Finally we're getting a summer rainstorm. (The summer rainy season usually starts in early July.) There were some out of season showers during the last week of May and then nothing for over two months but a few clouds, some virga, and just enough rain to make the windshield dirty. This storm looks serious.
If you see the arrows - that's the direction the storms are moving. When two (or more) storms collide, it can get violent.