Glaciated sounding?

[azure]

Lately I've been looking for opportunities to get experience in actual IMC, which are few and far between in winter around the Great Lakes. I just noticed that the forecast sounding between 900mb and about 750mb, for my home field tomorrow at from about 19Z on, looks a lot like the upper parts of many Skew-Ts when there are high cirrus clouds, which are usually glaciated. The T and DP curves parallel each other but are usually a few degrees apart. Now the skew-Ts for nearby airports don't look like this and some show the T and DP curves actually touching, so maybe this is due to something else, such as air that isn't quite saturated to the point of condensation, or even a model artifact... But these temperatures are so cold, in the mid -20s by 5000 MSL or so that it's hard to imagine there's much liquid water in any clouds that will be up there. Yes I know -- the theoretical limit is still colder, -40. But what are the chances of encountering structural icing in clouds this cold?

This is probably going to remain a theoretical "what if" kind of question unless I can be really sure the clouds are completely glaciated. I don't fly a FIKI bird and at these temperatures, I don't really have an "out" unless I can get on top for long enough to sublimate the ice, and then get back down without going through the nasty stuff.

 

[Marauder]

What type of clouds are forecasted for your flight levels? Rime will form in the 10 to -20C range in stratus clouds. Clear icing in the 0 to -10C. Other factors will come into play, like air mass moisture. Most icing I have seen has followed the temperatures ranges above, but I have been surprised a few times with the occasional mixed icing or freezing drizzle at temps around freezing.

If you are not flying a FIKI or turbo airplane, your most logical "get of out there strategy" will be to descend below unless you have a decent tops forecast.

I should also add that I look at the airmets/sigmets for additional clues. The Garmin Pilot I use also provides icing prediction charts that help visualize potential areas of concerns. Here is one example:

 

[azure]

Thanks Scott. I recall seeing a short workshop on your site not too long ago about a scenario where you took off from a field in western MI into very cold IMC confident that there was nearly zero icing potential in those clouds. The clouds were glaciated based on the Skew-T, but also there was shallow lake-driven precipitation rather than a convectively driven environment, and the lapse rate was much less steep. Do I understand correctly that the lack of convection was the main difference between that case and today?

And yes, the clouds are stratocumulus, it's very obvious they have more vertical development than ordinary stratus clouds. Much like the ones in the area yesterday, and these seem to have more moisture (at least, they're darker as seen from underneath). Yesterday I was on the way to northern IN getting badly beaten up by choppiness and was very tempted to get a pop-up to go through the thin layer to smoother air on top, but I remembered your warnings about the potential for lots of supercooled water near the tops of stratocu clouds. But those cloud tops were a lot warmer than today's, in the -15C range. I'm rather surprised to see the potential for so much supercooled water at temperatures in the mid -20s, at least outside of summertime convection where there is usually a lot more water vapor in the atmosphere to begin with.

Where can the condensate forecast images be found?

 

[N801BH]

..... I don't fly a FIKI bird and at these temperatures, I don't really have an "out" unless I can get on top for long enough to sublimate the ice, and then get back down without going through the nasty stuff.

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Be very careful trying to get actual IFR...... Wrong time of year, in that type of equipment..

 

[azure]

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Be very careful trying to get actual IFR...... Wrong time of year, in that type of equipment..

That's why I'm asking lots of questions and NOT just upping and doing it.

 

[azure]

It's part of my Internet Wx Brief Roadmap shown below. Scroll to the right in the thumbnail bar and find the thumbnail image labeled WRF-NMM (black circle below). Click on this thumbnail and you'll find the condensate forecast selection on the left of the images.

Okay, I see the forecast. What are the units for the scale at the bottom? Also, I think I understand the valid time notation but want to be sure: it looks like YYMMDD/HHMMVXXX with HHMM in UTC - I don't understand the VXXX part though.

 

[bbchien]

Dr A- I think if you get offered a java update, DON'T take it. I just updated my home station and now I can't see the sounding. My laptop and office still work, however.....sigh.

 

[azure]

Dr A- I think if you get offered a java update, DON'T take it. I just updated my home station and now I can't see the sounding. My laptop and office still work, however.....sigh.

Yuck, Bruce. I wonder what happened there? I keep getting offered java updates, but they fail when I try to apply them. I guess I've been lucky.

Of course you can still get the GIFs, but the java ones offer a lot of functionality. Bummer.

 

[gismo]

Yuck, Bruce. I wonder what happened there? I keep getting offered java updates, but they fail when I try to apply them. I guess I've been lucky.

Of course you can still get the GIFs, but the java ones offer a lot of functionality. Bummer.

It's my understanding that the Zero Day virus is a real threat to the Java RTE. I think Oracle has a preventative fix for several different versions, at least 5 through 7.

 

[azure]

The units are in mm, but don't worry about that for now. Blue stuff is very low amount of condensate and the purple stuff is likely associated with deep, moist convection. White is likely totally clear sky.

I asked because I'm a physics type person and I like to know what these images are actually saying.

V012 means a 12 hour forecast. V036 means a 36 hour forecast.

Okay, thanks.

Looking at the radar images tonight from GRR and APX it looks very similar to the situation in your scenario, with an artifact of missing lake snow from overshooting (the METAR at KLDM confirms that there's snow falling in between). So the precip is likely shallow, with no deep convection. Surface temperatures are anywhere from -15C down to -18C, cloud tops around -30C and all the Op40 soundings look glaciated. CIP and FIP show very low icing probabilities over the next couple of hours in NW lower MI (at least, over land) despite lots of clouds and snow. It wouldn't be a nice night to go flying with what look like blizzard conditions in places, but I guess the chances of getting iced up are pretty low. Does that sound about right?

 

[azure]

And yet...

TVC UA /OV TVC270015/TM 1322/FL060/TP C208/TA M28/IC MOD MX
TVC UA /OV TVC/TM 1338/FL060/TP E45X/SK UNKN005-TOP060/TA M30/IC MOD RIME

although the radar & satellite images, and the soundings, are little changed from last night... and the temps are WAY down there.

 

[Marauder]

And yet...

TVC UA /OV TVC270015/TM 1322/FL060/TP C208/TA M28/IC MOD MX
TVC UA /OV TVC/TM 1338/FL060/TP E45X/SK UNKN005-TOP060/TA M30/IC MOD RIME

although the radar & satellite images, and the soundings, are little changed from last night... and the temps are WAY down there.

No disrespect to anyone in the weather forecasting world... I often find that what is forecasted versus what actually happens do differ. Flying for years in upstate New York with the lakes acting as variables, I can't tell you the number of times I flew in forecasted good weather only to find myself in lake effect snowfall.

The same holds true for icing. No icing forecasted and yet I have seen where one plane in the same vicinity as mine is talking to a controller about picking up significant ice and I am at the same altitude, 5 miles away and I'm not seeing anything.

Where the strengths in forecasts come into play is making the go/no go decision. Additionally, I rely on the forecasts to know where my escape path is should be if things turn out differently than forecasted.

Forrest Gump summed it up best "Weather is like a box of chocolate, you never know what you are going to get".

 

[azure]

In fairness to the weather forecasters, the above paragraphs were MY inexpert interpretation. The Skew-Ts from last night and this morning still had one feature that might be concerning, a fairly steep lapse rate up to about 6000 MSL. So the lower atmosphere is unstable and likely to do a good job of squeezing out whatever moisture there is available. (Although, even Scott's condensate forecast is showing very low amounts up around TVC today, if I'm reading it correctly.)

Anyway, I don't think anyone would argue with you that observations trump any forecast. We're a long way from 100% accuracy in forecasting, that's for sure.

 

[azure]

On go-no go decisions, what's been drilled into me is to always have a sure out. That's why I'd have to be pretty confident there was no ice in the clouds before I would enter them as long as temps are subfreezing down almost to the surface, again unless it was a VERY thin layer and I was climbing to clear conditions on top, AND I was sure of not having to go down through it again after sublimating off whatever I picked up in the climb. (Actually, Sunday going down to KMIE met most of my criteria, except I wasn't sure I wouldn't pick up a LOT of ice in the tops of those stratocu clouds, so I played it safe, and I still think that was probably the best decision.)

 

[Marauder]

On go-no go decisions, what's been drilled into me is to always have a sure out. That's why I'd have to be pretty confident there was no ice in the clouds before I would enter them as long as temps are subfreezing down almost to the surface, again unless it was a VERY thin layer and I was climbing to clear conditions on top, AND I was sure of not having to go down through it again after sublimating off whatever I picked up in the climb. (Actually, Sunday going down to KMIE met most of my criteria, except I wasn't sure I wouldn't pick up a LOT of ice in the tops of those stratocu clouds, so I played it safe, and I still think that was probably the best decision.)

We certainly have come a long way with weather products that are available for aviators. Even with what is available, we still see folks ending up on the wrong end of the engagement with weather.

It's too bad that after you enter your flight plan on your GPS that someone hasn't invented a warning light that computes weather along your route and flashes a big red IDIOT in your face when you are making the wrong "go" decision. It would be so much easier that way

 

[azure]

Dr A- I think if you get offered a java update, DON'T take it. I just updated my home station and now I can't see the sounding. My laptop and office still work, however.....sigh.

I've been bitten too now -- and it is NOT a java update since my java plugin was last updated in October, it is Firefox itself, just updated. 18.0.1 is incompatible somehow (the plot is blank and says Inactive Plugin).

edit: it turns out that Firefox 18.0.1 was incompatible with my installed Java -- and that I needed the Java update to make the soundings display again!

So for now anyway, all seems to be good.