Any chance of icing at 15,000 feet?

[Scott Dennstaedt, PhD]

So it's -30°C at 15,000 feet over Boise, Idaho at the end of February.  Any chance of icing at this altitude based on this Skew-T diagram?

[Jerry 5TJ]

Not much, given the dew point spread. 

If there is, it will be too cold to cycle the boots, however:  Boot operations are limited to warmer than -30C.  

 

[kmyfm20s]

I’m going to say no but I have a feeling I’m going to get an edgamacation on this:) No visible moisture and below -20.

[Raptor05121]

Scott, do you have any videos explaining how to read a Skew-T?

[Scott Dennstaedt, PhD]

3 minutes ago, Raptor05121 said:

Scott, do you have any videos explaining how to read a Skew-T?

Alex,

About 25 workshops including a couple recorded webinars on the Skew-T. 

[kortopates]

At almost -30C chances icing in even saturated air is very small and here we’re not near saturated. Should be minimal chance if any.
But interesting we see a small temperature inversion up a bit higher.
look forward to learning what I am missing!


Sent from my iPhone using Tapatalk

[gsxrpilot]

6 minutes ago, Raptor05121 said:

Scott, do you have any videos explaining how to read a Skew-T?

I tried them all but really needed a Skew-T for Dummy's video.

A good place to start is, where the heavy Blue and Red lines touch, there will be IMC conditions. Then look at the edges of the chart to see what altitude it will be at, and what temperature it will be. Freezing or below will likely be icing. 

The lines aren't touching on this chart so we don't think there's much chance of icing here.

 

[garuda]

Maybe not at 15000 ft but when coming down roughly between 8000 and 12000 ft?

[N201MKTurbo]

I thought the lines need to cross to have clouds? The sky should be clear, unless I have my lines backward and it is solid clouds the whole way up...

[ArtVandelay]

I thought the lines need to cross to have clouds? The sky should be clear, unless I have my lines backward and it is solid clouds the whole way up...

I think clouds possible from 7000-12000.

[Robert C.]

Reminiscent of Scott's post a while back "a nasty icing signature." The big difference is the big dry zone before we get to the inversion, suggesting that there isn't that much moisture to be trapped, and the temperature -30C. The saturation mixing ratio analysis doesn't seem applicable at 15k feet here.

Interesting that you/Scott cut the CAPE from the numbers box. Looking at the chart the moist adiabat line would be to the right of the actual red temp line...i.e. instability...chance of convective clouds reaching 15k, hence icing possible?

Robert

 

PS: love these puzzles

[gsxrpilot]

One thing to remember when reading these charts. The altitude is Pressure Altitude. And so that's MSL and not AGL. 

[Scott Dennstaedt, PhD]

 

3 hours ago, Robert C. said:

Reminiscent of Scott's post a while back "a nasty icing signature." The big difference is the big dry zone before we get to the inversion, suggesting that there isn't that much moisture to be trapped, and the temperature -30C. The saturation mixing ratio analysis doesn't seem applicable at 15k feet here.

Interesting that you/Scott cut the CAPE from the numbers box. Looking at the chart the moist adiabat line would be to the right of the actual red temp line...i.e. instability...chance of convective clouds reaching 15k, hence icing possible?

Robert

 

PS: love these puzzles

Robert,

I didn't cut the CAPE out of this chart.  This is a radiosonde observation and they don't include CAPE on RAOBs. But this might help.

[Scott Dennstaedt, PhD]

Wrote up some more details in my blog here.

[HXG]

7 minutes ago, Scott Dennstaedt said:

Wrote up some more details in my blog here.

Scott, great discussion.

I had a feeling this case was setting us up to disregard the instability producing the possibility of icing. The CAPE value is less impressive than I thought it would be, but I think the important point is that of the instability overshoot of cumulus clouds above 15,000 feet. Looks like 19,000 feet or higher would be better altitude option, but certainly not high enough with a significantly greater instability/ higher CAPE and higher temperatures.

 

[Danb]

On 3/3/2021 at 2:33 PM, Scott Dennstaedt said:

Wrote up some more details in my blog here.

Read the blog, which points to ones extreme knowledge in this area is necessary to see the big picture, my first inclination was there would be no ice, after reading the blog which depicted a different answer. Scott I have no clue how to put together the necessary elements to give me a good prediction. Jeez that’s hard, I’ve read a few books on skew t and beyond the basics wow..

[Scott Dennstaedt, PhD]

1 hour ago, Danb said:

Read the blog, which points to ones extreme knowledge in this area is necessary to see the big picture, my first inclination was there would be no ice, after reading the blog which depicted a different answer. Scott I have no clue how to put together the necessary elements to give me a good prediction. Jeez that’s hard, I’ve read a few books on skew t and beyond the basics wow..

Dan,

Good feedback.  Even though I sell a weather book, this is just the foundation.  Important, but there is a need to learn how to integrate all of this guidance so you understand how to characterize that big picture.  I have been doing a 1-on-1 online training with pilots over the last 15 years for flights they are looking to take. This makes it real and likely one of the best ways to learn how each piece of guidance contributes to making a good decision. Given that each weather event is unique, it’s really hard to put this kind of training in a book. So seeing it all in action for a flight you may take is something you just can’t get from a book. 

 

 

[ArtVandelay]

Read the blog, which points to ones extreme knowledge in this area is necessary to see the big picture, my first inclination was there would be no ice, after reading the blog which depicted a different answer. Scott I have no clue how to put together the necessary elements to give me a good prediction. Jeez that’s hard, I’ve read a few books on skew t and beyond the basics wow..

That’s why I rely on weather forecasts (TAF, windy, aviationweather.gov, usairnet.com, etc).