A 992 mb surface low was over North Dakota as the outbreak began:
As dewpoints reached 70 as far north as Grand Forks, the dewpoints in South Dakota were in the 40s and even as low as 23 in Nebraska.
Satellite imagery shows just how quickly skies cleared behind the thunderstorms:
Both the low dewpoints and rapidly clearing skies are an indication of strong subsidence.At 2218Z (5:18 CDT), numerous discrete supercells were moving across Minnesota and North Dakota:
This outbreak set a record for the most tornadoes in a single day in Minnesota. More on the outbreak here.The next day, June 18th, the same storm system produced two separate derechos, hitting areas from Iowa to Michigan and Ohio.
The Chicago area had two damaging wind events separated by less than 6 hours:
The only major hurricane activity in the Eastern Pacific so far was in late June.
Hurricane Celia (center) reached maximum intensity on the night of June 24th with winds estimated at 140 knots, and a minimum central pressure of 926 mb. Hurricane Darby (right) was at maximum strength at the time of this image with winds at 105 knots and pressure at 960 mb.In the Atlantic, Hurricane Alex, which had unusually low pressure for its wind speed, reached peak a strength of 85 knots and 947 mb as it made landfall in northern Mexico on June 30th. There was some question if Alex would even survive crossing the Yucatan Peninsula on June 26-27 when it was still a tropical storm. But by comparing these satellite images which were only 2 hours apart, I noticed that the only major change was that convection on the eastern half was actually intensifying.
By June 28th Alex had regained all the strength it had before crossing land:
On June 29th, Alex appeared to have entrained some dry air:
But then became filled with deep convection again just a few hours later:
Alex making landfall on June 30th:
Even though Alex quickly weakened over the mountains in Mexico, its moisture was spread over a huge area.
There was a very well defined edge to the north as the high level moisture spread into the southern United States:
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