Nick F

Derecho I've lost faith in using the MJO passage through the phases as precursor to changes in weather patterns towards cold or mild. Following 'warm phases' of 3-4 in early Jan we saw a 2-week cold spell, we've seen the MJO recently pass through 6 and now loitering and weakening through 7, but very little amplification in the upper flow at mid-to-high latitudes to show for it in the models. What high lat blocking that has been showing and will likely continue to be shown down to changes in the strat, i.e. downwelling of weakening winds. And I don't get this obsession with using AAM as tool on its own, it seems that when ever it rises all falls we are told to look out for changes but it seems, like when the MJO moves through the historically 'colder' and 'milder' phases, many other drivers are at play, some not so obvious, drowning it out much influence from it over the N Atlantic sector / Europe. Though the biggest interference in what we would expect in lag to certain MJO phases being climate change. The state of the stratosphere is one driver, when it couples with the troposphere, still one to keep an eye on though. Be glad not hear about the MJO for several months, until the next cold season. I've given up talking about how it may influence patterns, as it makes me feel fraudulent!

Analysis of the risk of locally significant snowfall of higher ground of north Wales, N England and Scotland during Thursday and Friday. Also the risk of heavy rain and flooding in the south. View the full blog here

damianslaw It's certainly been a painful and frustrating winter chasing cold and wintry weather, been plenty promise, some opportunity in Jan with the two week cold spell with easterlies and northerlies, but very little reward for many. A lot of bad luck too.

Froze were the Days Think there is something in the idea that sub-tropical high pressure belts have shifted further north in winter recently, preventing cold getting as far south as it used to and explains drought persisting through the winter months now in southern Europe, as far north as the Alps. The pub run trying to make up for its horror show with a BFTE tease at the end.

Don The persistent high latitude blocking signal from EC46 over recent days still makes me optimistic of a cold end / last third to February. But my worry is the blocking could be too far north for southern UK to benefit, but northern areas could become cold at times. Every time cold patterns develops that seem to be too far north.

Good grief, the pub run couldn't draw any worse charts for coldies this evening. Are we going to have to hope the likely SSW will reverse our bad luck this winter? Of course it may not be a quick trop response to it too. Or will the MJO / AAM help us out? A real struggle to keep up the enthusiasm for any cold and wintry weather coming down south before Feb's out at the moment!

nick sussex Agree, quite a complex low pressure system moving in from the Atlantic later this week. 00z GFS perhaps looking the least likely to handle well the various low centres that develop and disappear within the low pressure system. Differences between EC and GFS on baroclinic development around the southern side of the parent low moving in from the southwest across the Bay of Biscay. A strong jet streak moving E and NE underneath the parent low, EC shows wave developing over the Bay of Biscay which forms a low that moves NE across SE England early Friday. GFS doesn't have this low, but this low is quite pivotal in elongating the low pressure system and pulling the parent low east away with it and not allowing it to drift north over Ireland like GFS and Arpege do.

TillyS You do like to bang the mild drum! Backing the mildest model run every time, regardless of where it sits in the ensembles. It won't always work. The 00z EPS average supports high pressure to build after the coming weekend, not a return to Atlantic and mild southwesterlies that the op shows. Looking dry and not particularly conducive for snow though. We may have to look beyond mid-month for better prospects, the extended ensembles have favoured the high migrating to Iceland and then Greenland with time.

I guess if UKMO/UKV is the most southerly scenario and we discount the GFS then Midlands north look the best bet Thurs/Fri for snow on the northern edge of the rain moving in from the W/SW. Here's UKV: A lot of uncertainty after this week, but it does look like low pressure will clear east on to the near continent to allow high pressure to build in the vicinity of the UK, a cold high. Would disregard the 00z GFS, which looks like it's on the mild end of the spread because it brings in the Atlantic.

IDO The EC op doesn't look like an outlier to me on wetterzentrale spread for Birmingham, would treat those meteociel EPS spread graphs with caution, think they are too crude.

EPS mslp mean has the late week / early Saturday low running through the Channel! Trend GIF over last 4 runs shows the slowing of the low moving NE/E and also further south track. Ending up in France?

A blog looking at how the current mild weather lasts into the first half of next week but then gets replaced by colder air later in the week, with an increasing risk of snow in places. View the full blog here

Stunning sunset out my office window near Heathrow Airport earlier

Today provisionally saw the warmest January temperature on record in the UK, with 19.6C in Kinlochewe in the NW Highlands. It's been rather mild this past week, but will we see colder weather return in February? View the full blog here

Synoptic analysis looking at the arrival of Sahara dust and very mild air from the south over the weekend and into the start of next week. Maybe an idea not to wash your car for now! But could be some nice sunsets or sunrises. View the full blog here

Grid values for UKV at 3am, can see why they issued a red wind warning

A synoptic analysis looking at the development and impacts of Storm Isha arriving Sunday night and expected to bring widespread gales with potential for disruption. View the full blog here

None of the extended clusters showing Atlantic troughing / upper flow energy undercutting high pressure building north over Europe that would hold a Scandi high in place for a sustained enough period to bring cold air our way though, so the high would eventually collapse. My worry is the lack of low heights especially over Iberia from Atlantic troughing undercutting, as well as further east over the Mediterranean Basin from undercutting of cold air from the NE, will mean we end up with a large Scandi-Euro High of little benefit to coldies in the UK other than some surface cold perhaps. But, we know these clusters can change, so more runs needed. But I'd feel much happier if we saw troughing extending from the Atlantic over Iberia rather than the semi-permanent Azores ridging there. Extremely dry across parts of southern and eastern Spain this winter so far, due to lack troughing extending from the Atlantic over Iberia with ridging dominating. We can get away with cold air undercutting high pressure over Scandinavia from the NE into southern Europe to lower heights over the central Med to bring a brief cold easterly, but prefer of the Atlantic troughing undercuts too to make it more sustained. Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5018826

I don't spend all day everyday doing it, weather forecasting is part-time work for Netweather, though also tweet a fair bit, wish I had more time to post on here but work life and home life gets in the way. I have a main job besides doing the Netweather articles. And it ain't weather forecasting I'm afraid. Back to the models, as John H mentions, the UK isn't consistently bathed in Tm air for the next 10 days - alternating rPm and Tm air, but when we are in Tm, it could be very mild, like this Tuesday coming - with 14-15C on the cards, but Wednesday in rPm air and cooler

True, the lack of cold from antecedent mild southwesterlies pumping deep into NE Europe and NW Russia is a worry, though with the right synoptic pattern developing, it can return there from the arctic fairly quickly before the rest of northern Europe can tap into it, but without the notably low temperatures we have seen build since November over Scandinavia, will any quickly developing cold pool be too marginal by the time it reaches here? All conjecture for now, as we have to get a Scandi high to develop and get and easterly flow far enough west in the first place. Getting all the right pieces of the jigsaw to fall into place, not least getting cold air back to the NE and E Europe, a Scandi high to extend far enough west and crucially low heights over southern Europe to stop a high to the NE collapsing south, is an uphill battle to break out of the strong +NAO pattern ensuing.

No signs of any deep cold from the 00z EPS yet ... long road back to cold and snow for now. Need patience of a saint in the UK if you've not seen lying snow yet this winter. Because it can get to you if you spend too much time over analysing and discussing the models each day, why I try to find other things to take my mind away from the disappointment of not seeing snow from this cold spell and seeing little on the horizon. Otherwise you just get frustrated.

None of the extended clusters showing Atlantic troughing / upper flow energy undercutting high pressure building north over Europe that would hold a Scandi high in place for a sustained enough period to bring cold air our way though, so the high would eventually collapse. My worry is the lack of low heights especially over Iberia from Atlantic troughing undercutting, as well as further east over the Mediterranean Basin from undercutting of cold air from the NE, will mean we end up with a large Scandi-Euro High of little benefit to coldies in the UK other than some surface cold perhaps. But, we know these clusters can change, so more runs needed. But I'd feel much happier if we saw troughing extending from the Atlantic over Iberia rather than the semi-permanent Azores ridging there. Extremely dry across parts of southern and eastern Spain this winter so far, due to lack troughing extending from the Atlantic over Iberia with ridging dominating. We can get away with cold air undercutting high pressure over Scandinavia from the NE into southern Europe to lower heights over the central Med to bring a brief cold easterly, but prefer of the Atlantic troughing undercuts too to make it more sustained.

A Sudden Stratospheric Warming (SSW) took place on Wednesday, with a reversal of zonal winds at 10 hPa 60N, but it was a brief reversal and zonal winds look to return in the polar stratosphere, marking its recovery. So its likely this SSW won't trigger high latitude blocking and bring prolonged cold and wintry weather. View the full blog here

There is a chance, as GEM shows, that the Atlantic upper troughing / surface lows disrupt more and slide SE against the cold airmass over the UK weekend of 20/21st. UKMO looks like it could head down that route too after t+168. Not a great deal of support from GEFS postage stamps. But still time for changes towards Atlantic trough disruption. But the return of westerlies weekend of 20/21 looks more favoured for now. Snow event looking likely for parts of Scotland and perhaps N England on Tuesday, as that low that forms south of Iceland in the arctic flow tracks SE towards northern Britain. Also snow showers for far north and coasts exposed to the N or NW Flow. EC has snow event back on the menu for S England Weds/Thurs next week, GFS a near miss, UKMO and GEM well south over France. Could be more back and forth on this front, though suspect it will end up south of S England. Cold all next week, but away from the north, can't see a great deal to get excited about if you want snow, unless the low off the Atlantic tracks further north than suggested. I see the 'but features can pop up at short notice' comments, but nothing to suggest anything popping up other than the Channel low threat for now.

No point squabbling over how dry it will be, too far away to pin down where troughs, convergence zones or lows will track next week that may bring snow I think the key to the longevity of next weeks cold spell will be how long the TPVs over Canada and N/NE Europe are kept apart by ridging mid-N Atlantic and Greenland. GFS/GEM ops are more bullish to merge to 2 TPVs over the Atlantic later next week, turning the flow more zonal / milder / unsettled. While EC det keeps the two upper vortices apart. However, as already posted, the mean of both GEFS and EPS do join the two together by day 10, with the more zonal look taking over. But the smoothed out mean may not be the best guidance at handling upstream developments and how the upper flow and surface lows over the Atlantic interacts with the cold air entrenched over northern Europe Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006538