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?)
UPDATE:
July 5. Greg Johnson, who lives in Hansville and manages the
Skunk Bay Weather
station there, said the unusually high rainfall in June for
Hansville, compared to the rest of the peninsula, was the result of
the Puget Sound convergence zone settling over the area on several
occasions. Weather conditions brought localized squalls during the
month, he said, adding, “This is very unusual for us.”
The reading at Greg’s weather station, 1.98 inches for the month
of June, was somewhat lower than the 2.26 inches recorded at Kitsap
PUD’s weather station in Hansville.
—–
Cool, often cloudy conditions have helped obscure the fact that
very little rain has fallen on the Kitsap Peninsula over the past
two months.
Precipitation in Holly
(click to enlarge)
Now that we are in the fourth quarter of the water year, we can
see that rainfall levels for this year will be close to average for
most areas on the peninsula. What might not be recognized, however,
is that April was well above average, while May and June were well
below average.
After two years of near-record rainfall across the Kitsap
Peninsula, precipitation has returned to a more normal pattern.
Halfway through the water year, which begins in October,
rainfall in Hansville, Silverdale and Holly are all within 10
percent of the average for this time of year, according to weather
instruments managed by Kitsap Public Utility District.
This near-average total for the first half of the year comes
about despite a very wet November, when Hansville broke the
all-time record for precipitation for that month. Since then, the
monthly rainfall numbers have been mostly below average, except for
a wet January when Holly nearly broke the record for that
month.
As we’ve seen time and again, the amount of rainfall decreases
dramatically as one travels from south to north on the Kitsap
Peninsula. That’s the general pattern for all times of the year,
although the amount of precipitation can vary wildly.
Hansville received 25.5 inches for the six months ending April
1, compared to a 28-year average of 23.1 inches for that period.
Last year, the six-month figure was 7 inches higher at 32.5 inches,
and the first half of 2016 went down in the record books with a
total of 37.0 inches.
Silverdale posted 35.1 inches of rain by April 1, compared to a
28-year average of 38.1 inches for this time of year. Last year,
this Central Kitsap area received 51.7 inches by April, and in 2016
the number was 52.3 inches, second only to 1999 with 69.8
inches.
In rainswept Holly, residents experienced 68.7 inches by April
1, compared to a 27-year average of 65.0 inches. By April 1 last
year, Holly was practically swimming with 95.9 inches, driven by
24.0 inches during the month of October 2016 and 21.8 inches the
next month. But nothing compares to the first half of water year
1999, when Holly received 120 inches for the first half of the
year. Following a fairly dry summer, water year 1999 in Holly ended
with 127.5 inches of precipitation.
NOAA’s Climate Prediction Center has projected somewhat
higher-than-average rainfall through the end of this month in the
Pacific Northwest, followed by fairly average conditions going into
summer. Forecasters rely heavily on observations about temperatures
in the Pacific Ocean, which influence a natural cycle known as the
El Niño Southern Oscillation, or ENSO. See video this page.
A very strong El Niño during 2015 and 2016 (associated with the
much-discussed “blob”) shifted into a weak La Niña in 2017.
Conditions have now reversed course again and seem to be headed
toward neutral. La Niñas are generally associated with cooler and
wetter weather for our region of the country, while El Niños
suggest warmer and dryer conditions — although it does not always
turn out that way.
Neutral conditions are expected to arrive by summer, and some
forecasters predict that the warmer El Niño could arrive toward the
end of the water year in September, according to information
released today by
the Climate Prediction Center.
“Some of the computer models are forecasting development of El
Niño by next fall,” noted research scientist Emily Becker in a new
post on the
ENSO Blog, “but there are a number of reasons why we’re not
completely taking the bait right now.
“First, forecasts made this time of year tend to be less
successful,” she continued. “Another reason is that, while elevated
subsurface heat content in the spring sometimes precedes the
development of El Niño in the fall, some recent studies have found
that this relationship has not been very reliable over the past two
decades.”
Researchers observed a warming trend in March among subsurface
waters in the Eastern Pacific. Those waters are expected to rise to
the surface over the next few months to potentially neutralize any
cool surface waters that remain. The outcome is likely to be the
end of the current La Niña and possibly the beginning of a new El
Niño, featuring warmer ocean conditions.
UPDATE: April 24, 2015
Cliff Mass, professor of atmospheric sciences at the University of
Washington, says in his
blog that it is too early to be predicting severe drought in
Western Washington this summer because of possible late-spring
rains:
“I believe the media and some local politicians have gotten a
bit too worried about our ‘drought.’ We have NOT had a
precipitation drought at all….we are in a snow drought due to warm
temperatures. The situation is unique and I suspect we will weather
this summer far better than expected.”
—–
The word seems to be getting around about the record-low
snowpack in the mountains, which could create a shortage of
drinking water and even lead to problems for salmon swimming
upstream. Read about Gov. Jay Inslee’s expanded drought emergency, issued
today, as well as the last
update from the U.S. Department of Agriculture.
Kitsap Peninsula and the islands of Puget Sound are in their own
worlds, fairly insulated from what is happening in the higher
elevations. In these lower elevations, the key to water supplies is
rainfall, not snow, and the outlook for the year is normal so
far.
As you can see from the charts on this page (click to enlarge),
this year’s rainfall has been tracking closely the long-term
average. If the rains are light and steady, much of the water will
soak into the ground and recharge the aquifers where most area
residents get their water. The aquifer levels tend to rise and fall
over multiple years, depending on the rainfall.
Casad Dam on the Union River, which supplies a majority of
Bremerton’s water, filled in January, well ahead of schedule, said
Kathleen Cahall, water resources manager for the city. The dam is
scheduled for a normal drawdown, and Kathleen said she does not
expect any water shortage.
“We filled the reservoir fairly early this year,” she said. “We
are looking pretty good for the summer.”
October, the first month of the water year, was unusually wet,
Kathleen said. December precipitation also was high. The other
months were fairly normal for precipitation.
Precipitation in the Puget Sound region is expected to be below
average for June, July and August, according to models by the
NOAA’s Climate Prediction
Center. Interestingly, large portions of the Central and
Southwest U.S., Alaska and Florida can expect above-average
precipitation. See U.S. map.
Streams on the Kitsap Peninsula are fed by surface water flows
and shallow aquifers. At the moment, most of the streamflows are
near their historical average. That’s not the case for the larger
rivers in the Northwest, which rush out of the mountains. Most are
well below their normal flows, as shown by the map with the
dots.
Low streamflows usually mean higher temperatures and stress for
salmon. Low flows also can affect fish passage in some stretches of
the rivers while also reducing spawning areas.
While things look fairly good on the Kitsap Peninsula now,
things can change quickly. We have different vulnerabilities than
elsewhere. Climate-change models predict that rains will grow more
intense in the future without changing annual precipitation very
much. That means more of the water will run off the land and less
will soak in, potentially reducing aquifer levels over time.
Managing those underground water supplies will become more and more
critical.
