Wind Shear @ Altitude

[Windchill]

When talking with FSS for a standard VFR wx brief before a cross-country flight, the briefer eluded to the possibility of wind shear at altitude do to the Winds Aloft. The region were the wind direction changed was well south of my route, but I kept it in the back of my mind anyhow.

It got me thinking ... would one notice since it's not like on final as you're throttling down close to idle? Would it amount to a small drop in airspeed, lower the nose and press on? Or potential pocket where you drop a hundred or two feet in half of a second?

My guess would be 1 or 2. Not really noticable with the thrust from the airplane keeping you going, or at worst 2, a small drop in airspeed and lower the nose (pretty much a practiced arrival stall, but at altitude).

 

[SteveC]

It is typically a turbulence issue in the area of the shear that is of interest to pilots.


[off-topic]Grammar mode on

When talking with FSS for a standard VFR wx brief before a cross-country flight, the briefer eluded (alluded) to the possibility of wind shear at altitude do (due) to the Winds Aloft. The region were (where) the wind direction changed was well south of my route, but I kept it in the back of my mind anyhow.

(Sorry, incorrect word usage is an old hot button of mine.)


.

 

[Windchill]

(Sorry, incorrect word usage is an old hot button of mine.)

Not a problem ... I am usually particular when it comes to that stuff ... and having completed higher education one and I should expect more from myself .... taking the time to proofread my own work has never been a strong suit.

Alluded ... I wasn't quite sure

"Due" and "Where" are just stupid mistakes I don't usually, and shouldn't make.

 

[typhoonpilot]

When talking with FSS for a standard VFR wx brief before a cross-country flight, the briefer eluded to the possibility of wind shear at altitude do to the Winds Aloft. The region were the wind direction changed was well south of my route, but I kept it in the back of my mind anyhow.

It got me thinking ... would one notice since it's not like on final as you're throttling down close to idle? Would it amount to a small drop in airspeed, lower the nose and press on? Or potential pocket where you drop a hundred or two feet in half of a second?

My guess would be 1 or 2. Not really noticable with the thrust from the airplane keeping you going, or at worst 2, a small drop in airspeed and lower the nose (pretty much a practiced arrival stall, but at altitude).

Windshear at altitude, better know as CAT ( Clear Air Turbulence ) can be quite nasty and has caused serious problems in the past. The worst areas are in the vicinity of very fast jetstreams, generally on the southern side of them. NWA is probably the best at forecasting and flight planning to avoid CAT in their Pacific routings. With jetstreams of over 200 knots over the Japanese islands and north Pacific, they need to be. In our route structure we have an area between Southern New Zealand and Australia that tends to be quite bad.

CAT over the Rockies is also well known. There it is more of a mountain wave type phenomenon. Airspeed excursions of over 20 to 30 knots are not uncommon and severe to extreme turbulence can be encountered. I once saw a DC-8 without a number four engine sitting on the Combs Gates ramp at Stapleton. They had lost it over the Rockies due to extreme turbulance.


Typhoonpilot

 

[Windchill]

I'm not sure if this is relevant or not ... but when I refer to "at altitude" (all things relative I suppose), I'm dealing with 5,500 feet in an aircraft with a TAS of 110kts and winds aloft changing direction with speeds of only 20-30kts as opposed to the wind speeds in the flight levels and aircraft speeds equivalent (sp?) to airliners. Would this lessen the effect?

 

[typhoonpilot]

I'm not sure if this is relevant or not ... but when I refer to "at altitude" (all things relative I suppose), I'm dealing with 5,500 feet in an aircraft with a TAS of 110kts and winds aloft changing direction with speeds of only 20-30kts as opposed to the wind speeds in the flight levels and aircraft speeds equivalent (sp?) to airliners. Would this lessen the effect?

It would. CAT is worse for airliners because the rate of change is higher due to higher speeds. Kind of like the difference between walking into a brick wall or running into a brick wall.

The one area you could get into a lot of trouble with mountain wave activity is on the lee side of the Rockies ( or any mountain range, for that matter ) where downdrafts can often times exceed the rate of climb of the aircraft you are flying.

TP

 

[FlyChicaga]

The worst turbulence I've ever experienced was between 3000-4000 feet descending on an approach. Definitely would classify it was severe turbulence. This was due to a strong temperature inversion coupled with a strong shear. Second most intense turbulence I've felt was flying up over Canada descending through FL310 to FL290. Borderline severe in severe clear. Winds went from westerly at 110 knots to northwesterly at 25 knots in 2000 feet.

I've seen moderate turbulence due to windshear at altitudes from 5000 feet to 37000 feet. Good idea to check tango airmets as well as upper-level wind charts from 850mb to 300mb, depending on your flight level.

http://adds.aviationweather.gov has some of these charts that I'm talking about, as well as graphical depictions of airmets and sigmets.

 

[Koen]

Turbulence

The worst areas are in the vicinity of very fast jetstreams, generally on the southern side of them.

Actually turbulence associated with the jet stream will be stronger on the northern (i.e cold air) side of the jetstream. Will be even stronger if significant cold air advection is expected.