This blog post is a version of an article that appeared in the April, 2015 issue of “Allen County HamNews” and is used here with permission of the author (me).

During a severe weather seminar in DuPage County, Ill. March 14, storm chaser and amateur meteorologist Skip Talbot pointed out that a horseshoe shape in a supercell thunderstorm’s updraft base is often visible before the storm forms a tornado (see figures one and two). Talbot said that this feature is a more reliable indicator of a potential tornado than is the formation of a wall cloud, which does not always happen before a tornado forms.

Talbot’s presentation was one of several during the annual, day-long Severe Weather Seminar hosted in a western suburb of Chicago by the DuPage County Office of Homeland Security and Emergency Management.

Talbot’s presentation was titled, “Anticipating Tornadoes in Visual Clues,” and focused primarily on tornado-producing supercell thunderstorms. Fortunately, we don’t often see supercells in northern Indiana but all spotters need to know what to look for when those huge storms do arrive.

How big is a supercell?

Speaking of huge, Talbot cleverly superimposed a radar base-reflectivity image of a Plains supercell over a map of the Chicago area. This provided a clear idea of the scale of such storms (see Figure 3).

Tornado red flags

Talbot also provided a valuable list of “tornado red flags:”

• Rain moving rapidly from left to right (as viewed from beyond the right side a supercell)
• A sudden surge of wind flowing into the supercell
• A sudden barrage of positive cloud-to-ground lightning.

While none of the above meet the SKYWARN storm spotter reporting criteria, they can help spotters remain alert to the strong possibility that a storm is about to produce something reportable!

Storm spotting squall lines (QLCS’)

Meteorologist Ben Deubelbeiss of the Chicago National Weather Service (NWS) office did a presentation that focused on “squall line” thunderstorms, to which meteorologists refer as quasi-linear convective systems (QLCS’). These types of storms are quite common here in northern Indiana, especially during the summer.

A QLCS is a line of thunderstorms that can extend hundreds of miles and persist for hours. It typically produces straight-line wind damage. Shelf clouds form along the leading edges of many QLCS’. Deubelbeiss pointed out that the bottoms of shelf clouds often contain a great deal of turbulence that results in many false reports of funnel clouds (See Figure 4). As trained storm spotters, we must guard against getting fooled by that turbulence.

Deubelbeiss also offered some important comparisons between QLCS’ and supercell thunderstorms. One relates to where the action is. In a supercell, our attention is at the right, rear portion of the storm, where tornado formation is most likely. But with a QLCS, “worst is first” as Deubelbeiss put it. The heaviest wind, occasional weak, short-lived “spin up” tornadoes and damage occur along the leading edge of a QLCS, followed by heavy rain.

Deubelbeiss also made an important point about spotter location. We’ve long been told that the best place to view supercell thunderstorms is where the storm’s heavy rain and hail are to our right and updraft is to our left (typically southeast of the storm). But where should we be when a QLCS approaches? Deubelbeiss strongly advises taking shelter in a building before the leading edge arrives, putting as many walls as possible between us and the outdoors. He reminded spotters that QLCS’ can have storm motion of more than 60 mph. He suggested waiting until the wind dies down to look outside for wind damage to report.

Technology for storm spotters

College of DuPage meteorology professor Dr. Victor Gensini provided an informative presentation, “Technology and Software for Spotter and Emergency Personnel.”

Among his recommendations was the GRLevel3 radar software available for PCs for a one-time fee of $79.95. The latest version is available for download at www.grlevelx.com/grlevel3_2/. GRLevel3 displays live and archive NEXRAD Level III data. It displays high resolution base products, dual polarization products, and derived products along with local storm reports, severe weather warnings, the positions of spotters who are registered with SpotterNetwork.org and other data.

For mobile devices, such as smartphones and tablets, Gensini recommended Radarscope (for iOS and Android) and PYKL3 (for Android only). You can find information about Radarscope at www.radarscope.tv and PYKL3 at www.pykl3radar.com. Like GRLevel3, both products integrate with SpotterNetwork.org.

Another valuable resource for spotters – especially the serious “weather geeks” among us – is a Web page maintained by the College of DuPage meteorology department (weather.cod.edu). The “Weather Analysis Tools” menu of that page offers a wide range of nationwide data, including surface maps, upper air maps, upper air soundings, satellite and radar data, numerical model data, etc.

Late season start

Finally, a note about complacency. The severe weather season nationwide got off to a late start this year, without a tornado reported anywhere in the country until March 25. Meteorologist Greg Carbin of the NWS Storm Prediction Center advised the spotters at the DuPage County seminar that climatologically speaking, severe weather someplace in the continental United States is likely to increase through the month of April. Remember also that in the 37-county area served by the northern Indiana NWS office, tornadoes are nearly twice as likely in April as in March, 1.8 times as likely in May as in April, and 1.7 times as likely in June (our peak tornado month) as in May.

Similarly, in the northern Indiana NWS area, severe thunderstorm winds (58 mph or stronger) are nearly 2.5 times as likely in April as in March, three times as likely in May as in April and nearly twice as likely in June (also our peak severe thunderstorm month) as in May.

So, don’t let the late start to the severe weather season fool you. As we get closer June, it becomes much more likely that our area will see severe weather and SKYWARN spotter activation. Be ready!

The National Weather Service (NWS) issued a simulated tornado warning this morning for the entire state of Indiana, but not all communication channels activated.

In an earlier blog post, I advised readers that if they don’t receive the test warnings today (another one is scheduled for 7:35 p.m. EDT), that could be an indication that they’d miss a real tornado warning at the same time of day.

This turns out not to be the case!

I apparently misunderstood information from the NWS and incorrectly believed that today’s test tornado warnings would activate the entire warning system, including Wireless Emergency Alerts (WEA), smartphone apps, text message systems, etc.

The morning test, however, apparently activated only NOAA Weather Radios and the Emergency Alert System (local broadcast radio and TV). The morning test did not trigger WEA or other warning systems.

So, if you didn’t receive the test this morning, it might be because you have inadequate access to warning information, or the incomplete nature of the test might be the only reason.

See an important update to this story!

The National Weather Service will issue two test tornado warnings today; one at 10:15 a.m. EDT and another at 7:35 p.m. EDT. The NWS will use the same procedures and technology it uses for real tornado warnings.

If the test times pass without you becoming aware of the tests, that very likely means that if the NWS issues a real tornado warning at that time a weekday, you might not get the warning.

Not knowing about a tornado warning could cost you your life!

So, make a mental note today to think about this at around 8 p.m. tonight. If you realize you missed either of today’s tests, take steps to improve your ability to receive weather warnings. I blogged about ways to do that last year. Here’s a link to that blog post.

Today’s test will help public officials know whether all systems are working correctly. But perhaps more important will be any gaps the tests demonstrate in your personal severe-weather preparedness.

See an important update to this story!

If you’re in Indiana tomorrow and don’t hear a tornado warning, be concerned

If you’re in Indiana, your smartphone might make an annoying noise twice tomorrow. Your NOAA weather radio should beep at you. You might hear outdoor warning sirens. That’s because the National Weather Service (NWS) and other agencies will conduct a statewide test of severe weather communications systems as part of Indiana Severe Weather Preparedness Week.

The NWS will issue test tornado warnings for the entire state of Indiana twice tomorrow, once at around 10:15 a.m. EDT and again at about 7:35 p.m. EDT. The warnings will activate weather radios, Wireless Emergency Alert-equipped smartphones, etc. the same way a real tornado warning does. The only difference will be the wording of the warning, which will make clear that it’s just a test.

Unlike your weather radio and smartphone, NWS warnings do not automatically trigger outdoor warning sirens. Local emergency agencies control the sirens manually. Many communities will sound their sirens during the tests but some might not participate in the tests. For example, during a previous year’s test, Allen County, Indiana officials decided not to activate the county’s outdoor warning sirens because skies were cloudy that day.

Whether officials activate outdoor warning sirens, however, is a bit of a moot point, because you’ll probably be indoors when the tests occur and very, very few people live where they can hear outdoor warning sirens indoors.

So, if by 8 p.m. tomorrow, you realize you never knew when the warning tests happened, that’s a good sign that you need to improve your ability to receive warnings sometime between now and the arrival of severe weather season (which is just around the corner)!

It’s “only” a thunderstorm warning? Really?

“It’s only a thunderstorm warning.” Have you ever said that? Have you ever heard anyone say it?

Complacency about severe thunderstorms is dangerous but common. Why is it dangerous? Non-tornadic thunderstorm winds killed two people in northern Indiana last year. Throughout Indiana, they killed 32 people from 1990 to 2014 (see graph above). Non-tornadic (“straight line”) severe thunderstorm winds killed all 32. Tornadoes were not involved in any of those deaths.

If you believe you’re not in danger as long as there’s no tornado, you could be the next victim.

What might surprise you is that the winds of a severe thunderstorm can be stronger than those of a tornado, and often are. For example, an EF1 tornado on the Enhanced Fujita scale produces tornadic winds of from 86 to 100 mph. The “derecho” line of severe thunderstorms that struck northern Indiana in June of 2012 produced a measured wind gust of 90 mph at the Fort Wayne international airport. That’s stronger than the bottom end of the EF1 tornado range!

What can a 90 mph wind gust do? According to the Beaufort wind scale that storm spotters use to estimate wind speeds, 90 mph wind can do considerable and widespread damage to structures.

The northern Indiana office of National Weather Service ( NWS) issued 114 severe thunderstorm warnings in 2014. Such warnings might therefore seem quite common, which can lead to complacency. It’s important to know, however, that the NWS issues those warnings only when a storm is producing or is expected to produce either one of the following:

• Wind gusts of 58 mph or stronger
• Hail of one-inch or more in diameter

Winds of 58 mph can uproot trees and do considerable structural damage. One inch hail can be traveling at 100 mph when it hits the ground (or your house, car, or worse, your head).

So, the next time the National Weather Service issues a severe thunderstorm warning, take shelter, just as you would for a tornado warning. Don’t become the next person on the state’s tally of non-tornadic thunderstorm wind deaths!