Windstorm Update #2

Sunday, September 29, 2013
11:27 p.m.

Hey everybody, this is just going to be a quick post because I gots to go to bed soon. Anyway, the GFS was correct and the NAM was not. The NAM is often called the "Never Accurate Model" for that very reason. We still have high wind warnings up, but I am doubtful that many places will see gusts above 60, and the NWS is too.

Here are some more shots from that same satellite. They were taken at 7:30 and 11 p.m. respectively.

In the second image, you can see that the dry slot is starting to fill up. This is a sign that the storm is weakening.

However, we will still see some pretty hefty winds tonight. Some exposed headlands, like Alki or West Point, could see gusts to 50 miles per hour. Most of the region will likely be in the 35-45 mph range.

We will definitely still have heavy showers throughout the night, but the steady stuff is over. Although it will be paltry compared to this weekend, the Monday-Wednesday time frame of next week looks soggy as well. After that, we finally see that thing we call sunshine and highs rebound into the 60s.

Have a nice night!!!

Charles

Windstorm Update

Sunday, September 29, 2013
10:36 a.m.

What are more delicious? Apples or mangoes?

Mangoes, of course! They are juicier, sweeter, and slipperier than our state fruit. Also, they are imported, and just the thought of eating something that came from Thailand automatically makes it more delicious.

Apples aren't too bad though. They have anti-doctor properties and permeate the Pacific Northwest. They are cheap and local, and they are therefore under-appreciated. Once you get over the sobering fact that the most awesome fruit grows somewhere between the tropics of Cancer and Capricorn, apples don't seem too bad.

This is the analogy I came up with for today's UW model runs. Apples are to mangoes as the WRF-GFS is to the MM5-NAM. Let me show you what I mean.

The 12z WRF-GFS is about on par with what we saw last night... maybe a wee bit weaker. This sort of track would give storm force winds to the coast with lesser gales inland. Of course, gales are nothing to snicker at, but we aren't talking any record winds here. The gradients are not nearly tight enough over our area. The place that has the best shot of receiving some damaging winds would be Clayoquot Sound and Tofino.

Valid 08:00 pm PDT, Sun 29 Sep 2013 - 15hr Fcst: 1000-500mb thickness, SLP (hPa). UW WRF-GFS 12km Resolution: Initialized 12z Sun 29 Sep 2013. Retrieved from the (University of Washington) Pacific Northwest Environmental Forecasts and Observations website. Chart URL: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d2_slp+2013092900//84/3

This is our "apple." It's a fairly common type of storm and is probably the more likely of the two scenarios, although my opinion is starting to shift as I'm taking a look at the current water vapor imagery. Still, the GFS has been more consistent and is more in line with the Canadian model this morning.

Now, let's take a look at the mango.

Valid 08:00 pm PDT, Sun 29 Sep 2013 - 15hr Fcst: 1000-500mb thickness, SLP (hPa). UW MM5-NAM 12km Resolution: Initialized 12z Sun 29 Sep 2013. Retrieved from the (University of Washington) Pacific Northwest Environmental Forecasts and Observations website. Chart URL: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d2_e_thick+//72/3.

The NAM paints a much more dire scenario for Western Washington, particularly Puget Sound. An intense low moves to Cape Flattery and deepens to an astounding 966 millibars before steamrolling through southern BC. This would give damaging winds to all of Western Washington. 

But at this point, these models don't much matter. Our best sources of information are the satellite images offshore, especially the water vapor models. When a low pressure system is undergoing explosive development as this one is right now, a "dry slot" - an area of relatively dry air at the center of the low - begins to become larger. This often does not show up on the visible or infrared satellite imagery. Take a look at the water vapor image below and you'll see what I mean.

http://sat.wrh.noaa.gov/satellite/alternative.php?wfo=pqr&area=nw&type=wv&size=4

See how is that little slot of black and red? That marks the center of the low. The region of moisture north of this slot is what is called the "bent-back occlusion" and is indicative of a meteorological "bomb" - an explosively developing and deepening mid-latitude cyclone. Check out this link to watch this animation. You can bet that I'll be watching this loop all day.

The National Weather Service, which was hesitant to give King County a High Wind Warning, has now given one to them and has upgraded the Wind Advisory in Pierce Country to a High Wind Warning as well.

God... this is next to impossible to write when listening to Steve Raible call the Seahawks game. That's why it's two hours later and I've only gotten this far.

But this is enough for now. The bottom line is that we will have to watch the satellite. Also, now that we have the coastal radar at Langley Hill, we will be able to get a better idea of the location of the low. If the NAM is correct, Western Washington will see the most damaging wind event in several years... perhaps the strongest since the Hanukkah Eve Storm of 2006. It's a very exciting time for meteorological maniacs like me.

Enjoy your Sunday! Stay posted... I'll post updates as new details come along.

Chaz

What Does the Model Say?

Saturday, September 28, 2013
10:49 p.m.

I'm sure many of you are familiar with Ylvis' international hit: "What Does the Fox Say?". I've heard the song once or twice, and that's one or two many times too many. The fox does not say "gering-ding-ding-ding-dingeringeding" or "Wa-pa-pa-pa-pa-pa-pow."

The fox goes "WAArra!!!" Everybody knows that. So what's with the annoying song?

A far better question is "what does the model say?" Here, we can look at the various models and interpret what they are saying. No need for any of that ring-a-ding-ding nonsense. However, because models make no sound, if one wanted to write a song about the varying statistical output of models, it would have to be called "What Does the Model-Watcher Say?". "I LIKE THE 500mb PATTERN" or "NEED MORE CAPE" (convective available potential energy) or "WHERE'S THE RAIN SHADOW" could be lyrics, and they'd make more sense than "What does the fox say (bass drop, cue jibberish)."

But this blog is in written form, not audio form, so we don't need to worry about any of those logistics. Let's take a look at what some of the models are saying.

First, let's look at some important differences in this evening's (00z) runs from those this morning (12z). The 'z' is just a synonym for UTC or GMT (Coordinated Universal Time or Greenwich Mean Time). The 12z MM5-NAM had a deeper low than the 00z, but the 00z WRF-GFS was stronger.

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Sorry for this brief change of subject, but the fraternity next door (Phi Kappa Sigma/Phi Pools/Pi Fools) just started playing that fox song. Let me get my earplugs real quick...

Alright... ear plugs are in. Back to weather stuff.

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The bigger differences were in the WRF-GFS, so let's compare those two real quick.

Valid 05:00 pm PDT, Sun 29 Sep 2013 - 36hr Fcst: temperature at 925 mb (C), SLP (hPa), 10-meter wind speed (knots).  UW WRF-GFS 12km Resolution: Initialized 12z Sat 28 Sep 2013. Retrieved from the (University of Washington) Pacific Northwest Environmental Forecasts and Observations website. Chart URL: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d2_slp+2013092900//84/3

Valid 05:00 pm PDT, Sun 29 Sep 2013 - 24hr Fcst: temperature at 925 mb (C), SLP (hPa), 10-meter wind speed (knots).  UW WRF-GFS 12km Resolution: Initialized 00z Sun 29 Sep 2013. Retrieved from the (University of Washington) Pacific Northwest Environmental Forecasts and Observations website. http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d2_slp+2013092900//84/3

As you can see, the most recent run is much deeper and a tad further north. It gives high winds (gusts over 58 miles per hour) to the coast, northern interior, and Puget Sound from Seattle northward. This is an encouraging sign for high-wind lovers.

Unfortunately, I don't have access to the European model, but I do have access to the Canadian one. It is... to say the least.. smile-inducing.

The Canadian model brings a ~960 millibar low to southern Vancouver Island. This scenario would bring the highest winds in recent memory throughout Western Washington. It's an outlier at this point, but it's fun to look at.

What does this model-watcher say? BRING IT ON! Either way, us meteorological enthusiasts are gonna have a good time. Stay safe!!!

Chuckles

An Unusual September Rain Event

Saturday, September 28, 2013
5:50 a.m.

There's no sound quite like moderate rain.

Light rain doesn't make much of a sound at all, and heavy rain can be overpowering at times, especially if it is related with a thunderstorm. But moderate rain... that hits the spot. Moderate, consistent, soaking rain is great for just sitting by a fire with a warm bowl of Top Ramen. Hot chocolate is so early 90s.

Let's take a look at our current situation. It's been a while since we've seen such a colorful map. We've got flood watches, flood warnings, wind advisories, high wind warnings, gales, and even storm warnings well off the coast and from Willapa Bay down south to Cape Blanco, Oregon.

Watches, Advisories, and Warnings over Western Washington. Retrieved from Seattle NWS. Site URL: http://www.wrh.noaa.gov/sew/

So far, the Cascades in Southern Washington and Northern Oregon have seen the heaviest rain. Timberline Ski area has seen 5.17 inches of rain in the last 24 hours. Much of the mountains northward have not seen quite as much rain, but amounts have still been quite significant. As of 3:50 p.m., Sea-Tac has accumulated 1.15 inches of rain in the gauge since midnight. I cross-checked this statistic with some on-site observations while my mom was driving me down Alder to our house, and the 1.15 inches seems to be correct... perhaps even a bit low. Take a look at the UW WRF-GFS below. It shows over 10 inches of precipitation in many locations over a 72 hour period. That's pretty incredible. Thankfully, while some rivers will flood, the rivers started out pretty low, so any flooding will be minor.

Valid 05:00 am PDT, Tue 01 Oct 2013 - 72hr Fcst: 72-hour precipitation (inches), 10-meter wind (knots). UW WRF-GFS 4km Resolution: Initialized 12z Sat 28 Sep 2013. Retrieved from the (University of Washington) Pacific Northwest Environmental Forecasts and Observations website. Chart URL: http://www.atmos.washington.edu/~ovens/wxloop.cgi?mm5d3_wa_pcp72+///3

One of my favorite aspects of the UW atmospheric sciences website is their "Northwest Radar Loop," which is a composite loop of images from a variety of standard NWS WSR-88D radars around the region. I wish they kept a continuous record (or at least a longer one) of past radar images, but the loop extends back eight hours, and that's not too shabby at all. The image below shows that most of the recent rain has been over Washington, and it will continue well into the evening hours over Seattle before coming to halt.

Andddd... the power just went out. 4:38 p.m. But that's ok.

I was reading some Seattle NWS discussions and looking at some satellite imagery over the past couple days, and it became clear that there was some tropical moisture entrained within this storm. While it is uncommon for strong storms to roar ashore this early in autumn, they are definitely not unheard of. I remember a strong, compact, poorly forecast storm that came through on October 18, 2007, and I remember a much stronger storm that curled off our coast on the 5th of that year. And of course, the earliest windstorm in the Pacific Northwest - the Columbus Day Storm - was easily the strongest. Downtown Portland had a gust to 116 mph. 'Nuff said.

We've got an even stronger storm on tap for Sunday, and although this one will be quite the soaker as well, the main threat will be the wind. A HIGH WIND WATCH is now in effect from from Sunday afternoon to Sunday night over much of Western Washington, including areas from Seattle northward in the Puget Sound region. As is tradition, the coast and north interior will see the highest winds, but even the Seattle area could see a few gusts to freeway speeds. This will no Columbus Day storm... but it's forecast to be stronger than anything I've ever seen in September.

Last year's storm season was apocalyptically boring. Will this year help to nudge the short-term average back to the long-term average? It's too early to know. But from all the thunderstorms earlier this summer to a possibly record-setting soaking of a September, I can rest easy, knowing that I've already been blessed to see some unusually interesting weather in our region. :)

And at 5:48 p.m., the power is back on. :)

I will post an update tonight with the latest forecast for the Sunday storm. If you take a model average, we'll probably see a 970-980 mb low coming in somewhere between Forks and Winter Harbour, BC. This is quite a spread for an event expected to occur in less than 24 hours.

Windstorm-ily yours,
Chuck

Biblical Rainfall Amounts in Colorado

Wednesday, September 18, 2013
4:13 a.m. (one of those nights...)

Hey everybody! It's super early Wednesday morning and I woke up and am having trouble falling back asleep. There are two things that make me fall asleep... writing weather blogs and reading the Bible. I'm not religious, I just want to read it because I'm curious about what it has to say and how this has been interpreted by people around the world, especially those in politics. I don't mean to offend anybody, but it's really boring... I haven't gotten out of Genesis yet. Moses was no Shakespeare. That doesn't make the Bible any less fascinating... it just means that it's not exactly the most riveting text in the world.

I heard about the Colorado floods when I was moving into my new house. I didn't have much time to write about them or even study them in detail, but in this post, I'll give an overview of what happened and why it happened. So without further ado, let's get to it!

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I still remember Seattle's rainiest day ever recorded. It was October 20, 2003, and I was a fifth-grader at McGilvra Elementary in Madison Park. We had a "rainy-day recess," and all of our activities were to take place either inside the school gymnasium or under a covered area with basketball hoops and such right outside of it. There were two "portables"  (classrooms outside the main school that were built so the school could accommodate more students) that had recently been built outside the school by the gym, and these were on the cusp of being flooded due to a storm drain that had stopped functioning near them. The day afterwards, my mom, my brother and I went on an expedition to find some remaining puddles and came across a small lake in an area near the arboretum that had poor drainage. A couple days later, I went fishing with my dad in Puget Sound and saw logs deposited by the outflow of the region's rivers scattered outside the Edmonds marina.

I also remember one of the heaviest downbursts of rain ever recorded in Seattle. It was around 4:40 p.m. on Thursday, December 14, 2006 when I began to hear a long, consistent roar outside. I went out to check and witnessed the heaviest rainfall rates I had ever seen in my life. The ground was saturated from the previous November, which was the wettest month on record for many places (including Seattle), and several inches that had fallen since Monday. The ground could not absorb any more water, so the rain from this brief squall turned roads into rivers and even tragically drowned a woman living in Madison Valley, a bowl-shaped region that was among the hardest hit by the storm. My very primitive Lacrosse rain gauge measured rainfall rates of 1.88 inches per hour, and they likely reached over 2 inches per hour for brief periods of time. Those two events stick out very clearly in my mind, and by combining the massive amount of rainfall on the 20th with the massive rates on the 14th, I am able to gain an inkling of perspective on the biblical amounts of rain received in Boulder on the 20th.

Between the afternoon of Monday, September 9 and Friday, September 13, much of the Front Range of Colorado saw unprecedented amounts of rain and associated flash flooding. Boulder was one of the areas hardest hit, receiving 14.62 inches during this time period with 9.08 inches on Thursday, September 12 alone. To make matters even flash-floodier, most of this rain occurred in a couple hours. The previous record for total daily rainfall in Boulder, an impressive 4.80 inches on July 31, 2013, was nearly doubled.

And on that note, I'm hitting the hay. It is 5:59 a.m., and I've done a little storytelling and a lot of research that will hopefully make the rest of this post go a little quicker. I'm not Bible-sleepy, but I'm a fair bit more relaxed. ;)

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Alright. It is 10 hours and 22 minutes later, and I'm ready to write again. I just got back from a strenuous workout, but I'm not quite tired enough to begin my ritualistic afternoon nap. Thankfully, I got the two B's... Blogger and Bible, and I'll choose the former.

One note on the pictures below... most of this content was taken from other people's blogs on the Colorado floods. The pictures below are in the public domain, but I still give credit to the people from which I got the pictures from. I'm adept at obtaining pictures of any sort to describe Pacific Northwest weather because I do it all the time, but I'm simply not familiar with places to get the types of charts and imagery that are shown below.

Now that that's out of the way, let's take a look at how it all started.

We had a setup here that was actually pretty darn similar to a setup that brought intense rains to Alberta earlier this summer. The 500 millibar height chart below shows the configuration of the atmosphere on June 20, 2013 at the height of the event. High pressure in northern Alberta prevented a low-pressure system from passing eastward across the country, and since air flows into areas of low pressure, warm, humid air with origins east of the Rockies flowed westward and produced incredible amounts of orographic precipitation as it encountered the topography of the Rockies.

NWS Upper level analysis of the weather pattern leading to Alberta flooding as of 5 a.m. PDT, Thu 20 Jun 2013. Retrieved from TheWeatherNetwork.com. Chart URL: http://www.theweathernetwork.com/news/articles/colorado-flooding-echoes-of-alberta-/12914/

Now, fast-forward three months and you have a very similar scenario setting up further south along the eastern edge of the Rockies.

NWS Upper level analysis of the weather pattern leading to Colorado flooding as of 5 a.m. PDT, Thu 12 Sep 2013. Retrieved from TheWeatherNetwork.com. Chart URL: http://www.theweathernetwork.com/news/articles/colorado-flooding-echoes-of-alberta-/12914/

Again, you've got a moist, slow-moving low pressure system to the west that has its eastward progress slowed by a large area of high pressure over Canada. It's essentially the same pattern shifted to the south. Again, this low was responsible for steering air east of the Rockies, in this case directly from the Gulf of Mexico, northwestward into Colorado. This event occurred around the annual peak of sea-surface-temperatures in the Gulf of Mexico, and the air directed into the area had incredible amounts of moisture and heat energy within it. When that air collided into the Front Range, well, you know the rest.

The chart below shows balloon soundings from the Denver area around the time of the big floods. It shows a lot of things, and all are very useful in their own special ways. I want to you take a particularly close look at two things, though. The first is the total Precipitable Water (PW) value, which is located on the bottom left of the chart under "Parcel." These values are a measure of how much moisture in the atmosphere. More specifically, they measure how much water would precipitate (fall towards the ground) if all the water vapor in a column of the atmosphere was condensed. Since this value is 1.15 inches, the water vapor alone within the column of air sampled by the balloon would amount to 1.15 inches of rain. That's a LOT of moisture. Additionally, the level of moisture was extremely deep. The red and green lines represent the temperature and dew point, respectively, throughout the atmosphere. They are essentially the same all the way up to the 500mb level, which is approximately 18,000 feet in the atmosphere. That's INSANE. 

The top three highest PW values ever recorded in September at Denver since records began in 1948 occurred over the 12-13th, and they completely overshadowed anything that had ever been seen before.

1.33" 12Z September 12, 2013
1.31" 00Z September 12, 2013
1.24" 12Z September 13, 2013
1.23" 12Z September 10, 1980
1.22" 00Z September 2, 1997
1.21" 00Z September 7, 2002
1.20" 00Z September 13, 2013

But how can we have PW values of "only" 1.3 inches but still end up with 10 inches of rain in spots? Remember, this moist air was constantly pouring into the area, so as water vapor condensed out of the atmosphere and the atmosphere held less, this relatively drier air was continuously replaced by moister air originating from the Gulf.

The second one is the environmental lapse rates. These are located below the PW value, and represent the rate at which the air temperature changes with height (positive values correspond to decreasing temperature with increasing elevation). Environmental lapse rates change, but there are two lapse rates commonly used in meteorology that are always the same. These are the unsaturated and saturated adiabatic lapse rates and represent the laboratory-tested values of the rate of change of air temperature a parcel experiences as it rises (or decreases) in elevation.

The unsaturated adiabatic lapse rate in our atmosphere has been found to be a cooling of 9.8 degrees C per km gained in the atmosphere. The saturated one varies strongly with temperature, but it is usually around 5.5 degrees C per km. If you want to calculate it more specifically, follow the equation below...



... where

	= Wet adiabatic lapse rate, K/m
	= Earth's gravitational acceleration = 9.8076 m/s2
	= Heat of vaporization of water, = 2260000 J/kg
	= The ratio of the mass of water vapor to the mass of dry air, =.6219897 kg/kg
	= The universal gas constant = 8,314 J mol−1 K−1
	= The molecular weight of any specific gas, kg/kmol = 28.9635 for dry air and 18.015 for water vapor
	= The specific gas constant of a gas, denoted as
	= Specific gas constant of dry air = 287 J kg−1 K−1
	= Specific gas constant of water vapor = 462 J kg−1 K−1
	=The dimensionless ratio of the specific gas constant of dry air to the specific gas constant for water vapor = 0.6220
	= Temperature of the saturated air, K
	= The specific heat of dry air at constant pressure, = 1003.5 J kg−1 K−1

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Sorry, just needed to put that in there. It's actually pretty easy to calculate... the only variable is the temperature of the saturated air. The rest of the letters represent constants. That said, it doesn't look fun. I got it from Wikipedia, which means it's 100% right.

Anyway, the unsaturated adiabatic lapse rate is always less than the unsaturated lapse rate because the condensation of water droplets from water vapor is an exothermic process - that is, it releases heat. Since there was SOOO much moisture in the atmosphere and moist lapse rate was lower than the environmental lapse rate, the air that rose cooled at a slower rate than the air around it, causing it to rise even further because it was less dense. The combination of a large change in temperature with height and copious amounts of moisture can be a recipe for disaster, and when you factor in the orographic effects of the mountains providing additional lift, you have a recipe for an apocalypse.

Below are two pictures that I thought were particularly apocalyptic. I got them both from Jeff Masters' Wunderblog from Weather Underground.

Flooding in Boulder, Colorado on Wednesday evening, September 11, 2013. Photo posted by brandish on Instagram @photogjake.

Damage to Highway 34 along the Big Thompson River, on the road to Estes Park, Colorado. Image credit: Colorado National Guard.

Here's a doppler radar estimate of the totals from just the 12th that I retrieved from Jeff Masters' Wunderblog. There's a small location of over 12 inches to the south of Boulder. Some places received over 20 inches from the entire event.

And here is a "recurrence interval." Have you ever heard the term "100-year-flood"? Well, it looks like this event was closer to the 1-in-1,000 year category in some places, meaning it has a 0.1 % chance of occurring any specific year.

I used Luke Madaus' Looking Aloft blog, an article written by The Weather Network, and, as mentioned before, Jeff Masters' Wunderblog as my primary sources of information to write this blog. You should definitely follow Luke's blog... he's a UW atmospheric sciences graduate student who was a TA in the 101 class I took with Cliff Mass fall quarter freshman year. He knows his stuff AND is a really good writer. He, along with Scott Sistek and Cliff Mass, are "there" as far as blogging goes. I'm currently "here," but I'm working on getting over "there."
We have a wet weekend ahead of us, but I doubt we'll be seeing any Bible references in NWS forecast discussions. :)

Charlie