Definitive Guide to Skew-Ts and Hodographs - Part 3a - Calculating Parameters from a Skew-T
ฝัง
- เผยแพร่เมื่อ 3 มิ.ย. 2024
- Welcome to my Definitive Guide to Skew-Ts and Hodographs! In this multi-part series, we'll take a deep dive into deciphering those complicated skew-T log-P diagrams and hodographs, which are both critical tools in severe weather forecasting.
In this video (Part 3a), we'll begin a multi-part discussion on how to calculate environmental parameters from a skew-T.
Contents:
0:00 Introduction
1:54 Parcel trace review
2:30 Lifted condensation level (LCL)
5:49 Level of free convection (LFC)
8:03 Convective available potential energy (CAPE)
9:43 Convective inhibition (CIN)
12:50 Equilibrium level (EL)
14:58 Tropopause height
17:53 Convective condensation level (CCL)
19:57 Convective temperature (ConvT)
22:20 Maximum temperature (MaxT)
Check out the previous videos in the series here:
Part 1: • Definitive Guide to Sk...
Part 2: • Definitive Guide to Sk... - วิทยาศาสตร์และเทคโนโลยี
Trey, this series is the greatest thing I’ve ever stumbled upon. Perfectly presented in a smooth and easy to follow fashion. NOBODY else I’ve seen on TH-cam has done this thorough of a break down. Thank you for this 10 part serious. A seriously invaluable source of information
Thank you so much! I'm really glad you found it helpful!
Taking a second to thank you for doing these videos on SKEW-Ts. As an amateur chaser, enthusiast I am completely self taught. I've had a basic understanding of reading soundings but your explanation and detail is really helping me to understand a lot better. I really appreciate you taking the time in sharing your knowledge.💯
It's my pleasure to do these videos; I just really enjoy sharing my knowledge and helping others learn about meteorology. I'm so glad to hear that these videos are helpful!
@@ConvectiveChronicles Definitely 👍
This series is VERY nicely done! The segments are perfectly sized chunks of information and the content is always relevant to the processes discussed. Thank you VERY much for making this available. I know this takes time and I am sure everyone that watches (including myself) is truly grateful for you putting this together. Take care!!
Thank you so much for the kind words; they really mean a lot!
By far the best skew-T videos on TH-cam. Thank you!
Thanks so much for the kind words!
I'm so so grateful that you've invested so much time to make these videos! I'm really enjoying these so far
I’m glad you’re enjoying them! Thank you so much!
Glad I can finally take the time to go through a couple more of these videos and give them the attention they deserve! So well put together and some of the prettiest notes I've taken on a subject. I have a whole section in my Notability (note taking app) dedicated to your channel. :-)
Thanks so much! So happy to hear you've found the videos helpful!
It took a while to get my head around the difference between lifting condensation level and the the convective condensation level. It eventually dawned on me that LCL is where any parcel of air is lifted mechanically, eg by a front, whereas the CCL is a non-average heated parcel from a particularly warm area of ground that has risen as a thermal. As a glider pilot the first three videos were particularly useful.
You’re exactly right! Happy to hear you found the videos useful!
I second the praise from the amateurs! As a lifelong Oklahoman, weather is just a part of life and if you don't know weather here, you won't enjoy your life much. LOL You might get blown away by a nader, frozen, or turned to dust. Maybe all in the same day. Anyways, I love being my own meteorologist and am very glad to find such a detailed explanation of weather balloon data!
Thank you for watching; glad you enjoyed it! Absolutely, Oklahoma weather is one of a kind!
Tray, while now "retired" from "formal" chasing, I've been at it in some form since 1991 and have studied several written documents about Skew-T's, including trying to ingest a good portion of the USAF document AWS/TR-79/006 training manual. Unfortunately, I learn best by demo; not by digesting written text. Your Skew-T videos have, above and beyond anything else, finally opened up my better understanding of how they're plotted, how the parameters are determined and most importantly, what they all mean in the forecasting process. Knowing the amount of time it has taken you to put these together, I cannot begin to express my thanks for your stellar and hard work. Kudos!
Thank you so much! I’m really happy to hear they’ve been helpful for you!
Fantastic, these videos are far more informative and breaks down to an easier format. I have looked at lots of these videos and have found them a bit either too technical or too complicated These videos are just great and the right amount of information over the three videos. Fantastic and a big thank you.
Really happy to hear that; thank you for the kind words!
It's been a while since so many dots have connected at once. Thanks
Thank you so much for the video. Couldn’t find any others quite this good!
Thanks so much for the kind words! Really glad to hear you enjoyed it!
Great job explaining on how to calculate parameters on a skew-t. Relly learned a lot in this one. 🙂👍
Thank you, glad it was helpful!
@@ConvectiveChronicles Your welcome.
Great Series, thanks!
Thank you!
Thanks so much for the video bos❤
You bet; thank you for watching!
Awesome!
I am going to this vdieo. I am also a self taught geek . This is so rich!
Hello, great video series! Should we calculate the CAPE based on the LCL or the CCL, if we do not know a priori what the lifting mechanism will be? The CAPE linked to the CCL is much bigger, hence the importance of knowing what to do.
Thank you! You should always calculate CAPE based on the LCL associated with whatever parcel you're using (surface, mixed-layer, etc.).
I appreciate you.
I am a self-taught enthusiast and cannot thank you enough for this series and your willingness to teach this topic. I live in Virginia and usually only see two soundings a day from Wallops Island. Most of the lessons on TH-cam regarding these diagrams seem to often show storm specific radiosonde data. Our local NWS office out of Wakefield doesn't seem to show soundings from storm specific events. Are these soundings taken during/before storms in areas where supercells are more prevalent or is there another place I should be looking for more data? I do notice a nationwide series of data at 0000Z and 1200Z. Should I be using the more westerly data as the day progresses between those two time periods?
I’m very happy to hear the series has been helpful! As you said, these soundings are released daily at 12 and 00z all across the country; you can access them from the SPC webpage (hover over Forecast Tools on the homepage, then click on Observed Sounding Analysis). These are released regardless of whether there’s a severe storm threat or not. That said, NWS offices in areas with a threat for severe storms on a given day will release additional soundings (e.g. 18 or 21z) to help forecasters see how the atmosphere is changing. The SPC also has a severe weather event archive that has outlooks, mesoanalysis data, and all soundings from most severe weather events dating back to the early 2000s.
In your case, you have a few soundings that might be useful: Wallops, Dulles Airport, and Roanoke. You don’t really need to use the more westward soundings on a severe weather day for you, although it might tell you what kind of environment is upstream from you. That said, soundings are just one of many tools to use when forecasting severe weather; upper air/surface maps will tell you more information about an environment that might advect into your area than just a series of soundings.
Very helpful video! I have a question about something. I would like to know what the Supercell section on the Sounding analogs mean? I see in it saying 3 loose matches 67% TOR
Thank you; glad to hear you found it helpful! To answer your question, the Supercell section in the sounding analogs box takes a bunch of different past events that produced supercells (non-tornadic, weak-tornadic, and tornadic) and tries to find events with similar thermodynamic/kinematic environments. "3 loose matches 67% TOR" means that it found 3 events with somewhat similar environments, and 67% (2 out of 3) of those produced tornadoes. Coming up, I will be doing a couple videos in this series solely dedicated to deciphering every box and parameter on the SPC soundings.
Thankyouu very muchhhhhhhh 👍❤🤩🤩
Where the red temperature line starts to kick back near about the 530mb level, is that what meteorologists refer to as the "cap?" As in breaking the cap, where warmer air aloft may stop convective thunderstorms from firing?
That little warm nose just below 500 mb would be considered an inversion, but the main cap would be that significant warm nose down at about 900 mb. Usually, the "cap" that inhibits storm formation will be present in the low to mid levels.
Hearing some of the abbreviated terms and what they mean (LCL, CCL, LFC, etc) is really helpful to me since I've seen many other videos mention them and I never knew what they meant. However, I was curious as to why the computer model on the Skew-T chart and your estimations don't align sometimes? For example the equilibrium level is 150+ millibars different. Why does this happen? Thanks for the helpful video.
Thank you; happy to hear this was helpful! It’s probably different because they are using a different parcel. In this example, I used only the surface parcel to calculate them (i.e. starting at the very bottom of the skew-T and calculating values using the surface temp/dew point). As far as the equilibrium level goes, I’m not sure why they have it there, as it’s supposed to be the point above the LFC where the parcel becomes cooler than the environment, and that clearly doesn’t happen at their EL.
@@ConvectiveChronicles The only thing I see in the graph is that EL is labelled at a sharp turn in dew point temp, so maybe that has something to do with it. Thankfully I actually know how to calculate equilibrium level now so I guess we don't have to worry too much about that.
Is the CIN the "cap" that I hear people refer to that must be broken through to develop thunderstorms? Or is that something else?
Correct, CIN is convective inhibition, which is a measure of the cap.
Might be a silly question, but is the parcel temperature measured or calculated in the sounding? Environmental temp and dew point makes sense. The sounding hardware measures the air temp and humidity while rising through the air column. But how is the parcel temp obtained? Is there like a small container of surface air captured at the ground that goes along with the hardware as it rises and measured internally or was there a calculation that I somehow missed. Great content. thank you so much.
Thank you! The parcel temperature is not a measured/calculated quantity; it is simply the plot of what a hypothetical parcel of air would experience thermodynamically if it were to rise in the atmosphere. I explained how to plot it in Part 2 of this series; basically, you find the lifted condensation level (LCL), below which parcels would rise using the dry adiabatic lapse rate. Once they become saturated at the LCL, they would rise following the moist adiabatic lapse rate because they are theoretically full of moisture. So up from the LCL you'd draw in the parcel trace along the associated moist adiabat line.
@@ConvectiveChronicles I rewatched part 2 and yes i somehow missed that calculation. thanks for the explanation. I get it now.
What is the ideal LCL for more photogenic tornado? Obviously the lower the better but sometimes too low and the tornado visual isn't great.
There’s no real threshold, and it has more to do with the overall wind profile in the atmosphere, but a little bit higher LCLs (but not too high) are often better.
@@ConvectiveChronicles and what number would be too high? In general...
@@ConvectiveChronicles thank you for doing this series. I want to get better with skew T and hodographs
@@JohnnyH71983 The general rule of thumb for tornadoes is about 2000 m, but I've seen some occur with higher LCLs (generally on the High Plains...usually these are quite photogenic).
A bit confused on environment temperature and parcel temperature. Isn't the environment made of parcels? Maybe the sunlight has to do with it?
The parcel trace shows what a hypothetical parcel, or box, of air would experience if it were to be released in this environment. The environment temperature is the actual temperature of the environment. These hypothetical parcels are independent of the environment.
On some Skew Ts its hard to find out where the Parcel Trace is. Is there always a Parcel Trace on every Skew T?
So the parcel trace is technically not a part of a raw skew-T, but it is (almost) always drawn in either when doing it by hand or on weather data sites, like the SPC site. Since skew-Ts are used to assess instability, a parcel trace is a necessity, so if you come across a skew-T that doesn't have a parcel trace, you can always draw one in manually by using the method I outlined in the earlier videos in this series (i.e. find the LCL, then follow the moist adiabat up). Now, there are multiple parcel traces that can be drawn using different starting parcels, such as the mean-layer parcel, most unstable parcel, etc. (we'll talk about this in depth in an upcoming video).
@@ConvectiveChronicles Thank you Ill look at SPC right now.
@@ConvectiveChronicles Thank you for pointing out the soundings on SPC. Their parcel trace is in blue line?
@@LegitChristian On the SPC soundings, the parcel trace is the prominent dashed brown curve. SPC plots the most-unstable parcel trace, which often overestimates instability, but for a qualitative assessment, it works well enough.
@@ConvectiveChronicles thank you.
3:50
.
so seeing a "high" LCL...... that means the storms are going to be high based?
and seeing a "low" LCL..... means the storms are low based?
.
at least generally
Exactly! It's somewhat of an oversimplification, but you can usually approximate the height of the cloud base by the LCL.
Why is the height of LCC and CCL not the same when LCC is where air saturates and becomes cloud whereas CCL also is also nevertheless the same
LCC?
@@ConvectiveChronicles sorry I mean LCL
That MaxT explanation doesn't make sense if you have solar heating.. It would make sense if the parcel of air from that height were to be pushed down to the surface maybe? But if you had solar heating then surely the air at the surface can heat up much more? I don't get it.
Following the dry adiabat down from our starting point at 100 mb above the sfc and then adding 2 degrees C accounts for solar heating, as pure solar heating steepens lapse rates close to that DALR and can introduce that superadiabatic contact layer near the ground as I discussed. Overall, it's a silly parameter that is not often used.
@@ConvectiveChronicles Thank you for trying to explain it further. I'm just a private pilot so not really learning about this subject in depth. Maybe that's why I still don't get it. Maybe if you could just clarify for me is MaxT supposed to be roughly equal to the forecasted max temp on a given day?
@@markor2476 Yes, it's an estimate of the maximum temperature a given environment might see. I wouldn't worry too much about it; I have never used this parameter in any situation; it's much easier (and probably more accurate) to just grab the max temp from the NWS.
@@ConvectiveChronicles Cool, thanks. Great vids, I learned a lot about SkewTs and how to read them even better to understand the weather forecast for my flights. 👍