Rotation?

[Tarmo Tanilsoo]

I shot this video yesterday afternoon as one part of approaching thunder cloud looked suspicious. If you fast forward the recording, it appears like there is some rotation, what do you think? Is there rotation? I think there is also some lowering of the cloud bases.

 

[rdale]

Looks like a ton of scud. You really need to have the camera on a tripod if you want to pick out details -- it's bouncing around quite a bit.

 

[Tarmo Tanilsoo]

I've got to agree. However, there was no time to set up the tripod. Previous rain had just stopped when I went to the spot and when I was shooting this it started to rain from this approaching cloud.

 

[Jeremy Miller]

Hi there,

I just looked at your video, the cloud structure doesn't appear to be very organized. As the above poster said, there is quite a bit scud. Fast forwarding it does appear that the entire cloud MAY be rotating (looking at it for a couple minutes by rocking it back and forth). However, again the video wasn't on a trip pod, so that could come into play. Was this a severe thunderstorm?. Typical severe thunderstorms, especially supercells tend to have really sharp defined cloud bases. Can I have more information on this storm?. storm history, what were the surface conditions before this happened?.

I'm not trying to discredit your work by any means. I just need more info before I can say what I think. At first glance, fast forwarding, again, it does appear to be rotation. But with the clip being too short and the fact it wasn't trippoded make it difficult to make a real determination. As you know and the rest us know, when we suspect rotation, we got to watch it over a period of time to confirm rotation and that its not just storm environment wind shear.

A good video though, wish there was more time to it.

Please let me know some stats on the storm and the wx conditions
leading up to it. I'd much appreciate it.

Keep up the great photography and video work.

Take care and stay safe!

Jeremy

 

[Tarmo Tanilsoo]

Here's some more information:

There was no hail, but there was 0,24 inches of rain associated with it. Following comments events what happened after the shooting. 3 minutes after shooting this(14:37), air temperature was 63,1 degrees Fahrenheit and heavy rain hit for a minute, diminishing to moderate by 14:38. Air temperature then was 62,7. By 14:40, air temperature had dropped to 61,5 degrees. At 14:45, heavy rain hit again, this time lasted over 10 minutes. At 14:49, air temperature was 61,8 degrees. 10 minutes later, air temperature had risen to 64,2 degrees.
Before shooting:
A thunder cloud had headed in. Detailed list of events follows:

Time Temp Events
14:04 69,4 Beginning of precipitation
14:05 68,0 Moderate rain
14:06 68,4 Moderate rain
14:07 66,9 Thunder heard
14:08 66,0 Loud thunder heard
14:09 65,5
14:10 65,5 Still moderate rain, thunder heard
14:11 64,6
14:12 63,7
14:13 Heavy rain begins
14:14 64,6
14:15 64,2
14:16 64,0 Thunder heard. Cloudiness gets lighter from westerly directions
14:17 61,0 Rain begins to weaken, thunder heard.
14:18 60,6
14:19 59,7
14:20 59,4
14:21 60,2 Rain only moderate now
14:22 61,0 Loud thunder heard
14:23 61,9 Thunder heard
14:24 62,4
14:25 61,9
14:26 62,4 Thunder heard. New cloud visible in the west(the same I filmed)
14:27 63,1
14:28 63,1 Rain only weak by this moment

After that I headed outside to wait the end of rain, what happened in couple of minutes. I then took a precipitation reading, what was 0.047 inches. A cloud in WNW had caught my attention as it looked to move in other direction. I started shooting it and just then, it started to rain. I rushed then to inside and reached it just before the rain started intensifying.

This time I am a little smarter, will have the tripod ready for next time.

Here are some photos.
NW sky at 14:28, taken at doorstep as it was still raining a bit(my camera is not water-proof).

WNW sky at 14:30

NW sky at 14:32

WNW sky at 14:33 - as I head to check rainfall amount and to investigate strange movement I see behind the roof of a farm building, I see this and immediately take a shot.

WNW sky at 14:34 - I am back from measuring rain(in a rush). Raindrops start falling and I quickly snap a photo of this cloud shortly before I start to film it.

--
Northwestern sky at 14:40

--
14:52 - heavy rain falling on a pavement.


Following is radar image from Latvian Environmental, Geological and Meteorological Agency at 14:30. I marked approximate location of Laguja (± 6 miles) with a plus. Please note that sometimes this radar doesn't see thunderstorms or misplaces them...

 

[Jeremy Miller]

Thanks for the pictures and the reports. Althought it was somewhat helpful, I was looking for besides temps and conditions. The dewpoint, winds, pressure, LIs, CAPE, bulk shear. ect... If you don't have that info or are not quite sure what it is thats O.K.

Looking at the radar it LOOKS like one of those sunny relatively warm days (only low to mid 60s), with no surface boundry to really focus development along it. It looks like diurnal driven convection that pops due to instability and then as the sun sets the thunderstorms become outflow dominate and collapse. I still can't say for sure whether or not that is rotation. For the few frames I've rocked it back and forth, it does appear to be rotation. However, as I said before. Rotating wall clouds are produced by supercell thunderstorms (thunderstorms with a
mesocyclone), these storms tend to have very well defined and destinct cloud bases, along with producing large hail, very vivid cloud to ground lightning, ect. This storm doesn't jump out at me as being severe. Now, again, there was not a lengthy video recording of this thunderstorm. Edit: Was thinking, with the somewhat cool surface temps, the convection
doesn't look to be focused along a boundry. This could be aided by an upper air low pressure system. Temps in the
low to mid 60s aren't nessicarily by themselfs favorable for strong to severe convection. Unless there are other contributers coming into play.

With that said. It was most likely a diurnal thunderstorm and not much more than that. Keep up the great work. I hope I didn't disappoint you or bring your excitement down. Without a real good idea of pre-storm environment at the surface and the upper atmosphere along with real detailed radar images and video, I don't feel comfortable in saying its definately rotating.

One thing I did want to ask about. Does the weather service over there use doppler radar?. And why did you mention that it misplaces storms or doesn't see them?. Is the systems they use have that bad of antenuation(sp)?.

You take care! and keep taking pictures and video, Ill keep looking at them.

Jeremy

 

[Tarmo Tanilsoo]

Yes, EMHI uses radar, but its images are not available for to the public for free(LEGMA's is) and therefore I wasn't able to get an Estonian image. That radar what misplaced storms was LEGMA.

EMHI only does soundings at 0Z and 150 miles from me so I guess, that's not much usable. Anyway, here it is.
Estonian weather data from that time can be found here. Nearest station(10-15 miles from me) is Tartu (Tõravere)

Edit: Here is ESTOFEX's convective outlook for yesterday. Following is excerpt from that:

... southern British Isles ... Baltic-Sea region ...

In a deeply convectively mixed modified polar air mass that will be present over the southern British Isles, as well as over the Baltic-Sea region, some brief non-supercellular tornadoes may occur, but these events should be too isolated to warrant a categorical outlook.

 

[Jeremy Miller]

Interesting. I do know that tornadoes can form out of non-supercell thunderstorms. I'm thinking (i could be wrong, please correct me), that this is simular to what we get in the northeast during early fall when colder air comes down from canada aloft with warm temps at surface (esp lake ontario) we get cold air funnels to spin up in afternoon convection. Due to the marked temperature drop the higher ones goes into the atmosphere.

Now that I've read more into it. It could have been some rotation simular to the cold air funnels we get up near the great lakes where I live.

If there are any meteorologists that can explain it better than I can.
(I'm not a meteorologist, but have followed and studied weather since child hood).

Thanks for the info

Jer

 

[Tarmo Tanilsoo]

Yeah, I also sent a copy of that video to a meteorologist in Estonian Meteorological and Hydrological Institute who I know. Anyway though, this was very interesting phenomenon.

 

[Jeremy Miller]

Awesome. I love the weather, whether it be a overcast dreary day or an approaching severe thunderstorm. I love it all. I have only seen 1 tornado so far in my life as a child. I've seen a couple supercells. Unfortunately up here in central new york state we don't have the ideal set up for the monster tornadic supercells that roam the plains. We do get supercells and the occasional EF2 or stronger tornado. Just not the frequency or magnetude that the plains see. We do get a good veriety of weather.

We get summer time thunderstorms. Usually along or ahead of an advancing cold front. Usually in a line echo wave pattern with bow segments, sometimes multi-celluar clusters, occasional airmass diurnal driven thunderstorms. Speaking of bow echos, we've had some pretty nasty derecho's in the past. One back in 1995 then in 1998. I remember both.
I was 11 during the 1995 derecho, I was scared when the southern end of the line plowed through. Then in 1998 at 14 got woke up by nwr at 12 midnight for a WW, turned on TWC and saw a line of solid red dropping southeast from ontario crossing lake ontario coming for me. It was such a beautiful show. I lived out in the country at this time, power went out before the line ever reached me. I could see constant lightning in the distance to my north.

Can I ask what got you into weather or severe weather?.

errr, sorry for getting off topic. Now returning to the thread already in progress.

Jeremy

 

[Andrew Khan]

The video is to short to observe rotation. Even with fast forwarding, it could be the constant, movement of the camera that simulates this "rotation".

 

[cdcollura]

Interesting cloud structure.

Looks like a section of a shelf cloud, which is outflow dominated.

Portions of shelf clouds, however are rather turbulent and rotation / movement is erratic and pretty chaotic.

Never the less, most likely not a "true" mesocyclone.

Anyway, fantastic post and details...

Thanks for sharing ;-)

 

[Doug Lee]

I'm not sure I'd call it rotation either. If it is rotating, it is very slow.

Most likely I think you were seeing the effect of ambient winds moving the storm and pushing on the sides of the cloud.