The 300 mb chart investigates the upper portion of the troposphere where most of the weather producing phenomena occur. This level lies around 30,000 feet up and is often referred to as the jet stream level. Areas of strong winds at this level (winds > 100 knots or 115 mph), commonly referred to as jets, indicate areas of high atmospheric energy. These are created by strong temperature contrasts in the lower and middle tropopause and reflect areas of potential storm development. A strong jet (winds > 130 knots) can indicate the potential for the development of a strong low pressure system especially when if moves over the Rocky mountains and into the Plains states. A strong jet hitting the west coast can indicate the existence of a strong precipitation producing system.