Question about sounding

[Tarmo Tanilsoo]

This is 0Z sounding for Tallinn, Estonia: Link

I noticed that K index is 26,2, Total Totals index 51,4, but CAPE and Convective Inhibition are 0 and Lifted index is 8,3. On a side note, Showalter index is 2,95. What could this sounding signify?

Actually, today is the warmest day of this year in Laguja. As of writing this post, air temperature is 61,3°F

 

[rdale]

What exactly are you asking? Is that a severe storm sounding -- no...

 

[David Draun]

LI of 8.3? That is indicative of a very stable atmosphere. You got yourself a mild sunny day on your hands. The difference in the 500mb temps between the environmental and wet/dry adiabatic lapse rates or lifted index as it is called, is a very good indicator of atmospheric stability. Positive values generally indicate stable conditions, while negative values show instability. The lower the LI is, the more unstable the atmosphere. I've seen severe weather usually occur when the LI is -4 or lower. Sometimes on a really hot day, I've seen the LI as low as -17, however no storms developed due to multiple inversions. This was conditional instability.

From what I've learned, the LI value is a better measure of atmospheric stability than CAPE.

 

[rdale]

Ehhh, LI is not useful because it only looks at a few slices. CAPE integrates the entire convective area of the sounding. You can have LI -7 and just regular thunderstorms. Pop a storm with a CAPE of 4000 and it WILL be bad...

 

[JF Massicotte]

Ehhh, LI is not useful because it only looks at a few slices. CAPE integrates the entire convective area of the sounding. You can have LI -7 and just regular thunderstorms. Pop a storm with a CAPE of 4000 and it WILL be bad...

I totally agree with this one. For example if you get some slight inversion at 500mb, your Li may only show -1 but you may also find out that 0-3 km CAPE is incredible.

But you may consider that Li is a good indication of the CAPE's repartition. A higher Li can mean that CAPE is concentrated in some part of the atmosphere while a lower one will tend to show the CAPE extending all the way up.


Anyways, absolutely no number, be it Li CAPE or anything, beats a good understanding of a sounding.

 

[afischer]

Ehhh, LI is not useful because it only looks at a few slices. CAPE integrates the entire convective area of the sounding. You can have LI -7 and just regular thunderstorms. Pop a storm with a CAPE of 4000 and it WILL be bad...

The latter two sentences aside, I do agree that CAPE itself is generally more meaningful than Lifted Index because it does integrate the entire column. Similarly, Showalter Index is pretty much worthless unless your moist layer or high theta-e parcel is located right at 850mb; a MUCAPE would generally be more approriate if you wanted to "catch" all available elevated instability. However, different parameters work well for different instances. There are some cases where LI can be rather insightful. One example is the cool season, short & fat CAPE days... particularly when the width of your positive area is maximized right around 500mb. Even though the integrated CAPE may only be 500-800 j/kg, your LI can be -6 to -8... definitely approaching the "strong instability" category. These types of thermodynamic profiles tend to support stronger updrafts than one might think based on the CAPE value itself. In contrast, if nearly all your CAPE is located below 500mb, a 0-3km CAPE value alone might be more meaningful. In the end, as the previous poster stated, it is better to closely assess the shape and quality of the sounding rather than get too caught up in a particular parameter value.

 

[rdale]

I highly recommend Skew-T Mastery (along with many other webcasts) at http://www.meted.ucar.edu/topics_convective.php

 

[Tarmo Tanilsoo]

What exactly are you asking? Is that a severe storm sounding -- no...

That was what I asked, what I thought and just wanted second opinion. I realized that as well, only 3 indexes were marked red by Sounding Analyser. Sorry for late answer, I was in EMHI today on a conference and travelling there and back took several hours.