Thursday, January 28, 2016

Unstable Air, A Convergence Zone, And An AMAZING Satellite Picture

Thursday, January 28, 2016
9:10 pm

Image taken at approximately 12:00 pm  1/28/2016
Credit: NASA Terra MODIS Satellite

Apart from an extremely rainy morning for many folks, today ended up being a pretty nice day. Our atmospheric river that had been giving us so much rain, wind, and warm temperatures finally sagged to our south as cold front, and in its wake came cool, unstable, and rather moist air. Although pressure gradients relaxed somewhat, things were definitely still gusty, and the amazing satellite picture above shows that. Let me explain.

I got this picture from NASA's MODIS satellite imagery page. MODIS stands for "moderate-resolution imaging spectroradiometer," and it is a very expensive instrument installed on two NASA satellites: the "Terra" and the "Aqua." These two satellites are called "polar orbiting satellites" and orbit the Earth around the poles. Most meteorology satellites orbit the equator in sync with the Earth's rotation so they can take shots of the entire Earth at any given time, but polar orbiters have to take a single, continuous image as they circle around the poles. It takes around 99 minutes for these satellites to orbit the poles, and each one can only take one picture of a certain region per day. However, these polar orbiters can come much closer to the Earth than the ones over the equator, and when they pass over right as an awesome weather event is occurring, you can get some sensational pictures.

The cold front has just passed Western Washington, and is now over the Cascades. If you look really carefully, you can see the actual cold front as a very thin discontinuity in the cloud cover centered over the Cascades and curving very slightly as you head north. Ahead of this front, winds were primarily from the south, but behind it, winds were from the west. This buoy near Destruction Island shows a very sharp change in pressure, wind speed, and direction following the passage of this morning's front.

Credit: National Data Buoy Center
Credit: National Data Buoy Center

With strong, westerly winds and cool, unstable air in the wake of the front, air flows off the Pacific, and, after encountering terrain, is forced to rise, with clouds and precipitation resulting. On the other hand, places on the leeward side of terrain in westerly flow, like the Willamette Valley and the Southeastern portion of Vancouver Island, remain relatively cloud-free due to air sinking as it comes off terrain.

However, there is one place that is directly behind a mountain range and is NOT cloud-free. And that's our trusty Puget Sound convergence zone. The zone forms because winds, like all of us in life, would rather avoid obstacles than fight an uphill battle. Therefore, they split around the Olympics and "converge" right over Puget Sound! This time, they do rise, forming clouds, precipitation, and even the occasional thunderstorm in the process.

Even though the zone looks pretty intense on that satellite picture, it didn't really get going until later in the afternoon. Remember, that satellite picture was taken right after the front passed Western Washington, and even though it is extremely impressive that the convergence zone formed that quickly, it really ramped up as the afternoon went on. Take a look.

Credit: University of Washington

This radar image was taken at noon, which is close to when the satellite picture above was taken. You can see some weak convergence, with showers over Vancouver Island. This image is from the Camano Island radar, so there is blockage by the Olympics.

Credit: University of Washington

Three hours later, the zone is much more intense. There are even some reds in there!

Credit: University of Washington

By 4 pm, it has moved over northern Seattle. Red indicates very heavy rain.

Let me leave you with one thing before I sign off for the night. I'll repost the satellite picture here for convenience.

Image taken at approximately 12:00 pm 1/28/2016
Credit: NASA Terra MODIS Satellite

To the north and south of the convergence zone, the skies are blue as can be. The reason is because after the air has finished rising, it diverges and sinks on either side, creating bluebird skies in the process. It's great for basking in the sunshine while your neighbor's house gets struck on lightning, and it sure makes for some great satellite pictures.

Thanks for reading!

Wednesday, January 27, 2016

An Atmospheric River Fiesta

Wednesday, January 27, 2016
1:41 am

Yesterday, I wrote about the Eastern third of the country and how much of that region was profoundly affected by a major blizzard that halted over 13,000 flights and caused 3 billion dollars in damage. Now, the weather action has shifted back to our neck of the woods, and while we won't see anything historic over the next week like what was witnessed in some states back east, the entire West Coast looks to get a pretty good soaking this week.

I've used the term "atmospheric river" a lot, and that's because we get a lot of them. This week will be an atmospheric river fiesta not only for Washington State but for the entire West Cost. The first of these rivers will impact us tonight into Thursday, and with snow levels above 7,000 feet, flooding is possible on many of our rivers. The Skokomish will certainly flood and could reach major flood stage. Models have trended a bit lower with precipitation amounts here in the lowlands mainly due to the atmospheric river staying trending further north in the models, but the Olympics and North Cascades are expected to get several inches of rain within a few hours. When you have that amount of rain in such a short time combined with high freezing levels and rivers that are already running high, you've got a recipe for flooding. Contrary to popular belief, a healthy snowpack like the one we have now actually decreases flooding concerns because it helps absorb water and prevents it from all flowing into rivers.

Valid 04:00 pm PST, Wed 27 Jan 2016 - 12hr Fcst
Credit: UW Atmospheric Sciences

This river will be remarkably persistent and will progress southward as the week goes on, re-energizing on Friday off the Central Californian coast. You can already see the beginning of the second river with that little ‘wave’ around 155 degrees west. In fact, there could still be some vestiges of this river on Sunday over SoCal! Even with this El Nino, they've been relatively dry, so finally getting some significant precipitation should bring a heavy sigh of relief.

Credit: National Center for Environmental Prediction (NCEP)

Here's one of my favorite model charts: the total accumulated precipitation for the 12z GFS run this morning. The picture below shows the total predicted accumulation over the next week. Tons of precipitation everywhere, and in the mountains, that precipitation will be in the form of snow.

If you think the East Coast got hit hard this past week, look at the charts below. The Sierra Nevada are a high mountain range that rises dramatically from the Central Valley and are very efficient at enhancing precipitation on their windward slopes. They often get extraordinarily heavy snowfall totals when there are moist winds perpendicular to them, and I would not be surprised if places like Mammoth Mountain and Mt. Shasta Ski Park picked up 3-4 feet of snow with this atmospheric river. If the Sierra Nevada and Washington Cascades switched places, the mountains here would get a lot more snow, Eastern Washington would be even drier, and traveling over the mountains would be a pain over the pass.

Here are the first 72 hours of snowfall. Not a blizzard, mainly because the warm atmospheric river over our area will send snow levels skyrocketing and prevent anything from accumulating here. BC gets clobbered though.

Valid 04:00 am PST, Sat 30 Jan 2016 - 72hr Fcst
Credit: UW Atmospheric Sciences

But look at the next 72 hours. A good amount of snow for the Cascades, but look at the Intermountain West. Utah gets buried. Colorado is off the chart (literally), but I'm sure they get gobs of snow too. Great news for skiers and reservoirs alike. 

Valid 04:00 am PST, Tue 02 Feb 2016 - 144hr Fcst
Credit: UW Atmospheric Sciences

We've had a somewhat atypical El Nino winter thus far, with more zonal flow into our area rather than split flow. However, long-range forecasts show the dreaded split flow returning, blocking anything from reaching the Pacific Northwest and unfortunately making it pretty difficult for that energy to spread southward to California as well. Although Northern California has gotten a lot of precipitation this year, it has been a letdown for SoCal.

Credit: National Center for Environmental Prediction

Enjoy the active weather this week!


Tuesday, January 26, 2016

A Review Of The Massive Storm Back East

Monday, January 25, 2016
1:24 pm

A car submerged in snow. Photo taken 23 January 2016.
Credit: Wikimedia User Aude

Last week in Seattle was pretty stormy, capped off by a very wet Thursday storm that set daily rainfall records throughout Western Washington and major avalanche danger on the Cascades. However, this storm was just child's play compared to the storm that impacted the eastern third of the country.

Officially known as the "January 2016 United States Blizzard" and unofficially known as "Winter Storm Jonas," "Winter Storm Anna," and even "Snowzilla," this colossal storm has caused at least 42 deaths and up to 3 billion dollars in damage. It directly impacted 85 million people with varying amounts of rain, snow, high winds, and even severe thunderstorms and tornadoes, and had international repercussions. While I've seen much stronger blizzards affect remote places like the Bering Sea, I don't recall ever seeing such an intense and extensive snowstorm affecting so many people here in the lower 48 in my lifetime.

Snow over the Eastern U.S in the aftermath of the blizzard.
Taken 1:30 pm EST on 1/24/2016
Credit: NASA MODIS, Aqua Satellite
This storm began as a shortwave trough - a small, southward undulation in the jet stream and upper-level flow - over the Pacific Northwest on January 19. The trough deepened and gradually moved to the southeast, becoming a weak area of low pressure over Texas. From there, it began to intensity rapidly as it interacted with an active southern jet stream and abundant moisture from the Gulf of Mexico.

Although that might sound pretty complex to the layperson, this was actually a pretty easy storm to forecast. Unlike small-scale local weather events like Puget Sound Convergence Zones, models generally do a pretty good job with large, powerful extratropical cyclones. Moreover, the precipitation from this storm was falling into sufficiently cold air, so there was no doubt that many areas would see historic snowfall totals. Here in the Pacific Northwest lowlands (and especially west of the Cascades), it is very hard to get both moisture and cold temperatures at the same time, and when we do, our temperatures are often just right on the fringe of freezing and our precipitation is in the form of spotty showers or the aforementioned Puget Sound Convergence Zone rather than widespread rain or snow. The result is, more often than not, a few people win the snow “lottery” and a lot of people come up empty-handed, with some (mainly small, school-going children) even throwing temper-tantrums!

Credit: National Weather Service Weather Prediction Center

The model chart above shows Friday's forecast for Saturday. The low takes a nearly perfect trajectory for a major snowstorm and blizzard, skirting just to the east of the coast. With this track, cool winds are pulled down from the north while heavy precipitation falls over the area, creating blizzard conditions.

Credit: NWS Eastern Region Twitter
Credit: NWS Boston Twitter

The National Weather Service went all-out with their snow forecasts for this storm, and for the most part, they were right. The heaviest snowfall was a little bit further northward and eastward than forecast, meaning that remote settlements like Philadelphia and New York City got higher snow totals than forecast. Central Park had 26.8 inches, a smidge below their all-time record of 26.9 inches, and Philadelphia picked up 22.4 inches. Washington D.C. was forecast to get hammered, and they did, with Dulles airport picking up 29.3 inches.

Credit: NWS Boston Twitter

There were also some pretty intense gusts from this storm. Gusts over 40 were common, with many areas having gusts over 50. These wind gusts would be impressive and even dangerous over the Puget Sound lowlands (our large trees greatly amplify the damage here), but when you combine these gusts with snowfall totals of over two feet in many places, you get blizzard conditions, and intense blizzard conditions at that. Again, Dulles Airport was hit hardest with a 52 mph gust, with Philadelphia and Central Park not far behind at 49 and 42 mph respectively. Credit to Accuweather for all of these snow and wind statistics.

Things look to calm down for the foreseeable future on the East Coast, with no major storms in sight. In our neck of the woods, our pattern will remain active. If I decide to go to graduate school down the road, I definitely want to consider researching why this El Niño has not lived up to expectations weatherwise throughout much of the country, particularly the Pacific Northwest. The Climate Prediction Center kept saying that we were going to be drier than normal, especially after the New Year. I thought so too. Instead, we are currently over 10 inches ABOVE normal rain-wise at Sea-Tac since October 1st.

If you ever decide you need to keep your ego in check, take up weather forecasting. On a good day, you are close, and on a bad day, you are completely wrong. It’s not a profession for the weak of heart!

- Charlie

Thursday, January 21, 2016

Tons Of Rain!

Thursday, January 21, 2016
5:45 p.m.

It's been pretty darn wet today. I could explain it with satellite imagery, models, maps, and all that jazz (and I will), but all you really needed to do was to go outside and look at the size of the puddles, both on the road and off it. There was an astonishing amount of puddles today.

Credit: National Weather Service

Let's take a look at some 24-hour rainfall totals around the region. At least two inches everywhere on the Coast, with especially heavy rain north of Willapa Bay and south of the mouth of the Quinalt River. As is usual, the southwestern slopes of the Olympics took home the bacon, with many spots reaching 5 inches. Even the Puget Sound region has gotten a substantial amount of rain, with areas on the northern Kitsap Peninsula getting the most, followed by the area between Seattle and Everett. The rainfall patterns here are very influenced by topography; note the dramatic rainshadow to the northeast of the Olympics, and note how much the precipitation increases as soon as air flowing off the Pacific comes aboard the Washington Coast.

Snow levels are high, and there is an avalanche warning for the Cascades. Stevens Pass was closed for some of today due to avalanche danger, and Snoqualmie was closed pretty much the entire day (and remains closed). Much of the precipitation falling in the mountains has been in the form of rain, and this greatly increases avalanche danger because it weighs down any snow "layers" that have recently accumulated and makes them much more unstable. I was caught in a minor avalanche inbounds at Alpental once on a run aptly named Adrenalin, and it was very scary. Don't go in the backcountry right now.

There is one atmospheric phenomena that routinely brings mild temperatures, high snow levels, heavy rain, and a distribution of rain heavily influenced by topography to our region. And the name of this infamous phenomena is the atmospheric river. Or, more colloquially, the Pineapple Express.

08:30 pm PST, Tue 19 Jan 2016
Credit: UW Atmospheric Sciences Water Vapor Imagery

Our current system (below) actually began life as an extremely sexy storm way out in the Pacific. It's not too often that we see storms take on such a picture-perfect appearance. You can clearly see the warm front, cold front, and occluded front, and if I could go back a little further in the satellite loop, I bet I would be able to see a pronounced dry slot near the center of circulation as well. I apologize for the tangent; I just had to show that satellite picture!

Anyway, that storm has weakened significantly over the past 48 hours but is still dumping heavy rain over our area. Do you notice how it is transporting a steady, slow-moving stream of moisture from the subtropics into our neck of the woods? That's why we call them atmospheric rivers: they don't move much side to side, preferring instead to transfer moisture and rainfall continuously into one place. 

06:00 pm PST, Thu 21 Jan 2016
Credit: UW Atmospheric Sciences Water Vapor Imagery

You can see the atmospheric river even better with this morning's model simulation!

Valid 04:00 pm PST, Thu 21 Jan 2016 - 12hr Fcst
Credit: UW Atmospheric Sciences WRF-GFS Model

This rain will continue throughout much of tonight before finally ending early tomorrow morning and transitioning to showers. The warm weather and avalanche danger will continue, but it should subside somewhat. We'll have showers over the weekend, drier weather early next week, and then the possibility of another wet and warm atmospheric river on Thursday. I'll keep you posted!


Tuesday, January 19, 2016

Is This Year's El Niño A Bust?

Tuesday, January 19, 2016
1:42 pm

Average precipitation anomalies from El Niño events. Credit: NOAA

For winter-weather lovers and skiers in the Pacific Northwest, an El Niño forecast sounds like a death sentence. Such a forecast conjures up visions of no major windstorms, hardly any lowland snow, below-average snow in the mountains, and a "death ridge" more often than not firmly situated over our area, giving us fog and poor air quality while sending powerful storms to our north and south.

This has not necessarily been the case for the SUPER strong El Niños (1982-1983 and 1997-1998), and it was not true at all for this November and especially December, where much of Oregon had its soggiest month on record and monthly snowfall records were set throughout the state. Even Washington had record snowfall in some areas, with Snoqualmie Pass picking up over 16 feet in that month. This was due to a persistent ridge in the Eastern Pacific and a trough closer to our area, directing a steady parade of cool storms from the northwest into our area. The result was heavy snowfall all the way down to 1,000 feet, and it was even possible to ski down to Mt. Si, which, despite a summit elevation of 4,167 feet, gets less snow than Snoqualmie Pass because it does not receive a strong, cool easterly wind from Eastern Washington to locally lower snow levels.

As was expected, our pattern transitioned to a more typical El Niño pattern after the New Year with high pressure over us and storms coming to our north and south, but by mid-January, we had entered a slightly wetter-than-normal pattern with weak storms coming in every day or so and putting even more snow in the Cascades. I've been up at Alpental for the past two weekends teaching ski lessons, and there is a TON of snow up there. As the below picture shows, our snowpack is still at or above normal throughout Washington, and well above normal in Oregon, Nevada, California, and southern portions of the Intermountain West and Southwest. It's common for those southern places to have above normal snowfall, but not so much for the northern places.

Credit: USDA/NRCS National Water and Climate Center

In California, many are worried whether this El Niño will give them the massive amounts of precipitation that their local weatherman promised.

Credit: Southern California Public Radio
Credit: Mercury News

Indeed, if you look at the percent of average precipitation from the beginning of the current "water year" (October 1) to present, El Niño's effects in California look rather underwhelming. Meanwhile, the Pacific Northwest has been reveling in heavy rain and mountain snowfall.

Credit: Western Regional Climate Center

This certainly doesn't look like what we'd expect for a super strong El Niño for this period. California typically gets absolutely slammed with precipitation during this time frame, with near-normal to slightly-above-normal precipitation in the Pacific Northwest.

Credit: NOAA Earth System Research Laboratory - Physical Science Division

However, Californians needn't fear. Rain is coming.

Credit: LAist
Credit: LA Times

Since the New Year, the precipitation pattern has looked much more El Niño-esque. Southern California has received near average precipitation, and the folks in Northern California have been getting soaked. We've been drier than normal here in the Pacific Northwest, but a more active pattern over our region during the next two weeks should help put us above normal by the end of the month.

Credit: Western Regional Climate Center
Credit: NOAA Earth System Research Laboratory - Physical Science Division

While California got above average rainfall during the beginning of the month due to a split flow pattern, I expect the rainfall to resume soon and be even heavier for this second time around. We are forecast to again have a split flow off the West Coast, but with a twist. This time around, the northern branch will be much, much weaker, allowing California to experience the full brunt of the storms because the storms will not be "torn apart" by the split. In fact, there may be some times when there is no split at all and a powerful jet stream is slamming directly into California. By February, I expect California to be getting absolutely walloped by storms. That is what happened in 1983 and 1998, and signs are there that it will happen again.

Credit: NCEP

But don't just take my word for it. The Climate Prediction Center is also going with above-average precipitation in California. As a side note, they have consistently underestimated the precipitation in the Northwest, and I would not be surprised if the Pacific Northwest picks up above-average precipitation in this pattern as well. Of course, they are paid professionals and I am just another internet blogger.

Credit: Climate Prediction Center

So no, this year's El Niño is not a bust. It's just a little late to the party.


Friday, January 8, 2016

An Extremely Cold Playoff Game On Tap

Wednesday, January 6, 2016
11:20 pm

Richard Sherman looking ferocious during week 13 vs the Vikings

I've been following several things lately: the return of rain to California, the thousands of earthquakes on the Olympic Peninsula and Vancouver Island, and even the slight, slight weakening of the El Niño in the tropical Pacific. It looks as though the ocean temperatures reached their peak a few weeks back and have began to decrease. However, we are just starting to feel the influence of it here on the West Coast. 

But with the Seahawks coming off a massive road win in Arizona and Beast Mode finally back in the huddle (edit 8:52 pm 1/8: I just found out he's out unfortunately, we'll see how Michael can do) I've been following the Hawks - and their Sunday playoff game, extensively. Tragically, I won't be able to watch it; I'll be receiving training and orientation for teaching ski lessons up at Alpental, but I'll see if I can find a way to intermittently tune into Steve Raible's play-by-play and Warren Moon's color commentary nonetheless. 

Minnesota used to play in usually plays in the "Metrodome," an indoor stadium, but right now, a new indoor stadium for them is being built and they are playing outside at TCF Bank Stadium on the University of Minnesota campus in Minneapolis. Come Sunday, I'm sure that most players (and all the fans) wished they were still playing inside. In case you haven't heard it by now, temperatures are forecast to be near 0 for the game, with windchills near 20 below. 

Credit: Ian Leonard, FOX 9 Minneapolis Chief Meteorologist

As the above picture shows, only six NFL games have ever made it below 0, and the last time such conditions occurred for the Vikings on their home turf was 43 years ago, when the Vikings still played outside in Metropolitan Stadium. By Sunday evening, that six could become a seven. We'll have to see just how cold we get.

ECMWF 500mb heights and sea-level pressure on 6 pm CST Sunday
Credit: Unisys Weather

The models are consistently showing a large mass of cold air moving down from the arctic into the Midwest. This is the famed "polar vortex." El Niños tend to keep any frigid air bottled up far north and often bring record warmth to the northern tier of the country, and that is what has happened this year, particularly east of the Rockies. This cold blast looks to be relatively short-lived, with temperatures rebounding to near-normal by the middle of next week.

I was reading the Seattle Times this morning, and I found a neato article by Matt Calkins where he talks about the effects of cold temperatures on the body and on the game of football. I suggest reading the whole article, but just to summarize, it doesn't sound like cold temperatures affect teams that much. During games with temperatures under 10 degrees, a quarterbacks completion percentage falls by roughly 2%, field goal accuracy drops by 1.7%, and punts are, on average, 3 yards shorter, as colder, drier air is denser and increases resistance on the football. The coldest game in NFL history, the "Ice Bowl," of 1967, featured temperatures of -13 degrees with a -48 degree windchill, yet Bart Starr, the hall-of-fame quarterback for the victorious Packers, went 14/24 for 191 yards, 2 touchdowns, and 0 interceptions for a 111.6 passer rating. These are very impressive numbers, particularly when you consider that the NFL, and particularly the Lombardi Packers, were a power running team and NOT a pass happy team like so many teams in the NFL today.

It would seem like this cold weather would put the Seahawks at a disadvantage. Even though we claim to be a running team, we haven't seemed like it this year, as we have the most prolific passing attack in franchise history. It would seem to me that passing would be more affected by cold weather than running. Moreover, Minnesota has more experience playing in these super cold games. Also, their sideline will be in the sun, while the Seahawks will have to endure being in the shade for the entire game, and that will make a difference. For what it's worth, the Seahawks have historically done pretty poorly in cold-weather games, and the Carroll-era Hawks are 0-2 when game temperatures are 20 degrees or lower.

Still, these guys are working so hard that it's hard to believe they will get too cold. Take a look at New Orleans Saints nose tackle Hollis Thomas during the 2007 NFC Championship game in Chicago. He doesn't look very cold.


Neither does Brandon Jacobs during the -4 degree NFC championship game a year later at Lambeau Field (with a windchill of -24 degrees, I might add).

Credit: NFL/David Stluka

The main thing I worry about is their extremities; will there be more dropped balls because the receiver's hands are colder and less responsive? Will the quarterbacks not be as precise with their passes? Possibly. Still, I have a hard time imagining anybody playing poorly because they find themselves shivering. Additionally, Minnesota-based WSI sports will be supplying the players with high-tech cold weather gear.

As for the fans? I wouldn't be surprised if the Minnesota hospitals are treating a few cases of mild frostbite on Monday.

Credit: National Viking Association

Go Hawks!