Hello Kyosanto,
thanks for looking into this issue and providing me with the weather information. I send British Airways those information and they answered me with this:
I’ve had another look at your claim for compensation and I’ve taken time to make sure our response is accurate and up-to-date. Based on this, our decision hasn’t changed and the response you’ve received about the eligibility of your EU compensation claim are correct.
As your flight was cancelled due to adverse weather conditions, it means you’re not eligible for EU compensation.
So what are the next steps? Fill out a money claim?