Saturday, July 21, 2018

The Unnecessary Tragedy in Missouri: Lessons for Our Society

The headlines in the Seattle Times and many other newspapers this morning describe the terrible loss of life on Table Rock Lake near Branson, Missouri as strong winds from a rapidly moving convective system resulted in the flooding and sinking of a duck boat filled with tourists.

The tragedy of this loss is compounded by the fact that it was totally avoidable:  National Weather Service forecasts and warnings were excellent, and the weather radar showed the developing threat well before the boat even entered the water. 

Unfortunately, this kind of avoidable tragedy is not an isolated incident, highlighting the need to connect the ever increasing abilities of meteorologists with the needs of society to be warned and to avoid severe weather.


The cause of the tragedy was a severe line of thunderstorms, with outflow winds in front of them.  The incident occurred over southwestern Missouri around 7:00 PM central time (5 PM PDT, 0000 UTC) on Thursday. 

Radar imagery clearly showed the approach of the severe convective line and strong evidence of associated powerful winds.  Let me show you using Springfield, Missouri NWS radar imagery.  Remember the accident occurred around 0000 UTC 20 July (meteorologists use a 24-h clock with the time at the Greenwich meridian).

At 2246 UTC (5:46 PM Central Time), a very strong convective line was approaching the area.  Red colors indicate heavy precipitation, perhaps with hail. (this field is called reflectivity, the amount of radar return from the precipitation, which is related to intensity)


At 6:17 PM, before the boat went into the water, the line was heading straight towards the lake, with many intense cells.  Look closely and you will see a faint line ahead of the main action--that is the gust front, the leading edge of strong outflow winds in front of the convection.


Fifteen minutes later, the system was still approaching

 And was stronger and imminent at 6:45 PM.

At 7 PM, the gust front had crossed the lake and the heavy precipitation was on them.


Modern radars are Doppler radars that provide the velocity of the precipitation (and the air it falls through) towards or away from the radar.   The Doppler velocities at the lowest elevation angle  from the horizontal (.5 degree) at 6:31 PM shows very strong winds behind the gust front.  


Blow up radar reflectivity and Doppler velocities at 659 PM show the threat clearly.



The National Weather Service was on top of this, with excellent forecasts and warnings.  Here are some examples:

11:20 a.m. — Severe thunderstorm watch issued for all of southwest Missouri, including Stone and Taney Counties (and the Table Rock Lake area) until 9 p.m. Potential for severe thunderstorms and isolated wind gusts of 70-75 mph.
5:45 p.m. — Severe thunderstorm warning for Newton, Cedar, Polk, Barry, Greene, Jasper and Dade counties. 60 mph wind and 3/4-inch hail possible.
6:32 p.m. — Severe thunderstorm warning for Taney, Stone, Barry counties until 7:30 p.m. Branson and Table Rock Lake are specifically mentioned in this warning. 60 mph winds and hail less than 3/4 inch possible.
6:45 p.m. — Severe thunderstorm warning for Webster, Douglas, Wright, Christian, Stone, Barry, Lawrence, Greene counties until 7:45 p.m. 70 mph winds and 3/4-inch hail possible.
So we had a failure mode with excellent observational data and official warnings of the event, but lack of protective action by the tour operator.   This type of failure mode is not limited to this event.

Another potent example:  the wine country fires of last October.   44 people died and billions lost from a severe weather event (strong Diablo winds) that were well forecast.   Many of the deaths of wildfire fighters of recent years were also from completely predictable weather events.  I could easily give you a dozen more examples of this kind of thing.


Our ability to diagnose and predict the weather has improved immensely during the past decades, but we are not making full use of this information to save lives and property.  Some of the problem is education.  Some of it is poor communications.   But in a world of internet almost everywhere and smartphones in every hand, we should be able to do better.    

Diagnosing and forecasting the weather is only half the battle...the easier part.   Communication and effective use is the hard part.









Thursday, July 19, 2018

Winds Drive the Explosive Substation Fire Near the Dalles

One of the most explosively growing fires in the nation occurred during the past two days near the Dalles, Oregon, just south of the Columbia River...and winds have been a big factor.  It appears to have begun about 5 miles SE of the Dalles around 3:30 PM Tuesday and has grown to over 70,000 acres (see map)


To get a feeling for the growth, let me show you some MODIS satellite images.  Below is a series of satellite images using wavelengths the show burned areas.  The Columbia River is evident, as is Mt. Hood.

 On Tuesday...nothing...but you can see some indication of the Columbia Gorge fire of last year.


 Wednesday.... a big  burned area (red color) is evident, with a run of roughly 18 miles


Today around noon--extensive growth of the fire.


The fire is growing in grass, sage, and in some of the extensive wheat fields of the region.   Such fuels burn explosively and are known as "flashy".

The fire was apparently human caused, with the media suggesting some kind of criminal investigation.   But looking at the temperature and humidity at the Dalles, temperatures were quite warm (around 100F) for the days leading to the incident.  That is about 10F above normal.
With warm, dry conditions over northeastern Oregon during the past month, the crop moisture index showed very dry conditions in the area of the fire.


But what about the winds, which can stoke a fire and cause it to run rapidly in spac?.  Winds really surged later on Tuesday, and have been blowing since then--sustained winds around 20-25 mph with gusts above 30 mph.  Highly predictable when marine air surges into western WA this time of the year.
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Ironically, the wind acceleration was associated with cool air moving into western Oregon and Washington, enhancing the pressure difference across the Columbia Gorge.  The winds should weaken tomorrow, as the west side of the region begins to warm.   Thus, there is a substantial hope that the fire will slow and hopefully brought under control.   So far, the fire season has been relatively normal over our region, but the threat is increasing steadily as we enter the warmest period of the year.

Tuesday, July 17, 2018

Marine Air Surges Inland

For those of you unhappy about the recent warm days, living in a city where AC is rare, relief is at hand.

As I speak, marine air is pushing rapidly into western Washington.  Trees are swaying, temperatures are rapidly falling, the air is moistening, and my wind chimes are ringing.   Life is good.    Our natural AC is turned on, and a night of comfortable sleeping is in store.

It has been substantially warmer than normal for the past week, with several days of high temps that were 10F or more above normal (see plot, purple line shows the average highs, cyan, average lows).  There was a bit of marine air leakage today...resulting in highs dropping 5-7F from yesterday.

All meteorologists know to watch the onshore pressure gradient--the difference in pressure between the coast (say Hoquiam, HQM) and Seattle (SEA)-- to get an idea of the amount of marine influence.  Just a small change from offshore to onshore pressure gradient can make all the difference.  Here are the pressure differences today.  Note that the Hoquiam to Seattle pressure difference rose to 3.5 hPa--that is enough to guarantee a good surge of marine air.

Winds have responded to the onshore pressure gradient. At Smith Island, in the eastern exit of the Strait of Juan de Fuca (and just offshore of northern Whidbey Island), winds climbed to 25 knots as of 9 PM.  At Race Rocks, near Victoria, it hit 40 mph.


At the University of Washington, winds have also picked up to around 10 knots (top panel).  Temperature at the UW is falling rapidly (third panel) and dew point rises (more moisture in the air).  As a result, there has been a huge increase in relative humidity (fourth panel) from 30 to 75%.  This will help reduce fire risk in the west.
The onshore flow is also bringing in the low clouds that have been waiting their chance offshore.  The visible satellite at 8 PM Tuesday shows stratus/stratocumulus pushing inland, particularly south of the Olympics through the Chehalis gap (see below).  If you live in western Washington expect to see lots of clouds when you wake up Wednesday morning.


The next few days should be typical for mid-summer--low clouds in the morning and temperatures rising into the upper 70sF during the afternoon.  Perfection.

There is a cloud in the silver lining though....with cool air and higher pressure in western Washington, winds over the eastern slopes of the Cascades (e.g., Ellensburg) should strengthen considerably, resulting in an increase potential for stoking any fires.   Even with the minor cool-down today, the winds at Ellensburg revved up quite a bit, with sustained winds reaching 23 knots and gusts to 37 knots  this evening (see plots)


Expect even stronger winds there tomorrow.
________________________________________________

Morning update.  The cool air moved in, but was quite shallow.  Here are the winds and temperatures above Sea Tac Airport (time on x-axis, pressure on y axis, 850 is about 5000 ft).  Above that level, nearly no change in temperature, but at around 2000 ft the temperature it  is about 10C (18F) cooler.

The visible satellite photo at 6 AM shows low clouds reaching the Cascade foothills, but it is still clear in the mountains.  A hike this morning to a low peak would be glorious.....going from cool to warm and looking down on the low clouds.    But hurry!  They will burn back quickly.




Sunday, July 15, 2018

The Technology That Can Provide Society with Actionable Information For Dealing with Global Warming

The long-term impact of global warming is one of the key issues of our time.

Greenhouse gases are increasing rapidly and it is becoming increasingly clear that mankind will not significantly reduce emissions during the next few decades.
Global climate models, forced by increased greenhouse gases, suggest major changes in the Earth's climate and weather regimes, especially by the middle to end of this century. 

But these models do not provide actionable informationWhy? 

(1)  Because global climate models do not possess fine enough resolution to describe terrain, thunderstorms, and other local effects that can be critical for determining future climate change in many areas (like the Northwest).

(2) Global climate models do not necessarily agree on even the large scale impacts of climate change.    And there is also uncertainty regarding how much greenhouse gases will increase during this century.



Although global climate models have issues, society still needs future climate impact information. 
  • Infrastructure must be built or adapted to deal with changes in climate-- with examples including dams, reservoirs, drainage and water systems, coastal and riverside facilities, and more.
  • Our management of the environment, such as forests, wetlands, and the Sound, may need to be altered with upcoming climate change in mind.
  • And we may well have to alter where we live, build, and do agriculture.
Clearly, we need reliable information on how our local weather and climate will change as greenhouse gases increase.  Information that provide both our best estimates of what will happen and their uncertainties.   And we don't have it.

This blog describes a proposed effort designed to provide the necessary regional climate forecasts.  One based on state-of-science modeling that is both high resolution and probabilistic and takes advantage of the latest modeling and scientific advances.


But to make this effort a reality will take resources, both in terms of personnel and computer time.

This blog proposes the development of a regional climate modeling center and is a call for the support needed to make it a reality:  from local governments, interested local businesses, wealthy individuals, large numbers of modest investors, or perhaps a foundation.

Building a Regional Climate Prediction Effort

Global models can get large-scale features correct, but can't deal with critical, but smaller scale, local terrain, surface, and water features.  How do we solve this problem?  

Regional Climate Models (or RCMs).

The idea is to run high-resolution RCMs on small domains over an extended period, using the global models to drive the boundaries of the small RCM domains.  This is called dynamical downscaling. The high-resolution domains are small enough so that the computer resource requirements are reasonable, but high-enough resolution to get the local features correct.

Several efforts are doing this, including a group of us at the University of Washington.   Let me show you an example.  On the left below is the forecast of winter (DJF) temperature change predicted for the end of the 21st century using the ECHAM5 global climate model, assuming a continued rise in greenhouse gases.   No local details at all and doesn't look very realistic.  
And on the right is a simulation from a regional climate model driven by the global model.  You can see the influence of terrain, with areas of very large warming due to melting snow on the slopes.  Much more warming and undoubtedly more realistic.
Only  a high resolution regional climate model can realistic predict the reduction in snowpack on our local terrain, since the global models lack even our major mountain ranges (e.g., the Cascades and the Olympics). 


Long experience by my group and others suggests that a regional climate model must run with a grid spacing (distance between the grid points) of 12-km or less to start to do a reasonable job with Northwest terrain.

But then there is the uncertainty issue.  You can't simply complete one regional climate run and go home (which several groups have done in the past).   Just as in weather prediction, you must run a collection of high-resolution runs (called an ensemble), each starting slightly differently and each using somewhat different physics (how we simulate processes such as radiation, condensation, precipitation, etc.).     And we need to so a variety of runs with different amounts of greenhouses gases, since there is uncertainty of their concentrations in the future.

So an ensemble of regional climate runs is necessary to provide a reasonable estimate of regional climate uncertainties and to allow the calculation of probabilities of potential outcomes.  One also needs to complete statistical calibration (more on this later).

Our results so far

No group has attempted to create a large regional climate model ensemble, until a group of us at the UW began such an effort.  Our initial funding was mainly from Amazon, who provided 18 months of some staff support and tens of thousands of dollars of time on their cloud.  Amazon gave us a good start, but that funding has run out and our project is running on fumes now.

But we have gotten far enough in to give you a taste of the power of the approach--four of the regional climate runs are complete.  So let me give you a view of Northwest climate change that no one has seen before.

Here are four high-resolution regional climate model forecasts of total winter (DJF) precipitation at Seattle, driven by four major global climate models from simulations running from 1970 through 2100.   Black dots indicate observed values.  The model values are within the spread of the observations during the contemporary period...a good sign.  The future?   A slow, but modest increase in winter precipitation.  Good for water resources if we can store it.

How about winter temperature?   No much change between 1970 and now (consistent with observations), followed by a slow rise starting in the 2030s, with temperatures at the end of the century up by about 4-5C (about 8F).  Seattle will have much more pleasant temperatures in the winter, but that has a down side:  reduced snowpack.


Our goal is to have at least 12 of these runs done by the end of the year if we can find the funding.

What needs to be done

To provide the best possible regional climate forecasts, we need to run 30-50 regional climate simulations for the Pacific Northwest, using a full range of climate models, greenhouse gas scenarios, and variations in model physics.  We know how to do this.   And once the runs are complete we need to complete statistical calibration, including fixing biases evident over the contemporary period where we have observations (such as 1970-2015).

This is all doable within 1-2 years, but it will take resources.  Support for 2-3 personnel.  Substantial computer resources.  But doing so will give infrastructure planners in the Northwest extraordinarily valuable information and greatly assist in increasing the resilience of our region to upcoming climate change.  You can't plan for what you don't know about.


So how can we get the resources to make these regional climate simulations a reality?

Might a regional or national foundation provide the assistance?  Or a wealthy individual?  If so, please contact me.

We have appealed to state and local agencies, talking about setting up a regional climate change prediction consortium, modeled after our very successful regional weather prediction consortium.   So far only limited interest.

Individual donors can also help maintain our current efforts at this UW website.


But somehow, we must find a way to make this happen. There is so much talk about climate change,  even a carbon initiative on our upcoming ballot.  Is it not amazing that the investments have not been made in securing the best possible information regarding the impacts of climate change on our region?

Finally, I have a prepared a video that goes into more detail about the necessity and scope of the proposed effort:

Saturday, July 14, 2018

The Driest Air of the Nation is Over the Inland Pacific Northwest

People think about the Pacific Northwest as being a moist place, but during mid-summer we are often one of the driest.

An excellent measure of the amount of water vapor in the air is the dew point temperature, the temperature to which the air must be cooled at constant pressure to become saturated.  The higher the dew point, the more moisture air contains. 

Here is a map of dew point at 9 AM this morning.  The lowest dew points in the nation was in the Pacific Northwest east of the Cascade crest (around 40F).  Middle of the country and in Florida?  Around 70F--very sticky.


Another measure of humidity is relative humidity, a measure of moisture that also involves temperature.  Relative humidity tells us how much moisture is in the air compared to the maximum it can "hold".   Since warm air can hold more water vapor than cool air, relative humidity tends to drop as temperatures rise.  

Here is the relative humidity at the same time as the above figure (9 AM Saturday).  The lowest relative humidities were over the  inland Northwest (both little water vapor in the air and high temperatures) and over the interior of California and eastern Texas (very high temperatures).


Relative humidity varies greatly over the day, declining substantially during daytime as temperatures rise.    Let me illustrate this for today (Saturday) using forecasts from the UW WRF model. 

At 5 AM, when temperatures were relatively cool, the driest air is over the lower elevations east of the Cascade crest (brown colors), with higher humidity along the coast.

Big changes by 11 AM, as warming causes a huge decline of relative humidity over most of the region.

And by 5 PM, near the time of max temperatures, the region was pretty much desiccated--with relative humidities below 30% in most locations away from the immediate coast.   No wonder your mouth felt parched and you grabbed a cool drink.

10 PM tonight?  Cooling temperatures resulted in an increase of relative humidities.


In contrast, dew point hardly changed during the day.  To show this, here are the dew points for 5 AM and 5 PM today.  Pretty similar. With drier air (dew points less than 40F) over much of the the high terrain and regions east of the Cascade crest--see below.



So when outsiders tease you about Northwesterners having webbed feet and other jokes of our region always being wet, feel free to correct them, noting our wonderfully dry conditions during our near perfect summers.

Thursday, July 12, 2018

Far Less Smoke over the Northwest Than Last Year

The wildfire and smoke situation is far better over the Northwest this year and there is a good chance it can stay that way for several weeks if we are careful.

Let's start by comparing the high resolution MODIS satellite imagery for yesterday around noon and the same time one year ago (below).  This year, with the exception of some clouds, has clear skies with little hint of smoke.


But last year, dense smoke, produced by multiple fires over British Columbia, was evident over that province, with substantial amounts pushing into Washington State.


Air quality, as shown on the EPA AirNOW website, is quite good over our region today(see below).


Why has this year been better? 

We started with a healthy snowpack on April 1st, which is good.  But the key has been that June had normal  to below normal temperatures around the region (see below).  And, precipitation, and particularly thunderstorms, were below normal--thus, less lightning initiation of wildfires.

Because of the good snowpack and a relatively temperate spring (except the warm period in May), the soil and fuel moistures are relatively normal right now over fire-prone areas, with the biggest dry anomalies over the western part of the region, which is far more resistant to fires.  To show this, here is the  current Palmer Drought Severity Index, which integrates past temperature and precipitation to give a measure for the moisture content of surface layer.  Not too bad over eastern Oregon and Washington.


The forecasts over the next week are favorable.  We should be dry, but not excessively warm, with highs getting into the lower  to mid 80s over western Washington.  The latest ensemble forecasts indicate high pressure building over the West Coast, but of modest amplitude (see forecast height anomaly--difference from normal--at 500 hPa from the GEFS ensemble below).


We will be dry....but paradoxically that could be a good thing in the short run, with no thunderstorm and lightning activity over the Washington and much of Oregon.  The UW WRF accumulated precipitation for the next week is shown below.  Only southern Oregon will get some lightning... and the fire folks need to be ready for that.


So what about new fires in the weeks ahead? 

It will be up to us.   The moisture content of "fuels" will slowly drop, enhancing fire danger.  And it is clear from the recent grass/sage brush fire near Vantage that some of the grasses at lower to moderate elevations are ready to burn right now.  So we have to be careful (no fireworks, no throwing lit cigarettes out of cars, no target shooting, campfires, and off-road vehicles in vulnerable locations, etc.) 

But we should not forget that fire is entirely natural in our region and much of the problem is created by us.   We are pushing our homes deep into the wildland--locations that have burned frequently for millennia.   We have mismanaged our forests, including suppression of fires and allowing them to grow into explosive tinderboxes.  And we should never endanger young men and women to save isolated homes when wildfires are raging. 


For too long, many in the media and some politicians have waved the climate change banner when wildfires have occurred, neglecting to push the necessary actions on the ground (e.g., stopping development in remote areas, thinning and burning forests).  My field can help immensely by providing forecasts of dangerous situations (like major wind shifts, upcoming lightning events), but in the end some difficult and expensive choices need to be made.