Cascadia Subduction Zone

Monday, April 30, 2012
10:49 A.M.

I know it's been a while since I've posted. Sorry.

I actually haven't been doing a whole lot of weather related things lately. The weather has been pretty boring around here (and it probably will be until October), so I've been focusing on other earth sciences that interest me.

In particular, I've been reading a lot about the Cascadia Subduction Zone. Remember that huge earthquake that occurred last year in Japan? We've got a fault off our coast that bears a lot of similarity to the fault that caused that earthquake and tsunami in Japan last year. I'm sure many of you knew that we live in an earthquake-prone region, especially if you lived through the 2001 Nisqually Earthquake, but I don't know how many of you have really thought about what would happen if we saw an earthquake like the one Japan saw last year.

Huge subduction zone earthquakes like the one in Japan last year and the one in the Indian Ocean in 2004 are called "megathrust earthquakes." Megathrust earthquakes are the most powerful type of earthquakes and completely overshadow all other earthquakes in the amount of energy released. To get an idea of the amount of energy these earthquakes release, take a look at the pie chart below. The three largest earthquakes ever recorded (Sumatra, Alaska, and Chile) make up about half of all the seismic energy released in the past 100 years. The 7.9 earthquake that devastated San Francisco in 1906 is practically invisible on this pie chart.

If a megathrust earthquake were to occur off our coast, many coastal communities would be wiped out from the tsunami and major cities like Seattle and Portland would suffer heavy damage from the earthquake itself. We are not prepared for such a disaster.

I've got to go to class now... I know this isn't the most elegantly written post I've ever created. But it is food for thought.

Charlie

It's Thursday, Thursday.

Thursday, April 5, 2012

9:43 A.M.

Yes, it may not be Friday, and the weekend may actually be two days away, but I'm still pretty darn excited. Besides it being Easter Sunday, which is always in style, the weather is expected to be nicer than it has been in a while. It certainly won't be hot and sunny, but it will be warmer than we've seen in a while. It will definitely be good picnic weather and a great day to go relax in the UW quad. I just can't get enough of how beautiful the cherry blossoms are right now. Of course, I wish there were actual cherries involved, but I'll take cherry blossoms any day.

Before then, we've got some weather to go through. Today could be an interesting day for weather for certain places, because we've got cold air overhead and strong solar insolation. When the sun heats the lower atmosphere, air expands and decreases in density, and these air parcels continue to rise through more dense and colder air in the mid-upper trophosphere. This phenomenon creates towering cumulus clouds, and, if the conditions are right, thunderstorms. The air mass isn't too unstable today, so if there are any thunderstorms, they will be isolated. We could see some beautiful cumulus clouds though.

Cumulus congestus clouds

 Weak cumulonimbus over Seattle

And here's a picture of a supercell thunderstorm. We will not be seeing these today.

Of course, our thunderstorms are a far cry from the thunderstorms seen east of the Rockies at this time of year, but they are interesting nonetheless. There actually was one time where we got some very well developed thunderstorms on the Cascade foothills, but they were still much weaker than storms like the one pictured above. The UW atmospheric sciences department loves this picture.

Ok, now let's get onto our forecast. Chilly with a slight chance of thunderstorms today, especially along the coast. We could see a few showers tomorrow as well, but they will be more isolated and weaker than today.

Then comes the weekend. 

Right now we've got a pretty big trough off our coast, which is directing cool air into our region. 

Valid 05:00 am PDT Thu, 05 Apr 2012 - UW 36km WRF-GFS 1000-500mb thickness, SLP

But look what happens on Saturday. We get a little ridge over our area, which will direct warmer air into our region.

Valid 05:00 pm PDT Sat, 07 Apr 2012 - 60hr Fcst -  - UW 36km WRF-GFS 1000-500mb thickness, SLP

The ridge will strengthen on Sunday before a weak trough moves in on Monday, giving us a chance of showers and thunderstorms.

Enjoy your Thursday!

Charlie

Accuweather's 25 Day Forecast

Wednesday, April 4, 2012
11:00 A.M.

I have a love-hate relationship with Accuweather. On one hand, I love some of the blogs and posts up there, and they are fun to look at. On the other hand, their forecasts are generally pretty inaccurate and they tend not to focus on the West Coast. Today, Accuweather unveiled their new "25 Day Forecast." How much stock can we put in these forecasts when forecasts for each day around here are basically useless after a week and it is hard to gather trends past 10 days?

The answer? Absolutely none.

It's completely ridiculous. It is NOT POSSIBLE to accurately predict the daily high, low, and amount of precipitation 25 days from now, and as I learned in my atmospheric science class with Cliff Mass fall quarter, it will likely never be possible to have reliable daily forecasts past two weeks out. Right now, forecast accuracy dramatically increases inside 120 hours and tends to just get better from there, but I find it highly unlikely that we will ever be able to extend this level of accuracy five-fold, to 25 days. Definitely not in my lifetime.

On April 28, Accuweather is predicting a high of 54 and a low of 39. There will be a 53% chance of a thunderstorm in the afternoon, one hour of precipitation, and a total precipitation of .19 inches. The winds will be out of the south at 5 mph and gust to 14 mph during the day, and they will be from the NNE at 5 mph with gusts to 10 mph at night.

Still, it will be fun to look at this extended forecast, especially if it is forecasting arctic outbreaks in the winter. So while I hate how Accuweather is giving the public a false representation of the science of synoptic-scale modeling, the 25 day forecast will definitely give me some excitement when the weather is boring around here.

And for that, I thank them.
Charlie

El Nino/La Nina Update

Tuesday, April 3, 2012
1:06 P.M.

This has to be a super speedy post, cause I have a chem lab orientation I have to be at by 1:30 and it takes around 10 minutes to walk over there. But hopefully I can get some stuff down before then.

I might as well give you guys a brief overview of how our La Nina is doing. It's pretty much dead. Let's take a look at some of the SST anomalies for the different regions. As I have said many times before in this blog, Nino 3.4 is the region that is generally the most telling of the general state of the tropical Pacific as it relates to El Nino or La Nina.

Retrieved from Columbia University's International Research Institute for Climate and Society

Nino 3.4 is just about neutral, and it is forecast to warm up even further over the next couple months. Still, it is not expected to transition to an El Nino phase (thank goodness, I hate those things) but it will likely be a tad warmer than average. We are definitely not in a La Nina anymore. Here's a picture of the SST temperatures and anomalies over the Tropical Pacific for the past week.

And finally, here's a picture of some model forecasts the Nino 3.4 region SST anomalies over the next year or so. The forecast is a little old, but you can clearly see a transition to a neutral phase, with temperatures ever so slightly above average.

I'm a fast typer.
Charlie

Light at the End of the Tunnel!

Monday, April 2, 2012
10:46 A.M.

So, my post yesterday was an April Fool's prank. You gotta admit though, it was pretty good.

Anyway, looking over the models this morning, it appears as though some warmer weather will soon be affecting us in the Pacific Northwest. Take a look at the latest model extraction from the 12z GFS for Seattle! This is a program from Brian Schmit, so I gotta give him credit.

Look at those high temps! Starting Sunday, we could get pretty toasty around here. I, for one, am actually a little depressed about this... I love my cold, springtime showers and sunbreaks weather, but I'm sure many of you will be happy for a change. I DO plan to have some picnics in the UW quad, which should be super fun. I've already got one scheduled with some girls on a different floor in the dorm. We plan to eat tons of ice cream. Before then, we've got some weather to go through.

03:00 am PDT Mon 02 Apr 2012 - West Coast NWS water vapor satellite

Take a look at this BEAUTIFUL storm above. Not every Pacific Northwest storm takes on such a picture-perfect appearance. Take a look at that spiral! Simply incredible. That's a powerful storm, no foolin' here. This satellite image was taken at 3 A.M., and the storm has degraded since then, but it is still very pretty.

10:30 am PDT Mon 02 Apr 2012 - West Coast NWS water vapor satellite

The long fetch of tropical moisture is expected to slowly make its way inland today into tonight. Although it isn't looking as wet and strong as originally feared, it will bring us around a quarter inch of rain, and there are wind advisories for the Northwest Interior and the Coast.

Take a gander at the 500mb chart 180 hours from now though. See that huge ridge of high pressure over us? That's what is expected to bring us picnic weather. 

Valid 05:00 pm PDT Mon, 09 Apr 2012 - 180hr Fcst - UW 36km 12z WRF-GFS 500mb vorticity, heights

One more week, and then we'll get into some wonderful (albeit boring) weather. Get the frisbees out!

Have a good one,

Charlie

Puget Sound Waterspouts

Sunday April 1, 2012
6:24 P.M.

Waterspout over the Florida Keys. Retrieved from NOAA.

When I was looking at the radar today, I definitely noticed some rather heavy rain showers. I have a house in Cultus Bay on South Whidbey Island, so I wasn't too surprised when my neighbor called me to tell me the skies were looking pretty stormy. But then he told me something else, and my jaw practically dropped to the floor. He said that two HUGE waterspouts had entered formed right off Possession Point, which is more in Puget Sound, and then gone into Cultus Bay before getting out of the bay and passing within 100 yards of his house before dissipating. Waterspouts are pretty rare around here, but they are definitely not unheard of, especially in the spring.

Take a look at the radar below. To prove to you that this is not an April Fool's joke, focus your attention on the precipitation over South Whidbey Island. You can see a pretty well-defined convergence zone over there, and that is probably what caused the waterspouts. My neighbor called me at 6:32 PM, so these waterspouts were definitely associated with this convergence zone.

Convergence zones are often associated with funnel clouds, tornadoes, and waterspouts. Cliff Mass has a great book about weather in the Pacific Northwest that explains why, but I haven't been able to find the diagrams he uses in the book on the web (believe me, I've tried). Anyway, convergence zones form at the boundary between northerly winds and southerly winds, and when these two winds collide, they often produce localized areas of rotation that produce weak tornadoes and waterspouts.

The best metaphor for showing how convergence zones can spin up tornadoes is a pinwheel. Since a convergence zone has air coming in from the north and the south, it spins columns of air like pinwheels, and this rotation leads to waterspouts like the ones my neighbor witnessed on Whidbey Island.

Waterspouts pick up lots of stuff from the water, and my neighbor found clams, sand, some seaweed, and even some baitfish scattered around the neighborhood. Rumor has it a salmon fell at another house in Cultus Bay, but my neighbor wasn't quite sure on this one.

Thanks for reading, and don't be surprised if a herring comes your way in the next hour or two. :)

Charlie