Why??

[tonycondon]

Here is the sounding for Ames right now:

its freezing outside, and has been snowing all day. looks to me like basically solid cloud layer from ground to really high. I would naturally expect a fair amount of ice. Although, I have always heard that snow filled clouds are often ice free because the precip in them is already frozen. it makes sense. that nice dry snow will just bounce off the wings. My question, is how, from the forecasts, am i supposed to know that? the CIP is as follows:

fairly variable situation at 4000 feet, but generally below 50% probability, and something in the 15-25% range for the area of the sounding above. Here is the vertical cross section for the short path shown above. (I love the Flight Path Tool btw)

the airport is about in the middle of the path, so it appears that theres about a 15% probability all the way up to really high. Is this a case where its just too cold for ice? Since there is no extra water content like SLD etc, all the moisture is frozen? Satellite page on aviationweather.gov isnt working so i cant post infrared sat picture...sorry Scott

 

[KennyFlys]

For a second there, I thought I saw an Alfred Hitchcock profile.

 

[flyingcheesehead]

Here is the sounding for Ames right now:

I see you're using the Bak20 sounding now. I noticed last time I used the site that Op20 is now gone, so I was using Op40. What's the difference between Op40 and Bak20?

Also, what's up with that spike right at 25,000 feet? Looking at the winds on the right, it looks like there might be a shear layer there. Is that the only cause?

And I keep getting the red lines confused - The ones that are marked near the bottom are temperature - What are the ones that are marked just under the 600mb line and oriented to the left of vertical?

 

[tonycondon]

I see you're using the Bak20 sounding now. I noticed last time I used the site that Op20 is now gone, so I was using Op40. What's the difference between Op40 and Bak20?

Also, what's up with that spike right at 25,000 feet? Looking at the winds on the right, it looks like there might be a shear layer there. Is that the only cause?

And I keep getting the red lines confused - The ones that are marked near the bottom are temperature - What are the ones that are marked just under the 600mb line and oriented to the left of vertical?

Kent - my understanding is that the Op20 used a higher resolution grid than the Op40, which is why scott told me to use it last year. the Bak20 is the same resolution (i think) just on the backup server (maybe?)

the solid red line is temp. the other one you are talking about is the wet lapse rate, im pretty sure.

 

[bbchien]

And Here's CMI....

The slope of the red/blue convergence is nearly horizontal, e.g flatter than the wet lapse rate. So there is MORE moisture contained, than fully saturated air can contain. Therefore it's in the form of liquid, as the flakes can't contain much water mass.

Sure enough, CMI has Freezing drizzle. The slope at Ames is too near the moist adabatic lapse rate lines.

 

[AdamZ]

And I keep getting the red lines confused -

Consider yourself lucky. I don't even have the slightest clue how to read a Skew T, I don't know what it tells me and didn't even know what it was till someone posted one within the past year. Wish I knew what I was looking at so I could give an intelligent comment so for now I'll just say "mmmm seems like bad Wx in the midwest."

 

[EdFred]

My question, is how, from the forecasts, am i supposed to know that?

I just wait for someone in a FIKI plane to go up and get the PIREP.

 

[sba55]

I just wait for someone in a FIKI plane to go up and get the PIREP.

Since I now fly a FIKI plane, I find myself to be more worried about ice and properly understanding ice has become more important to me.

Conditions in which I simply wouldn't have flown before now become fly-able for me. This is especially true because I generally won't encounter ice in the flight levels in cruise (sometimes, obviously, this isn't true and there is ice there). So, in a sense, my margin for error has decreased. I feel fairly comfortable flying through light ice and I could deal with moderate, but I want to avoid anything more than that at all costs. Finding out where frz rain might be or where I could get into SLD has become a lot more important to me.

Don't want to take this thread off-topic, just saying that FIKI just means that you have to know this stuff to an even greater extent...

-Felix

 

[EdFred]

Don't want to take this thread off-topic, just saying that FIKI just means that you have to know this stuff to an even greater extent...

-Felix

Which is why I never really bothered learning the skew-t charts and everything icing. I just used the ROT of between 0 and -20C I'm not going in the clouds unless they are going to be less than 500' thick.

 

[EdFred]

And how do you tell if an overcast deck is less than 500 ft thick? Sounds exactly what the Skew-T diagram is perfect to identify.

PIREP. In the Great Lakes the only good forecast is a pastcast.

 

[gprellwitz]

Don't want to take this thread off-topic, just saying that FIKI just means that you have to know this stuff to an even greater extent...
-Felix

Kind of like how getting an instrument rating merely means that you need to understand weather so much better!

 

[Ted]

Don't want to take this thread off-topic, just saying that FIKI just means that you have to know this stuff to an even greater extent...

Like the instrument rating, FIKI just makes the go/no-go decision that much harder in a number of cases.

I read this stuff with interest, and will need to be learning more of it, especially as I get to the point of flying FIKI planes.

 

[sba55]

Kind of like how getting an instrument rating merely means that you need to understand weather so much better!

Good analogy!

Felix,

Most definitely. A lot of my one-on-one online training focused on icing are with pilots flying aircraft with certified IPSs.

Scott, at some point, I might just do something like that. Lots of options in a turbo'd pressurized twin.

-Felix

 

[bobmrg]

Consider yourself lucky. I don't even have the slightest clue how to read a Skew T, I don't know what it tells me and didn't even know what it was till someone posted one within the past year. Wish I knew what I was looking at so I could give an intelligent comment so for now I'll just say "mmmm seems like bad Wx in the midwest."

The Glider Flying Handbook (FAA-H-8083-13, available on the FAA web site), has a good discussion of Skew-T; I have a quick-and-dirty discussion in both my private pilot and advanced pilot books....but to really know what is going on you need Scott's program.

Bob Gardner

 

[flyingcheesehead]

The operational Rapid Update Cycle (RUC) model runs at NCEP (where I used to work). They also run a backup version out at FSL (where it was developed). Both are available to you. Bak20 should be identical to Op20 in most cases.

Aha, Cool. I guess I'll use Bak20 then, since Op20 is gone at the moment.

Looks like you need some training.

Darn skippy!!! Problem is, most weather stuff goes right over my head. I understand about half of the stuff you talk about, the rest is trying to build on a weak foundation. I do at least find your stuff interesting! Many of the weather videos I've attempted to watch in the past simply put me to sleep.

I know what I consider to be "the basics" - high and low pressure, what they do with wind, the general vertical shape of warm and cold fronts, etc. but when you start talking about glaciated clouds, I just sit here and feel dumb.

Do you (or anyone else) have any more basic courses where I can build a better foundation for understanding weather (preferably something that remains interesting and relates it to flying, to keep me awake!), so that I can get more out of your advanced stuff? Thanks!

 

[Ted]

I know what I consider to be "the basics" - high and low pressure, what they do with wind, the general vertical shape of warm and cold fronts, etc. but when you start talking about glaciated clouds, I just sit here and feel dumb.

I get the feeling that a pretty good number of pilots, including those who fly FIKI airplanes into ice, probably have a similar level of understanding. My feeling could be wrong, but it seems that this sort of information is not as commonly known as it ought to be.

I'm thinking I may get some of Scott's ice CDs before long, certainly if I start flying a FIKI airplane. I'm enjoying reading and learning about this stuff, although there's a certain amount of as my brain attempts to digest and understand all of this info. Like with most subjects, it can be as complicated as you want to make it, and the more complex you make it the better understanding you have.

 

[flyingcheesehead]

I get the feeling that a pretty good number of pilots, including those who fly FIKI airplanes into ice, probably have a similar level of understanding. My feeling could be wrong, but it seems that this sort of information is not as commonly known as it ought to be.

Ted,

I think your feeling is absolutely right. And I'm sure I'm not the only pilot whose weakest and least favorite subject is weather!

 

[flyingcheesehead]

I think that most of the weather-related videos you can purchase or get online put me to sleep as well. They are often repetitive, drone on about common sense elements and don't spend any time talking about how to really identify what adverse weather looks like on a weather map.

Glad to hear I'm not the only one who goes during those parts.

The stuff I teach doesn't build on any foundation you might have. I build the foundation you need from scratch.

Aha. Well, sounds like I need to get into more of your stuff.

From me you'll learn how to identify the depth of the mixed layer. What's a mixed layer, you ask? And why do you need to know that? If you want to know where the thermal turbulence starts and stops and what altitude you'll need to stay above it, you'll want to know how to identify the depth of the mixed layer.

And that is EXACTLY what I need - The "why" and the "Why do I want to know." Otherwise...

 

[sba55]

I get the feeling that a pretty good number of pilots, including those who fly FIKI airplanes into ice, probably have a similar level of understanding.

I'd be very careful making that assumption, especially if you're basing it on your own lack of experience with weather. There certainly are those who fly advanced aircraft that don't know as much as they should.

In general, however, the knowledge gap is much less of a problem with advanced aircraft folks. If you read accident reports, you'll find that the vast majority of fatal accidents happens to people who fly non-FIKI planes into adverse conditions. We should be worried about that, not about how much we think others don't know either. You'd be surprised.

-Felix

 

[gismo]

IIf you read accident reports, you'll find that the vast majority of fatal accidents happens to people who fly non-FIKI planes into adverse conditions

Chances are the statistics on that will show that's because there are a lot more non-FIKI planes out there.

 

[jesse]

Chances are the statistics on that will show that's because there are a lot more non-FIKI planes out there.

..and one could say that the FIKI airplanes are exposed to the icing conditions more often making their risk higher than the non-FIKI..

Statistics will say whatever you want generally

 

[Ted]

I'd be very careful making that assumption, especially if you're basing it on your own lack of experience with weather. There certainly are those who fly advanced aircraft that don't know as much as they should.

In general, however, the knowledge gap is much less of a problem with advanced aircraft folks. If you read accident reports, you'll find that the vast majority of fatal accidents happens to people who fly non-FIKI planes into adverse conditions. We should be worried about that, not about how much we think others don't know either. You'd be surprised.

Of course there are going to be more fatal accidents involving non-FIKI planes into adverse conditions, because the FIKI planes are better equipped to handle those situations. Ice that could be fine in a FIKI plane could take a non-FIKI plane down, plus, as Lance pointed out, there are more non-FIKI aircraft out there. That doesn't give any indication to me that one group is or is not knowledgeable about weather, more just a statement of the obvious that if you put a plane not designed for particular conditions into those conditions, you will have problems.

I wasn't making a definite statement, just something that seems to be the case. The group that you mix with I'd bet would be among the more educated folks, but a number of pilots do seem to operate in a bubble education wise - I can think of a good number I know who do - and those are the ones you probably don't know.