So they can change experimental conditions.
Scientists look for observable patterns and they measure whatever is objectively quantifiable.
They use scientific notation for very large or very small measurements
Simply to make a series of 'standard' measurements that are recognised in any country.
Usually scientists do not use any tool to determine how strong a tornado is. Usually the strength of a tornado is determined based on the severity of damage it causes. Occasionally wind speed measurements are obtained using Doppler radar, but such measurements are rare.
So they can change experimental conditions.
Because
It is a fundamental requirement of scientific research that experiment can be replicated so that other experimenters can validate results. This would be impossible unless scientists used standard units and methods of measurement.
They use the Metric system.
Scientists look for observable patterns and they measure whatever is objectively quantifiable.
They use scientific notation for very large or very small measurements
What measurements are you performing? Make sure you aren't bitten if it's large, and make sure you don't kill the animal (unless you need it to be dead)
to find accurate information
If they are sensible, they will use those units defined and agreed by the International Standards Organization (ISO), as these will be universally understood and normally are required to be used in scientific publications.
Absolute Magnitude
There is no instrument on that list that can take any reliable measurements.
SI units such as kilograms, meters, liters etc