# Key Takeaways - Too tall to fly over, too dangerous to fly through or under, and can be difficult to circumnavigate - Penetration of any thunderstorm **can lead to an aircraft accident and fatalities** to those on board - Never regard any thunderstorm lightly, even when radar echoes are of light intensity. Avoiding thunderstorms is the best policy. # Details ## 3 Ingredients ![[Thunderstorm Ingredients.jpeg]] ### 1) Moisture Potentially from a body of water or a particular air mass ### 2) Instability See [[Atmospheric Stability]] ### 3) Lifting Action 1. **Orographic effects**: Winds blowing across mountains and valleys cause the moving air to alternately ascend and descend 2. **Low pressure system**: winds converge into surface low pressure, causing the air to rise, expand, and cool^[The [[Aviation Weather Handbook]] calls this "frictional effects".] 3. **[[Front|Frontal lift]]**: occurs when the cold, denser air wedges under the warm, less dense air, plowing it upward, and/or the warmer air rides up and over the colder air in a process called overrunning. 4. **Buoyancy**: Air near the ground can warm at different rates depending on the insular properties of the ground with which it is in contact. 1. A newly plowed field will warm faster than an adjacent lake. 2. The denser cool air will tend to push (i.e., lift) the less dense warm air aloft. ## Life Cycle ![[Thunderstorm Life Cycle.jpeg]] ## Hazards > [!danger] From [[Aviation Weather Handbook]] > Hazards include low ceiling and visibility, lightning, adverse winds, downbursts, turbulence, [[Ice Hazards and Aircraft Icing|icing]], hail, rapid altimeter changes, static electricity, tornadoes, and engine water ingestion. > [!warning] While not every thunderstorm contains all hazards, it is not possible to visually determine which hazards a thunderstorm contains. ![[Thunderstorm Up and Downdrafts.jpeg]] [[Wind Shear]] and [[Wind Shear#Microbursts]] ## Avoidance ### Safe Distances > [!quote] [[AIM 7]]-1-29 > avoid by at least 20 miles any thunderstorm identified as severe or giving an intense radar echo. This is especially true under the anvil of a large cumulonimbus.^[Although anything closer than ~40nm can result in serious winds and turbulence] ![[Thunderstorm from 37,000 feet.jpeg]] ^image ### Forecasting #todo :: add more info [[Convective SIGMET]]s will be issued for expected thunderstorms See also [[Thunderstorm Alerts in Forecast Before Lightning Strikes]] ### In Flight - Consider diverting and waiting out the storm - May be appropriate to ask for a hangar if hail is expected - Go around the storm using radar for large scale planning - Never try to use radar to navigate between storm cells (link) > [!youtube]- Published by [[Air Safety Institute]] >  ## If Unable to Avoid > [!quote]- From [[Aviation Weather Handbook]] > If unable to avoid penetrating a thunderstorm, the following is guidance for before entering the storm: > 1. Tighten the safety belt, put on the shoulder harness (if installed), and secure all loose objects. > 2. Plan and hold the course to take the aircraft through the storm in a minimum time. > 3. To avoid the most critical [[Ice Hazards and Aircraft Icing|icing]], establish a penetration altitude below the freezing level or above the level of -15 °C. > 4. Verify that pitot heat is on and turn on carburetor heat or jet engine anti-ice. Icing can be rapid at any altitude and cause almost instantaneous power failure and/or loss of airspeed indication. > 5. Establish power settings for turbulence penetration airspeed recommended in the aircraft manual. > 6. Turn up cockpit lights to highest intensity to lessen temporary blindness from lightning. > 7. If using [[Autopilot Systems and Usage|automatic pilot]], disengage Altitude Hold Mode and Speed Hold Mode. The automatic altitude and speed controls will increase maneuvers of the aircraft; thus, increasing structural stress. > 8. If using airborne [[radar]], tilt the antenna up and down occasionally. This will permit the detection of other thunderstorm activity at altitudes other than the one being flown. > 9. Keep eyes on the flight instruments. Looking outside the cockpit can increase danger of temporary blindness from lightning. > 10. Do not change power settings; maintain settings for the recommended turbulence penetration airspeed. > 11. Maintain constant attitude. Allow the altitude and airspeed to fluctuate. > 12. Do not turn back once in the thunderstorm. A straight course through the storm most likely will get the aircraft out of the hazards most quickly. In addition, turning maneuvers increase stress on the aircraft. # Additional Resources - [[Aviation Weather Handbook]] - [Thunderstorm Ingredients](https://www.weather.gov/source/zhu/ZHU_Training_Page/thunderstorm_stuff/Thunderstorms/thunderstorms.htm) ***Definition*** :: a local storm, invariably produced by a cumulonimbus (CB) cloud, and always accompanied by lightning and thunder, usually with strong gusts of wind, heavy rain, and sometimes hail. ***Source*** :: [[Aviation Weather Handbook]] #glossary #concept