Not sure how far you are into IRS, 'kouldurepeat' (and I shall say this only once
), but
IRS measures the acceleration forces on an aircraft, produced either by engines, brakes, bank, yaw, pitch or wind (plus some 'esoterics' you do not need to bother about). Therefore ANY change in wind is read by the IRS and computed. Forecast wind is only relevant to the FMC and has no bearing on 'IRS nav' which reacts to ACTUAL effects.