Flying through towering cumulus

[redbaron1982]

Hey, last weekend I did a short (1hr) XC from KSGR to KVCT just to keep getting used to my new M20J. I filed IFR as there were some clouds and didn't want to fly low. So I was cruising at 6000ft and going in and out of some towering cumulus. It was scattered so I had good general visibility while in between the clouds.

Turbulence was not bad, but at some point, I started feeling while in the clouds, that the aircraft IAS was increasing significantly, for instance from 140KIAS to 160KIAS. My theory is that updrafts inside the cloud made the autopilot pitch down to keep altitude and the speed increased. 

At some point I was not feeling comfortable anymore so I request an altitude change and start flying below the clouds. My main question is, how to tell from the outside how bad the up (or down) drafts are and to know if it is time to divert/change course.

Most likely what I experienced was not a big deal, I'm a relatively new IR pilot and this is one of my first flight solo in IMC.

[Danb]

RB it can get downright nasty in the towering cums, I now do the best I can to avoid them. A few good rides will humble you. Flying in the morning helps but by the time I generally get to my destination it’s hot large cums on a good day. My opinion be conservative there bigger stronger and more nasty than us. Just saying 

[Oscar Avalle]

I agree CB are not nice and never comfortable. Best thing to do is to ask to ask to deviate 

[redbaron1982]

32 minutes ago, 1980Mooney said:

Now I recognize that you said "towering cumulus".

• The “towering cumulus” tend to exist between 1000-6000 ft. They have less moisture than cumulonimbus, the air is less unstable, and convective activity is not present.
• However, nothing however prevents a “towering cumulus” from developing into Cumulonimbus. 

As a new IR pilot I would not trust my ability to distinguish between a towering cumulus and a Cumulonimbus.  Also weather data and FISB will lag - so you might decide to fly  into clouds that have developed into something worse than you thought.  Better to lose a few minutes and deviate.

They were not cumulonimbus for sure because there was no rain at the surface, the stormscope didn't show any lighting activity either.

The bases were at 3500ft and tops I guess around 8000ft. 

Edited June 16, 2023 by redbaron1982

[PT20J]

Years ago, I was flying with my wife from San Jose to Reno to visit friends. Out over San Juaquin Valley there were a few TCu up ahead and as soon as I deviated around them more formed farther up ahead. I kept trying to get around them and more kept popping up I finally diverted to Sacramento and soon after I landed there was thunder and lightning about. We spent the night and it thundered and lightninged all night long. Next day was beautiful. I was surprised how quickly some innocuous TCu's became Cb's.

Skip

[Pinecone]

You can also ask to deviate to stay out of them and weave between them.  Great fun flying.

[A64Pilot]

It was rising air, it’s sort of like Mountain wave turbulence, I ran into that over the Canadian Rockies, there you learn to let it carry you up however high it will, don’t turn it into airspeed, because the down draft is coming and if you only have 2,000 or so above the mountains it might get uncomfortable.

Stay out of the CB’s buried into the soft fluffy ones will be an ugly one.

[Hank]

12 minutes ago, A64Pilot said:

Stay out of the CB’s buried into the soft fluffy ones will be an ugly one.

Tru dat! My first IFR trip had my wife and I held at 7000msl across SC. Pretty smooth, and I could see all the way to the wingtips. Suddenly I was climbing 1500-2000 fpm, still smooth, still indicating cruise speed, ~143 mph. Center gave me a block,7-9, and I leveled off around 8800. Finally convinced center that I really wanted the 10k I had filed for, and that I was willing to take the deviation they gave as an excuse for holding me down.

At.10k, we were in sunshine, and the occasional buildup was easy to see and avoid. Easy lesson learned early.

[GeeBee]

Having the benefit of on board radar allows you to train your eye with regard to cumulus buildups. Generally I try to be above or below, but preferably above so you can observe any vertical development. Bad ones go up, not down except in the expended stage so above allows you to see the nasty.  If you look at it and you see active development, that is "boiling action", or expansion in both girth and height, you want to deviate. I'm not a fan of just punching through unless I am pretty dang sure what is on the other side so before I punch in, I ask myself, "What is on the other side" and is it building, diminishing or stable. If I don't have convective weather for a long ways (indicating an area of instability) and there is no building indicating instability, I punch through. Otherwise get out of the way. Remember the cumulus cloud at 6000' grew to 60,000 in height in less than 5 minutes and brought down Delta 191 at DFW, so have a good grip on the instability in the area you are flying.

[A64Pilot]

Way I see it, is if Scott Crossfield couldn’t fly through the things I have no chance

https://www.aopa.org/news-and-media/all-news/2007/september/27/ntsb-releases-final-report-on-crossfield-crash

Scott Crossfield is one of the ones I respect

A few of us are of the opinion that Center vectored him into it

[hais]

4 hours ago, redbaron1982 said:

Hey, last weekend I did a short (1hr) XC from KSGR to KVCT just to keep getting used to my new M20J. I filed IFR as there were some clouds and didn't want to fly low. So I was cruising at 6000ft and going in and out of some towering cumulus. It was scattered so I had good general visibility while in between the clouds.

Turbulence was not bad, but at some point, I started feeling while in the clouds, that the aircraft IAS was increasing significantly, for instance from 140KIAS to 160KIAS. My theory is that updrafts inside the cloud made the autopilot pitch down to keep altitude and the speed increased. 

At some point I was not feeling comfortable anymore so I request an altitude change and start flying below the clouds. My main question is, how to tell from the outside how bad the up (or down) drafts are and to know if it is time to divert/change course.

Most likely what I experienced was not a big deal, I'm a relatively new IR pilot and this is one of my first flight solo in IMC.

I recommend you watch EZWxBrief seminars. I started watching these because I had similar questions: I wanted to know what was safe.

Benign looking clouds could be dangerous. Before watching the series, I didn't have a good appreciation of the dangers. 

As a fresh PPL, I used to like to fly through rain shafts - now I know better. 

[201er]

3 hours ago, redbaron1982 said:

They were not cumulonimbus for sure because there was no rain at the surface, the stormscope didn't show any lighting activity either.

The bases were at 3500ft and tops I guess around 8000ft. 

That’s not towering cumulus. That’s just cumulus!

 

 

[Ragsf15e]

5 hours ago, redbaron1982 said:

Hey, last weekend I did a short (1hr) XC from KSGR to KVCT just to keep getting used to my new M20J. I filed IFR as there were some clouds and didn't want to fly low. So I was cruising at 6000ft and going in and out of some towering cumulus. It was scattered so I had good general visibility while in between the clouds.

Turbulence was not bad, but at some point, I started feeling while in the clouds, that the aircraft IAS was increasing significantly, for instance from 140KIAS to 160KIAS. My theory is that updrafts inside the cloud made the autopilot pitch down to keep altitude and the speed increased. 

At some point I was not feeling comfortable anymore so I request an altitude change and start flying below the clouds. My main question is, how to tell from the outside how bad the up (or down) drafts are and to know if it is time to divert/change course.

Most likely what I experienced was not a big deal, I'm a relatively new IR pilot and this is one of my first flight solo in IMC.

If your AP is in altitude hold, you will see updraft/downdraft as speed changes, so likely thats what you saw.  20kts is a pretty big one.  If you’re at 130kias, 110 feels downright mushy.

If you’re not in altitude hold and don’t change trim, the airplane will maintain constant airspeed (roughly) as it climbs/descends in the updraft/downdraft.

As others said, you’ll want to start avoiding these.  Up, down or around.  Whether  or not they are violent, you can’t see the worse “embedded” ones when you’re in there.  Much better to avoid them from clear air.  Typically any altitude above actual cloud height is smooth.  Below them is rougher (air is rising from below), to the side is at least as good as below, usually it’s pretty smooth, even close to them.

Chasing each other in formation around “big puffies” was great sport.  You could fly through the “valleys”, around the peaks, etc while trying to ditch your buddy and not hit the cloud.  No turbulence just outside the actual cloud most of the time.

[N201MKTurbo]

2 hours ago, A64Pilot said:

Way I see it, is if Scott Crossfield couldn’t fly through the things I have no chance

https://www.aopa.org/news-and-media/all-news/2007/september/27/ntsb-releases-final-report-on-crossfield-crash

Scott Crossfield is one of the ones I respect

A few of us are of the opinion that Center vectored him into it

I went to some aviation event in about ‘95 in downtown Phoenix. I had my 2 year old son on my shoulders. On the way in this old guy came up and started playing with my son. It was Scott Crossfield.

[ArtVandelay]

You said you didn’t want to fly low…6000 is low for me, 8000 is my minimum as a general rule, smoother, cooler and avoid the lower clouds.

[A64Pilot]

9 hours ago, N201MKTurbo said:

I went to some aviation event in about ‘95 in downtown Phoenix. I had my 2 year old son on my shoulders. On the way in this old guy came up and started playing with my son. It was Scott Crossfield.

If you read his history on why he became a test pilot it’s interesting.

I never got to meet most of the greats, but a friend and I made a precautionary landing at a field in Oberwinter Germany and Adolph Galland came out to look at the helicopter. That was the hope anyway because at that time you didn’t just get to go see him.

[A64Pilot]

7 hours ago, ArtVandelay said:

You said you didn’t want to fly low…6000 is low for me, 8000 is my minimum as a general rule, smoother, cooler and avoid the lower clouds.

Funny, for most of my trips now I fly at 1,000 ft, which is nose bleed territory for me.

I either fly low, or high, 7500 seems to be a sweet spot, the Maule it was between 10 and 12,000. 210 was about 7,500 too, which I think is about average for NA engines. Every design will have a sweet spot where lower eats more fuel and higher is slower, but short trips it doesn’t pay to climb to start an almost immediate descent when you get there.

One thing the Mooney does better than most is pick up speed in a gentle decent, most designs have so much drag they don’t pick up all that much, but if you leave cruise power in a Mooney and just trim for a few hundred feet a minute she picks up quite a lot of speed, you just start down much further out than you do with most aircraft

[Hank]

1 hour ago, A64Pilot said:

One thing the Mooney does better than most is pick up speed in a gentle decent, most designs have so much drag they don’t pick up all that much, but if you leave cruise power in a Mooney and just trim for a few hundred feet a minute she picks up quite a lot of speed, you just start down much further out than you do with most aircraft

I prefer 7500-10,000 if the trip is over an hour. For a 500fpm descent around here, from ~9000 msl, imstart down about 60nm out, and enjoy the extra speed.

[N201MKTurbo]

1 hour ago, A64Pilot said:

If you read his history on why he became a test pilot it’s interesting.

I never got to meet most of the greats, but a friend and I made a precautionary landing at a field in Oberwinter Germany and Adolph Galland came out to look at the helicopter. That was the hope anyway because at that time you didn’t just get to go see him.

Let’s see, I have shaken hands with; Chuck Yeager, Bob Hoover, Scott Crossfield,  Pete Conrad and the head pilot of the Tuskegee Airmen, but I Don’t remember his name. Mostly at Oshkosh.

[Mooneymite]

Towering CU can be quite benign down low, but once they build up through the freezing level....watch out.  That's when you can get some really bad conditions.

[A64Pilot]

3 hours ago, 1980Mooney said:

The OP's flight time was only about 25 minutes from leaving Class D at Sugar Land to a vector near Victoria towards the Localizer and IAF.  There wasn't a lot of time to be climbing and descending at 500 fpm.  Best to just stay reasonably low and below the Cumulus.

He did say if flight time is over an hour, and it was referencing a generalization, not the OP’s flight. I believe he was commenting on my statement of a sweet cruise spot

[201er]

The regular kind of cumulus clouds that top out at 6000, 8000, or even 10,000 feet are fairly benign. There may be some turbulence but virtually never any rain or substantial turbulence. There can be unexpected icing. But luckily most cumulus clouds tend to have gaps between them. 
 

You can fly around, through, between, above, or below regular cumulus clouds. Above is the most comfortable, followed by around, under, and least of all through. The turbulence can be enough to get your attention but shouldn’t ever be enough to cause a hazard. I prefer going through to going under because there tends to be plenty of VFR traffic below and a not so smooth ride.

Cumulus clouds reaching higher, like 10,000 to 14,000ft may be considered Towering Cumulus but are at the lower end of the type. You might get over these in a turbo, and I’m sure the ride above them is much better. In normally aspirated, you’re not getting above them. This leaves going through, around, or below. It may be a good smack going through, but again doable. I usually tighten up my belts and grab onto the center steel tube. Might get tossed around for a minute, but it won’t be long till you pop out the other side and go on your way. Make sure nothing is loose before going through one of these because it may not be where you placed it by the time you’re out.

And then there’s the real towering cumulus. The good old cumulus congestus. These extend to about 20,000ft which may be a challenge to cross even in a turbo. This is a bonafide junior cumulonimbus. It has many similar characteristics to a thunderstorm but with less severity. Updrafts, downdrafts, wind, rain, turbulence. What the large towering cumulus don’t have, as compared to a thunderstorm, is lightening. They may still show up on a storm scope but with significantly lower intensity than a thunderstorm.

Towering cumulus may show up on radar with light to moderate and at times heavy precipitation. It can be heavy enough to feel like going through a pressure washer. 
 

Going through large towering cumulus is possible but certainly uncomfortable. It’s the survivable version of flying through a thunderstorm.

The biggest hazard is that it could possibly grow into a thunderstorm as you’re going through it. I suppose every thunderstorm was a towering cumulus at some point as it grew. 

Towering cumulus can be distinguished from a thunderstorm by color, height, milder strikes on strike finder, and echo returns. Towering cumulus are usually white while thunderstorms are grey. Towering cumulus top out around 20,000 while thunderstorms continue higher. Towering cumulus may or may not appear on strike finder while thunderstorms do. Towering cumulus may return green, yellow, orange, even a bit of red on radar. Towering cumulus will be smaller in size on radar than thunderstorms but with similar shape. Thunderstorms are likely to have pronounced red and even purple areas on radar and likely a connective sigmet.

That’s a towering cumulus. Definitely not getting over it in a normally aspirated Mooney. I wouldn’t be eager to go through it. I’d try to get deviations around, but I would go through. However, if it extends above 20,000ft, shows significant lightning strikes, is dark in color, or is showing heavy+ precipitation on radar, UNABLE.

This information is for entertainment purposes only and should not be taken for meteorological or safety advice. Just my experience and a place to start your own gradual understanding of hazardous weather.

[Danb]

Great explanation Mike, nothing to add.

DB