I did a Python analysis on Baltimore's precip totals, just cause I felt like it, and it turns out that 2018 single-handedly wrecked the normal distribution. Precip totals are now skewed to the right. Sometimes one extreme outlier is all it takes.
Baltimore's final total of 71.82" is over 4 standard deviations above the long-term pre-2018 average.
From what I can tell, nobody knows the appropriate probability distribution for precipitation data. It appears to vary by region. The normal distribution isn't widely used because it allows for negative precipitation values and underestimates the probability of large totals. The gamma distribution is widely used, but it too can underestimate the probability of extreme events.
Our region's extreme run
in Mid Atlantic
Posted
From what I can tell, nobody knows the appropriate probability distribution for precipitation data. It appears to vary by region. The normal distribution isn't widely used because it allows for negative precipitation values and underestimates the probability of large totals. The gamma distribution is widely used, but it too can underestimate the probability of extreme events.