Now you are arguing like a child. Without a scientific explanation of the physics involved, noticing a pressure drop is only the beginning of a scientific explanation. Does the storm cause the pressure drop, or the pressure drop cause the storm? Sometimes the pressure drops and there is no storm. Noticing a pattern is the beginning of the work, not the end.
At least you're admitting that noticing a pattern has some value. Now take the next step: if you notice the pattern, and then make a prediction based on what you've noticed, you have a hypothesis. And when the prediction is borne out consistently, and is borne out for other people, you have a pretty good theory.
This is what's been going on with the theory of evolution for the past 150 years. No, we don't have a complete scientific explanation for how every single thing works. I don't know if we have a complete explanation for why air pressure drops in advance of a storm--I know I couldn't tell you without looking it up. But while you stand on the sidelines saying, "Sometimes the pressure drops and there is no storm!" and asking which came first, the rest of the world is buying barometers and knowing when to get out of the rain.