Which is almost exactly what the international SARPs specify - make the gusts 10kts or more above the mean and it would be fully compliant with the SARPs. IIRC, you have a UK background - the use of 'instantaneous' values continued in use in the UK many years after it was superseded by major, if not all, international airports in other states because the UK did not implement the averaging SARPs when they were published.