Model Output Discussions 12z 08/03/17

[Eugene]

Looks like GFS 12Z is moving towards ECM with high pressure retrogressing northwestwards, cool and unsettled last week of April seems likely.

[Singularity]

The HLB signal for the week after next seems different to those that have gone before in that it appears to be predominantly a response to the final warning event in the stratosphere - or at least the onset is. Spurious MJO activity in the GEFS projections may be leading to overly aggressive retention of a UK-based trough beyond day 12 or so.

[Frosty.]

The Arctic floodgates open wide at the end of the Gem 12z as we see retrogression. Even the Gfs 12z shows a risk of snow during low res.

Edited April 15, 2017 by Frosty.

[I remember Atlantic 252]

Awful charts Frosty, but feel GEM could be correct, as last April saw a horrendous end, expect same this year, didn't even see 1mm of snow

we all know, nowadays, last 19 years or so, that these charts are so rare in 'winter', even if we do get this setup, will be less cold than 90's, with only wet snow at best in South

Edited April 15, 2017 by I remember Atlantic 252

[Frosty.]

The Ecm 12z looks largely fine and dry during the week ahead as high pressure builds in and we should all see pleasant sunny spells but with some cold frosty nights and for gardeners they are likely to be damaging in places but it's a nice benign week ahead on the whole. The settled spell continues into week 2 with high pressure the main feature.

Edited April 15, 2017 by Frosty.

[Summer Sun]

1 hour ago, Eugene said:

Looks like GFS 12Z is moving towards ECM with high pressure retrogressing northwestwards, cool and unsettled last week of April seems likely.

And right on cue ECM comes up with something different with high pressure close enough to us to keep the coldest winds over in Scandinavia

[Frosty.]

1 minute ago, Summer Sun said:

And right on cue ECM comes up with something different with high pressure close enough to us to keep the coldest winds over in Scandinavia

I had a feeling the Ecm would do this and true to form it has..but it's good news for those of us who like dry weather and sunshine.

[Frosty.]

Well tonight's Ecm 12z ensemble mean is still bullish about retrogression and an increasingly cold unsettled extended outlook from the north after next weeks largely settled spell.

Edited April 15, 2017 by Frosty.

[Singularity]

Hmm yes - retrogressive forcing is so strong in the ECM 12z that the low which has on most recent runs dropped into the west flank of the Scandi trough days 8-10 is instead held back to our NW for so long that a new ridge establishes across the UK.

If in reality the trough gives us a miss it will add to a growing funny suspicion of mine that the time to anticipate a breakdown in the weather a week or so from the current day is in fact when the models aren't showing a trough moving right over us in the 8-10 day range, due to the propensity for troughs to adjust either west or east nearer the time.

Which of those days it goes can't be second-guessed though so this doesn't help forecasting much.

[Eugene]

2 hours ago, Frosty. said:

Well tonight's Ecm 12z ensemble mean is still bullish about retrogression and an increasingly cold unsettled extended outlook from the north after next weeks largely settled spell.

 

GFS 18Z OP finally fully on board frosty with the retrogression theme.  

[Man With Beard]

Any rainfall records up for grabs this month? Latest GFS struggles to get 5mm of rain for S/W areas by D10, and some areas barely 1mm. My personal weather station has recorded a full 0.5mm this month so far. 

Too early to call a drought?

[Weather-history]

12 hours ago, I remember Atlantic 252 said:

we all know, nowadays, last 19 years or so, that these charts are so rare in 'winter', even if we do get this setup, will be less cold than 90's, with only wet snow at best in South

January 2010 and December 2010 were colder than any month of the 90s.......March 2013 and April 2012 were colder than any of the Marches and Aprils of the 90s.....

Edited April 16, 2017 by Weather-history

[Weather-history]

11 minutes ago, Man With Beard said:

Any rainfall records up for grabs this month? Latest GFS struggles to get 5mm of rain for S/W areas by D10, and some areas barely 1mm. My personal weather station has recorded a full 0.5mm this month so far. 

Too early to call a drought?

At a local level maybe but I think the all time record of April 1938 looks probably safe. 

[Summer Sun]

ECM has flipped back to a cold plunge towards the end of the month dream charts for coldies 4 to 6 months too late

[johnholmes]

To the models, well anomaly type

It is hard to be too sure just what 6-14 days ahead the upper air is going to look like. The anomaly charts are far from consistent over the past week. All, I use, showing variations. However, the overall idea suggests no marked warmth. They have shown various patterns with the ridge perhaps the main player, sometimes on its own, and very close in to the western edge of the B Isles, sometimes with the trough east of it as a significant player.

see the links below for the last issues from the 3.

http://www.cpc.noaa.gov/products/predictions/610day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

 

Edited April 16, 2017 by johnholmes

[Eugene]

7 hours ago, Summer Sun said:

 ECM has flipped back to a cold plunge towards the end of the month dream charts for coldies 4 to 6 months too late

 

Long term averages show snowfall in April to be very similar to November, snowfall isn't that uncommon for northern britain even in May, models all seem to show a cold last week to April with greenland/mid atlantic blocking.

Edited April 16, 2017 by Eugene

[Summer Sun]

Knifedge stuff for next weekend a slight shift either way to that high will make huge differences to what weather we get

[Sky Full]

I do not like the look of this suggestion from the GFS:

   

Surely we don't want these conditions to verify at the end of April, just when a hard frost could do serious damage in the garden?

The ECM tells a similar story though...

   

I am hoping these predictions will be seriously moderated in the next few days....

 

[Weather-history]

18 minutes ago, Sky Full said:

 

Surely we don't want these conditions to verify at the end of April, just when a hard frost could do serious damage in the garden?

 

 

Damage may have already been done, frost possibilities Tuesday morning

Edited April 16, 2017 by Weather-history

[ANYWEATHER]

Good Easter Folks, What does stand out is two things ,Dry and Cold.....in the ten day period. .Farmers and Growers  will be not happy with the outlook , some damaging frosts with low dewpoints  . low humidity and virtually no rain , a warming up by Friday and then a deluge of cold from the north  .repeat and rinse....and our neighbours just  to the east  of us will bear the worst,, Apart from the odd day of spring warmth we will see  below average temps..... We have certainly got a Positive Artic Ossilation  sending the cold well south which often happens this time of year!

[Polar Maritime]

The GFS this morning shows reloads from the North into Wk2, With some pretty cold air filtering South over the UK at times.

 

 

[Summer Sun]

ECM shows a bit of a battle developing during the final week of April what looks a decent bet is it will be on the cooler side of normal what is a bit uncertain is where the high and low will sit

A hint of something milder as we move towards May as the high finally manages to shift a bit further east

[Man With Beard]

2 hours ago, Polar Maritime said:

The GFS this morning shows reloads from the North into Wk2, With some pretty cold air filtering South over the UK at times.

 

 

Looks like the pattern change really is on now. Just in time for the "hotter" part of the year! I fear that having taken so long to get a north Atlantic height anomaly, in the absence of a winter polar jet it may take a while to get rid of it. BBQs probably not needed for the turn of the month and I'm guessing for some time after that.

[cheshire snow]

No comments on the 12z GFS,Some dream winter charts at day nine with widespread 

Snow fully understand why people are not interested in such set ups at this time of year

But as this is the Model Output thread I thought it worth a mention 

C.S. 

[snowray]

ECM says no, just turning a bit colder again.

 D8,D9 & D10.