Five storms have dumped more than 3’ of rain on the US in 2 years:
60.58” 2017 Harvey (Texas)
58” 2018 Lane (Hawaii)
43.15” 2019 Imelda (Texas)
37.9” 2017 Maria (Puerto Rico)
35.93” 2018 Florence (North Carolina) [Tropical storms with highest rainfall.]
Hurricane Dorian was a near miss with over 3’ of rain in the Bahamas. Dorian was the fifth Category 5 Atlantic hurricane in five years!
Hurricanes are heat engines, so higher air and water temperatures provide the energy for stronger storms. Warmer air holds more water, enabling harder rains. Climate change seems to causing these strong storms to move slowly; Hurricane Dorian basically stalled out, moving slower than 1 mph at times. The slower forward motion of these storms seems to be caused by slower wind currents and probably caused by much higher temperatures in the Arctic.
[researchers] think it's caused by a general slowdown of atmospheric circulation (global winds), both in the tropics, where the systems form, and in the mid-latitudes, where they hit land and cause damage.
Hurricanes are steered and carried by large-scale wind flows, "like a cork in a stream," said Tim Hall, a hurricane researcher with NASA's Goddard Institute for Space Studies and author of the study. So, if those winds slow down or shift direction, it affects how fast hurricanes move forward and where they end up.
…
"in the broadest sense, global warming makes the global atmospheric circulation slow down," said NOAA hurricane expert Jim Kossin, co-author of the June study.
He said scientists suspect the overall slowing of winds is at least partly due to rapid warming of the Arctic. The temperature contrast between the Arctic and the equator is a main driver of wind. Since the Arctic is warming faster than lower latitudes, the contrast is decreasing, and so are wind speeds.
Why Are Hurricanes Like Dorian Stalling, and Is Global Warming Involved?
Finally, my thanks to Greta and the other students striking for climate.