Eagle Eye

@sebastiaan1973 I suspect it's quite rare but I'm fairly new to these.

GLAAM tendency now significantly +VE. W/all +VE MT, especially east Asian and north American but also tropical momentum rising. Therefore the momentum built-up forcing w/MJO phase 7 is a potential high-lat blocking pre-cursor for mid-Feb but there's still MJO phase uncertainty.

Yes however I suspect that that's the amplitude of both the suppressed (dry) and active (wetter) phases because of the mix in the ensembles. So it depends whether the phase 8 of a combined falling +VE IOD and El Nino is a suppressed or active phase. @AO- thank you, was wondering why today's wasn't showing up for me but anyway, still a similar strength and direction of travel.

Looking at the ECM which probably has a better convective envelope characterisation, has it being active into phase 7 before potentially moving towards COD by phase 8. However, will the convective envelope response to falling IOD into phase 8 be favourable or is that another dry phase response. I couldn't really tell you for now because it's still a dynamical evolution, not a perfect composite response as with pretty much anything. Perhaps things looking a little better on the NWP and the teleconnections.

And then I woke up In all seriousness. The amount of detail on that post is top notch, well done. The amount of high-level posts on here recently have shown how complex the second half of this Winter is. "Set in stone, February is not" as Yoda would say.

Using verification, the GEFS has generally trended -VE of the actual strength of the wave propagation, the GFS slightly above but as we go further towards the future, they move very close together and phase 5-7 are more responding to a quickly falling -VE IOD (a fairly strong wave strength response but it's not the only variable, just 1 of the MJO spread inputs) so potentially may be underdoing the strength of the active western Pacific response further away from the western Maritime region slightly infiltrated w/dry air occluded into the far western Maritime region likely in response to the trend away from a +VE IOD, not a full on dry response but not as +VE wet as the normal composite and that dry air into parts of the Maritime region. Whereas a wetter than normal eastern Maritime and western Pacific that has been characterised poorly by the GFS so far. Theoretically leading to a larger response in phase 7.

@Met4Cast Agree with you w/uncertainty but at least we're not guaranteed to be zonal for the rest of Winter is all I can say. Long-term it is mostly guess work based off the slightly most likely outcome at the moment.

Not all down, trending towards a Greenland high for mid February which I mentioned as a general possibility might be showing now. Not much to add for now.

The second half of February was bigger to me than the first half pretty much with a mid Feb change, quote from Thursday I think; "that could well have a significant response by mid February here. For now, the best we're looking at is the rising GLAAM and phase 5 ish response. However, the +VE IOD collapse has aided the potential for a larger MJO-GLAAM tropical and subtropical forcing for that mid-month ish potential. " I did expect a semi-good signal for early February but that's appearing unlikely. However, mid February perhaps later towards March given how delays have been recently is the next potential. It's a large pattern to get rid of though.

Its both a driver and a response but larger changes in the overall setup in AAM and MJO would change it more than it would affect them. Therefore the second rise in AAM or still a small chance this rising AAM is important. Yes because of the horizontal temperature gradient it can drive zonal mean zonal wind fairly continentally but the EAMT is more of a driver of the Asian pattern than the Iberian high, as in my mind it's a sudden and strong event. Almost akin to a major warming being stronger than an initial westerly zonal wind. Once the support for an Iberian high is lost it won't be able to sustain itself. Hence, if there is a complete flip in the zonal extension over the north Atlantic (the north Atlantic Jet, maybe the NAJ) , then the Iberian high doesn't magically stay. The hard thing is getting that, almost needs to happen in this situation with a disconnected jet phasing between the NPJ and the NAJ and therefore the support for a poleward propagating Rossby wave over north America transferring eastward is likely. This AAM rise may semi-support that but the CAD over eastern USA that's possible may be overriden by the extended jet despite the equatorward NPJ movement. However, to say Winters over because of the Iberian high when there's that second potential AAM rise, isnt necessarily wrong but it's not really right either. Depends on how the MJO and AAM both go beyond the current rise which is mostly not poleward propagating. Yes climate change expansion of the Azores high has made it harder but it's by no means impossible to get rid of it, we do, however, need a stronger zonal mean zonal wind change than we did in years past. Cold spells still happen, they haven't disappeared, it's just harder to get and sustain them.

Not entirely out of question that the +VE heights driving the zonal pattern in the mid-term w/the GLAAM rebound underway the NPJ equatorward shift is extremely likely but also extended and appears strong favouring that Pacific trough, it could be more zonal US response in terms of the jet. With the north-eastward moving US high, cold could well undercut into eastern parts of the USA and get more entrenched than you would first think because if that does happen it is natural to pivot the pattern to flip it and hence the two jets seperate between the NPJ phase and the north Atlantic. However, getting rid of the Euro high entrenched over well Europe might be a bit harder even with the rising Greenland heights as it's just easier to return to zonal without any Scandi movement whatsoever and the CAD won't last forever in the eastern US and so the Greenland pattern would return to - VE heights fairly easily. Its a precarious pattern that needs everything to go right for us and we know our luck quite often. We'd need a Scandi high to come out of nowhere which is unlikely, the NAO pattern is essentially useless in this scenario.

With the rise GLAAM signal being poor for us specifically, the second GLAAM rising signal was delayed on the latest CFS. We're running out of time for February to be honest, especially the firs half. The Euro-Scandi high does look like becoming more of a ridge and we do get stuck with an expanded mild and zonal pattern almost irrespective of the US pattern. The second potential GLAAM rise toward mid Feb will be very important for any prospects for most of us later into Winter.

Its Canada going cold that'd fire the jet up.

Nothing really to add to this for now, I think I've done enough in-depth discussions so far this Winter. US pattern same as late December but longer could mean UK pattern similar.

There's been very little difference run to run, perhaps slight downgrades for some places and slight upgrades in strength for others. As is models not handling topography well nor the strength of highs and lows well either. Ground observations are going to be all we know about this storm once it's left. Relying on UKV is also a bit meh, it's an ok model that has often gone for the right setup with a storm then moved it around for the next few runs only to have been right a day before. It's a puzzling model.

Already the LLS and vorticity coming into play and that's w/out any real low-level energy there either.

Let's talk severe hail potential as well. Low CAPE weakens that potential especially given that means lack of vertical depth of convective availability, weakening the updraft speed. However updraft speed and hail size is an overdone rhetoric when it's updraft width combined w/the energy. Yes updraft speed can contribute but generally I find updraft width + low freezing temps helps. Especially w/non Supercellular hail. Weak LLS and strong DLS can also contribute. Multiple combining cells inducing strong momentum in a buoyant environment is generally the best given non-Supercellular severe hail setup in a C shaped hodo environment type. Taking a look at the setup, this is the closest I could get with a reliable CAM's model as they don't go fully into Ireland so I won't get the convective energy part just the environment. Imagine inflow into the storm to complete the hodo and it's quite C shaped w/fairly low down freezing, the moderate LLS keeps severe hail production fairly unlikely for now it appears though. Especially given fairly normal low-level lapse-rates, so surface warning effects are theoretically quite important here. A favourable for severe weather setup here is the mid level dry cap, a more typically severe hail setup than what I see here. Specifically modelled, here's an example. The shear stretched shower in southern Ireland has a flanking cell potentially contributing to both momentum and eventually updraft width, where the updraft widths potentially being quite wide here supporting a lot of hail embryo production and whilst more hail embryos do not necessarily mean bigger hail, the fairly random processes forming hail inside these clouds are significantly increased to normal here w/the large updraft width though weak updraft speed is still capping it off at sub-severe levels in my opinion. Though TORRO did still mention severe hail potential so we'll have to see.

Update on the tornadic potential. Using the 3CAPE and low-level vorticity lobes, the potential energy for rotation crossover is mostly the best through the middle of Ireland. The 'cheat' for tornadic forecasting is a crossover between 3CAPE and low-level vorticity. I'd probably want 925hPa vorticity but I'm not paying for that so this will have to do. Now comes the problem of very stretched shear so mostly linear mode. General tornadic potential will come from a broken line, whether that precedes potential energy for rotation or it's opposite way around I don't know so I won't really bother trying.

10 years ago today. Yes that's me

Convective Outlook️ (remember this is for Winter, lightning isn't a big risk but convective rainfall and tornadic potential are quite big risks with this) The UK on the south side of a significant low with the stronger gusts should experience significant gusts potentially in excess of 80mph Sunday through Monday morning and further north the risk for severe wind gusts goes through Monday. A couple models are even showing 95+ mph in Northern Scotland and occasionally hitting the Irish coasts. The UKV especially strong on this with 105mph in Northern Scotland and western Ireland. I find this unlikely just given the UKV's tendency to over strengthen the winds but it shows what's possible. Most of the UK not just the coasts could well see 50+ mph wind gusts, yes the land based friction will have some effect but given how strong the low is, we'll still likely see severe level winds throughout the UK and Ireland. It's especially interesting to see the widespread 100 mph 850's on the south side of this low when it's over the UK to show you how strong this low is. Surface friction and the viscous layer is therefore an extremely important dynamic in just how strong this low can be at the surface here. Thunderstorm potential wise and the cyclonic vorticity ejects out PV lobes towards the SE of the lows centre which we normally wouldn't be hit by as its rare for a low to be this well placed for us but Ireland gets the full strength of the PV lobes latching onto WAA which drives line based thunderstorm developed perhaps stretched more horizontally with shear stretched storms. The push of WAA means that there's a Theta-E drive that on the backend of is where the PV lobes generally are found through mostly Ireland and this is where the best thunderstorm potential potentially is but the high saturation weakens that. Apart from that, general lightning risk throughout most of the UK and Ireland with the energy just generally around. Mostly sporadic though. Tornadic risk is mostly with high LLS combining with 100+ J/KG of 3CAPE, mainly in Ireland and despite the crosswise stretched showers andor thunderstorms, the 3CAPE and vorticity crossover with any ejected PV lobes means that for the UK there's a fairly high tornadic parameter. The streamwsie vorticity would come from a broken line segment, so keep an eye out for those. So there's a genuine potential for a tornado within all the straight line winds but would probably need a less saturated area of shower formation to actually work. Also a small chance with some weak line convection Sunday night over parts of the midlands.

Convective Outlook for it as all the wind warnings have already been done really. The UK on the south side of a significant low with the stronger gusts should experience significant gusts potentially in excess of 80mph Sunday through Monday morning and further north the risk for severe wind gusts goes through Monday. A couple models are even showing 95+ mph in Northern Scotland and occasionally hitting the Irish coasts. The UKV especially strong on this with 105mph in Northern Scotland and western Ireland. I find this unlikely just given the UKV's tendency to over strengthen the winds but it shows what's possible. Most of the UK not just the coasts could well see 50+ mph wind gusts, yes the land based friction will have some effect but given how strong the low is, we'll still likely see severe level winds throughout the UK and Ireland. It's especially interesting to see the widespread 100 mph 850's on the south side of this low when it's over the UK to show you how strong this low is. Surface friction and the viscous layer is therefore an extremely important dynamic in just how strong this low can be at the surface here. Thunderstorm potential wise and the cyclonic vorticity ejects out PV lobes towards the SE of the lows centre which we normally wouldn't be hit by as its rare for a low to be this well placed for us but Ireland gets the full strength of the PV lobes latching onto WAA which drives line based thunderstorm developed perhaps stretched more horizontally with shear stretched storms. The push of WAA means that there's a Theta-E drive that on the backend of is where the PV lobes generally are found through mostly Ireland and this is where the best thunderstorm potential potentially is but the high saturation weakens that. Apart from that, general lightning risk throughout most of the UK and Ireland with the energy just generally around. Mostly sporadic though. Tornadic risk is mostly with high LLS combining with 100+ J/KG of 3CAPE, mainly in Ireland and despite the crosswise stretched showers andor thunderstorms, the 3CAPE and vorticity crossover with any ejected PV lobes means that for the UK there's a fairly high tornadic parameter. The streamwsie vorticity would come from a broken line segment, so keep an eye out for those. So there's a genuine potential for a tornado within all the straight line winds but would probably need a less saturated area of shower formation to actually work. Also a small chance with some weak line convection Sunday night over parts of the midlands.

Not no real point, it won't be affecting our own pattern till February so we can look at our pattern but for the Pacific pattern beyond the Japanese low's effects, which will drive our own future till late January, I don't think there's much point in looking at that yet.

Models especially poor with the handling of AAM strength for this specific rise, last few forecasts have corrected the GLAAM rise fairly significantly stronger so I don't think the deterministic runs will have any sort of pattern scheduled properly till after the AAM rise and when it flattens out into a phase 6/weak frictional torque loss around day 6-7 maybe. So not till next week will we have a proper idea in my opinion. Then we've got a potential second rise to contend with.

The Japanese low that forces the switcheover to a stronger Pac trough to stop a full on Alaskan ridge and keep the trough in charge is now only a few days away so the return to a Pacific trough and semi-zonal forcing for early February appears quite plausible. So not much time for a weaker zonal state. So the time frame for the Scandi high is running out as this would eventually cut off the feed for the Euro-Scandi high. Which would also higher the potential for it to advect north but it would have to do it straight away then.

Unlikely pattern to verify but there is some support for a Scandi high in phase 5 only if the momentum forced into the high is strong enough otherwise it's just quite a flat ridge into UK-Scandi slightly tilted like the GFS mean has it as. However this pattern is not entirely without support and we've seen multiple runs showing this is possible. Early February is very much the start of this potential for a return to cold potential after all as I've said before.