Jet stream
a long but narrow corridor of extremely strong winds near the top of the troposphere that encircle the globe
Jet Stream Characteristics
Length: 1000-3000 mi (1600-4800 km)
Width: 200-300 mi (300-500 km)
Depth: 1-3 mi (2-5 km)
Typical wind speeds range from 55-250 mph (55 minimum)
Jet Streams form
high above the separations between warm and cold air masses
Separations most consistently pronounced at the Horse Latitudes and Polar Fronts
line up with the greatest surface temperature contrast
Location of the two primary jets
Polar jet stream: above 60 °N and S
Subtropical jet stream: above 30 °N and S
Jet stream speeds are strongest
where the surface temperature gradients are the greatest
Jet stream and pressure centers
The winds in the jet stream converge above high pressure centers by slowing down
Air builds up (converges) and must go somewhere. Air sinks down!
The winds in the jet stream diverge above low pressure centers by speeding up
Air evacuates (diverges) and must be replaced from below. Air rises up!
Northerly and northwesterly surface winds
advect cold, dry cP air southward from Canada
Westerly and southwesterly surface winds
advect warm, dry cT air from the Rocky Mountains, Desert Southwest, and Mexico
Southerly and southeasterly surface winds
advect warm, moist mT air northward from the Gulf of Mexico
Easterly Winds
are rare due to the Appalachians
