BREAKING NEWS: "SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATE THAT THE TROPICAL WAVE AND ASSOCIATED LOW PRESSURE AREA LOCATED ABOUT 250 MILES EAST OF THE WINDWARD ISLANDS COULD BE DEVELOPING INTO A TROPICAL DEPRESSION" (NHC).

UPDATE THU. EVENING: Blog reader Donny tipped me off to some excellent outflow boundary action (also including a sea-breeze front moving inland then retreating) on the Jacksonville, Florida radar tonight. I have posted radar animations* here.

UPDATE: In the video blog below, I talk about the tiny storm and the huge outflow boundary that it generated, and what happened when that boundary ran into others. Blog reader Mike was in the core of the storm centered over St. Charles, MO, and says that it was very localized but winds were in excess of 70 mph, causing his power to fail for two hours, and knocking down small trees and large branches, up to 12 inches in diameter. His roof even started to vibrate to the high winds! He said it brought back memories of the Great Saint Louis Power Outage of 2006, which was also caused by (a much larger) thunderstorm derecho [WikiPedia].

http://wwwa.accuweather.com/video/video_inline_launchV3.asp?video=http://qt.accuweather.com/flashvideo/vblog_ferrell/jf-070830-outflow&category=&thumb=http://qt.accuweather.com/flashvideo/vblog_ferrell/jf-070830-outflow.jpg&hd=true

NOTE: THE VIDEO ABOVE MAY BE PRECEDED BY ADVERTISEMENTS

The event was so localized that The NWS only issued one storm report, out of Bridgeton, Missouri, saying "ROOF TORN OFF BUSINESS AT AMERICAN EAGLE PLAZA IN EARTH CITY." The storm was not covered by the media in St. Louis or St. Charles, according to Google News. UPDATE: Mike points out the KMOV weather blog did in fact cover the story, and also posted a video of the roof damage. STLtoday also mentioned the storm, saying that 10,500 lost power.

NOTE:

The "super-fast" radar animation in the video above didn't turn out the way I saw it on the screen, so I've posted this link where you can download the original Quicktime* radar movies from AccuWeather.com RadarPlus. At top speed, it's easy to see which outflow boundaries are colliding with each other, and which storms they are coming from. The loop repeats several times during the video. You can also download the Velocity and Storm-Relative Velocity loops there as well... the storm was so small, and so close to the radar, I couldn't make out much of interest on those.

*Quicktime required. "Save Target As" required for IE.

ORIGINAL POST:

THE OUTFLOW BOUNDARY EXPANDS...

Blog reader Evan tipped me off to a spectacular example of thunderstorm outflow boundaries [WikiPedia] tonight around Saint Louis. We have talked about these a couple times before (here in town and during the Las Vegas Dust Storm).

Typically when you see well-pronounced outflow boundaries on radar, they come from pretty hefty storms, but these guys were tiny! Here's a radar map showing the large boundary, and you can download radar movies* here.

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