Supercell in the Netherlands

[Robert van de Velde]

Hello, I'm Robert van de Velde from the Netherlands. I am 15 years old and I live in Sint Philipsland, a village with a little more than 2000 inhabitants in the province (a province is like a county in the US) Zeeland (Zealand). I got interested in the weather a year ago when it was very muggy (the CAPE was 4000+ and that's very high in the Netherlands) and serious thunderstorms were expected but eventually I hadn't seen any thunderstorms except some ominous skies.

In the Netherlands we have a few tens of supercells every year so they are quite rare. Since I'm not yet allowed to drive a car I can't go to the storms so the storms have to come to me. I had always wanted to see a supercell above my home village. Last Sunday I got lucky when a supercell appeared right in front of my window. I was very happy because I had never seen a supercell so close by and I could clearly see the wallcloud which was above the farmlands of the peninsula (which is also called Sint Philipsland). The inflow tail came right over the village. When it was above me, I could feel that the air was sucked into the thunderstorm.

When I first reported in the mean thunderstorm thread that I had seen a supercell, some people didn't believe me (perhaps I shouldn't have called it a 'beast of a supercell', but I was very enthusiast), even after I posted some photos. There are several arguments which make it plausible that it was a supercell.

1. DLS was 20-25 m/s during the lifetime of the thunderstorm
2. My brothers car was (a little bit) damaged by 3 cm hail (while the CAPE was only around 500 J/kg)
3. The thunderstorm deviated to the right.
4. It showed a V-notch.
5. The anvil height of this thunderstorm was 8 km while the anvil height of other thunderstorm was barely 7 km. Moreover it showed a 2 km overshooting top reaching 10 km during its whole life.

Except for argument two a thunderstorm in Overijssel showed the same behavior. I suggested that this thunderstorm could be a supercell too, but somebody said: "Robert not every thunderstorm is a supercell" (that's right but he didn't have any reasons why the thunderstorm in Overijssel wasn't a supercell).

The Dutch weather radar archive can be found on http://buienradar.nl/historie.aspx. The date is 5 august 2012 and the supercell appears at 15:00 in the south of Zeeland. Tick 'toon bliksem indien aanwezig' to see lightning. Click on 'Ophalen' to get the requested image. Click on 'Volgend beeld' to see the next image. Click on 'Vorig beeld' to see the previous image. You can see the other suspected supercell in Overijssel too around that time. I think there are more thunderstorms that could be supercells but I'm pretty sure that these two thunderstorms are supercells.

The supercell that developed in Zeeland caused a lot of flooding in Rotterdam. Later a new supercell arised to the right of the old supercell and the new supercell killed the old supercell (or the old supercell killed the new thunderstorm and continued) The new supercell (or the old supercell) caused flooding in Utrecht and Hilversum and a brief tornado which caused damage was reported in Putten.

I made some photos from out of my window (unfortunately my parents didn't let me go to the wallcloud above the farmlands) and posted some of them on https://www.onweer-online.nl/forum/topic/35282/ontwikkeling-van-een-wallcloud/. In this thread I have posted some photos, a radar image of the supercell shortly after the last photo was taken and a photo of a wall cloud in Australia (not mine) to show them how I imagine a wall cloud. I've called the thread 'Development of a wall cloud' because it shows (in my opinion) the development of a wall cloud. At first I didn't see any wallcloud (or it could be hidden between the inflow tail or a tree), a little bit later the wallcloud appeared and shorty after the wallcloud got gradually obscured by a rain curtain. Some people didn't believe that it was a wallcloud. Somebody said that the tail cloud was on the wrong place but that person didn't know the difference between a tail cloud and a beaver tail. He also said that a wall cloud was a type of arcus.

So the most disappointing thing is that some people just say: "You are not right" without any reasons and not knowing what they're talking about. This has occured several times. They only believe that it is a supercell when you come up with spectacular photos or when your name is Reed Timmer.

So guys I have four questions:

1. Is this a supercell and do my photos show a wallcloud?

The updraft was on the southeastern side of the thunderstorm and the wallcloud was obscured by the rain. The radar also showed a heavy rain core and the thunderstorm caused floodings. So:
2. Is this a HP supercell?
3. Is a wall cloud an type of arcus? I don't think so but what do you think?
4. Do you mind if I post more storm reports on Stormtrack when I get to see more supercells in the Netherlands?

I look forward to the reactions.

Robert

 

[Jeff Duda]

Hello, Robert. Glad to see an enthusiast from across the pond. Regarding some of your points:

The observations you listed are not unique to supercell storms, but that doesn't mean the storm you saw was not a supercell. I was able to use Google maps to figure out specifically what area of the region that radar image was showing. That is a very large area. Unfortunately, that means that without a closer look and some Doppler velocity data, it's pretty difficult to say with certainty that the storms were supercells.

Regarding your images, there are some hints of supercell structure, but it looks very ragged. It's not the look of the typical American southern great plains supercell. However, I see what appears to be a ragged, expansive wall cloud with a tail cloud on the right edge (relative to your point of view in the images). Starting from pictures 6 and on, there looks to be a shelf cloud pushing out ahead of what may be a large, strong, wet RFD. If that is the case, then you probably were looking at a somewhat poorly shaped HP supercell. Did you see rotation in the wall cloud? Wall clouds aren't arcus clouds that I'm aware of. My understanding of arcus clouds is that they basically only form along the leading edge of a strong density current (usually a cold front or gust front) and form due to the strong lift caused by the density current. Wall clouds, on the other hand, generally develop because the parcels making those clouds have lower LCLs than the parcels around them. Thus, they condense at a lower height than do other parcels. The source of lift in a wall cloud is generally the storm scale updraft rather than a density current resulting from a push from a downdraft.

You are welcome to post accounts and images on Stormtrack all you wish. Just remember that, for a post to go in the REPORTS section of the Target Area of the forum, you must have personally gone out of your way to chase the event. Perhaps that has changed recently, but I know at one point in the past you weren't allowed to post in that section if you just watched a storm go over your home. However, you can post anything that can't go in the REPORTS section in the Weather & Chasing sections, the Sky Photgraphy, or even the Bar & Grill sections.

 

[Rich West]

Hi Robert
I am quite a newbie to meteorology and so I can't comment on your post in its details, but it is great to see your enthusiasm and willingness to tackle the complexities of observation and technical data. I would like to say hi and welcome
All the best
Rich

 

[Robert van de Velde]

Hi Jeff and Rich!

In the Netherlands, we don't have Doppler velocity images. The KNMI (Royal Dutch Meteorological Instute) has two doppler radars, but when I asked the KNMI for Doppler velocity data, they said that they didn't have the right software for it. However, they used to have Doppler images (perhaps not available to the general public) a number of years ago because I've seen some examples of them on the internet. At the moment, we have Rainfall Intensity, Lightning, Echo Tops, and an archive of Rainfall Intensity and Lightning back to 2006 (I would also really like to see images from before 2006). From what I've seen they used to have Radar Reflectivity, Lighting, Echo Tops, Radial Velocity, Vertically Integrated Liquid, Probability Of Hail, Atmosferic Wind Profiles and a bird tracking system.

Before 2006, we had to pay a meteorological company to get radar images. In 2006, buienradar.nl was launched and we from then on, we could get free radar images. The founder of buienradar.nl got the idea in the US, where he saw radar images on TV. He said that the weather in America was more extreme than in the Netherlands, but he had no doubts to do it. He paid €200000,- to get the radar images of the Netherlands and Western Europe.

Belgium has Doppler velocity data, but unless you work at an airport or a meteorological institute or pay huge amounts of money, you won't get them.

So we don't have Doppler velocity data here and that's a pity.

 

[Joshua Nall]

This has occured several times. They only believe that it is a supercell when you come up with spectacular photos or when your name is Reed Timmer.

Enjoyed your post Robert. I got a laugh out of this line, and I generally agree with Jeff's assessment. I remember the first couple of times I was able to see a supercell from where I live and it was a very exciting experience. Hope the day you can become mobile comes quickly for you.

 

[Robert van de Velde]

Thanks for your response and encouragements guys! I can't wait getting 10 inch hailstones on my car

There are new thunderstormchances here at Wednesday the 15th and Sunday the 19th.

Wednesday we will be in the warm sector of a mid-latitude cyclone. The mid-latitude cyclone pulls warm and moist air from the southern part of the North Atlantic Ocean to the north. The CAPE can rise to 2000 J/kg at Wednesday, however it seems the area with high wind shear is just west of the area with high CAPE so they don't overlap each other that much.

The weather models show a Spanish Plume at Sunday. In this situation, hot and dry air from Spain is pulled to the north by a mid-latitude cyclone. The hot and dry air serves as a strong cap so that the air below the cap can get very moist. The CAPE (MUCAPE/SBCAPE and sometimes MLCAPE) can get more than 4000 J/kg and the LI lower than -12.

Some examples:

25 May 2009:


28 June 2011:


28 June 2012:


19 August 2012 (previous run, the current run shows less CAPE but more shear):


I happens on average once a year here so it's quite rare. How often do you get these values in the US?

PS: why are my images so small?

 

[Rich West]

Love your enthusiasm, mate.

 

[Robert van de Velde]

Thanks Rich!

Yesterday (Wednesday 15 August) we got thunderstorms again. During the day I saw a lot of castellanus clouds and it was quite warm (30 degrees Celsius) and muggy, the CAPE was 1000-2000 J/kg. The DLS was 10 m/s during midday and later in the evening increasing to 20 m/s or higher (however I thought the area with good shear was behind the cold front so I didn't expect supercells). A convergence line ahead of a cold front caused a squall line. I hoped the squall line came to me but unfortunately it went over the North Sea and the northwest of the Netherlands so I thought the game was over (because I first thought the squall line was caused by the cold front so I thought that the cold front had passed but afterwards I realized the cold front had not yet passed). My younger brother asked me to go with him to play with a kite on the levee and I went with him (a thunderstorm was developing in southwest Belgium however, but I thought it would quickly die so I decided to go with him although I took my camera with me). After some time I saw a cauliflower cloud far to the south but I thought it was nothing. When I was busy with the cords of the kite, a row of low stratus clouds approached from the west. When they passed, it got windy and pretty cold. I thought the cold front had passed so I thought it was definitely over now (afterwards I think it could be the outflow of a death thunderstorm or someting like that). But after some time, I saw two pretty large cauliflower clouds on a cloud bank, although at that moment I still thought it was large stratocumulus castellanus. Some minutes later the western updraft tower became very large and I continuously heard rumbling. In the west I saw some mammatus clouds. In the southwest and south I saw a rain curtain beneath the large updraft tower. To the southeast I saw a rainfree cloudbase with a lowering beneath it and some updraft towers upon it.

I took some photo's of the lowering next to the rain curtain (I regret I hadn't taken photos earlier but I was busy with the kite and didn't recognize that it was something interesting until I heard the rumbling and saw the updraft tower). I posted two photos taken on 19:41 local time at http://www.onweer-online.nl/forum/t...13-tem-15-augustus-2012/367333/#message367348 along with a weather chart that shows that the DLS was 20 m/s or more at this time. The photos show a slight lowering and that the updraft is seperated from the downdraft. The thunderstorm died immediately when it came into an area with a DLS less than 20 m/s. It moved to the northwest while other thunderstorms were moving to the north (look at the first picture of my post at http://www.onweer-online.nl/forum/t...13-tem-15-augustus-2012/367376/#message367382 however the second picture shows that it moved according to the mean wind, but still when this thunderstorm formed, a small and short lived thunderstorm to the left of the thunderstorm that I saw moved to the north, and when the thunderstorm that I saw died, the anvil precipitation moved to the north instead of the northwest). At 19:35 it seems the thunderstorm showed a kind of V-notch.

When I posted the two photos, I clearly said that you can't be sure that this is a supercell without the help of doppler velocity data and thus I said that I wouldn't say whether this is a supercell or not. A little later, a new thunderstorm arised in the middle of Belgium and moved into the Netherlands. It showed similiar behavior as the thunderstorm that I saw (I mean that the thunderstorm seemed to be rightmoving and died when it came into an area with too little DLS). The max. cloud top of the first thunderstorm was 12km, the max. cloud top of the second thunderstorm 13km, but that was not really extraordinary because some thunderstorms in the squall line reached 12km as well. Someone remarked that the thunderstorm moved to the right. I said that I perhaps could be due to the veering winds behind a cold front (I don't know if this is right and moreover the cold front had not yet passed) or because the thunderstorm is a supercell (I meant not to say that this thunderstorm was a supercell but I used it as a possible cause of the northwesterly movement of the storm). Soon after I said this, someone said that it was just the movement of the thunderstorm and said that it was not a supercell. Another person agreed with it and said that he was getting tired of people calling thunderstorms supercell and that I should learn about supercells. Well I'm getting tired of people who say without any evidence that it is not a supercell while supercells are possible (DLS>20m/s) and while the thunderstorm looks like a supercell and behaves like a supercell.

Other people had taken some nice shots of the thunderstorm that came over me. Here are some links:

Birth of the thunderstorm and the maturity of the thunderstorm and at the end some lightningpictures of the second thunderstorm (man I love those explosive clouds):

http://www.weerwoord.be/includes/forum_read.php?id=1666263&tid=1666263&exp=1

Young thunderstorm in Belgium viewing to the west:

http://www.weerwoord.be/includes/forum_read.php?id=1665469&tid=1665469&exp=1 and
http://www.weerwoord.be/includes/forum_read.php?id=1665486&tid=1665469&exp=1

Young thunderstorm in Belgium (this man said that the thunderstorm didn't rotate):

http://www.weerwoord.be/includes/forum_read.php?id=1666075&tid=1666075&exp=1 and
http://www.weerwoord.be/includes/forum_read.php?id=1666091&tid=1666075&exp=1

Later closer to my home SSE of the thunderstorm at Gawege:

http://www.weerwoord.be/includes/forum_read.php?id=1665873&tid=1665843&exp=1

A video around the same time I took the photos: http://www.weerwoord.be/includes/forum_read.php?id=1665843&tid=1665843&exp=1
The man who filmed it was to the south of the thunderstorm near the town Tholen. My older brother was also in Tholen (he has got a car, man I wish that I went along with him so we could go to the thunderstorm) and he made some photos of the lowering and the rain curtain, although I haven't got his photos yet. He said that he didn't see the lowering rotating.

Some photos of the same man: http://www.weerwoord.be/includes/forum_read.php?id=1665888&tid=1665843&exp=1

Around the same time SW of the thunderstorm, the mammatus at the left part of the photo is probably the same mammatus that I have seen: http://www.onweer-online.nl/forum/t...13-tem-15-augustus-2012/367304/#message367318

Thunderstorm approaching and dieing at the end, view probably from the northeast:

http://www.weerwoord.be/includes/forum_read.php?id=1666235&tid=1666235&exp=1 (I think it had just passed me at the first photo) and
http://www.weerwoord.be/includes/forum_read.php?id=1666543&tid=1666543&exp=1

Tomorrow I will add some photos and videos about the thunderstorm (the thunderstorm which I started this topic about) of 5 August from other people, I'm tired now it's 23:35 here at the moment.

So what to you think of this thunderstorm (15 August)? I think it looked beautiful!

 

[Rich West]

I think the pictures are great, Robert. While I can't comment on anything technical, other than recognising the cloud types, I do appreciate the immense power and beauty captured there

Unfortunately we have very few thunderstorms here....although that may change with climate change...

All the best

Rich