Ocean temperatures and their connections to weather trends have been making news. Five 天美影视传媒 experts offer their perspectives on the current El Ni帽o 鈥� a climate pattern in the tropical Pacific Ocean that affects weather worldwide. UW researchers comment on the current El Ni帽o, its effect on weather in the Pacific Northwest, as well as on regional and global ocean temperature trends.

, a UW research scientist at the , comments on the developing El Ni帽o:

“This El Ni帽o has evolved in a really interesting way. Since spring, the dynamical models have very confidently predicted an El Ni帽o event. But while the key region of the tropical Pacific has warmed quickly, the typical atmospheric response has lagged. The atmosphere in the tropical Pacific is only now becoming more typical of an El Ni帽o event, although it is still not fully matching the ocean surface. That鈥檚 unusual, because the tropical ocean and atmosphere tend to evolve together.

“It will be interesting to see how this El Ni帽o continues to evolve over the next few months, which will help determine the extent of impacts on our upcoming winter weather. Remote impacts in places like Seattle tend to be stronger for stronger El Ni帽o events. While sea surface temperature has typically been the main measure, the impacts might very well depend more on the atmospheric response. So the evolution of the system over the next few months will be key to the eventual local impacts in places like Seattle.”

Dennis Hartmann, professor of atmospheric sciences at the UW, on El Ni帽o and its effects:

“The impact of El Ni帽o on the Pacific Northwest varies a lot from one event to the other, depending on the spatial structure and size of the sea surface temperature changes in the tropics, and on the state of the atmosphere between the tropics and the Pacific Northwest. For that reason, the predictions of Pacific Northwest impacts based upon El Ni帽o events that happened in the past are quite uncertain.

“In addition, the climate has warmed significantly in both the tropics and outside the tropics since some of the prior big El Ni帽o events, in the 1970s and 1980s. That may add an additional complication to making an accurate forecast of how this winter will be different because of the current El Ni帽o event.”

Nick Bond, a research scientist at CICOES and Washington鈥檚 state climatologist, on El Ni帽o and its effects on Washington鈥檚 weather:

“El Ni帽o conditions are present now in the tropical Pacific Ocean, and they are very likely to persist through the coming winter. The effects on Washington鈥檚 weather are expected to feature relatively warm, and perhaps drier, weather than usual after Jan. 1, and ultimately a lower-than-normal snowpack in our mountains at the end of winter. El Ni帽o’s impacts on the weather in Washington state tend to be more consistent in the middle to latter part of the winter.

“But this is not written in stone 鈥� there has been variability among past El Ni帽os in terms of effects on Washington鈥檚 winter weather.”

Jan Newton, senior principal oceanographer at the UW Applied Physics Laboratory and director of the UW-based , on what oceanographers are seeing in regional waters:

“Conditions off Washington鈥檚 outer coast have varied and are mainly influenced by changes in coastal upwelling and downwelling in the Pacific Ocean. Temperatures off the outer coast are now 4 degrees Fahrenheit (about 2 degrees Celsius) above normal, though variable.

“In Puget Sound, we鈥檙e starting to see surface water temperatures shift from cooler than normal, or normal, to consistently warmer than normal, but only by less than one degree Fahrenheit (half a degree Celsius). Given the large-scale warmth in the satellite-measured sea surface temperatures offshore, I do expect that we will continue to see warmer-than-normal sea temperatures in Puget Sound.聽 However, it鈥檚 hard to predict if these differences from the average will stay small or will increase. What happens next will depend on ocean conditions and local weather.”

LuAnne Thompson, UW professor of oceanography, on the :

“The recent acceleration of ocean warming in the Atlantic is unprecedented in the historical record, and has created an Atlantic-wide marine heat wave. The ability of the ocean to absorb and store vast amounts of heat makes these types of events last longer. I study marine heat waves with a focus on their evolution in time and space. However, with more long-lasting, basin-wide events, such as the one we are seeing now in the Atlantic Ocean, we will need to reevaluate our approach.

“At a particular location, a marine heat wave occurs when the sea surface temperature is above a threshold, defined by what is typical for that time of year, and lasts for at least five days. However, with the global warming projected over coming decades, these dangerous hot water events will no longer be localized and of finite duration 鈥� they will no longer fit the traditional definition of marine heat waves. Instead, these marine heat wave events will become more persistent and widespread, and eventually will cover entire ocean basins.”

For more information, contact Levine at aflevine@uw.edu, Hartmann at dhartm@uw.edu, Bond at nab3met@uw.edu, Newton at janewton@uw.edu and Thompson at luanne@uw.edu.

The new is freely available on the Office of the Washington State Climatologist鈥檚 website. It replaces a tool made more than a decade ago that collected snow depth data from the NWAC website to create a simple graphic on the state climatologist鈥檚 website.

鈥淲hen that display wasn鈥檛 working, that鈥檚 the one where we would get emails from ski enthusiasts or other meteorologists or climatologists. To us that was a good sign that we should rebuild it,鈥� said Karin Bumbaco, a UW research scientist who is the assistant state climatologist.

The new version, built with support from Tableau, is interactive, displays more data and is more reliable. It lets users explore differences in mountain snow depth from one season to the next and create a graphic of the results.

鈥淭his is a tool that people in the weather community, like meteorologists and climatologists, as well as snow recreationalists, can use to communicate the current snow conditions and how they relate to average conditions and previous years,鈥� Bumbaco said.

A default view shows the current year compared to the past 30 years of data at a single location. Changing the settings can display measurements back as far as 1927 for the longest-running stations, on Mount Baker at Paradise on Mount Rainier. Measurements go back to 1974 for the two most recent stations, at Mount Hood Meadows and Timberline in Oregon.

The Northwest Avalanche Center monitors mountain snow depth for their forecasting operations as avalanches pose risk to roadways and people venturing onto the winter slopes. Data are entered 12 times a year, on the 1st and the 15th of each month, during the monitoring season from Nov. 15 to May 1.

The monitoring sites are part of the center鈥檚 mountain weather station network. Some sites are owned by the Washington state Department of Transportation, while others are partnerships between NWAC and the transportation department, ski areas or national parks. While other measures exist, they don鈥檛 have the same history of similar measurements.

鈥淲e use this tool to track how our snow depth is building across NWAC’s forecast region in a historical context,鈥� said Dennis D鈥橝mico, meteorologist and forecast director at the Northwest Avalanche Center, who worked on the project. 鈥淟ocal professionals and recreationists track this report all season long. This new tool will allow them to explore historical snow depth data in a modern visualization tool at winter recreation access points.鈥�

The new tool complements a previous UW data visualization looking at long-term weather trends. Official trends in mountain snowpack are measured in snow-water equivalent, or the amount of water when the snow is melted. Those trends vary throughout the state and generally show long-term declines of about 3%-10% per decade, Bumbaco said.

“Tableau Public is an ideal medium for this sort of civic, historical data,鈥� said Blair Hutchinson, product manager at Tableau. “The visual dashboards we created provide people with a great way to interact and make informed decisions regarding the聽snowpack聽on a seasonal scale.鈥�

The many people seeking outdoor recreation during the pandemic are lucky that as of early February, most of the 11 stations are now measuring slightly above-normal snow depth. This winter had been forecast to be an La Ni帽a year, which is often slightly cooler and wetter in the Northwest, Bumbaco said. It鈥檚 delivered on half that promise, with December-January conditions generally warmer and wetter than average.

The continues to predict conditions slightly cooler and wetter than normal, Bumbaco said, which means we鈥檙e likely to see a healthy snowpack.

The new visualization tool was supported by Tableau.

For more information, contact Bumbaco at kbumbaco@uw.edu or 206-543-3145 and D鈥橝mico at dennis.damico@nwac.us.

After many people in the Puget Sound region had dismissed any chance of snowfall in the lowlands this season, the region is now on track for not one, but two, and possibly even more snowstorms this winter.

, a 天美影视传媒 associate professor of atmospheric sciences who serves as , commented Thursday on the upcoming snowstorm 鈥� the second to hit the Puget Sound region this week.

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It’s not a coincidence that we’re getting even more snow 鈥� the situation on the ground matters for the coming snowstorm, Bond said. Because the ground is already cold, that will chill the air enough that this storm will likely bring snow from the start, instead of rain followed by snow. Also, this cold spell means that snow will likely last on the ground longer.

“It is a very unusual situation we’re in, which is sustained cold weather,” Bond said. “Oftentimes, the atmospheric circulation patterns get into a state that’s favorable for snow, but because it’s a rare event, it just doesn’t hang around that long. Then we get back to more air coming off the Pacific Ocean that’s relatively mild, and a return to more normal temperatures.

“But in this particular case, we’ve just kind of gotten locked into a pattern where we’re going to continue to get colder air from the north, along with that special set of circumstances in which we can get the lift, the precipitation, and the snow to fall. It doesn’t happen very often 鈥� maybe every decade, or even two, that you have something like this. So it’s quite remarkable.”

Bond defers to the National Weather Service for exact predictions, and notes that the exact timing and location of the heaviest snowfall is hard to predict. But he expects it to be a more unusual event in the lowlands than at higher elevations.

“These patterns aren’t really huge snow producers for the mountains,” Bond said. “They don’t produce a great deal of total precipitation, so it’s not the most favorable for really piling up snow in the mountains. But they will get some, and our snow pack right now is a little below normal. We’re not panicking, but there is some concern about water supply next summer. So hopefully they’ll get some, too.”

Bond is a member of the , a collaborative research center between the UW and the National Oceanic and Atmospheric Administration.

The air that is hitting us is not the same mass of cold air that hit the Midwest a few weeks ago, but the two events are somewhat related, Bond said.

“If you were to track the wind patterns, and ridges of higher pressure and troughs of lower pressure, sometimes the overall pattern around the whole Northern Hemisphere will be more circular 鈥� very symmetric,” Bond said. “Other times, it has these big ridges and big troughs, so there are places with strong north winds and strong south winds. So we’ve been in one of those kind of wavier patterns.”

One common question in the media is whether the “polar vortex” might be destabilized, sending more Arctic air into the mid-latitudes under global warming. Bond said that with a short record and evidence on both sides, the jury “hasn’t even been called yet” to establish if that connection exists.

As for whether this cold snap disproves global warming, Bond said the answer is clearly no.

“This is weather, not global warming. 2018 was by most measures the fourth-warmest year on record. But these sort of cold-weather events will still happen.”

And the cold seems likely to stick around.

“Right now, it looks like it’s going to stay cold for an extended period 鈥� at least another week or so, maybe a little bit longer,” Bond said. “It won’t necessarily be bitterly cold, but below-normal temperatures. The crystal ball starts to get really fuzzy when you start to look longer than a week or so, and it doesn’t really imply anything for the spring.”

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For more information, contact Bond at nab3met@uw.edu

The 天美影视传媒’s College of the Environment has teamed up with Seattle visual analytics company to create a new, interactive visualization for historical observations of temperature and precipitation in Washington, Oregon, Idaho and western Montana, and for Washington snowpack.

The lets anybody interact with the records going back as far as 1881 and look for significant trends.

“This tool lets anyone, from researchers to meteorologists to members of the public, look at the actual data to motivate why we should care about our climate changing, and see how it is changing in our own backyard,” said project lead , the assistant state climatologist for Washington.

The tool uses Tableau’s interactive visual analytics platform to select one or several National Oceanic and Atmospheric Administration stations in the Pacific Northwest, plot the trend and play around with time periods, seasons and other variables.

“You have to have people explore historical climate in order to understand the context of future climate,” said project co-lead , lead scientist for science communication at the Climate Impacts Group. “We hope Tableau visualizations like these will become go-to resources for engagement and exploration of climate data in our region.”

A previous version of the tool ran on Google Maps and was the most popular feature on the state climatologist’s website. But it sometimes crashed and it was cumbersome to load new weather observations, so it was updated infrequently.

The new tool was created in the summer of 2018 when the UW and hired UW atmospheric sciences alumnus to migrate the tool from Google Maps to Tableau.

The new platform launched in September is more visually appealing, more stable and is easier to update, with plans to update observation records every few months. Users can access it to easily explore the data for their city or region, and produce graphics that display the data and any significant trends.

The tool displays quality-controlled records of temperature and precipitation beginning in the late 1800s. These data are a subset of federal weather observations, known as the , which includes the best-located stations with the longest records the agency recommends using to look at climate trends.

On the map, stations with an increasing temperature trend show up as a red bubble, and decreases are blue. A statistically significant increase gets a big red bubble, while a statistically significant decrease gets a big blue bubble.

For temperature, the map is filled with big, red bubbles.

Are those trends the impacts of climate change in the Pacific Northwest?

“Definitely,” said Bumbaco, who is also a research scientist at the UW’s Joint Institute for the Study of the Atmosphere and Ocean. The most striking trends are in summer nighttime temperatures, the daily minimums, which she says are increasing across the region.

The team surveyed other state climatologists, on-air meteorologists and other potential users in the region to get feedback when creating the tool.

People can use the map’s navigation button to zoom in or out, and then click a triangular button below to access buttons that select regions of the map. Clicking on a single station pops up a summary of its data and creates a line graph below that shows each year’s observations over time. Clicking several stations compares those observations. Tools at the left can have the popup window show changes over the entire period of observations, per year or per decade. Users also can add a trend line to the line graph, add an average value, or compare a location with the statewide average.

The tool gently encourages users to display statistically significant trends by showing a gray color if the time period is shorter than 30 years, considered the minimum for a climate trend.

Along the bottom of the screen are buttons that let users download, export or email their visualizations.

, a technical advisor at Tableau who helped create the tool, said the ongoing collaboration allows him to learn more about how to visualize unique datasets and help people create user-friendly interfaces.

“My basic advice for new users is to interact,” Cory said. “People are used to visualizations being static, and they don’t realize that if I move my mouse over, something happens, and if you click, something happens.”

The tool also includes snow-water equivalent, a measure that takes density into account, for Washington state beginning in 1930 from the federal sites. The snow observations are best for April and show decreases in many parts of the state.

Precipitation in the Pacific Northwest doesn’t show a clear trend, though many areas show wetter springs, Bumbaco said.

The Climate Impacts Group has been working with Tableau since 2016 to create other, more forward-looking , such as a future , or projected changes in around Leavenworth, Washington. The partnership with the Office of the State Climatologist creates consistent and common visualization tool for the two groups.

“Our collaboration with Tableau has helped us to consider everything from what colors you use and how thick should the lines be, to addressing bigger issues, like where you start with a visualization, how users navigate through it, and what information users need to navigate it successfully,” Roop said.

The updated Pacific Northwest climate trends analysis tool is open source, so other regions of the U.S. or other countries could potentially use it to display their historical observations using the same Tableau interface.

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For more information, contact Bumbaco at kbumbaco@uw.edu or 206-543-3145, and Roop at hroop@uw.edu. For Tableau communications, contact Dan Jensen at djensen@tableau.com.

More example visualizations are .

Early reports suggest that the winter of 2018/2019 will be a weak to moderate El Ni帽o year. For the Pacific Northwest, that probably means less snow in the mountains than average, especially late in the season.

“El Ni帽o is when the tropical Pacific is warmer than normal, right in a thin strip along the equator, and what happens as a result is there’s a shift in these large clusters of thunderstorms, and that has a ripple effect on the atmospheric circulation over much of the globe 鈥� including in our neck of the woods,” explained , a 天美影视传媒 associate professor of atmospheric sciences who studies links between the ocean and atmosphere.

El Ni帽o winters tend to be warmer than normal, especially after January 1, said Bond, who also serves as the ..

For skiers, “El Ni帽os aren’t all bad,” Bond added. “In particular, early on in the winter there can be some good conditions 鈥� some healthy snows. One thing we do see is a tendency for less snow pack than usual at the end of an El Ni帽o winter. That means at certain elevations, maybe a little bit more rain versus snow.”

Meteorologists can predict an El Ni帽o or La Ni帽a year with some skill six months or even farther out, he said.

In August 2018, , the assistant state climatologist for Washington and a research scientist at the 天美影视传媒’s , commented on the summer weather across the state.

“It’s definitely an unusual summer. We’ve been drier than our normally dry, and also temperatures have been warmer,” Bumbaco said.

Washington had its third-warmest summer 鈥� for the months of May, June, July and August 鈥� since 1895. The trend was less the result of heat waves than just a steady, overall warmth.

“While we haven’t had a really extremely hot days, say in the upper 90s in Western Washington, the baseline is so much warmer,” Bumbaco said. “We haven’t seen that many days of cool, cloudy skies that tend to make up a summer in Seattle, in particular.”

A healthy water supply locked in winter snow got derailed by unusual spring and summer weather.

“In the beginning of April, we had normal to above-normal snow throughout Washington state, and that’s really important for our water supply later in the spring and summer,” Bumbaco said. “But beginning in mid-April, temperatures warmed drastically. So that snowpack melted very rapidly 鈥� much faster than usual.”

Summer rainfall was only about 20 to 40 percent of normal for much of the state.

That hit some places harder than others, Bumbaco said.

“Places with reservoirs to hold that water, like Yakima, were able to store that and release it slowly,” she said, for use throughout the summer. But other regions of the state, especially those that rely on summer rain, were experiencing drought conditions by the end of August.

The of the monthly newsletter that Bumbaco produces for the , based at the UW, summarizes the conditions across the state and shows how the 2018 season compared to previous summers on record.

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For more information, contact Bumbaco at 206-543-3145 or kbumbaco@uw.edu.

And if you don’t sleep well in hot weather, this might be a good time to buy a fan, since records show that on average heat waves tend to strike around the last week of July.

天美影视传媒 research shows that the region west of the Cascades saw only three nighttime heat waves between 1901 and 1980, but that number quadrupled to 12 nighttime heat waves in the three decades after 1980, according to a published in the July issue of the .

Nighttime heat waves are when the daily low is in the top 1 percent of the temperatures on record 鈥� in Seattle above around 61.5 F 鈥� for at least three nights in a row.

“In general, minimum daily temperatures have been warming faster than maximum temperatures, so we’re not surprised to see a trend in the minimum events,” said corresponding author Karin Bumbaco, a research scientist at the . “Still, we were surprised to see this significant increase in the frequency of nighttime heat waves.”

She and co-author Nicholas Bond, both with the , began the investigation after fielding questions during the , which broke temperature records and led to a local run on fans and air conditioners. People wanted to know how that event compared with others in the history books.

The two ran the numbers with the help of Oregon State University’s at the Oregon Climate Service. They studied temperature readings west of the Cascade Mountains in Washington and Oregon from 1901 to 2009, looking for instances where the daytime high or nighttime low temperature hit the top 1 percent of readings for at least three consecutive days.

The 2009 scorcher set records in daytime temperature, but it was the string of warm nights that stood out, Bumbaco said. By their definition it was a three-day daytime heat wave in the Pacific Northwest 鈥� but included eight consecutive hot nights, the longest seen in the observational record.

“It was hard to cool down at night, there wasn’t much relief at all,” Bumbaco said.

Researchers also found a clue to suggest why we’re seeing more hot nights. It’s well known that Pacific Northwest heat waves occur when breeze off the ocean is replaced with air flow from the east, which warms up as it flows down the western slope of the Cascade Mountains.

But they found another trait for nighttime heat waves. The records show that nighttime heat waves happen during high humidity, where water vapor in the air serves as a blanket to trap heat.

“Forecasters already do a good job at predicting when heat is coming into the region, but this might help differentiate between hot days versus hot nights,” Bumbaco said.

Predictions are that climate change will bring longer, more extreme and more frequent heat waves during the day and night. The paper found no significant trend in the historical record of daytime events.

Though it was not part of the study, the recent late-June 2013 hot spell included just two extremely hot days, but readings at SeaTac Airport showed it qualified as yet another nighttime heat wave, Bumbaco said.

The study also includes a preliminary look at health effects from heat waves, which in the U.S. account for about 1,500 deaths each year. It found a 50 percent increase in the number of regional hospitalizations coded as being related to heat on dates the authors identified as heat waves. The most heat-related hospital admissions were during the 2009 heat wave and during a 2006 event that had the warmest nights on record. This corroborates other studies suggesting that nighttime heat has the most impact on human health.

Northwesterners are unlikely to draw sympathy from people across the country who are weathering triple-digit summer temperatures. But there is reason for concern. Because the region has mild temperatures people are not acclimatized to extreme heat and, perhaps most importantly, most people do not own air conditioners in their homes.

The research was funded by the State of Washington through the state climatologist’s office.

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For more information, contact Bumbaco at kbumbaco@uw.edu or 206-543-3145.