Jump to content
Cold?
Local
Radar
Snow?

Model Output Discussion - Stormy Period Inbound...


Recommended Posts

Don't like looking too far ahead but next week at T+132 looks very interesting indeed - this coupled with probable good ppn for Alba Cumbria and the Pennines this weekend.

 

post-6879-0-99738000-1420712552_thumb.pn

 

All Good.

 

Ian


It could be that the double / triple whammy of storms about to batter the far north in the coming days will be the catalyst for a progressively colder and wintry pattern to become established during the weeks ahead. Those storms look fierce, 90-100 mph with Amber warnings already in force..take care up there.

 

Yes Karl - next week looks particularly promising from this weekends events.

 

Ian

  • Like 2
Link to post
Share on other sites
  • Replies 1.8k
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

Righty-Ho. This can't pass without comment. Below follow just a random snapshot of detailed medium range briefings from Ops Centre made in first days of Jan, looking towards what was then the 10-15d

Je suis charlie

A bit of clarity re EC Monthly prognosis and expectations further ahead. The broad scheme of things sees a shift in balance re lows to NW becoming more aligned further away to the north from the UK, u

Posted Images

The snapshot clusters at around that time (T372) supports that mean. Only 20% (cluster 4) go with the more amplified flow with the 528 dam in the Midlands. 25% has HP over the UK and 55% go with the zonal flow:

 

attachicon.gifweather_model_gfs_ensemble_-_europe_-_surface_pressure_cluster__base___372___base__08-01-2015_00_gmt__-_weatheronline.jpg

.

Funny I read that rather differently...... They all look Zonal..... but only 25% have the wind coming form a south of westerly direction...... AKA Cool and below average for the other 75%.

  • Like 3
Link to post
Share on other sites

Funny I read that rather differently...... They all look Zonal..... but only 25% have the wind coming form a south of westerly direction...... AKA Cool and below average for the other 75%.

 

Looking at 2m temp highs for midday (not the warmest time of day) at T372 they look mainly average with the colder cluster being the last one, as per pre post:  

 

post-14819-0-61932200-1420713200_thumb.j

 

A westerly flow is more likely to mix PM and TM so I cannot see anything but transient cold coming from that setup.

Link to post
Share on other sites

Really - Around 511 dam thickness but it's maybe 700 miles west of Ireland !

 

When commenting on the 510 LINE, Im assuming you mean the 2 key isopleths we use for snow ( 528 & 510 DAM)

 

ECM day 8 chart doesnt show that low thickness-

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015010800/ECM1-192.GIF?08-12

 

If your looking at the 990 LOW -

 

& the thickness is

Roughly 500 height-((SLP-1000)*0.8  )

The height is 508 DAM adding on around (990-1000 X0.8 = 8 DAM

 

is net 516 DAM.

This is echoed by the GFS

http://www.wetterzentrale.de/pics/Rtavn1923.gif

Which is closer to the 528 LINE

 

But whos splitting hairs.- its quite low.

 

As for the outlook, cold zonality seems to be winning the war today- possibly some amplification at day 10-

S

Edited by Steve Murr
  • Like 5
Link to post
Share on other sites

ECM day 8 chart

 

http://www.meteociel.fr/modeles/ecmwf/runs/2015010800/ECM1-192.GIF?08-12

 

If your looking at the 990 LOW -

 

& the thickness is

Roughly 500 height-((SLP-1000)*0.8  )

The height is 508 DAM adding on around (990-1000 X0. 8) = 8 DAM

 

is net 516 DAM.

 

But whos splitting hairs.- its quite low.

 

As for the outlook, cold zonality seems to be winning the war today- possibly some amplification at day 10-

S

 

 

your .8 has come out as a smiley-does this all the time!

  • Like 2
Link to post
Share on other sites

would that be 100mph gusts?

Amanda

Can you pop on what area you live in?  Maybe folk can help you more then.  Expect the south to be more storm affected at and after mid month.  Mucka good post, conditions will vary greatly.

 

BFTP

Edited by BLAST FROM THE PAST
  • Like 2
Link to post
Share on other sites

I have been seeing this trend for a while now dave.

Haven't put it into the thread in any detail as the persistence of this season to derail promising NH trends is notable.

Siberian/Russian vortex to be the driver by back end jan. Vortex split of sorts over the pole with the Canadian daughter becoming less relevant to our part on the NH due to the more favourable Atlantic profile. Either via a southerly jet with weak n Atlantic blocking or a more defined e greeny ridge.

That's all a long way off and loads of weather to get through before then (some of it wintry )

  • Like 3
Link to post
Share on other sites

 

I'm not having a go but I think it needs pointing out that Temp anomaly charts for the next 7 days  don't really paint an accurate picture of the weather many will experience over the coming days.

 

I think it is more a case of last winter skewing our opinion that westerly patterns do not deliver snow to low levels rather than the anomaly charts to be honest. From what I've seen, they look correct to me. In fact the 8 day mean today shows Scotland in the slightly below normal category whilst the rest of the UK is at or above average.

Polar maritime incursions at this time of year should deliver wintry showers to low levels in the north with snow over Scotland. Last year was very unusual for the strength of the zonality as we saw the 850s pretty much mix out to around 0C across most of Europe whilst meant the rather homogeneous temperatures we got. I feel this has skewed opinion rather than anything else.

 

As for the output, it looks a bit of a mess to be honest. No real confidence, the means do open a window at around day 8/9 but by day 10 have the polar vortex re-grouping over Greenland again. Not sure how significant an Atlantic ridge we could get or if we see a wedge of heights develop to our north at some point which could aid to bring colder conditions to the UK. Not happy about the handling of the potential storm for the 15th and the following events as there are shallow lows being picked up on some models running over the top of the Azores high whilst other models do not spot these at all.

Low resolution GFS op is whack y to say the least. The parallel look to heading the same route as the ECM with low heights diving into Europe with an easterly developing, though rather weak and brief.

Edited by Captain shortwave
  • Like 1
Link to post
Share on other sites

Good morning all.

My thoughts haven't changed for around a week now so the models have been fairly decent in predicting the general synoptic for up to mid month. 

I said back then that somewhere in England would likely experience a decent snowfall in the run up to mid month, even if fairy shortlived and I think the output has firmed up on this cold zonal flow kicking in this weekend.

 

I'm not having a go but I think it needs pointing out that Temp anomaly charts for the next 7 days  don't really paint an accurate picture of the weather many will experience over the coming days.

After a mild spell into Saturday things will turn colder and wilder from the NW. temps may be only a little below normal in the North and around average in the South over this period but it will feel cold in strong or gale force winds at times and although rain is most likely in the South it looks cold enough for snow to low levels at times in the NW. That snow line will move up and down the country as winds veer between W/SW and back W/NW but North Lancashire and Yorkshire as well as Cheshire at times could  see heavy snow showers at times with temporary accumulations possible. West Scotland, NI, and anywhere from midlands Northwards with elevation could well see blizzard like conditions at times. There is scope for prolonged periods of snow again next week in among rain and gales so quite mix.

 

The North/South divide as far as storminess and wintriness is concerned looks as though it may continue for a while after mid month so what people experience in the SE will be especially different from those in the NW which is where some of the disagreements will arise. Someone getting blown around in a blizzard will stagger in and see someone post "typical January fare, temps around average" and likewise someone will get in from a typical wet and windy day and read how the winter has finally turned with cold and snow. IMBY and NIMBY posts are no problem but we should try to remember conditions on the ground will be very different at given times for large swathes of England to save bickering.

 

Mini ramp ahead.

 

The good news for Southerners, as I see it, is that during 3rd week of Jan the scope for snow will move South albeit the synoptic will be quite messy and generally zonal still so any snow unlikely to stick around away from hills.

The Operationals are starting to pick up on some very interesting possibilities during this period IMO. First Southerly tracking lows across the base of a UK trough which if the pattern develops and is far enough South with UK on cold side of trough could give very heavy snowfall for parts England and the South could get a heavy fall from any channel low in such scenario.Again conditions for any snowfall will be marginal but the possibility absolutely exists.

Also they are picking up a new signal which may or may not develop. They have been modelling low pressure pushing SE into the continent for some time on and off but they are beginning to play with the idea of low pressure diving SE or disrupting much further West. If this happens West of the UK then again it could lead to some very heavy snowfall if it is firmed up upon. So look for slider possibilities also in this 3rd week.

ECM 240h chart from this morning handily shows the possibility of both scenarios but it is also in GFS output. It is just another possibility to add to the confusion at the moment but I think this signal is gaining in strength while any sort of strong Atlantic ridge (for this period) weakens - though it will be the weak ridge that aids any slider.

 

ECH1-240.GIF?08-12

 

So while it may be typical January fare at a stretch the second half of January could be very snowy at times and the South will not be excluded from any fun and games.

Looking further into the crystal ball last week of Jan could see a better attempt at blocking and deeper cold pushing in from the NE.

 

Caveats.

We could yet get a much flatter pattern with the Azores high playing spoiler which will give our weather a completely different feel to above but what I describe above is not hope-casting or farfetched. It is currently a reasonable forecast IMO based on current output. The problem is that any snow events look to be marginal and temps never particularly cold so someone may get average and rain while another gets cool and snowy and of course any changes tot eh output could be negative for snow chances rather than positive but If this pattern does develop the MetO are going to have a very difficult but rewarding forecasting period coming up!

If you are anywhere with a little elevation or further North then you will likely see some heavy snowfall on several occasions between now and end of Jan. If you are in the South you could just see wind and rain though your chances will likely increase later in the month.

Barring the AH playing spoiler second half of Jan looks fascinating and a deeper cold spell still looks like possibly forming in last week. Hopefully we will get lets of updates from Fergie on MetO thoughts.

well glad i read this post before attempting a very similar posting myself .since last nights model runs and todays runs i am much more confident in an eventual cold cyclonic outlook later next week .As Mucka mentions its in these sort of set ups that many can see some good snowfalls .Indeed after flicking through my large collection of Royal Met Soc magazines it becomes very clear that some very notable falls of snow can turn up in the sort of synoptic situation Hopefully we can reach later next week .So lets hope ECM Meto and the rest of our gang can all sing off the same Hymn sheet soon ,with regards of course to Snow . :cold:just noticed how much page space i,v created ,apologies ,

Edited by legritter
  • Like 2
Link to post
Share on other sites

I think it is more a case of last winter skewing our opinion that westerly patterns do not deliver snow to low levels rather than the anomaly charts to be honest. From what I've seen, they look correct to me. In fact the 8 day mean today shows Scotland in the slightly below normal category whilst the rest of the UK is at or above average.

Polar maritime incursions at this time of year should deliver wintry showers to low levels in the north with snow over Scotland. Last year was very unusual for the strength of the zonality as we saw the 850s pretty much mix out to around 0C across most of Europe whilst meant the rather homogeneous temperatures we got. I feel this has skewed opinion rather than anything else.

 

As for the output, it looks a bit of a mess to be honest. No real confidence, the means do open a window at around day 8/9 but by day 10 have the polar vortex re-grouping over Greenland again. Not sure how significant an Atlantic ridge we could get or if we see a wedge of heights develop to our north at some point which could aid to bring colder conditions to the UK.

 

 

Hi Matt, I don't doubt they will be fairly accurate and have no problem with them being posted so long as it is not supposed to be indicative of "real feel" over the period.

(Which is why I made a point of saying I wasn't having a go)

It is partially down to North South divide but also that we will see a change into weekend so it will feel quite mild into Saturday but then cool to cold thereafter for the 7 day period. 

I mean if you are in the North you can look at that map and see temps above average yet you could very well see snow falling over the weekend and again early next week after a brief milder blip and at no stage after Saturday will it feel above average.

I just don't see temp anomaly charts over a period of very changeable weather as a particularly useful descriptor without the added info.

 

I agree we are looking at a very difficult forecasting period 3rd week of Jan especially - could be anything and everything on offer.   :unknw:

Edited by Mucka
  • Like 2
Link to post
Share on other sites

Just a quickie as I don't have much time.

 

Looking at the model output I would be staggered if the Met O outlook was correct. The change towards a colder 2nd half of Jan is gathering pace and an even colder last week of Jan looks on the cards. Despite the varying GFS runs they are all pointing towards a colder trend.

 

Very excited at todays output so far.

 

Just add its the trend with regards to the PV that is exciting me and shall explain later.

 

I really can't see why the Met Office's outlook is erroneous?

 

There are hints of Atlantic amplification in FI but the form horse has to a toppler / MLB.  With no other strong support for sustained wintry weather (e.g. MJO), that's a very brave call.

 

PS - Not saying that you will be wrong but with the evidence at hand, not convinced about anything significantly colder in the next 15 days.

 

ECM London temperature ensembles look only slightly below average in the medium term.

 

ensemble-tt6-london.gif

Edited by mulzy
  • Like 4
Link to post
Share on other sites

This has popped up a few times now this week and its showing again this morning with some fairly widespread snow for parts of England and Wales during the 2nd half of next week

 

Before that NW Scotland is shown to get 12 inches maybe slightly more in places by mid next week - separate warnings out for this weekend suggesting blizzards on high ground

 

150-780PUK.GIF?08-6

 

Moving on 24hrs and the highest totals in NW Scotland hit 35cm (13 inches)

 

174-780PUK.GIF?08-6

 

Moving on another 24hrs and snow becomes more widespread for parts of England and Wales - up-to 13cm in places (5 inches in old money)

 

198-780PUK.GIF?08-6

 

Not a great deal of change 24hrs later though the highest totals in NW Scotland are now at 39cm (15 inches)

 

222-780PUK.GIF?08-6

 

The final chart shows totals in NW Scotland now hitting 41cm (16inches) with snow widely covering Scotland and the pennines east of the pennines remains snow free

 

240-780PUK.GIF?08-6

 

giphy.gif

  • Like 7
Link to post
Share on other sites

GFS 06 ensembles Central England

 

graphe3_1000_249_92___.gif

 

Just a hint of things settling down and that some colder weather may be arriving last week of Jan.

Also that is quite a cold zonal signal for 13th to 19th with mean 850's around -4c (suggesting they will dip to -6c or so at times)

  • Like 1
Link to post
Share on other sites
Guest
This topic is now closed to further replies.
×
×
  • Create New...