EMA Events and Activities

Tuesday, May 7, 2019 Weather Information


“What happened to my storm siren??”

Now that we have a confirmed touchdown associated with Tuesday night’s surprise tornado warning, we’re starting to get questions from folks about why certain storm sirens didn’t activate. Hopefully by sharing this information as broadly as possible, it will help calm fears or perceptions that the system failed during that storm.  First, this was definitely a surprising warning. Our atmosphere had changed considerably over the couple hours leading up to it and was no longer considered to be very tornado-ripe, at least not for bigger or more powerful tornadoes.  But ingredients can sometimes suddenly mix to produce a quick, smaller spin-up…and this one definitely spun up (and down) in a hurry. Here’s the timeline for our twisting visitor:


TIMELINE

11:18 p.m. A Tornado Warning was issued for central Butler County, between Augusta and Leon. This was for radar-indicated rotation that forecasters noticed developing in an area approximately 4-6 miles SE of Augusta, moving to the NE at 20 mph. The Warning area was relatively small and did not extend up into the city of El Dorado.

11:20 p.m. Approximately two minutes later, an NWS forecaster noted that the area of rotation would be crossing Hwy 54/400 right between Augusta and Leon. During that time, a caller noted that sirens were going off in Leon.  Spotters were positioned on both the Augusta and Leon sides of the storm, watching it progress toward northbound Hwy 77/54.

11:34 p.m.  A spotter called 911 advising that he could see a rotating wall cloud in the storm from his position approximately 7 miles south of El Dorado along Hwy 77. No funnels or tornadoes were seen at that point.

11:37 p.m.  The NWS informed the county that they were no longer seeing the same tight rotation on radar that they saw earlier.

11:48 p.m.  With the disappearing rotation on radar, the NWS canceled the Tornado Warning for Butler County. About that same time, a spotter with eyes on the storm was also able to confirm that the low-hanging “stuff” under the storm was no longer rotating. A Severe Thunderstorm Warning was issued in place of the Tornado Warning as there was still a chance for straight-line winds as the storm moved towards El Dorado.
 
(Click HERE to see a rough visual mock-up of this timeline, based on the most current information we have.)

ALL THE STUFF THAT MAKES NOISE

What made Tuesday night confusing (and concerning) for some citizens was that some information sources were telling them they were in trouble, while other sources/noise-makers weren’t going off at all. So which was correct?

First, storm sirens:  in our county, storm sirens are sounded as soon as a community falls within the boundaries of a Tornado Warning polygon.  Note that our local National Weather Service is really good about stretching the “upstream” end of the warning boxes to capture and prepare communities anticipated to be in the path (not just immediately threatened communities).  So, Tuesday night the sirens were sounds for all areas that fell within the warning polygon.

Second, NOAA weather radios: these go off any time a warning is issued anywhere within the county borders. They can’t be narrowed down to match polygons, so even those folks outside of the impact heard about the Tornado Warning if they had a weather radio.

WEA cell phone alerts:  this newer technology (that produces those squealing alerts and pop-up banners on your cell phone lock screens) is great in that it can narrow things down much tighter to your location. It grabs your current location, your closest cell phone tower’s location and the boundaries of the warning polygon to determine if you should get alerted.  However, it has some limitations, too. Sometimes, a cell tower’s coverage area overlaps both warned and non-warned areas.  Depending on how the cell provider processes the warning information, when the phones “tied” to that tower are alerted, it can potentially alert people who are not actively threatened. It’s still more precise than a weather radio, but not 100% spot-on.


Sorting through the barrage of information that can roll in during a storm can be overwhelming, but remember that you can never go wrong by taking shelter.  Better to take action and find out later that you WEREN’T in the affected area than to not act and find out the hard way that you were!



Taught by EMA
Taught by EMA
N of 120th on Boyer__2