PORTLAND, Ore. (KOIN) — A powerful fall front brought rain, wind and tornadic activity to the Portland metro area on Monday afternoon.
The first round of severe weather started just before 3 p.m. as the National Weather Service out of Portland issued a tornado warning for parts of Clark County in southwest Washington.
The tornado warning was just northeast of Vancouver and included places like Brush Prairie and Battle Ground. The warning expired just before 3:30 p.m. as the heavy rain continued to move through the metro area.
The second round of tornadic activity came in from a National Weather Service Trained Weather Spotter. A funnel cloud was observed near Sandy & 138th St. around 3:40 p.m. from the Parkrose area.
As the strong fall front moved east its final spin was with a brief severe thunderstorm warning in southeast Portland. Both the tornado warning and severe thunderstorm warning were radar-indicated. So, no human eyes saw rotation, but the winds seen through the radar velocity feature helped indicate the rotation.
The velocity section of the radar isn’t something that’s always shown. It’s a good indicator of the inbound and outbound winds associated in a storm.
The inbound winds are detected by the radar picking up on winds that are moving towards the radar sight. This is highlighted with the color green. Outbound winds, or winds that are moving away from the radar indicated in red. When you have the red and green nearby, that is a good indication that rotation is happening in a given area on the map. This color combination is known as a ‘rotational couplet‘ and is usually a good indication that rotation is happening, but can only be confirmed visually.