Thunderstorm

Preparing for thunderstorms pamphlet

Washington natives and transplants alike are well-versed in being prepared for the climate of the Pacific Northwest, but significant weather deserves additional safety measures. The Pacific Northwest annually receives the least amount of thunderstorm days compared to any other region of the country, so we sometimes get lulled into a false sense of security; this warm, fuzzy feeling is usually one of the first items to get thrown out the window when severe weather strikes! Thunderstorms are the most dangerous weather scenario that people are likely to encounter frequently, and can either form rapidly within your local area or be carried into the Puget Sound with the prevailing winds. Preparation now can prevent a bad day from becoming worse.

There are three basic phases in the life-cycle of a thunderstorm, and the various hazards a thunderstorm can produce are present at different times.
Stage 1: Winds, Lightning.
Stage 2: Winds, Rainfall/Flooding, Lightning and Hail.
Stage 3: Winds, Flooding, Lightning and Hail.

Resources to help you get ready:

• Commuters: Are you prepared for emergencies?
• Preparing for and responding to power outages
• Help keep storm drains clear, clean gutters and down spouts regularly: adopt a drain
• Flood safety: preventing, protecting, cleaning up and drying out

Lightning and thunder

Lightning is typically the first feature you will see outdoors that indicates weather is going from “Everyday Overcast” to “Potentially Messy.” If you count the seconds between a lightning flash and the rumble of thunder, each second equals 1 mile of distance between you and the lightning bolt. (For example, 4 seconds between flash & rumble means that lightning struck ~4 miles away from you.) Lightning Warnings issued by the Department of Commerce agencies (NOAA & National Weather Service) and the Department of Defense agencies (US Air Force and US Navy) mean that lightning has already struck within 5 miles of a given area at least once within the last 15 minutes. They remain in effect until 15 minutes of lightning/thunder-free time has elapsed. If watching a weather report on television, over the Internet, or listening by radio, pay attention to where storms are reported and which way they are moving. Lightning can potentially strike as far out as 50 miles from the storm cloud itself, in any direction!

High winds and tornado/waterspouts

Storm systems are always associated with a change in wind direction, as well as an increase in wind speeds for a period of several hours. The rough terrain of the Puget Sound area is unfavorable ground for tornadoes and/or waterspouts to develop, but so-called “Straightline Winds” are actually enhanced by our environment. People should make every effort to avoid being outdoors during High Wind activity due to the difficulty of traveling on foot as well as the potential for loose debris to be blown around & cause damage or injury.

Heavy rainfall and flooding

Thunderstorms are often accompanied by significant rainfall within a period of 1-3 hours. During the heaviest showers, visibility can be reduced to ranges experienced during morning fog events. Driving during heavy rain requires more vigilance, as roads become slick and dangerous (hydroplaning). Drivers will often drive slower as visibility makes it harder to navigate through city streets as well. Low-lying areas may temporarily flood as storm drains get blocked with debris. Nearby rivers may slowly rise & flood as well; monitor local reports for any updates or warnings.

Damage from ice pellets/hail

Thunderstorms with intense vertical winds as well as horizontal winds can produce hailstones.
Smaller hailstones can be ejected from thunderstorms 10-15 miles away from the cloud itself, while heavier stones fall directly down from the cloud. Any hailstone 0.75 inches (2cm) or larger is considered capable of causing injury to people & animals or damage to property.

Other resources

• WA State Emergency Management safety tips
• National Weather Service, Seattle
• Seattle Department of Transportation
• Washington State Department of Transportation
• Seattle City Light: when the power goes out
• Seattle City Light: system status
• Puget Sound Energy
• Port of Seattle: Sea-Tac Airport

UW Suspended Operations Policy

“The President or the President’s designee(s) may declare a temporary suspension of any or all University operations due to an emergency situation that adversely affects University operations, public health, or the well-being and safety of students, faculty, and staff.Events which might require suspending operations include, but are not limited to: severe weather or natural disaster, spread of a communicable disease, fire or related hazard, an immediate threat to the safety of the campus community, damage to or failure of UW infrastructure, equipment or mechanical systems.”

Keeping updated

• UW Information Line (recorded message) 206-UWS-INFO, Toll Free: 1-866-897-INFO
• Sign up for UW Alert
• “Red Alerts” on UW Home page
• Your supervisor, department/college administrator or building coordinator
• KOMO 1000 AM (Emergency Alert System)