How does a chaser forecast the target?
That’s a simple question with no simple answer, because every chaser has different methods. As a general rule, the chase day usually begins unfolding a day or two before, as model forecasts, severe weather outlooks, television reports, and computer model forecasts all begin hinting at an active day ahead. Chaseable severe weather requires some combination of moisture, instability, lift and wind shear — the four ingredients all organized severe storms need, and which chase forecasters seek. A weakness in one may be compensated for by unusual strength in another; but with a glaring lack of any of those ingredients, storms may be weak or may not form at all. Analyzing surface and upper air data is important as far out as two or three days, to determine where these ingredients are setting up and where they may shift. This continues off and on through the morning of the chase, when the target areas get narower and decisions must be made about when and where to go. If the chaser is already
