“Is there anything in the algorithm that can detect “ultra dry conditions”, and increase the water level over 100%?” — yes, the weather algorithm can output a water level above 100% (though it’s clamped to 200%) depending on the weather. For example, under very high temperature and / or low humidity, it can calculate a water level above 100%.
Maybe you were asking about if the ET algorithm can output more than 100%. That I don’t have enough knowledge to tell. In general it should, because the assumption is that 100% water level corresponds to the water time of an average day so it should be possible to go beyond that.