Tag Archives: severe thunderstorm

SKYWARN, Weather

Tornado strikes NW Allen County July 29

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Path of a tornado that touched down just west of the Eel River Golf Course south of Churubusco and tracked rapidly east southeast, crossing US 33 before dissipating in a corn field west of Chase Road. NWS image.

The National Weather Service Northern Indiana weather forecast office (IWX) announced August 2 that it found evidence that a tornado did damage in eastern Whitley County and northwestern Allen County, Indiana at approximately 2:30 a.m. July 29.

“But wait,” you might say, “I never heard about a tornado warning for Allen County that day!” That’s because IWX didn’t issue a tornado warning for this storm. At the time of the tornado, however, a severe thunderstorm warning was in effect that included the words, “tornado possible.”

Most severe thunderstorm warnings do not automatically create alerts on your cell phone.

It’s not unusual for the kind of storm we had Saturday morning (a bowing “squall line”) to spawn weak tornados that appear and disappear before the National Weather Service can issue a warning. That’s why, when they warn us of a severe thunderstorm that could contain such tornados, they mention that a tornado is possible.

Weather radar loop slowing the bowing squall line that moved across Indiana early July 29.

It’s also one reason that it’s so important to know about and react appropriately to severe thunderstorm warnings, including those the National Weather Service issues in the middle of the night, when you’re sleeping. But that requires extra effort on your part, because most severe thunderstorm warnings do not automatically create alerts on your cell phone.

If you’ve ever been someplace covered by a tornado warning, you probably received a Wireless Emergency Alert (WEA) on your phone, even if you never installed a weather app. That’s because all modern smartphones come with WEAs enabled and all tornado warnings prompt WEAs.

The only severe thunderstorm warnings that trigger WEAs, however, are those in which the National Weather Service includes a “destructive” damage threat “tag.” They do that for storms that have either hail that’s at least 2.75 inches in diameter (baseball-sized) and/or 80 mph straight-line thunderstorm winds. According to Saturday morning’s severe thunderstorm warning, meteorologists expected winds of up to 60 mph and no large hail. That warning therefore did not trigger a WEA.

So, how can you know if a storm like Saturday’s is headed toward your home in the middle of the night, while you’re asleep? I know of two really good ways:

  1. Buy a weather alert radio and keep it near enough to your bedroom to wake you.
  2. Install a weather alert app, like Storm Shield, and configure it to alert you to severe thunderstorm warnings.

When the NWS issues a severe thunderstorm warning for your location, the best way to be safe is to do the same thing you’d do in a tornado warning. Move to the most interior room on the lowest level of your house. This will provide the best protection from a brief tornado, like the one that touched down July 29 and from straight-line thunderstorm winds dropping a tree limb on your house, which is what killed a woman in Ohio City, Ohio July 20.

SKYWARN, Weather

High probability of very severe weather in Indiana today

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Probabilities of damaging, straight-line winds or gusts.

Damaging, straight-line thunderstorm winds — the kind that can knock down whole trees and cause widespread power outages and road blockages — are likely in Indiana this afternoon and evening, especially in extreme southwestern counties (shaded purple in the map above), according to a convective outlook that the National Weather Service (NWS) Storm Prediction Center issued at 9 a.m. ET today.

The 45% probability indicated on the map above compares to “normal” or “average” probability for this time of year of only 1%, acccording to climatology (weather history) data from the National Severe Storms Laboratory.

And in a large part of southern Indiana (shaded gray on the map below), any severe thundertorms that form could create wind gusts of 75 mph or stronger. That’s the same as a category one hurricane. The probability of that happening is 10 percent, or approximately 100 times the climatology norm of 0.1%

Probability of gusts of 75 mph or stronger.

Tornadoes are also possible throughout Indiana and once again, the greatest risk is in the southwest (shaded yellow on the map below), where the probability is 10%, or about 25 times the climatology norm. The 5% probability in the rest of the state is about 12.5 times the norm for this time of year. So even though 10 and five are small numbers, they’re important in this context.

Probability of a tornado.

Any tornadoes that form in southwestern Indiana (shaded gray on the map below) have a 10% probability of doing damage rated EF-2 or higher on the enhanced Fujitsu scale. That’s about 50 times the climatology norm.

Probability of a significant tornado doing damange of EF-2 or greater.

The entire state also has a risk of one-inch or larger hail, but as the map below indicates, the hail risk is lower than the straight-line wind risk.

Probability of one-inch or larger hail.

It’s important for anyone in Indiana to have multiple ways to receive severe thunderstorm and tornado warnings today. Unfortunately, the Indianapolis NWS office reported this morning that three NOAA Weather Radio transmitters in southern Indiana were inoperative.

NWS Indianapolis tweet about inopertive weather radio transmitters

Update: The Indianapolis NWS office reported at 11:44 a.m. ET that all three transmitters had returned to service.

That makes multiple alerting methods even more important. People in that area shold probably keep a TV on, turned up, and tuned to a local station (i.e., not ESPN or Netflix!). Another idea is to install the free FEMA app on smartphones.

If your phone and other rechargeable devices are not fully charged, start charging them now.

If you’re a volunteer Skywarn storm spotter, prepare for activation this afternoon or evening.

SKYWARN

Top 5 ways to get severe weather warnings

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It’s hard to protect yourself and your family from tornados, damaging straight-line severe thunderstorm winds, or large hail, if you don’t know that the National Weather Service has issued a tornado or severe thunderstorm warning for your location.

So, here’s my list of the best ways to get tornado, severe thunderstorm and flash flood warnings.

Continue reading →
SKYWARN

Half of Indiana has marginal risk of severe storms today

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Indiana map showing (Left) Risk of severe weather between 9 a.m. EDT today and 8 a.m. EDT tomorrow. Dark green shading: Marginal risk. Light green: thunderstorms possible but none expected to be severe. (Center) Probability of damaging straight-line thunderstorm winds of 58 mph or stronger within 25 miles of any point. Brown: 5% (marginal risk). Unshaded: Less than 5%. (Right) Probability of hail of one inch diameter or larger within 25 miles of any point. Brown: 5% (marginal risk). Unshaded: Less than 5%. Source: SPC "Day 1 Convective Outlook" issued at 8:52 a.m. EDT.
(Left) Risk of severe weather between 9 a.m. EDT today and 8 a.m. EDT tomorrow. Dark green shading: Marginal risk. Light green: thunderstorms possible but none expected to be severe. (Center) Probability of damaging straight-line thunderstorm winds of 58 mph or stronger within 25 miles of any point. Brown: 5% (marginal risk). Unshaded: Less than 5%. (Right) Probability of hail of one inch or more in diameter within 25 miles of any point. Brown: 5% (marginal risk). Unshaded: Less than 5%. Source: SPC “Day 1 Convective Outlook” issued at 8:52 a.m. EDT. Click the image for a larger version.

Half of Indiana (shaded in dark green on the map, above-left) has a marginal risk of severe thunderstorms between 9 a.m. EDT today and 8 a.m. EDT tomorrow, according to the “Day 1 Convective Outlook” that the National Weather Service Storm Prediction Center (SPC) issued at 8:52 a.m.

The primary risks are damaging straight-line thunderstorm winds of 58 mph or stronger and hail of one inch or more in diameter. The probability of either occurring within 25 miles of any point in the slight risk area is five percent.

The normal wind probability for any May 12 is about two percent, according to climatology data from the National Severe Storms Laboratory. Today’s probability, therefore, is roughly twice the normal probability for this date.

The normal hail probability for any May 12 is about one percent, so today’s probability is roughly five times normal.

There’s no reason to be alarmed by a marginal risk, but if you live in that half of Indiana, it’s wise to remain weather-aware today, especially if you’ll be involved in any outdoor activities (e.g. baseball games, etc.). Remember that all thunderstorms, severe or not, bring lightning, which kills people who are outdoors.

The SPC plans to update its outlook for today by 12:30 p.m. EDT.

SKYWARN

Know anyone who’s still confused by watch vs. warning?

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Wizard of Oz witch tornado watch warning meme
Meme creator unknown

The U.S. National Weather Service has been issuing tornado and severe thunderstorm watches and warnings since 1965. More than 50 years later, however, people still fail to fully understand the difference between a watch and a warning. You probably know some of them, I certainly do.

As my contribution to the second day of Indiana’s Severe Weather Preparedness Week 2016, I’ve written this blog to share with your friends and family members who remain confused.

A watch is essentially a forecast

Map showing tornado watch for a large part of Indiana and Michigan for 11:20 a.m. to 8 p.m. Nov. 17, 2013.
Map showing tornado watch for a large part of Indiana and Michigan for 11:20 a.m. to 8 p.m. Nov. 17, 2013.

In fact, before 1965, the NWS called what we now know as “tornado watches” “tornado forecasts.” A tornado watch indicates the possibility of tornadoes forming, just as a rain forecast indicates the probability of rain. Similarly, a severe thunderstorm watch indicates the possibility of severe thunderstorms forming. A watch does not mean these things are already happening, it means they could happen.

Like a forecast, a watch covers a period of many hours and usually covers a large area of at least several counties, if not several states. We should watch for possible dangerous weather in the near future.

A warning is an indication of immediate danger

Polygon indicating the area covered by a tornado warning for the Kokomo, Indiana area Nov. 17, 2013.
Polygon indicating the area covered by a tornado warning for the Kokomo, Indiana area from 3:17 p.m. to 3:45 p.m. Nov. 17, 2013. Click the image to see a larger version.

It’s a call to take shelter now, because the tornado or severe thunderstorm is already happening. Depending on where you are, you might only have couple of minutes to protect yourself and your family. Or, you might have 10 or 15 minutes, if you’re at the far edge of the “warning polygon.” If you want to survive a tornado or a severe thunderstorm, don’t waste time seeking more information. When a warning comes out, take shelter immediately.

Because dangerous weather has already formed and is on its way, a warning usually covers a period of less than an hour and a small area that’s sometimes smaller than a county. The time to watch is over. It’s now time to heed the warning and take shelter.

Want even more lead time?

If you’re really interested in weather, or want to know even earlier whether severe weather is possible, there are two other NWS products to check out.

The NWS Storm Prediction Center (SPC) usually issues a “mesoscale discussion” before it issues a watch. This product lets you know that the SPC is thinking about (or planning to) issue a watch, the geographical area of concern and the reasons. Some of the text of a mesoscale discussion can get pretty technical, but anyone can figure out from this product whether a watch is likely to be issued. If any mesoscale discussions are in effect, you can find them on the SPC website.

For even more lead time, the SPC issues “convective outlooks” that indicate the amount of risk of severe weather as much as eight days in advance. You can also find these products on the SPC website.

SKYWARN

Circus tent tragedy was preventable — NWS had issued a warning

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A father and his daughter died when a circus tent collapsed during a severe thunderstorm in New Hampshire. Aug. 3, 2015
A father and his daughter died when a circus tent collapsed during a severe thunderstorm in New Hampshire. (Sebastian Fuentes photo)

It appears that a severe thunderstorm tragically killed a father and his daughter yesterday, while they were inside a circus tent at a Lancaster, N.H. fairground.

The New Hampshire Union Leader reported that the tent collapsed at approximately 5:46 p.m. EDT. The collapse injured an additional 15 people, according to the newspaper.

This reminds me of another time that a severe thunderstorm killed people at an outdoor event: The 2011 Indiana State Fair.

Both tragedies could have been prevented. If the people at the circus had been aware of and heeded a severe thunderstorm warning that the local National Weather Service issued at 5:23 p.m., they would have had more than 20 minutes to seek shelter before the tent collapsed.

The yellow polygon shows the area of New Hampshire for which the National Weather Service issued a severe thunderstorm warning before the circus tent collapsed.
The yellow polygon shows the New Hampshire area for which the National Weather Service issued a severe thunderstorm warning before the circus tent collapsed. Click the image for a larger version.

Typically, a storm that warrants a severe thunderstorm warning has straight-line winds or gusts of 58 mph or stronger.  A big tent is the last place I’d want to be when winds of that speed hit.

We don’t know yet whether anyone at the circus knew about the warning. Severe thunderstorm warnings don’t trigger Wireless Emergency Alerts on smartphones the way tornado warnings do. Likewise, most localities don’t activate outdoor warning sirens for severe thunderstorm warnings.

Weather alert radios – which are available for as little as $30 – certainly sounded off when the National Weather Service issued the warning for Lancaster.  Very few people, however, carry portable weather alert radios with them to a circus.

Still, the entire audience could have known about the coming storm and taken shelter in fairgrounds buildings, or at least in their cars, had a circus staff member had been monitoring a weather radio and had the circus implemented an emergency weather plan.

Every organization that stages any kind of outdoor event has a responsibility to its participants, spectators, etc. to know about and respond appropriately to all weather warnings.

That includes circuses, state and county fairs, sports stadiums, etc.

In New Hampshire, the following chain of events would very likely have prevented all the injuries and deaths:

  1. Circus staff members program a weather alert radio for the county in which the circus is located.
  2. A circus staff member (e.g. ticket office staff) remains within earshot of the weather radio.
  3. Upon hearing the severe thunderstorm warning, a circus staff member alerts a member of management.
  4. Circus management makes an announcement over the circus public address system, in which they ask all patrons to seek shelter and provide advice on where to do so.

Of course, awareness of a severe thunderstorm warning is only part of the solution. People must also understand how dangerous a severe thunderstorm is, so they take shelter just as they would during a tornado warning. But that’s a topic for a different blog post.

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