures pushes across the uk towards the end of the week.

P.S...some Highland Glen's reached 20c this afternoon.

GEM great Frosty! FI shame as well rubbish model

[I remember Atlantic 252]

ECM good too, need high ideally further NW, but potentially warm here

[Frosty.]

Most of the week ahead indicates above average temps but they drop next weekend so feeling a lot cooler than this weekend's afternoons have been. The Ecm 12z shows an unsettled interlude later in the week but the azores high starts ridging in from sunday and tropical maritime air floods around the top of it and across the uk to start the following week and high pressure brings a return of fine warm weather..T+240 looks very nice.

Edited March 26, 2017 by Frosty.

[snowray]

1 hour ago, Frosty. said:

Somewhere in the SE would reach 19 or 20c on thursday according to the Gfs 12z..maybe even the first 70f of the season!..roll on summer 

Very pleasant for most of the week ahead, temperature wise at least. There will be some warm sunshine but an increasing risk of showers on tuesday before atlantic weather and a drop in temperatures pushes across the uk towards the end of the week.

P.S...some Highland Glen's reached 20c this afternoon.

We actually got a 20c today, and of all places it was recorded at Aviemore!, with Aboyne hitting 19c again, can't see temps as high as that for some time to come in Scotland.

ECM looking good for early April though.

[Frosty.]

5 minutes ago, snowray said:

We actually got a 20c today, and of all places it was recorded at Aviemore!, with Aboyne hitting 19c again, can't see temps as high as that for some time to come in Scotland.

ECM looking good for early April though.

Yes I hope the Ecm 12z is right about another anticyclonic spell during early April..this weekend has been fabulous even with the much discussed cirrus clouds.

Edited March 26, 2017 by Frosty.

[phil nw.]

Our pleasant early Spring sunny spell looks like ending by midweek as a complex area of low pressure out in mid-Atlantic sends bands of showery rain up across the country by Wednesday.

It doesn't look a complete washout though by any means with sunshine between the showers and temperatures holding up quite well as winds veer around to the south and south west.

[gottolovethisweather]

1 hour ago, Frosty. said:

Yes I hope the Ecm 12z is right about another anticyclonic spell during early April..this weekend has been fabulous even with the much discussed cirrus clouds.

It cirrusly has been fabulous, hasn't it. The birds they've been a singing and I expect to see a few migrant Swallows and a few more incoming warblers nationwide ahead of next week's southerly drift. Nothing but blue skies......

Edited March 26, 2017 by gottolovethisweather

[Frosty.]

Good news is tonight's Ecm 12z ensemble mean follows the op and shows there is good support for high pressure to build in from the southwest again. There is an unsettled blip on the way but things could again be looking a lot more promising through early April and dare I say the run up to Easter could be settled..hopefully!

Edited March 26, 2017 by Frosty.