The October Mystery Solved!

Well, sort of. For years now, there has been a puzzling discrepancy between what my weather display software (WeatherView32) displays each October for "Average Monthly Rain to Date", and "Average Water Year Rain to Date". Since the "Water Year" starts each year on October 1st, the two numbers should be identical on each day in October, but they aren't.

I was able to calmly ignore this puzzling discrepancy until it became a slightly annoying discrepancy, after Gary Boggs (waveguru) started to point it out in emails to me, and then it became a really annoying discrepancy, once the weather chat room came into existence, and dozens of concerned citizens started bugging me about it.

So, this October, I decided to try to figure it out, once and for all. And, with the aid of a Excel spreadsheet, it became clear what the display software was doing. Here's the spreadsheet of the first 10 days of October:

WeatherView32 contains a database of records and averages for all days of the year, based on the MCAREC historical records here in Hood River. The above chart shows the precipitation data for the first 10 days of October. In column B, the historical daily averages are shown for each day. Column C totals those up from day to day for the month. Column D is what is displayed as the "Monthly Rain to Date" total on the weather web site graphic, and Column E shows what the "Water Year to Date" total is displayed as.

Note that Column C and D match perfectly, day to day, as they should. However, the total in Column E starts lagging behind, but by a varying amount each day. Notice what that amount is?

Yep, that's right. Column E waits until the NEXT day to increment the yearly total upwards, and therefore always lags behind by one day.

Now, WHY it does that is still a mystery, and will probably remain so, as the author of the WV32 software has not returned my emails. So, you now know as much as I do about this puzzling, annoying discrepancy, so please just live with it, as I had calmly learned to do years ago, until I didn't.