Thursday, September 23, 2010

Guess who's back, back again

Thursday, September 23, 2010
8:29 P.M.

Yup, you guessed it, the rain is BACK in the forecast. We had different scenarios being forecasted by two different models. The American GFS model was forecasting dry and warm, with rain going right to the north of us, while the European ECMWF was forecasting rain. Naturally, we believed our own forecasting model, because we think that everything about America is way better than our inferior relatives across the pond. However, it's no secret that the ECMWF is a better forecasting model, especially for the long run. We just generally use our models because we have the amazing UW mm5 models for them, but yeah, long-range forecasting is the achilles heal of our models.

I'll have another, longer forecast later, I just have a bunch of hw to do.

Wednesday, September 22, 2010

The Next Storm to Watch

Wednesday, September 22, 2010
4:34 P.M.

As many of you have noticed, the U.S. hasn't been hit by a hurricane this year. We've come mighty close - one recurved off of the outer banks and one landed just south of Brownsville, but we have had no U.S. landfalls, which is phenomenal because this has been a very active hurricane season so far.

But we may get a hurricane landfall yet. There's another Cape Verde storm way out in the Atlantic, and it's not going to impact us. But there is an area of disorganized low pressure in the Caribbean, and this could very easily develop into something if conditions are favorable.

As the satellite image shows, there is a LOT of thunderstorm activity in the Caribbean. There is not much wind shear and there are warm water temperatures. The strongest hurricane on record occurred in the Caribbean in conditions like these back in 2005. It reached 882 millibars! The Columbus Day Storm, our strongest storm, was only a 960. Only a few storms ever go below 900, and no non-tropical storm that I know of has ever gone below 940. 882? That's crazy. It was Hurricane Wilma, and at peak intensity, it had the smallest eye on record, being 2 nautical miles in diameter. Most eyes are like 40 nm across.

See if you can make out the eye in this picture. It is visible, but barely. Wilma also occurred in mid-October when water temperatures were cooler. Evidently, they weren't cool enough to prevent hurricane formation. I'll keep you posted for updates on the situation in the Caribbean!.

Tuesday, September 21, 2010

Tropical Moisture - A Weather Model's Worst Enemy

September 21, 2010
5:43 P.M.
Hey guys, I have some breaking news! Ok, just kidding, it's not really breaking news. The weather models are acting up (I wish they weren't, THAT would be breaking news!). Tropical systems are being entrained in the westerly flow. This doesn't necessarily mean we will have a big storm (although since there are high PW values, we could get a good dose of rain). What it DOES mean is that the computer models are all over the place. They typically have a hard time deciphering what will exactly occur in situations like this, and this specific situation is no different. Take a look at the forecast model yesterday showing a large low pressure center off of our coast early Monday...

And now look at what today's run gave for the same time; a much weaker storm that actually doesn't even end up hitting the coast at all (goes north into the Alaskan panhandle).
As you can see, these are vastly different scenarios, and if you looked at the other frames following them, you'd see even more drastic differences in the way they unfold. One could give a solid inch of rain to the lowlands in 24 hours with much more in the mountains, as well as generating swells in the region of 15-20 feet. On the other hand, the latter, more recent solution doesn't even impact us. Hopefully, as forecasting technology gets better, occurances like these will be more common. Now you can see why the National Weather Service can have a tough time forecasting storms!

Wednesday, September 15, 2010

Our forecast and the hurricane season in the Atlantic

Wednesday, September 15, 2010
4:15 P.M.

Greetings my friends! Recently, we've seen a gradual transition to fall from summer. The days are getting shorter, and they are also getting cloudier and rainier. Up until now, though, we've been in pretty good shape. Unfortunately for you sun fans, this rain coming in today will be the first of many rainfalls throughout this La Nina winter, as forecast models show no real strong ridge of high pressure over the area anytime soon and show some weak systems coming through. The systems will get stronger in nature as we head into October, and they will be in full-force by November, peaking near Thanksgiving if statistics are anything to base predictions on. Until then, we will keep it showery in the short term. Expect showers tonight, and another frontal system will arrive on Friday, giving us periods of rain lasting into Saturday morning. The Husky game in the afternoon and Sunday will feature frequent showers, with isolated ones on Monday.

And ok, I lied, we might see some sun next week after Tuesday as a week ridge of high pressure takes over. But it's gonna be just that - a weak ridge of high pressure, and I don't expect it to warm us up at all (we will still be cooler than average). We will also still have a lot of cloud cover.

Ok, the weather is boring here. Nothing new for this time of year. But in the Atlantic, a debate continues. Has this year's hurricane season been a boom or a bust? There have been tons of hurricanes, and there are three storms out there currently. We have Tropical Storm Karl and Hurricanes Igor and Julia, and none pose a threat to land. But that is an awful lot of storms to have at once. You can clearly see Igor (big hurricane in the middle) in this satellite picture, and it once was a Category 4 storm with 155 mile per hour winds. That is almost a Cat-5. Julia is also a major hurricane with 135 mph winds and is to the east of Igor. This is the first time we have had two major hurricanes occuring simultaneously in the Atlantic basin. On one level, this hurricane season seems ferocious. And it is.

But it isn't! We haven't had ONE U.S. landfall, which is very unusual. All of the Cape Verde storms have been curling off to the northeast, and while we have had some storms in the Gulf (and they have intensified VERY rapidly) they have not been over water long enough to strengthen and have made landfall over Mexico, like Karl is expected to. So in that way, the season has been a bust. I kinda wanted to see a hurricane, but it's good for the U.S. that there have been no landfalls because they can cause massive death and destruction, and we don't want that, no matter how amazing a storm is.

Tuesday, September 14, 2010

Some more recent storms

Tuesday, September 14, 2010
3:21 P.M.

After the Columbus Day Storm, we would be without a major storm for some
time. But we had a major windstorm on November 13, 1981. This storm was actually similar to the Columbus Day Storm in depth and track, but its track took it a lit
tle further offshore, preventing the gradients around the area from getting too bad and keeping the strongest ones out at sea. It also moved northward at a slower pace, resulting in lower wind speeds. It was still a major storm though, as the above diagram shows. Pressure is in millibars. This diagram is from the Storm King website. Thanks to Wolf Read.

Another big storm struck in 1993, and on Inauguration Day of that year. He
nce, it is called the Inauguration Day Storm. While everybody was paying attention to ole' Williams induction to the presidency, few noticed the stellar forecasts by the National Weather Service forecasters. This storm was very important because it ma
rked the first major windstorm that we forecasted correctly. We didn't even forecast anything before the Columbus Day Storm, and before the 1/20/1993 storm forecasts were mediocre at best. But this was a successful forecast. And 700,000 people lost power, that too. Seattle's third most devastating storm since 1962 (with the Columbus Day Storm being #1 and the Hanukkah Eve Storm being #2)
1995 saw an absolute monster storm. It followed pretty much a perfect path for intense wind in Seattle and was extremely deep - 953 millibars. However, the Inauguration Day Storm generated stronger wind for us. Why? Because it was more compact. This stor
m was bigger, so the gradient was spread out over a wider area. Of course, that means a ton of areas got clobbered. Alaska to California, to be exact.

We got our 2nd most destructive storm on December 14-15 2006. It had roughly the same winds as the Inauguration Day Storm, but it caused far greater devastation. Why? Because of suburban development, sure, but mainly because the soil was so saturate
d from the previous November (15.63 inches of rain at Sea-Tac!). We also had some extremely heavy short-term rainfall, as this radar image shows. My house actually got pretty much bulls-eyed by it, and a woman who lived a couple miles away died when water flooded her house and she could not get out, sparking a complete re-do of the drainage system in Madison Valley. Se
a-Tac recorded its fastest gust ever at 69 mph, faster than the Columbus Day Storm. Of course, Renton gusted to 100 in the Columbus Day Storm and a little over 50 here, so the Columbus Day Storm was much stronger.

Recently, we had a very unusual storm. Well, ok, it was freshman year, but that's still pretty recent. Over December 1-3 2007, the coast got pounded with tons and tons of wind, and over the last 2 days, torrential rain resulted. Some places got 15 inches of rain in a day as the last storm came through. This main storm was very very deep at 953 millibars and was fed from multiple tropical sources. These events gave the strongest wind gusts on record for some locations, like Astoria. Even stronger than the Columbus Day Storm. Holy Cross in Pacific County reached 137 mph, Naselle ridge reached over 140. But what really made this storm devastating was the duration of the wind. I forget the details, but some place had high winds (gusts over 58) for something like 50 hours. Most locations on the coast have an 8 hour window of these winds. Inland, it is usually like 3 hours. 50 is just off the charts, and that, coupled with the extremely strong wind and extremely heavy rain, made this storm truly spectacular. I forget where I saw it, but I've seen publications saying that this combination of rain and wind is a 1000-year-event. The picture above? All those trees were standing before the event.

That just about wraps it up. I don't think we will have any big windstorms this year, as it is La Nina and we generally get then on ENSO-neutral years. But we certainly could have one.

Friday, September 10, 2010

How our strongest storms form

September 10, 2010

3:31 P.M.

Hey everybody. I'll pick up the tab on where we left off on yesterday. I must emphasize that the contents of this blog are not my own ideas, sure I'm not copying and
pasting (except for quotes), but I'm really relying on a variety of sources
including books by Glenn Miller and Cliff Mass, and of course Wolf Read's website. So give these guys credit for allowing my knowledge to grow to the point that it has.

On October 21, 1934, one of the strongest storms on record for Seattle. A degrading but still very tightly wound and deep low headed off Tattoosh Island and delivered a solid gale into the region. This storm was not as devastating for the coast as the 1921 storm but was much more devastating for the inland areas. Puget Sound recorded waves as high
as 20 feet, and an aircraft hangar at a Boeing plant actually got lifted off of the ground.

This storm may have actually been the strongest on record for the Seattle metro area, but it was not the strongest storm to hit the Pacific Northwest. There was one storm that hit in 1962 that caused unfathomable devastation throughout the Pacific Northwest, and this was the Columbus Day storm on October 12, 1962.

How did the Columbus Day Storm form? Well, like many of our absolute strongest storms, it had a very ample supply of moisture. In this case, the moisture actual
ly had a tropical source and was the remains of Typhoon Freda in the Pacific. The storm held this moisture as it was carried along the jetstream into our area of the woods, and as it got close, it sped up, turned northward (it had been previously going wes
t southwestward), and intensified into a compact, intense mid-latitude s

The Columbus Day Storm is the Holy Grail of all windstorms, and the storm that all others are compared to. Cape Blanco on the Oregon Coast recorded sustained winds of 145 miles per hour, Category-4 hurricane force. Most estimates pin gusts there at 179 mph, and I've seen one estimate at 195. Similar wind speeds were observed at exposed locations in Oregon and Washington such as the Tillamook Forest, the Mt. Hebo radar site, and Naselle Ridge. Even areas that were far inland received high gusts. Corvallis had a gust to 127. Portland had a gust to 116. Redmond had a gust to 100. And no, these amounts are not in km/h. There was over 10 billion board feet of timber blown down, and many 1000-year trees were blown down. What does that mean? That the Columbus Day storm could have been the event of the millennium. Nothing since the Columbus Day Storm has even come close in the strength of winds throughout such a wide area.

Pictures are of Corvallis (top) and Portland. Although Washington was also hard hit, Oregon took the brunt of the storm.

Thursday, September 9, 2010

Historical Windstorms of the Pacific Northwest

September 9, 2010
5:01 P.M.
While the weather is still pretty boring, I thought it would be a good idea to go over some different topics that are still related to weather, even if they aren't my own forecasts for the upcoming days. I'll cover a couple notable storms each day, going in chronological order.

The first big windstorm to hit the Pacific Northwest since the arrival and settlement of white men was on January 9, 1880. This storm was rather unique because although we don't have detailed measurements from back then, we do have some observations and approximations, and
I've found two things. First of all, it is important to point out that this storm came in from the southwest onto the northern Oregon coast when cold air was already in place around the PacNW. The result, especially for places north of the center of low pressure (and therefore receiving northerly winds) was intense snowfall. Seattle got 2 feet of snow total. The second point is that the damage looks to have been highly localized. Look at the graphic above, and look at the comparison between Astoria and Fort Clatsop. "Light damage" at Astoria vs. a "terrific west wind" at Fort Clatsop. This clearly illustrates the localized nature of this storm, in no doubt helped and aided by our mountainous topography. This picture came from Wolf Read's "The Storm King" website @ I love these guys' names. Wolf Read. Cliff Mass. Somehow Charlie Phillips doesn't seem to fit. Maybe Chuck Phil? Or as Adam Moshcatel likes to call me, C-Lips. Who knows.

I'll go over one more storm, the Olympic Blowdown of January 29, 1921. Again, reliable measurements were hard to come by in this age, but anecdotes and notes do exist and can give us an idea of what terrifying power this storm really beheld.

A weather bureau officer stationed at the North Head lighthouse (which recorded sustained winds of 113 miles per hour and a gust of 150, the strongest winds ever recorded in Washington excepting some occasional times on Naselle ridge) had this to say about the storm.

"The road from Ilwaco to North Head is through a heavy forest of spruce and hemlock timber for some distance. On the return trip shortly before reaching the heavy timber, the wind came with quite a heavy gust. We saw the top of a rotted tree break off and fall out of sight in the brush. About this time (near 3:20 p. m.) we were overtaken by a young man from the naval radio station at North Head who was driving a car. It is dangerous driving over this road under favorable conditions. We proceeded very slowly and with great care, passing over some large limbs that had fallen and through showers of spruce and hemlock twigs and small limbs blown from the trees. We soon came to a telephone pole across the roadway and brought our car to a stop, for a short distance beyond the pole an immense spruce tree lay across the road. We left the machines and started to run down the road toward a space in the forest where the timber was lighter. Just after leaving the car, I chance to look up and saw a limb sailing through the air toward us; I caught Mrs. Hill by the hand and we ran; and instant later the limb, which was about 12 inches in diameter, crashed where had stood. In three or four minutes we had climbed over two immense tree trunks and reached the place in which I thought was our only chance to escape serious injury or possibly death. The southeast wind roared through the forest, the falling trees crashed to the ground in every direction from where we stood. Many were broken off where their diameter was as much as 4 feet. A giant spruce fell across the roadway burying itself through the planks within 10 feet of where we stood. Three tops broke off and sailed through the air, some of the trees fell with a crash, others toppled over slowly as their roots were torn from the earth. In a few minute there were but two trees left standing that were dangerous to us and we watched every movement of their large trunks and comparatively small tops.

"Between 3:45 p. m. and 3:50 p. m. the wind shifted to the south and the velocity decreased to probably 100 miles or it may have been as low as 90 miles per hour. Shortly after 3:50 p. m. we started toward North Head. We climbed over some of the fallen trunks, crawled under others, and pushed our way through tangled masses of tops that lined the roadway. We supposed that all the houses at North Head had been leveled and the wireless station demolished for we knew that the storm was the most severe that had occurred in the vicinity of the mouth of the Columbia within the last 200 years. Mr. Seui, the young man from the radio station who was with us, hastened through the obstructions, and Mrs. Hill and I proceeded more slowly. About one-fourth of a mile from the station we were met by one of the men from the radio station, who had come to assist us had it been necessary. At 4:40 p. m. we arrived at the assistant lightkeeper's home where all the families of the Head had gathered for safety."

Wow. Yeah. That was a big one. The storm track for this was more typical of a region-wide windstorm, but it also was highly localized. Whereas several billion board feet of timber blew down on the coast, the inland areas escaped with light damage. But they would get their share of wind too. :)

And do yourself a favor and check out Wolf Read's website at That's where I'm getting these pictures and anecdotes from, and you'll find way more there than you will ever find here. Wolf Read is the man.

Wednesday, September 8, 2010

The Art of Inconsistency

September 8, 2010
2:30 P.M.

Have you ever looked at one eather forecast one day, seen it as forecasting rain, then seeing the forecast switch to sun, only to have it switch back to rain? That is what is happening in the models right now, and it is very, very hard to make accurate forecasts when models can't decide what path to take with a certain storm. It makes it particularly hard if all the models are doing this, which is what they have been doing.

Thankfully, they seem to be converging on a solution of sun Thursday and Friday, with light rain returning Saturday night and Sunday. This is September, so the sunshine won't be your July sunshine, and the storm won't be your typical November storm. Things will generally remain quiet and benign around here as summer transitions into fall. Fall transitioning into winter brings the big storms, and winter transitioning into spring often brings instability and heavy showers, but summer to fall (and spring to summer) are both fairly quiet as far as weather phenomena go.

Our long range forecast shows this low pressure trough hanging around for a while, directing cool air from the northern Pacific right in our neck of the woods from a westerly direction. The mountains, especially the Cascades, will likely pick up some decent orographic (topographically enhanced) precipitation, but the Seattle area will likely get rain shadowed. It depends on how much onshore flow there is, but we could also see a PSCZ form, although it is hard to predict convergence zones one day in advance, much less 5 days. But if this scenario shown in the models were to come true, I would expect a convergence zone of some sort, likely near the eastern entrance to the Strait of Juan de Fuca. Also, I expect we will be seeing a lot of these upper-level lows (although this is a very weak one) dropping down from the Gulf of Alaska and directing a cool westerly flow into the Cascades. This type of setup is not conductive to a lot of rain in Seattle (shadowed by the Olympics) or lowland snow but snow levels are usually around 1000 feet in the winter with these types of setups and snow can really pile up in the Cascades. I remember one such event in early February 2008 where Snoqualmie Pass got 7 feet in 4 days. 2007-2008 was a La Nina year much like the upcoming one, and Snoqualmie Pass got 50 feet of snow (as opposed to maybe 20 feet last year). I'm excited for it and I hope you are too.
Here is the latest update on the SSTs in the tropical Pacific. As you can see, there is a wide swath of cooler-than-average temperatures. This swath is only expected to grow with time, and La Nina itself will really start to have an impact on our weather after Christmas, although it will certainly have an impact before then as well.