Severe Thunderstorm, June 4, 2009

I remember May of 1993. An area of low pressure sat offshore and rotated counter-clockwise, sending waves of warm, humid air into our region. Imagine spokes on a wagon wheel, and each time a spoke passes over there is rain, winds, lightning, and thunder. In May, 1993 a lot of spokes passed over, and we had a very lively, memorable month (and a very enjoyable one, if you ask me!).

This week a similar occurrence took place. A low off northern California sent warm, moist air into the western half of Oregon from the south. The result: thunderstorms on several days. The biggest occurred on Thursday, June 4, and was the strongest local storm I have seen in Corvallis since I moved here in 1989. The combination of heavy rain, high winds, and long-lasting, intense lightning-thunder was unlike anything I have witnessed here.

The strongest storm activity occurred between about 4 and 5 PM, though this varied from place to place. While lightning and thunder were reported throughout the area, rainfall was very spotty: some locations had rain totals well over an inch in less than an hour, while others had very little. Corvallis-Albany’s official weather station at Hyslop Experiment Station on Highway 20 (OSU Crop and Soil Science) received only .14 inch.

I had been watching the satellite and radar images, and in mid-afternoon began to see some very significant “echoes” approaching our area. Doppler radar images (from the National Weather Service) are color coded. The strongest storms, based on rainfall rate and upward air movement, show up in red. We seldom see red here — our storms are usually pretty “wimpy” — but Thursday I saw red everywhere! Sure enough, the action started shortly thereafter. Many observers reported significant, severe weather. Some examples:

Peoria (southeast of Corvallis, southwest of Albany): a tornado touched down and tore the corner off the roof of a building.

Detroit (22 miles east of Salem): a severe thunderstorm produced winds estimated at 80 mph (reported by a trained weather spotter). Numerous trees fell along state highway 22.

Shedd (south of Albany): winds were measured at 71 mph on an automated weather station. Rain totaling .71 inches fell in 20 minutes. Pea-sized hail was reported.

Near Independence: winds exceeded 60 mph; nearly a half inch of rain in 20 minutes.

Salem: a Microburst (very intense downdraft winds) on the back end of a thunderstorm complex caused winds to exceed 60 mph. Water reported 8 inches deep at Lancaster Mall.

Corvallis: a lightning strike cause a fire which completely destroyed a home.

2 miles west of Philomath: 1.55 inches of rain in 90 minutes.

Southwest Corvallis: .98 inches of rain in one hour.

By Friday, calm had returned to western Oregon, but the low pressure offshore remains in place and may produce more action in the next week.

By the way, there have been much stronger thunderstorms in the area before – it’s just that I wasn’t here to witness them. For example, in 1953 a tornado struck downtown Corvallis, causing moderate damage. Thunderstorms have dropped as much as 2 inches of rain in a few hours. But Thursday’s storm was a very significant one, and not easily forgotten.

If you have an interesting story to tell about the storm, please write and tell me about it. I love collecting weather stories!

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