[--MAIN HOME--] [--ALL HABYHINTS--] [--FACEBOOK PAGE--] WAA VS. LOCAL HEATING ON THE 850 MB FORECAST MODELS METEOROLOGIST JEFF HABY There is a fundamental difference between WAA and local heating. WAA is the movement of warmer air into a region. Local heating (diabatic heating) is warming of temperature at a fixed location without movement. WAA is common behind warm fronts and when a strong southerly wind transports warmer temperatures to the north. Local heating is caused by the sun's energy striking the earth's surface. Clear skies, long days, light wind and dry air maximize local heating. Low level WAA causes a dynamic lifting of air (due to column stretching) and can increase thermodynamic instability. Local heating can increase thermodynamic instability but does not cause significant dynamic lifting by itself. When using the models, WAA is denoted in a region where wind vectors are crossing through the temperature gradient from warm toward colder temperatures. The movement of the temperature gradient causes WAA if warmer air is being blown toward a fixed location.