Blessed Weather

February 15

Ridiculous for the 15th February!

February 14

7 minutes ago, Metwatch said:

BOM just doesn't work for me, phone or laptop or any browser

Strange. The link works for me on my laptop (using Firefox browser). From your image it looks like the https protocol might be messing it up. Try copying in and pasting the link from Met4Cast into the url address line. It should look like my screen shot and not have 'https' showing on the address.

February 14

26 minutes ago, Metwatch said:

Also any idea where I may find those MJO reanalysis charts which i've seen posted by a fair few recently?

I'm unsure exactly what you're after (I can't recall seeing reanalysis charts posted), but maybe the NOAA MJO archive going back to January 2006 may help? Don't look at the "file last updated" date, but go by the date embedded within the pdf file name.

Files in /products/precip/CWlink/MJO/ARCHIVE/PDF

WWW.CPC.NCEP.NOAA.GOV

February 14

3 hours ago, Met4Cast said:

On the other hand, this will be the third SSW of the winter that has utterly failed to produce. A lot of hope is placed upon SSW's to produce but the truth is roughly 70% of split events produce colder weather across NW europe, that % is significantly lower for displacement events (as you know, I'm sure!)

I wonder if the initial Canadian Warming was a fail tho? It might actually have played a role in giving us the favourable (for cold) NH synoptics in the form of a Greenland High that could well have delivered a notable cold spell. But agree that unfortunately the second SSW that occurred around the 17th January seems to have been the factor that on this occasion messed up the favourable synoptics. Win some, lose some.
Here's an extract from a NOAA blog dated 16th Jan discussing the Canadian event and imminent second event:

The polar vortex is acting up
.....But what makes the stratosphere’s current behavior unexpected and somewhat rare is that the polar vortex seems to be more disrupted at the lower levels, closer to the stratosphere-troposphere boundary. For more than a week, high pressure has been sitting in the troposphere over Greenland. It’s possible that the recent minor stratosphere warming reinforced this Greenland high pressure, which then drove a wedge into the stretched-out polar vortex in the lowest part of the stratosphere, splitting it into two lobes.

Full NOAA blog: https://www.climate.gov/news-features/blogs/polar-vortex/polar-vortex-acting

Whatever, for stratosphere watchers it's been a very interesting winter - three events noteworthy in itself (although strictly speaking we await to see if the third SSW happens or not!).

February 14

9 minutes ago, ANYWEATHER said:

The SSW, won't have any implications for winter ,maybe Spring, but far too much emphasis on this phenomenon for my liking.

You are most entitled to your opinion. Whilst there's no guarantee that a SSW will impact our little island favourably it's widely accepted that the occurrence of one can result in some of the UK's most severe winter weather, hence the interest in their occurrence. If you're looking for cold at least it's a ticket for the draw. This from the Met Office:

"In recent years some extreme cold, winter snow events have all been connected to the surface effects of sudden stratospheric warmings, such as those in 2009-10, 2013, and ‘the beast from the east’ in 2018."
Link: https://www.metoffice.gov.uk/weather/learn-about/weather/types-of-weather/wind/sudden-stratospheric-warming

February 14

A SSW not entirely in the bag yet. The latest GEFS 0z mean forecast (blue line) barely reaching a reversal around the 19th Feb before mean zonal winds recovering:

The members going for a reversal has fallen away from a peak of 87% earlier this week. At this stage not a favourable trend:

The SSW probability in GEFS is: 61%

Source: Weather is Cool: http://weatheriscool.com/

Yesterday's 0z 10hPa minimaps from Zac Lawrence (awaiting this morning's update) showed no members going for a split; so very much looking like a displacement event. This for the 20th Feb:

Source: https://www.stratobserve.com/ens_ell_minis

A displacement event not surprising given it's Wave 1 forcing:

Edit: Lots of info & reading about SSWs to be found in the Netweather Research library :
https://community.netweather.tv/learning/research/stratosphere-sudden-stratospheric-warming-ssw-r54/

February 11

2 hours ago, raz.org.rain said:

it would appear that we're getting a somewhat clearer impression of how an SSW will impact lower latitudes, and it seemingly isn't good news if you want cold in our location. Regional factors such as a strong jet just go against any incursion potential. The safe bet would be to assume that the cold incursions strike the northeastern US instead. I'd imagine we'd get more of the same of what we've already got.

Hi. I'm wondering who this 23 year old person is that you're quoting, but I'm surprised to see anyone confidently predicting what the tropospheric impact will be at this stage from a SSW that won't occur until the 20th Feb, assuming it does indeed happen. If it does happen it's going to be a Wave 1 induced SSW which typically means a lag of at least 10 days for any impact to show.

Here's a few snippets from recent research that indicate the extent of the challenge. Click on the title to go to the full paper.

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events (2020 paper)
While the stratospheric forcing often projects onto the North Atlantic Oscillation (NAO), the tropospheric response to SSW events, if any, is highly variable, and what determines the existence, location, timing, and strength of the downward impact remains an open question.

Using large ensembles to quantify the impact of sudden stratospheric warmings and their precursors on the North Atlantic Oscillation (2023 paper)
We find that there is little information in the precursor state to guide differences in the subsequent NAO behaviour between one SSW and another, reflecting the substantial natural variability between SSW events.

February 10

16 minutes ago, Froze were the Days said:

So were are the effects from this decent split SSW? as posted on Thursday by a couple of members...it's gone all very quiet in here!

Latest GEFS forecasts and 84% are predicting a SSW with the mean showing this occurring around the 20th on the 0z run today:

Source: http://weatheriscool.com/page11.html

February 10

Back to model output discussion please. This is not the thread for discussing what's gone wrong with this winter. A new thread has been created:

Further off-topic posts will be disappearing.

Thanks.

February 9

That's what brovs do Norrance! Well me and mine did anyway.
Hope she's OK with nothing too serious.

February 9

Thought I'd take a peek at Zac Lawrence's excellent GEFS 10hPa minimaps. The 0z run from yesterday (not updated to today's yet) indicate the potential evolution of the sPV over the next couple of weeks. On the 15th Feb (T168) the vortex still largely intact with none of the 21 members or the GFS Op showing reversed zonal winds.

By the 20th Feb (T288) there are 7 members showing a split vortex with the remaining 14 plus GFS Op showing a displaced and highly stretched vortex - both displaced and split (main lobe) pushed to the Asian side of the NH. This date seems to represent the peak of the sPV distress with 16 members showing a reversal in zonal winds to easterly with only 5 members showing no reversal (no technical SSW) and retaining weak westerly zonal winds.

No more than a very slight recovery of the vortex by the 24th Feb (T384) with just 7 members by then showing positive (westerly) zonal winds. The GFS Op remaining negative (easterlies).

Whatever transpires, hopefully a very interesting period of weather watching coming up. Personally I love the unpredictability that a SSW throws into the weather mixing bowl.

Charts from: https://www.stratobserve.com/ens_ell_minis

February 8

3 hours ago, Severe Siberian icy blast said:

This year has been a joke in all honesty. It's all well and good removing posts when they don't read what you want but the reality is as a model output discussion, then airing frustration on hear surely is relevant particularly when it relates directly to the forcing drivers we've all obsessed over in depth then it's completely relevant.

Just a quick comment on this, assuming it's a comment about the moderation of the forum.

It's not a case of "removing posts that don't read what you want". The team fully understand the frustration for many of trying to get some proper wintry weather into the UK and have no problem with folk discussing those frustrations and the causes. But what we, the team, are trying to do is encourage that to happen in the appropriate thread and not in the Model Output Discussion thread. From comments, messages and reported posts we know there are many members that prefer to keep the Model thread 'clean' and to read about the latest output. And there are some members who aren't of a cold persuasion and are quite happy with this winter. We try to strike a balance for the benefit of the majority.

We therefore have the Model Banter and Emotions thread as well as the more general Moans, Ramps & Banter thread in the Winter Discussion area for folk who aren't happy with this winter and wish to sound off.

The Model thread guidelines - the link is at the top of every page - give clear guidance about posting in this thread.

I hope everyone understands.
Thanks.

February 8

10 minutes ago, Met4Cast said:

The MJO runs on a cycle of roughly 60-90 days, it won’t be back into favourable cycles again until April (ish).

AAM tendency likely won’t return in any meaningful way until late March (assuming a coherent MJO cycle).

So in a word.. no.

Whilst certain phases of the MJO are known to assist with 'bringing on' a SSW (and the MJO has recently been in phases 6 and 7 which do), there is also research suggesting that - acting in the reverse direction - the SSW then impacts the MJO. So maybe it's 'all bets off' with regard a continuance of the normally expected MJO and AAM cycles? Extracts from a 2020 paper:

Influence of stratospheric sudden warming on the tropical intraseasonal convection

.....analysis reveals that SSWs also exert considerable influence on tropical intraseasonal convection. The occurrences of MJO phases 6 and 7 significantly increase during around 20 d after the onset of SSWs...

Full paper: https://iopscience.iop.org/article/10.1088/1748-9326/ab98b5

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5033893

February 8

10 minutes ago, Met4Cast said:

The MJO runs on a cycle of roughly 60-90 days, it won’t be back into favourable cycles again until April (ish).

AAM tendency likely won’t return in any meaningful way until late March (assuming a coherent MJO cycle).

So in a word.. no.

Whilst certain phases of the MJO are known to assist with 'bringing on' a SSW (and the MJO has recently been in phases 6 and 7 which do), there is also research suggesting that - acting in the reverse direction - the SSW then impacts the MJO. So maybe it's 'all bets off' with regard a continuance of the normally expected MJO and AAM cycles? Extracts from a 2020 paper:

Influence of stratospheric sudden warming on the tropical intraseasonal convection

.....analysis reveals that SSWs also exert considerable influence on tropical intraseasonal convection. The occurrences of MJO phases 6 and 7 significantly increase during around 20 d after the onset of SSWs...

Full paper: https://iopscience.iop.org/article/10.1088/1748-9326/ab98b5

February 6

Developing squall line moving down across the Region this evening. Arome suggesting it will reach London around midnight. The cold front marking the boundary between the very mild airmass we've been in for some days and the much colder air moving south. Here in Hadleigh today's high of 13C will be replaced by a max of around 7C tomorrow. That'll feel different.

Radar 16.40 Arome midnight

February 4

1 minute ago, January1940 said:

Goodbye to my old profile (Weather-History), hello to my new one. What a pain this e-mail authentication has proven to been.

Sorry to hear that WH. Why don't you raise in the announcement thread (below) that Paul started. Maybe Paul can help you and you can retain your old name and profile?

February 4

January 2024

A look at the monthly anomaly charts would suggest a rather uneventful month, but a few noteable weather events did give the month some interest.

On the 2nd January Storm Henk brought a Met Office weather warning for the Region and widely saw gusts of 60 mph (96 kmh) and a top gust of 94 mph (151 kmh) at the Needles lighthouse, Isle of Wight.

A cold snap around the 7th - 9th January saw some snow showers come into the Region on a brisk NE'ly, giving a light covering for some east coast locations and higher ground in Kent and Sussex. Another cold snap on the 18th/19th January saw a widespread very sharp frost overnight into the 19th. Min temps across the Region:

Another named storm - Isha - on the 21st and overnight into the 22nd January again saw gusts widely across the Region of around 60 mph (96 kmh) and a top gust of 112 kmh (70 mph) at Odiham, North Hampshire.

Zooming in on the stats for East Anglia reveals:

Near-average temperatures (+0.2°C)
Near-average rainfall (98%)
4th sunniest January on record (143%)

Interestingly, January 2024 continues a run of sunny Januarys with 2022, 2023 and 2024 all featuring in the top 4 sunniest Januaries (records back to 1910).

With thanks to Dan Holley, Weatherquest, for the summary chart and EA stats. See X @danholley_
Min temp & storm gust charts from Starling Roost Weather.

February 4

blizzard81
Here's the latest 5-day 500hPa forecast verification chart from the ECMWF website for the period 5th Jan to 25th Jan. It shows a very respectable and steady performance from GEM (CMC). The worst performing model appears to be the NCEP/GFS with the forecast accuracy graph line lurching from a good performance one day to a poor performance the next. JMA performance similar. Interesting that over the 20 day period even the UKMO comes bottom on occasions. Also interesting that all models had a bad day at the office on the 24th Jan - I wonder what caused that?
But the main take is that ECM is top model.

Source: https://charts.ecmwf.int/products/plwww_w_other_ts_upperair?area=NHem Extratropics&day=5&score=Anomaly correlation

Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5029588

February 4

blizzard81
Here's the latest 5-day 500hPa forecast verification chart from the ECMWF website for the period 5th Jan to 25th Jan. It shows a very respectable and steady performance from GEM (CMC). The worst performing model appears to be the NCEP/GFS with the forecast accuracy graph line lurching from a good performance one day to a poor performance the next. JMA performance similar. Interesting that over the 20 day period even the UKMO comes bottom on occasions. Also interesting that all models had a bad day at the office on the 24th Jan - I wonder what caused that?
But the main take is that ECM is top model.

Source: https://charts.ecmwf.int/products/plwww_w_other_ts_upperair?area=NHem Extratropics&day=5&score=Anomaly correlation

February 1

8 minutes ago, TEITS said:

Very pleased with the overall output this morning. The trend is becoming clear i.e heights increasing to our N, Heights decreasing to our S with the infamous Iberian high being replaced by low pressure as the jetstream takes a much more S,ly route. At the same time low pressure over the UK slowly moving E introducing a cold, unstable potentially snowy spell of weather.

With the usual caveats about using 'past climatology' anomaly composites, the MJO Phase 7 and 8 February/Nino composites certainly support that evolution TEITS. MJO charts rotated for comparison with GFS 500 anom on 15th Feb:

Ph 7

Ph 8 ................late Feb??

January 29

I don't know whether this helps the 'foehn' discussion:

Weather record for warmest January set in Scottish Highlands

A new UK record high temperature has been set in the Scottish Highlands, according to provisional figures from the Met Office. It recorded a peak of 19.6C (67.3F) at Kinlochewe on Sunday, making it hotter than Rome and the Cote d'Azur.

BBC Scotland forecaster and meteorologist Calum MacColl said the balmy weather was due in part to something known as the Foehn effect. He explained: "The Foehn effect is where, within a stable atmospheric environment, air is forced to rise up and over the hills and mountains, before descending back towards the surface on the leeward or downwind side of the mountains.

Full article: https://www.bbc.co.uk/news/uk-scotland-highlands-islands-68119951

January 28

Please don't respond to off-topic posts such as "winter's over" and "can't be bothered anymore". Those posts have been moved to the Model Banter & Emotions thread where they belong. Thanks.

January 27

13 minutes ago, Penguin16 said:

How common has that become over the years? Seems like snow shortages in alps are happening almost yearly at some point? Is there a rapid change from only 10 20 years ago?

I'm afraid it really isn't good news. Take a look at this research article published in March 2021. Extracts:

Observed snow depth trends in the European Alps: 1971 to 2019

Here, we present an Alpine-wide analysis of snow depth from six Alpine countries – Austria, France, Germany, Italy, Slovenia, and Switzerland – including altogether more than 2000 stations of which more than 800 were used for the trend assessment. The average trend among all stations for seasonal (November to May) mean snow depth was −8.4 % per decade, for seasonal maximum snow depth −5.6 % per decade, and for seasonal snow cover duration −5.6 % per decade.

Full paper: https://tc.copernicus.org/articles/15/1343/2021/

January 27

@Metwatch What a dreadful sight for January! Looks awful. I had a quick look at onthesnow and they're reporting snowpack levels across the Pyrenees are currently only 33% of normal, and only slightly better in the Haute-Pyrenees where levels are 43% of normal. For their sake and indeed the Alps too I hope the GFS 06z is on the money with the arrival of a cold airmass and snow around the 8th Feb.

onthesnow link: https://www.onthesnow.co.uk/pyrenees/skireport

January 27

29 minutes ago, sebastiaan1973 said:

Indeed, 2018 was an extreme event, a combination with SSW and very strong MJO.

The 2018 SSW makes a good case study with the MJO playing a 'trigger' role. Extracts:

Mechanisms and predictability of sudden stratospheric warming in winter 2018
We investigate the role of the tropospheric forcing in the occurrence of the SSW, its predictability and teleconnection with the Madden–Julian oscillation (MJO) by analysing the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecast. The SSW was preceded by significant synoptic wave activity over the Pacific and Atlantic basins, which led to the upward propagation of wave packets and resulted in the amplification of a stratospheric wavenumber 2 planetary wave.
......a composite analysis suggests that teleconnections associated with the record-breaking MJO phase 6 observed in late January 2018 likely played a role in triggering this SSW event.

Full paper: https://wcd.copernicus.org/articles/1/657/2020/

Latest MJO, nicely into Phase 6 atm at reasonable amplitude. ECM and GFS ensembles: