January 17, 12z NAM pressure and wind at the tropopause and 700-500 mb frontogenesis
Notes:
January 17, 12z NAM tropopause pressure and wind forecasts valid at 00z on the 18th (left panel) and 12z on the 18th (right panel), indicated an upper wave moving east from the Great Lakes toward the northeast U.S. A northeast-southwest axis of 700-500 mb frontogenesis was forecast to develop across New York and Pennsylvania during the early morning on the 18th. Forcing for upward vertical motion would likely focus near this frontogenesis axis, as upper-level forcing associated with the upper wave moved in from the west. Click on image for a larger view.
Slide 14