Thursday, April 29, 2010

Latest Oil Pics: Oil Spill Reaches the Coast and Bad Meteorology


The latest MODIS satellite picture shows the oil making landfall on the far SE Louisiana coast. Not good. I made a blow-up below so you can see the detail. On the meteorological side, you can see nice rows of cloud streets over land in the first picture.


The weather is not cooperating I am afraid. Below are the surface winds predicted for tonight and tomorrow night . Moderate southeasterly winds blowing the oil directly to the coast.
10 PM Thursday


10 PM Friday

And here are some recent surface observations over the Gulf of Mexico...SE winds are clearly evident.
This is all very serious. The persistent southeasterly winds are pushing water up against the coast, where the general water levels will be several feet above normal. On top of that there is substantial wave action--roughly 5-7 feet. The only good aspect of all this...and good is a bad word, is that it is moving the spill away from Florida. There is a loop current in the Gulf and if the spill went south, the oil could move along the western side of Florida, into the Keys and the Everglades, and around the peninsula towards Miami. This is the last place in the U.S. you want a major spill.

Wednesday, April 28, 2010

Gulf Oil Slick Image and Local Weather


The NASA AQUA satellite got a a great view of the oil slick off Louisiana a few days ago (April 25)-- you can see it above. The oil is the white-looking stuff, reminiscent of an ink blob in some water. The MODIS sensor has amazing resolution (250 meters)--compare that to visible satellite imagery, which tops at at 1-km resolution. You can also see the particle-laden water exiting the Mississippi delta.
The next picture is for yesterday, April 27th, is a close up and in this case the oil has a darker color.

Finally, the image today is not as helpful, since there were lots of clouds overhead.

Talking about today, here in the NW we had another classic spring day with cool air aloft and destabilization of the atmosphere during the day as the surface heated up.
In addition, we had a weak convergence zone situation, with winds shifting from north to south. A wonderful view of the action is available from Dale Irelands HD webcam:
http://www.drdale.com/lapse/lapse100428.mov

Watch as the clouds are relatively layered (we call that stratiform in the biz) during the morning, but switch to bubbling cumulus during the morning and afternoon. You can see multiple wind shifts.

Finally, there was some talk about the warm temps and strong winds on Monday. In some places like Arlington the temps rose into the low 70s as strong to moderate southeasterly and easterly winds descended the Cascades, warming by compression as it did so. Look at the weather obs at the UW for Monday (click on the image to expand. SE winds gusting to roughly 25-30 kts accompanied the jump in air temp to the upper 60s. At the same time, the relative humidity plummeted to around 30%--classic drying with downslope flow.

Monday, April 26, 2010

Rainshadow Land

Living here in the Northwest we often think about how much it rains, but to truly understand our weather, you have to appreciate our rainshadows. We have world-class rain, but we also have world-class rainshadows. Take a look at the radar image above (from the Camano Island radar). Precipitation (indicated by the colors) all around the place, but there is a rain-free zone downstream of the Olympics...stretching from Sequim to the San Juans. Or take a look at the precipitation over the last six hours from the SPU Rainwatch System (see graphic). You can see that the dry-zone ground zero is just offshore from Sequim. That is why so many people retire there and cacti are native species. As air approaches a barrier it rises, producing precipitation, but on the opposite side there is sinking, drying, and rain shadow creation. You can look at the rainshadow above and immediately know the wind direction near the Olympics--from the south-southwest. To prove this, here is the latest radiosonde sounding at Forks, on the Olympic Peninsula. The general crest level of the Olympics is roughly 5000 ft--approximately 850 mb, with higher terrain above that to roughly 8000 ft. So look at 850-800 on the sounding chart. If you can read the wind barbs, you will see the southerly flow.

An important thing to know about rainshadows is that they can move since their position is controlled by large scale wind direction interaction with terrain barriers. So Sequim being dry is not religion. It is just the wind here in the winter is typically from the south to southwest. If the large scale wind shifts direction, so will the rainshadow. So if the wind switches to westerly or northwesterly, Sequim is no longer effectively shadowed, but Seattle and central Puget Sound is! That will give the retirees and golfers in Sequim something to think about! Such Puget Sound rainshadowing is really quite frequent and helps explain why Seattle is really quite dry (only 37 inches a year), receiving far less than the east coast of the U.S., and WAY less than the Washington Coast. That is why vampires live in Forks but keep away from the Puget Sound lowlands.

But there is one ironic complication to our rainshadow under westerly flow....something that literally rains on our parade: the Puget Sound convergence zone, which produces a band of rain IN THE MIDDLE OF A PROFOUND RAINSHADOW. That is why north and south of a convergence zone it can be profoundly clear.

Finally, not only can rainshadows move, but we have lots of them due to our complex mountains. Big rainshadows in the lee of the mountains of Vancouver Island, the Cascades, the Blue Mountains. Smaller ones in the lee of Mt. Rainier and the other volcanoes. Even rainshadows int the lee of Queen Anne Hill and Tiger Mountains. Yes, this is really rainshadow land here.

Friday, April 23, 2010

Why are our fronts different?


Friday Afternoon Visible Satellite Image: Front Approaching

Update: Here is Saturday Morning's Visible Photo--you can see all the showers offshore

It is now 7:30 PM on Friday and a modest Pacific front is moving through western Washington . The above (top one) high-resolution satellite image at 5 PM shows the story. At that time most of eastern Washington was clear and wave clouds induced by the mountains was found over and immediately to the lee of the Cascades (they are those periodic lines of clouds in the image). The front will be through by midnight and the continuous showers will end. If we were living over the eastern two-thirds of the U.S. it would then be all over. Fronts bring rain. After the fronts move past the skies clear and the precipitation is over. Here is an example of the lack of clouds and precipitation after a midwest front.



But that is NOT what is typical here. After the front passes in the Northwest the weather show is just beginning, because we typically see postfrontal convective showers in the 24-h after a front moves through during winter and spring. You know what I mean--the typical showers and sunbreaks. The media tends to call this wacky and strange...but those that make such remarks don't understand our weather.

Here is an interesting fact: in the winter much of our mountain snow does NOT come from frontal precipitation, but from the showers after the fronts in the cold, unstable air that follows. Tomorrow will be no exception. A field of postfrontal convective showers are out there waiting to come into our area, and the forecast is for showery precipitation on Saturday. Don't believe me? Take a look at the larger view satellite image at 5 PM today (Friday). You see the front? Then you see a narrow zone of clearing (this is due to sinking motion immediately behind the surface front) and then a thousand kilometers of more of convective showers, which look like a field of cotton balls surround by dark (clear) areas. Our number is on those clouds. In the business we call them "open cellular convection" because generally there are more clear areas than precipitating areas.

Why do we get these showers AFTER the front? Because there is plenty of moisture (not surprising) and the atmosphere is relatively unstable there. The ocean surface is "relatively" warm--roughly 50F year-round off our coast, and the air behind the front (cold or occluded front) is even colder, coming off of Alaska or Siberia. Cold air over warmer water is an unstable situation, with temperature decreasing rapidly with height. Cold air is dense and wants to sink, warm air is less dense and wants to rise. Put them cold air over warm air and they want to switch places. Or think about your hot cereal, which convects when you create a large change of temperature in the vertical when you turn on the burner. (My book has much more on this if you are interested in learning more).

So why doesn't this happen over the eastern U.S.? First, there is less moisture. But more importantly, the land surface is cool or cold in the winter, so you have cold air over cold land. No good.

But wait! We have more special weather here! The coastal winds often switch to the west here after frontal passage, particularly during the spring. Such a wind direction leads to the formation of Puget Sound convergence zone, a zone of clouds and precipitation over Puget Sound...generally from Everett to north Seattle, with clear zones to the north and south. And guess what, the computer models indicate a good chance of this happening tomorrow (see forecast of the 3-hr precip ending 8 PM on Saturday). And there will be plenty of showers in the mountains, including snow showers at higher elevations (see graphic). Typical spring in Seattle!

Wednesday, April 21, 2010

Harry Wappler (1936-2010)


It is with great sadness that I note the passing of Harry Wappler, the dean of Northwest weathercasters for over a quarter century. As many of you remember, Harry was the lead meteorologist on KIRO-TV during the 70s, 80s, and 90s. He was one of the most genuine, kind, warm-hearted individuals I have ever met, and a passionate, enthusiastic member of the local weather community.

I got to know him quite well when I returned to UW to join the atmospheric sciences faculty. Although Harry did not have a degree in atmospheric sciences (he had a B.A. in speech from Northwestern and a graduate degree from Yale Divinity School!), he was an avid student of Northwest weather and I learned a great deal from him about the convergence zone and other local weather features. Harry was the TV weathercaster that I would watch. He was a mainstay of the local weather community and secured substantial funding from KIRO to invite a distinguished meteorologist to town each year. The local chapter of the American Meteorological Society would meet at KIRO once a year and Harry always supplied a nice carrot cake. I still remember that carrot cake fondly.

To give you an idea of Harry's involvement with the community, on November 13, 1981 a major storm was offshore. The numerical prediction technology at that time was fairly primitive and without much skill for such events. Harry had a new-fangled invention that the National Weather Service did not possess: a device that could animate satellite imagery, something we take for granted today. An intense storm was obvious in the animation and headed our way. Harry made a tape of the satellite loop and rushed it to the National Weather Service folks who put out a timely and accurate warning. He could have kept it to himself and smoked the other stations, but that was not Harry's way.

The only time there was a slight bit of tension between me and Harry was when I had my 101 students write down the forecasts of all the local TV stations and scored them compared to the Weather Service. None of the stations were statistically better than the Weather Service, but another station had beaten KIRO. He called my chairman asking about this investigation (probably pushed on by his management). But next time we met, he smiled, told me it was water under the bridge, and we remained very friendly for the rest of his career.

A few times I went out with him in public. Everyone knew him and treated him as a member of the family. They would come up to him and tell their weather tales, and he would listen so intently and with obvious warmth, without ego or pretense. They went away feeling special.

I wish I had talked to him more often after he retired, but I have very fond memories of him, as as I suspect many of you do as well. Harry was a remarkable individual and we are all lucky to have shared some time with him.

Tuesday, April 20, 2010

Its 2040!


Congratulations!

For those of you living in western Washington, you have experienced a typical winter of roughly 2040.

Now how can I say this?

Looking at the average temperatures from November through March at Seattle-Tacoma Airport, the last winter was 1.8F above normal, including the remarkable warmth of January. Examining the temperature predictions using high-resolution models embedded in global climate models, driven by an aggressive increase of greenhouse gases, one find that this corresponds to the expected changes around 2040. (For the hard core climate types, this is based on the MM5 runs forced by the ECHAM-5 GCM, check out:
http://www.atmos.washington.edu/~salathe/reg_climate_mod/ECHAM-MM5/seadiffs)

The April 1 snowpack this year was roughly 70% of normal in the Cascades and this corresponds to the amounts in the models for roughly the same time--2040.

Time travel without traveling!

Now I am not saying this to downplay global warming, but to just add some perspective. Thirty years from now it will be warmer and the snowpack will be less, but here in the Northwest no panic is required. Even our current infrastructure can handle water supplies for such a situation.

This week I had a very interesting meeting with managers from Seattle Public Utilities, who are actively thinking about the implications of global warming on Seattle's water supply. It appears that with some changes in management of the reservoirs (storing more water in the spring and letting the level come down a little farther in the fall) and some modest improvements to the system, Seattle will easily weather climate changes well into mid-century.

In our discussions something came up that should have been obvious to me: the amount of rainfall during the winter and the snowpack at the beginning of summer are both very important, but so is something else--when the winter rains begin in the fall. How will this change under global warming? This is something I am going to investigate in the simulations we are running right now. Several simulations I know of suggest somewhat heavier fall precipitation, which if true, could help mitigate the water situation further.

Another factor this is helping immensely is that even with all the local population growth, water demand has stagnated or even decreased. An amazing accomplishment. Give credit to better plumbing--those water conserving toilets and shower heads--coupled with reduced usage of water during the summer.

Saturday, April 17, 2010

Eyjafjallajökull (Iceland Volcano): No Climate Impacts. Local Weather Update


A few media outlets are starting to talk about a climatic impact of the Iceland volcano, but they shouldn't be. First, this is really a pretty modest event. But even more important, it is NOT ejecting large amounts of sulfur dioxide into the stratosphere, which is the main way volcanoes alter climate. As noted in my last blog, sulfur dioxide combines with water vapor to create small sulphuric acid particles that scatter some of the sun's rays back into space. The result is global cooling--up to a degree or two C for the big eruptions.

We have satellites that can measure sulfur dioxide (SO2) from space, one of them being the NASA OMI instrument on its AQUA satellite. Here is a recent image showing total SO2 in a vertical column--no real evidence of volcano SO2 in this and previous images.

In contrast, here is another image from an Alaskan (Aleutian chain) volcano

that had much more prodigious SO2 production. Lots of red...that means plenty of SO2.


Another point is the latitude of the eruption: being far north limits that ability of the SO2 to spread into the equatorial zone and the southern hemisphere.

I suspect the authorities in Europe are being conservative, perhaps too conservative, in canceling flights and closing airports. With some effort, the altitudes and locations of the dust cloud could be accurately delineated and flights could simply be vectored away from the areas of higher concentrations. Furthermore, a lot of the dust coverage over Europe is very thin--is that REALLY a problem for a jet engine? This is really a minor eruption and it seems unlikely that it could spread a sufficiently dense layer of dust over the volume of air in which air traffic restrictions are taking place.

They are being careful, and lets face it, aviation authorities over Europe don't have much experience with such dust events. Long range weather predictions indicate the later in the week the flow over most of Europe will turn more southwesterly, so even if the volcano is going wild most European airports should be functional.

Perhaps some old prop planes (driven by gas engines and not turbines) can be taken out of storage...they do much better with volcanic dust, since the blades of jet turbines are the real vulnerability in volcanic dust clouds.

Want to see an example of an old prop plane flying close to a major eruption? A few hours after the initial Mt. St. Helens eruption, Professor Peter Hobbs and Research Scientist Larry Radke took a UW research aircraft (prop plane) up to and into portions of the volcanic cloud...and lived to tell the tale. You can watch some video of their daring flight: http://pluie.atmos.washington.edu/movies/msh_sm.wmv

Finally, for those of us in the Northwest, tomorrow should be a splendid day. The front is moving through now and the showers are lessening. We should see sun and temperatures climbing into the 60s for the lowlands. Some people has asked whether some of the dust on their cars is volcanic dust. The answer is no. Most of the gunk is pollen from trees and plants. I had to wash my car yesterday...it was covered with the stuff!

Thursday, April 15, 2010

Iceland's Volcanic Eruption: Will it influence weather and climate?

Dust Plume from Mount Eyjafjallokull seen by a NASA MODIS satellite

There have been a number of inquiries about the impact of the eruption of Iceland's Mount Eyjafjallokull volcano (how do you pronounce it?&%). I have a lot of interest in the weather/climate effects of volcanoes and have written several papers on it, including a paper on the local weather effects of Mount St. Helens.

The volcano has sent a plume of ash, dust, and gases to altitudes of 40-50 thousand feet, high enough to be spread rapidly east by the jet stream winds aloft. The immediate danger is to aviation: the dust can clog jet engines, with the silica component melting and hardening on jet turbine parts.
But what about weather and climate?

This was not a particularly explosive event--not the equivalent of Mt. Pinatubo or St. Helens, to name only a few. The big question is how long the volcano will continue to erupt--the last major event of this volcano in the 19th century lasted a few years, but at a relatively low level. I have included some satellite images of the dust plume. In the picture at the top of the blog you can clearly see the dust (brown color) extending southeastward from Iceland. Another image is found below.


Using satellite observations and knowing the winds aloft, we can track and predict where volcanic dust clouds will move. Here is the recent distribution at several times of the current event.


The weather effects will be modest and short-lived. The large dust particles fall out or are washed out of the atmosphere, so if the eruption stops the dust will be removed in a matter of days. Weather effects include a loss of solar radiation and thus cooling during the day, while at night the dust plume can act to reduce the loss of infrared radiation to space and thus warm. Significant weather effects will be limited to Iceland and immediately downstream for a hundred miles or so. St. Helen's plume caused 10-15F cooling during the next day over eastern Washington. 48h later, the effects were hard to notice.

But what about climate changes? Dust and ash fall out quickly and have no climate impacts. But the sulfur dioxide gas can be lofted high into the stratosphere and combine with water to form sulphuric acid and sulfate particles that can produce a haze that stays in the stratosphere for several years (typically 1-3 years). Such hazes scatter some of the sun's rays back to space and produce cooling. In fact, several studies have shown a major eruption (in terms of injecting sulfur dioxide into the stratosphere) can cool the planet down by several degrees centigrade. Perhaps the most famous example is the "Year Without a Summer" of 1816, following the great eruption of Mt. Tambora in 1815. Killer frosts hit the NE U.S. and Europe in June 1816, crops failed, and amazing sunsets reigned.

So the big question is how sulfur rich is the Iceland eruption, how much is getting into the stratosphere, and how long will the eruption last. A major eruption could tame global warming for a few years and in fact some geoengineering advocates think we should deliberately spread some kind of dust particle in the stratosphere to mimic an endless volcanic eruption. But this has a downside....such particles contribute to the destruction of the ozone layer. From initial reports, the sulfur content of the Iceland eruption is relatively low, so that would lessen its climate impacts. Another factor is the latitude of the eruption. Low-latitude eruptions have the most climatic impact since sulfur dioxide gas and resulting aerosols can spread northward into both hemisphere in the stratosphere, while midlatitude and high latitude eruptions tend to stay over northern latitudes, thus influencing a far smaller portion of the globe. Iceland is obviously pretty far north.

And one more local factoid: Mt. St. Helens injected lots of dust and ash into the atmosphere, but was relatively sulfur poor--thus, it had virtually no climatic impact.

Tuesday, April 13, 2010

Summer Outlook


Quite a few of you have emailed me asking about the summer forecast. What does one expect in an El Nino year? Is there any useful guidance for planning that summer outing or party?

Let me begin by being honest: forecast skill for summer made this far out has only marginal skill. Now that won't stop me from telling you what the official and unofficial forecasts are, but please don't depend on them for anything critical.

And keep in mind that summer generally start around here a week or two after the July 4th weekend. The inside joke in the local weather community is that summer starts on July 12th, and this is often pretty close. It is true that we are in an El Nino pattern right now (warmer than normal water in the tropical Pacific), but it is only a moderate one and our forecasting tools suggest that it will weaken rapidly this summer. Besides, El Nino does not correlate that well with our summer weather.

The National Weather Service's Climate Prediction Center provided the following forecast for this summer (June, July, August) temperature and precipitation. To create the forecast, NWS forecasters use many tools: El Nino/La Nina, historical trends, an ensemble of long-range weather forecasts, and much more. You note that they are going for above-normal temperatures over the western U.S. (Canada is white because they don't forecast there!) and below normal precipitation over Oregon and Washington. Good tomato weather.

Just looking at the influence of El Nino one finds very little signal. Here are plots of temperature and precipitation anomalies (differences from climatology) for El Nino years. All white. Very little signal.

As noted earlier, long-range forecasts only have marginal skill. Want proof?

Here is the temperature forecast from the ensemble of computer forecasts for last summer's temperature made in early May. Reality was much warmer than normal over the NW, while the models missed it completely.Now there is always the Farmer's Almanac, found in better supermarkets everywhere. Here is their forecast for this summer:

Summer will be drier than normal, with below-normal temperatures, on average, in Washington and above-normal temperatures in California and Oregon. The hottest periods will occur in late June and mid-July.

Dr. Nick Bond of NOAA and UW JISAO studied the Farmer's Almanac's skill...it didn't have any.

Anyway, I wish I could give you better guidance for this summer, but I can't. Oh, I almost forgot. When is the absolutely best time to plan than special outdoor occasion? The driest period of the year? The last few days of July. I love having a "dry-sky" party on July 30th. Precipitation has only fallen on about 7% of the time on such days.

Sunday, April 11, 2010

TV Weathercasters and Global Warming And Current Weather

There were several comments regarding my blog on TV Weathercaster and Global Warming that suggested I didn't express myself clearly enough, so let me try here.

I am NOT saying that one MUST have a higher degree in atmospheric sciences or meteorology to understand the issue of global warming, although such backgrounds surely help. The climate system is quite complex and to really understand the issue takes a real dedication to mastering the basic physics and interactions. Anyone can gain such knowledge with a little effort, and I know many without technical degrees that have (including a number of amazing retirees that attend atmospheric sciences classes here at the UW). Reading a few web articles and watching Climategate coverage on TV just won't do it. We live in an era when too many people think they understand something based on superficial study and are unwilling to put in the hard work to master the subject. And this is isn't limited to climate.

Regarding TV folks, what I WAS saying is just because someone is a TV weathercaster does not mean they have the necessary knowledge in the climate arena, since a majority of them don't have a basic academic background in the material. And some of the denier TV weathercasters are making arguments that are simply in error technically.

There IS substantial uncertainty in the magnitude of global warming and the local implications of the changes. And yes, some scientists have overhyped things at time. But the essential science is very solid and mankind will substantially change the earth's environment if we follow the current route.

Another point that should be stressed is that there has been a fixation by the scientific and political communities on global warming, when that is only a small part of the overall problem of sustainability. Mankind needs to adapt so that we can live with our planet in the long haul...and we are not doing it. A big issue is overpopulation...there are simply too many people on this planet using too many resources. If the population was 1/4 of the current, we probably would not be worried as much about global warming. But it is funny how no one likes to talk about population issues.

Irrespective of global warming, we should be doing the right things anyway for many reasons. More recycling, more conservation of energy, more renewables, reduce population growth, protecting our soils, preventing the collapse of our fisheries, emitting less toxins into atmosphere and water, etc. This is not a liberal or conservative issue. It is about giving our species a future in the long term. Are we smart enough to do this?

Back to weather.

Take a look at plot of temperature and precipitation over the past four weeks (compared to normal highs and lows and usual daily precip). The past month has been wetter than normal and the last two weeks colder than normal. No day in the last two weeks has gotten warmer than normal. No surprise. And the result has been a major improvement in our snowpack and reservoir levels. And quite frankly this break in the El Nino warmth and dryness was not forecast ahead of time.

Today and tomorrow the main action goes to our south, as a low pressure center heads into California (see image). Bands of clouds are circling around to its north, producing the high clouds that we will see today. It should be dry today over Washington and relatively warm, with temps rising into the low 60s. There is easterly flow aloft that produces warming and drying on the western side of the Cascades.

Thursday, April 8, 2010

Cold and Snow

Just a brief note. After passage of a Pacific front last night, the freezing level has plummeted to approximately 1500 ft. Snow level is roughly 1000 ft below that. The winds in the lower atmosphere are from the northwest and the lowlands will be mainly rainshadowed from the incoming instability showers over the Pacific. The mountains on the other hand will AGAIN be hammered with snow...with 1-2 ft in many locations. I don't expect much snow action reaching sea level due to the marginal temps and lack of precipitation, with one exception--there could be a weak convergence zone today. In fact, as shown in the radar image, one has already started to form:You can also see the general scattered showers in this image and the rainshadowing outside of the convergence zone over the lowlands.

The snowpack, shown below, is rapidly rebounding. And since local water utilities, like SPU, have gone into water saving mode early, we are actually in pretty decent shape now. Skiing will be excellent this weekend. The strange thing for me is that yesterday I flew in from NY, where temperatures came close to 90F.

Wednesday, April 7, 2010

Monday's "Surprise Storm"


Weather prediction has come a long way, but sometimes forecasters miss a significant event and Monday's windstorm over the Oregon coast and the Willamette Valley was a good example. The satellite picture above shows a tight low center making landfall near the Oregon/Washington border. As shown in the list below, winds of 50-70 mph were observed at a number of locations along the Oregon coast (click on the graphic to get an enlarged clear image)And here is a plot at Newport, Oregon, where there was a peak gust of roughly 55 knots on Monday, April 5th.
The forecast from the National Weather Service distributed on Sunday was:
NORTHWEST OREGON AND SOUTHWEST WASHINGTON
NATIONAL WEATHER SERVICE PORTLAND OREGON
220 PM PDT SUN APR 4 2010
ORZ001-WAZ021-050545-
NORTH OREGON COAST-SOUTH WASHINGTON COAST-
INCLUDING THE CITIES OF...ASTORIA...CANNON BEACH...TILLAMOOK...
PACIFIC CITY...NORTH COVE...RAYMOND...LONG BEACH...NASELLE
220 PM PDT SUN APR 4 2010

.TONIGHT...SHOWERS LIKELY. A SLIGHT CHANCE OF THUNDERSTORMS AFTER MIDNIGHT. LOWS 35 TO 40. SOUTHEAST WIND 10 TO 20 MPH.
.MONDAY...SHOWERS LIKELY. A SLIGHT CHANCE OF THUNDERSTORMS IN THE MORNING. HIGHS AROUND 50. SOUTH WIND 10 TO 15 MPH.
.MONDAY NIGHT...SHOWERS LIKELY. BREEZY. LOWS 35 TO 40. SOUTHWEST
WIND 15 TO 25 MPH.
.TUESDAY...MOSTLY CLOUDY WITH A CHANCE OF SHOWERS. HIGHS 50 TO 55.
SOUTHWEST WIND 10 TO 15 MPH.
-------------------------------------------------------------------------------------------
CENTRAL OREGON COAST-
INCLUDING THE CITIES OF...LINCOLN CITY...NEWPORT...YACHATS...
FLORENCE
220 PM PDT SUN APR 4 2010

.TONIGHT...SHOWERS. A SLIGHT CHANCE OF THUNDERSTORMS OVERNIGHT.
LOWS 35 TO 40. SOUTH WIND 15 TO 20 MPH.
.MONDAY...SHOWERS. A SLIGHT CHANCE OF THUNDERSTORMS IN THE
MORNING. HIGHS NEAR 50. SOUTHWEST WIND 15 TO 20 MPH.
.MONDAY NIGHT...SHOWERS LIKELY. LOWS AROUND 40. SOUTHWEST WIND 15 TO 20 MPH.
.TUESDAY...MOSTLY CLOUDY WITH A CHANCE OF SHOWERS. HIGHS 50 TO 55.
SOUTHWEST WIND 10 TO 20 MPH.

The NWS was only going for 15-20 mph!

Clearly, the forecast models had some problems the day before--which is not surprising for a small scale low coming off the Pacific. Below is the wind and sea-level forecast valid 2 PM on Monday for a simulation started at 5 AM on Sunday. A weak 1003 mb low was evident as we brisk, but modest winds. Contrast that with the second graphic for a forecast started 24-h later--a 998 mb low and much stronger coastal winds.




This is not the first surprise storm associated with a small, intense low center to hit Oregon...another occurred during Feb 7, 2002---the South Valley Surprise Storm (check out: http://www.climate.washington.edu/stormking/ to find a description of that event).

Monday, April 5, 2010

TV Weathermen and Climate


A number of you asked about the NY Times story that reported on a George Mason University study that roughly a third of polled TV weathermen don't believe in man-caused global warming (http://www.nytimes.com/2010/03/30/science/earth/30warming.html). Specifically, 27% answered in the affirmative that "global warming was a scam." Only half thought that global warming was occurring. In contrast, nearly all Ph.D. and research meteorologists believe that global warming is occurring and will be highly significant. How can this be? I should note that this national poll is not representative of Seattle, where virtually all of our TV weathercaster contingent believe human-induced global warming is a serious issue.

A key question you should ask is this: what is the scientific background of TV weather folk? Do they have the education or experience that would allow them to provide an informed opinion of this or other science matters?

The truth is that most TV weather presenters or "weathercasters" don't have college degrees in atmospheric sciences or meteorology. My own rough estimate is that perhaps 1/4 have at least a B.S. in the subject. Very, very few have graduate degrees (M.S. or Ph.D.) in the field. The weekend weather folks generally have less real background than the weekday evening weathercasters, with the morning weathercasters a close second. TV stations obscure this lack of education by calling their presenters "meteorologists" and sometimes using impressive titles like "lead meteorologist", "head meteorologist", or "senior meteorologist" without any basis in real knowledge.

Let's be honest here, a B.S. in atmospheric sciences is the absolutely minimum background required for someone to have an informed view of the climate subject. A person with a B.S. degree has had calculus, physics, a good course in atmospheric physics, a class in atmospheric radiation, and quite probably one in climate. This is not even close to the education that someone in graduate schools gets and particularly someone working in the climate arena. So quite frankly, 75% of the TV folks don't have the knowledge base to provide a truly informed decision. The rest may be good communicators and fun to watch, but I wouldn't put much credence in what they say on topics outside their educational experience.

I should note that here in Seattle our TV weather contingent is quite strong. Jeff Renner, Shannon O'Donnell, M.J. McDermott have B.S. degrees in atmospheric sciences from the UW and deep experience. Rich Marriott has a M.S. Steve Pool has co-worker Scott Sistek with a UW B.S. and I tutored Steve for several years in the subject. Rebecca Stevenson has been studying the subject through Mississippi State and sat in on my senior forecasting class.

One of the arguments presented by the weathercaster doubters is that since we can't forecast skillfully more than approximately a week ahead, how can we predict climate a half-century from now? But the type of prediction is completely different: in one we are trying to predict the exact configuration of the atmosphere at a particular time, while in the other we are predicting climatological statistics average over extended periods of time.

So global warming claims are like anything else: before you trust someone's opinion, better insure they have the background to make an informed judgment. Don't get me wrong, M.S. and Ph.D. types can make mistakes or overhype global warming issues, but at least they have the background to truly understand the details of the subject. This is not some elitist argument as suggested by a few of the comments below--this is a complicated business and it takes a substantial investment in time and knowledge to master the details.

Saturday, April 3, 2010

Storm Review

The Friday Storm (I guess we can name it the Good Friday Storm of 2010) was one of the strongest late season windstorms in a while, with many locations experiencing gusts over 60 mph, and a few feeling true hurricane force winds. (Point of information: true hurricane winds require the sustained winds, averaged over two minutes, to exceed 74 mph). Such winds were achieved at Tatoosh Island yesterday. Here are some samples of max gusts (thanks to Scott Sistek of KOMO TV for collecting them)
  • Tattoosh Island: 94 mph
  • Lincoln City, Ore.: 78 mph
  • Destruction Island: 78 mph
  • Cape Disappointment: 74 mph
  • Oak Harbor: 62 mph
  • Bangor Sub Base: 62 mph
  • Kirkland (waterfront): 62 mph
  • Everett (Paine Field): 62 mph
  • Bellingham: 61 mph
  • Seattle (Alki Beach): 61 mph
Tens of thousands of homes lost power, including all of the San Juan Islands for a while.
Here is the hourly weather plot at Tatoosh Island. The the pressure dropped to 28.85 inches of mercury...around 976 mb as the low center moved NE in the close vicinity. And the maximum winds spiked after the lowest pressure. This is classic. Wind are not strong in the center of the low, but on its flanks where the pressure gradients (change in distance) are greatest.

The forecast the day before was close, but not perfect..here is the sea level pressure prediction made on Thursday. The low was displaced a small amount to the SE of the actual position and was not quite as deep as reality, but more than good enough to indicate a threat. National Weather Service warnings were highly accurate.


An interesting aspect of this event was the early snow. We had some moderately cool area over us and the evaporation and melting of precipitation forced the snow level down to the surface in some locations, particularly those over 500 ft and particularly over the SE side of the Olympics (Silverdale, Hood Canal Region). This location often experiences snow under strong SE flow--the air if forced to rise by the Olympics and evaporation and melting is favored there.

And snow is the big story now...1-1.5ft have fallen in the mountains from this event and another 1/2 feet will come today. Avalanche danger will be high in uncontrolled areas, but elsewhere this is a real opportunity for fine late season snow fun.

Thursday, April 1, 2010

Storm Watch

9 PM Update: The latest run (WRF-GFS) is virtually identical to this morning's forecast. This should be a good storm, but we are not talking of an event like the Chanukah Eve or Inauguration Day windstorms. The NWS has just put out an ominous bulletin on their web site and to show it is serious it is all red.

An unusually strong spring storm is approaching and will hit tomorrow. It could end up being the strongest winds in several months for the Northwest lowlands. And we have the added complication of some trees starting to leaf out--which makes them more vulnerable to a strong blow.

Let me show you a series of surface pressure charts for tomorrow, produced by the UW WRF numerical prediction system. The maps are for 8 AM, 11 AM, 2 PM, and 5 PM tomorrow.
A perfect track for strong winds over Puget Sound and the WA coast--right across the NW corner of the Olympic Peninsula (see my book for information about optimal storm tracks). The largest pressure gradient and strongest winds will be later in the afternoon...not the morning...for Seattle and vicinity. What kind of winds? Would not be surprised to see 40-60 kts over Puget Sound and 20-40 kts over land. Expect some power outages.

And the fun doesn't end there! As the low moves past us, there will be a westerly surge through the Strait of Juan de Fuca that will hit Whidbey, northern Olympic Peninsula, and southern San Juans.
You want more? You got it! Moderate to heavy precipitation will strike the region, with 2-5 inches of precipitable water in the mountains. Guess what, a lot of that will be in the form of snow...with some areas getting several feet. Check the 24h snowfall ending 5 AM Saturday below. Get those skis ready! But a warning--the avalanche danger is going to be substantial when this is all over.