Eagle Eye

Convective Outlook️ A couple different linear modes appear likely to push through the south and eastern parts of the country but some models do push convection into the midlands and the north as well though. Most convection appears to be likely in the southern parts of the country. An initial system should move through the country in the morning moving NE. Hitting the SW between about 4-8am then moving NE fairly slowly till it hits east Anglia and maybe the SE around 11am maybe delayed till mid day. This could also extend further north into the midlands and the north depending on the size of the PV lobe. Fairly good initial 3CAPE and low-level shearing may favour some tornadic potential but there's still a lot of differences in modelling. Whilst not particularly strong lapse-rates and weak MLCAPE, there may be favourable kinematics for longer lived storm cells and parcels parallel to the flow for 7km cloud heights. The strong buoyant airflow in the SE around mid day near the surface with negative lifted index between the surface and 850s staying strong for most of the SE. Lightning should mostly stay sporadic but for the time of year it's quite a strong system. Given potential cell clustering and momentum exchanges, near severe hail and tornadic potential with turbulent surface flow are possible. The cell clustering is because the next system follows close behind or is part of the main system and clusters up in the eastern part of the country. Eventually showers should start scattering in the afternoon and clearing later on, most of the potential is held in the south and the east mid day, then in the morning further west and there's more mixed signals. Alongside that, wind gusts are likely to be strong because this all happens with a low moving through for the south mainly. Potentially severe wind gusts for coasts and slightly inland. There is potential for a squall line to form if vorticity is strong enough, if that does happen than severe wind gusts inland are also very possible. There's a lot of mixed signals on whether there's merging of systems or whether they disconnect or don't disconnect so it's hard to tell whether a squall line will form. In western Scotland there's a rash of heavy showers likely along rolls of vorticity. Potentially a more favourable area for lightning than the southern mode because of more widespread 50+ J/KG of 3CAPE but less likely to have severe threats associated.

Great example of a cycling mini-squall line today. These occur with interactions between the cold pool strength and low-level shear strength. 1) Tight squall line with weaker trailing stratiform behind it, loses shape as the stratiform region is stronger. 2) Development of cell into the system temporarily outbalances the cold pool and the frontal lobe of the mini-squall tightens. Except for where it disconnects further north with less momentum and shearing effects. 3) Once the new cell cycles into the system, the cold pool re-strengthens and timilts the updrafts back for most of the frontal lobe of convection leading to a loss in the uniform linear mode. Squall line loses shape. 4) As this loses energy, the stratiform region becomes the dominant force and it loses all shape. This is where the mini-squall is unlikely to reform properly till it re-encounters energy.

Convective Outlook️ Behind a clearing cold front, some heavy showers and storms could form around western Ireland and into Scotland where they may become more of a rash of showers. Some sporadic lightning is possible within these showers especially around western Scotland. This is due to a trough just to the north of Scotland and one west of Ireland. Moist air is pulled up through Scotland, leading to a fairly strong amount of moisture convergence in western Scotland. A fairly buoyant airflow for the time of year is wrapped up and carried north by the trough and some of it hangs low into western Scotland with the moisture convergence. This also coincides with very strong lapse-rates in similar areas and moderate saturation. Relatively high deep-layer shear also favours good situations for longer lived single-cell storms and a higher risk of lightning due to that and the moderate saturation. All of the buoyant and moist airflow leads to 100+ J/KG of 3CAPE and 200-300 J/KG of MLCAPE so most convective potential is kept rather low in the atmosphere but the favourable buoyancy and shearing may act as kinematic forcings to push the storms beyond the 5.5-6km maximum mostly predicted. This depends on how much time the cells can live though and whether it will be more of a cycling mode especially with how messy some forecasts predict the showers to be organised. The high shear and high 3CAPE may be favourable for a Supercell somewhere especially if it were later in the year but I don't think it'll be enough. Something to keep an eye out for and if one were to form then there's enough support for some slightly below severe hail. Similarly there's enough low-level shear and 3CAPE that if enough streamwise flow can be reached along the high potentially available vortcitiy fields mainly in western Scotland then a tornado couldn't be ruled out. The western Ireland and surrounding area of western Scotland risk is more due to the general conditions surrounding the western Scotland risk than anything, in Ireland and isolated showers are a risk and the rash of showers may live long enough to push further east into Scotland whilst maintaining some lightning potential. If the rash of showers does upscale as a proper PV lobe forms then the low-level energy and low-level sheer may allow for some relatively strong wind gusts as well. Nothing severe appears likely but an upscaling would increase the potential for that risk.

Lovely day for some convection. P1310655 copy.mp4 P1320001 copy.mp4 P1320567 copy.mp4

Thunderspotter Don't think they'll be anything of note tonight to be honest. Happy birthday for a few days ago.

Convective Outlook️ Behind a cold front clearing east, there's some fairly strong buoyancy for the time of year that could form, allowing for some convective forcing in pockets mainly isolated to the SE but perhaps in some areas further north. Good lapse-rates and 100+ J/KG of 3CAPE possible could well allow for sparodic lightning in showers forming behind the front in the SE. However, this would most likely rely on a storm taking full advantage of its surroundings by taking advantage of all the convective energy possible and so the deep-layet shear being low really limits the risk to sparodic lightning and mostly showery activity in the SE. With the highly saturated layer just above the LCL and low LCL, it's not looking like showers would be highly photographable either. Though, the weakening saturation post 850's do still favour lightning slightly so it's dependant on how much DLS can truly form, some models such as the ICON-D2 up to around 30 knots between 0-4 miles and that may be more favourable for lightning but given time of year and weak MLCAPE, still sparodic at best. DCAPE, not bad low-layer shear and low LCL's might be enough for some fairly gusty conditions below any showers that do form as well but not enough to be severe worthy. Similarly, a low freezing height and some energy may be favourable for small hail but non-severe most likely. There may be a funnel or two from the low LCL's but apart from that no real support that I can see for a t ornado.

It's nearly that time of year (I mean 2-3 months is nearly right?) for the storms to come back properly. Hoping for a good year of course. YouCut_20240217_165417480.mp4

Another of the research into storms. This time some lightning data.

Another helpful part of the website for working out where best will be to get clear view of storms and what to expect from them from Cameron Nixon. Would be helpful to bookmark it for storm days. Parameters – Cameron J. Nixon CAMERONJNIXON.WORDPRESS.COM This is a comprehensive "cheat sheet" of severe convective weather parameters. Definitions of parameters can be found here. Composite parameters and...

Chesil View To be fair to Tamara she's not infallible, even the professionals did seem to think the cold could well occur. It's just been one of those Winters hasnt it.

Despite the Greenland high regime not being favourable for we did get one and we did get a win for the teleconnections. This was from my post back on January 12th. "So we get another seperate jet situation w/favourably kinematics for the high just south of the Caribbean to be forced up again eventually as the momentum forces itself from jet to poleward forcing and so a mid-Atlantic block and/or a Greenland high is very possible" "The CFS weekly is showing the southern disconnected jet and the slow southern descent of - VE zonal wind anomalies into the 2nd week of February ish, hence the Greenland high support increases. " Yes I used the CFS but only to get the timing right and it worked. It's a shame it wasn't helpful for us but predicting if it'll be helpful is a whole other ball park because then that relies on predicting the strength of it, working out support for a Euro high etc. The momentum to poleward forcing wasn't really enough to gain a strong Greenland high, it was just more of a weakened Greenland vortex area. However, if you think you can dismiss teleconnections then you're wrong, in fact, whilst it wasn't what we wanted it did become slightly favourable for us as we got some snow for the north. If you're expecting teleconnections to get it within 100s of miles months away you're wrong. With that said, we continue to run out of time on the chase for Winter, the MJO is going back into it's shell as it re enters a surpressed phase w/the drier air distributed by the changing IOD pattern into the phase 8 area. Along w/that AAM is doing what it's supposed to but it's just not being forced poleward, so we're stuck w/out much momentum and so we're relying on transient events which could well happen and have been shown on the models but they can easily be thrown out of kilter.

Well this Winter certainly happened, if you can call it that.

WeatherArc A Reed Timmer classic to me, the ones that start off just shooting vertically and then showing the strong shear show the potential for tornado's "in the air" for that storm chase.

Renegade Supercells early season in Texas, classic setup of sorts. Could be very interesting to say the least.

Paper from one of Reed's tornado measurements has been written up. Will be an interesting read. https://amt.copernicus.org/articles/17/943/2024/

12Z GFS has helped set the trend towards a split semi in stone, much better than all the displements runs earlier. Hopefully the trend continues and better. Still quite far out.

Singularity Problem with the major SSW is that if it does happen, most of the runs appear to be wave-1 displacement driven with most of the vortex over Europe so favourable surface responses at the moment are looking a bit meh. So I'm not really thinking those March's are likely at the moment but we'll see. I really would warn people here getting excited over the modelled SSW, no matter the strength it's really not looking the best, arguably the worst scenario considering some runs saying about - 15ms zonal mean zonal winds. Most of the deterministic runs have been displacement type for a while. I'm still hanging onto hope but this feels like it's not going to end up well.

Secondary AAM rebound appears to be well underway, momentum being added to the atmosphere, significant jet shift surely likely for the NPJ, perhaps displacing the Pacific trough as has been expected for a while. This appears to be helpful in Greenland high forcing still. Interested to see how accurate the response forecasts tend to be in this scenario. Original post: https://community.netweather.tv/topic/99814-model-output-discussion-22nd-jan-2024-onwards/?do=findComment&comment=5031468

Secondary AAM rebound appears to be well underway, momentum being added to the atmosphere, significant jet shift surely likely for the NPJ, perhaps displacing the Pacific trough as has been expected for a while. This appears to be helpful in Greenland high forcing still. Interested to see how accurate the response forecasts tend to be in this scenario.

Let's talk SSW potential. What we don't want is the GFS 06Z to be repeated, it's an example of a wave becoming baratropic-ally stable before a wave-2 can occur and that leads to when the EHF disconnects (which is the switch from a baroclinic wave to a baratropic one) it's a wave-1 diffusion into the polar vortex. What that'll do is disconnect and stretch it but clearly Eurasia-ward. It's then both easier for the vortex to recover and become baratropic (vortex like) even when displaced right over Europe. Easily leading to a state where we're relying on a strong Greenland high surface response for any luck here as the SSW would be another negative for us and even that that's not looking good on the 06Z. This appears to be a trend with the GFS and has been the outcome of many recent SSW's over the last few years so I'm sort of inclined to believe it, the timeframe for a wave-2 being fairly short. It's another multiple rounds of wave-1 due to timing on the 06Z GFS, could well end up in a major SSW but later and still displaced based most likely. As once the EHF pushes polewards, it won't recover on the wave it just disconnected on. Timing as ever is important and it's currently an uphill struggle. Just a warning. Hopefully the 12Z is better. Away from the Strat, GLAAM on the rise soon/potentially now if it can maintain and w/the already +VE GLAAM and MJO 7-8 phase during a late Winter El Nino and enhanced Western Pacific-western Hemisphere (slightly) convective envelope then we have good support background signals wise. Greenland high easily supported at the moment later into February, how much that is helpful will depend on basing and actual strength of response. Good tropospheric signs but we're running out of time for them to produce.

johncam Yeah, Greenland is the easiest to get cold from unless you get certain angles of Scandi high really but I don't think Winter is over yet, still got the possible SSW and about a month left.

johncam Greenland isn't the only high available that's good for us.

johncam Greenland high quite possibly there which is also supported long term by the GFS unless I haven't got the updated EC46.

AAM tendency definitely down over next few days but the actual total momentum ignoring the tendency is still +VE easily compared to recent and long term averages, any +VE EAMT event soon would lead to probably the largest AAM response of the Winter.

Mike Poole Yes very interesting to say the least. Good thing is that it's - VE NAM drive so should reflect back a Greenland high so could reinforce an MJO-GLAAM driving Greenland high if that were to occur. Looks to be driven around this time.