A weak tornado is presumed to have touched down in a Vancouver, WA neighborhood around 3:15 p.m. Friday.
The damage was minor and limited to some fencing, a tree and some backyard items overturned but KIRO 7 Pinpoint Doppler Radar detected some weak rotation just off the ground at the time of the damage.
This corroborates a survey by the National Weather Service in Portland which estimates that it's likely a weak tornado -- with the lowest rating of EF-0 on the Enhanced Fujita scale -- touched down in the Orchards neighborhood of East Vancouver.
EF-0 tornadoes are generally capable of winds up to 85 miles per hour.
There were no reported injuries.
There is believed to have been no sighting of a funnel cloud or tornado, so Doppler Radar evidence and a survey of the area are what supports the belief a tornado touched down.
How does Doppler Radar spot a tornado?
In the image from the KIRO 7 Pinpoint Stormtracker at 3:15 p.m., the red colors are winds moving away from the Portland radar site, which is off-screen to the left, or west. The green colors are winds moving toward the radar.
In other words, in this instance, reds are winds blowing west to east and greens are winds blowing east to west.
Where the greens and reds meet -- known by meteorologists as a "couplet" -- is the site where a funnel cloud or tornado would be most probable in a thunderstorm. In this case, the rotation was pretty weak, but still detectable.
Rather weak couplets like this are actually detected often when strong thunderstorms occur and very, very rarely produce tornadoes or damage.
Had there also been a sighting of a funnel or tornado, a Tornado Warning would likely have been issued.
By the time the damage was reported, the radar indication of rotation had rapidly diminished.
How often do tornadoes hit Washington?
Because of our relatively cool climate, thunderstorms are rarely able to grow tall enough and sustain themselves long enough to produce tornadoes. But they do happen.
On average, one to two tornadoes occur in Washington each year. Most of those are in southern Washington as moisture, warmth and atmospheric instability tend to be greater there than farther north around the Puget Sound region.
Tornadoes have occurred in eastern Washington as well where temperatures in the spring through fall are warmer.
Vancouver has a notable tornado past.
In 2008, an EF-1 tornado touched down with significant damage.
The Portland-Vancouver F-3 tornado of April 5, 1972 still stands as the deadliest tornado on record in the Pacific Northwest. Six people were killed and more than 300 injured, including 70 students at an east Vancouver school. The damage swath was nine miles long.
The last tornado in the Puget Sound region was an EF-1 near Gig Harbor on Jan. 19, 2015 (pictured)
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