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ancientsolar

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    Storms and Convective discussion - June 2023

    in Storms & Severe Weather

    Posted

    2 minutes ago, ResonantChannelThunder said:

    Yep, me too. Keeping a close eye on the channel south of Sussex for any developments, as for the Arome to be correct, something's going to have to happen there over the next hour or so.

    sat 24 5min radar showing quite a significant development , so perhaps there'll be more cells developing westwards, which would encourage that setup on the Arome --- 

    • Like 2

    Storms and Convective discussion - June 2023

    in Storms & Severe Weather

    Posted · Edited by ancientsolar
    add info

    radar showing a developing  approaching Peterborough 

    also looks like quite an area of convection developing South of London.
    - and less so North of London

    Developing shower between Liverpool and Manchester 

    After a lot of cloud, there seems to be a break forming in the South, stretching west toward Southampton - Could allow for developments such as that in South London currently

    • Like 1

    Storms and Convective discussion - June 2023

    in Storms & Severe Weather

    Posted

    4 hours ago, Eagle Eye said:

    Cloud should be partly burned through by mid-afternoon. I suspect later initiation than expected today but shouldn't impact strength too much, any holes in the cloud will allow for very quick advection but this evenings scenario was the bail out for the high for me, 2 chances on the southern portion of the high risk was good enough to extend it down there and pretty much all models showed the northern part of the high risk having something with fairly good burn back of the clouds.

    Just like what you said earlier, even with all this cloud, the sun is somehow finding a way to break through, - the humidity is also very intense. 

    • Like 1

    Storms and Convective discussion - June 2023

    in Storms & Severe Weather

    Posted

    Just now, FBR said:

    This wasn't in the plan today lol

    take a look at sat 24 ,  - you can see on the 5 minute update, you can see small dots of thicker cloud masses coming out of the band of rain on the Northern edge - and the development to the East of the rain too

    image?type=visual5&region=gb

    6554b6be8c0d829a8bf63ae0c82cf121_link.pn Weather United Kingdom and Ireland, Satellite Weather United Kingdom and Ireland, Weather Forecast, Rainfall, Clouds, Sun in United Kingdom and Ireland - SAT24.com

    EN.SAT24.COM
    Weather United Kingdom and Ireland, Satellite Weather United Kingdom and Ireland, Weather Forecast, Rainfall, Clouds, Sun in United Kingdom and Ireland - SAT24.com

     

    • Like 1
    • Thanks 1

    Storms and Convective discussion - June 2023

    in Storms & Severe Weather

    Posted

    13 minutes ago, Eagle Eye said:

    Good morning, me and Jay's first ever high risk, its a historic day ha ha.

    Sunday 10:00 - Monday 08:00

    Widespread MUCAPE 1000+ J/KG with locally 2500+J/KG of MUCAPE means that fairly significant thunderstorms eith frequent lightning are likely fairly widespread when the capping is broken. Similar to yesterday, the capping means that vigorous convection can take place and there's likely to be enough forcing and energy overlapping to create clusters of storms in areas.

     

    Multiple shortwaves and a forming surface low provide the lift for very strong Theta-E and energy as it is pulled up from our south. Very warm temperatures mean that the capping in place is likely to be broken from surface heating early to mid afternoon and provide ample bouyancy for active thunderstorms fairly widespread, especially in the Oxfordshire across to the Llanidloes region where we have issued a tentative high risk as only one model doesn't show widespread thunderstorms in that area. That is the UKV but it's already behind the showers in the channel whereas the two models handling those showers very well, the AROME and the WRF show strong thunderstorms in that corridor.

     

    Given the amount of energy, strong thunderstorms are possible pretty much anywhere but with varying levels of confidence. The moderate and high risk are most likely to see these active storms with most models showing ample energy there to provide vigorous convection.

     

    Given such high moisture and PWAT values and the surface-latching nature of these storms (quite low LCL's), two severe's have been added for possible surface flooding from these possible storms. 1 to 1.5 inches of rain could fall within an hour in some areas which could lead to surface flooding in the strongest storms.

     

    The close to surface LCL's and EL's ≈ 12km lead to significant entrainment CAPE. The low amount of shearing may mean that if these storms cannot last long enough, they won't reach that height but given the significant bouyancy and CAPE, the convection is likely to be vigorous enough to quickly use up that energy. If forcing and bouyancy work together they can counteract thst shearing further by lifting the storms above 12KM, so we may see even taller storms somewhere. Generally the more entrainment CAPE and the taller the storm, the more frequent the lightning. So with these tall storms with significant entrainment CAPE, frequent lightning is probable somewhere.

     

    Along with 200+ J/KG of 3CAPE (0-3 KM averaged out CAPE) meaning that significant thunderstorms are looking likely especially in the moderate and high risk areas. Just for reference 50+ J/KG is typically for strong thunderstorms (surface based ones) and we had around 150+ J/KG yesterday in spots. 

     

    So, more active and stronger thunderstorms than yesterday are possible. It's possible that they could form low-end severe hail though the steep 0°C line means the hail growth zone is quite small compared to usual. Between roughly 7km up to cloud height means that storms have to reach their maximum theoretical height and take in a lot more of their 0> CAPE to grow that type of low-end severe hail. Along with that hail growth detriment, the shear is generally non-supportive and a weak or near non-existant inflow strength doesn't support severe hail. Generally you want the inflow and the shearing to form a C shape with weak low-level shear and strong deep-layer shear. There's moderate low-level shear and weak deep-layer shear. So despite the strong 3CAPE which can sometimes support severe hail almost by itself, severe hail is unlikely and the severe is just for surface flooding.

     

    These storms are likely to be slightly more saturated than yesterday, weakening the lightning potential but given the pure amount of energy in the atmosphere, that shouldn't do too much. It may make the day slightly weaker than forecasted by models such as the AROME but only very slightly.

     

    The surface lift is strong and similar to yesterday so late initiation won't mean too much to eventual strength just like it did yesterday. All late initiation would do is strengthen the vigorousness of convection that gets going and weaken how widespread the convection gets.

     

    Some models then show as the showers in the channel around the central south hit the south coast they should start building up especially as they get further inland and move towards Gloucestershire and Wales hence two rounds of thunderstorms are possible for the southern area of the high. Some models show that as the main convection in that area with it forming a strong storm but other models dont show it forming into much. We've seen it in similar events before where there is significant surface energy after dark which forms thunderstorms from weakening channel showers. Currently this looks to take place west of Southampton, maybe in Southampton if there's a slight eastern shift and across to Dorechester moving NE towards Cardiff overnight, definitely something to keep an eye on radar on if you're between those areas and want a good late evening/early night time (11pm) roughly, storm but its not a guarantee.

     

    So significant thunderstorms with frequent lightning are possible. Strong surface flooding and near-severe hail may be possible as well. Generally, a high end event appears plausible today especially in Gloucestershire and the Wales-England border general area.

    20230611_093242.thumb.jpg.1b312f10af5783dd4dd5afe19a6a7819.jpg

    Well this puts me on the Wester border of your severe Risk, but given the cloud cover, perhaps that's based on this evenings possible scenario - 

    • Like 1

    Storms and Convective discussion - June 2023

    in Storms & Severe Weather

    Posted

    It has been a cloudy morning in SE Wales - but the cloud seems to be breaking up in places

    I'm frequently checking Sat24 for any thickening cloud areas , - if anything the opposite is happening in general, giving the sun a chance to break through and bake some favourable conditions for later on .. much like what is happening in Central-Western France.

     

    • Like 1

    Model Output Discussion - 15th March onwards

    in Forecast Model Discussion

    Posted

    5 minutes ago, Mike Poole said:

    Very little to choose between the ECM clusters T120-T168, all look excellent a week from now:

    IMG_6972.thumb.png.0747a9318f4438957180137f6136d0de.png

    Only one cluster in the next timeframe, so I’ll just show the mean, non too shabby at T240:

    IMG_6971.thumb.png.6c68a0ba8b405a1f39df4bf9d416a4dc.png

    I just wanted to remark on the SSTs.  The seas to the west and south of the UK are much warmer than usual now, as shown by the anomaly:

    IMG_6969.thumb.png.932abe695184b2b62d48435708be0499.png

    It is of interest to compare this with 2 months ago:

    IMG_6970.thumb.png.9481107668e90fcaa967dd2665fd2321.png

    That’s similar to how we came out of winter, a tad above average in most places.  Where’s all this heat come from?  Particularly in Iberia, they’ve had the southern arm of the jet bringing dross there recently.  I think it must be that really unseasonal warmth down there in early-mid spring that has made the difference.  I think the SST anomaly will now be important for summer, potential for more potent storms, but also it is part of a positive feedback loop, which could set in train big heat for the continent from now on.  And for the UK, I always think the continental influence on our weather is made that bit greater in summer by warmer seas in this area to our south and west.

     

    Not only for summer, but also as we enter Autumn , - I'm curious, what sort of Sea temps are there when the Hurricanes form around the U.S and Caribbean, we normally end up with weakening storms crossing the atlantic? Would this sea in anyway feed them? 

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