21.   This cooling stabilizes the atmosphere, suppressing the rising currents of warm air needed to promote severe storms.

22.   Tornadoes form when rising currents of air tilt these horizontal rolls into spinning, vertical columns of air.

23.   Wednesday, rising currents of air over the Oregon Cascades generated a thunderstorm that spawned a small tornado near the town of Hood River.

24.   When the wind changes speed and direction as altitude increases, updrafts, the rapidly rising currents of air that sustain thunderstorms, can begin to rotate.

25.   With dramatic warming aloft, rising currents of moist air will be discouraged from ascending to high altitudes, limiting the growth of cumulus clouds and thereby suppressing thunderstorms.