Rivers in the Sky are Flooding the Northwest: Impacts of the Pineapple Express

Major flood risk,in the Pacific Northwest, typically increases with an evolving “Pineapple Express” pattern off the West Coast of North America. Orographically enhanced rainfall is usually responsible for moderate to major flooding and storm damage, as an intense,focused precipitation band moves onshore. These narrow, warm, moist “atmospheric rivers” (ARs) are often responsible for record rainfall, warm temperatures, flooding, avalanches and landslides. ARs appear to be a neccesary and sufficient cause of all cool season major flooding in the Pacific Northwest. This presentation explains the nature and detection of ARs while exploring the reality and myths of NW flooding.