catchment tank overflowing the top

[terracore]

I have a 10,000 gallon steel catchment tank and something new is happening, I'm guessing because all this TS Darby rain. The water is overflowing the top of the tank. There is water coming out of the overflow pipe, but its not blasting out like a firehose like I've seen it do before during heavy rains. 1) Why is this happening and 2) Do I need to be concerned?

ETA: I haven't taken the cover off to look inside because I'm afraid with the gusts the cover might get away from me.