Mountain IFR/Icing and Nexrad

[Alexb2000]

I fly a lot in NM and CO. The weather can be severe and unpredictable, so I try and do as much weather planning/updating as possible. I have noticed that Nexrad while good in most areas is not a good predictor of conditions in the mountains. Below are some pictures from my flight Monday from KSKX (Taos, NM) to KADS (Dallas-Addison). The first shows the MFD with only green and light snow. You would expect benign conditions and mostly clear. The second picture is in the middle of the green at 11K. It's hard to see, but its heavy frozen mist from the ground level up to about 13K where an overcast layer starts. Lastly, just south of the green near the Santa Fe airport. XM shows nothing, but you can clearly see an overcast layer.

What makes it interesting is that aircraft coming out of Santa Fe were reporting Moderate icing from 15K to 22K in an area on XM that shows clear. I have found in the winter in the mountains that XM is really not a very accurate way to predict adverse conditions. Neither is ground based (ASOS, AWOS) since they only report to 12K (below MEA's for much of the area).

Thoughts?

 

[Ted]

What makes it interesting is that aircraft coming out of Santa Fe were reporting Moderate icing from 15K to 22K in an area on XM that shows clear. I have found in the winter in the mountains that XM is really not a very accurate way to predict adverse conditions. Neither is ground based (ASOS, AWOS) since they only report to 12K (below MEA's for much of the area).

Thoughts?

I've found typically that clouds with no radar returns have more than enough ice in them. Radar returns can make it more interesting. A lot of times having the radar returns means the liquid is actually moving, and that seems to change things up significantly. My typical flow:

1) Am I in a cloud?
2) Is it below freezing?

If 1 and 2 are yes, then there's a possibility (albeit a high variability of how possible) that I'll pick up some ice. At that point, I look at things like temperature, PIREPs, where I am in the cloud layer, etc. to keep out of it.

 

[Everskyward]

I fly a lot in NM and CO. The weather can be severe and unpredictable, so I try and do as much weather planning/updating as possible. I have noticed that Nexrad while good in most areas is not a good predictor of conditions in the mountains. Below are some pictures from my flight Monday from KSKX (Taos, NM) to KADS (Dallas-Addison). The first shows the MFD with only green and light snow. You would expect benign conditions and mostly clear. The second picture is in the middle of the green at 11K. It's hard to see, but its heavy frozen mist from the ground level up to about 13K where an overcast layer starts. Lastly, just south of the green near the Santa Fe airport. XM shows nothing, but you can clearly see an overcast layer.

What makes it interesting is that aircraft coming out of Santa Fe were reporting Moderate icing from 15K to 22K in an area on XM that shows clear. I have found in the winter in the mountains that XM is really not a very accurate way to predict adverse conditions. Neither is ground based (ASOS, AWOS) since they only report to 12K (below MEA's for much of the area).

Thoughts?

Nexrad is based on radar and radar doesn't show clouds regardless of whether they contain icing or not. Radar reflects the best off water droplets (not mist) and less well off snow. Therefore you shouldn't be using Nexrad to determine the extent of cloud cover. This would go for the flatlands as well as the mountains.

 

[gismo]

Nexrad is based on radar and radar doesn't show clouds regardless of whether they contain icing or not. Radar reflects the best off water droplets (not mist) and less well off snow. Therefore you shouldn't be using Nexrad to determine the extent of cloud cover. This would go for the flatlands as well as the mountains.

Practically speaking you are correct but AFaIK in "Clear air mode" Nexrad can indeed see the moisture in some clouds. Normally none of that makes it through the filters in the mosaic geneators that feed our airborne displays.

 

[Alexb2000]

Nexrad is based on radar and radar doesn't show clouds regardless of whether they contain icing or not. Radar reflects the best off water droplets (not mist) and less well off snow. Therefore you shouldn't be using Nexrad to determine the extent of cloud cover. This would go for the flatlands as well as the mountains.

I guess I should have said clear of enough moisture to reflect on radar and especially enough moisture to produce moderate icing. What would you have used that could have better predicted icing in that area?

 

[Everskyward]

I guess I should have said clear of enough moisture to reflect on radar and especially enough moisture to produce moderate icing. What would you have used that could have better predicted icing in that area?

ADDS now has this tool.

http://aviationweather.gov/adds/icing/icing_nav.php?icg_type=CIPSEVO&height=max&fcst_hr=00

You could also look at these soundings. I'll confess that I'm just learning how to read these things but I'm sure someone will chime in.

http://rucsoundings.noaa.gov/gifs/

There are also PIREPS, of course.

The problem is that AFAIK there are no tools which can pinpoint the location of icing with that much accuracy.

I would be really wary about flying in IMC in areas of suspected icing in the mountains unless you are flying an airplane with FIKI which is at least turbocharged if not a turboprop.

 

[Alexb2000]

ADDS now has this tool.

http://aviationweather.gov/adds/icing/icing_nav.php?icg_type=CIPSEVO&height=max&fcst_hr=00

You could also look at these soundings. I'll confess that I'm just learning how to read these things but I'm sure someone will chime in.

http://rucsoundings.noaa.gov/gifs/

There are also PIREPS, of course.

The problem is that AFAIK there are no tools which can pinpoint the location of icing with that much accuracy.

I would be really wary about flying in IMC in areas of suspected icing in the mountains unless you are flying an airplane with FIKI which is at least turbocharged if not a turboprop.

I have used the aviation weather icing page, but never the second link. I would need some serious training to use that one. Also, away from the larger airports pireps are really rare (unfortunately).

I wouldn't fly 6 months out of the year if I let freezing temps and any possible icing stop me. So I just try to keep learning better ways to predict it and of course have outs if I get into some. In the pictures I am using my common SOP by staying at that altitude over the valley and not trying to climb above it. Even in the frozen mist I was able to avoid any icing and I was very close to an out if required (really not a challenging flight). I also only fly aircraft with some reasonable ice capabilities in the winter (turbo, o2, hot prop, etc.).

It seems to me that the air movement around the rocks creates much less predictability and moves clouds/moisture into areas you typically wouldn't find it. On the same trip going in over KAXX (Angel Fire) I picked up some trace at 16K (-16C) where it is usually to cold for ice. Of course Nexrad didn't help me there either.

 

[Everskyward]

It seems to me that the air movement around the rocks creates much less predictability and moves clouds/moisture into areas you typically wouldn't find it.

Here is a good article about icing. It's written for bigger airplanes but the concepts about what causes icing are the same.

http://www.aviationweek.com/aw/gene...=news/coldops1010p06.xml&headline=null&next=0

Moist air must be lifted and cooled below freezing while the droplets remain in liquid state to create the potential for icing. Super-cooled is the term meteorologists use to describe liquid water that is cooled below 0°C without freezing into ice.

The necessary lift is often found in mountainous areas.

 

[Ted]

It seems to me that the air movement around the rocks creates much less predictability and moves clouds/moisture into areas you typically wouldn't find it. On the same trip going in over KAXX (Angel Fire) I picked up some trace at 16K (-16C) where it is usually to cold for ice. Of course Nexrad didn't help me there either.

-16C isn't too cold for ice, and I frequently get it there (although usually not enough to write home about). Below -20C I usually figure I probably won't get any, but I think a graph Mari posted a few months back said that the 0% chance was down around -40C.

Most of the ice I get is in the range of -20C to 0C.

 

[ChrisS]

ADDS now has this tool.

http://aviationweather.gov/adds/icing/icing_nav.php?icg_type=CIPSEVO&height=max&fcst_hr=00

I use the ADDS Flight Path Tool FPT which shows Icing Level, Icing Severity and Icing SLD (supercooled large droplet), good free software.

 

[Alexb2000]

Here is a good article about icing. It's written for bigger airplanes but the concepts about what causes icing are the same.

http://www.aviationweek.com/aw/gene...=news/coldops1010p06.xml&headline=null&next=0

The necessary lift is often found in mountainous areas.

Thanks, I'll check it out.

Ted-

I haven't seen much in the area that I fly when it's -16C, certainly nothing to write home about as you said (still it does surprise me to see any). I'll do a search for that graph, sounds like something I need to look at.

Thanks.

 

[Everskyward]

Actually wet-coated hydrometeors such as wet snow, wet hail or wet ice pellets are excellent reflectors. With ice pellets and wet snow, you often get what is called a "bright band" when the radar hits these hydrometeors.

I guess my point was the radar needs something to reflect off of and normally clouds with no precip in them will not do the trick. If there are echoes there might be icing but the absence of echoes does not mean no icing as the OP seemed to think.

 

[Everskyward]

...which is not the case for wet snow. Dry snow, yes.

OK, I guess I'm just more familiar with dry snow out here. I've seen it snowing quite a bit without creating many echoes.

Plus if the OP is flying in NM, that's an area which tends to dry snow as well.

 

[Ted]

OK, I guess I'm just more familiar with dry snow out here. I've seen it snowing quite a bit without creating many echoes.

I've seen it here, too. We do get wet snow out here that will tend to produce some radar returns (albeit light).

But most of the ice I get ends up being in clouds with no radar returns, especially close to the tops.

To the OP: Curious, what plane are you flying? Thinking a T206 from your pictures or else T182, but you rmanifold pressure made me think T206.

 

[Alexb2000]

I've seen it here, too. We do get wet snow out here that will tend to produce some radar returns (albeit light).

But most of the ice I get ends up being in clouds with no radar returns, especially close to the tops.

To the OP: Curious, what plane are you flying? Thinking a T206 from your pictures or else T182, but you rmanifold pressure made me think T206.

Ted-

You are very observant, T206H. One of the few singles endorsed by OPEC.

 

[Ted]

Ted-

You are very observant, T206H. One of the few singles endorsed by OPEC.

Yeah, I know a few things about the TIO-540-AJ1A.

Fear not, I burn more fuel than you. Remember, iFlyTwins.

 

[Everskyward]

You are very observant, T206H. One of the few singles endorsed by OPEC.

That's cool. I have lots of time in the (much) older T206s. They are a great airplane for this area. I never would have believed back in the day that someday they would come equipped with Nexrad.

 

[Alexb2000]

That's cool. I have lots of time in the (much) older T206s. They are a great airplane for this area. I never would have believed back in the day that someday they would come equipped with Nexrad.

The G1000 in the 206 is kind of like heated leather seats in my pickup. I'm glad its there, but they always seems a little out of place.

 

[Ted]

The G1000 in the 206 is kind of like heated leather seats in my pickup. I'm glad its there, but they always seems a little out of place.

It's also the primary thing that Cessna has going for it to try to convince people to buy new airplanes, when you consider that the aircraft themselves are 50+ year old designs in many cases. I like your analogy of the heated leather seats in your pickup. The Cirrus you expect to have a shiny glass panel - it's what its Mercedes-driving owner expects. A Cessna driver is more likely to own a pickup, and the best pickups are beaten up.