Rainfall in the first six months of water year exceeds yearly average

Halfway through the current water year, which began on Oct. 1, rainfall patterns on the Kitsap Peninsula are shaping up to look a lot like last year.

Hansville rain gauge (click to enlarge)
Source: Kitsap PUD

For most areas, total rainfall is well above average, as it was last year at this time. It is also well below the record accumulation in most places. One exception is Hansville in North Kitsap, as you can see in the first chart on this page. There, the total rainfall is tracking both last year and 1999 — the highest year on record, which goes back 35 years at that station.

Moving into the drier half of the water year, it is now obvious that we will be above average in rainfall for the entire year, since we have already reached the average in most places.

Average rainfall on the Kitsap Peninsula varies a great deal from north to south. Since 1990, the average precipitation at Holly in the southwest has been close to 80 inches, according to records from the Kitsap Public Utility District. That compares to Hansville in the north, which averages a little more than 30 inches.

Holly rain gauge // Source: Kitsap PUD

Checking the scale on the charts, one can see that Holly has had about 95 inches of precipitation over the past six months, which is more than all of last year and about 15 inches above the yearly average already this year.

In drier Hansville, the rainfall chart does not flatten out quite as much during the second half of the year. More than 32 inches has accumulated so far this year, which is just above the average for the entire year. Hansville is still chasing the record annual accumulation of 43.8 inches set in 1999. Last year’s total accumulation of 42.5 inches fell just short of that mark and was the second-highest on record.

In Central Kitsap, where most of the population resides, the total rainfall for the past six months has reached 51.7 inches, which is above the average for the entire year and just about equal to last year at this time. It looks like the record of 76.9 inches is safe for this year unless we get extreme rains during the last six months of the water year.

Silverdale rain gauge // Source: Kitsap PUD

The next three months in the Northwest are likely to be close to average for precipitation, according to the National Weather Service’s Climate Prediction Center. Some chance of El Niño conditions are predicted for later in the year. If that occurs, it could reduce the amount of precipitation, but the effects are unlikely to make much difference before the end of the water year in September — although it could have an effect going into the 2018 water year and beyond.

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