# Key Takeaways - Wind shear is a change in wind speed and/or direction over a short distance. - Four common sources of low-level wind shear are— 1. [[Wind Shear Along Front.jpeg|Frontal activity]] 2. [[Thunderstorm Up and Downdrafts.jpeg|Thunderstorms]] 3. [[Wind Shear from Tempurature Inversion.jpeg|Temperature inversions]] 4. Surface obstructions - Best ways a pilot can prevent a hazardous encounter with wind shear: - Know wind shear is there. (How?) - Know the magnitude of the change. - Be prepared to correct or go around immediately. - Always be alert to the possibility of wind shear, especially when flying in and around thunderstorms and frontal systems. # Details #todo :: add sources to know about wind shear Wind shear can occur either horizontally or vertically and is most often associated with strong temperature inversions or density gradients. While wind shear can occur at any altitude, low-level wind shear is especially hazardous due to the proximity of an aircraft to the ground. ![[Strong Wind Shear At Low Altitude.jpeg]] Low-level wind shear is commonly associated with passing frontal systems, thunderstorms, temperature inversions, and strong upper level winds (greater than 25 knots). ## Microbursts Microbursts are a very severe form of [[LLWS]]. > [!caution] From [[AIM 7]] > They may be embedded in heavy rain associated with a thunderstorm or in light rain in benign appearing [[virga]]. When there is little or no precipitation at the surface accompanying the microburst, a ring of blowing dust may be the only visual clue of its existence. A typical microburst: - Has a horizontal diameter of 1–2 miles and a nominal depth of 1,000 feet. - Lasts about 5–15 minutes during - Can produce downdrafts of up to 6,000 feet per minute (fpm) and headwind losses of 30–90 knots ![[Effect of Microburst.svg]] > <a href="https://www.weather.gov/bmx/outreach_microbursts"><img alt="Microburst Animation" src="https://www.weather.gov/images/bmx/Daily/microbursts/animation.gif"></a> > <a href="https://www.weather.gov/bmx/outreach_microbursts">Microbursts</a>, <a href="https://www.weather.gov/disclaimert">Public Domain</a>, via [[NWS]] Birmingham, Alabama # Additional Resources - [[FAA P-8740-40 Wind Shear]] - [[AC 00-54]] - [[PHAK Ch12]] - [[AIM 7]] - [Delta 191](https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_191) ## FAA Definition ***Definition*** :: Wind shear is a sudden, drastic change in wind speed and/or direction over a very small area. ***Source*** :: [[PHAK Ch12]] #glossary #concept