Seemingly overnight, the oceans are exploding with tropical cyclone activity

By Brian McNoldy &  Matthew Cappucci of "Capital Weather Gang" @ WashingtonPost.com, Sept. 12

The Northern Hemisphere is facing an onslaught of hurricanes and typhoons, seemingly overnight. With three storms spinning in the North Atlantic — Hurricane Florence one of them — the tropics have exploded to life at the peak of the annual season. At the same, in the tropical Pacific, Super Typhoon Mangkhut is the most intense tropical cyclone in the world, packing 170 mph winds.

Why the remarkable uptick in activity? In the Atlantic, in particular, it's all thanks to a sudden alignment of the two things that fuel hurricanes: energy and wind.

If the winds aloft in the atmosphere are too strong, they can shear apart a developing storm. It’s ironic but true — calm winds are needed to brew a hurricane. The amount of shear in the Atlantic has reached its seasonal minimum, kindling any fledgling storm and fostering its growth.

What also changed in the past two weeks is how much instability — or “juice” — storms had to work with. Until two weeks ago, we were well below average. Then all of a sudden, a switch flipped, and the results were explosive [....]