Thursday, August 29, 2013

Precipitation Percentages

As the rain continues to fall in Anchorage, it seems like a good time to take stock of the amount of rain falling withing discrete intervals. Not surprisingly, when looking at the historical record, small precipitation values are more common than large values. For Fairbanks, 31% of days that have measurable precipitation have a total of either 0.01" or 0.02" (note: this includes melted snow). In 2013, 24% of "wet" days (through 8/28) ended with a grand total of 0.01" or 0.02". Those numbers are pretty close to one another. What really stands out is the large percentage of high precipitation days for Anchorage and the low number of days for Fairbanks. Fairbanks has had 1 day with 0.26" to 0.50" and 3 days with over 0.50". Anchorage has had 18 days with 0.26" to 0.50" and 4 days with over 0.50".

The first chart only looked at the count of days represented in each category. The second chart looks at the percentage of the annual precipitation that fell in each of 6 different categories (note: the categories are slightly different between the two charts). Since Fairbanks is far behind in annual precipitation so far in 2013, the three days with over 0.50" of precipitation represent 1/3 of the annual total. Other than those three wet days, the annual deficit is very noticeable in the 0.21" to 0.30", 0.31" to 0.50", and the over 1.00" categories. On the other side of the ledger, Anchorage is running behind in terms of total precipitation in the smaller categories but more than makes up for it in the wetter categories.

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