"But for a puff of dry air..."

As bad as things are along the Gulf Coast, by every indication it should have been much, much worse.

Devastating as Katrina was, it would have been far worse but for a puff of dry air that came out of the Midwest, weakening the hurricane just before it reached land and pushing it slightly to the east.

The gust transformed a Category 5 monster into a less-threatening Category 4 storm, and pushed Katrina off its Big Easy-bound trajectory, sparing New Orleans a direct hit _ though not horrendous harm.

"It was kind of an amazing sequence of events," said Peter Black, a meteorologist at the Hurricane Research Division of the federal government's Atlantic Oceanographic and Meteorological Laboratory.