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LONDON FIR last night mountain waves

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LONDON FIR last night mountain waves

Old 14th Nov 2006, 10:13
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LONDON FIR last night mountain waves

Out of curiousity there were reports of Severe Mountain Waves in the London area last night. I know that there were some strong high & medium level winds last night. This is the first time that I have ever heard such a report.
My limited understanding is that this type of activity is usually associated with unstable air and severe turbulence?

Anyone out there get caught up in this last night?

Also a layman's explination of this condition would be welcomed.
With thanks.
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Old 14th Nov 2006, 11:30
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Was not there to comment on last night.

Theory: STABLE air mass. Can cause difficulties in maintaining height or speed if severe, but I have never had 'severe turbulence' in them. Stable air allows the 'upswell' effect of the mountains to set up a 'wave' effect which can exist hundereds of miles downwind.
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Old 14th Nov 2006, 12:42
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It's as above - last year I climbed out on a glider to about three & a half k ato in the rising part of mountian wave in a north westerly just infront of Devils Dyke by Brighton. The rough bits are horrid I understand & enough so to down aircraft. IIRC, the 737 crash at Colorado Springs had mountain wave as one theory amongst others.
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Old 14th Nov 2006, 13:15
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On the tube home at about 4pm yesterday I was looking at a long circular cloud (looked a bit like rolled pastry) running E-W from horizon to horizon passing south of London. Would have been over Fairoaks - Redhill - Biggin. I wondered what was causing it. Now I know.
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Old 14th Nov 2006, 14:07
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All, thanks for your responses. I didnt see the "pastry" cloud HOLYFLYER but it would have been interesting to see that one!
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Old 14th Nov 2006, 15:53
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One of the most famous 'wave bars' in the free flying community...


Hang-gliders ge towed up to this behind microlights...just for a laugh!!!
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Old 14th Nov 2006, 17:22
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I was once told that wave generated in Wales could sometimes be found as far east as London.
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Old 14th Nov 2006, 18:35
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dear ppruners

I have never been to the UK, but I live and have flown the sierra in California/Nevada USA.

Quite frankly I didn't even know the UK had mountains to speak of.

Mt. Whitney is the tallest peak in the 48 US states ( alaska has much higer) with elevation over 14,000 feet, part of the sierra range.

There have been reports of effects of mountain wave off the Rockies some 700 miles downwind.

Rotor clouds may form that can ruin your whole day.

Turbulence is almost not enough of a word for what one might encounter with mountain wave...indeed once encountered a quick call to ATC that we will be off our altitude riding the waves is not unheard of

I live in Reno, NV and we get Lenticular couds ( shapped like flying saucers) which can warn pilots of mountain wave.

Updrafts can be huge as can downdrafts....I lost 3000 feet in a light prop twin early on in my career encountering wave on a lesser range in california.

High winds over the mountains can be vectored UP upon hitting the mountains and then on the lee side can come down...ouch.

Mountain flying is a different animal and in planes capable of only lower altitudes one should approach the mountain at a 45 degree angle to allow an easy retreat if things are going badly.

One should clear the mountain by at least 1/2 of the height of the mountain...14,000 mountain, you should clear by 7000 feet meaning FL210...much above small planes ceilings.

Flying Jets into Reno (KRNO) may require you to stay high till over the mountains and then drop your gear very early in order to get down...we have more go arounds then many other airports in the US.

Similiar stuff for Denver and other mountain area airports.

For jets, fly at rough air penetration speed, ignition on, flight attendents strapped in....if too high and on autothrottles in cruise, they may hunt and you will get very close to overspeed (coffin corner) and drop to very close to stall within seconds. and plenty of room above mountains.

my airline had a CAT encounter some 500miles from the rockies and it was blamed on mountain wave.

And to BOAC I think...mountain wave was part of the thinking about that colorado springs crash 737...but I think the rudder bit was really to blame
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Old 14th Nov 2006, 19:52
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The 1966 BOAC B707 -436 G-APFE Mount Fuji crash was associated with severe turbulence caused by a mountain wave.
I have also had severe turbulence over the Pyrenees, no lenticular nor rotors evident..and certainly no MTW SIG WX activity on the charts..just a sudden jolt then all hell brakes loose..14 pax's injured ...I have looked into my incident in great detail and have the upmost respect for the enviroment we work in.
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Old 15th Nov 2006, 08:18
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Ah Mr Turin, the famous morning glory. One understands that it shows up two or three times a year & is indeed a must do for hang glider pilots. Unfortunately, us PG pilots are just too slow & ponderous to do get involved & would indeed end up with the very thin end of the wedge.
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Old 15th Nov 2006, 08:45
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The main effect of the standing waves on public transport a/c is that transiting from the rising air to the sinking air will lead to the auto thrust increasing and decreasing power (very noticeable over the Alps with a strong northerly). Also if the wave bar were to be aligned with the approach it would either require more power if on the "down side" or lead to difficulty slowing down if you were on the "up" side. A few weeks ago there was a classic southerly wave bar on the approach to EDI 06 and the bar was aligned with the approach making it hard to slow down and go down. If one were a bit high and fast in that situation it could lead to a go around, so when mountain waves are forecast it is worth monitoring your climb, descent and deceleration profile more closely and being prepared to drop gear earlier and/or use speed brake.
Standing wave is particularly common where there is high ground but is regularly noticed by the more observant pilots over the flat lands too.
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Old 15th Nov 2006, 09:03
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Come to Bonnie Scotland, we regularly fly in wave in our gliders. Any half decent hill or mountain range should kick off some good wave. Some of the best lift here can be found to the north of the grampians(just south of Inverness) with a southerly wind. At our club near Elgin we're up at 10 - 20k feet every other week. Some great cross countries around Scotland (300 - 500 kilometers) can be had if the wave is good. The UK altitude record for a glider stands at 38,0000 feet, set by a glider from Aboyne, just to the east of the Cairngorms. Flying in wave is beautifuly smooth, provided you are on the leading edge side of the bar, where the air is rising. The turbulence is found to the trailing edge, where the air is sinking and mixing with the unstable air below. Flying in wave is not dangerous, provided you know what your doing.

I believe Steve Fossett recently climbed to nearly 60,000 feet in wave, somewhere over Argentina and broke the absolute altitude record for a glider.
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Old 15th Nov 2006, 12:33
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Unfortunately, there are too many days when this phenomenon is forecast over the London FIR without geographocal limits or regard to the real meteorological criteria for required their formation. The best wave (and worst turbulence - generally as a result of rotor cloud and found near the surface) is to the east of the Breacon Beacons, Snowdonia, Pennines, Cairngorms etc. In the UK, wave system may usefully extend (from a glider pilots point of view) up to 60 miles (and maybe more) downwind of the obstacles forming with the wave. However the turbulence associated is normally left behind after the first or second bar - within 10 miles of the obstacles and is rarely encounted much above 3,000'. The real problems for the bigger stuff are the vertical components of the wave (up to 1,000 fpm in the "best" bits) and it's fair to forecast these, but also the "real" location. Also, we should challenge the Met. man's concept of "Severe" - Mild might be a better term for the UK. As for being in a bigger aircraft, I have happily gone wave riding in a F100 and used wave to climb in an F27 but nothing quite beats cross-country soaring in a glider. That is a joy I have to thank a guy called John Jeffries (from the LGC) for.
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Old 17th Nov 2006, 10:21
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Ahhh my handle.. MorningGlory... Seen it a few times from the pointy end was impressed hence..
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