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The Eagle

Air Turbulence Forecasting

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On a very recent trip in which my flight flew over Turkey moderate to severe turbulence was encountered (of which we were warned before hand). Unfortunately many passengers were frankly frightened by the experience and one or two in quite a distressful state. 

 

I think it's the ONE thing that terrifies nervous fliers. 

 

Just to note turbulence is NO threat to a modern aircraft whatsoever. It's uncomfortable and can be unnerving but at no time is the aircraft at risk. It's just a mixing of warm and cold air and though the plane may seem to drop a long way it's actually very exaggerated the way it is felt. 

 

Tip *Best place to sit on a long haul flight if you are wary of it is at the center of gravity which is over the wings.Posted Image

 

 

But it got me thinking about turbulence forecasting and it is advancing. Typically airliners depend on reports to ATC of turbulence from aircraft in a particular area - a warning is then relayed to other pilots. It's not forecasted as such yet.

 

See here http://www.turbulenceforecast.com/europe.php

 

 

Posted Image

 

 

Whether it provides reassurance or not i'm not sure but it's an area that is notoriously difficult to forecast and even above is experimental. But I think it's important none the less and hopefully more advances are made in this area.

 

Any thoughts?

Edited by The Eagle

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Severe turbulence, by definition, could be hazardous to modern aircraft. It is defined as turbulence which causes at least temporary loss of control of the aircraft. Aircraft that are involved in such an encounter must be checked for damage after landing.

There are many turbulence incidents reported monthly but in the majority of these it is passengers seated without seatbelts or crew who are injured. Nobody should be seated without their seatbelt fastened, but how many people actually listen to the preflight safety briefing? Too busy reading the Kindle to pay heed.

http://avherald.com/

There are good turbulence forecasts provided to pilots in the Sigwx charts fourtimes a day. Both CAT and Cb areas and levels are hightlighted.

http://brunnur.vedur.is/flugkort/PGDE14_EGRR_1200.PNG

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But it got me thinking about turbulence forecasting and it is advancing. Typically airliners depend on reports to ATC of turbulence from aircraft in a particular area - a warning is then relayed to other pilots. It's not forecasted as such yet.

 

 

Yeah, this is not entirely right. Turbulence forecasts have been issued for a long time. Along with turbulence SIGMETS (a warning of significant weather for aviation). Although of course forecasting of it is really tricky. You can use pattern recognition to identify areas which are known to be conducive for severe turbulence (vertical wind shear being one good example). Tricky thing about turb is that it's so deeply non-linear; turbulence happens at microscopic levels and can also work its way up to levels large enough to impact aviation. The microscopic stuff must be parameterised, it can't be forecast explicitly, so this introduces assumptions from an early stage. However, you can still use global models for it - with the Ellrod Index (a combination, IIRC of vertical and horizontal wind shears) being pretty common. That's for synoptic turbulence - low level turbulence (mechanical, convective) is different again. And then there's mountain waves....

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When I boarded a flight to Spain a couple of years ago captain came on half way through journey and warned us that aircrafts ahead were experience very bad turbulence and we was likely to be approaching it shortly.

 

Everyone aboard sat down and put safety belts on but we never came across any and rest of flight was smooth.

 

Must be very difficult to forecast and it must come and go very quickly.

Edited by Bradowl

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When I boarded a flight to Spain a couple of years ago captain came on half way through journey and warned us that aircrafts ahead were experience very bad turbulence and we was likely to be approaching it shortly.

 

Everyone aboard sat down and put safety belts on but we never came across any and rest of flight was smooth.

 

Must be very difficult to forecast and it must come and go very quickly.

 

 

In terms of aviation forecasting it always was and appears to continue to be the most difficult weather hazard to get right. During my time in avaiation forecasting Met and the aviation industry treid all manner of tests but nothing ever gave a model we could use with confidence.

As per the last post, aircraft could get severe clear air turbulence (CAT) those in front and behind would report next to nothing. Attempts with very fine temperature profile warners were one of the attempts but that never really worked well enough. No idea what is being done in the research area these days but it seems we are not much further on.

 

Predicting mountain wave activity oddly enough has always been much easier providing the forecaster is careful in their upper air analysis and in my day again there were very good and accurate empirical rules to apply, they gave about a 80 maybe 90% accuracy if forecasting for a specific area.

Edited by johnholmes

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I think the Lee waves are fairly easy to forecast, as a glider pilot I love them, but would say wave rotor is not very pleasant and sometimes bl##dy scary  but this tends to be found lower down. Toppling waves, I think these are the worst from my experience  (a glider is so small compared to a commercial jet so a jet may just fly straight through it?) I think it's when the top of a lee wave "topples" forward and breaks up creating serious rotor like turbulence, I had this happen whilst flying up in Scotland and can say it was the most frightening thing I think I've ever had to endure. How you would predict this type of event I don't know?

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I can't say I ever came across an example of that. Have you any links where I might read up on them please?

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I can't say I ever came across an example of that. Have you any links where I might read up on them please

 

 

 

John the only link I have is http://mwp.flightplanner.info/Beschreibengl.htm that shows a breaking wave. I do know that there was a lot of research done namely the Sierra Wave Project in the 50's and gather that a team of pilots have recently been assembled for another project starting next year (source Sailplane and Gliding)

 

I have heard it spoken about whilst gliding up in Scotland (Portmoak, Scottish Gliding Centre) the consensus seemed to be that the upward going parcel of air goes past the 90 degrees and as a result topples, then creates rotor like turbulence, this seemed to be born out by my variometers showing the climb rate in excess of 1,200ft/min I did see 1,400ft/min prior to the wave breaking up (this was at FL15 or circa 15,000ft) when normally on a good day we would see anything from 200ft/min up to 1,000ft/min in typical hotspots.

The turbulence was pretty horrific, airspeed going from zero, with the control stick limp in my hands to 80kts in a blink of an eye, I was glad I still had my straps done up tight or my head would have been through the canopy. It's pretty sobering when looking out at your long flappy wings and one is bent up 6-8ft while the other is bent down the same amount the other side. The wonders of Carbon fibre!! 

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thank you for that, I will have a look tomorrow.

The idea of being in that type of turbulence does not appeal one little bit, and yes the wonders of carbon fibre. Sitting in one of the latest aircraft in severe turbulence can be quite a sobering experience watching the wing on your side flex as it does. The only time I have been in a glider was about 1962 when a Canadian I worked with gave me a couple flights in one from Gt Hucklow, I always said I would get a lift again but never did. Too old for that sort of caper now.

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I used to fly United Airlines a lot when I lived in the US. They have a great feature where you can listen to the cockpit (although it was up to each individual captain whether they made it available or not). I remember being on a transatlantic flight one time and we hit moderate to severe turbulence over Newfoundland. I was expecting it as I was listening in. It was very interesting listening to the conversation between the captain and ATC as they tried to find an altitude where the turbulence was less severe. All they had to go on was reports from other aeroplanes. The upshot was that turbulence was reported at all altitudes and the captain settled on 29000 feet as it seemed the smoothest.

The worst I ever experienced was on a flight from New York to Chicago in late Autumn one year. There was a powerful cold front sweeping in from the Ohio area towards the East Coast (they get some very powerful fronts over there of course!), and about twenty minutes after take off the order came from the cockpit for all crew members to take their seats. That was it for the rest of the flight! As I recall, we ended up flying at an altitude of 19000 feet for most of the journey which is very low for a cruising altitude. It's amazing to think just how much is going on up there in the atmosphere that we do not see down here!

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thanks for that insight WF. I have to admit I always preferred to be in the jump seat, that shows my age, flying and be able to see and listen directly to what was happening. I was very priveleged I suppose to be able to do that with being a forecaster at a number of UK airports and getting to know pilots from a good many airlines who were more than happy it seemed to let me do this even years after that part of my career came to an end.

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Hi,

I fly for a well known large Orange and White UK based airline, we have a very good briefing system (lido) which includes a vast amount of weather related info ( even able to speak to a lovely met person on the phone ) As regards CAT, we have a shear rate level on our 1st briefing page. I believe this came from research done by Singapore Airlines... I maybe wrong on that one... It's pretty useful for a general guide and most of the time accurate but from my experience it's always going to be difficult/impossible to predict with any certainty CAT..

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thanks for that kp, is it possible to post a copy of that shear rate chart you mention, or perhasp send it via pm to me please? I would be very interested to see how it is presented? I assume it is part of the Sig Wx chart issues from UK Met, used to be London (Heathrow) now from Exeter.

 

thanks

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thanks for that kp, is it possible to post a copy of that shear rate chart you mention, or perhasp send it via pm to me please? I would be very interested to see how it is presented? I assume it is part of the Sig Wx chart issues from UK Met, used to be London (Heathrow) now from Exeter. thanks

Not a problem John, will send it over.. Easier to see how it's presented than for me to explain..You will also see the wind direction and wind speed at different waypoints ( as you know) can't get over how accurate these are! Within a degree/knot or two compared to what we actually get up there. Absolutely phenomenal! Clever lot at Exeter!

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Not a problem John, will send it over.. Easier to see how it's presented than for me to explain..You will also see the wind direction and wind speed at different waypoints ( as you know) can't get over how accurate these are! Within a degree/knot or two compared to what we actually get up there. Absolutely phenomenal!Clever lot at Exeter!

 

 

many thanks for that-upper air forecasting has always been the easier compared to what happens at ground level. 24 hour predictions are also much easier than longer term but good to hear you are so satisfied with the products.

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Hi John, as promised.. Sorry not great photos! You should be able to just make out SR ( Shear Rate ), goes with the info from Exeter..

Regards

Paul

post-7736-0-56806900-1389177223_thumb.jppost-7736-0-51533200-1389177252_thumb.jppost-7736-0-07129300-1389177265_thumb.jp

Edited by bluekipper

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Hi John, as promised.. Sorry not great photos! You should be able to just make out SR ( Shear Rate ), goes with the info from Exeter..

Regards

Paul

Posted Imageimage.jpgPosted Imageimage.jpgPosted Imageimage.jpg

 

 

thanks Paul I will download them and put them the right way up and see what they show-thanks for doing this

 

regards

 

John

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