Storms and Convective discussion - 1st August 2022 onwards

[SarahWxm]

10 minutes ago, TallPaul said:

That's total dedication to your team Sarah... but to witness a win AND a storm within 48 hours is as rare as finding a hen's missing tooth...

Joking of course... and enjoy your well deserved Prosecco...

 

 

I guess I’m being too greedy expecting 3 points and a few cracks of thunder lol. I’ll take just the 3 points tomorrow night tbh  Definitely enjoying the Prosecco atm though!  

[ChezWeather]

42 minutes ago, SarahWxm said:

I agree and I travelled between Yeovil, Bristol, Gloucester, Kidderminster, Bridgnorth, Telford and Wrexham today and still seen Jack s**t. Me is not a happy bunny lol. Tomorrow I’m going to Manchester and Chesterfield and probably still not see anything

I hope you come to Chesterfield and see a storm, and not leave with 3 points  

[SarahWxm]

2 minutes ago, ChezWeather said:

I hope you come to Chesterfield and see a storm, and not leave with 3 points  

Haha if we play like on Saturday I’ll be leaving Chesterfield with 0 points and 0 thunder/lightning, then I definitely will be one naggy cow lol

[TomLO04]

Webcam live from Terracina, Italy is popping off

Don’t get these kind of storms very often in our neck of the woods

 

Edited August 16, 2022 by TomLO04

[Thundery wintry showers]

Staying at my parents in Knaresborough for a couple of nights, and a cell went up just to the north-east of here between 10 and 11pm and produced quite a bit of thunder and lightning.  It was so localised and short lived that the Met Office's ATD system didn't detect the lightning from it, but it shows up well on the radar.  Thus, I've had my first thunder-day of the 2022 summer quarter (I had a couple in Lincoln back in May).

[Wivenswold]

I must admit to being very lucky this year, seeing 6 storms at home (including Monday's one) and 2 while in London.  This is unusual for me and very unusual for this corner of Essex as homegrown storms often collapse when they get a cold feed of air off the North Sea. It's worth noting that the sea near me has been 2-3oC warmer than usual this year so I wonder if that may have been the difference. And a little luck of course.  

[TallPaul]

40 minutes ago, SarahWxm said:

I guess I’m being too greedy expecting 3 points and a few cracks of thunder lol. I’ll take just the 3 points tomorrow night tbh  Definitely enjoying the Prosecco atm though!  

3 points and your fave tipple are a must... your storm will arrive tomorrow (he says with fingers crossed)

[Woodboss]

5 hours ago, BrickFielder said:

Usual warnings on this information that I simplify things and don't exactly follow the rules so this will be a flavour of things rather than some of the very good technical explanations on the internet from professional meteorologists (My interpretation should be taken with a pinch of salt). Maybe somebody will do a proper pinned post of this but in the meantime check Nick's very good pinned guide to thunderstorms in the UK which covers many of the ideas which about SkewTs.

SkewT Diagrams are usually seen with respect to soundings. Here a weather balloon is released to rise through the atmosphere and the temperature, dewpoint, wind speed and wind direction are recorded at different levels as the balloon rises and then plotted on the SkewT diagram. From this information you get a snapshot of the air conditions and this is useful for predicting weather conditions downwind. For example the Nottingham soundings are sometimes useful for weather prediction later in the Netherlands or Germany. The only upstream sounding for the UK is Castor Bay in Ireland which tends to be useful for Scotland and Norway. UK weather models rely heavily on Satellite monitoring which give a good idea of the air conditions upwind but has some limitations. What I tend to have a quick look at is the forecast (predicted) SkewTs and because they are not based on real measured conditions I often take certain liberties just to get a rough feel of conditions. 
 The types of things I can see from the diagrams is how humid air (dewpoint too close to temperature at any height may mean messy convection), is convection possible, is there cooler air aloft making things more unstable, is there wind shear which could enhance storms or make them long lived, is there CIN or a CAP stopping convection and how low cloud bases are and how high cloud tops are. Looking at a forecast SkewT I have numbered some features and lines and will try to explain what they are and how I interpret things (shortcuts included) 

1. Winds going up through the atmosphere giving direction and strength (number of barbs). The more winds turn with height and more speed difference there is between the surface and upper levels (Wind shear) the more severe a storm might be.
2. Isotherm lines (blue) and saturation mixing ratio lines (yellow dotted) are used to calculate the lcl and ccl(cloud base). Everywhere along an isotherm has the same temperature.
3. Saturated adiabatics (green dashed lines) (dry adiabatics are the red lines but I don't really use them but should). As moist air rises it condenses out into cloud and becomes cooler. If the air is still warmer than the surrounding air after the cooling it will continue to rise. So this line is the rate at which air cools as it goes up and produces cloud.
4. The actual or forecast temperature of air at a particular height above the ground. If the temperature drops rapidly (lapse rate) between the surface and high up at the tropopause due to cooler air aloft and drops quicker than the saturated adiabatic rate then air will rise and produce cloud (convection) up to a point where warmer air is encountered. There other mechanisms for example fronts that produce cloud so it is not the complete story.
5. Dewpoint temperature which is a measure of humidity of the air. If the dewpoint and temperature are very close together then humidity is likely close to 100% and cloud will form at that level which might affect temperatures at the surface and lapse rates. Humidity at the surface will tend to dictate cloud base levels and whether any moisture is available to form clouds.
6. This is a line I add myself to guess at the cloud base level. It should be parallel to the saturation mixing ratio but I tend to use the isotherm line. To do this properly you should draw a line from the surface temperature parallel to the dry adiabatic (red lines) and draw a line from the surface dew point parallel to the saturated adiabatic (yellow dashed lines). This is the place where a surface parcel of air will begin condense out into cloud provided the meeting point of the two lines is above the temperature line.(This is where I take a bit of a rough shortcut)
7. This a line also added by myself which estimates the level of free convection (cloud top height). This should be a curved line from the intersection point determined by 6 (cloud base level) following the saturated adiabatic until it intersects with the temperature line. The larger the area between this line and the temperature line the more unstable the atmosphere is.
8. Things like elevated convection (The lines I have drawn don't work) and other scenarios may show up here. The higher the cape number the more unstable and stronger storms will happen. Li represents the lapse rate and the higher it is the stronger storms will be. CIN is a rating of prevention of convection and the higher the number the less likely storms will occur. Pressure 1000mb tells you convection should be from the surface and not elevated.

Strictly speaking the forecast SkewT shown may not lead to a storm due to the CIN level, but considering it is estimated from satellite images certain liberties when taken in conjunction with precipitation charts don't seem unreasonable.

OK lets test out the theory on a forecast SkewT from tomorrow. (I will try do it properly for once - if I am interpreting the lines correctly)

I can see the dewpoint line close to the temperature line at higher levels. This suggests convection might be embedded or very messy. There are very strong winds up near the tropopause which would suggest a jet stream (high fast winds) and cloud tops being spread quickly at higher levels. Wind speed and direction differences are not in the key areas to affect storm development much (lower and mid levels are more important). CIN of zero shows no prevention of convection and the 200 of Cape suggest weak instability and hence weak storms. 

Looking at precipitation charts I would take that SkewT with a pinch of salt. Forecast SkewTs can be useful but need to be looked at in conjunction with other charts and the latest satellite imagery. Looks like multiple low level convergence zones occurring  which will tend to cause moisture pooling. Moisture pooling will increase the surface dewpoint and alter any forecast SkewT which does not take that into account. Wales looks like a good spot for storms again tomorrow but any cloud clearance may spark storms so keep an eye on the radar.

 

Hopefully this might start to clear a little fog around SkewT's but it is not easy to explain and after a while it becomes instinctive for some storm enthusiasts and you begin to take liberties.

 

This is a great post Brick and many thanks for taking the time to share this with the group. I'm still learning more about the science of it all so it's benefits me too. I have a lot of experience in the field and generally pick up situations quickly and I've been lucky enough to get under some absolutely monstrous storms over the years and had some very close calls which I have learnt from. There's a good few people in here with a lot of the technical knowledge and that's vital for the less experienced and betters the thread for all of us. Thanks again and keep the posts coming matey!

Cheers.Neil.

 

 

[Woodboss]

4 hours ago, Mapantz said:

Parts of Cornwall and Devon could see another deluge during the early hours.

I'm liking the FAX chart for Wednesday - marked the area of interest:

This could pose in interesting scenario for a lot of the south.Im quite liking the look of this fax myself and will be watching the skies closely!

[SarahWxm]

1 hour ago, TallPaul said:

3 points and your fave tipple are a must... your storm will arrive tomorrow (he says with fingers crossed)

Oh I hope so. Definitely keep fingers crossed for everything for me tomorrow lol  

[Woodboss]

Some development in the channel underway.Currently sitting at the top of the cliffs in peacehaven before I start work and the skies are darkening out over the channel with a few distant flashes now.

[Eagle Eye]

Woke up to a big elevated cloud blanket and thought the Storms won't going to happen this morning but oh well and realised there was a key word in there, elevated, I know I'll probably have to go outside and blow it here but fingers crossed.

[Guest]

A few showers and TS in the channel but a huge amount of mid and upper cloud debris this morning will be tough to shift today to allow surface. 

[minus10]

Interesting storm forecast from Nick this morning

Severe Convective Weather & Storms Forecast - Netweather.tv

WWW.NETWEATHER.TV

Activity in the channel growing as it moves north.....

[Sprites]

15 minutes ago, Alderc said:

A few showers and TS in the channel but a huge amount of mid and upper cloud debris this morning will be tough to shift today to allow surface. 

Yes could be alot of debris from spent storms, not good for later today.

[The Tall Weatherman]

Dan’s Convective weather forecast is looking quite optimistic today. Sadly I have to go to north wales today so I will probably miss out.

[Argyle10]

I'm in both moderates today but nothing even forecasting storm and sometimes even rain! 

[Supacell]

Much better likelihood of more widespread storms today for the vast majority of people in England. Today is a day I deem worthy of chasing. My focus is going to be the convergence zone about 50 or so miles to my south that runs Bristol to The Wash. No problem with cloud here this morning it is wall to wall sunshine through a thin layer of high cloud.

[Gordon Webb]

8 minutes ago, The Tall Weatherman said:

Dan’s Convective weather forecast is looking quite optimistic today. Sadly I have to go to north wales today so I will probably miss out.

all down to how people see it as always , seems to be near the M4 corridor seems to be where CZ will hover give or take a few miles of course has the greatest chance , going near Birmingham seems to get more uncertain and then further N than that well seems little point if you read Nick's and Dan's forecast

[Lu.]

Waking up to the sound of rain is quite possibly the best noise

[Guest]

All the crappy showers in the channel really going to hamper surface heating today. Not sure I'd be feeling very confident if I'd written a convective outlook forecasting widespread surface based storms.

[Biggin]

South coast getting battered atm

[Gordon Webb]

3 minutes ago, Alderc said:

All the crappy showers in the channel really going to hamper surface heating today. Not sure I'd be feeling very confident if I'd written a convective outlook forecasting widespread surface based storms.

to be fair Dan's forecast is more conservative than is be been made it out to be , just have to read first paragraph of 6 lines to get that impression

[Chris K]

Very grey here this morning so not sure if this will hamper things for later, but still feeling a little humid. Hopefully things develop later this afternoon as most of the models looks decent for the W country, but as always it will come down to watching radar developments and the skies.

[Ben Sainsbury]

5 minutes ago, Never On Topic said:

to be fair Dan's forecast is more conservative than is be been made it out to be , just have to read first paragraph of 6 lines to get that impression

Yes exactly. However, if we see storms kick off they'll become rather widespread with frequent lightning in places hence the MDT zone that Dan has issued.