Blowing dust, low visibility plague eastern Idaho

In a more tropical climate, Monday’s relentless wind might have prompted a hurricane warning. But eastern Idaho is much drier; and instead of torrential rains, the sky was filled with dust … so much dust driving became hazardous and highways were closed.

Interstate 15 was the first to succumb to the blinding dust. ITD’s District 6 crews closed the interstate between Idaho Falls and Roberts (mileposts 119 to 135) at 3:08 p.m. Traffic was diverted to U.S. 20 through Rigby.

How windy was it?

The National Weather Service issued a warning for sustained winds of between 35 and 45 mph, with possible gusts reaching 60 mph in eastern Idaho. In retrospect, the weather service reported steady winds of about 58 mph and a gust of 67. (Tropical storms carry winds of 39 to 73 mph; hurricane winds begin at 74 mph for a level one on the Saffir-Simpson wind scale.)

How windy was it?

A gust of wind pummeled a “road closed” sign on I-15, breaking the cross arm. Flags straining at the pole outside the district office looked more like a maritime small craft advisory for ocean fishing trawlers (see photo, left). Gale force winds generally are considered to be 39-54 miles per hour. (See information below from Wikipedia)

How windy was it?

Seagulls were looking for tie-downs at regional airports and farmers in western Wyoming were tilling Idaho soil.

Low visibility prompted the first-ever closure of Idaho 32 between Ashton and Tetonia at about 4:30 p.m., explained D-6 communication specialist Bruce King.

The rural highway reopened at 9:23 p.m. and traffic resumed on the interstate at 10:38 p.m.

Road closures resulting from blowing dust and reduced visibility are most likely to occur on open stretches of highway in the spring and fall, although they can happen at anytime the ground is bare. Motorists are urged to use extreme caution when traveling through areas that have a history of dust storms. (See related story).

From Wikipedia:

The most common way of measuring winds is with the Beaufort scale which defines gale as wind from 50 to 102 km/h. It is an empirical measure for describing wind speed based mainly on observed sea conditions. Its full name is the Beaufort Wind Force Scale.

On the Beaufort Wind Scale, a gale is classified as: Moderate Gale (32–38 miles per hour), Fresh Gale (39-46 mph), Strong Gale (47-54 mph) and Whole Gale (55-63 mph). A gale is a type of wind description preceded by Calm, Light Air, Light Breeze, Gentle Breeze, Moderate Breeze, Fresh Breeze, and Strong Breeze and succeeded by Storm, Violent Storm and Hurricane on a Beaufort Wind Scale. There is a unique Beaufort Scale number and a unique Arrow Indication for each type of Wind Description mentioned.

Published 5-3-13