A shear funnel is a type of weak, short-lived funnel cloud often observed in fair weather conditions. It's important to note these are not associated with severe thunderstorms.
Understanding Shear Funnels
Shear funnels, sometimes referred to as "high based" funnels, differentiate themselves from tornado-producing funnel clouds in several key ways:
- Weak and Ephemeral: They are typically small and do not last long.
- Associated with Small Cumulus Clouds: These funnels often form below small cumulus clouds, which are not the massive cumulonimbus clouds that produce tornadoes.
- "High Based": They are termed "high based" because the condensation level of the cloud is relatively high above the ground.
- Fair Weather: Shear funnels often occur in conditions generally regarded as "fair weather."
- Rooted Aloft: These funnels may even form from clouds whose bases are rooted aloft, meaning they are not directly connected to the surface boundary layer.
Comparison with Tornado Funnels
| Feature | Shear Funnel | Tornado Funnel |
|---|---|---|
| Strength | Weak | Strong |
| Lifespan | Short, ephemeral | Can be long-lasting |
| Cloud Type | Small cumulus | Large cumulonimbus |
| Weather Conditions | Fair weather | Severe thunderstorms |
| Connection to Ground | Often disconnected | Often connected to ground |
Example Scenarios
- Imagine seeing a small, wispy, funnel-like formation descending from the base of a puffy, white cumulus cloud on a calm, sunny afternoon - that could be a shear funnel.
- You might notice a brief, rotating column of air beneath a small cloud, but it quickly dissipates; this is consistent with a shear funnel.
Conclusion
Shear funnels are interesting atmospheric phenomena that highlight how rotation can sometimes occur even in non-severe weather. They differ significantly from the funnel clouds associated with tornadoes and are generally not a threat.
