
Alabama’s “Severe Weather Awareness Week” continues on Tuesday (but this info applies to EVERYONE and we do this again later in the month when Tennessee does theirs). Today’s topic from the NWS Huntsville office is “Lightning and Severe Thunderstorms”. Here in the Tennessee Valley, the vast majority of weather hazards we face through the year come directly from thunderstorms: lightning, flooding, damaging straight-line winds, hail, tornadoes. A storm doesn’t have to be “severe” in order to be dangerous or deadly if you’re not taking appropriate shelter. That’s because EVERY thunderstorm contains lightning, just simply by definition of what a thunderstorm is! Lightning is one of the most deadly thunderstorm hazards we face here. In fact, unless it’s a year with a major tornado outbreak or a hurricane disaster like Helene or something similar with a high fatality count, lightning will often kill more people than other type of weather hazards in our area of the country. Below, we will talk about some basic steps and info for lightning safety:



The most important thing to remember is that if you are close enough to hear thunder, you are close enough to be struck by lightning! Even if the sun is shining. Lightning bolts can often reach up to a few miles away from the storm itself. It does NOT have to be raining for you to be at risk from lightning! The basic mantra is “When Thunder Roars, Go Indoors!”. That is because your safest place to be during a thunderstorm is inside a sturdy home or building, or a car with a hard-top roof if you are caught outdoors with nowhere else to go. Stay indoors away from windows until at least 30 minutes after you hear the last rumble of thunder. If you are caught outdoors, your best bet is to head inside a sturdy structure or a hard-topped car, and only seeking shelter in a low area outside as a last resort. If that happens, crouch down and cover your head and neck with your hands similarly to how you would during a tornado, trying to make yourself one of the lowest objects around. Try to avoid metal poles, bodies of water, and tall trees… especially isolated trees. The highest percentage of lightning deaths occur either on/near water bodies and during sporting events. It is extra important to monitor the weather and have a place to seek quick shelter if a storm comes up if you are involved in these type of activities!




Not every thunderstorm is “severe”, however, and severe thunderstorms bring unique and specific hazards of their own that not all thunderstorms carry with them. In order for a storm to be classified as “severe”, it MUST be producing at least one of the following three things: straight-line wind gusts of 58 mph or greater or equivalent damage, hail to 1 inch in diameter (25 center quarter size) or larger, or a tornado (in contact with the ground, not just a funnel cloud or rotating wall cloud). Many severe thunderstorms carry a simultaneous combination of those things. Lightning does not make a storm “severe” because ALL thunderstorms have lightning. Heavy rain and flooding does not make a storm severe, and neither do dark or low-hanging scary looking clouds. The safest place to be when a severe thunderstorm approaches is inside a sturdy structure and away from windows, and preferably on the lowest-floor and away from exterior walls. This is to protect yourself as much as possible if wind blows a tree onto the home or if a window is broken because of wind-driven debris or by hailstones. These basic safety rules are also the core components of tornado safety, and severe thunderstorms can and sometimes occasionally do produce tornadoes without any advance warning, or very little advance warning… especially the quick spin-up tornadoes within lines of thunderstorms.


In order to know when you are at threat of severe thunderstorms, you must understand forecast information and the watch/warning system from the National Weather Service.
A watch means that conditions are favorable for severe weather (tornadoes or severe thunderstorms, depending on the type of watch), but it’s not necessarily happening right NOW. A watch is your cue to have your safety plan ready to go and to be paying close attention to weather information and listening for warnings. A watch is not the time to actually ACT on carrying out your plan to shelter, but if you are in a mobile home and need to leave for a sturdy structure for shelter, doing that when the watch is issued is a good idea for giving you advance time to get there before storms are bearing down on you. Keep in mind, tornadoes can sometimes happen within severe thunderstorm watches or even occasionally with no watch in place at all! You must ALWAYS be vigilant of weather conditions when severe storms are possible.
A warning is the alert to let you know to ACT IMMEDIATELY to shelter safely. Whether it’s a tornado warning or severe thunderstorm warning, it means that particular type of severe weather has either been spotted by trained spotters or detected by Doppler Radar and is an IMMEDIATE threat to your safety over the next several minutes while the warning is in effect. Go IMMEDIATELY to your safe place when a warning is issued. Remember that tornadoes, especially the quick spin-up type within thunderstorm lines, can sometimes happen when there is only a severe thunderstorm warning in place or on rare occasion, with no warning at all. These are smaller and more shallow circulations and may not always be detected in time by radar for a warning to be issued. You MUST be extra vigilant to rapidly changing weather conditions when severe storms are possible, and if something doesn’t feel or seem right, trust your instinct and shelter to play it safe. You’d only be wasting a few minutes of your time if it turns out to be no big deal.
On the occasional higher-end type severe weather day, you may hear of something called a “PDS” when referring to a watch. PDS stands for “Particularly Dangerous Situation” and is a phrase added to the wording of a tornado watch or a severe thunderstorm watch when there’s an elevated threat of higher-end type severe weather. A PDS Tornado Watch means there is a heightened threat of multiple long-tracked strong to violent (EF2 to EF5) intensity tornadoes within the watch area. A PDS Severe Thunderstorm Watch is issued for long-lived widespread wind damage events when there is a heightened threat of widespread 80-100+ mph wind gusts. These watches are infrequently issued in comparison to “regular” tornado watches and severe thunderstorm watches. Roughly 3% of all tornado watches carry the PDS wording. They’re not a guarantee of major severe weather, but they have a lower failure rate and a generally a signal of something potentially major happening. Even in our tornado-prone area of the country here in the Tennessee Valley, we usually only see one or two days out of the year with a PDS watch, and there are some years in which we don’t get one at all.

Before watches and warnings are even issued, there will often be a severe weather risk forecast for the day. These outlooks are issued by the NWS Storm Prediction Center in Norman, Oklahoma. They are a specialized national forecast office within the National Weather Service that is responsible for daily severe weather outlooks and the issuance of tornado watches and severe thunderstorm watches. When severe storms are possible, the forecasters will highlight a region in a risk level ranging from Level 1 through Level 5, the higher the number the higher the relative risk. This is specifically for threats of severe storms producing damaging winds, hail, and/or tornadoes. The risk levels are mainly driven by the risk based on number or coverage of expected severe storms, but once you get into the higher-tier risks (especially Level 4 and Level 5) intensity plays a big role as well. For instance, the Level 5 of 5 “High Risk” is a rare thing (only a couple of days out of the year in the entire United States, not just here) that is saved for widespread extreme derecho damaging wind events or major tornado outbreaks with violent (EF4-EF5) tornado potential. Keep in mind, however, that not all risk outlooks are associated with tornadoes. You can be in a Level 4 risk zone, and there not even be a tornado threat at all! It could just be driven by widespread damaging winds or hail instead. Conversely, small-scale ingredients can occasionally come together at the last minute to produce a strong tornado in a lower-end risk level when the large-scale ingredients for a higher-end type threat aren’t necessarily apparently in place. These outlooks are just general guidelines to help you prepare ahead of time for the potential for severe weather.