...STRONG STRAIGHT- LINE WINDS...LARGE HAIL... AND LIGHTNING ARE MAJOR WEATHER THREATS IN THE NORTHWEST...
Straight line winds
Downburst winds from a thunderstorm usually result when evaporation of raindrops cools air within a storm. This pocket of cooled air, heavier than the surrounding air, accelerates downward to the ground. As the cool air impacts the ground, it spreads out from the area of impact causing strong winds.
Winds generated from this process can exceed 100 mph. Weather forecasters call these bursts of wind "microbursts" if they are less than 2 1/2 miles across and "macrobursts" if they are greater than 2 1/2 miles across. These downbursts of air can be detrimental to aircraft and can cause extensive damage, injuries and fatalities.
Staying indoors when thunderstorms are present is good protocol.
Hail, another thunderstorm threat, also occurs in the northwest. Hail forms within thunderstorms as liquid water freezes in the cold mid and upper levels of storms. This ice is kept aloft by strong updrafts (convection).
Hailstones may vary from pea-size to larger than softballs. Hailstones can do tremendous damage to farm crops, either as large hailstones or as an entourage of small hailstones that accumulate to a depth of several inches. Large hail can easily damage vehicles and buildings and can be life-threatening to animals and people. Even small hail can be dangerous to motorists when it accumulates on roadways.
Each year over 300 people in the U.S. are struck by lightning while working outside or during other outdoor activities. An average of 54 people are killed by lightning each year in the U.S. and several hundred others are injured and are left to cope with permanent disabilities.
Lightning can strike as far as 10 miles away from any rainfall and has been documented to strike up to 70 miles away from the thunderstorm which generated the lightning. Many lightning victims are struck ahead of the storm or shortly after the storm has passed.
Outdoors is the most dangerous place to be during a thunderstorm. Watch for darkening cloud bases and head to safety before that first lightning flash. If you can hear thunder, the storm is close enough that it could strike your location, and you should seek shelter. If lightning is forecast, plan an alternate activity or know where you can take cover quickly.
If caught outside and lightning is in the immediate area,, and there are no safe locations nearby, the following steps
will help decrease your chances of being struck by lightning. Do not seek shelter in partially enclosed building, or
tall objects such as an isolated or small group of trees. Stay at least 15 feet apart from other members of your group
so the lightning won't travel between you if hit. If
you can possibly run to a vehicle or building, do so! Sitting or crouching on the ground is not safe and should be
used only as a last resort if an enclosed building or vehicle is not available.
Lightning injuries can lead to permanent disabilities or death. If someone is struck by lightning, call 9-1-1 or your local ambulance service. Give first aid as quickly as possible. People struck by lightning carry no electrical charge that can shock others, so you can examine them without risk.
Try to get indoors during all thunderstorms. When thunderstorms threaten you this season, tune to NOAA Weather Radio, The Weather Channel, or your local radio or television stations for up-to-date information.
This week is severe weather awareness week in the Pacific Northwest. Now is the time to get prepared for thunderstorms and hazardous weather such as strong gusty winds, hail, and lightning. Public safety information statements will be issued throughout the week to help you know how to respond when severe weather threatens.
This message is brought to you by your local NOAA National Weather Office.
HOW FAR IS THE LIGHTNING?
It takes thunder about 5 seconds to travel one mile. So, if you count the seconds from the flash to the thunder you can calculate the distance. A 10 second flash to thunder count would mean the lightning strike was 2 miles away.
Additional Links of Interest...
Spotters Guide to Estimating Hail Size
Historic Thunderstorms of Oregon
Notable Thunderstorms of Eastern Washington
Tornadoes of Eastern Idaho
Severe Emergency Plan for Inland Pacific NW Schools
Preparedness for Thunderstorms
NOAA's Lightning Safety website
- Each local office may have photographs online (
see office links below
Remember, in times of severe weather, you can get all these vital NOAA/National Weather Service messages via NOAA Weather Radio, your favorite local media, or through NOAA's National Weather Service websites.
For questions about local Severe Weather Preparedness, contact your local NOAA National Weather Service Office: