January 25, 2009
There was a little snow this morning and right now, but it isn't really amounting to much. It will continue a little longer and taper off this evening. Again, no accumulations are expected outside of a half inch on grassy areas on the highest hills.
Of greater interest to most of you is probably a fringe snow event on Tuesday morning. Models show a POSSIBLE lowland snow event Tuesday morning before switching to rain in the afternoon.
This is an extremely hard forecast... because temperatures will be right on the fringe. If it holds off at all, there will be no snow.
The precipitation would arrive in Seattle at around 6:00 A.M. This makes it even harder for me to predict if school will be closed.
In short, even if I do a pretty good job on this forecast, there will probably be errors. And I will probably get people repeatedly tell me I was wrong even if I was mostly right.
The rule of thumb to the public's perception of forecasting to the weatherman is: "When we are right, no one remembers. When we are wrong, no one forgets."
I'll keep details streaming in as they come. However, just telling you in advance... fringe snow events in Seattle are some of the hardest events to forecast in the world. We'll see what happens!
January 24, 2009
Ok. My little break is over. Finals were this week, and finals take priority over writing weather forecasts. Let's talk about what happened over the past week though.
In short, there was a HUGE ridge of high pressure creating very warm air aloft. This warm air aloft was very very stable, and it created an inversion. The cold, dense air hugged the ground, and the warmer, lighter air rose above it. This is called an inversion.
An inversion creates very little mixing because the air is very stable, and there is nothing to move it. That is why we had deteriorating air quality and fog in the Puget Sound area. Places with higher elevation, like Snoqualmie Pass, were actually warmer than Seattle many days because while Seattle was in the fog and cool air, Snoqualmie Pass was above the fog and in the warm sector of the inversion. That pattern stayed in place for a while, but it looks as though it is finally beginning to break down.
We will have a weak arctic air mass (nowhere near as strong as the one we saw in December) filter down into Western Washington. The air temperatures in the Seattle area actually will not be noticably different thanks to all fog preventing temperatures from getting too high over the past couple weeks, but the air temperatures aloft will get significantly colder.
We could have a couple fringe brushes with snow on Saturday night and Sunday morning, and maybe again Tuesday night, but this looks unlikely right now, and if it occurred, it would only be a couple inches or so. I'll keep you posted.
The extended looks very active and very wet, with lots of snow in the mountains. Which, I have concurred, is something we need after doing ski bus Friday.
January 14, 2009
I've taken a little hiatus lately because there hasn't really been much to talk about. We are under the influence of a HUGE ridge of high pressure that is bringing extremely warm air aloft and stagnant conditions down below.
High pressure is generally associated with sunshine. Why, you may ask, was it so cloudy today?
The answer is air stagnation and a very strong inversion. The the pressure is so high, and the air is so stable that very little mixing occurs. This leads to moisture being trapped in the lower levels of the atmosphere, and allows for fog and low stratus clouds to form.
What is an inversion, you may wonder? The answer is rather simple. An inversion is when there is air aloft that is warmer than air at the surface and it "caps" the surface air. This prevents mixing of the air masses and is often associated with fog, stratus clouds, and smog. We get our worst air quality when we have inversions.
The inversion we have is extremely strong. I checked the temperatures for the top of Alpental and the base of Summit West this morning, and the differences were astronomical. Summit West was in the mid-20s, and the top of Alpental was in the mid-50s! That is a HUGE difference in temperature with height. It is certainly possible that the temperature at the summit of Mt. Rainier (14,410 feet) could get a higher high temperature than Olympia, one place that usually gets thick fog and has gotten very thick fog lately. That isn't likely, but possible.
Forecasting high temperatures for places in the lowlands is really hard right now because the temperatures could vary as much as 20 degrees based on if you are in the fog or not.
I'll be safe and predict a high of 46 for Seattle tomorrow. We'll see what happens.
Long range models have been erratic but occasionally show possible arctic outbreaks a long ways out. It is WAY to early to make any predictions, but just letting you know.
January 10, 2008
It's been an awesome time for me with all this craziness, but now the fun must cease. We have one more system coming through. Then, models show...
The extended model (GFS Superensemble) shows dryness 16 days out.
Anyways, ya'll can look forward to sunny days with highs in the mid 50s.
January 9, 2008
I hate weather. It is the most boring thing in the world.
Okay... well I don't hate it... but I strongly dislike boring weather. It gives me nothing to do but work on other stuff (like AP Euro).
The highlight of this week is some rain Saturday afternoon and night. Otherwise, you can look forward to temperatures in the mid 50s and sunny skies for the next week. Long range models show rain back in the picture 10 days out... I don't know if what I'm gonna do with my spare time until then.
Hope you like boring weather more than I do...
ciao for now
January 8, 2009
You know what I really hate? Boring weather.
That's what we got now. My couple days of bliss are now over. Looking at the forecast models is too hard. The forecast is for painfully boring weather. >:(
Of course, everybody else is probably like "woohoo!"
Those looking for a break in the action will get what they want. Me? zzzzzzzzz...
Let's do a quick review of this storm. Needless to say, it was extremely wet. The first wave of moisture came through Tuesday morning. There was a quick break in the action, and then heavier rain arrived Tuesday afternoon. However, in the Seattle area, a rain shadow prevented rain from getting really heavy. Meanwhile, rain was falling at the rate of an inch per hour in spots.
And it didn't stop.
Wednesday evening, the upper-level flow became more southerly and the rain shadow shifted north as a result. Now, Seattle got a taste of what others had gotten for the last 36 hours.
On the rain shadow, I checked some rain totals around the Puget Sound lowlands, and it is amazing how drastic the differences in precipitation are from place to place. Places like Shoreline got a couple hundreths of an inch of rain up until Wednesday afternoon. Places like Tacoma, meanwhile, had around 4. That's a serious rainfall gradient. Just goes to show how complex weather forecasting in the Pacific Northwest is. You think people in Alabama have to worry about rain shadows?
The rain continued falling until early Thursday morning, ending at around 2 A.M. in the Seattle area.
But the damage was done.
Of particular note was the mudslide/avalanche at Hyak. I never thought that would ever happen. Hyak (Summit East at Snoqualmie) is not steep at all. It's also avalanche patrolled. I NEVER thought in my wildest dreams that an avalanche would happen there, let alone one as huge and destructive as that one.
As some rivers are still on the rise, flooding records are not complete. My cousins however, who live in Snoqualmie, said this flood was higher than any one they had ever seen. They've been through some unbelievable floods too (1990, 1996, 2006, just to name a few). The Snoqualmie crested higher than ever at Carnation, over 61 feet!
As I said before, this flooding situation was actually fairly different than the December 2007 floods. Those had very very very strong wind and had much worse impacts on the coast. A situation that closely parallels this were the November 2006 floods. Expect an in-depth analysis of this storm over the summer. In retrospect, the things that made this storm so destructive, especially for the Cascades, were the duration of time we got the heavy rain, the significant low-elevation snowmelt, the high freezing levels, the heaviness of the rain itself. The thing that really sets this storm apart though were the mid level (5,000 feet) winds. They weren't historically strong (unlike the December 2007 winds), but they were almost due west for most of the event. That's why the Seattle area got rain shadowed. However, these winds SLAMMED into the Cascades as the Cascades were perpendicular to the flow. This allowed for maximum oragraphic precipitation too occur. Again, I'll create a more extensive page on this sometime in the future, but the upper level winds put the word "historic" in this storm.
January 7, 2009
What's golden people? I'll tell you what's golden. The Snoqualmie River will crest higher than it's ever crested before. And who called it? Charlie Phillips > lots of numerical and statistical models.
Alright that's nothing to get cocky about. Any person with any sense knew that the hydro models were underdoing their river estimates. This is just cool cause it makes me feel good about myself, which is always a good thing (unless it turns you into a dick :) ).
The heavy rain is still forecast to taper off around 2 A.M. Tomorrow, I will have a quick update on this storm, and perhaps somewhere down the road, I will post a more in-depth page about it. In the weather off-season (ie late spring, summer, early fall) I may not do these forecasts since I will be out of town but I will work on researching individual events (mainly windstorms) but also flood and snow events.
In the meanwhile, my cousins in Snoqualmie say they are getting flooded more than ever. I went to Snoqualmie Falls earlier last fall (2008) when there was major flooding on it. I looked at reports from KING5 and this event looks much more major.
This storm is much more similar to the November 2006 event than the December 2007 event. More on that later, it's getting late.
Remember: go see Snoqualmie Falls at all costs tomorrow. You will thank me sometime down the road. You will.
This is beginning to look like the real deal folks. I just looked at the data for the Alpental ski resort as well, and they have gotten over 5 inches of rain in the last 15 hours. Several rivers are forecast to reach record severity flooding. The Snoqualmie River is expected to crest a couple inches below record stage. However, I think it will crest at record stage. We will have to see.
The rain shadow that has been keeping us dry while other places have been getting feet of rain has shifted to our north and weekend. This rain shadow, by the way, was extraordinarily strong. I thought there would be a little rain, but I thought there would be more than there was. There was no rain in Seattle this morning, while, to our west, east, north, and south, it was dumping. We are now seeing what everybody else has been seeing for the last 24 hours. It's not hard to realize why so many rivers are flooding when you take the rain we are getting now, make it heavier, and prolong it. That's what it's been like in the mountains. Freezing levels are at 7000 feet, so it is pretty much all rain in the mountains. This storm will be historic. KOMO says, "Heavy rains continue to fall across Western Washington as some areas could see flooding that we haven't seen in generations, if at all."
Still, while some rivers may be flooding at record severity, I got a question from Evan Shay about whether this storm is the same strength as the storm on December 1-3, 2007. It is not, and I can say that with confidence. Even though places in this storm may get even more rain, the December storm was shorter in duration as far as heavy rainfall is concerned and dropped more rain in a shorter amount of time. This biggest difference is wind. Wind is generally the best indicator of a storm's strength since the lower the pressure of a storm, the stronger the wind. Moisture doesn't have as direct of a connection to strength.
Bottom line on these two storms: The former was stronger, mainly because of wind, but this one will lead to flooding just like the other one. Because of upper level flow differences, the Olympics were favored more in 2007. Now, the Olympics and Cascades are favored. The Cascades have seen much more rainfall already than they did in 2007.
The steady rain is forecast to end around 2 AM in Seattle. Still, strong orographic flow will keep precipitation going in the mountains, although it will begin to wind down as well. Check out those links I posted in yesterday's post. AND GO TO SNOQUALMIE FALLS. YOU MAY NEVER SEE IT THIS HIGH AGAIN. I'VE GONE THERE IN SITUATIONS MUCH WEAKER THAN THIS AND IT WAS AMAZING. I doubt your parents will answer your pleas if you really want to go, but trust me... this is the highest I think that river will be for a long time.
Oh yeah, and we dry out tomorrow and keep dry for a week or so. Not much to talk about there... especially when the weather is like it is now.
Have fun in the rain!
January 6, 2009
Want to know what the NWS says on the situation?
THE OVERALL TREND IS NOT LOOKING GOOD WITH SOME VERY HIGH RAINFALL RATES STARTING TO COME IN THE PAST FEW HOURS
Yeah! That's what I'm talking about!
Precipitation rates look even higher. Isolated amounts of 30, yes, 30 inches are possible in spots. Widespread amounts of 10-15 inches are certain. Avalanche danger is extreme. Rain was falling at the rate of an inch per hour north and east of us. Again, the rain here isn't that bad as of now. There has already been over 5 inches in the past several hours in some spots on the Cascades and Olympics. If you live in a floodplain, move valuables to higher ground. AND SEE SNOQUALMIE FALLS IF YOU CAN. I GET THE FEELING THAT THE SNOQUALMIE RIVER COULD CREST AT AN ALL TIME FLOOD STAGE, EVEN THOUGH THE HYDRO MODELS DON'T AGREE. IT ALL DEPENDS ON HOW LONG THIS RAIN LASTS.
Stay dry under the Olympic rain shadow!
Even if it's not raining at your house right now, it is raining very hard elsewhere. The Seattle metropolitan area is getting shadowed by the Olympics right now. Take a look at the radar, and you can clearly see a lot of rain in other parts of Western Washington. http://www.komonews.com/weather/radar
This shadow, however, will shift further north as time goes on. Therefore, Seattle will eventually get all the heavy rain everybody else is getting. The NWS is expecting 4 inches of rain in Seattle. I think we will see totals closer to 2-3 inches in Seattle proper, but places like Sea-Tac, which are currently not affected by the rain shadow, could see total rainfall amounts close to 5 inches. The Cascades and SW Olympics could see 15-20 inches of rainfall. That is a phenomenal amount of rain, and with all that rain comes flooding. I can say confidently that we will see moderate to major flooding on all area rivers, maybe even a few records. I highly encourage everybody to check out Snoqualmie Falls if they have time. It will be dramatic.
In the meanwhile, we have a little wind in the Seattle area. A wind advisory is in effect for most of Western Washington. We could see wind gusts to 45 mph, which is enough to cause some localized and isolated power outages. The main story over the next few days will be the rain and associated flooding. Here is a great website to see the stages of the rivers and their predicted heights.
Click on the names of places to see the forecast for the river and more specific information on it.
Remember: If you are up for an adventure and your parents are too, head to Snoqualmie Falls. It is forecast to reach major flooding at this point and may go even approach record stage.
And there is no snow for Seattle in the foreseeable future :)
January 5, 2009
So actually, I just looked at the models and all guidance points to a major flood event for Western Washington. Our most dependable model for the region, the 4 km mm5-gfs, shows a constant, heavy rainfall from 1 A.M. Tuesday morning to 10 A.M. Thursday morning. A rain shadow will protect Seattle from excessive rainfall at first as the flow is westerly, but the shadow will shift north as the upper level flow gets more of a southerly component. models now show rainfall totals as high as 20 inches in the Cascades. Many tv stations are calling for urban flooding, but I don't think it will be that bad due to the rain shadow. We could see some urban flooding when the rain shadow moves north closer to Everett. Bottom line: even if it's not raining here, it's raining elsewhere. HARD. I suggest you go to see Snoqualmie Falls if you can get a ride. It is unbelievable when the river is at major flood stage.
See snow totals HERE: http://www.facebook.com/group.php?gid=33875355514&v=app_2373072738#!/topic.php?uid=33875355514&topic=6006
Let's start out with a review of last night's storm. I actually thought I did a great job of forecasting it. The snow switched to rain at around 11 at my house, but switched later at other places (Mr. Stever, my marine biology teacher, said it turned to rain at 3 A.M. in Shoreline).
Just to get a couple things straight, I did NOT say there was a 10/100 chance of snow. I was fairly certain that there was going snow, and predicted a couple inches in my forecast. I was 10% sure that there was going to be a snow DAY, as I thought the rain would turn the snow into slush.
Things I learned from this: Fringe snow forecasting is really hard. I already knew that, but this just reinforced it. With the temperatures the way they were, a quarter of the time you would see snow, half the time you would see a rain/snow mix, and a quarter of the time you would see rain (that's at least what I think). We got more snow than I expected, and I'm afraid there's not really much I can learn from that. It wasn't a forecasting error or anything. It's just the nature of snow around here. You really have to see the snow falling before you can really put down some hard forecasts in these fringe situations, which is often too late.
I will confess, however, that I was fairly certain that we would have a late start. This wasn't a forecasting error though. I tried to predict SPS, who I've learned is very hard to predict. I thought they would delay because of all the slush on the road. I think they got impatient with all the snow days and just wanted kids to go to school. Even if I can predict weather, predicting the inner thoughts of school officials is even harder.
So... I thought I did well in this situation, but not much better than any other guys. This wasn't really a typical forecasting scenario. It was a "look out the window and see what's happening scenario." Anybody could have predicted this if they knew some basic signs to look for.
This week looks WET. We could see some flooding on area rivers, and after that, we could see a perhaps fairly extended (5-7 days) period of dry weather (which everybody loves except me). I'll right more on it later tonight after the UW models come out. They are one of my best resources.
January 4, 2009
So... it's actually kinda snowing! Awesome for some, problemsome for others. I am looking outside right now, and frankly, I did not expect to see this much of snow (I have about a 1/2 inch outside my house right now). Neither did the NWS. They have issued a SNOW ADVISORY until 9 P.M. for all of Western Washington for 1-3 inches of snow. However, I think that it MAY keep snowing beyond that point. Here's why...
1.) snow acts to keep temperatures cool, and the atmosphere has cooled off from the snow.
2.) the precipitation is fairly intense due to some weak low-level convergence over Seattle and especially Bremerton. When precipitation rates are higher, it brings cooler air down to the surface and gives the snow less time to melt
3.) Cause Chris Swanson controls the weather and he says we are going to have a snow day
This is what you call a fringe snow event. Temperatures are RIGHT on the fringe. The temperature at my house is 34 degrees. Thankfully, dew points are low enough and precipitation rates are intense enough that the precipitation is remaining as snow.
All the other forecasters and the models are in agreement that the snow will change to rain at 9-midnight. I'm starting to head for the later part of that range. I've seen some helpful signs that we could see more snow. The snowflakes are getting smaller (which means the snow is drier, although it is still very wet) and snow is sticking. This is a very tough forecast and I'm listening to every single clue I can get to make a decision.
Models operate my pure mathematical equations. There is some weather wisdom you can incorporate into your forecasts in these times. For example, snow helps to keep temperatures steady. Models say rain tomorrow morning at Snoqualmie Pass. I don't think so. The storm coming in isn't all that warm.
Another good indicator more snow is that southerly winds have died down. We have less of a warming wind to eat away the snow and change the precipitation to rain.
Bottom line... this is a very difficult forecast. But I think that it will continue snowing for a couple hours, and then the precipitation will change over to rain. The best resources at this time are just temperatures and observations from other places. I am hoping for a snow day, but that looks unlikely. However, I have bumped my odds from 1 in 100 to 10 in 100. A 2 hour late start seems much more likely.
Feel free to ask me any questions, but just write them on the wall here. I will answer them. All the chat spazzes out my computer. Your best resource at this time is simply doppler radar and your temperature gage.
ONE MORE SNOW DAY!
Looking at the models this morning, it looks as though there is a slight possibility that the Seattle area may see a little bit of light snow. The most advanced model we have (the 4km mm5-gfs) shows 2 inches of snow in the Seattle metropolitan area tonight as moisture from the Pacific comes streaming in over a marginally cool airmass. The latest satellite observations show that the storm may be slowing up, which does not bode well for snow, but still we could see a slushy inch or two. Later tonight, it will all change to rain. I guess there is a slight possibility that we could have a 2 hour late start tomorrow, but that looks unlikeley. The snow will probably melt and probably not really stick to the roads anyway.
Hood Canal could now see as much as 8 inches in isolated spots, the easterly outflow of cold air dams up against the Olympics there. This does two things: it increases precipitation (because of orographic enhancement) and it cools temperatures (because the air there is cooler). Hood Canal also has a bit of elevation in spots, which helps to keep snow there.
The mountains will see snow regardless. 1-3 feet is still on track for totals from this incoming storm.
Of greater interest is the middle of the week. Models show a very wet and mild pattern with very heavy rain in Western Washington. Seattle may get shadowed by the Olympics, but the mountains will see very heavy rain, and very heavy snow above 6-7000 feet. The models show over 60 inches of snow in a 24 hour period in those spots. Unfortunately, it looks like it will rain in the passes. The rivers look like they are going to flood and there could be some avalanche danger. Stay tuned.
January 3, 2009
Happy New Year Everyone!
I hope everybody had a fantastic New Year, and I hope it will be filled with excitement, love, and other goodies. Out with the old and in with the new! Woohoo!
First, before I explain the forecast, I want to go over a concept that isn't particularly advanced but is rather unknown to much of the greater Seattle area. What if I told you that the snow we get isn't always snow?
Everybody knows what snow looks like... it's white, it's fluffy, and it sticks to trees. Still, not all white things that fall from the sky are snow.
Today was a good example of a time when there was white stuff falling from the sky that wasn't really snow. If fell in pellets, and bounced high when it hit the ground. It isn't hail either though. It's graupel!
Graupel are kinda like snow pellets. They lack the hexagonal structure of a snowflake, but they are not hail either. Many people say we are getting hailed on when they see graupel. I don't know why they don't teach this in the schools. It's one of the biggest weather misconceptions I've noticed.
These pellets are not hail because hail is formed of ice, whereas graupel are still snowy and squishy. Hail are also generally clear, and graupel are white.You can have white hail, but you can NEVER have clear graupel.
To find out if it's hail or graupel, just pick up the sphere and squish it. If it's squishy, it's graupel. If it's ice, it's hail.
Hail is formed inside of a cloud when supercooled (liquid below 32 degrees) water droplets attach to each other and ice over. I'm not sure how graupel is produced, but it's not that way.
I've noticed that graupel usually occurs on cool days a really unstable atmosphere, or in a REALLY intense convergence zone. So for now on, when you see these snow pellets, I want your status to be "It's graupeling outside!"
Alright. The forecast looks fairly interesting, especially for midweek. We will get a strong warm front off the Pacific tomorrow and Monday that will provide breezy conditions, some rain, and gobs of snow in the mountains. The lowlands by Hood Canal may even see 2-4 inches of snow when the precipitation starts, as the airmass we have now is marginally cool enough for snow. The Cascades will see 1-3 FEET, which is great news for ski resorts. Still, the avalanche danger will be extremely high, so this is not a good time to be in the backcountry. I-90 may also close for avalanche control.
Tuesday-Thursday is where it gets interesting. A Pinapple Express will move through the area, blasting snow levels up to 7000 feet. This one looks fairly strong, and it will stall over our area, bringing very heavy rain to the mountains and extremely (several feet per day) heavy snow above that level. With rain in the mountains comes the threat of river flooding. Those who live in floodplains should be warned that a moderate to possibly major flood event is possible the middle of next week.
Hey so I just did some more research on graupel... supercooled water droplets actually are involved. Instead of supercooled water droplets sticking to each other and making compact ice, graupel is a coating of ice formed from supercooled water droplets around a snowflake. It is formed in convective atmospheres (ones with a lot of instability... like the ones we get with convergence zones and strong showers). All these graupel falling also produce a lot of static electricity in the air, which explains why I almost got struck my lightning razor clamming on the coast last year (it was graupeling at the time).