When a rapidly moving arctic air mass invades a warm one, dramatic things can happen. The wedge of cold (denser) air moves under the warm air, forcing it upward. This causes cooling and loss of moisture (rain, snow, sleet, hail). A steep temperature gradient, abrupt wind changes and moist air moving vertically together trigger cumulonimbus and/or tornado development (which was present last Friday). Perhaps the flock of blackbirds that fell flew from a warm air mass into a colder one. Although this sounds benign, it could be deadly.
In the early days of aviation, some airplanes failed to take off on certain cold mornings. Some crashed. The cause of their demise eluded experts sifting through the charred rubble. Finally, they realized the smooth flow of air over the wings was simply disrupted by frost, causing loss of lift. I suspect these poor birds simply flew into freezing air with wet wings. They lost lift before they could reverse course and may have fallen into even colder air before hitting the ground.
You would think birds would instinctively avoid icing; however, this happened just before midnight New Year's Eve when they are normally roosting (fireworks?). Broken legs, internal injuries and perimeter survivors would typify this scenario. All evidence of their problem would melt seconds after hitting a warmer earth. Meanwhile our dedicated wildlife biologists will spend countless hours and dollars focused on elusive parasites, disease, shock, etc. I sincerely wish them well. I simply hope they don't overlook this possibility.
LARRY LUSK, former Naval Aviation Safety Officer,