creased wind speed in the jet stream.  The speed pulse moving across the Rockies will then develop into what we call a "shortwave". A shortwave  is a ripple in the jet stream that propagates along the jet stream. Air lifting out ahead of this shortwave can create low pressure beneath the air mass in the lower levels of the atmosphere.  This occurs as the wind field attempts to balance the Coriolis force.

The Coriolis force is created by the earth's spin on its axis,  with the centripetal force created by curved wind flow.  As low pressure develops on the surface it pulls cold air south behind it and draws warm air north ahead of it.  The sinking of the cold air behind the low in the trough, and the lift of the warm air ahead of the trough, both act to intensify the wave.  The developing wave in turn intensifies the surface low.  The surface low and upper level trough intensify each other until cold air sweeping down behind the surface low surrounds the

low and curtails the energy process.
Some of the biggest storms come when the northern branch of the jet stream can work together with the southern branch.  Sometimes, a shortwave propagating along in the northern branch will phase in with a wave propagating along in the southern branch, similar to a cog in a gear locking into the groove of another gear.  Phasing short waves can bring together cold arctic air from the north and moist subtropical air from the south to produce strong storms with heavy precipitation.

The jet stream becomes weaker during the warm season as temperatures across the north modify.  However, a weaker jet stream is also a slower jet stream.  This can allow storms to move more slowly across an area bringing prolonged rainfall.  Waves in the jet stream can also have a significant effect on thun

derstorms during the warm season.  Lifting air ahead of a shortwave can enhance thunderstorm development.  Even small and subtle shortwaves can have a major influence on the potential for thunderstorms in the late spring and summer.  A pocket of cold air aloft drifting over marginally unstable air can add just enough buoyancy to an airmass to trigger thunderstorms.

The jet stream provides the foundation from which most major weather systems develop and grow.  Jet stream winds both initiate and carry most weather systems, and ultimately structure the prevailing weather pattern.