Thunderstorm Safety

4.5.2013 Thunderstorm Safety   Questions or Comments? Contact us at weather@thestormreport.com

We’re entering the time of year where thunderstorms will be rumbling regularly across most parts of the United States. We have already seen some large outbreaks of thunderstorms, and a few tornadoes. We thought we would give you a few simple safety tips, to protect yourself from one of nature’s most beautiful, and deadly, phenomena.

The main threats from thunderstorms are: Lightning, Hail, Straight-Line Winds, Down-Bursts, Heavy Rain and Flash floods. Thunderstorms are fairly well predicted, however their strength and speed can change rapidly. Your best initial defense is to keep tabs on your local weather forecast each morning. If thunderstorms are in the forecast, then you’ll know to be on the lookout. Every day, the Storm Prediction Center in Norman, OK issues a thunderstorm outlook, and we always mention that in our Tweets here at The Storm Report. So, we encourage you to subscribe on our home page. Having a “heads-up” to threatening weather gives you a huge advantage in preparedness.

Next, you should have a plan for safety at work, home and while driving. When big thunderstorms threaten your area, the best place to be is inside a strong structure on the ground floor. This protects you from lightning and hail. Most office buildings are not constructed on flood plains, so you should be safe from flash flooding at your workplace. It’s also a good idea to have one or two employees serve as “weather marshals”. That is, a couple of responsible people who can keep an eye on the forecasts, and NOAA weather radio for bulletins. When thunderstorms appear imminent, your Weather Marshals would check in with all employees to make sure they’re aware of the situation, and prepare them to take action on the office emergency plan.

It’s basically the same situation at home. During a thunderstorm, located yourself and your family in an enclosed room with no windows on the lowest floor of your house. This generally keeps you safe from most thunderstorm threats.

If you work outside, your best shelter would be an enclosed vehicle. (not a motorcycle or convertible car). An enclosed car or truck acts like a shield against lightning, directing the energy around the car and down into the ground. It may be scary, but it’s better protection than being outside. If you work in construction, or near lakes or rivers, be aware that flash flooding can happen very quickly, and be prepared to move to high ground when you see water rising.

Lightning is the most deadly threat from any thunderstorm. It is unpredictable and very powerful. If you’re outside playing golf or other sports, head to a substantial structure before the storm hits. And keep in mind, lightning can strike many miles away from the center of the thunderstorm. Meteorologists call this a “Bolt From The Blue”. It’s rare, but it does happen. Employ the 30/30 rule for lightning. When you see a flash of lightning, begin counting until you hear the thunder. Every five second equals roughly one mile. So if you count to ten before hearing thunder, the lightning strike was about two miles away. If you hear thunder before counting to 30, it’s time to take shelter. The other part of the 30/30 rule is to wait 30 minutes after hearing the last rumble of thunder before resuming outdoor activities.

Hail can be a threat as well, especially if large hailstones are falling and you are caught outside. There has only been one recorded fatality in history from someone being hit by a hailstone. The biggest problem is trying to drive on it; it’s like driving on marbles. So, you will want to pull over and wait out the storm, or drive extremely carefully through hail.

Flash flooding is of particular danger to people camping in the wilderness near rivers or creeks, or in dry flood beds. It’s also dangerous for drivers because of potential road wash-outs or overflow. If you’re caught outside and heavy rain begins, move immediately to higher ground. A thunderstorm can be dropping heavy rain many miles upstream, and that rushing water can cause major problems for anyone downstream. The Big Thompson Canyon flood in Colorado in the 1970s is a prime example. People many miles downstream were caught unaware, because the storm itself was miles away. Be prepared to move quickly to higher ground.

If you are driving, and come across water rushing across the road, do not attempt to cross it, even if it does not appear to be very deep. A mere 2 inches of rushing water can float a car off the road, and into a gully or ravine where you could be trapped. Or, the roadway may be ready to collapse under the weight of your vehicle, leaving you in an extremely dangerous situation. The general rule is: “Turn Around, Don’t Drown”. If water is rushing across the road in front of you, go back the way you came and avoid crossing it.

As for down-bursts and straight-line winds, in many thunderstorms wind speeds of 70 to 90 mph are possible as the storm’s gust-front crosses your location. Down-bursts happen when heated air rises up the thunderstorm updraft in large quantity. Once the moisture (and its latent heat) are condensed, the air cools rapidly and begins a long descent, picking up speed along the way. Once that cool air hits the surface, it has nowhere to go except out along the ground. Down-burst wind speeds over 100 mph have been recorded. Being in a sturdy structure will protect you from these threats.

We must emphasize that being prepared is your first, best defense. Don’t get caught unaware. Check the weather forecasts daily, and know what your area may be expecting later in the day.

In our next article, we’ll cover Tornado Safety.

Please send your questions, comments and cool weather photos to us at weather@thestormreport.com.

Tornado Ratings

4.3.2013 Tornado Ratings   Questions or Comments? Contact us at weather@thestormreport.com

Tornado

Example Of A Strong Tornado

How do we determine the power or strength of a tornado? Nowadays, when we hear about tornadoes on the news, they’re described as having a rating of EF-0 to EF-5. The “EF” part stands for “Enhanced Fujita”, for the Enhanced Fujita scale, which has been used since 2006 in the USA. Canada is set to adopt the EF Scale this year.

In 1971, a brilliant scientist named Tetsuya Theodore “Ted” Fujita invented a tornado ranking scale that rated tornadoes based on the damage they caused. His scale was designed to match closely with the Beaufort Wind Scale (long used by mariners), and the Mach speed scale. The Fujita scale was updated in 1973 to account for the length of the path, and the width of the base of each tornado. So, during the 1970s through the mid 2000s we would hear of tornadoes rated as “F-3″ for example. The scale Fujita invented estimated wind speeds of tornadoes based on the amount of damage caused on the ground, what kind of damage, and the strength of the structures that were damaged. Basically, we had to guess at tornado wind speeds because there was no real way to measure them. Originally, Fujita’s scale went from F-0 to F-12, then it was amended for general use, only going up to F-5. He did leave room for an F-6 in the original scale, which he described as an “inconceivable” tornado. This is because no one really knew the limit of their power, (and we still really don’t).

On February 1, 2006, the National Oceanic and Atmospheric Administration switched to the “Enhanced” Fujita Scale. The “EF” is basically the same as the “F” scale in structure, however it was revised to reflect better examinations of tornado damage surveys, so as to align wind speeds more closely with associated storm damage. The new “EF” scale also adds more types of structures and vegetation. It also expands degrees of damage, and better accounts for variables such as differences in construction quality.

EF-5 Tornado Damage

EF-5 Tornado Damage

Both the “F” and “EF” scales are really only a proxy for actual tornado wind speeds, based on damage after the tornado has passed. If you hear anyone talking about a tornado that is happening right now, and they call it an “EF-3″, that’s an incorrect reference. Tornadoes are only classified after the damage has been analyzed by the National Weather Service. While a tornado is happening, you can really only accurately refer to it by size or shape. Once the NWS takes a look at the damage to buildings or ground cover along the path of the tornado, they are the ones who will give it an official “EF” classification. Examples of EF-5 tornadoes would be the Greensburg, Kansas tornado of May 4, 2007 and the Joplin, Missouri tornado of May 22, 2011. To view the damage of an EF-5 tornado, one would think the area had been flattened by a nuclear blast.

Like the original “F” scale, the “EF” scale makes only estimations of the wind speed in a tornado. However, fairly accurate estimations have been made with high-speed film, and mobile radar. Several university research programs have vehicles that carry their own radar. Using two or three of these vehicles, parked at different areas around a tornado, wind speed can be estimated more accurately. Based on this new research, tornado wind speeds have actually been downgraded a little. It was once thought that some tornado wind speeds were well over 350 mph. On May 3, 1999 an F-5 tornado near Bridge Creek, Oklahoma had an estimated wind speed of 302 mph, based on radar observations.

There have been attempts to record tornado wind speeds using “probes”. These are ground-based instrument packs designed to hug the ground during high winds. The probes are packed with cameras and sensors to record close encounters with tornadoes. Engineer Tim Samaras developed a very successful type of probe four years ago. Several “close calls” have been successfully documented, but as you can imagine, it is very difficult and dangerous to get such an instrument pack directly in the path of an oncoming tornado. Right now, the safest and most reliable wind speed measurements are calculated using mobile radar. Readings by different mobile radar units are compared, and an estimate of wind speed is made by measuring the speed of debris flying around the base of the tornado, or rain circulating within the funnel.

Remember, a tornado can only get an “EF” rating by the National Weather Service, after it has occurred. And until someone comes up with an indestructible instrument pack and gets it into the middle of a tornado, we won’t know exactly how fast their wind speeds are. This is why we continue to do research into one of Nature’s most destructive forces.

Please send your questions, comments and cool weather photos to us at weather@thestormreport.com.

Weather Wise: No Fooling, Lightning Kills

4.1.2013 Lightning

Multiple Lightning Channels

Multiple Lightning Channels

Lightning is perhaps the deadliest threat from the average thunderstorm. Over the past 10 years, lightning alone has killed more people than any other hazard associated with thunderstorms. Lightning is also responsible for a great number of forest and grass land fires. Each stroke of lightning contains millions of volts of electricity, and a huge “amperage” or current. One lightning stroke can power about ten average-sized homes for about a month. Lightning heats the air around its path to about 50,000 degrees F. This cause rapid heating and expansion of the air along the lightning channel. As the air cools rapidly after the lightning stroke is over, it contracts and causes the loud bang we know as thunder.

Lightning is unpredictable and occasionally behaves in strange ways. It can destroy one object without touching another one nearby. Lightning can also strike something such as a tree, then travel across the ground shocking anyone who happens to be standing nearby. Lightning normally strikes the tallest object in the area, but not always. Occasionally a lightning stroke may branch out and make contact with several objects simultaneously. Simply based on its power and unpredictability, lightning is arguably the most dangerous threat from any thunderstorm. So, how do we protect ourselves and our property from lightning?

Stay away from metal objects and away from water, because both are good “attractors” for lightning. Tall objects like telephone poles in open fields, towers or large buildings can become likely targets. Simply put, don’t be the tallest thing around, and don’t be near the tallest thing around.

Most lightning fatalities occur outdoors, and often under or near tall trees, in or near water or on hilltops. Lightning can strike the ground up to 20 miles away from the parent thunderstorm. Based on this information, it is obvious why you need to take shelter from lightning if you happen to be engaged in outdoor activities. One reliable way to estimate your distance from a thunderstorm is the “Flash To Bang” technique. Count the number of seconds between the time you see the lightning flash and when you hear the thunder. Divide the number of seconds you count by five. Every five seconds equals about one mile. It is recommended that you should begin to seek shelter if the time between the lightning flash and the thunder is 30 seconds or less. You should not resume outdoor activities until 30 minutes after the last audible thunder. This is known as the “30/30 Rule”.

Stay off corded telephones when lightning is in your area, since the electrical discharge from lightning can travel along the telephone lines and produce fatal results. It is also recommended that you unplug sensitive electronics such as computers when lightning is expected in your area. Stay away from electrical devices and stay out of shower stalls and bathtubs, swimming pools and lakes when thunderstorms threaten. As far as we know, being on a cordless phone or a cell phone is relatively safe during a lightning episode.

The best defense in protecting yourself from lightning is to plan ahead and avoid being caught in a vulnerable position, (such as outdoors). Check the weather forecasts prior to venturing outside, especially if you are traveling into mountainous or open terrain where there is little or no shelter. Plan outdoor activities for early in the day before thunderstorms develop.

If thunderstorms threaten, seek shelter in a building or in an enclosed metal roof vehicle, making sure all windows are closed. Never seek shelter under an isolated tree or small group of trees. If you are in a heavily forested area, take shelter in a low spot and away from the taller trees. However, avoid areas which could be prone to flash flooding. If you are caught in the open, do not lie flat on the ground. Lying flat exposes more of your body to contact with the ground, and the possibility of absorbing current flowing along the ground. Instead, squat low to the ground, clasp your hands around your knees and put your chin to your chest. Make yourself the smallest target possible, and avoid becoming a human lightning rod.

Don’t forget to send us those cool weather photos you have hiding in your camera! You can upload them to us by email at weather@thestormreport.com.

“Weather Wise” is a feature of The Storm Report, especially designed for you, so please participate with us. It’s the only place on the web where you get to talk with real Meteorologists about how weather works.

Weather Wise: Winter Storms

Winter Storm Formation

Winter Storm Basics

3.29.2013 Winter Storms Still Possible

It’s Spring by the calendar, however winter storms are still possible, especially in the Rockies, Midwest and Northeast USA. In fact, some of the worst winter storms on record have happened in March and April. So, what are the makings of a winter storm? Our diagram shows a simplified version of the basics. There are several main ingredients that must be present for a winter storm to get cranked up: A strong area of low pressure, preceded by a warm front, and trailed by a cold front. High pressure to the northwest of the low presents a clockwise flow of cold air from the north, while counter-clockwise flow around the low pulls in warm, moist air from the south.

These main ingredients form the building blocks of a winter storm. The strength (or intensity) of the low pressure area is very important, because the stronger it is, the more capable it is of generating strong winds, and pulling in a southerly air flow. The other very important factor is an ample supply of moist air in close proximity to the low. This air gets pulled in and the moisture is converted to precipitation, possibly in a wide variety of forms depending on the structure of the storm. Snow, rain, freezing rain, sleet and even hail are possible in winter storms. Looking at our diagram, you can see a warm area out ahead of the warm front. This is where we’ll usually see rain and even thunderstorms form up as the storm approaches. Depending on your relative position to the storm, you may experience mostly rain, or mostly snow. If the temperature and humidity at the mid-levels of the atmosphere are adequately cold and wet, heavy precipitation may fall.

Every winter storm differs slightly in the alignment of all the various elements. When they come together just right (acting with the local terrain) we can get a storm that will drop snow which can be measured in feet instead of inches. The Sierra and Cascade mountains are an example of this, along with the eastern slopes of the Rockies, and the Appalachian Range. Winter storms can sometimes intensify in these areas because of the mountainous terrain, higher (and colder) elevation and something called “up slope” flow. This is where warm, moist air is pushed against a mountain range and forced to rise, causing it to cool and condense the moisture it contains into snow. There are cases of winter storms leaving 7 or 8 feet of snow (or higher).

Another factor to consider with winter storms is wind. This obviously causes drifting snow, bad driving conditions and temperatures that feel colder than they actually are. The wind is dependent upon the strength of the low pressure center. The lower the pressure, the stronger the wind it will generate. Wind is basically air flowing from an area of high pressure, to low. So if we have a very strong low next to an equally strong high, the pressure gradient between the two will form the atmospheric equivalent of a “cliff”.  And this can cause extremely strong wind.

Winter storms are not the same as Blizzards, although they can occur together. Blizzard conditions are partly determined by the strength of the wind. In order for a Blizzard Warning to be issued, there must be significant blowing and drifting snow, (but not necessarily falling snow), and sustained winds of 35 mph or greater. Visibility must be 1/4 of a mile or less.

So, while Spring may be on your mind, there is still a chance we will have a few more winter storms to deal with. Fortunately by this time of year, temperatures usually warm up quickly following a “Spring Winter Storm”, (no, that’s not an official term). This is actually a potential hazard, because quick snow-melt can cause flooding.

Don’t forget to send us those cool weather photos you have hiding in your camera! You can upload them to us by email at weather@thestormreport.com.

“Weather Wise” is a feature of The Storm Report, especially designed for you, so please participate with us. It’s the only place on the web where you get to talk with real Meteorologists about how weather works.

Welcome to “Weather Wise” – Our New Weather Info Feature

Wind VaneWelcome to our new feature, “Weather”Wise”. This is where The Storm Report will give you great information about how the weather works. Please let me introduce myself, first off. My name is Steve Hamilton, and I am one of the Meteorologists here at The Storm Report. I’m certified by the American Meteorological Association, and weather has been my passion since I was a little kid. I’m also a professional Storm Chaser/Spotter, and an Observer for the National Weather Service.

The goal of “Weather Wise” is to help you get familiarized with weather, and the processes that make it work. We’ll even give you safety tips so you and your family won’t be caught unprepared in severe weather situations.
Best of all, YOU get to participate! Here’s how:

  • Suggest topics for us to talk about.
  • Disagree with us, or invite debate on any topic.
  • You’re welcome to ask any questions you want about our topics or answers.
  • We invite you to send us any weather photos you’re really proud of.
  • We’ll occasionally ask YOU questions, and we’ll post your answer, (if it’s OK with you).
  • We will recommend ways for you and your kids to get involved in weather observation and educational programs.

We promise to give you explanations that are down-to-earth, along with cool graphics that will give you a visual idea of what we’re talking about. “Weather Wise” is a perfect little environment where we can all gather as friends and talk about weather. Plain and simple.

3.27.2013 Severe Weather Watches and Warnings

We’re getting to that time of year where we’ll be hearing a lot about tornadoes, flash floods, hail, strong winds and lightning. Springtime is severe thunderstorm time across most of the USA. You often hear on Radio and TV broadcasts about severe weather “Watches” and “Warnings”. So, what’s the difference?

“Watches” are issued by the Storm Prediction Center in Norman, Oklahoma. The SPC is a division of the National Oceanic and Atmospheric Administration (NOAA). They are usually posted for a wide area of a state, or several states. Simply stated, a “Watch” is just that… we are “watching” for severe weather to develop in the watch area. Watch areas are posted for places where conditions are favorable for certain types of severe weather: Winter storms, tornadoes, hurricanes, severe thunderstorms, blizzards, freezing conditions. Watches are usually posted for a period of time lasting several hours or several days. If your home or town is under a severe weather “Watch”, you should watch the sky, be alert for rapidly-changing weather conditions, and prepare your safety plan in case dangerous weather develops. It’s not a reason to go hide in the basement, but it is cause for being alert and paying attention to weather updates.

“Warnings” are issued by your local National Weather Service office, not by Radio or TV stations. The only organization authorized to issue a “Warning” is the National Weather Service. Warnings are issued for a specific area or town that is under the threat of imminent severe weather. For example, a “Tornado Watch” might cover half of Ohio, but a “Warning” might just cover the city of Dayton. When you hear on NOAA Weather Radio, or local Radio or TV about a Warning for your area, that’s the time to take action and seek shelter. Put your emergency plan into effect and get to a safe place. (In our next report we’ll tell you about how to prepare an emergency plan for any type of severe weather.)

Sorting out Watches from Warnings can be very confusing, especially when there is a lot going on in your area. We think the simple explanation above will help you keep it straight. Please send any questions or comments to us by clicking HERE, and we will get right back to you. And don’t forget to send us those cool weather photos you have hiding in your camera! You can upload them to us by email at weather@thestormreport.com.

“Weather Wise” is a feature especially designed for you, so please get into the act and participate with us. It’s practically the only service on the web where you get to talk with actual Meteorologists about what makes weather tick!

-Steve Hamilton, Meteorologist. The Storm Report