Friday, October 2, 2015

Another Heat Record Bites The Dust/Thoughts on The Blob

Thursday, October 1, 2015
4:08 p.m.

"It ain't the heat, it's the humility" - the late, great Yogi Berra

At Sea-Tac, the last time we had a month that was cooler than average for that month was February 2014. Since then, 20 months have passed, with 19 consecutive months being warmer than normal. That's right... this September was the first colder than normal month since February 2014.

We've broken some impressive records in that time. Our records to Sea-Tac go back to January 1948, but within the span of these months, we've broken two all-time records for hottest months (March 2015 and June 2015). In addition, December 2014 and June and July 2015 broke records for all-time highest maximum temperature, and October 2014 and February, March, June, and July 2015 broke record for all-time highest minimum temperature. In other words, these 19 months weren't just warm, they were scorching!

Why so warm?

Two answers: a massive and persistent ridge of high pressure, and a larger-than-life blob of boiling-hot (OK, maybe not that hot, 2-3 degrees warmer than normal) water in the Northeast Pacific. With this ridge, instead of getting cool, northwesterly flow from the Gulf of Alaska and places to the Northwest, we got warmer flow originating from our south, and our surface winds were often offshore, further warming us due to downslope adiabatic warming effects off the Cascades (that's fancy terminology for the phenomenon of air warming as it sinks). With the warm water, onshore flow off the Pacific into our region was often at least 2 degrees higher than it would have been due to the long time it spent over the Blob of warm water. 

The picture above shows our sea-level-pressure compared to normal values, and you can clearly see that we had higher than normal pressure this summer. As you can see, we clearly had higher than normal pressure over the Northeast Pacific this year.
This ridge of high pressure was associated with relatively little mixing of the ocean, so the surface got nice and warm instead of having this warmth being mixed down deep by storms and waves. Also, these ridges are associated with sunny skies, so the sun heated the ocean.

I was unable to find out how to get a similar chart to this for sea surface temperature (SST), but as you can see from the February-March 2015 SST anomaly chart below, the "Blob" is located in the same area that the higher-than-normal pressure is located. This is not a coincidence! The Blob is a direct result of this higher-than-normal pressure.

As you can see below, the Blob wasn't just present in 2015. It was there in 2014 too; in fact, that is when it was first named. It was a bit further west, and a bit more "blob-like" then (at least in my opinion).

Credit: NOAA Earth Systems Research Laboratory: Physical Science Division

So, why did this persistent ridge of high pressure (and the resulting Blob) occur? There's been a lot of study concerning it, particularly at the University of Washington, where Professor Nick Bond (great guy, had him for my senior capstone forecasting course spring quarter) first came up with the "Blob" name. It turns out that the high pressure looks to have originated from atmospheric waves originating from the western Pacific. On a larger time scale, the Pacific Decadal Oscillation, an oscillation in Pacific Ocean temperatures on 20-30 year time scales that has atmospheric implications, may be a factor. Finally, some studies like those by Diffenbaugh et al. (2015) have hypothesized that we will see more of these "Ridiculously Resilient Ridges" and therefore Blobs in a warming climate. This is likely due to a weakening meridional temperature gradient, as the poles (particularly the North Pole) are warming faster than the tropics and midlatitudes. This creates a weaker "polar vortex" (yes, the infamous vortex you hear about on CNN) and allows strong ridges of high pressure to occur in some regions while other regions have large troughs and arctic outbreaks. When the vortex is all wavy like this, it is weak and in a "highly amplified" pattern. I know amplified = more powerful most of the time, but in this context, it refers to a lot of ridging and troughing. A strong, non-amplified polar vortex is said to be "zonal." And yes, our record breaking heat and the eastern U.S.'s record breaking cold as of late are directly related... we've had the ridge, and they've had the trough.

Thanks to the strong, potentially record-breaking El Nino, the Blob is pretty much toast, and our winter won't be as warm as last winter. I don't think we'll have 19 consecutive months of above average temperatures soon, but as we go further into the 21st century and really start to feel the effects of global warming, we'll shatter more and more heat records. Someday, air conditioning may be a standard feature for Seattle homes. That’ll probably have to do more with our rapidly growing economy than rapidly warming climate though.

On that happy note, enjoy some cooler weather. Sunday should be beautiful, but we should have typical early October weather for this time of the year this coming week. Come late October, things will start to feel a lot different. The transition to storm season is a lot more abrupt than the transition out of it!

Thanks for reading,

Sunday, September 27, 2015

A Supermoon Lunar Eclipse!

Sunday, September 27, 2015
6:03 pm

Credit: NASA

We've all heard of supermoons... after all, we've had three of them this year. The same goes for lunar eclipses... we had one this past April. They are both fascinating events.

But what if you were to combine the largest supermoon of the year with a total lunar eclipse?

I had known about this for several weeks, but realized the true scope of the supermoon last night as I was heading towards a gig with my funk band up in the University District. As I walked along the Ave, I noticed a massive moon up in the sky. I could not ever remember seeing a bigger and brighter moon. It turns out that it is going to be even bigger tonight, and blood-red as well. 

Credit: Courtney Seligman

Lunar eclipses happen when the Earth is positioned in front of the sun such that it blocks the moon from receiving direct sunlight. Instead, the moon is positioned in the "umbra" of the Earth, meaning is fully shadowed from the sun. However, it doesn't appear black (and hence invisible) because light from the sun scatters off the Earth's atmosphere and hits the moon, giving it a reddish tint.

"Supermoons" occur because the moon has an elliptical orbit, meaning that it is closer to the Earth at some times during its 27-day orbit than others. When one of these close points corresponds with a full moon, you get a supermoon!

To get both of these occurring at once is exceedingly rare. The last supermoon lunar eclipse occurred in 1982, and the next one will occur in 2033. So enjoy tonight!

Luckily for us, the viewing conditions for tonight will be absolutely perfect. The air quality is great, the air is relatively dry, and there are no clouds in the sky to muck up viewing of this historical event. The model picture below measures outgoing longwave (infrared) radiation and simulates an infrared satellite image. As you can see, there are NO clouds over our region. Pretty awesome!

Valid 08:00 pm PDT, Sun 27 Sep 2015 - 15hr Fcst: Retrieved from UW Modeling Website

The partial eclipse is now underway, and the total eclipse will be here within a half hour. We're lucky... if the eclipse was a little sooner, it would still be light out and would not be nearly as stunning. The times below are in Greenwich Mean Time, so just subtract 8 hours to get PDT. For example, the full lunar eclipse starts at 7:11 pm and ends at 8:23 pm.


Enjoy this unique phenomenon, and take some pictures! I know I will!


Thursday, September 17, 2015

A Megathrust Earthquake And Tsunami off Chile!

Thursday, September 17, 2015
1:24 p.m.

The port town of Coquimbo, Chile after the earthquake and tsunami. Credit: Wikimedia User Sfs90

Chile is hands-down the most active place in the world when it comes to megathrust earthquakes. Three of the past six megathrust (subduction zone earthquakes over moment magnitude 8) earthquakes have been in Chile, and one of those three that was not in Chile was in Peru (the others were the 2004 Indian Ocean Earthquake/Tsunami and the 2011 Japan Earthquake/Tsunami). Heck, they had an 8.2 earthquake just last year, and a 8.8 earthquake back in 2011. Here in Cascadia, we are frightened (and rightfully so) about a mega-quake that occurs once every 200-700 years. But Chile's gotten three magnitude 8+ of those quakes since 2001! We haven't had one of those quakes since 1700.

Their most recent quake struck 29 miles west of the Chilean city of Illapel. This is a very seismologically active region even for Chile; 15 7+ magnitude earthquakes had struck with 400km of this area within the last century prior to yesterday's earthquake. It was an 8.3 earthquake, so while it was powerful, it was not the same magnitude as the aforementioned Japan or Indian Ocean earthquakes. The moment magnitude scale is a logarithmic scale, meaning that the energy released by an earthquake increases exponentially with linearly increasing magnitude. For example, a magnitude 9 earthquake is not three times as powerful as a magnitude 3 earthquake... it is a billion times more powerful! If you ever want to compare earthquake magnitudes, the ratio between the energy released due to earthquake 1 and earthquake 2 = 103/2(Magnitude of Earthquake 1 - Magnitude of Earthquake 2). Nothing wrong with a little math to keep your brain nice and fresh! Using that calculation, it was about 11 times less powerful than the 9.0 2011 earthquake of the Pacific coast of Japan, so while it wasn't as powerful as some of the powerful quakes of years past, it was still pretty darn powerful... nearly 6 times more powerful than the catastrophic Nepal earthquake we saw earlier this year.

Source: Environmental Physical Geography

Just like all of the other Chilean megathrust earthquakes, this earthquake was formed by the subduction of the Nazca Plate under the South American Plate. As this subduction occurs, certain places become "locked" due to friction and can no longer undergo the subduction process. Below this locked zone, however, warmer temperatures make the plates less rigid, allowing them to continue to slide past each other. As this occurs, stress builds up along the locked zone, and when the stress exceeds a certain threshold, all of the energy is released and a massive earthquake ensues, often accompanied by a tsunami.

Source: Cascadia Region Earthquake Workgroup

The reason why Chile gets so many of these violent earthquakes is because the rate at which the South American Plate is subducting the Nazca Plate. The faster the rate of subduction, the more stress builds up in a certain amount of time, and the more frequent the earthquakes. The South American Plate is moving westward at 10 cm/year, and the Nazca Plate is moving eastward at 15-17 cm/yr, giving an approximate subduction rate of 26 cm/yr (Monroe & Wicander, 2006). In comparison, the Cascadia fault has an approximate subduction rate of 4 cm/yr (Cascadia Region Earthquake Workgroup, 2013). 

Now, let's move on to the actual earthquake at hand!

Source: USGS Earthquake Hazards Program

The USGS map above shows the Mercalli intensity Scale, which is a qualitative measurement and measures the intensity of the earthquake, unlike the moment magnitude scale which is a quantitative measurement and measures the total energy released. The intensity of an earthquake is dependent on many factors and can vary substantially from one region to another, but one of the biggest things that it is dependent on is the depth of the earthquake. If you have a 8.0 earthquake 600 miles deep, there will be no damage. However, if you have an 8.0 earthquake right at the surface, the damage will be catastrophic. With a depth of 15 miles, this earthquake was comparable to depth to other recent megathrust quakes.

As you can see, strong to severe shaking was reported over a very large area. Even in Buenos Aires, some 690 miles away from the epicenter, buildings swayed and car alarms were spontaneously set off. People even reported shaking in São Paulo 2,100 miles away. That's the same distance as New Orleans is from Seattle!

And let's not forget about the tsunami.

Boats stranded in Coquimbo after the tsunami. Credit: Wikimedia User Sfs90

Due to this "only" being a magnitude 8.3 earthquake, it did not have the massive tsunamis that the Japan and Indian Ocean earthquakes had. However, it still sent a 15-foot wave to Coquimbo, stranding boats and flooding parts of port city. Over a million people have been ordered to leave their homes in Chile due to the tsunami and earthquake, and hundreds of thousands around the Pacific have been ordered to evacuate. A tsunami advisory was actually posted by the National Weather Service for Southern California for waves less than one foot in height, but it was later cancelled.

The National Tsunami Warning Center issues these awesome "propagation forecasts" after these earthquakes occur. Look at how the energy is not distributed evenly; there are little filaments of higher wave energy scattered within the overall wave dispersion. You may see the low wave height values and say to yourself: "I thought this wave was one foot when it hit L.A. Why does the map show it as less than five centimeters?" Well, the answer is that this map shows the height of the tsunami as it travels through the open water at 500 mph. As the waves approach the shore, they slow down considerably and increase dramatically in height.

Source: National Tsunami Warning Center
The physics of tsunami propagation. Credit: Régis Lachaume

One of my favorite things to do after these events is look at tide gauges. Even though it is very unlikely that anybody in southern California observed the tsunami, the tide gauges definitely reported it. Let's take a look at some! By the way, all these charts (and many more) can be found at NOAA's Tides & Currents website.

Santa Monica reported a 0.7 wave. But how about some other locations around the U.S.?

Hilo Bay, much more exposed to the tsunami, saw a 5'11" drop in sea level today as the waves raced 455 mph across the ocean. Impressive. 

Even the Washington coast saw some action! Take a look at La Push. You can clearly see fluctuations in water level from the tsunami occurring this afternoon.

Of course all of this pales in comparison to Coquimbo. 

One thing to take away from all these gauges is that the first wave often isn't the strongest, you don't always experience the ocean receding before the first wave, and tsunamis can last for hours. If you live in a tsunami-prone zone, as soon as you feel shaking, evacuate to high ground, and stay there! Even if you don't feel shaking, it's always important to be aware of any tsunami advisories or warnings, as earthquakes thousands of miles away can still send devastating tsunamis into certain locales where the sea floor amplifies incoming waves. Crescent City, a coastal city situated in Northern California, was devastated by a deadly 20 foot tsunami due to the Good Friday Earthquake of 1964. Even the 2011 Japan earthquake sent an 8 foot tsunami to the harbor, killing one person.

At some point, we will get a megathrust earthquake off our coast. It might be five seconds from now, and it might be 500 years from now, when the world is 900 degrees and we all have the same color hair. But it's crucial that we prepare by rebuilding our infrastructure and having better disaster management/evacuation strategies, because the longer we put off dealing with those things, the bigger a hole we are digging ourselves in the future.

On that note, have a nice evening!

Our Beloved Salmon

Tuesday, September 15, 2015
2:27 pm

Spawning Coho Salmon on the Sol Duc River. Credit: National Park Service

Things were never looking good for our beloved salmon this year. I've been a fisherman all my life (I actually just got back from catching a bunch of albacore tuna off the Washington Coast), so I care quite a bit about how our salmon are doing. First and foremost, they are some darn tasty creatures, but they are also super fun to catch, and I think there's something special about a fish that leaves a river, travels thousands of miles in a couple years, and then heads right back to that same river. Salmon are one of nature's most fascinating creatures... and for a fish, that's saying something!

The problem, of course, has been our rivers. The journey upstream can be very tough, as salmon often have to navigate strong currents and rapids. Therefore, it is essential that they have water temperatures that are cold enough for them to not get exhausted and water levels that are high enough so that they can migrate upstream in the first place. The two are closely related; when the water is high, it means that there is a lot of cold freshwater input either from remaining snowpack, rainfall, groundwater, melting glaciers, lakes/reservoirs, or other sources. When the water is low, it is more easily warmed by the surrounding atmosphere both because there is less water to warm and the currents are often slower, meaning that the water takes more time to get to the ocean and thus has more time to warm.

Salmon prefer temperatures between 46 and 59 degrees. Once you get above this, they get tired more easily, as warmer water holds less oxygen, resulting in a variety of negative effects.  

Credit: Willamette Riverkeeper Volunteer Monitoring Program

Salmon, like many other of Earth's wonderful creatures, don't want to die. Therefore, if they sense that the river they are about to enter is, according to the Environmental Protection Agency, at least 66.4 degrees, they wait at the mouth of it for it to cool off. This can be great for fishermen at that moment, but it can throw off the salmon's cycle, making it a more difficult experience when they do go up. Think about how you would feel if you had a reservation at your favorite restaurant, but then you found out they COMPLETELY overbooked, and that you had to wait outside... for several weeks.  

I took a look at our current (9/16/2015) streamflows according the United States Geological Survey compared to average for this time of year (see them here), and found that only 29 of 226 stations in Washington had above-average streamflow. When you consider that our August was the 4th wettest on record and September has had near-average rainfall, that's pretty sobering. Ironically, one of the few rivers that is flowing higher than normal in many locations is the Columbia, which happens to be the biggest river flowing from North or South America into the Pacific. This is likely because its headwaters are located in inland British Columbia, which actually accumulated a decent snowpack this past winter. Also, the Columbia River is heavily dammed, so they are able to control how much water flows downriver. Unfortunately, this table did not have average temperatures, but some locations did have temperature measurements for the day. Most of the river temperatures were between 50 and 59 degrees, but many locations in large rivers like the Columbia and Snake were slightly above that 66.4 degree threshold. This is common for these large rivers, but if the temperatures were just a little bit higher, the fish would still be hanging out in the ocean.

So how are the fish going to fare this year as they go up to spawn? It really depends on the river. The Columbia River is forecast to have their third-largest return of Chinook salmon since 1938 and their water levels are near normal, so they should be fine. It's a different story for rivers in the Cascades and Olympics with our record-low snowpack and record-high temperatures. By the way, 6 of our past 11 months have been the warmest on record. And before anybody jumps to conclusions, it's because of our "Blob" and a persistent ridge of high pressure off our coast, not global warming. Global warming has an underlying impact that further raises temperatures, but it was not the principal reason why we broke so many records this year.

But back to our salmon. With the exception of the Skagit (which also has dams), our local rivers are much lower than normal. For example, the Middle Fork of the Snoqualmie River near Tanner was measured today flowing at 120 ft3/sec. There typical flow for this time of year is 549 ft3/sec. The Hoh River, a river on the Olympic Peninsula that gets most of its water from glaciers on the flanks of Mt. Olympus, was flowing at the rate of 519 ft3/sec today near Forks. Average for this time of year? 1,200 ft3/sec. It gets even worse when you go up north by Bellingham, where Anderson Creek's flow is 15 times less than its average.

The Hoh River. Note the blue tint due to the presence of glacial silt. Photo credit: Flickr user "Thomas"

The story is similar everywhere you look. The vast majority of rivers in the Pacific Northwest are much lower than normal and have been for the majority of the summer. 

There's also another factor: the presence of feed in the ocean. I am not a marine biologist, so I have no clue how abundant the feed for salmon has been this year. However, I do know that the amount of feed is directly related to the amount of nutrients in the water, and the amount of nutrients in the water is related to how much upwelling occurs along the coast. El Niño years generally have less upwelling than normal, thus limiting primary productivity and decreasing the amount of animal life that portion of the ocean can support. I don't know if the infamous Blob of warm water in the northeast Pacific affected the salmon, but it probably resulted in less primary productivity way out in the open ocean, as warmer ocean temperatures imply less mixing and therefore imply a more sterile ocean surface.

In conclusion, we've got a number of factors working against salmon this autumn all the way into next spring. This August was a tremendous help, and the additional rain we will see through the end of the month into October will help as well. 

But the tuna fishing's great!

Thanks for reading,

Tuesday, September 15, 2015

My Fall Forecast

Sunday, September 13, 2015
5:19 pm

If you ask an astronomer when summer ends, they'll tell you "September 23." That is the date of the autumnal equinox, the date when the day and night are approximately equal in length (the day is always a couple minutes longer because the sun does not set all at once and therefore radiates light until the very last part of it has set below the horizon). Ask a meteorologist though, and they'll tell you that autumn begins September 1, as that is the beginning of 'meteorological autumn,' which goes until November 30. During this time period, our nights get longer while our days get shorter, our daytime and nighttime temperatures plummet, stronger storms start to enter the region, and people become more and more obsessed with the Seahawks. Our earliest lowland snows have generally appeared the last two weeks of November, and our stormiest week is Thanksgiving week. I will have an exclusive winter 2015-2016 forecast on WeatherOn that will be released November 1, so be on the lookout for that. For now, I thought I'd give a more informal autumn forecast.

This has been one of the more abrupt summer-to-fall transitions that I can remember. June and July both broke their respective all-time average temperature records and were extremely dry as well, while August was our 4th wettest month on record and was capped off by a historic windstorm at the end of the month.  Now, it's mid-September, and according to the National Weather Service, showers or rain are forecast for the area for the entire week, and highs likely will not reach 70 in many locations.

We've gone from a pattern of persistent ridging directly over our area to one of persistent troughing, with the ridge having retrograded much further west. Now, storm systems and "shortwave troughs" are undulating on the east side of this ridge and sliding down from the northwest into our area, giving us cooler temperatures and precipitation than anything we experienced during June, July, and even much of August.

Valid 05:00 am PDT, Mon 14 Sep 2015: Retrieved from UW Northwest Modeling Website

So far, this pattern has been pretty consistent. Will the mega-ridge return? I don't think so. That isn't to say we won't have some sunny days, but we won't be seeing the mid-80s until 2016. In fact, we may be done with the 80s for all of 2015. Time will tell.

I'll get into a brief month-by-month breakdown soon, but first let's take a look at some of the major factors that are influencing my forecast. The main factor I'm looking at is El Niño, not only because it is an incredibly influential phenomenon for our weather around here, but because this El Niño could end up being the strongest El Niño ever recorded, perhaps even surpassing the 1997-1998 El Niño. Right now, sea-surface-temperatures in the tropical Pacific are around 2 degrees Celsius above normal in the "Niño 3.4" region, which is the region of the eastern/central tropical Pacific that is most telling for the status of an El Niño. In addition, the trade winds have weakened and convection that typically forms over Indonesia has shifted westward, two things that are also consistent with a strong El Niño.

El Niños tend to give warmer temperatures and drier conditions to northern states and cooler temperatures and wetter conditions to southern states. These effects are most pronounced in winter, when El Niño is typically strongest. However, this pattern manifests itself at many other times during the year. During the spring, we had a persistent trough off southern California that not only gave them desperately-needed rainfall but gave us quite a bit of lightning, especially over the Cascades and in Eastern Washington.

Credit: University Corporation for Atmospheric Research

But remember... just because you have an El Niño does not mean that the above scenario will come true. It only means that the probability of it becoming true is higher. Also, just because a location is forecast to be warmer and drier than normal does not mean it can't have any cold and wet days. This week doesn't exactly look "warm and dry" to me.

SST Anomalies 9/14/2015. Retrieved from NOAA Office of Satellite and Product Operations (OSPO)

I'm also looking at the "Blob," which is an area of anomalously warm water in the Northeastern Pacific. The Blob was quite strong during the summer, but with the cool and wet weather the past few weeks, it has decreased in ferocity. I predict that El Niño will ultimately destroy the Blob due to increased storm activity into California, but it is still around for now and will influence our weather by warming us up slightly. I could look at the Pacific Decadal Oscillation and many other oceanic and atmospheric factors, but with the El Niño being so obscenely strong, it should overwhelm any of those other factors, including our beloved Blob. Just take a look at the SST anomalies right now in the tropical Pacific. Incredible.


September is halfway complete, so we don't need to use El Niño to try and predict what you should wear on Wednesday (you should wear a raincoat!). The models are painting a cool and rainy scenario for us the next two weeks... the above forecast provides evidence of that for this upcoming week, and the graphic below shows that we are expected to see below-normal temperatures and above-normal precipitation next week as well.


Our longest range deterministic global model, the GFS, has been consistent in keeping our current pattern, with a ridge offshore and trough over the Northwest. As a result, we will likely start off cooler and rainier than normal. However, El Niño will continue to strengthen, and as a result, our precipitation and temperature patterns will likely begin to resemble those found in the strongest of El Niños, meaning southern regions like California and Texas will be wetter and cooler than normal while we will be warmer and drier. I should note that the precipitation signature over our region with an El Niño is weaker than the temperature signature, so while I am confident that the late autumn and winter will be warmer and drier for our region (the models have been advertising this for a long time), I am less confident about the precipitation than the temperature.


By this time, El Niño has kicked into overdrive. We will almost certainly be warmer than normal, and we will probably be drier than normal as well. November is our stormiest month, and El Niño years tend to bring less of the big storms, so it is less likely we will see one of those. It's also less likely we will see any of those early lowland snows I was talking about. I'm making it out to be a pretty lame month for us weather-wise, and it very might well be. But I want to emphasize this: it is unlikely that this winter will be as warm as last winter. Last winter was crazy warm, and our snowpack paid the price. The culprit? A consistent ridge of high pressure, pushing our storms to the north and leaving the entire West Coast warm and sunny. That is not predicted to happen this year. Even during the record-breaking 1997-1998 El Niño, snowpack was 70-80% of normal throughout most of the mountains here. Last year, our snowfall was around 25% of normal, with some places in the Olympics not breaking 10%.

Remember... I'm talking about anomalies here. It's gonna be colder in November than the last two weeks of September. But compared to average, the last two weeks of September will be colder than normal, while November will be warmer than normal.

Thanks for reading! If you like this, be sure to look out for my winter forecast, which is truly a deluxe blog. And you'll only find it on WeatherOn.