The earth's seasons are caused by the tilt of the earth . More direct sunlight in the spring and summer causes warmer temperatures and the opposite occurs in winter. The Coriolis Effect does cause the jet stream to move from west to east. All 48 contiguous states have experienced tornadoes. Tornadoes most frequently occur in May .
Dry air is heavier .
So, the more water vapor, the lighter the air. In 1842 Christian Doppler discovered that the whistle of a train approaching a location had a higher-pitched frequency than the same whistle moving away from a location. Today's Doppler radar measures wind speed, distance, direction and speed of travel towards and away from a radar site. A 100 mph updraft is necessary to form a 3-inch diameter hailstone. The lowest barometric pressure in a hurricane occurs in the eye .