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To The Weather Watcher
Thunderstom Basics
What to watch for
Tornadoes and Funnel Clouds
Don't Get Fooled
What to Report
Index
Safety Tips
How to report
quick reference
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Severe Weather Watcher Handbook
Whether viewed at a distance or experienced overhead, the changes in a storm's intensity are some of the best clues to its severe potential. If you can interpret the system's present state and probable changes, you will be alert to the risks that may develop later. In most situations, your best viewing location is to the SE of the core, or just south of the storm's path, where the rain-free base is clearly visible and you are not at risk of being engulfed in precipitation.Storm features to check
Many distant storms will bypass your local area and be of no direct concern to you. So, why pay any attention to them? It's great practice! They provide a chance to test your knowledge, study features, and uncover clues that can be verified in severe events from other areas or in weather office records. Watching separate parts of a thunderstorm system can provide valuable insights for your assessment of its intensity and the probability of severe weather. (See What to Report for storm features MSC would appreciate hearing about.)
27 N/SE A
distant supercell with backsheared anvil and thick-edged, flat forward anvil.
Although there is no specific overshooting top, the anvil has a bulgy look suggesting
strong, persistent new growth. Hints of the flanking line are seen lower left
in towers leading up to the storm.
28 S/SE In this closer view, shaded towers on the short flanking line ascend to great heights, reach maturity (upper left), then push back to maintain a very high (18 km), large, backsheared anvil. The wall cloud is hidden by rain (lower left) where outflow has swept around the back of the core.
The anvil
The anvil can tell you everything about a storm - from age to strength and organization. A newly formed anvil will be short and thick-edged. The anvil on long-lived regenerating storms is very long, with small notches or dents along the edge corresponding to the separate pulses or updraft stages. If a storm is severe, the anvil will have a sharp edge (abrupt transition to clear sky), be smooth and high, and be flat on top. These are signs of a very powerful, steady updraft which has spread out at the tropopause (the stable layer at the top of the atmosphere) and blown forward on strong winds aloft. On the other hand, unevenness on top or along the edge indicates erratic growth or sporadic regeneration, suggesting a weaker system.
A storm's history is frozen into the anvil shape and structure. By comparing stages you can know the past and estimate the future. A new anvil section forming above an older one may indicate the onset of the severe phase, in which all aspects of the system are accelerated and magnified.
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