VillagePlank
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All to still play for. Firstly, it's not uncommon for low pressure to correct to a more northerly trajectory than the models show. Secondly, the jet stream is acting as a kind of block on the northerly trajectory. This is persistently moving further east allowing the low to travel further north, as shown in the last few model runs. Timing is key, here. Will the JS move east quick enough to allow the LP to move further North?
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Latest Sat IR, If you notice on the West/South West side of the centre, it looks like it is developing into fingers (banded cloud head) which is indicative and characteristic of sting jet formation. Not quite clear enough to call, yet - but worth keeping an eye on!
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Regarding the issuance of MetO red warnings. This is controlled by the National Severe Weather Warning Service (NSWWS) where it's priority is a "warning service based on the impact of the UK weather rather than a threshold of the weather itself" https://www.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/data/pwms_nswws.pdf
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Quick update from Arome1 12z, Don't forget that like most wind related charts - these are at 10m. So, if you're up on top of the North or South Downs, you can add to these values. Also, max wind velocity is often calculated as the maximum moving average value over a period of time (I'm not sure with Arome, but presumably it's similar to others) so the realised max wind velocity spot values are likely to be higher.
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The worst of it for the SE seems to be around 6am, according to GFS 0.25, 12z. I'm not sure about the track of the LP, I think it will veer further North. In particular with it's interaction with the other LP, NW of Ireland. The strongest part of the jet-stream aloft is well east of UK by this time. Of more concern is saturated ground with trees with most of the leaves still on - could be lots of disruption come morning rush-hour, in particularly for the overcrowded SE notwithstanding some excessive rainfall totals.
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This suggests mid-afternoon onwards for the far SE, *should* the requisite environmental factors develop favorably. Worth noting that most of the models did not agree, but as the morning comes to a close, there is some agreement amongst some of the models - the yellow warning from the MetO, mid-morning, for example. On the threshold, really, of severe/non-severe given TT of 50, but still likely thunderstorms based on this skew-t Don't forget the handy risk of/severity of storms table (59=fluffy clouds, 96=armageddon)
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Hmmm, Not so sure about here in Rochester, now. The stuff in N France is heading off to the NE, and it looks like it will miss the UK entirely. The cloud base is *still* high, here, implying that convection never really got going (since we were expected low LCL and low LFC, today) probably supressed by outflow and deritus from last night. Might get lucky, but it looks as if it's just going to be rain here.
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Unusual skew-t for a day with t/storms forecast. Of interest is the LCL (lifting condensation level) which is the height where the air becomes saturated and the LFC (level of free convection) which is the height where air becomes warmer than the surrounding area so that the air just goes up and up - for our interest goes up far enough to create big clouds that support storms. Both are surprisingly low, which suggests very little surface heating will be required to kick stuff off - maybe as low as 20degC, but more like 21/22degC. These temperatures should be the level where any CIN that is forecast evaporates quickly. The great big fat DD (dewpoint depression, the dent in the blue line as it goes up) normally really gives lift a good boost, too. Given that the skies above Rochester are currently clearing, this bodes well for later on. Don't forget to check out your chances with the marginally useful, t/storm chart,
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Whilst I am sitting here, storm-less, I thought I'd create a rule of thumb chart. Just a bit of fun, really. Here's what you do. Grab yourself a skew-t chart, Read off the Total Totals, and the K-Index, and then use this chart to get a number, from 59 (almost no chance of a thunderstorm but if you do see one it won't amount to much) to 96 (you're going to get a thunderstorm, and when you do, you'll soil your underwear) This combines likelyhood of seeing a storm with intensity of the storm. Useful maybe? Who knows ....
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Storms and Convective discussion - June 2023
VillagePlank replied to Supacell's topic in Storms & Severe Weather
In that ascent chart, the dewpoint depression, I think, is significant. ie if enough surface heating (and other factors) can get a parcel to get that high then the extra 'push' will turn it into a storm. -
Storms and Convective discussion - June 2023
VillagePlank replied to Supacell's topic in Storms & Severe Weather
Tomorrow in the SE a parcel is forecast to be able to travel all the way up. The skew-t is such that it looks like we are losing all our air to space. The problem is, that this occurs approx 00z to 01z, so of course, no air lost to space, and no thunderstorms. The conditions are available over the next 72 hours, it's just that the timing is awful. -
Storms and Convective discussion - June 2023
VillagePlank replied to Supacell's topic in Storms & Severe Weather
Sad times