Tag Archives: Rainfall

It was a wet water year, but then the weather reversed its course

After unusually high amounts of rain fell on the Kitsap Peninsula last fall, this summer is starting out with a most unusual pattern of dryness.

It appears that we haven’t had any measurable precipitation anywhere on the peninsula since mid-June. That’s an oddity for dryness not seen in even the driest year on record since 1990, when Kitsap Public Utility District began keeping rainfall data.

Since May 17, Central Kitsap has seen only 1.4 inches of rain, while less than half an inch fell in Hansville during that time period. That’s barely any rain, given that we are talking about nearly two months. Holly has experienced about 2.4 inches in that time — still way low for the rain belt region of the Kitsap Peninsula. And to think that last fall I was contemplating that we might break a record this year. See Water Ways, Oct 27.

I will admit that I used to avoid writing weather stories for the Kitsap Sun. If an editor asked me to write about the weather, I would think for a moment and promise a “much better” story of a different kind. Now, as I try to keep up on climate change, I find myself fascinated with what I can learn from rainfall patterns — including the extremes you see going from south to north on the Kitsap Peninsula.

If you haven’t been around the area much, you may not know that we get more and stronger rainstorms in the southwest corner of the peninsula around Holly, while Hansville at the peninsula’s northern tip may get a third as much rainfall in some years.

Take a look at the pink lines in the charts on this page to see the average over 25-30 years. The scales on the left side of the graphs are different, but the charts show an average precipitation around 30 inches for Hansville in North Kitsap, 50 inches for Silverdale in Central Kitsap, and nearly 80 inches for Holly in Southwest Kitsap.

These charts also show the rainfall patterns in each area for this year with a blue line. Last year, which had above normal rainfall, is shown in orange. And the year that ended with the highest total rainfall is shown in green.

Hansville is especially interesting, because this year and last year essentially kept pace with the record rainfall year of 1999 as spring ended and summer began. In fact, on May 16 of all three years, the total accumulation to date in Hansville was 38 inches, give or take less than half an inch.

After May 16, the three years diverged in accumulated rainfall, and this year’s dry spell makes the blue line as flat as it can get for an extended period. Last year, the driest time came in April, as you can see from the flat section of the orange line.

July and August are typically the driest months of the year, but that can vary greatly by year. I used to tell people that we Puget Sound residents can expect a full three months of summer each year, but nobody can predict when it will happen or whether it will be divided up, say a week here and a week there.

Anyway, as I mentioned on April 1 in Water Ways, we are on a trajectory to exceed the average rainfall this year even if we get no more rain until the water year is over on Sept. 30. It appears our water wells will survive, but we need more rain for the streams to rise by early fall for salmon to increase their numbers.

It’s been a wet ride through the first half of the 2016 ‘water year’

With half of our “water year” in the record books, 2016 is already being marked down as one of the wettest years in recent history.

Hansvillej

The water year, as measured by hydrologists, runs from Oct. 1 to Sept. 30 each year, so we will be in WY 2016 for nearly six more months. If things keep going as they are, we will see some new lines plotted on the rainfall charts.

Joel LeCuyer, who keeps track of water data for the Kitsap Public Utility District, points out that the district’s two longest-running weather stations are on their way to record-high totals:

  • Bremerton National Airport, with records going back to 1983, accumulated 66.7 inches of rain at the midway point, compared to an average of 56 inches for the full year.
  • Hansville, with records going back to 1982, has accumulated 36.6 inches, compared to a yearly average of 32 inches.

Looking at the charts, you’ll see that both the airport and Hansville stations are slightly ahead of their maximum water year. It will be interesting to watch this chart as we get closer to June, when rainfall traditionally falls off dramatically. Whatever happens over the next two months will likely foretell whether annual precipitation records will be broken.

Airportj

To access the charts, go to the KPUD website. Under the tab “Water” click “Water Resources Data.” At the bottom of the map, click on the tiny bubble “Rain gauges.” The red ones track precipitation almost in real time.

Looking back, some rather dramatic downpours are already written into the record books this year. For example, when considering the top 10 rainfalls in a 24-hour period, nearly every station has at least one rain event from WY 2016 among the top 10.

At Holly, four of the top 10 rain events recorded over the past 25 years occurred during the past six months. That’s interesting, since Holly is one place where the total accumulation of rainfall is still falling short of the record. Holly has already surpassed the average annual rainfall of nearly 70 inches, according to the chart, but it is unlikely to reach the nearly 130 inches of rainfall recorded in 1999.

Hollyj

Above average precipitation was seen across Western Washington for the first half of the water year, according to the National Weather Service. The range was from 26 percent above average in the Olympic Mountains to 40 percent above average in the Puget Sound lowlands. Snowpack in the Olympic and Cascade mountains is about 10 percent above average.

Ted Buehner of the National Weather Service in Seattle reports that the current warm El Niño is expected to weaken through the spring. And there is a 50 percent chance that La Niña will return next winter. That would typically bring cooler and wetter weather, but rains over the coming winter will have a long way to go to match what we’ve seen during this water year.

As for what we might expect from now through the end of summer, the latest forecast from NOAA’s Climate Prediction Center says temperatures are likely to be warmer than average in the Northwest with slightly higher than even odds that the summer will be drier than average.

For details on a national scale, check out “ENSO: Recent Evolution, Current Status and Predictions” (PDF 3.5 mb).

Kitsap precipitation nearly normal during
the past water year

Despite concerns about drought in much of Washington state, Kitsap County came through the water year (ending Sept. 30) with precipitation just about normal.

Precipitation at Hansville over the past water year.
Precipitation at Hansville over the past water year. (Click to enlarge) // Graphic: Kitsap PUD

As you can see from the graphs on this page, precipitation in 2015 (blue line) fairly well tracked the average (pink line). The previous water year (orange line) was more concerning, although both 2014 and 2015 water years ended in fairly decent shape.

Areas in North Kitsap ended the year somewhat above average. In Hansville, the annual total was 34.3 inches, compared to an average of 30.2 inches. In Central and South Kitsap, many areas were slightly below normal. In Holly, the annual rainfall was 69.4 inches, compared to an average of 76.6 inches.

Hansville precipitation over the past water year.
Precipitation at Bremerton National Airport over the past water year. (Click to enlarge) // Graphic: Kitsap PUD

The Kitsap Peninsula largely relies on groundwater for its water supplies, and we have gotten enough rains to keep the aquifers in fairly decent shape, according to Mark Morgan of Kitsap Public Utility District.

“Aquifers experienced their typical summer drawdown, driven more by demand than by drought, but (it was) nothing exceptional,” Mark said in a summary of the water year.

Concerns about drought in other parts of the state were largely based on a lack of snowpack coming out of last winter.

Precipitation at Bremerton National Airport over the past water year.
Precipitation at Holly over the past water year. (Click to enlarge) // Graphic: Kitsap PUD

Meanwhile, flows in many streams hit low-flow conditions a month earlier than normal this past summer, but some maintained their typical flow, Mark said. Adequate streamflows are critical for coho salmon, which spend a year in freshwater, as well as for year-round residents, such as trout.

The forecast for the winter is based on strong El Nino conditions (see map below), which means that sea surface temperatures off the coast of South America will be significantly higher than usual — up to 3.4 degrees F (2 degrees C). Above-normal temperatures are expected across the western U.S. as well as the northern tier states and Eastern Seaboard, with the greatest chance of above-normal temperatures in the Pacific Northwest.

Sea surface temperatures are above average across most of the Pacific Ocean. NOAA map
Sea surface temperatures today are above average across most of the Pacific Ocean. (Click to enlarge) // NOAA map

Below-average temperatures are expected in New Mexico and West Texas. For details, see the prediction maps at the bottom of this page or check out NOAA’s Climate Prediction Center.

While much of the country will benefit from greater rainfall, below normal precipitation is expected for the Northwest and areas in the Eastern Great Lakes, New York and northern New England.

Climatologists predict with 95 percent certainty that the El Nino will continue through the winter in the Northern Hemisphere before gradually weakening in the spring.

Temperatures are predicted to be warmer this winter across the northern states. NOAA graphic
Temperatures this fall are predicted to be above average across the northern states. // NOAA graphic
Precipitation is predicted to be less than normal in the Pacific Northwest. NOAA graphic
Precipitation is predicted to be less than normal in the Pacific Northwest. // NOAA graphic

Kitsap rains: not too much, not too little for salmon and aquifers

The on-and-off rains over the past two weeks are nearly perfect for both spawning salmon and for recharging shallow groundwater supplies, experts say.

Chum salmon in Chico Creek. Kitsap Sun photo
Chum salmon in Chico Creek.
Kitsap Sun photo

For October, total rainfall ranges from about 5 inches at Hansville to 12 inches at Holly, according to rain gauges managed by the Kitsap Public Utility District. Fortunately, those rains have not been delivered to us in only a few days.

The intermittent nature of October rains has allowed the streams to maintain their flows without flooding. They’ve also allowed infiltration into the ground without excessive runoff.

“It is the good kind of rain,” said Bob Hunter, interim manager of Kitsap PUD. “We’ve had a couple of days when we’ve had 2-plus inches, but we haven’t seen the streams flash.”

In other words, the streams have not risen excessively fast. Bob attributes that to how dry the ground was before the rains began. Soils were able to absorb much of the early rainfall before stormwater runoff began to increase. Pauses between the rainstorms allowed more of the water to soak into the ground.

“It just goes to show you the variability that we have around here,” Bob told me.

October marks the beginning of the 2015 “water year.” Although we are just a month into the start of the year, the rainfall has been closely tracking all-time highs at some rain gauges — including Holly, which has been monitored since 1999. (See charts below.)

Meanwhile, the rain pattern in October was nearly perfect for salmon, said Jon Oleyar of the Suquamish Tribe, who walks the East Kitsap streams to count migrating salmon as they arrive.

“It seems like we’ve had storms coming in every couple of days, so they are not right on top of each other,” Jon said. “That gives the streams some time to recede.”

When there is not adequate flow, the salmon often wait for the streams to rise. On the other hand, too much flow can wash salmon eggs out of the streambed.

Last week’s rains got the chum salmon moving into most of the East Kitsap streams, Jon told me.

“I checked Chico Creek on Wednesday, and there were almost 11,000 fish in there and going up about as far as they can get,” he said.

A good escapement for the Chico Creek system is between 12,000 and 15,000 chum, and there is still more than a month left — assuming a typical timing of the run, he said. But things are looking a little different this year, he noted, and the bulk of the run may have arrived already.

One indication that timing could be different this year is that Gorst Creek already has a fair number of chum salmon — perhaps 500 — yet the Gorst Creek run usually comes in later and continues well into December.

Is it possible that all or most of the salmon runs are coming in early? It’s a question that only time will answer.

Jon told me that he’s a bit water-logged at the moment, trying to count fish in the rain with the streams running high.

“I’m pretty happy about it,” Jon said. “I have my fish up where they need to be, but it’s just hard to count them right now. If you’re a fish, this is really working for you.”

In the charts below, found on the Kitsap PUD’s website, you can see that October’s rainfall has been tracking the record high rainfall at these stations. Of course, the “water year” has barely begun, so anything can happen. (Click on images to enlarge.)

Rain-Holly

Rain-CK

Rain-Hansville