Fog and Roadway Icing: The Warning of the Husky Bus Crash

Yesterday, a bus with a number of students of the Husky Band overturned on Interstate 90 just west of the town of George, Washington (see map  below) as they headed to the Apple Cup game in Pullman.   A number of students sustained injuries, but thankfully none were life threatening.

As I will discuss below, severe icing conditions occurred due to fog and freezing temperatures, and with modern observing, modeling, and warning technologies, coupled with cautious driving, the number of  such events can be greatly reduced.

The accident occurred around 5:30 PM Thursday.  A plot of temperatures at 5 PM (with the accident location indicated by the red circle) shows freezing and below freezing surface air temperatures, with 31F reported in the immediate vicinity, while to the southeast temperatures were in the 40s.

A 13-h model forecast of winds and surface air temperature valid at 4 PM was very realistic, showing the threatening cool temperatures over the accident region, while warmer temperatures were predicted over SE Washington.

The cool temperatures were accompanied by low clouds and fog, something shown by a high resolution visible satellite image around 1 PM (see below).

The nearby Grant County Airport (MWH) reported dense fog all day and FREEZING FOG starting around 435 PM (times in UTC, with 0000 UTC being 4 PM)

I have spent a large amount of time studying and working with WSDOT (Washington State Department of Transportation) and SDOT (Seattle Department of Transportation) on the issue of roadway icing.  And I have occasionally done some forensic work on roadway icing accidents.  Roadway icing is probably the greatest meteorological threat faced by WA State citizens.  More than windstorms, flooding, thunderstorms and everything else (I have checked the numbers).

One thing I learned:  freezing fog can be a huge threat.  Fog has lots of water content and when fog droplets contact a cool  roadway surface, substantial icing can occur rapidly.  

When air temperatures are below 35 F and you see fog, you should immediately slow down. 

Why 35F?  Because air temperatures are measured at roughly 6 ft above the surface (car thermometers are at roughly 2 ft above the surface) and surface temperatures can be cooler that air temperatures, particularly at night.  

The threat of icy roads was already evident that morning with the Grant County Sheriff reported icy roads.

Reducing Roadway Icing Injuries and Deaths

There has been substantial progress in reducing roadway icing injuries and deaths.  WA State WSDOT has made large strides, putting up RWIS roadway weather stations around state roadways, educating their plow operators (e.g., bridges ice up first!), using aggressive anti-icing pretreatments on vulnerable roads, and working with us at the UW to build the road temperatures prediction capabilities and public websites that would provide guidance to their staff and warn drivers.  One application I am particularly proud of is our Road-Weather web displays, such as the I-90 page (see
below)

But unfortunately, Washington State efforts are beginning to slide and new technologies that would promote roadway safety are not moving forward.   Recently I learned that Washington DOT (WSDOT) is going to cut all funding to the roadway weather pages and data streams produced by the UW (e.g., I-90, SR-20, I-5, Ferry Weather), substantially cutting back the information available to the public.

Just as serious, we are not moving forward with protective warning technologies that could produce timely warnings of dangerous road condition for WSDOT personnel and the motoring public.  

 Today, there are immense amounts of information describing, in real-time, weather and surface conditions around the State.  Thousands of surface stations, weather radar information, amazing new weather satellite capabilities, smartphone pressures, to name only a few.  Plus, high resolution weather modeling has improved rapidly, with new rapid-fresh forecasts being made every hour.   And soon cars and trucks will serve as massive data sources.    

This huge potential is magnified by the fact that most folks have smartphones, and thus we could provide real-time, vehicle specific warnings of threats on the roads ahead.  I believe we can stop many of the fatal/injuring accidents caused by snow and ice on the roadway, such as the tragic accident of a pregnant woman on I-90 last year.

Unfortunately, the Washington State transportation bureaucracy is not pushing forward on such technological advances, with the explanation that WSDOT lacks the funds to do so.  Hopefully that will change someday.   The effective use of weather information, coupled with smartphone distribution of warnings, has the potential to save many lives and to substantially lessen weather-related carnage on our roads.

from Cliff Mass Weather and Climate Blog https://ift.tt/2TC9FOa