June 30, 2010

Fourth of July Forecast and the Upcoming Heat Wave

We are about to repeat an age-old Northwest weather pattern. People complain about the "unusually" cool and cloudy June. The weather prediction for July 4th calls for clouds and a chance of showers, and somehow the fireworks just squeak bye on a cool, but acceptable night. And then the miracle occurs. Like a switch being flipped, our weather warms dramatically. The lawns turn brown and watering our vegetables and plants is mandatory. The best weather in the nation takes hold for roughly 2-3 months.

And it is about to happen again.
For the past weeks a persistent trough of low pressure has bedeviled the Northwest, bringing cooler and cloudier than normal conditions. But lets get one thing straight--June is typically NOT a good month west of the Cascades. Normal is lots of low clouds and hit and miss sunshine.

But as they say it is darkest before the dawn....and tomorrow will not be pleasant. A fairly strong upper level trough is now approaching (see figure) and it is associated

with considerable clouds and showers (see satellite picture). Tomorrow (Thursday) will not be nice. Lower 60sF.

A second weak trough comes through early Friday, leaving that day with scattered showers and a few sun breaks. Perhaps mid-60s

Saturday really should be decent, with little or no precipitation, partly cloudy skies and considerable sun and temperatures in the mid to upper 60s.

On Sunday, July 4th, the air will still be on the cool side and there will be lots of onshore flow; there could be some light, scattered precipitation, strengthened by a weak disturbance moving to our north early in the day. No guarantees. But no major storm.

But then the impossible will occur. Ridging in the eastern Pacific will build.

The pesky west coast trough will be no more and temperatures will warm rapidly on Monday and Tuesday.

Sun will return and temperatures will reach the seventies from Tuesday onward. Here is the upper level flow for Tuesday afternoon...a magnificent ridge.

Even lower to mid- 80s away from the water by mid-week. We are talking a significant heat wave and it will seem more so with all the cool weather we have been through.

Time to purchase a fan....

Finally, if any of you are interested, I will be one of the instructors this summer (August 5-8) at the North Cascade Institute's Northwest Naturalists Weekend: Weather, Wildfire and Biodiversity. I will provide a series of talks on NW weather and the other instructors will be talking about effects of wildfires and about lowland forests. Plus, hikes and canoe trips and good organic food in a beautiful location. For more information go to:


June 28, 2010

The Unending Trough

The weather west of the Cascade crest has gone downhill again and the we will stay in this June funk for the next several days.

The reason: the amazingly persistent trough over the eastern Pacific. But before I get into that, above is an interesting graph, which shows the water usage in Seattle for this year, 2009, and for averages over 1985-1991 and 1999-2008 (courtesy of the nice web pages of Seattle Public Utilities).

The water usage this year is really down compared to either 2009 (a warm, dry year) or normal. It looks like few of us are irrigating our gardens, with usage just above winter levels. Another interesting fact is how much less water we use now compared to the 80s, even though population is up. Clearly, water-conserving toilets and shower heads are making a major difference, and perhaps some individuals are making better landscaping decisions (drought-tolerant plants, drip irrigation, etc). With low water usage and a cool wet late spring, Seattle reservoir levels are above normal!

Now about that trough. Below are the upper level (500 mb) weather maps for last night and for the next few days. A low or trough dominates the eastern Pacific off our coast, and that brings clouds and some light rain showers this time of the year. Highs in the mid to perhaps upper 60s for a while.

The current forecast for July 4th? You don't want to know and I don't want to tell you. And there is plenty of time for the forecast to change. Just have indoor options for your big holiday barbecue!

June 25, 2010

Low Clouds over the Pacific

Perhaps the most important characteristic of June weather over the west side of the Northwest is the persistent low-level clouds--the cause of the annual June gloom or Junuary, as some wits like to call it.

There is a reason for the low clouds: -the NE Pacific is full of them this time of the year. Look at the visible satellite picture above (from Friday at 12:30 PM PDT). Most of the Pacific is covered in clouds. In fact, more of the Pacific has cloud cover now than during the middle of the winter! Nearly all of these clouds are stratus and stratocumulus, associated with some drizzle at best.

Even coastal California gets hit by this stuff--in fact it is worse for them than for us. Never plan a summer vacation in Monterrey if you want lots of sun.

Why so many clouds? Ironically, it has to do with high pressure. During the spring and early summer the east Pacific anticyclone (high pressure area) strengthens and moves northward and the Aleutian low attenuates. Below is the sea level pressure for yesterday at 5 PM....you can get a feel for the situation. High pressure is associated with weaker winds and sinking air.

Sinking is strongest aloft and weakens towards the surface (the air can't move through the surface). Sinking causes warming, so there is more warming aloft...this produces a stable situation with little mixing (inversion or near inversion conditions). Air near the surface thus gets moister and moisture without the mixing down of dry air aloft. Another factor is warm air moving off Asia and Alaska....as the air cools down over the warm it eventually can cool to saturation.

The result of both mechanisms: lots of low marine clouds. With higher pressure offshore (associated with the high) and lower pressure inland, the low clouds are pushed into the western lowlands. Generally you can escape them by traveling east of the Cascades, since they are quite shallow.

High pressure and cooler air on the western side and lower pressure east of the Cascades produce a bounty for some of us--strong winds and lots of wind energy downstream of gaps in the Cascades, like downstream of the Columbia Gorge or in the Ellensburg region (I have a section in my book on this).

Anyway, knowing why we have the low clouds won't get rid of them, but perhaps understanding their cause and possible benefits will make them easier to tolerate.

June 23, 2010

Finally! The 75F Ceiling is Broken

Today, temperature at Seattle Tacoma Airport has reached the the magic number--75F-- in fact later this afternoon temperature climbed to 77F. This is the latest into the summer season that Sea Tac has reached 75F for the first time. As apparent in the high resolution visible satellite image below--a clear zone existed today over western Oregon and Washington. Offshore extensive low-level cloudiness was in place, while eastern Washington was generally cloud with some convective showers over the northern portions.

Significant pressure changes have occurred during the past several hours, with the onshore pressure gradient reversing: pressure is now higher on the coast than inland, and some cooler ocean air will move in. Tomorrow will not only be cooler, but there will be considerable clouds and some light showers over the region.

I have gotten a large number of comments suggesting that the Iceland volcano has been the cause for our cool weather. Let me be absolutely clear on this...there is no reason to think this is true. None. The continuing eruption is NOT putting large amounts of sulfuric acid aerosol into the stratosphere---which is the only way that volcanic eruptions can have climatic impacts. Remember--Mt. St. Helens had virtually no climatic signal for the same reason.

June 20, 2010

Unusual Murk Strikes the NW

Even for me, a lover of rain and clouds, this is going too far.

Today was an amazingly murky day for much of the region, in addition to tying the record low-high at Seattle Tacoma Airport (55F). 55F is the typical high for mid April. You have heard of all the notable records for monthly precipitation and daily temperatures--I won't bore (or depress) you with more (and there are lots more!).

But here is something interesting. Today, June 20st, one day short of the day when the sun's ray should be the strongest over the northern hemisphere, was one of the most sunless days in months...many months.

Want the proof? Here is the solar radiation received at the top of the UW Atmospheric Sciences building since March (click on image to improve quality):

Today got up to around 50 W per meter squared, which is less than ANY day in the plot (which starts on 29 March). In fact, looking at a longer period, this is the darkest day (in terms of maximum solar radiation) since early February (see figure below)

Here is more information from Mark Albright, past Washington State Climatologist:

A scan of the last 15 years of rooftop June solar radiation data shows today (20 June 2010), just one day short of the summer solstice, to be the darkest June day over at least the past 15 years on campus. We received only 2.65 MJ/m2 of solar radiation today under very dark overcast gray skies. You have to go all the way back to 10 Feb 2010, with 2.40 MJ/m2 to find a day with less solar radiation than 20 June 2010! For comparison, the darkest day of the 2009-2010 winter was 11 Jan with 0.73 MJ/m2 of solar radiation.

Considering all the comments I am getting, people are starting to get depressed. Seasonal Affective Disorder in JUNE? I don't even want to ask about the sales of sunglasses and sunscreen. But at least we won't have to worry about rattlesnakes.

Finally, if any of you are interested, I will be one of the instructors this summer (August 5-8) at the North Cascade Institute's Northwest Naturalists Weekend: Weather, Wildfire and Biodiversity. I will provide a series of talks on NW weather and the other instructors will be talking about effects of wildfires and about lowland forests. Plus, hikes and canoe trips and good organic food in a beautiful location. For more information go to:


June 19, 2010

The Great Weather Divide

Today, some of the media are forecasting general showers over western Washington, but the reality will be very different between north and south. A tight upper level low is moving SE into Oregon (see graphic above) and a band of clouds and precipitation are wrapping around it (see image).

Try this animation of the visible satellite imagery:

The current radar picture shows that showers are limited to the south Sound area...so north of Seattle it might be completely dry. This kind of pattern brings precipitation into eastern Washington and of course the Cascades. In fact, with easterly flow approaching the Cascades, normally dry locations could get hit by heavy showers. The air will be somewhat unstable after the surface heats, so thunderstorms are possible over eastern WA and over the mountains. As the low moves SE the showers should follow.

If you dig down on the Seattle National Weather Service web site you can see their graphical forecasts (http://www.weather.gov/forecasts/wfo/sectors/sew.php)...here is their prediction today for 12-h precipitation ending 5 PM--the probability of rain varies from 83% in Olympia to 32% in Bellingham.

So advice for today....want dry condition...go north.

June 17, 2010

Don't Forget Portland...and the weekend

Snow at Timberline Lodge on Mt Hood on Wednesday

I talk a lot about Seattle wather in this blog (for obvious reasons), but as bad as it has been in western Washington, Portland and vicinity have been worse. For example, Portland has broken its ALL TIME MONTHLY RECORD precipitation for June, HALFWAY through it. Impressive. There has been a persistent trough over the WA and as a result Portland has often got the brunt of incoming systems.

Here are the temperature and precipitation records this month for Portland. Few days have risen to the normal highs, and the last few days have been extraordinary cool with highs not even reaching 60F. Some days have experienced all time record low highs. The soggy conditions reached a pinnacle on the 6th when Portland had 1.48 inches in a day.

There is one major silver lining in this heavy-duty cloudiness....the waterfalls in the Columbia Gorge are running very high. I love waterfalls and headed down there this week and was not disappointed. Big flows, huge sprays, and warming up near the big fire at Skamania Lodge in Stevenson makes the cold go away. And all the while sun was always close by...just head east to Hood River or beyond and sun and relative warmth beckons.

Or if you prefer fresh snow...no problem! Head for Mount Hood, where several inches fell at Timberline Lodge (see top picture).

We are now in a short improving trend and tomorrow should be partly cloudy and temps in the 60s. But I am afraid that things will go downhill on Saturday with a new upper low over us (see graphic), bring temps in the 50s and some precipitation.

June 14, 2010

The Cool Returns

The cool weather and the lack of warm days is killing honey bees in our area.

After a decent weekend, things are going downhill again.

First, as indicated by the chart below, we failed to reach 75F this weekend and thus we are completely smashing the 75F record...we are now the latest of all years in getting to 75F (old record was June 9). And it is going to be a while before we do so.
Today I was talking to a bee-keeping friend of mine who lives on Bainbridge Island. This weekend he went outside to check his hives and found a thousand bees dead on the ground in front of them. Why? He believes they starved to death because of the cool weather. Honey bees like the temperature to be 57F for them to fly around actively and this year such periods were rare. Now he is feeding them sugar water to keep them alive. That does not make quality honey.

Tomorrow a strong cold low will move over the region...so cold the National Weather Service put out a special statement about snow above 5000 ft. Here is the upper level (500 mb) map with shading indicating temperature. I would be thinking about snow in Seattle if it were December and I saw this pattern.

The bees are not going to be happy campers. Our temperatures will be 5-10F below normal and there is a good chance of light showers over the region tomorrow. And Wednesday won't be much better. But drying and warming is expected this weekend.

Finally, if any of you are interested, I will be one of the instructors this summer (August 5-8) at the North Cascade Institute's Northwest Naturalists Weekend: Weather, Wildfire and Biodiversity. I will provide a series of talks on NW weather and the other instructors will be talking about effects of wildfires and about lowland forests. Plus, hikes and canoe trips and good organic food in a beautiful location. For more information go to:


June 12, 2010

Finally Summer!

Today's visible image says it all--clear skies except for some regional low clouds that are rapidly burning off. Here is the latest forecast of max temps today from probcast:
mid-seventies over central Puget Sound and even warmer (80s!) east of the Cascades and in the Willamette Valley. Finally, a summer-like day that will get those strawberries and raspberries going and give our tomatoes a needed boost.

Tomorrow will not be as nice...but it may be good enough for many activities. A weak front will be moving through the region Sunday AM, bring clouds and a few sprinkles on the coast and NW WA. The afternoon should be dry over the lowlands with partly cloudy conditions. Temps should drop about 10F to the mid-sixties on Sunday.

In the wake of the front marine air will move it...an onshore push...and Monday will be relatively cool and cloudy over the western side of the state, with temps only getting into the lower 60s. Typical June weather. Nothing exciting next week...just June weather with mixed clouds, high in the 60s, and relatively dry. No big storms.

June 09, 2010

Remarkable Convergence Zone Rain

We have had some very strong showers over the region during the past six hours and particularly in a convergence zone over the north Sound and eastern Strait of Juan de Fuca (check out recent radar above). It is really pouring in some locations.

Take a look at the last 6-h rainfall from the Seattle rainwatch web site (www.atmos.washington.edu/SPU). Some locations on the Kitsap and near Marysville have gotten TWO to THREE inches over the last six hours. I would not be surprised if there was some street or urban flooding in these places (this is what Rainwatch, funded by Seattle's Public Utilities, was designed to help show). An other heavy rain band struck Tacoma and the south Sound. Not as much action in between due to rainshadowing in the lee of the Olympics.
Now there are some people who make fun of weathermen (none of you, of course). But to show you how far we have come...below is forecast made this morning for three hour rainfall ending 11 PM. Compare that against the radar...not perfect, but it got the general idea of that SW-NE band over the N Sound.

And, as I noted yesterday, Saturday is still on track to be warm and sunny. Not as good on Sunday.

June 08, 2010

Weekend Heat Wave...but first

It is really looking like we will FINALLY see some real warmth this weekend...but first there will be clouds and rain.
As an amusing aside, it looks certain that we will break a major record tomorrow...the latest in the season that the Sea-Tac maximum temperature has not hit 75F! The record is June 9...and there is virtually no chance we will get that high tomorrow. You will tell your grand kids about this some day. Maybe.

A front with some heavy showers is moving in now (Tuesday night) and more are expected Wednesday and Thursday. Friday is the transition day and then the unexpected will occur....ridging aloft and offshore flow leading to a major warming on Saturday.
Exhibit 1: Here is the 500 mb upper level chart for Friday at 4 PM. A very nice ridge is developing.
Exhibit 2: The same chart a day later...even better.What about the surface temperatures? Here is the latest model forecast for 5 PM on Saturday. SEVENTIES OVER THE LOWLANDS. And 80s in the Willamette Valley and portions of eastern Washington.

Get your barbecues ready! The ridge will hold through Sunday, with temperatures at least as warm. Unfortunately, it will cool down in next week a bit...

June 06, 2010

The First Day of Summer: When Will It Be?

The big question that is on everyone's mind:

When will summer really begin?

There is a stock answer that local meteorologists give for this query:
July 12th. And it is usually pretty close to the truth.

First, lets get real. June is often a bad month in Seattle. June gloom. Lots of low clouds. ( The good thing is you can usually get out of it by crossing into eastern Washington.) Memorial Day weekend has never been dependable. I can't count how many times the media has done the same story about the unusually cloudy spring.

There is NO reason to suspect our cold weather is due to the Iceland volcano, the oil spill in the Gulf, or El Nino/La Nino. It does not have any connection with global warming or sunspots.

The July 4th weekend is also a crap shoot. Sometimes very nice, often not. But then something magical happens...it is like someone throws a switch...and by mid July we have the best weather in the U.S. --temps in the 70s, low humidity, sunny skies, not too many bugs--heaven. In fact in July we get less rain than Tucson or Phoenix.

The change in July is really quite extraordinary...one of the most rapid climatological dry-outs in the U.S. Below is a graph of the daily probability of getting a trace of rain or more for.. July is just amazing. During the first few days of the month there is roughly a 30% chance of rain in any day. By the last week..roughly 8%.

Want to get married outdoors or hold a party?...end of July or beginning of August is the driest period of the year. No doubt that is why Seafair is scheduled then.

What about the next week? The next few days will have rain on and off. But then, next weekend, the models are going for a major warm up...we will see.

June 04, 2010

Funnel Cloud and Sunday's Weather

Here is a picture sent to me by Michael Baseflug (forwarded to him by a co-worker) of a funnel cloud observed around 5:10 PM today (Friday). And another one provided by Brad Colman of the National Weather Service:

Looking at the radar this funnel was embedded in some heavy precipitation associated with the current Puget Sound convergence zone. Puget Sound tornadoes are often associated with CZs (my book tells why).

The convergence zone will weaken tomorrow and Saturday will be a fine day.

The models still have problem with Sunday...we are just on the northern edge of the rainfall associated with a system south of us. One thing is clear, the further north you go the drier it will be....Bellingham will be better than Portland!

June 03, 2010

No windstorm and a decent Saturday

Weather Gods Like Coastal Weather Radars

Earlier this week it looked like a strong low center and attendant windstorm would strike our region. No longer. The weather gods have been satiated. It is quite possible they are pleased with the National Weather Service's decision to bring a weather radar to our coast a year earlier. A sure sign of respect.

In some situations, the models find a solution 5-7 days out and stick with it, in others the weather forecasts don't settle down until 1-2 days out. Tomorrow is an example of the latter situation.

Each forecast run for the past few days tended to weaken the low and bring it in further south. Below is today's forecast: a modest low will cross Oregon and we should see little wind from it. Precipitation associated with this event will move in this evening and extend into tomorrow morning. The rain will be through mid-day for most of the region, with the exception of a fairly strong Puget Sound Convergence Zone in the afternoon (see graphic).
Saturday will be drier and warmer (60s) and then a weak system will dampen Sunday
But next week there may be a major shift towards summer warmth and dry conditions...stay tuned.

June 02, 2010

Major Radar Announcement

Today, Senator Maria Cantwell announced that the new coastal radar would be installed one year earlier than initially planned--thus, it should be in place by September 2011. (see her press release--http://cantwell.senate.gov/news/record.cfm?id=325432)

The National Weather Service has found an available WSR-88D radar unit (these are the radars that currently comprise the current national radar network) at Keesler Air Force Base and will update it with dual-polarization hardware. This unit will then be moved to Grays Harbor county and placed on one of the three potential sites identified in the recently released siting report. The top location is Langley Hill, located northwest of Hoquiam and about 3.5 miles east of Copalis Beach.

When I learned about this proposed plan a few months ago, I was a little nervous about accepting a used unit, when Senator Cantwell had secured enough funds for a new one, but I am now convinced that this is the best approach. First, the WSR-88Ds are proven units for which the NWS has deep experience. They know how to repair them and two local offices (Seattle and Portland) would have technicians that would be available. Second, the units have been updated over the years and the dual-polarization option (which allows identification of precipitation type and better estimation of rainfall intensity) would be installed from the beginning. Third, I talked to radar experts around the country (including at the National Center for Atmospheric Research), who all agreed that this approach would be best and that the unit would be state of the art.

Having the radar in a year early is a great benefit. Many are worried about flooding and the stress on the Howard Hanson Dam. Last year was an El Nino year--which typically doesn't bring major flooding. But next year will be different, since the El Nino is rapidly fading and heading towards a neutral or La Nina year. It would have been nice to have had the radar this coming winter, but certainly the followed year will be a non-El Nino year and thus threatening.

The National Weather Service has also compromised on an essential issue...they are now willing to run the radar with a zero degree elevation angle. Sounds complicated, but this means that the lowest radar scan will be horizontal, not at the NWS's typical .5 degree angle). This zero degree angle will allow MUCH better coverage offshore and at low levels.

This new radar will revolutionize weather prediction in our area and I would like to again acknowledge the major role played by Senator Cantwell. She not only appreciated the crucial need for this radar but secured the funding as well.

This is one piece of infrastructure that will pay for itself many times over and save lives. No longer will mariners venture offshore with a poor understanding of coastal conditions. No longer will coastal residents be denied what those of us in the Puget Sound area enjoy--detailed knowledge of where it is raining. No longer will forecasters be surprised when our computer models fail. And no longer will there be uncertainty regarding precipitation on the Olympics and the SW coastal mountains. This will be a major public benefit, and I suspect you will see it on your local weather broadcast nearly every night in the winter!

June 01, 2010

Weather Picture of the Day

Take a look at this satellite picture: a line of clouds and rain stretching THOUSANDS of miles are headed for our area. This looks like November!

The rain is now moving into western Washington and the latest forecast is for substantial rain, particularly on the western side of our terrain (see 24-h precip map ending at 5 PM Wednesday).

A windstorm is still on tap for Friday. More on that later.

Even eastern Washington will be wet and some locations on the western slopes may receive 2-4 inches. One good thing about these conditions: plenty of water to fill our reservoirs for summer use. Here is the latest snowpack conditions in the area...the Olympics are at roughly 250% of normal, and much of the rest of the region near 100%. Demand for water is down. There will be no water problems this summer for irrigation, drinking, or for fish.

Winter-Like System in May

Tomorrow will not feel like late May, with a winter-like Pacific weather system making landfall, bringing lots of rain, wind, and cool tempe...