Entering Tsuyu

Tsuyu, the rainy season, began on Monday. Oddly enough, it rained neither Monday nor today, so how did they know it was tsuyu?
They checked the calendar, then confirmed by looking at satellite photos of the cloud cover.
Himawari, Japan’s weather satellite, was retired a few months ago. Now the Japanese weather agency has to rely on American satellites which don’t give them 24 hour coverage over Japan. There’s a plan to launch a new satellite – MTSAT – later this summer but it won’t be in operation until the end of this year.
I suppose tsuyu proclamations don’t have to be very precise but it sure would be nice to have good coverage for typhoons.