Question about windshear at 2000 feet

polaris

polaris

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polaris
23017G23KT P6SM SCT070 BKN200 WS020/23051KT

The weather is supposed to be clear and a million but this wind shear is in the TAF.

Winds aloft at 3000 feet is 28026KT.

I am surprised to see this, as there is no thunderstorms or anything in the forecast. A front is supposed to move in later. Never seen something this drastic before without a thunderstorm.

Is this an absolute no-go for a small plane? What happens to a small aircraft when you encounter a 25KT burst of wind going more or less the same direction at 2000 feet? And a sudden dying of the wind at 3000?

Is it still bad if I don't plan on staying at that altitude?
 
Probably just some turbulance. You should be fine, as long as it's not too close to the ground. The TAFs are MSL. How many feet AGL is this?
 
PPC1052 said:
Probably just some turbulance. You should be fine, as long as it's not too close to the ground. The TAFs are MSL. How many feet AGL is this?
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I thought TAFs were AGL??
 
polaris said:
I thought TAFs were AGL??
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You are correct, although with the tons of information available on the web "I thought" is a poor standard. Aviation Weather Services, in its discussion of low-level wind shear on page 7-27, emphasizes that the figure in the TAF is AGL.

You could look it up.

In any event, you are unlikely to notice anything more than a change in groundspeed if you have a GS display and are looking at it at the time.

Bob Gardner
 
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I've been in a 40kt sheer at about 3k' once just south of Chicago. The wind went from (roughly) south at about 15kts to from north at 20~25kts. The groundspeed change was neat, but honestly other than a few bumps it wasn't anything crazy. I went from tailwind to headwind. Was able to get the Cessna 152 to nearly a stand-still in slowflight.
 
polaris said:
23017G23KT P6SM SCT070 BKN200 WS020/23051KT

The weather is supposed to be clear and a million but this wind shear is in the TAF.

Winds aloft at 3000 feet is 28026KT.

I am surprised to see this, as there is no thunderstorms or anything in the forecast. A front is supposed to move in later. Never seen something this drastic before without a thunderstorm.

Is this an absolute no-go for a small plane? What happens to a small aircraft when you encounter a 25KT burst of wind going more or less the same direction at 2000 feet? And a sudden dying of the wind at 3000?

Is it still bad if I don't plan on staying at that altitude?
Click to expand...


I've flown in stuff like this before without a problem. Use caution at low altitudes, I approach with no flaps coming in hot and just flying it on.
 
Good to hear. Thanks. I didn't think it was a problem but one CFI told me, "I would never fly in that!" But I think he might have thought that the winds were gusting to 51 on the surface w/ a wind shear advisory.

Sounds like as long as I can handle the 23 gusts I will be fine.

Thanks guys!
 
Also I think the mistake was that the WS020/23051KT was misinterpreted as "winds variable from 020 to 230 at 51 Knots ... when it actually means 2000 feet AGL 230@51.
 
I've experienced a 50 kt difference between 2000' and 9500' -- 20 kt headwind to 30 kt tailwind. And I vaguely recall some years back a TAF mentioning a low-level wind shear of 50(?) kt on a clear morning in East Texas.
 
Wind shear isn't necessarily turbulent, but it can be.

But a 51 knot wind shear is N A S T Y. Unless that's a typo, it's a no go even if perfectly laminar and gentle. That's half your cruise speed and almost all of your approach speed. If that's really 15 knots, I wouldn't sweat it, as long as conditions on the ground are OK. I'd approach a little fast, though, as a 15 knot loss at minimum approach speed puts you right at stall in a 172. Wind shear isn't always reported on the ground, and I've had a 15 knot unreported lull in winds bite me before. It is NOT FUN at 50 AGL (stall warning, full power, bounce, go around from the bounce -- fortunately, no prop strike and no detectable damage except to my ego).

Given the conditions at altitude and the range of that wind shear, I don't think it's correct. You would need 70 knots on the ground to explain all that at once, and that's obviously a no-go (winds > stall speed means you can take off as soon as you're untied even with the engine off and no one in the aircraft). It makes a lot more sense if its 15 knots instead of 51.
 
MAKG1 said:
Wind shear isn't necessarily turbulent, but it can be.

But a 51 knot wind shear is N A S T Y.
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So this is where I am having trouble and I want to clear up before the flight.

WS020/28051KT means that the winds at 280 is at 51 knots, right? Not a 51-knot wind shear?

And if the winds on the surface is 25 knots in the same direction, I will see a 26 knot increase in ground speed as I enter 2000 feet? Therefore a 26 knot wind shear at 2000 feet?

"51 KT wind shear" makes it sound a whole lot worse.

Can someone please clarify?
 
polaris said:
So this is where I am having trouble and I want to clear up before the flight.

WS020/28051KT means that the winds at 280 is at 51 knots, right? Not a 51-knot wind shear?

And if the winds on the surface is 25 knots in the same direction, I will see a 26 knot increase in ground speed as I enter 2000 feet? Therefore a 26 knot wind shear at 2000 feet?

"51 KT wind shear" makes it sound a whole lot worse.

Can someone please clarify?
Click to expand...



Similar: WS010/18040KT - Low level wind shear at one thousand, wind one eight zero at four zero.


http://aviationweather.gov/static/help/taf-decode.php
 
polaris said:
So this is where I am having trouble and I want to clear up before the flight.

WS020/28051KT means that the winds at 280 is at 51 knots, right? Not a 51-knot wind shear?

And if the winds on the surface is 25 knots in the same direction, I will see a 26 knot increase in ground speed as I enter 2000 feet? Therefore a 26 knot wind shear at 2000 feet?

"51 KT wind shear" makes it sound a whole lot worse.

Can someone please clarify?
Click to expand...

Yes, you're right.

Though the direction of the wind correction depends on what direction you're flying.

It's still scary. 51 knots is still half your cruise speed, so fighting a headwind like that is going to take twice as long as it would otherwise.

This isn't impossible, but it sounds unusual, especially in clear weather. You have 26 knots at 3000, 51 at 2000 and something not enough to trigger a warning below 2000 (so it's still 51? That's not good). I'm not buying. I think someone transposed digits and it's really 15. But I wouldn't bet the farm on that without an independent verification somehow.
 
I ran into a 50knt headwind at about 3500 AGL running from Kentucky south to Tulahoma TN. Some small bumps but no real turbulence. The winds were hardly noticeable on the ground. Unless turbulence is forecast with the shear it may be a non issue. Except for the slow groundspeed.
 
Welp... the flight school grounded all flights for the night.

But that probably has more to do with the 60 degree crosswinds gusting to 25. They cited the wind shear levels dropping to 1500 feet as a reason, as well.
 
I've gotten up to 30 knot wind shear up to 3000. Calm winds on the ground, 30 knots at altitude. Smooth as a baby's bottom. It all depends on the temperature profile (i.e., stability). Even with terrain, you can get smooth transitions if the air damps out the mechanical turbulence.

That was a lllooonnnngggg cross-country. The return was real fast, but it doesn't cancel.
 
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