if you could not see how low & high pressure centers , how would we determine where each pressure system was located and which direction it was moving?

Refute it, showing why it is mistaken—an apparent but not real problem; acknowledge its validity or plausibility, but suggest why on balance it's relatively less important or less likely than what you propose, and thus doesn't overturn it; concede its force and complicate your idea accordingly—restate your thesis in a more exact, qualified, or nuanced way that takes account of the objection, or start a new section in which you consider your topic in light of it. this will work if the counterargument concerns only an aspect of your argument; if it undermines your whole case, you need a new thesis.

Oofuv