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Greeny

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    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted · Edited by Greeny

    33 minutes ago, Andy Bown said:

    Not a squall line, a convergence zone stretching all the way from East Anglia to Cornwall, very impressive.

    I missed it cause it isn't at such an acute angle as we saw a couple of weeks back. I guess as the winds are stronger at the surface they don't have to be colliding head on as such. More to add to what I've learn't.

    PWAT values are forecast as 27mm so yeah could drop a fair amount.

    Screenshot_2016-07-11-14-46-07.png

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted · Edited by Greeny

    I'm surprised convective weather hasn't issued a convective outlook for tomorrow unless I'm missing something, perhaps the area is too small, ok things are not overly impressive and lapse rates not that steep but some CAPE showing although modest over eastern Scotland (early afternoon) and East England a little later. Occluded fronts moving in according to metO SLP chart including a trough. GFS shows increased upper level vorticity spreading from southwest to EA and out over the north sea and beyond. DLS weak so pulse storms at best if any. Unlikely any CZs and looks to be a little windy the more east you are and losing intensity throughout the course of the day according to GFS any way. Low cloud bases forecast, LLS reasonably strong. Certainly nothing widespread and certainly not a great deal forecast for tomorrow but worth a mention I guess :)

    A feeling of uncertainty and noone else on board mentioning it does give me a sense of reluctancy but its the convective forecast topic so what the hell.

    vorticity 15z.pngSBCAPE 15Z.png

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted · Edited by Greeny

    3 hours ago, William Grimsley said:

    @Ben Sainsbury, that's not a funnel cloud either, as @Flash bang flash bang etc says, it's just some scud cloud.

    The day I saw my first funnel from Peterborough a few years ago, on the way back I caught some what looked to be spiralling air through some residual cloud fairly low down. I've only ever seen that once and there wasnt any Cbs around at that time and it was pretty sunny too. The atmosphere seemed to be ripe for that so who knows, can't really confirm unless its caught on video really.

    Back to today, appreciate we're under a ridge today with no convective outlooks but just pointing out that mid west builds up some CAPE throughout the day with an upper trough arriving early evening. Mid level capping will probably inhibit any CAPE that is present.

    Midlands coverage and some more EA. MLCAPE slowing moving off to the east throughout the evening and night.

    • Like 1

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted · Edited by Greeny

    12 minutes ago, East_England_Stormchaser91 said:

    Long live the 28th June. Not this year I'm afraid though!! 

    Nothing promising on the horizon either.. 

    You never know something may crop up as we head into July. Keep an eye on Friday, showing some signs of a convective day more the north Scotland and Ireland but its 3 days out and it could change. The low may end up being further south when it arrives you never know.

    Edit: the jetstream a direct hit currently being forecast producing strong DLS.

    • Like 1

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted

    1 hour ago, weather09 said:

    Yes, last Thursday had plenty of moisture but relatively low instability, which meant torrential downpours but with lightning amounts not having been that high. Had the skies been clearer and temperature a good few degrees higher, no doubt CAPE would have responded and we would've seen an increased likelihood of severe storms.  Agree the amount of moisture in the atmosphere that day would have had a negative effect of updraft strength given the lack of heating and build-up of CAPE, but point is in an environment of moderate/high CAPE, you could have PWAT values of 4-5cm but that wouldn't be considered an inhibitive factor for storm development. Would just tell us that there's a lot of moisture in the atmosphere. 

    Agreed with Nick F when he mentioned that the more southwesterly sourced component to the low-level flow at the time perhaps the reason why it was too cloudy/murky, where a more southerly/southeasterly flow off the continent would have seen more in the way of clear skies. 

    Yeah it went off over the continent and thats the flow we really needed. Was severe imo but for excessive rainfall, it did cause quite a bit of difficulty. Certainly a member in my fb group said a friend or relative had flooding issues. I drove passed a car that had broken down and the next day delivered a car to a customer who had his car break down cause of the floods. More heating and CAPE would have had a different output, I should think HP would have still been likely but storm stuctures would have been a lot more impressive and hail a good size I reckon too.

    Sorry I didn't respond earlier William I wasn't able to keep an eye on the thread. Was interested in the shear, deep and low layer shear would have like to have seen a bit more CAPE build up and a higher troposphere. In general was the event interesting and did it have some noteable events? Its harder to judge when I don't live there to see it.

    • Like 1

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted · Edited by Greeny
    added DLS

    1 hour ago, weather09 said:

    Useful link on precipitable water and its relevance to storms: http://www.theweatherprediction.com/habyhints/294/

    Think some are looking too deeply into this.  CAPE and updraft speed determines lightning amounts/frequency.  PWAT simply tells you how moist the profile is. Moisture is key to good storm development, however high moisture can lead to the issue of 'water loading', where high volume of water and intense rainfalls can slow updraft speed which can have a noticeable effect in weaker CAPE environments, where in the the initial stages of storm development you'll get some lightning, but then intense falls of rain quickly stifles the updraft. But in environments of high CAPE, this isn't an issue, but does mean that CAPE alone won't tell the whole story concerning potential updraft strength.  In the real world, many factors influence updrafts.  

    Yeah thats a good website w09. Thanks for posting the link for PWAT its good info.

    I think a good example of high PWAT keeping lightning to less than expected was here in Norfolk last thursday the 23rd. Although it was hot in the cloud breaks and was humid, DPs of around 20C, cloud cover kept the build up of CAPE to less than what was expected if clouds were not so in abundance.  Before it hit V4 radar realtime overlay stated 600j/kg of CAPE. The outcome were floods and some lightning with the odd loud cracks of thunder but lightning wasn't as frequent as it could have been if either CAPE was allowed to build up more or PWAT values were a bit less.

     

    Edit: this was within the period where there was strong DLS in the mix.

    • Like 1

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted

    10 hours ago, Mapantz said:

    Whenever there's a big set up, I usually get nothing. It's the surprise situations that something occurs here, when not much is on offer. lol

    I think the latest run from GFS has downgraded only slightly with the strongest shear more focused for the southwest than the previous forecast but lightning wizard and its SRH seems to have upgraded a little with its 12z and 15z, falling considerably by 18z.

    • Like 1

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted

    2 minutes ago, Ben Sainsbury said:

    If you didn't see my post from earlier this is exactly what I was saying, decent CAPE, 300 SRH, 60kts of DLS, I'm just not sure!

    Yes I did see it thats what prompted me to take a look. Its interesting for me to see what happens with this forecast and it being a small area, its a learning curve. The deep layer shear is coupled with nearly 30knts of low layer shear. Would be well interested with this setup myself. Can understand the tornado risk. I looked at the surface winds and they were quite strong which prompted me to check the LLS. As always I would be cautious to get too excited but would be looking around with interest :)

    • Like 2

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted · Edited by Greeny

    1 hour ago, William Grimsley said:

    I think your reply is a bit screwed up. PWAT values itself don't effect lightning amounts, but higher PWAT values can leave you saying "Why isn't this cell electrifying?!"

    It does look rather interesting for your neck of the woods William. Seems also to be potential for Ireland and later on in the day for Scotland. Equilibrium level for the southwest isn't as high (20 - 25000ft) but skew-t for Newton Poppleford has around 600j/kg of CAPE build up by 1800 with the current run. Lightning wizard has significant tornado parameters and up to 300 SRH although county of Devon skew-T has 191SRH at 12z down to 40 at 18z but that is still enough I think. It is a small area however and SRH may drop before storms finally get going so not sure how it would transpire if anything does fire there. Lightning wizard insists SRH for right movers will still be 200-300SRH at 18z. We shall have to see. Worth looking to any low cloud bases that you may be able to see for rotation and good luck!

    Equilibrium 12z.pngEquilibrium 18z.pngSRH RM 18Z.png

    • Like 2

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted

    3 hours ago, William Grimsley said:

    Ooo, yes! Come on!

    Cant seem to find the post from Supercell to quote but yeah I just noticed that whilst having a little look ahead on GFS Not a vast area currently but will see what happens in the upcoming runs. Noticed a post saying that it would be it for convective weather for a while but that isn't necessarily the case. The more far forward you look the more likely things change and the next thing you know there is another potential convective day. Can say that through experience although at times there can be a long period of quietness, best to take it a couple of days at a time.

    • Like 1

    Convective Storm/Discussion thread - 11/06/16 onwards

    in Storms & Severe Weather

    Posted

    9 hours ago, Allseasons-si said:

    I have the car to service tomorrow(myself)so hopefully get  it done before things kick off

    i see where Nick f is coming from with the convergence zones,i have drawn a couple of red lines illustrating this(hope you don't mind Nick),,if i have got this wrong then correct me but i did look carefully at this,looks good for this neck of the woods

    nmmukwind.png

     

     

    Its the convective discussion thread, I'm sure Nick won't mind one bit :) Its worth taking into consideration earlier times. 12Z and 15Z is a good time to look at imo, initiation is more likely to be around those times. Plus if on pulse storm like days where shear is weak if you're trying to see a funnel like Im trying then its more likely to produce one as its intensifying when the updrafts are strongest and are not being choked off by downdrafts.

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