DISCUSSION: In the wake of what is now a departing Tropical Storm Chris after formally being Hurricane Chris over the past 24 hours or so, there still do remain one or two concerns along north-south oriented beaches along the Mid-Atlantic and the Northeast United States. Although it would now seem to appear that the primary threat this latest offshore tropical cyclone is now well offshore, there is still a very legitimate coastal concern or two which is on the mind of many. This is the threat of both rip currents as well as mild-to-moderate coastal beach erosion. Even when a hurricane or tropical storm is tens to hundreds of miles offshore from a given coastline, there is always a legitimate threat for there to be a prominent and persistent ocean swell and wave action along the chance even far away from the storm.
This is a result of the fact that closer to the storm’s immediate proximity there are much larger waves which are generated by the stronger wind’s much closer to the storm’s center of circulation. Hence, as these larger waves continue to move away from the center of what is now (as of this evening) Tropical Storm Chris, they will gradually begin to lose some energy and magnitude with increasing distance from Chris, but not nearly enough to eliminate all the potential and kinetic energy from these incoming waves. To clarify, potential energy with wave action is referring to the net amount of energy which may end up having the ability to reach a given coastline. On the flip side, kinetic energy with wave action refers to the net amount of energy which does ultimately reach a given coastline during some given period. Further, such wave action reaching a given coastline can also induce substantial amounts of regional coastal beach erosion. This a result of the unrelenting wave action acting to quite literally “tear up” coastlines and remove a lot of sand from both parts of the inner coastal shelf, beaches, and critical protective sand dunes which help to more effectively protect coastal communities.
Lastly, tropical storms and/or hurricanes can also induce what are most commonly referred to as rip currents along coastal beaches normal to the axis of the incoming wave action. Rip currents occur as a result of strong incoming wave action racing back out to sea and creating locally strong undertows in the vicinity of the outgoing ocean water from the aforementioned incoming wave action. This is visually reflected the graphic attached above courtesy of the NOAA National Weather Service network.
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© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: As the Northern Hemisphere heads deeper in the Summer of 2018, it is no surprise that thunderstorm occurrence frequency is increasing along with corresponding rising average day-time high temperatures across many parts of the world. More specifically, across the South-Central, Central, and North-Central Plains states of the United States in North America, there is no question that thunderstorm activity frequency experiences a substantial increase. Having said that, one of nature’s greatest natural dangers is the well-known lightning strike.
With severe weather, many people across the United States and many other parts of the world know first-hand about how dangerous lightning can be. First off, it is important to note that an average lightning strike can have a maximum instantaneous temperature of around 53,000 degrees Fahrenheit as opposed to the surface of Earth’s Sun which has a temperature of around 10,000 degrees Fahrenheit. Second, lightning which is most commonly found directly in association with strong to severe thunderstorms in places all over the world can also sometimes strike many miles away from a given thunderstorm cell. Sometimes the reasons for such a displaced electrical discharge away from a given thunderstorm are not perfectly clear, but, the bottom line here is that it can and does happen at times. Thus, when you may have the curiosity during this Summer to go outside and watch an incoming thunderstorm, remember that lightning can strike both unexpectedly and unpredictably in many cases. Hence, always be sure to have the utmost respect for the natural power of thunderstorms during any season regardless of when they may occur.
Remember the old phrase from the NOAA National Weather Service network: “When thunder roars, go indoors.” It may initially seem comical at the face of that phrase, but at some point in your life, this may just end up being a phrase which separates you from encountering a potentially life-threatening experience due to a run-in with one of Mother Nature’s most intense weather phenomena on the planet. Remember that you can always replace a memory card in a camera for the next thunderstorm event, but you can never replace a life.
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© 2018 Meteorologist Jordan Rabinowitz
Analyzing the entirety of the atmosphere is vital in studying weather, understanding synoptic systems, and ultimately, providing forecasts. However, when studying smaller mesoscale phenomena, the atmospheric boundary layer (ABL) is the way to go. The ABL is the layer of the atmosphere which is directly influenced by the surface of the earth through exchanges in energy, moisture, and turbulence. To give an idea of its size, the troposphere (where almost all weather occurs) in mid-latitude regions is on average 12 miles high, but the ABL is only about a tenth of that. Two subsets of the ABL, each with their own distinct processes and functions, will be investigated in depth to understand its importance in the weather world.
The Land Boundary Layer
The boundary layer over land, also known as the land boundary layer (LBL) is one that almost everyone sees and interacts with every day. This boundary layer forms by growth with the diurnal cycle. The sun heats up the ground which in turn destabilizes the lower part of the atmosphere, generating dry convection. This convection mixes the air vertically elevating the boundary layer as it does so. In addition to heightening the LBL, this creates low level turbulence.
The height of the boundary layer depends on many different weather processes that occur daily, not just convection on a sunny day. For example, fronts, deep moist convection, precipitation, temperature and moisture advection, amongst others can significantly impact the height of the LBL. For a typical summer sunny day, with no significant weather features in the area, heights of the LBL extend up about 1-2 km with extreme cases such as in desert environments up to 4-5 km.
How do we know where to spot the boundary layer on a typical day? There are a few ways to go about this. One visual way is to look at the sky. Fair weather cumulus clouds, if present, will typically give an estimate of the LBL’s elevation. Below these clouds lies the mixing of the air from convection and hence a turbulent environment of varying intensities. Above these clouds exists an inversion, essentially the best way to pick out the LBL depth.
Another method utilizes a vertical profile of the atmosphere. In the sounding below from North Platte Regional Airport on the 27th of June 2018 at 00Z, the boundary layer is shown to be around 1.2 km above ground level (AGL) (the surface elevation is about 850 m, meaning the boundary layer is from the surface to 1.2 km above this). The temperature around this height shows a distinct increase for the next few hundred meters while the moisture significantly drops off above this increase in temperature. What this physically signifies is the almost uniform air below the inversion because of the mixing from thermals, shown by the unvarying moisture throughout the LBL. The widely varying moisture above this level is a testament to the mixing not being present and hence the boundary layer ceasing to exist at and above, in this case, 1.2 km AGL.
The LBL and its processes are very important to the Plains and Midwest United States, especially during the nighttime hours. Essentially a nocturnal increase in winds develops around 850mb after the sun goes down and lasts into much of the overnight providing moisture, instability, and wind shear to support thunderstorms during the nighttime hours. More on this process and the physics behind it will be provided in a future article to further explain the LBL’s importance in the weather world.
The Marine Boundary Layer
Switching gears, the marine boundary layer (MBL) chiefly differs that of the land boundary layer in that it has direct contact with the ocean instead of the land, allowing for large amounts of heat and moisture to be exchanged. However, the MBL is harder to study than the LBL for a few reasons. First off, there is a lack of observations due to the difficulty of studying the atmosphere over the ocean. Even on an island, local influences from the land can affect soundings. Consequently, little is known about the MBL.
Whereas cumulus clouds can usually be seen above the LBL, stratocumulus clouds are more likely to be seen over the MBL. These flat, low-lying clouds are very important to the earth’s radiation budget, since these clouds essentially act as a white blanket over large swaths of the ocean. This large blanket has a very high albedo (high reflectivity), meaning that these clouds will globally cool the earth’s surface. See below for a satellite image of a swath of these clouds.
The stratocumulus clouds in this layer are formed top-down. An air parcel on the top of the cloud will become negatively buoyant and stable by the cooling of the stratocumulus cloud. This will cause the parcel to sink; therefore causing surrounding parcels to rise (imagine dropping a rock in a cup of water, the water level will rise to make room for the rock as it sinks to the bottom). This process in the MBL creates a well-mixed layer with lots of turbulent air (see here for a great article on turbulence). This turbulent air allows water vapor and heat to be transported up to the cloud, which the cloud needs to stay alive.
Note the difference in boundary layer formation from the LBL. To recap, the MBL develops via stability and sinking air (top-down process) whereas the LBL develops in pretty much the exact opposite way; destabilization and convection (bottom-up process) matures the LBL.
Another important phenomenon that occurs in the MBL is decoupling. Essentially, decoupling occurs when the air that sinks below the cloud base does not reach the ocean surface; this is usually due to intense sunlight. The warming of the sun allows the stable air to retain some buoyancy, and therefore does not completely sink to the bottom of the ocean surface. This will cease the turbulence halfway up the cloud layer, meaning there is little to no air movement. As a result, this disallows the warm water vapor at the ocean surface to reach the cloud surface. Due to this lack of water vapor reaching the cloud, the cloud therefore thins and evaporates. Therefore, this diurnal process of decoupling essentially dissipates the cloud. See below for a comparison of a well-mixed and decoupled MBL.
As a whole, the planetary boundary layer is one of the most important aspects of the climate system. It is in direct contact with either the land or ocean surface, making boundary layer research essential to more accurate forecasting. Many important processes occur in the boundary layer, such as convection, turbulence, and decoupling, making it a vital part of our atmosphere to study and understand.
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©2018 Meteorologist Joseph DeLizio(Land Boundary Layer)
©2018 Meteorologist Joseph Fogarty (Marine Boundary Layer)
How the Weather Effects Fireflies (Credit: The Farmers Almanac, Washington Post, Smithsonian Magazine)
For every summer that I can remember, I remember going outside and catching fireflies in the backyard. These cold-blooded bugs are bioluminescence, which means there is a chemical reaction between luciferin and luciferase. Luciferin is an enzyme which brings oxygen and luciferin together. This creates a lot of energy; to which they emit 100% of its energy by giving off light.
During the winter, fireflies are usually in the larval stage and hibernate by burrowing underground until they emerge in the spring. Larvae live underground in the winter, mature during the spring and emerge in the early summer. When they emerge, it ranges from the third week of May to the third week of June. In years when summer-like weather arrives before June, they tend to appear earlier than usual – like late spring. The air temperature and rainfall play a huge role in when they emerge. Since they feed on snails, slugs, and pill bugs, which are brought out by the rain and moist environment, fireflies like the muggy weather.
Cold-blooded bugs like fireflies slow down when it gets cold. As the weather gets colder, the flash in the fireflies will flash at a slower rate. But once the air temperature reaches 50 degrees Fahrenheit and lower, that’s when they will stop flashing and flying around.
An Ideal night for these insects is when it’s warm and muggy. If it rained during the day, an ideal environment would be present during the nighttime hours for their prey. If it is a cloudy night, the clouds act as a “blanket” over the surface, keeping the warm air from the day close to the surface. Since the moon doesn’t give off any radiation/heat, the clouds have stored energy from the day that they give off to the Earth’s surface during the night. This acts as a “blanket” to the surface keeping it warm throughout the night and not letting the heat escape.
So, if you are trying to look for fireflies, then your best bet would be to do so on a warm and muggy night.
To learn more about other interesting educational stories in atmospheric, oceanic, or climate science from around the world, be sure to click on the following link: www.globalweatherclimatecenter.com/education.
© 2018 Weather Forecaster Allison Finch
Microbursts, coined by Dr. Testsuya “Ted” Fujita, are immensely powerful, localized columns of wind that occur when cooled air falls from the base of a thunderstorm at exceptional speeds – upwards of 60 MPH – and subsequently hit the ground, sprawling out in all directions. Upon the column of air reaching the ground and expanding outwards, it produces straight-line winds, which are capable of reaching speeds up to 100 mph – the equivalent of an EF 1 tornado on the Enhanced Fujita Scale, according to the National Oceanic and Atmospheric Administration (NOAA). Microbursts are more than capable of wreaking havoc by demolishing trees and powerlines, as well as causing extensive damage to buildings.
The most common weather event leading up to the formation of a microburst is dry air entrainment, which occurs when dry air mixes with precipitation inside of the storm cloud. The dry air then causes the droplets to evaporate, resulting in a rapid decline of air temperature at the top of the thunderhead. This patch of cooled air then begins to sink, gaining ample momentum as it falls, essentially turning into a speeding column of air. When this cool, dry air is pulled further down by the weight of precipitation, it becomes “water loaded”and falls to the surface rapidly.
Microbursts can be divided into two classes: wet and dry. Where you reside throughout the country will determine as to which class you’re most likely to experience. For example, if you reside in the Southeastern United States where conditions are primed for thunderstorms, you’re more prone to experiencing a wet microburst. Wet microbursts are typically fueled by both water loading and dry air entrainment. Dry microbursts normally begin with dry air entrainment from moisture within the upper levels, eventually turning into wind-driven weather events with minimal surface precipitation. These typically occur when the relative humidity within the upper atmosphere is moist yet drier beneath the surface. When this occurs, a storm can feed off of moisture high within the storm. As it produces precipitation, the precipitation falls into the dry air, evaporating and cooling the air around it. The Southwestern United States is more likely to experience this phenomenon.
There are microbursts that share both the wet and dry characteristics and are referred to as “hybrids”. Hybrids are fueled by multiple influences such as water loading, dry air entrainment, cooling beneath the base of the cloud and/or sublimation – ice crystals forming directly into vapor.
Though they’re far more common than tornadoes, microbursts are not as well-known. The National Weather Service estimates that for every single tornado, there are roughly ten microbursts reported. While there is not a specified study on how many microbursts occur on average, it is accepted that most wind damage occurring within thunderstorms is likely due to microbursts. The damages caused by microbursts can lead one to believe at first that they’ve been struck by a tornado. The sure-fire way of knowing whether a tornado struck is to study the damage pattern. Tornadoes tend to leave behind a more circular trail of destruction, while microburst winds create straight-line wind damage that typically have a central point of impact.
In terms of age, the study of microbursts is still relatively new within the atmospheric science world. Despite overwhelming advances in technology, it’s still difficult to detect and forecast microbursts. Meteorologists are able to predict an environment that may favor microbursts, but it’s not possible to predict an exact location or a specific storm that may produce a microburst. When forecasting for prime conditions, radar is by far the most helpful tool. Radars show air colliding above the Earth’s surface, which commonly means some of that air is being forcefully pushed downward. Radar technology also has the capability of showing air diverging or spreading outwards in the lower atmosphere right above the Earth’s surface, giving strong indication that a microburst is occurring. As with any form of technology, radar does have its limitations. For example, if a microburst forms on the outer rim of the radar’s scanning circumference, it may appear as a small blip that the meteorologist misses. It also doesn’t help that microbursts can form so rapidly that one could crash into the surface before a warning can be issued.
While there is no guaranteed way to predict microbursts, the best thing one can do to protect themselves is to stay weather aware. This can best be accomplished by paying attention to any severe thunderstorm alerts issued by your local National Weather Service.
There is no question that as we get deeper into the 2018 Atlantic hurricane season, many people around the country and the world have many questions about the likelihood of getting hit by a hurricane either indirectly or directly. More specifically, directly being an all-out head-on landfall in the context of a direct strike and then indirectly being a glancing blow where the eye does not officially make landfall but rather a region being impacted by spiral rain bands at a distance from the center of the tropical cyclone’s circulation core. Hence, as the National Hurricane Center often emphasizes to the general public, even though a hurricane may not be heading directly for your particular location, following the exact center track of a particular tropical cyclone is not what one should be concerned about. Rather, people should always be conscientious about the overall direction of a storm since regardless of the exact landfall location, you are likely to experience some degree of impact from the tropical cyclone if you are within 100 to 200 nautical miles from the center of the storm.
Looking at the graphic attached above (courtesy of Meteorologist Michael Lowry from the National Center for Atmospheric Research or NCAR), it is fairly clear that Florida is undoubtedly the national state leader in terms of historic tropical cyclone landfall occurrences. Based on the statistics from 1851 or 2017 across the tropical Atlantic basin, the state of Florida has accumulated a total of 229 tropical cyclone landfalls which is not even close to the second most landfalls held by Texas at 112 during that time. Hence, there is no question whatsoever that Florida “takes the cake” on historic tropical cyclone landfall likelihood potential.
Therefore, if you are reading this and have any friends and/or family which live and/or plan to visit the state of Florida during this 2018 Atlantic hurricane season or any future years, be sure that they are always logistically and mentally prepared to do what may be necessary. That way, they would be able to more effectively avoid any substantial problems if a tropical cyclone landfall threat were to present itself. As the old phrase goes, always “be prepared” and be proactive rather than reactive.
To learn more about other interesting educational stories in atmospheric, oceanic, or climate science from around the world, be sure to click on the following link: www.globalweatherclimatecenter.com/education.
© 2018 Meteorologist Jordan Rabinowitz
DISCUSSION: No matter how badly a forecaster wants to be 100% accurate, the unpredictability of the atmosphere will guarantee some missed forecasts in their lifetime. But there are a few tools out there that forecasters can use to quantify and take a closer look at how they forecast. This information is invaluable, because it can be used to ultimately improve one's forecasting abilities.
There are many different types of forecasts, and different statistical tools for those forecasts, but for simplicity, the focus here will be on dichotomous forecasts. A dichotomous forecast is a forecast that answers a yes or no question in regard to an event happening. For example, answering questions such as “Will a tornado will occur?” “Will fog will be present?” or “Will it rain before noon tomorrow?” are all examples of dichotomous forecasts. To analyze these types of forecasts, a forecaster can construct a “contingency table.” A contingency table combines the four possibilities that could occur during a dichotomous forecast:
From these tables, different statistics can be calculated to give a forecaster some insight into their own forecasting abilities. For example, if a forecaster wanted to see how often they issue false alarms, they would divide their false alarms by the total times they said “yes, this event will occur.” Using the contingency table, this is just a/(a + b), and this is known as the “False Alarm Ratio”.
These scores can be misleading though, so it is important to clarify which score is being calculated. For example, calculating a forecaster’s accuracy would be the total number of times they got a forecast correct divided by the total number of times they have forecasted. Looking at the contingency table, this is (a + d)/(a+ b + c + d). However, a forecaster usually has many correct negatives, as can be seen in the example contingency table above. Instead of this score, many forecasters use what is called the “threat score” or “critical success index” (TS or CSI). This score is a measure of success, but it does not include correct negatives. Therefore, it is calculated by a/(a + b + c). Since correct negatives are removed from consideration in this score, it is much more sensitive to hits, misses, and false alarms.
As mentioned before, there are many more tools that a forecaster can look at, and a much broader look at forecast verification can be found here!
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© 2018 Meteorologist Joseph Fogarty
DISCUSSION: As we head deeper into the 2018 Tropical Atlantic Basin hurricane season, there is no question that there are many different questions which loom on the minds of many people around the world. Among them, is how to understand and interpret the critical differences between what is referred to as a tropical storm and a subtropical storm. During any given tropical cyclone season in many different ocean basins around the world, there are often occurrences by which a low-pressure system of a tropical and/or subtropical nature develop. Moreover, people and the general media often confuse people regarding the key differences between what constitutes a tropical vs. subtropical storm.
First off, and above all else, tropical storms are warm-core low-pressure systems which often develop deep convection around the circulation center of the tropical storm. This ring of deep convection is often observed from above and referred to as a tropical storm’s central dense overcast (CDO). A CDO is defined via infrared satellite imagery as the continuous or near-continuous ring of coldest cloud tops which surround the center of the tropical storm. On the flip side, subtropical storms are predominantly cold-core low-pressure systems which extract the bulk of their energy from (Sun-based) diurnal heating cycles which is why the convection around the center of subtropical storms is often most vigorous near and around the peak of the day-time heating hours over a given ocean basin.
In addition, since tropical storms being warm-core low-pressure systems, they are often readily identified by the fact that isobars (i.e., lines of constant atmospheric pressure) which chronologically extend out from the center of the storm (i.e., from the point of lowest minimum central pressure) increase in value which makes sense since a storm’s intensity is weaker as you go outward from the center. This is found to be the same with both tropical and subtropical low-pressure systems. However, the marque difference between tropical and sub-tropical storms is that from a vertical perspective, these isobars tend to dip down near the center of the storm with tropical low-pressure systems which helps to explain why they tend to be weaker with height. On the other hand, isobars tend to bump up a bit near the center of subtropical storms which also explains why subtropical storms (and non-tropical low-pressure systems as well for that matter) tend to generally strengthen with increasing height.
To elaborate a bit more on this issue, we will revert to the official definition of a subtropical cyclone. Per the definition from the National Oceanic and Atmospheric Administration (NOAA), “A non-frontal low-pressure system that has characteristics of both tropical and extratropical cyclones. Like tropical cyclones, they are non-frontal, synoptic-scale (i.e., often systems which have life-cycles of between 5 and 7 days or so) cyclones that originate over tropical or subtropical waters and have a closed surface wind circulation about a well-defined center. In addition, they have organized moderate to deep convection, but lack a central dense overcast. Unlike, tropical cyclones, subtropical cyclones derive a significant portion of their energy from baroclinic sources and are generally cold-core in the upper troposphere, often being associated with an upper-level low or trough. In comparison to tropical cyclones, these systems generally have a radius of maximum winds occurring relatively far from the center (i.e., usually greater than 60 nautical miles), and generally have a less symmetric wind field and distribution of convection.” Hence, there are some similarities as well as some key differences between tropical and subtropical storms.
Attached above you will find a recent still image of the ongoing Subtropical Storm Alberto from 3:31 AM EDT on 27 May 2018 and then just below it, a brief corresponding infrared satellite imagery loop.
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© 2018 Meteorologist Jordan Rabinowitz
The belief that “heat lightning” is a real thing, is simply not true, but rather a misunderstanding of the term. Most commonly, people think that heat lightning is lightning that occurs in the clouds when it’s hot outside. When, in fact, the term heat lightning or silent lightning is used to explain cloud-to-ground lightning that occurs very far away.
Cloud-to-ground lightning occurs within a thunderstorm when lightning comes from the clouds and touches the ground - it’s pretty self-explanatory - While sound travels through the lowest layer of the atmosphere, the troposphere, with height, the temperature and density change which results in the sound of thunder being refracted or bent. When thunder is refracted in the troposphere, the sound waves are bent by bodies of air at different densities. Thunder also reflects off the Earth’s surface. Since Earth is round, when it reflects off the surface it sometimes doesn’t make a noise in places that we see lightning. With refracting and reflection, we are left with places that don’t hear any noise when they see lightning. You’re most likely to hear thunder if you are within 10 - 15 miles of the lightning strike.
When you are observing “heat lightning,” you are usually more than 10 - 15 miles away from the storm. In fact, you can see it from up to 100 miles away! The lightning is still visible because light travels faster than sound and isn’t refracted in the troposphere. It is easily seen during the hot, humid nights of July and August. When the sky gets hazy on a hot night, the light from intense thunderstorms can be reflected off this haze, which lights up the sky and can be seen from miles away. Since the sound of thunder doesn’t follow the lightning, we tend to label it as “heat lightning.”
Always remember, that within a thunderstorm, if you can see and hear lightning and thunder respectively, seek shelter and remain cautious. Even though “heat lightning” isn’t exactly real, it’s completely safe to watch since the storm is very far away. One of the most common places this phenomenon occurs is in Florida over the water at night. The remnants of storms that could have formed during the day coming from the opposite coast causes thunderstorms above the oceans and water.
To learn more about other neat educational topics in meteorology, be sure to click here!© 2018 Weather Forecaster Allison Finch
On May 20th, 2013, an EF5 tornado decimated the town of Moore, Oklahoma, killing twenty-four people and inflicting two billion in damages. The Moore tornado is estimated to have been over a mile wide in diameter, staying on the ground for forty minutes and traveling over fifteen miles. This disaster has left many wondering, to this day, how we can better predict these deadly acts of nature. The reality is, we still know very little about tornadoes.
The American Meteorological Society defines a tornado as a “violently rotating column of air, pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud”. According to The National Oceanographic and Atmospheric Administration (NOAA), most tornadoes form from large, rotating thunderstorms known as supercells, which are a combination of these specified factors: instability, moisture, lift, and wind shear. Though the factors are known, no one really knows what magical combination of the aforementioned factors result in a tornado. The Storm Prediction Center, partnered with NOAA), report that numerous weather combinations can lead to tornadoes, but – and this is a bit crazy – the same combinations frequently fail to produce any tornadoes whatsoever. The only reliable way to know whether or not given weather conditions will produce a tornado is if one actually appears.
In addition to the tornado’s elusiveness, there’s also no timeframe as to how long or short a tornado’s lifespan may be. Generally, tornadoes die within a few minutes; the destructiveness behind the Moore tornado was due to its longer-than-average lifespan and higher-than-average wind speeds, topping out at 210mph, making it a monstrous EF5 tornado. A tornado’s strength is measured on what is now called the “Enhanced Fujita Scale”, taken from the simpler Fujita scale, (“F” Scale”), in 2007. This scale was created by Dr. Ted Fujita, a Japanese-born American meteorologist whose focus was on severe weather. He felt as though the Beaufort scale, which was a method back in 1805 that estimated wind speeds by studying how man-made objects behaved in a breeze, was inadequate and unable to properly measure a tornadoes strength. Beaufort’s scale begins at zero wind speed and ends with a hurricane, which is defined as, “…maximum sustained winds reaching seventy-four miles per hour”, according to NOAA.
Dr. Fujita was well aware of other empirical measurements capable between seventy-four miles per hour and the speed of sound, (seven-hundred and sixty miles per hour). He also knew that these measurements would be imperative in measuring a tornado’s destruction. Fujita published a paper in 1971 entitled “Proposed Characterization of Tornadoes and Hurricanes by Area and Intensity”, using results from a three-year study of tornadoes funded by NASA. His paper laid out the basic proposal of the “F” scale: estimating the peak wind speeds of a severe storm by categorizing the damage that is left behind. This scale ranged from an F1 all the way up to an F12, which theoretically would pack winds equivalent to the speed of sound, (though never seen on Earth, winds to this magnitude are common on the planet Neptune).
As with any great idea, there tend to be flaws: It was based on observation, not measurement. Tornadoes are exceptionally destructive; normal weather instruments were incapable of operating, let alone surviving a tornado. Tornadoes are also incredibly unpredictable, making it near impossible to deploy a sturdier instrument in its path. Another issue being that this scale did not take the multitude of varying building materials into consideration: a sturdy home could withstand the winds of a small tornado whereas a mobile home would more than likely be flipped over. Lastly, the scale did not account for time. A brief, rapidly moving storm with excessive winds could actually cause less damage than a slow-moving, long-lasting storm with exponentially slower wind speeds. Realizing these issues, scientists from Texas Tech University suggested changes to the Fujita Scale, coining the Enhanced Fujita Scale. This newly enhanced scale featured tornado damage assessed by meteorologists and engineers across twenty-eight different types of building materials and natural structures. The horrific damage inflicted upon buildings like Briarwood Elementary School, as well as the loss of numerous single-family homes, enabled scientists to originally categorize the Moore tornado as an “EF5”. The Enhanced Fujita Scale came into play in the year 2007, and is now the only true way to judge the impact of a tornado – at least on a physical level.
©2018 Meteorologist Ash Bray
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