Sunday, November 23, 2014

Crazy Snow in Buffalo

Friday, November 21, 2014
9:58 pm

We have a bad habit of making a big deal out of the white stuff in Seattle, and it seems to get worse with each passing 'blizzard.' It's all too predictable; the chains on buses strike sparks with the ground as the snow that was seemingly 'promised' by the forecasters never came, schools close due to uncertain snow forecasts (this actually happened in 2008; Seattle Public Schools had a snow day when not a flake of snow fell), and suddenly, snow is the only thing in the world that matters. The last thing is actually nice for a change, but the hysteria that commences in the city is downright laughable.

But my favorite part of the Seattle snow rush is how it gets hyped up by the media. I don't know if it's because the writing staff have decided that their ratings will go up if they are in 'winter storm coverage' days leading up to the event, or if the newscasters just have a competition to see who can more effectively convince the populace that a winter storm of cataclysmic proportions is heading our way. Here's how things usually go down in the newsroom.


Anchorman: "People are scared, and they should be. Snowstorms in Seattle are not only deadly, but dangerous too. The upcoming storm could be the worst we've seen in many, many years."

Anchorwoman: "Flakes were spotted up earlier at Capitol Hill, and although it looks sunny right now, experts say that millions, nay, trillions of additional flakes are on their way."

Anchorman: "People all over Twitter have been talking about the impending storm. iLikeClams says "my pulse is quickening, I hope my increased metabolism doesn't create extra heat to melt any snow coming our way," while No_Umbrellas says "I hate snow, I hope it ends up being rain so I can run in it naked." Lastly, SubaruGurl4Lyfe tweets "I can't wait for the snow! With my Subaru, I'm more prepared than anybody else in Western Washington who doesn't own a Subaru!" Clearly a variety of opinions out there with regards to the snow."

Anchorwoman: "There certainly are! But while opinions are great, we want the facts. With that, let's take it back to our weather center, where our weatherman, Voice Reason, is standing by. So, tell us Voice, how much extra firewood do we need to buy?"

Voice Reason (shaking nervously): "Well, the truth is, there could be snow, or there could not be snow. Most models haven't been showing snow at all, but there is one that has been consistently showing three to six inches of snow over our area sometime tomorrow. It's really hard to know."

Anchorman: "Thank you for that, Mr. Reason. It truly sounds like we are in for a catastrophic event. Hang in there folks, and button down the hatches. And don't die."


In Buffalo, that last sentence would actually hold true.

Buffalo and suburbs to the south are now recovering from the most severe lake-effect snowstorm in memory. 13 people have died. Dozens of roofs have caved in. Parts of the region picked up over 80 inches this week, and even more incredibly, most of that snow fell in one day. A suburb to the south of Buffalo picked up 66 inches (5 1/2 feet) of snow on Tuesday. If you average that over 24 hours, you get an average rate of 2.75 inches per hour, which is hard for me to fathom. There were reportedly times where thundersnow occurred with rates exceeding 5 inches per hour, which is absolutely shocking. For those of you who prefer the metric system, that's slightly over a centimeter of snow every 5 minutes.

Any unprecedented event begs the question: "how on earth did this happen?" Well, as I mentioned before, this snowstorm was of the "lake-effect" variety. But what is lake-effect snow? And how did we get a pattern so conducive to it in the first place?

Bering Sea cyclone on November 8 at its peak intensity. Credit: NASA
Well, do you remember that Bering Sea superstorm that formed out of the remnants of supertyphoon Nuri? That was also a storm of unprecedented strength; it was the strongest extratropical cyclone on record in the Pacific. But this storm did more than cause hurricane-force winds and 50-foot waves, it actually was responsible for pushing a tongue of cold, arctic air into the lower 48, giving the contiguous U.S. its first "polar vortex" of the 2014 winter season. In fact, take a look at what I said from this blog post two weeks ago.

"This storm is so big that it will actually force a pool of arctic air down into the states this week. Yup, that's right. An early-November polar vortex. And you can bet that will be covered, both in the media and on this blog.

Excellent weather forecaster, or supernatural meteorological prophet? I'll let the reader decide.

I actually explained how polar vortices work in my previous blog post, so if you are interested on the physics of those, just read that blog. But now that we've got all that straightened out, let's define lake-effect snow.

Lake-effect snow is snow formed when cold, dry air flows over a relatively warm body of water, picking up moisture and creating clouds and snow downwind as a result. These bodies of water are generally lakes, but lake effect snow has been known to occur over inland seas such as the Caspian Sea, and sometimes it can even occur over the ocean if the winds are aligned correctly. In fact, sometimes Sequim will actually get "Strait-effect snow" when we get especially strong arctic outbreaks as air picks up moisture as it crosses the Strait of Juan de Fuca and runs into the northeast side of the Olympics, rising and creating snowfall as a a result. The bodies of water have to be quite large; your standard holding pond isn't big enough to create any sort of snow. If it were, you can bet that kids all over the midwest would collaborate to build ponds upwind of the superintendent's house.

Lake-effect snow formation. Credit: NOAA Earth Sciences Laboratory.

The air flowing over the lake obtains heat via two methods: sensible and latent heating. Sensible heating is the heating we are all familiar with; if you have a stove top above a column of air, it will warm the air above it. Latent heat, on the other hand, is a function of water. It takes energy to evaporate water from the lake, so when this water vapor turns back into its liquid phase (i.e. where the clouds form), the energy inherent in the water vapor is then re-released, warming the atmosphere.

These two processes combine to make strikingly beautiful "cloud streets" such as the ones shown in the satellite picture below, which was taken on Tuesday the 18th at the height of the lake-effect snow-storm. Notice how it is clear upwind of the lakes, yet clouds form as soon as the air flows over them. Additionally, the flow is nearly parallel to lakes Erie and Ontario, meaning that a ton of moisture was able to have been suctioned up by this cold air. This, combined with relatively warm temperatures due to the early-season nature of this event and an extremely persistent, stationary flow, was responsible for the historic snow amounts witnessed in Buffalo.

Cloud streets over the Great Lakes on November 18, 2014. Source: NOAA

Buffalo is forecast to experience springtime warmth over the next week. While this may seem welcome after such snowfall amounts, it's actually the last thing they need, as the warm temperatures will quickly melt snow. Roofs have already collapsed due to the immense weight of the snow on top, and this melting make the snow more dense and compound the problem. With five feet of snow turning to water, you can definitely expect a lot of ponding and flooding in regions that were particularly hard hit.

I'll leave you guys with some pictures of the snowmageddon to gawk at. Brace yourselves.

I think it's going to be a long day. Credit: Empire State College

And the Buffalo Bills actually thought they were going to play here this Sunday. Credit: Buffalo Bills

I don't even know what these things are. The Spectrum - University of Buffalo's Student Newspaper

And of course...

If you've ever wanted to build one of these guys, now's the time.


Monday, November 10, 2014

The Polar Vortex - Winter is Coming

Monday, November 10, 2014
12:39 pm

I think the above meme explains all you really need to know about the weather this coming week. But since I am a kind and merciful weatherman, I shall oblige your curiosity and explain the meteorological situation that has led us to our first real chill of the winter.

But first let me explain what a "polar vortex" is. This catchphrase became quite the buzzword last year as all sorts of media dished it out like free miniature Bibles. Professor Rush Limbaugh took it upon himself to define the polar vortex, seemingly settling the hysteria once and and for all.

"So, ladies and gentlemen, we are having a record-breaking cold snap in many parts of the country. And right on schedule the media have to come up with a way to make it sound like it's completely unprecedented. Because they've got to find a way to attach this to the global warming agenda, and they have. It's called the 'polar vortex.' The dreaded polar vortex."

"Do you know what the polar vortex is? Have you ever heard of it? Well, they just created it for this week."

"Now, in their attempt, the left, the media, everybody, to come up with a way to make this sound like it's something new and completely unprecedented, they've come up with this phrase called the 'polar vortex.'"

And here's my favorite part.

"Whatever it is that keeps the polar vortex vortexed in the Arctic Circle is vanishing, and that cold air is coming to us. Normally it stays up there. But now it's down here. How did it get here? That's the deepening mystery. That is the crisis. That is what is man-made. Man is destroying the invisible boundaries that keeps that air up there.

"Polar vortex vortexed." Good one Rush. The fact is, the polar vortex was not just created in the last week. In fact, the term has been alive and well for over 50 years. 

The polar vortex is a persistent cyclone that encircles either one of Earth's geographical poles in a cyclonic fashion (in the same direction as low pressure systems; counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere). They are usually less than 1,000 km in diameter, and their strength depends on the temperature gradient between the poles and midlatitudes. As such, the vortices are stronger during the winter than the summer, as the temperature gradient between the poles and midlatitudes is greatest at this time. 

It can be a little bit tricky to explain just in terms of words, so hopefully the picture below help you understand.

Northern Hemisphere Polar Vortices. Source: NASA Earth Observatory

Vorticity is an advanced concept, but it can be thought of as the tendency for a an air parcel to spin, with higher values responding to higher tendencies. Therefore, the higher the the vorticity, the stronger the polar vortex. The diagram above shows how a singular polar vortex over the North Pole weakens and breaks down into two separate vortices. When this happens, one of these vortices can slide south and bring a whole bunch of cold air that had been previously been stored up near the poles with it. 

The below diagram gives a general idea to how a part of the polar vortex gets cut off from the main circulation by the pole, bringing frigid air southward with it.

Schematic of the formation of an arctic outbreak in the Northern Hemisphere. Source: Wikipedia.

So, now, we've got a general idea of what the polar vortex is, and how it works. So what's gonna happen this week?

It turns out we are actually going to see an event like the one illustrated in pictures a, b, and c above. Take a look at the model chart below, and you'll see what I mean.

Retrieved from Supercell Weather

The colors represent the "thickness" in decameters of the atmosphere, which is a function of the overall density of the atmosphere and therefore the temperature via the ideal gas law. Take a look at how much lower the thicknesses are over much of the United States than areas much further north, with Southern Canada having particularly low thicknesses. This, right here, is the "polar vortex" that has been cut off from its 'parent' circulation up by the pole. Some of this cold air is actually infiltrating into Washington and even Seattle, and we will see our first freeze of the region Tuesday night. Models had been flirting with snow in the Portland region, but for now, it looks like any snow will be confine at and east of the Cascades, particularly near the Columbia Gorge. 

In the extended, we'll have a ridge of high pressure off our coast that will close the door to the the Pacific storm train that has been open for so long. We look to be relatively dry for the foreseeable future. Enjoy the break!


Sunday, November 9, 2014

A Historic Storm

Sunday, November 9, 2014
5:04 pm

Every once in a while, a storm so unbelievably massive, so breathtakingly powerful, and so horrendously destructive appears in the models that you literally go into cardiac arrest.

This is one of those storms.

I've seen many crazy, crazy storms in the models. I've seen gigantic 930 hPa "bombs" in the Gulf of Alaska, over a foot of snow in Seattle in 24 hours, sustained winds of over 50 knots in the foothills of the Cascades... you get the idea. None of these scenarios came true. The 930 hPa lows nearly always appear in the far extended and never develop, and the snow is notoriously hard to predict. The only time I can remember the foothill winds being forecast to be this strong was on December 20, 2008, with one of our legendary winter storms then. North Bend hit 57 mph, Enumclaw hit 70 mph, and the foothill town of Cumberland hit 100 mph, but this was nowhere near as bad as the forecast widespread, 50+ knot sustained winds (credit to Scott Sistek for these statistics, you can find his article on the storm here).

On Friday, one of the strongest storms in recent memory hit the Aleutians. This low was fed by the remnants of supertyphoon Nuri, which, at its most intense point, had a minimum low pressure of 910 millibars and sustained winds of 185 miles per hour. For comparison, Hurricane Katrina had a low pressure of 920 millibars and sustained winds of 125 miles per hour when it made landfall on the Louisiana Coast.

Supertyphoon Nuri at maximum strength

The Western Pacific is the the most active tropical cyclone basin in the world, and storms like these occur with almost disturbing regularity. However, what they generally do not do is travel northward to become super-ultra-mega storms in the Bering Sea, and that's exactly what this one did.

Track of Nuri.

Thankfully, when Nuri was at category 5 strength, it was far out in the Pacific and did not cause any injuries or deaths. As it began to head northward and dissipate, it was absorbed by an extremely strong jet stream off the Siberian coast. This jet stream had winds in excess of 210 knots, which is simply extraordinary. It was the strongest jet I've ever seen, regardless of location.

This jet stream provided the storm with the large horizontal temperature gradient needed for serious development, and with a ton of tropical moisture already in place from the remnants of a supertyphoon, a storm of the likes the Bering Sea had never witnessed before was formed.

Surface Analysis over the North Pacific on Saturday morning. Credit: NWS.

The analysis above of the storm at peak strength gives an idea of the the depth and breadth of the storm, but it's so far beyond anything that I have seen before that it is seemingly beyond my comprehension in many ways. It bottomed out at 924 millibars, which is deeper than any extratropical low ever for the Northern Pacific. It spanned over 2,000 miles (just look at how long that cold front extends outwards), and it created waves over 50 feet high in the Bering Sea. Our Hanukkah Eve Storm was around 976 millibars when it made landfall on the night of December 14, 2006, and cut power to millions while giving Sea-Tac its all-time highest gust of 69 mph. The thought of a 924 millibar storm hitting our region is, while impossible in our current oceanographic, geographic, and atmospheric setup, is truly frightening.

The infrared satellite picture above taken Saturday morning gives you an idea of the scope of the storm. The storm covers much more latitude than the United States. A snapshot of the wind field of the atmosphere at the same time reveals that the highest winds are just to the north and just to the south of the low, with an "eye" of calm winds right where the low is located, not unlike Supertyphoon Nuri itself.

Because this storm his such a remote region and caused very little damage as a result, it was not widely covered in the media. I feel as though it definitely should be though, as it is one of the most fascinating occurrences we have seen in the atmospheric sciences for quite some time. Instead of learning about violence in the Middle East, it sure would be nice to learn about the power that Mother Nature has manifested in this storm.

Oh yeah, one more thing. This storm is so big that it will actually force a pool of arctic air down into the states this week. Yup, that's right. An early-November polar vortex. And you can bet that will be covered, both in the media and on this blog.

Thanks for reading!

Tuesday, November 4, 2014

My Winter Weather Outlook

Tuesday, November 4, 2014
6:02 pm

Hey everybody, I actually just produced a winter weather outlook for WeatherOn, and you can find it here. Long story short, our weak El Nino played a major role in my forecast, and the previous existence of the "Blob" did to a lesser extent.

Snow in Eugene