Model output discussion - 20th Feb onwards

[knocker]

The GFS still nipping the depression down over the UK

[phil nw.]

Some particularly cold air coming south next week in the Arctic flow.

A look at temperatures at 500hPa for day 4 from the 06zGFS shows a notable upper cold pool coming down the Norwegian sea.

 

Temperatures forecasted at around -40C which is around Polar low* territory so i wouldn't be surprised to see something of that kind around the north east of the UK.This could well give enhanced possibilities of an area of snow, especially but not exclusively,higher up.The N.Isles and the Northern part of Scotland,highlands etc would be favoured most as it stands in the latest GFS run.

those images again from the GFS06z.

Being 4 days away of course there is still room for some changes but certainly it can be said this coming week will be notable for the depth of the cold pool given the time of year with quite possibly a taste of Winter in the north with some lying snow in places. 

*Polar low-link.  https://en.wikipedia.org/wiki/Polar_low

 

 

 

 

Edited April 22, 2016 by phil nw.

[carinthian]

30 minutes ago, phil nw. said:

Some particularly cold air coming south next week in the Arctic flow.

A look at temperatures at 500hPa for day 4 from the 06zGFS shows a notable upper cold pool coming down the Norwegian sea.

 

Temperatures forecasted at around -40C which is around Polar low* territory so i wouldn't be surprised to see something of that kind around the north east of the UK.This could well give enhanced possibilities of an area of snow, especially but not exclusively,higher up.The N.Isles and the Northern part of Scotland,highlands etc would be favoured most as it stands in the latest GFS run.

those images again from the GFS06z.

Being 4 days away of course there is still room for some changes but certainly it can be said this coming week will be notable for the depth of the cold pool given the time of year with quite possibly a taste of Winter in the north with some lying snow in places. 

*Polar low-link.  https://en.wikipedia.org/wiki/Polar_low

 

 

 

 

Phil, that's some impressive depth of cold air . Currently +12 c here today in spring like sunshine. Just been given a heavy snow warning for early next week with sub zero maximum temps -11c at 2000m. Might have to bring my snowmobile out of the shed !

 C

[phil nw.]

18 minutes ago, carinthian said:

Phil, that's some impressive depth of cold air . Currently +12 c here today in spring like sunshine. Just been given a heavy snow warning for early next week with sub zero maximum temps -11c at 2000m. Might have to bring my snowmobile out of the shed !

 C

Yes C it looks like a last fling from the Arctic for Europe/UK. 

A look at the latest ens surface temperature forecasts for the next few days.

shows quite a -ve anomaly as much 5/6C for C.Europe so looks like a good top up of snow for the skiers over there.Time to dig out the extra layers again C.

 

[knocker]

And of course we all remember the 23rd -27th April 1981, the snow I was on a train from Glasgow.....but no......that's another story and wrong thread

[knocker]

As i was saying...............well at least the last three runs have been consistant

[Cheshire Freeze]

10 hours ago, mb018538 said:

UKMO in their update last night seem fairly bullish about things changing in the 10 day range, with higher pressure moving in. It does appear that this northerly isn't going to stay around forever, and something will change at the turn of the month.

Just to add, the extended ECM and associated ensembles look promising this morning after May begins.

Just seen the GFS 12z output for early May...

Chilly...

[karyo]

Just now, CreweCold said:

Just seen the GFS 12z output for early May...

Chilly...

A never ending Arctic attack! lol

[knocker]

Not a total surprise but the ecm is not in agreement with the GFS. It is swivelling and weakening the upper trough and generally moving the centre NW and pushing the HP up from the SW. This is the pattern transition period so detail will be elusive at this range. It does introduce a shallow feature Thursday so the middle of the week remains interesting.

 

[andymusic]

2 hours ago, karyo said:

A never ending Arctic attack! lol

At this rate - summer will last all of "Blink and you'll miss it" 2 days - and then we'll be on our way back to xmas again lol

 

Edited April 22, 2016 by andymusic

[Snowy L]

5 hours ago, phil nw. said:

Yes C it looks like a last fling from the Arctic for Europe/UK. 

A look at the latest ens surface temperature forecasts for the next few days.

shows quite a -ve anomaly as much 5/6C for C.Europe so looks like a good top up of snow for the skiers over there.Time to dig out the extra layers again C.

 

and first

[ANYWEATHER]

Good Evening All, so now we had no Winter , Now we have no Spring.....!!!

[knocker]

NOAA and the ecm anomalies are in pretty good agreement on the evolution and the pattern change to zonality and a familiar interaction between systems running east and the Azores HP popping it's head from time to time.

The 5-10s both show the upper trough swinging NW with strong ridging western Russia, upper low NW Canada and weak ridging mid Atlantic. Thuis the upper winds backing NW so still unsettled and temps remaining below average.

In the 8-13 period with upper trough associated with the UK weakening the flow backs further and both show a westerly regime as mentioned at the beginning of the post.

So although we have a pattern change way from the Greenland block/eastern trough scenario to a more Atlantic driven one there is no immediate panacea regarding more settled and warmer weather. Certainly getting warmer with temps gradually rising but remaining depressed and the weather still unsettled. It's not looking that clever for the Bank Holiday at the moment.

[knocker]

This morning's GFS run just confirms what we all know that next week is going to be cold and wintry, more especially in the north and east, with low pressure to the east tracking NW later. Before the Atlantic nudges in next weekend that portends drier and warmer weather without getting exactly hot, The timing of this is crucial vis the Bank Holiday.

Oh and Sidney got quite excited when he glimpsed this chart

Edited April 23, 2016 by knocker

[Polar Maritime]

GFS take on next Fridays Low pushing S/E.

Edited April 23, 2016 by Polar Maritime

[knocker]

Looking at the ecm's take on the Bank Holiday doesn't fill one with optimism. it has the HP pushing in from the SW 00 Saturday but very quickly fronts associated with a system rapidly tracking in from the west take over and are situated over the UK 12z Sunday with some very very conditions.Of course there is still plenty of time for a rethink.

[damianslaw]

Well the long awaited change to colder arctic airstream has set in, the coldest uppers are forecast for Tuesday/Wednesday, in the main though the outlook isn't too bad if you like fairly dry settled conditions, its no rain fest... There will be showers around more so in the north and east but as ever they are difficult to forecast, some places could get a wintry mix, others will stay dry more so the SW.

It does look like being quite a lengthy cold plunge, trough features could form out of nowhere and it is ripe territory for shortwave mesoscale disturbances - cyclonic conditions could develop as hinted at by some of this morning's models increasing the chance of notable wintry precipitation in places, low level snow can't be ruled out..

The main notable feature will be the cold minima, very cold for late April, some places could see a 5 day run of minima below 0 degrees a tough act to achieve in the depths of winter.

Longer term - no definitive signal of a change in overall pattern, a cool dissapointing start to May could be on the cards.

[knocker]

Rather depends what you mean by definitive signal but a pattern change with the erosion of the Greenland block and a return to a more zonal flow has been indicated for some days.There might just be a little variance on timing. This does not mean that temps will rocket upwards as they will remain a little below average

The ecm take on this this morning is the process gets under way towards the latter end of next week with troughs over the western Atlantic and the UK with ridging mid Atlantic. The UK still just under the influence of the upper low but quite rapidly after that with the weakening of the upper low the upper flow backs to the NW portending unsettled weather arriving from the west particularly for the north of the UK and probably a forerunner of the interplay between the Azores HP and systems travelling east.

[Faronstream]

2 hours ago, knocker said:

Rather depends what you mean by definitive signal but a pattern change with the erosion of the Greenland block and a return to a more zonal flow has been indicated for some days.There might just be a little variance on timing. This does not mean that temps will rocket upwards as they will remain a little below average

The ecm take on this this morning is the process gets under way towards the latter end of next week with troughs over the western Atlantic and the UK with ridging mid Atlantic. The UK still just under the influence of the upper low but quite rapidly after that with the weakening of the upper low the upper flow backs to the NW portending unsettled weather arriving from the west particularly for the north of the UK and probably a forerunner of the interplay between the Azores HP and systems travelling east.

Where do you see any signs of heat/warmer temperature than average? I only see rather chilly and humid air as long as the models can see

[knocker]

3 minutes ago, Faronstream said:

Where do you see any signs of heat/warmer temperature than average? I only see rather chilly and humid air as long as the models can see

I don't. Where have I said that? My last post, "This does not mean that temps will rocket upwards as they will remain a little below average" But I don't think the air will be particularly humid later in the runs.

Edited April 23, 2016 by knocker

[AWD]

Chilly & humid?  That's an interesting combination.

[Weather-history]

An incredible chart, how often do you see a developing low with very cold air wrapping round it....and at the end of April?

 

Edited April 23, 2016 by Weather-history

[Milhouse]

The GFS 12z brings more settled conditions in during the first few days of May. Temperatures in no great shape but least there is no pool of cold air to the north so no plunge of cold air on this occasion. Fingerst crossed may will produce something warmer, it cant be difficult.

 

 

[Polar Maritime]

This evenings take on Fridays Low moving S/E. Some pretty unstable air in the mix..

 

Edited April 23, 2016 by Polar Maritime

[Eugene]

9 hours ago, damianslaw said:

Well the long awaited change to colder arctic airstream has set in, the coldest uppers are forecast for Tuesday/Wednesday, in the main though the outlook isn't too bad if you like fairly dry settled conditions, its no rain fest... There will be showers around more so in the north and east but as ever they are difficult to forecast, some places could get a wintry mix, others will stay dry more so the SW.

It does look like being quite a lengthy cold plunge, trough features could form out of nowhere and it is ripe territory for shortwave mesoscale disturbances - cyclonic conditions could develop as hinted at by some of this morning's models increasing the chance of notable wintry precipitation in places, low level snow can't be ruled out..

The main notable feature will be the cold minima, very cold for late April, some places could see a 5 day run of minima below 0 degrees a tough act to achieve in the depths of winter.

Longer term - no definitive signal of a change in overall pattern, a cool dissapointing start to May could be on the cards.

 

Great summary, i think May will be disappointing with milder moister air giving localised flooding, at least up until friday its looking better with colder drier air, this impressive Greenland high setup could be the best we have until next Spring, as we all know those unsettled SW'lys are alot more common Nov to March than in April/May when they are at their weakest.