How is clear air turbulence forecast??...

[UALdave]

You get this a lot, from air coming off of the mountains, here in Denver. But I wonder how it's forecast? AFIK, pilots can't see it on radar. Flying over the mountains, it would just be nice to know that pilots expected the turbulence in advance.

[Peter Kesternich]

As far as I know you can't predict or forecast CAT. You can only assume from certain conditions that it may exist. Hence "Keep your seat belt fastened while seated in case we encounter some unexpected turbulence."

[Gabriel]

That, and PIREP's.

[3WE]

I'm thinking theres lots of good ways to forecast CAT.

Things are usually rough around the jetstream- and it's tracked very well.

Winds are forecast by altitude and at some point if there's too much gradient/speed or directional shear, one might expect turbulence even in clear conditions.

Plus, over the years- conditions when CAT occurs have been catalogued- so that when those conditions repeat; one could reasonably expect turbulence to occur.

Of course, throw all of it into a mega-ass computer model and bring on forecasts for all sorts of stuff!

[3WE]

Originally Posted by UALdave

You get this a lot, from air coming off of the mountains, here in Denver.

Should have read slower.....

A great way to forecast CAT in Denver at the base of the mountains is if the wind is blowing and it's not cloudy, then you will have CAT......

(and meteorologists can forecast when it will be windy...)

[UALdave]

Originally Posted by 3WE

Should have read slower.....

A great way to forecast CAT in Denver at the base of the mountains is if the wind is blowing and it's not cloudy, then you will have CAT......

(and meteorologists can forecast when it will be windy...)

True! What about the effect heat has on CAT? The bumpiest ride I've ever had on an airplane was on a United 737-300 taking off from KLAS in July. People always ask when the turbulence started, and my answer is always the same-immediately after takeoff. I've been told that thermals were the cause.

People I know say that they don't want to fly on a smaller commercial plane, like a CRJ, because they say they'll feel the bumps more when there's turbulence. Like a smaller boat in big waves, the argument goes.

[Gabriel]

Originally Posted by UALdave

People I know say that they don't want to fly on a smaller commercial plane, like a CRJ, because they say they'll feel the bumps more when there's turbulence. Like a smaller boat in big waves, the argument goes.

Yet, my second worst turbulence was in a 747 (the worst one was in an F-27).

[Highkeas]

Originally Posted by UALdave

............ it would just be nice to know that pilots expected the turbulence in advance.

Pilots are updated based on observations from preceding flights on the same route.

[Highkeas]

Originally Posted by Peter Kesternich

.................. Hence "Keep your seat belt fastened while seated in case we encounter some unexpected turbulence."

During the USA election season I constantly see media images of candidates standing in the aisle surounded by reporters. I would not be surprised if a candidates aircraft hits turbulance and a bunch of people are carted of to hospital.

[Peter Kesternich]

Originally Posted by UALdave

True! What about the effect heat has on CAT? The bumpiest ride I've ever had on an airplane was on a United 737-300 taking off from KLAS in July. People always ask when the turbulence started, and my answer is always the same-immediately after takeoff. I've been told that thermals were the cause.
(...)

Well, there is turbulence and turbulence. I think, thermal turbulence would be easy to forecast: it's sunny and hot, there you go. Then there is precipitation-related turbulence, what you experience in clouds and during thunderstorms. But actually, this thread is about Clear Air Turbulence, and that is again a different matter. If I remember this correctly, true CAT is caused at high altitudes when different air currents meet and this is still something different from the terrain-induced turbulence you can encounter in the vicinity of mountains.

[3WE]

Originally Posted by UALdave

...it would just be nice to know that pilots expected the turbulence in advance.

1) There are numerous aviation weather resources at www.internet.com, including turbulence forecasts.

2) Of course, all weather forecasts have an error rate.

3) Weather, including turbulence, is often localized- so in spite of it being forecast- AND PRESENT- you might fly through it (and you have a bumpy ride) or around it (and you have a smooth flight)- and some of this may be do to luck of your assigned altitude, or the luck of someone else giving a pirep ahead of time.

4) There is a certain liability aspect- so forecasts may tend to over-predict turbulence to avoid surprises to flight crews.

5) I recall hearing a SIGMET for moderate to severe turbulence (on a 'police' scanner) before a turboprop flight...the result was some enthusiastic bumps on short final- where I felt absolutley NOTHING on departure in a DC-9. (Big planes do respond less)

6) Good luck.