Tag Archives: Rainfall

The word is ‘average’ for the first three months of Water Year 2019

Average, very average. That was my first reaction as I looked over the rainfall data for the first quarter of Water Year 2019, which began Oct. 1.

The point was driven home when I looked at the rainfall totals for Silverdale on the website of the Kitsap Public Utility District. October’s rainfall total was 3.23 inches, compared to a median average of 3.74 inches. November’s total was 5.51, compared to a 6.83 average. And December’s total was 9.31, lining up perfectly with a 9.31 average. (Exactly the same! What’s the chance of that happening?)

Looking at Hansville at the northern tip of the Kitsap Peninsula and Holly in southwest region, monthly totals were pretty close to the averages — with one exception. In December, Holly received 19.86 inches of rainfall, well above the median average of 13.93 inches for the month.

As you can see from the charts, the current trend (blue lines) are fairly close to average (pink lines) and not far off from last year (orange lines), which also was a fairly average year.

Here are all the numbers for October-December in these three areas, with this year’s monthly totals followed by the long-range median average for that month:

  • Holly: October, 5.52, 6.51; November, 12.41, 11.86; December, 19.86, 13.93.
  • Silverdale: October, 3.23, 3.74; November, 5.51, 6.83; December, 9.31, 9.31.
  • Hansville: October, 3.04, 2.68; November, 3.88, 4.37; December, 5.12, 3.91.

As we well know on the Kitsap Peninsula, drier areas are found as you go north with wetter areas to the south. By the way, December is clearly the wettest month of the year for Silverdale and Holly, putting December at the peak of a bell-shaped curve for data collected over many years.

Hansville’s long-term pattern looks a little different, with November at the top of the curve and successive months going slightly lower than the previous month through September, when the rainfall jumps up in October and again in November.

All this information can be found on Kitsap PUD’s webpage for Hydrological Data. Click on “rain gauges” and choose a location. Especially helpful are the current water year daily reports, cumulative charts and monthly box charts.

Looking ahead, the National Oceanic and Atmosphere Administration is predicting warmer-than-average temperatures and lower-then-average precipitation over the next three months.

The predicted El Niño has not yet formed, although sea-surface temperatures in the northern Pacific Ocean are well above average. Forecasters for NOAA’s Climate Prediction Center say there is a 90 percent chance that El Niño will still form this winter and a 60 percent chance that it will persist through spring.

In the Pacific Northwest, El Niño often diverts the jet stream and winter storms to California, leaving us with warmer and drier weather. (La Niña brings the opposite.) So far, oceanic conditions remain neutral, which creates unsettled conditions which are less predictable over the long term.

Hansville sees record rains coming down during November

Hansville is the driest area in Kitsap County, but in November the skies opened up with more rain than we’ve seen there in the past 27 years. In November, enough rain fell in Hansville — 8.7 inches — to break the record for that location.

Hansville // Graphic: Kitsap PUD

Longtime residents of our region realize that the amount of precipitation goes up dramatically as one travels south out of Hansville. For Silverdale, November 2017 was the sixth wettest November in 26 years, with a total of 11.0 inches. Holly experienced its fourth wettest November, with 22.9 inches, all based on rainfall data compiled by Kitsap Public Utility District.

The one glitch for Hansville is that three years of rainfall data are missing — specifically 2007, 2008 and 2009 — and 2007 was a particularly wet year in some parts of the county. In fact, record November rains were seen in 2007 in Holly but not in Silverdale. We may never know where 2007 would have fit into the records for Hansville, but November 2007 was only average in Port Gamble — the closest station. It’s very likely that Hansville really did break the record for November this year.

Silverdale // Graphic: Kitsap PUD

Consistent with those geographic differences, in Holly it rained 27 out of 30 days in November, compared to Silverdale with 22 out of 30 days and Hansville with 20 out of 30 days. This came after a fairly average October.

As you can see from the charts on this page, November rains pushed the lines up to begin tracking the wettest years in the record books from one end of the county to the other. But, as I discussed last month, anything can happen during the coming winter and summer. Last year started out well ahead of the wettest years on record. But, starting in mid-December, the rains did not keep pace with the record years, and then came a very dry summer. See Water Ways, Oct. 27.

Holly // Graphic: Kitsap PUD

Let me take a moment to further emphasize the difference in rainfall from north to south on the Kitsap Peninsula. Holly’s nonrecord precipitation of 22.9 inches in November is more than half of Hansville’s rainfall for the entire record year of 1999, when a total of 43.8 inches came down. Holly’s annual record is 127.5 inches set in 1999.

The average annual rainfall for Hansville is 30.7 inches, compared to Silverdale with a 42.8-inch average and Holly with 79.2 inches.

Looking forward, the rains are likely to continue, according to NOAA’s Climate Prediction Center (PDF 5.3 mb). La Nina conditions emerged in October and are predicted to continue through the winter in the Northern Hemisphere. The likely result will be below-average temperatures and above-average precipitation across the northern part of the contiguous U.S. — and the opposite across the southern tier of states, as shown in the map below.

Green shows above average precipitation; brown is below average.
Graphic: National Climate Prediction Center