Model output discussion - 20th Feb onwards

[stainesbloke]

2 hours ago, Nouska said:

Mid-day Bank holiday Monday - not looking at all nice in the south. Still a bit of fine tuning in regard to placement (and possibly strength).

   ensemble mean 

Latest GFS has Monday's storm further south, with gales missing us and hitting N France, Benelux etc with southern parts just getting very wet. 

[Milhouse]

Looks like a bit of a battle emerging next week between warm air from the south and cold air from the Arctic. The GFS 0z showed the warm southerlies winning out, while the 6z had more of a cool northeasterly.

http://www.wetterzentrale.de/pics/Rtavn1501.html

 

 

Edited March 24, 2016 by Milhouse

[knocker]

Wet and windy Saturday and the track of Monday's depression is critical.

[phil nw.]

A cyclonic outlook for the Bank holiday

Looking like a very changeable week coming up generally with bands of rain or showers.Some brighter skies between which i suppose beats the days of grey gloom many of us have experienced under the now departed high.  

[stodge]

Afternoon all

UKM, GFS and GEM 12Z OP output continue with the very unsettled them for the immediate future with a vigorous secondary depression crossing the south on Monday before curving NE on Tuesday and then stalling off NE Scotland.

The medium term evolution then  depends on how that storm system leaves the UK. GFS and GEM offer the possibility of a build of HP from the Azores through the British Isles combining with heights rising to the north which offers the possibility of a fine weekend to begin April before, well, who knows ? Once again we are tantalised by GFS FI with and E'ly followed by a retrogression and an Arctic outbreak.

We'll see...

The certainty of a deteriorating Bank Holiday does look, I'm afraid, nailed. Good Friday should be okay for many but after that not too pleasant for a lot of people.

 

[Daniel*]

The bank holiday storm could be quite nasty

UKMO T+96 a tight gradient in the isobars for South East England, severe gales based on this any upgrades on the wind speeds it would be concerning.

watch this space 

[Man With Beard]

It's still the outsider, but the GFS has once again pulled a spring-like scenario out of the general pattern in its latter stages:

[stodge]

Indeed and this was the equivalent from the 06Z OP:

Very small differences in position between the weather systems can have a huge effect between a warm SE'ly and a cool E'ly. Plenty to resolve on the detail but the general pattern for early April is starting to firm up.

 

 

 

 

[knocker]

As has already been noted previously

 

[Milhouse]

ECM also likes the stalling low to the west of the UK idea.

 

Edited March 24, 2016 by Milhouse

[johnholmes]

6 hours ago, stainesbloke said:

Latest GFS has Monday's storm further south, with gales missing us and hitting N France, Benelux etc with southern parts just getting very wet. 

I can't see it going there looking at the predicted T+96 on all 3 models. Looking at the 500mb flow, as it is now, also the Fax chart showing it at 987mb and the direction of the warm sector isobars. All suggest it somewhere over E/SE England during Monday. Hard to say where it will exit into the N Sea, anwyhere between the Humber and Thames estuary is the best I could suggest at the moment. As with most lows the worst winds will probably occur in its SW sector. An interesting forecast dilemma for another 24 hours maybe 36 or so?

[knocker]

There is good agreement between the GEFS 5-10, ecm same and NOAA 6-10 so as I've already posted the GEFS let's move on.

GEFS 10-15 is still trying build heights over Greenland whilst keeping a ridge mid Atlantic with the trough to the SW of the UK. The EPS is still not keen on building heights to that extent over Greenland but does have a stronger ridge mid Atlantic. The trough to the east is over the UK running south into southern Europe. Thus quite interesting with low pressure to the south and HP edging in from the west makes a difficult call with perhaps a SE flow for the south with some unsettled weather with the north maybe picking up the anticyclonic circulation and remaining drier and more settled.

[johnholmes]

8-14 NOAA below

http://www.cpc.noaa.gov/products/predictions/814day/500mb.php

The W'ly flow into the UK somewhat different from 2-3 days ago as it now shows marked troughing just west of the country. It also shows signs, commented on last night re other models for about the same date, suggesting +ve heights beginning to show of the east coast of N America and also over Greenland

[Singularity]

Not sure how much we can trust any particular model at the moment, but the GFS-based 2m anomaly maps for days 6-10 and 11-15 caught my eye on tropicaltidbits.com;

 

Amazing that the U.S. is the only continent with notably below average conditions affecting more than a % or two of the landmass. 

Essentially, all of the cold air ends up focused over the U.S., as yet another major cold wave (relative to average) affects the region. Many recent winters have featured such events - for some reason the polar heights have been tending to align in a way which favours such a thing, though usually there is an export to the Asian side too, which is notably lacking this time around.

Conditions are looking pretty crazy at the other end of the scale across most of North Africa by the 11-16 day period. Such a widespread early build of heat puts me on European heatwave alert for late spring and the summer, not so much in terms of their likelihood but their potential severity should the broad scale pattern allow them in the first place.

Yet even that can't compare with the anomalies shown over Greenland, which are a reflection of the idea of height rises in the vicinity of Scandinavia which then slowly retrogress, this being something GFS/GEFS seem very keen on while ECM has not really been there but appears to have moved toward to some extent with the 12z effort.

I'm not sure, but this might be just about the worst case scenario for the Arctic sea ice during the first 10-14 days of the melt season. By exporting so much cold air to just the one region at this time of year, the door is left open for imports from a generally well above average rest of the N. hemisphere landmass. 

Meanwhile there are interesting implications for the UK; there is an abundance of unseasonably warm air to tap into, which means that an exceptionally warm day (e.g. mid-20's across a wide area of the south) is a lot more achievable than unusual. It just needs the right alignment of the troughs and ridges ahead of the retrogression of that Scandi High- assuming such even comes around; the models (both det. runs and ensembles) have seemed a bit too keen with that sort of thing over the past few months. If it does happen though, we could see both a date record maximum and a date record minimum in the same month. I believe such a thing has actually happened quite recently - in July last year?

[knocker]

A quick look at the means from the latest EC32 update

On the 6th April we have the cold trough NE N. America, a ridge in the western Atlantic with some height rises over Greenland. In the eastern Atlantic the main player is a trough situated SWS of the UK running down to North Africa. Thus quite meridional with a light upper southerly drift over the UK. but with the surface low to the south a light E/SE would ensue bringing the likelihood of some varied unsettled weather over the south with temps a little above average maybe. The north for once getting the better of the deal.

The scenario of the trough to the south of the UK remains through to the 11th with a general area of low pressure over the UK and Europe which again portends the more unsettled weather to be in the south but it's certainly not all doom and gloom with more pleasant drier interludes and temps varying around the average.  However changes have been occurring upstream with the ridge in the western Atlantic no more

This heralds the arrival of another trough which is in mid Atlantic by the 17th which brings the UK back into a WSW flow and a likely return of periods of unsettled weather from the west. Temps around average.

Later in the month perhaps more influence from the Azores high.

Looks like some typical April weather.

The latest GFS take for Monday.

Edited March 25, 2016 by knocker

[johnholmes]

The uncertainty in the models and the Fax charts remains this morning. All now seem to have decided against any possibility of it staying south over northern France. The idea of it exiting somewhere between the Humber and the Thames estuary that seemed favourite yesterday has been shift by all 3 main models to north of the Humber, currently around Newcastle looking the most likely. 

The T_84 Fax chart issues by Met at 0547 this morning gives their latest ideas. Just north of the Humber centre 969mb from its value of 1001mb on Sunday 00Z around 47N32W, so a fair amount of deepening expected. This helps turn it left of its track and looks okay looking at the 300mb predicted flow with it embedded in the jet and exiting in what looks like the left exit region.

[knocker]

With ref. to the EC32 above for the 7th this morning's GEFS if very similar with the trough a tad further west.

 

 

Edited March 25, 2016 by knocker

[Nouska]

I wonder if the Met office will give this low a name even if we are now no longer in winter. Looks to have the potential for nasty impacts on a densely populated area in the middle of the day.

Talking of winter, probably as well that the winter crew have departed - how frustrating to see synoptics as shown in the low-res GFS.

... the long awaited effects of the MMW (or is it now classed as the final warming) are being seen at last.

 

Edited March 25, 2016 by Nouska

[Paul]

Nick has written an in depth synoptic analysis blog, looking at the active and potentially stormy weather this weekend. 

http://www.netweather.tv/index.cgi?action=news;storyid=7246;sess=

[johnholmes]

A very well presented outline of probable events there Nick - thank you

 

[knocker]

9 minutes ago, johnholmes said:

A very well presented outline of probable events there Nick - thank you

 

Ditto.

[Nouska]

3 hours ago, Paul said:

Nick has written an in depth synoptic analysis blog, looking at the active and potentially stormy weather this weekend. 

http://www.netweather.tv/index.cgi?action=news;storyid=7246;sess=

It's a shame the blog does not offer a 'like' option - that is definitely a post worthy of up votes.

Edit to add .... 06Z Arpege takes the low in a little bit further north - nasty swathe of gust potential on the southern coast.

   

Edited March 25, 2016 by Nouska

[stainesbloke]

17 hours ago, johnholmes said:

I can't see it going there looking at the predicted T+96 on all 3 models. Looking at the 500mb flow, as it is now, also the Fax chart showing it at 987mb and the direction of the warm sector isobars. All suggest it somewhere over E/SE England during Monday. Hard to say where it will exit into the N Sea, anwyhere between the Humber and Thames estuary is the best I could suggest at the moment. As with most lows the worst winds will probably occur in its SW sector. An interesting forecast dilemma for another 24 hours maybe 36 or so?

Yes, it looks like the SE will get battered by some quite dangerous winds on Monday sadly  Plenty of rain too. Must be a Bank Holiday?!

[DR(S)NO]

Could be wrong , but it was my understanding that storms would be named more for their impact rather than the time of year.....i wonder whether this one warrants a name. Where are we at anyway regarding names? ...Do we restart the alphabet later in the year?

[andymusic]

2 hours ago, DR(S)NO said:

Could be wrong , but it was my understanding that storms would be named more for their impact rather than the time of year.....i wonder whether this one warrants a name. Where are we at anyway regarding names? ...Do we restart the alphabet later in the year?

Storm Katie to arrive on Easter Monday

 

25 March 2016 - Storm Katie is forecast to affect southern England and south Wales on Easter Monday