In my Saturday morning post, I mentioned that we have just finished a fine
streak with measurable precip each of the past seven days here in Ashland,
MA. Rainfall total for this period was exactly 2². The only other time
this year we have seen such a streak with seven days in a row of measurable
was the seven days ending March 21. The total for that period was quite a
bit lower at 1.2².

My long term statistics shows that on the average we see measurable precip
on 38% of days. In other words, there is a 38% probability that on a given
day, I will observe .01² or more precip here in Ashland. Does it stand to
reason that the probability of seeing measurable two days in a row is .38 x
..38 = 14%? And taking this to its (il)logical extreme, is the probability
that I will see measurable seven days in a row .38 x .38 x .38 x .38 x .39 x
..38 x .38 = .0011 or about .1%? But...I have already seen such a 7 day
streak twice in year 2004 here. What is faulty with my reasoning.

Extra credit - Are you surprised that I measured .8² more over the past 7
day period than the period ending March 21? Explain your answer.

Jot - Ashland, MA


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