United States, Canada, and Adjacent Oceans (Theory)

The U.S. and CanadaCanada stretch across a wide range of latitudes and climatic types. The multiple north–south-oriented mountain ranges in the West and lower mountains in the East provide opportunities for orographic precipitation, double rain shadowDouble rain shadow effects, and interaction of strikingly different air masses that produce severe mid-latitude weather, including tornadoes andSupercell supercell andMulticell thunderstorm multicell thunderstormsthunderstorms. The mid-latitude westerliesWindmid-latitude westerlies, with their embedded Rossby wave ridges and troughs and theJet streamAfrican easterlypolar front polar front jet stream, provide the steering circulationsteering circulation, influence on for much of the region. The Bermuda-Azores High drives theGyreNorth Atlantic North Atlantic Gyre, with the Gulf Streamand Gulf Stream and spin-off Loop Current forming its western edge. The Bermuda-Azores HighAzores High brings maritime tropicalmaritime tropical air masses to the U.S. east of theMountainsRocky Rocky MountainsRocky Mountains and to southeastern CanadaCanada. Preferred mid-latitude wave cyclone trackstracks in North America include the leeward side of the Rocky MountainsFront (weather)and baroclinic zones and baroclinic zonesBaroclinic zone associated with winter land-sea temperatureTemperatureand baroclinic zones differences in the northern Gulf of MexicoHumidityand Africaand Gulf of Mexico and near the North CarolinaNorth Carolina coast. Ocean–atmosphereAtmosphere teleconnections including theTeleconnectionArctic OscillationPacific-North American pattern Pacific-North American patternTemperatureand Pacific-North American pattern are important causes of atmospheric variability invariability in position this region affected so strongly by both continentalityContinentality and maritime influence.