Upper Level Storm Clues - Best seen 30 to 40 miles from storm. Overshooting Top - domelike bubble of cloud material extending above the anvil and persisting for > 10 minutes. Think in terms of the updraft of the storm, that is movement in the vertical. The magnitude of the updraft is a signal of storm strength. As the Jet Stream moves along from generally west to east, the updraft, if strong enough punches a hole through the jet stream and an overshooting top results. Anvil Characteristics - thick, cumuliform anvil with sharp well defined edges. This is another clue of storm strength. The stronger the updraft, the better defined the anvil will be.