Blessed Weather

This morning's 0z Arpege continues to show this with Lincolnshire and Norfolk likely to see the strongest gusts as the storm exits the East Coast around 07.00 Thurs morning. Not a bad performance from Arpege on the track and timing of the storm, with it's forecast holding steady for several days now, although this morning's update suggesting the area receiving the strongest winds of up to 130 km/h (80 mph) has narrowed. Widespread gusts up to 90 km/h (55 mph) for areas south of the storm track. Arpege 0z forecast last Monday 15th:

Ventrice not impressed with ECMWF performance on this occasion....

My goodness! Brazil really goes in for amazing clouds!! Imagine standing there watching that coming towards you!

Further news on the cold to our East. Siberia described as worse than "brutal" cold.....

Just the job!!

What an incredible cloud!! Very dramatic!

Yesterday I posted in the Stratosphere Thread an encouraging tweet from Amy Butler about the possibility of a Sudden Stratospheric Warming (SSW) by end-January. My post included Wave 1 and 2 activity forecasts for the next 14 days showing ongoing disturbances to the Stratospheric Polar Vortex (SPV) that are holding back the SPV from growing stronger (with the implication of a stronger Jet Stream and more mobile westerly pattern for the UK). In an ideal situation the Wave activity would lead to a full blown SSW with the SPV zonal winds reversing and cold polar air spilling into the mid latitudes (with weak Jet Stream and high latitude blocking). (My full post: https://www.netweather.tv/forum/topic/88772-stratosphere-temperature-watch-201718/?do=findComment&comment=3714053) I would like to gain a much better understanding of what causes Waves 1 and 2 so that I am able to look at, for example, NWP forecast synoptic patterns or specific teleconnection forecasts (AAM, GWO, MJO etc.) and be able to understand the possible implications for the SPV. From my basic learning of AAM, GWO, MJO and ENSO teleconnections I am already realising that this is an enormously complicated subject with teleconnections interacting with the other (or cancelling each other out) and that different teleconnection phases have different implications. And I'm concluding that it seems incorrect to try and look at what's happening in the stratosphere without understanding what's happening with other teleconnections. I am picking up from the posts of others that there are currently a few 'issues' holding back the ideal position we would like to be in to have a chance of a SSW and possibility of meaningful cold in the UK. A key issue seems to be an El Nina base state (easterlies in the tropics) that is holding back AAM and which ideally needs to be countered? But at least on this point the MJO is moving eastwards and will help? I note the interesting discussions between @Singularity and @Snowy Hibbo about AAM needing to rise sufficiently in GWO Phase 3/4 to help push a SSW. So (once again) I would be grateful for (a) recommended reading material to further my understanding, and (b) maybe a high level overview of where we currently are (AAM, GWO, MJO etc) and what we ideally want to happen over the next few weeks. Finally, any comments please on this statement from Dr. Judah Cohen in his latest weekly blog, yesterday 15/01/18. Is the pattern change he talks of driving a Wave 2 attack on the SPV? " Eurasia has been dominated by ridging/positive geopotential height anomalies and mostly relatively mild temperatures. However, over the next two weeks ridging is predicted to centered in Western Asia/Eastern Europe allowing for troughing on both edges of the continent and colder temperatures in Western Europe and especially Siberia and East Asia. Ural ridging/blocking with downstream troughing in East Asia and/or near the Aleutians is once again favorable for active energy transfer from the troposphere to the stratosphere and should rea-activate stratosphere-troposphere coupling. The strongest pulse into the stratosphere of the season is predicted for this week. The pulse is predicted to weaken the current strong stratospheric polar vortex (PV), erasing cold stratospheric PCHs and returning a positive stratospheric AO to neutral." Link to blog: http://www.aer.com/science-research/climate-weather/arctic-oscillation Thanks in anticipation.

Many thanks for the response SH. Could you re-do the link please - doesn't seem to work. Thks.

Better late than never - some spells of sunshine and some lovely skies finally arrived! That's better!!

A great post Catacol. Thank you. I've been digging around to find papers that will help my understanding of 'frictionals' and their impact on weather/climate and wondered whether you have any links to some you could share? Also, links to the best websites for obtaining the latest charts? I copied extracts of a couple of papers so folk visiting this thread can quickly see if the contents are relevant/of interest to them. In the first paper https://www.sciencedirect.com/science/article/pii/S1674984716300301 I thought Section 1 contained a reasonably easy-to-understand description of the 3 variants: The atmospheric torques can be dividing generally into mountain torque, friction torque, and gravity wave drag torque. Mountain torque is a function of pressure and orography, which exerted the solid Earth through a difference in pressure across any raised Earth surface. The most significant mountain torque is locating in the mountains or mountain massifs regions. For example, if the pressure over the west slope of the mountain is stronger than that over the east side, it acts to push the Earth to rotate faster and slows the atmosphere rotation down, which imparting angular momentum from the atmosphere to the solid Earth. The friction torque is the wind or oceanic current frictional force on the solid Earth surface, which will directly speed or slow down the rotation of solid Earth. If there is a net global eastward surface wind, the atmosphere wind friction force will speed the solid Earth's rotation up, transfer the atmospheric angular momentum to the solid Earth, and thus the atmosphere loses angular momentum. The gravity wave drag torque is part of the mountain and friction torque that is too small to be resolved by present Global Circulation Models (GCMs), due to the nature of coarse resolution of climate models will not resolve the regional/local mountains and mountain-induced waves, and their contribution to the mountain torque. I thought this second paper http://www.csr.utexas.edu/eos/reports/95anual/page5.html further helped my understanding by giving some 'real' examples: Angular momentum has been shown to be essentially in balance among the components of the Earth system, namely the mantle, the oceans, the atmosphere, and the core. .......... Understanding the causes for the changes in the angular momentum of the various components requires a knowledge of the mechanisms that effect its transfer across the component boundaries. ......During one weekly portion of the SEARCH'92 campaign, we were able to isolate the mechanism responsible for a rapid acceleration of the atmosphere: the passage of a high pressure center from the western to the eastern side of the South American Andes in July/August 1992. ...... During the northern hemisphere winter of 1994, another intensive campaign captured a similar event of atmospheric angular momentum transfer by mountain torques, although this time acting across the Rocky Mountains of North America. QUESTION - When the atmosphere loses angular momentum can this equate to a less powerful jet-stream circulating and higher incidence of blocking? QUESTION - Different topic, but in your post you covered the MJO currently moving through the Indian Ocean. I see there's a powerful Tropical Storm Berguitta currently moving across the Indian Ocean. Will this enhance the MJO impact (i.e. amplitude) or is it merely a consequence of the MJO? Thanks in advance.

Windy and wet morning with 1.5mm of rain and a max gust of 44mph at 09.35. When I watched the beeb breakfast forecast for today I was hoping for some sunny spells by the pm, but from what I can see there's still plenty of cloud and rain yet to come through. Oh well, better luck for sunshine tomorrow! 12.40 Current track of the Thurs storm has Norfolk in the firing line with this morning's Arpege forecast suggesting 140 km/h gusts (87 mph). It'll be interesting to keep an eye on this feature as I suspect still some variation likely in the exact track. Gusts Thurs 07.00

Not somewhere you normally think of to go skiing, but certainly looking great this week: While I'm on the forum, may I wish @johnholmes a wonderful week in Wengen. Setting off tomorrow I believe John? I hope the forecast of copious snow this coming week doesn't detract from you having a great time! Wengen mid-mountain forecast at 1,672m http://www.snow-forecast.com/resorts/Wengen/6day/mid

If only a Beasterly would develop! A pool of bitterly cold air over Siberia at the moment! Great photo!!

Encouraging tweet from Amy Butler, holding out some remaining hope of a possible SSW by end January. GEFS with 5 out of 21 members showing a reversal of Zonal Wind at 10hPa 60N. Although it should be noted that the overnight 0z GEFS (15/01/18) run also has 8 out of 21 members showing the SPV Zonal Winds stronger than the ERA interim long term average for 30th January. Continuing the good news, the GEFS show an almost constant disturbance to the SPV from Wave 1 activity during January. Charts for 16th, 18th and 29th Jan: Some Wave 2 activity but to my eye not quite the strength we would wish for. Charts for 16th, 24th and 29th: But at least the overall effect is to keep up the disturbances on the SPV so that by end January it is under duress and stretched. Charts for 15th (48 m/s), 19th (27 m/s) and 30th (34 m/s): Later today I hope to get the time to copy this post over to the excellent new Learning Thread started by @Bring Back1962-63 where I would like to continue discussions and ask questions about the above. Of course input on this thread from our Strat experts very welcome!

Latest thoughts from Matt Taylor about the track of next Thursday's runner:

Wow! Up to 500% of normal precipitation possible for the Western Alps next week!!

Fantastic cloud.... but it does look spookily like the alien spaceship in that Hollywood movie!!

Stunning photo Paul!!

Wow indeed. Although the people on the beach seem oblivious!!

Impressive temperature gradient as a vigorous cold front moved south through Kansas and Oklahoma yesterday (first tweet). It certainly looked very dramatic from the ground as it passed through (second tweet).

Latest blog from John Hammond: "With such a strong jet stream on our doorstep, there is always the chance that it will spin up an area of more prolonged rain, sleet or snow as we head towards midweek. The computer models will struggle with this potential until much nearer the time. And the track of such systems will determine who gets what. It’s the high ground of northwest Britain – where the wintry squalls will be quite incessant – that I am most concerned about. Feet of snow could fall on the mountains, with much larger drifts, thanks to the strong winds. However I also expect some large conurbations of Scotland, Northern Ireland and northwestern parts of England and Wales to be affected by some disruptive snow showers at times. The wintry weather (and a flurry of hype) will make the headlines." https://weathertrending.com/2018/01/12/on-the-horizon-brace/

Whoopee!! After an eternity of dull, drizzly weather the cloud is finally breaking over East Anglia and there's some sunshine about!

John - here's a training video of how to get out of your snow-bound hotel next week!!!

Interesting comparison between this year's SPV behaviour at 10hPa 60N and previous years with a similar pattern that resulted in a SSW. I note that 4 out of the 5 similar years were also e-QBO. Hopefully we can add 2017/18 to this analysis, making it 4 out of 6 years with a SSW!