Two decisions plague the 2019 Japanese Grand Prix at Motegi. One, a historical choice made back in 2010, when the Icelandic volcano Eyjafjallajökull erupted, throwing so much ash and dust into the air that it severely disrupted air travel around Europe, forcing Dorna to postpone the race from the original date in April to October. The other, a more recent change made before the 2018 season, where tire allocation for all of the races throughout the year is already fixed before the season even begins.
The change of dates forced on the Japanese Grand Prix as a result of Eyjafjallajökull has stuck, meaning the race is now always in October, as part of the three flyaway races in Japan, Australia, and Malaysia. That has the unfortunate effect of putting the race right at the tail end of typhoon season, which stretches from July to October. Over the years, heavy rains, high winds, and low-hanging clouds have caused the action to be canceled or postponed before. In 2013, Friday practice was canceled completely due to rain and fog, while the 2015 race start was delayed while we waited for the low-hanging cloud to clear, so that the medical helicopter could fly.