A Record Low for Arctic Sea Ice

Monday, September 24, 2012
10:43 A.M.

Retrieved from National Snow and Ice Data Center (NSIDC)

On September 16, 2012, the arctic reached a record low for sea ice cover. Now, it is finally expanding as autumn arrives, but it is still well below average.

The sea ice cover this year fell to 3.41 million kilometers, which is 18% less than the previous record for lowest ice extent, which was set in 2007. It is also 49% less than the median for 1979-2000, which is outlined in the orange. This is the fifth consecutive year, and the fifth time in recorded history, that ice-free navigation was possible from the north coast of Canada to the north coast of Siberia, and, as you can see, this navigation window was massive. 

Retrieved from Chapman & Walsh (2001), and updated by the University of Illinois Cryosphere Today. In addition, Wunderblog blogger Jeff Masters updated the graph to include 2011 and the first nine months of 2012.

As the above graph shows, this event, while record-setting, is by no means an outlier. The loss of sea ice has been accelerating since the 50s, and the sea ice has drastically declined in the past five years or so. An important measurement to point out is that the winter sea ice cover has changed relatively little - from ~15.5 million square kilometers to 14.5 square kilometers. However, the summer ice extent has dropped drastically - from ~11 million square kilometers to ~ 6 million square kilometers.

This graph begs the question: why has the change in summer ice been so much more drastic than winter ice? Well, this graph measures ice extent, and not the thickness of ice. As the Earth becomes warmer due to global warming (which is very real and very serious - see my post here), the ice thins, so it takes less heat to expose a certain amount of water. Add this with the positive feedback of the albedo of water being much lower than the albedo of sea ice, and you have a recipe for disaster... a polar ice cap that is dying before our very eyes. In the mid 2000s, the scientific consensus was that the arctic would be ice-free in the summer by 2040 or 2050. But as there has been a drastic decline in sea ice in the past five years, most scientists predict that arctic summer sea ice will be completely gone by 2030, and some radical estimates show it being completely gone by as soon as 2016.

 This general sequence of editing previous estimates to become more dire is pretty common, especially when it comes to ice caps and sheets, both on land and on the ocean. The summer sea ice extent has declined at ~12% per decade, which is far more than the 2007 IPCC's "worst case scenario."

Retrieved from Kinnard et al.'s 2011 paper: Reconstructed changes in Arctic Sea Ice over the past 1,450 years.

Here's a longer term graph of average sea ice extent. Needless to say, this type of warming is unprecedented in this graph, and according to climate proxies such as ocean sediments and ice cores, perhaps much longer.

Interestingly enough, in the article I got this information from showed that the Antarctic sea ice extent was actually growing instead of shrinking, even as the air temperature by the southern oceans has begun to rise.

Why is this? Bear with me here, because the reasons are complex. First off, the water at the surface of the Antarctic Ocean (specifically the Weddell Sea) is actually colder than the deeper water because of the cold air temperatures at the surface. This warm water upwells and melts sea ice. However, there has been an increase in precipitation in recent years as the air temperatures have warmed. This does two things: 1.) the snow acts to expand ice caps, and 2.) the surface water freshens because of the increased precipitation, which leads to a more stratified ocean where the water mixes less easily, and since the decreased salinity in the surface ocean decreases the density, the water from the surface ocean does not sink as easily, and the warmer water from the ocean bottom, which acts to melt the ice, rises more slowly, so less ice is melted.

It is very important to look at everything that is changing in our climate, whether there is a decrease or increase in temperature and/or ice caps. This can go both ways... global warming deniers will specifically point out places where ice is expanding (like the Antarctic) and say that global warming is nonsense, and some global warming activists only point out places where the Earth is warming and ice cover is decreasing. Both of these methods are flawed. The only way we can definitively prove that the Earth, as a whole, as warming, is by looking at everything that is happening to our climate and taking an unbiased, scientific approach to an environmental change unlike anything the Earth has experienced for a very long time.

We have to go back 55 million years ago to the Paleoeocene - Eocene Thermal Maximum (PETM) to find an analog for the climate change the Earth will undergo in the future. But we have to be logical and scientific in our analysis of the problem, and we cannot specifically pick out data that supports global cooling or global warming. We have to look at all the data.

Charlie

Making Something Out of Nothing

Sunday, September 23, 2012

3:10 P.M.

It's been bad. Interesting weather is my drug of choice, and unlike most recreational drugs, it has good long term effects which include but are not limited to career opportunities, meeting new people, and the knowledge to impress and win the hearts of millions in the Seattle metropolitan area.

But like most drugs, weather has a dark side. It is addictive, and therefore, when there is no interesting weather to be found, withdrawal symptoms occur. The main symptom is my constant staring at models, hoping for something to magically change in them, but alas, no change is to be found at this time. Of course, there are ways to cope, such as looking at weather happening in other parts of the world, or reminiscing on past weather events, such as the Hanukkah Eve Storm of 2006, the Great Coastal Gale of 2007, and the Awesome Phillips' Snow Forecast of January 17, 2012.

So what do we do now?

Well, first, let's look at the weather models to see if anything has changed. I'll take some snapshots from different times in the 12z GFS model run.

Valid 11:00 am PDT Sun, 23 Sep 2012 - 6hr Fcst - 12z GFS 1000-500mb thickness, 6 hour precip, SLP

There is a huge ridge over our area, with storms being directed north into Alaska. Super boring.

Valid 05:00 am PDT Wed, 26 Sep 2012 - 72hr Fcst - 12z GFS 1000-500mb thickness, 6 hour precip, SLP

Almost the exact same setup. Storms over Alaska, but nothing here.

Valid 05:00 pm PDT Sun, 30 Sep 2012 - 180hr Fcst - 12z GFS 1000-500mb thickness, 6 hour precip, SLP

Same darn thing! Alaskan storms, but a huge ridge over us.

Ok, let's go out to 384 hours, which is the furthest the GFS goes out.

Valid  05:00 am PDT Tue, 9 Oct 2012 - 384 hours Fcst - 12z GFS 1000-500mb thickness, 6 hour precip, SLP

It looks like a weak front MIGHT hit the area. And sadly, that's the most interesting thing in the extended.

Most of you who read this blog know that a 384 hour forecast is useless. In fact, on October 9th, I'll post the same model run, and we'll see how similar the two model charts are.

But, by writing a weather blog, I made something out of nothing.

To my UW com-padres, enjoy the beginning of the school year (school starts tomorrow).

Charlie

Sunshine As Far As The Models Can Calculate

Saturday, September 15, 2012
9:56 P.M.

If you don't recognize this sun, you obviously missed out on some great children's 'tele'vision shows

Folks, I have never seen Seattle be as dry for as long as it has been this past year. And although I'm only 19 years old, I bet many older folks can't remember the last time it has been this dry. We had 48 consecutive dry days, and almost surpassed the 1951 record of 51. I was absolutely infuriated that .02 inches of rain fell and ended our near-record run and have regrets about not sneaking up to the Sea-Tac rain gauge and covering it with some plastic for those couple showers, but life goes on, and according to the weather models, sunshine does too.

Let's take a look at our current situation. Here's a infrared satellite shot from this evening with some 500mb height lines laid over it. It is important to note that these 500mb lines are lines are NOT isobars. Isobars delineate differences in pressure, where as these 500mb height lines delineate the contours of the altitude at which the pressure is 500mb. The two are definitely related though. High heights generally correspond to high pressure because there is more "distance" for the atmosphere to reach 500mb in pressure if the surface pressure is high. For example, if the surface pressure is 1030mb, the atmosphere has to decrease 530 mb in pressure before it reaches 500mb. If the surface pressure was only 980 mb, the atmosphere would only have to decrease 480 mb, and since 480 is less than 530, the distance it would take it would take for the pressure in both circumstances to reach 500mb would be less for a place with a surface pressure of 980 mb, and the height of the 500mb line would be lower.

However, the heights are not only dependent on pressure but on temperature as well. Places near the equator have very high heights because the air mass there is warm and not very dense, so there is a small vertical pressure gradient. On the other hand, heights at the poles are generally very low (especially in winter). There, the air is cold and dense, and the molecules are packed closer together there than an area with warm air. In this situation, the 500mb height line is low because the vertical gradient of pressure difference in the atmosphere is high compared to warmer climates

Ok, here's your satellite shot. :)

High height lines over the eastern Pacific, so we can infer that there is an area of high pressure here. If you take a look further north, you can see that there is some interesting weather happening up in Alaska, but let's be honest, there's always interesting weather occurring somewhere in Alaska.

Now, let's look at what UW WRF-GFS model says is happening over our area right now.

Valid 05:00 pm PDT Sat, 15 Sep 2012 - UW 36km 00z WRF-GFS 500mb thickness, SLP

Here are both the height lines and the pressure lines (isobars) on the same chart. As you can see, they line up fairly well. The biggest discrepancy in height lines and isobars in this graphic is on the west side of that Alaska storm, where the counterclockwise rotation of the low is bringing colder, denser, polar air southward.

And of course, over our area, the weather is more boring than an atheist in a church. High pressure to our west is blocking any sort of, well, anything, entering our area, and all we are left with is nothing. Hence, sunny days, with an occasional cloud making a brief appearance. 

Let's take a look at the same 500mb SLP chart 120 hours later.

Valid 05:00 pm PDT Thu, 20 Sep 2012 - 120hr Fcst - UW 36km 00z WRF-GFS 500mb thickness, SLP

That, my friends, is a gigantic ridge of high pressure. So it looks as though our dry weather will continue for the next five days. What about beyond that?

Valid 05:00 am PDT Sun, 23 Sep 2012 - 180hr Fcst - UW 36km 00z WRF-GFS 500mb thickness, SLP

Our ridge has moved a bit to the east, but is still very intact and protecting us from any storms. 180 hours is as far as the UW WRF-GFS goes out. 

But, let's see if we can go any further. Will we ever see rain?

Valid 05:00 am PDT Tue, 2 Oct 2012 - 384hr Fcst - NCEP GFS 1000-500mb thickness, SLP, 6 hour precip

Now, I generally don't put any stock in these forecasts because they are practically useless by day 16, but believe it or not, this is the rainiest day in the whole 00z GFS model run. It is also the last frame. See that tiny bit of green over Western Washington that might extend into Seattle? That's the most significant thing in the foreseeable future, even if the models aren't very good at foreseeing it.

In the mean time, water your lawns, use sunscreen, and go swimming. Even with the days becoming shorter, the water temperatures are still pretty warm right now because we have been above average in the temperature category in addition to below average in the precipitation category. Take a look at the temperature data for the Matthews Beach over the summer.

Great for taking a dip in the lake, or, better yet, fishing. There are some big, fat, hungry perch and bass in that lake right now, and now's the time to get them before the water gets colder and they become more sluggish.

I know that's what I'll be doing :)

Charlie Phillips

El Niño–Southern Oscillation (ENSO) - For Dummies

Tuesday, September 11, 2012
9:17 P.M.

 It's El Niño–Southern Oscillation...

...For Dummies!

Let me first start out by saying no copyright infringement is intended. I know that doesn't change anything, but it makes people less likely to sue you for "stealing intellectual property." Nobody likes a thief, but people are generally kinder to thieves with good intentions, like Robin Hood.

Since there's not much in the way of immediate weather, I thought I'd give all my readers the latest on the El Niño developing in the tropical Pacific. But then, it occurred to me that I may have not previously written an article on what El Niño–Southern Oscillation (ENSO) actually is. It turns out I have, but it doesn't have any fancy illustrations, and was written back in the days when I was doing this blog on Facebook (2008-2009). I posted all my previous blog entries from Facebook onto this website a couple years back. If you want to read it, you can find it here.

Also, if you want to join my group on Facebook, by all means, do so. Since there was that weird group format change thingy, I've been the only member. Even though I don't write the blog there, I post links to this blog, and all you weather nerds can ask me questions on there, or praise me for being the best weather forecaster the world has ever seen, or (God forbid), launch an assault on my soul when snow doesn't fall, and your term paper I said you could put off for a couple days is due. My Facebook group is here.

So, let's get down to business.

_________________________________________________________________

El Niño–Southern Oscillation (ENSO) is the name given to the cycle of the semi-periodic warming and cooling of the tropical eastern Pacific. There are three stages to the entire oscillation: El Niño, La Niña, and "neutral," in which the tropical eastern Pacific is neither in an El Niño or La Niña state. El Niño events are characterized by warmer than average sea-surface temperatures in the eastern tropical Pacific. They generally become apparent in spring, peak around Christmas, occur every 3-5 years, and last for 9-12 months. La Niña events where the sea-surface temperatures are cooler than normal in the eastern tropical Pacific. They also become apparent in spring, peak around Christmas, occur every 3-5 years, and last for 9-12 months, but they can last for 1-3 years. El Niño is Spanish for "little boy," which refers to the "Christ child" (baby Jesus) because El Niños peak around Christmastime. La Niña is Spanish for "little girl."

Closely related to the fluctuations in oceanic temperatures are large-scale changes in atmospheric pressure, and resulting differences in trade wind patterns. During neutral events, the air pressure in the western tropical Pacific is lower than the air pressure in the eastern tropical Pacific, causing the trade winds to blow from east to west. During El Niño events, the air pressure in the western tropical Pacific rises, and the air pressure in the eastern tropical Pacific falls, which acts to reduce the pressure gradients between the two locations and decrease the strength of the trade winds as a result. In La Niña events, the normally lower pressure over the western tropical Pacific gets lower, and the normally higher pressure over the eastern tropical Pacific gets higher, which results in a strengthening of the trade winds. The trade winds are essential to the whole ENSO cycle, and they are the driving force behind the differences in water temperature in the eastern tropical Pacific during different respective events.

A picture's worth a thousand words, so let's take a look at some pictures of neutral, El Niño, and La Niña events.

Retrieved from University of Miami ORCA Website

Before we go any further, let me define the temperature thresholds for El Niño and La Niña events. An El Niño event is characterized by temperatures that are .5 degrees Celsius above average in Niño 3.4, and a La Niña event has temperatures that are .5 degrees Celsius below average in the same region. Neutral events have anomalies that are less than .5 degrees Celsius above or below average in Niño 3.4.

Now, here is a diagram for what the atmosphere and ocean look like during neutral events.

Neutral Conditions - Retrieved from the NWS' JetStream website

Air sinks over the eastern tropical Pacific, where there is higher pressure, and air rises over the western tropical Pacific, where there is lower pressure. The trade winds flow from east to west, and push the warm, surface water over towards Indonesia, while cooler, deeper, more nutrient-rich water upwells off the coast of Peru. The upwelling off the South American coast makes for some extremely productive fishing grounds. Because the trade winds are constantly pushing water to the west, the sea surface height in the west is about half a meter higher than it is in the east.

Neutral Conditions - Retrieved from the NWS' Climate Prediction Center Website

Neutral conditions keep the Pacific Northwest near average in terms of temperature and precipitation, but our biggest storms generally come on neutral years. The rest of the diagram is self-explanatory... neutral conditions generally lead to typical (average) meteorological conditions throughout North America.

Neutral Conditions in the Summer of 2008 - Retrieved from the NWS' Climate Prediction Center website

Above are the sea surface temperatures during a neutral event. There looks to be a small pool of warm water off South America, but this still qualifies as neutral conditions, as the temperature anomalies in Niño 3.4 are less than .5 degrees Celsius.

Now, for El Niño!

El Niño Conditions - Retrieved from the NWS' JetStream website

In El Niño events, the trade winds are weaker, and in this picture, they even slightly reverse in the western Pacific. Since the trade winds are weaker because of less atmospheric pressure differences, there is less upwelling off the coast of Peru, and therefore less cold water is arising from the deep, leading to warmer water temperatures in the eastern tropical Pacific. The thermocline is "flatter" throughout the ocean, and the whole tropical Pacific is more homogeneous in terms of temperature and nutrient concentration. El Niños are bad news for the Peruvian anchovy fisheries, as fewer available nutrients means that there are fewer anchovies. This picture doesn't show it well, but there is not much of a difference in sea surface height between the eastern and western tropical Pacific during an El Niño event.

El Niño Conditions - Retrieved from the NWS' Climate Prediction Center Website

During an El Niño winter, the northern half of the US is warmer and drier than normal, and the southern half is cooler and wetter than normal. Southern California is generally a boring place to be as far as weather is concerned, but they can have some pretty intense storms roll through there during El Niño years. I strongly dislike El Niño years because they typically lead to boring winter weather, bad skiing conditions, and, because there is often reduced upwelling off our coast, less salmon. 

See that picture below? That's from the Russian River in California during March 1998, when it was getting pounded by heavy rains that were a result of the 1997-1998 El Niño.

Photo Credit: David Gatley/FEMA

Here is a great picture of sea surface temperatures (SST) during an El Niño event.

El Nino Conditions in 1997 - Retrieved from a EMS Penn State Website

During neutral years, SST are generally around 8 degrees Centigrade warmer in the western tropical Pacific than the eastern tropical Pacific, but in strong El Niño years like this one, the temperature difference can be less than 3 degrees C. 1997 was an exceptionally strong El Niño, most of them aren't this strong.

Whew!!! Two down, one to go. Now presenting: La Niña.

La Niña Conditions - Retrieved from the NWS' JetStream website

In La Niña events, the trade winds are stronger than normal, which leads to decreased temperatures off the Peruvian coast due to increased upwelling. Atmospherically, the pressure difference (high pressure in the east, low pressure in the west) is greater in La Niña years than neutral years, and this is what increases the strength of the trade winds. The thermocline is sharper because the pool of warm water in the western tropical Pacific is deeper than normal and the pool of warm water in the eastern tropical Pacific is very shallow. There is also more of a sea surface height difference, with the western tropical Pacific being over a half a meter higher than the eastern tropical Pacific. These pictures don't show the differences in sea surface height between neutral, El Niño, and La Niña events very well, but they are nice diagrams nonetheless. And, since there is a boatload of upwelling off Peru, boats generally have no problem with loading themselves up with copious amounts of anchovies.

La Niña Conditions - Retrieved from the NWS' Climate Prediction Center Website

During a La Niña winter, there is often a big fat ridge of high pressure over the eastern Pacific, and this ridge is generally far enough off our coast that we are not under its warm, dry influence. Instead, the jet stream slips down on the eastern side of the ridge from the Gulf of Alaska into our area, giving us cooler and wetter weather than normal. The winter isn't completely dominated by this northern branch of the jet stream though, as the jet stream coming off the Pacific sometimes sneaks in and gives us warm and wet weather. The southern part of the country is generally dry, and the Ohio Valley is wet. I'm a La Niña fanatic because La Niñas often bring gobs of snow to the mountains and they are good for salmon because there is usually increased upwelling off our coast.

La Niña Conditions in the Autumn of 2010 - Retrieved from the NWS' Climate Prediction Center website

2010-2011 was a big La Niña year, and this diagram above shows it well. The temperature departures in La Niñas usually aren't as big as those in El Niños, but they are significant nonetheless.

What's my favorite type of year? La Niña, of course! La Niña years are definitely the snowiest in the mountains and are often the snowiest in the lowlands. Here's a piece of personal history... this was taken in April of 2008, a huge La Niña year, and there was a ton of snow in the mountains. 

Even today, I stand by everything I said in that video. It was AWESOME!!!

Charlie

Sooooo close!!!

Monday, September 10, 2012

8:18 P.M.

.01 inches. The smallest measurable amount of precipitation possible. And that is what ruined our dry streak of 48 days.

I was actually thinking that Seattle might make it through this front without getting any rain. I was outside from 5 P.M. to 9 P.M. that night walking and running around Seattle with a fabulous friend, and we loved the breeze and prayed for a lack of rain. I was pretty tired when I got back home and took a nap.

I got back up at around 11:30 or so. Anxious to see if we had made it through the night without any rain, I quickly went to the UW Atmospheric Sciences weather website and looked at their radar. Much to my dismay, it looked like a small shower had made it through Sea-Tac while I was sleeping. I still had hope though. It didn't look like much, and we need measurable precipitation to end our streak, not just a trace.

I waited anxiously until midnight to check the weather statistics at Sea-Tac for the previous day. My hopes were high. I must confess, I am somewhat of a "wishcaster" (somebody whose forecasts are often based upon their personal wishes instead of empirical model, radar, and satellite data), and I really was hoping we made it through the night without measurable precipitation.

And then I saw that .01 inches of rain had fallen just before midnight Monday morning.

As my neurons transmitted this unfathomably disappointing information to my cerebral cortex, immediate psychological and physiological changes to my temperament and homeostasis occurred. The physiological changes were immediate: an increase in blood pressure, an increase in heart rate and pulse, an increase in body temperature, a decrease in salivary gland production, a dilating of the pupils, a flushing of the skin, violent convulsions, and minor (but still significant) amounts of steam exiting my ear canals. The psychological changes were profound as well, but they were manifested in different stages.

First, everything was numb. Lights looked brighter, and the few quiet sounds of the night, such as the ruffling of the leaves in the breeze, or the quiet hum of my computer hard drive, diminished until they were no longer audible. 

Then came the anger, and, along with it, disturbing impulsive thoughts, such as smashing the guitar I barely know how to play, or making my bed and ripping all the sheets off, and repeating the process. Thankfully, I did not act on any of these impulses, and around five minutes later, my fury subsided into a drowsy sadness, and I drifted off to sleep.

I know... I know... most of you could care less. But to me, this was a huge deal. Let me tell you another story. When I was at the ripe young age of 10, I ran a cross-country race, and I was in position to win, until I took a wrong turn the last 100 yards of the race, and had to settle for second place. I was a pretty competitive rapscallion back then, and second place, to me, simply meant that I was the best loser. But, I got over that flood of frustration in due time, and I have moved on since then.

And that is what I will plan to do with this 2nd place dry streak. You can't have everything in life, right? And in the 21 hours that have passed since my furious rage, I've learned to appreciate this dry streak for what it was, and look forward to the weather ahead.

The problem?

There's not much weather ahead.

Let's take a look at this evening's UW WRF-GFS model.

Valid 08:00 pm PDT Mon, 10 Sep 2012 - 3hr Fcst - UW 36km 00z WRF-GFS 500mb absolute vorticity, heights

You can see that the trough of low pressure has just passed our area, and a nice big ridge is waiting for us over the Pacific.

Valid 08:00 pm PDT Wed, 12 Sep 2012 - 51hr Fcst - UW 36km 00z WRF-GFS 500mb absolute vorticity, heights

That big ridge of high pressure is firmly implanted over us, and we will by dry and sunny. And honestly, I don't see this ridge moving much at all. It's a pretty safe bet that we will not see rain for at least ten more days. Temperature-wise, we will generally remain a few degrees above average. If you love hot weather though, look forward to Wednesday. Highs could reach the mid 80s in some locations.

Sooooo close!!!

Charlie

Bye Bye Dry Streak

Saturday, September 8, 2012
9:07 P.M.

As I write this blog, I'm listening to Miles Davis' and John Coltrane's famous rendition of "Bye Bye Blackbird." It's a wonderful song, but as I listen to Miles' soulful tone, I can't help but feel a bittersweet sentiment in my soul. Because for me, the "Blackbird" is not only this dry streak, but this summer mindset in general. It's time to say goodbye to the lazy, long days of summer and it's time to think about school. I have to say though, I'm definitely looking forward to my sophomore year at the University of Washington and the experience of surrounding yourself with a seemingly unlimited supply of wonderful people, enlightening schoolwork, and drugs/sex/rock&roll. Just kidding about that last one. Kinda ;).

But in all seriousness, this front symbolizes summer's departure and autumn's arrival. It's Mother Nature's way of refreshing our minds and helping prepare us for the changes we will all experience as the nights become longer, the leaves become redder, the temperatures become cooler, and the days become rainier.

What's responsible for ending such a long dry spell? Let's look at some satellite photos to find out! I'm gonna go back in time a little for you, so you can see how the front that will bring us the first rain we have had in 48 days has come about.

03:30 pm PDT Fri 07 Sep 2012 - Eastern Pacific Infrared Satellite

The temperature at Sea-Tac Airport reached 90 degrees on Friday, which was the first time it has done so in 22 years. If you look at the satellite photo above, you can see a HUGE ridge of high pressure over the area with clear skies over all of Washington and much of the Pacific Northwest.

Today, the temperature only reached 77 degrees. Why?

09:30 am PDT Sat 08 Sep 2012 - Eastern Pacific Infrared Satellite

It's tough to make out, but there are some high clouds over the Pacific Northwest, and the flow transitioned from strongly offshore to slightly onshore. Our once strong ridge weakened considerably today.

Take a look at the latest satellite picture. The ridge has broken down even more, but more importantly, look at the Gulf of Alaska, and look at the center of low pressure that is beginning to form there. This, my friends, is the low pressure system that will give us the first rains we have seen in a very long time.

09:30 pm PDT Sat 08 Sep 2012 - Eastern Pacific Infrared Satellite

Obviously, you can't take satellite pictures in the future, but we do have a wonderful assortment of weather models that can do just that. Let's see what my favorite one, the UW WRF-GFS, says what the ultimate fate of this low pressure system will be.

Valid 11:00 pm PDT Sat, 08 Sep 2012 - 6hr Fcst - UW 36km WRF-GFS 3 hour precip

As of right now, there is a weak area of low pressure and some associated precipitation stretching from the Gulf of Alaska to the Queen Charlotte Islands.

But take a look at what is expected to happen a mere 12 hours later.

Valid 11:00 am PDT Sun, 09 Sep 2012 - 18hr Fcst - UW 36km WRF-GFS 3 hour precip

See that front? That's what's gonna bring the demise of our dry spell.

Here's a higher resolution model picture that shows you the 24-hour precipitation expected over our area from Sunday evening to Monday evening as the front brushes Washington.

Valid 05:00 pm PDT Mon, 10 Sep 2012 - 48hr Fcst - UW 4km WRF-GFS 24 hour precip

You can see that there is a little bit of precipitation over the Sea-Tac airport, and much more to the north, where a convergence zone is expected to form.

And, our dry spell will end.

Or will it?

Sorry, I couldn't help myself. :)

Charlie

It's Been 50 Days...

Thursday, September 6, 2012
10:24 P.M.

... since my last blog post.

Summer kind of does that to you. The more free time you have, the less you feel like doing. I've actually been quite busy with music and jobs, but that is no excuse for being off this blog for 50 days.

However, I do have one valid excuse, and that is that the Seattle-Tacoma International Airport has not seen any measurable rain in 46 days.

It's been boring, to say the least.

But as this dry spell has become longer and longer, my outlook on weather, and life in general, has changed.

Here's why. A 46-day long dry streak in Seattle is practically unheard of. There was a 51-day long dry streak in Seattle in 1951. I'd love to set a new record. Can we make it five more days?

Let's take a day-by-day precipitation analysis of the latest WRF-GFS UW model run to find out.

Some of the charts on that site are pretty tricky to read, but this one is pretty simple. Where there are colors, precipitation is expected to fall, and different colors respond to different amounts of precipitation.

Will we get to day 47?

Valid 05:00 pm PDT Fri, 07 Sep 2012 - 24hr Fcst - UW 12km 00z WRF-GFS 24 hour precip

Absolutely. Not a color to be found.

How about day 48?

Valid 05:00 pm PDT Sat, 08 Sep 2012 - 48hr Fcst - UW 12km 00z WRF-GFS 24 hour precip

Still clear over Seattle! But things start to get a little interesting on day 49.

Valid 05:00 pm PDT Sun, 09 Sep 2012 - 72hr Fcst - UW 12km 00z WRF-GFS 24 hour precip

Oh noes! The precipitation is infiltrating the Pacific Northwest. Seattle looks to stay dry for another day. Will the streak make it to 50?

Valid 05:00 pm PDT Mon, 10 Sep 2012 - 96hr Fcst - UW 12km 00z WRF-GFS 24 hour precip

The answer, in case you have poor eyes, is no. But there is hope! Weather models are not perfect, and there is a chance we could escape unscathed. I've never wished so hard for a dry day in my life.

Regardless of whether the streak gets broken, we look to be bone-dry for the foreseeable future. So go do something wet. Jump in the lake. Drink some orange juice. Make a slip-n-slide. But most of all, to all my friends and family, enjoy the rest of your summer. Because come November, there will be a lot more color on these maps.

Charlie