Weather Spotting by Evan Ludes

WEATHER SPOTTING A Visual Guide to Midwestern Weather

Warm Air Rain & Hail

Cold Outflow

WEATHER SPOTTING A Visual Guide to Midwestern Weather

With Photography and Text by Evan Ludes

Table of Contents

Introduction

Basic Clouds

Storms on Radar

Hail Formation

Lightning Safety

Storm Diagrams

Conclusion

Skywarn Information

Glossary

About the Author

Introduction

Here in the central United States, weâ&#x20AC;&#x2122;re lucky enough to live in one of the most dynamic climates on Earth. The Rocky Mountains to the west and the Gulf of Mexico to the south provide just the right mix of wind and moisture to create some of the incredible, and sometimes frightening, cloud structures that many Midwesterners have grown accustomed to. For those of us that live in this extreme environment, itâ&#x20AC;&#x2122;s our responsibility to be able to identify

what the sky has in store. With a keen pair of eyes and the information presented in this guide, readers will learn how to discern a strengthening storm from a dying storm, a dangerous storm from a harmless one, and what exactly certain types of clouds can tell us about the weather. It is my hope that this guide will open the eyes of residents of Tornado Alley, and will serve as a catalyst to awaken a deeper fascination and understanding of weather.

Cirrus Clouds Cirrus clouds are one of the most common cloud types out there, and no matter where you live, you can probably spot them in your own skies at some point in the day. Cirrus clouds are high, thin clouds composed of ice crystals in the upper atmosphere. Cirrus clouds typically mean that high pressure is in place, and there is a generally low risk of thunderstorm activity that afternoon.

While the severe storm spotter may consider these clouds boring, they can create spectacular whispy formations as well as some rather unique solar optics. If the sun is high in the sky and you have thin cirrus clouds around, itâ&#x20AC;&#x2122;s worth putting on a pair of sunglasses to check the sky for a 22-degree sun halo, one of the most common atmospheric optical phenomena.

Stratus Clouds Stratus clouds are your classic gloomy gray day clouds. The term “stratus” refers to their sheetlike form. For weather photographers, they’re nothing to gawk at. While they can have some interesting rough textures on their underside, they are generally fairly flat in appearance. Stratus clouds come in multiple varieties such as altostratus (mid-level) and cirrostratus (highlevel sheet clouds). Stratus clouds often inhibit the production of storms due to their sheet-like

nature. By blocking the sun’s rays from reaching the Earth, they prevent instability from building via daytime heating. They do serve an important role in temperature regulation, however. While they may block heat from getting in during the day, they can also prevent it from escaping at night. This is why if it’s cloudy at night, temperatures are generally warmer, and if it clears out, all of the heat escapes into the atmosphere.

Cumulus Clouds

Every storm starts somewhere. Whether it grows into a low-precipitation supercell or a massive squall line, almost every storm begins its lifecycle in a cumulus field. You’ve probably seen a cumulus field before, but didn’t recognize it as a meteorological phenomenon. A cumulus field is your classic partly-cloudy sky, with those puffy cotton ball clouds evenly

spaced apart. While a cumulus field in itself poses no inherent danger, think of it as the atmosphere’s way of showing that it has the potential to create thunderstorms. Once the cumulus clouds start growing taller, they’ll start competing for moisture. Eventually, one or more “win” the race to become a storm and grow into something larger.

Mammatus Clouds Mammatus clouds are easily one of the prettiest types of clouds around, but there are a lot of misconceptions about them. Many people associate seeing mammatus as a precursor to the development of tornadoes, which is simply not the case. Mammatus clouds are simply the result of strong, persistent thunderstorm updrafts. This is a case where tornadoes and mammatus clouds may correlate (since they both come from strong

storms), but there is no causal relationship between the two. If you see mammatus clouds, thereâ&#x20AC;&#x2122;s a good chance that there is a severe thunderstorm in your area. Mammatus clouds can either be on the forward flank of the storm, or on the high extensive anvil behind the storm. Since these clouds are so high up in the atmosphere, they often light up vibrant golden or pink tones at sunset if there are no other clouds blocking them to the west.

Mammatus clouds directly overhead

Storms on Radar

Radar imagery isn’t just useful to scientists and meteorologists. It can be used by anyone as a powerful warning tool. In the next section, we’ll go over the basics of using and reading radar imagery. With this knowledge, you’ll be able to connect realtime data on a screen to the real world, giving you a better idea of the weather affecting your immediate area and any threats it may pose. In the following section, we will briefly discuss how various types of storms may appear on radar.

Most storms you’ll see on radar are what can be considered multi-cell or pop-up thundertorms. These storms appear to be a disorganized mess, often with varying directional vectors. Multi-cell storms are generally benign, though on days with extreme instability (hot summer days), they can produce brief periods of large hail.

HP supercells often appear as big, round balls of heavy precipitation (hence the name!) on radar. Unlike a classic supercell, the hooked portion may be more difficult to identify. If you look very closely at the southwestern portion of this HP supercell, you can make out a small notch. While the tornado would likely be wrapped in rain, that’s where it would most likely occur.

Squall lines are easy to identify on radar imagery. You’ve more than likely seen one before on your local newscast during the weather segment. Squall lines appear as long walls of heavy rain. Oftentimes they are accompanied by outflow boundaries ahead of them, which appear as thin lines. If there’s a squall line moving towards your location, expect high winds followed by a long period of heavy rain.

Classic Supercells Being able to identify classic supercells on radar is crucial for your safety if you live in tornado alley. Classic supercells are best identified by their unique shape or radar signature. Oftentimes they will look like a hook or v-shape. This hooked shape is the result of the turning winds (shear) that are responsible for the longevity of supercell thunderstorms. The location of the hooked portion depends on the direction the storm is moving, but most often it can be found on the southwest side of the storm. In the radar image on the left, there’s a pronounced ball at the end of the “hook” near the town Geuda Springs. This is known as a debris ball, and it’s a good indicator that a tornado is on the ground lofting debris into the air. If you see a hooked supercell or a debris ball heading towards your location, take shelter immediately. Even if the thunderstorm doesn’t produce a tornado, classic supercells are capable of producing extremely large hail that can knock out windows and skylights.

Radar images courtesy of RadarScope

Hail Formation

Although this book isnâ&#x20AC;&#x2122;t meant to be a scientific journal detailing the specifics of various weather phenomena, I felt it was important to give a basic explanation of one of the most common forms of severe weather affecting residents of the Midwest and beyond; hail. Those little balls of ice that come down to shred your plants and make your car look like a golf ball. In this next short section, weâ&#x20AC;&#x2122;ll look at how severe hail forms and how to identify hail-producing storms.

Powerful Updrafts of Ice If you live in the Midwest, you’ve almost certainly encountered hail in your life. It’s one of the most common forms of severe weather (and often one of the most memorable). The process behind the formation of hail actually isn’t incredibly complex. The transformation from a pellet of ice to a gigantic spiked ball of ice can be explained in just a few simple stages.

1.)

Strong thunderstorms carry precipitation high into the atmosphere above the freezing level.

2.) This precipitation accumulates layer upon layer of ice as other precipitation hits it in the updraft. 3.) Eventually, the updraft can no longer sustain the weight of the ice and keep it in the air. 4.) The hail stone falls, sometimes tumbling in the air, causing it to develop icy spikes on its surface.

Rain & Hail

Storm Base

Inflow

Lightning Safety Of all of the weather phenomena encountered while spotting storms, lightning is by far the most dangerous threat out there. It’s also one of the hardest elements of a storm to predict. Since we’ve got a long way to go before we’ll be able to predict when and where exactly lightning will strike, the best we can do is exercise extreme caution and know how to stay out of harm’s way when an electrical storm approaches.

100 Strikes Every Second You may have heard someone say before that you’re more likely to get struck by lightning than win the lottery / get attacked by a shark / die in a plane crash. Believe it or not, this statement actually holds some truth. It should come as no surprise that lightning is one of the leading causes of weatherrelated deaths, because globally, around 100 bolts of lightning strike every second. On average, there are 51 lightning-related deaths in the United States every year. If you don’t want to become a victim of a lightning strike, it’s important that you know what to look and listen for in a thunderstorm. You can determine how far away a bolt of lightning strikes by counting to 5 between the flash and the thunder. Each time you reach 5, that’s one more mile away. However, the simple fact of the matter is that there’s no “safe” distance to be from a lightning strike. If you can hear thunder, you can get struck by lightning. Even if the rain and wind

has stopped, some of the most powerful bolts of lightning can strike far away from a thunderstorm. If you are outside and you hear thunder, seek shelter immediately. Ideally you can find shelter in a building. However, in a worst-case scenario where you’re caught outside, there are still ways to minimize your risk of getting struck. If you feel your hairs standing up on your head or arms, a close strike is imminent. The best way to minimize your risk of being struck is to lie flat on the ground. While lightning is unpredictable, it tends to strike tall, isolated objects. This is why you should never seek shelter underneath a tree during a storm. If you’re outside and spot flashes of lightning or hear thunder, be prepared to drop what you’re doing and seek shelter inside. While lightning can be an amazingly powerful thing to witness, both cloud-to-cloud and cloud-to-ground bolts contain enough electricity to endanger anyone’s life.

Statistics courteousy of noaa.gov

Cloud-to-cloud or “crawler” lightning

Cloud-to-ground bolts or “CG” bolts

Thunderstorm Diagrams

Now that you’ve learned about the basic types of clouds out there, we can get into the nitty gritty. You know that storms start out as basic cumulus clouds, and they gradually grow until they’re towering plumes of convection with spreading anvils. But here comes a cloud that’s not so puffy-looking. This one looks more like something out of “Independence Day”, an alien mothership of a cloud with all kinds of dynamic featuresswirling around. In this next section, you’ll learn what exactly goes on in supercell thunderstorms, and how to identify a storm capable of producing a tornado.

Towering Cumulus To gain a better understanding of how supercells work, we first need to understand how they form. As mentioned previously, every storm starts as a single cumulus, but what are the stages in between? After a storm becomes a cumulus, it grows into what is called a towering cumulus. Just a stage shy of being a full-blown cumulonimbus, towering cumulus clouds have yet to develop an anvil. Towering cumulus clouds often have broad bases, or may be composed of several conjoined bases. While cumulus clouds are round and puffy, towering cumulus clouds are

more vertical in nature. These clouds are just now beginning to draw in the air around them. These areas of inflow (sometimes referred to as inflow streamers) can be found on either side of the storm base during early stages of development. Eventually, the storm becomes a supercell and picks one major area (often the warmest/moist air) to draw inflow from. Towering cumulus, much like their smaller cousins, harbor the potential to develop into severe thunderstorms. Once the tower begins to develop an anvil, itâ&#x20AC;&#x2122;s time to check radar and prepare for some rain.

Anvil of Neighboring Storm

Updraft Motion Inflow Inflow

Pileus (Cap) Cloud

Updraft Struggling Againt the Cap

Pileus or “Cap” Clouds Pileus clouds are certainly one of the lesserknown types of clouds that occur across the Midwest. They’re not rare by any means, but they are relatively transient in nature. Pileus clouds occur when a thunderstorm’s updraft is pushing upwards against a layer of warmer air above it. This layer of warm air, often referred to as the “cap” is responsible for prohibiting thunderstorms from developing. If the cap breaks, thunderstorm updrafts explode upwards, uninhibited by the layer of warm air. If thunderstorms are struggling to break the cap, we often see these pileus clouds develop above

them. If you see a cloud with a pileus cap above it, that doesn’t mean it’s going to fail to break the cap and become a severe storm. It simply means that while there is a layer of warm air in place keeping thunderstorms in check, updrafts are trying hard to break through it. Storms often “shed” pileus clouds as they continue to push against the cap . If you see this happening, there’s a good chance that that storm is going to come close to breaking the cap, and it’s a good idea to have a safe shelter nearby just in case the storm develops rapidly.

Cumulonimbus Clouds Cumulonimbus clouds are where you’ll probably start to finally recognize clouds as storm clouds. Think of a cumulonimbus as a developed cumulus cloud. It’s the cumulus cloud that won the “race” to become a real storm! Cumulonimbus clouds are often referred to as “towers” in the storm chasing community due to their impressive heights. They look like large cauliflower clouds due to their dense convection. Once a storm has developed into a cumulonimbus, its chances for producing severe weather greatly increase.

The longer they grow, the more likely they are to produce heavy rain and hail. If you see a cumulonimbus, it’s time to keep an eye on local media and have the weather radio handy, as cumulonimbus clouds can mature into severe storms at any time. The cumulonimbus pictured here has developed a well-defined anvil, meaning that its updraft has pushed as high as it can go. Crisp, wide-spreading anvils like these often mean that a storm is well-established and is capable of producing severe weather.

Shelf Clouds Shelf clouds, much like scud clouds, are one of the most often misidentified types of storm structures. If you live in the Midwest, you’ve almost certainly seen one before. Shelf clouds are long, often striped or “striated” clouds that stretch from horizon to horizon. If a storm develops into a shelf cloud, this indicates that the storm has become outflow-dominant. It can no longer sustain its updraft, and all of its energy flows down and outward. If you see a shelf cloud coming, prepare for very strong winds and

heavy rains. While shelf clouds pose little risk of producing tornadoes, the straight-line winds that follow shortly behind the shelf cloud are capable of causing significant damage. Although a storm with a shelf cloud may no longer be inflow-dominant, this outflow-dominant beast can persist for hours as it sweeps across the plains. Below is a list of common shelf cloud features that make them easier to identify. If you know what type of storm is coming, it’s easier to prepare yourself!

What’s That? Shelf clouds are often associated with outflow boundaries. These outflow boundaries typically manifest themselves on radar as long, skinny lines radiating out ahead of a storm. If you see this coming on radar, you can almost be certain a shelf cloud is heading your way!

Warm Air Rain & Hail

Cold Outflow

Storm Base

Rotating Motion

Rising Moisture

Funnel

Inflow Into Wall Cloud

Wall Clouds A wall cloud is a specific part of a supercell that is associated with the production of tornadoes. Wall clouds can be found “hanging” underneath the main updraft base of a supercell (hence the name). They often look big and blocky, like a rectangle block attached to the bottom of a storm cloud. The fact that the cloud is actually attached to the storm base sets wall clouds apart from the often misidentified scud cloud. While scud can also be “scary” looking, low, and ragged like a wall cloud, it isn’t attached to the storm base and poses no inherent threat. Wall clouds can be rotating (with the “near”

side of the cloud moving to the right and the “far” side of the cloud moving to the left, like a carousel) or non-rotating. Rotating wall clouds indicate that a tornado is imminent, and you need to find the nearest shelter possible. Wall clouds are one of the most tell-tale signs that a storm is capable of producing a tornado at any time. However, they’re also a little trickier to identify than other supercell features. So what distinguishes a wall cloud from the rest of the storm? Be on the lookout for the following features:

Wall clouds are low, often blocky clouds hanging below the base of a thunderstorm

Wall clouds are attached to the base. This is what distinguishes wall clouds from harmless scud clouds.

Look for the “left to right” carousel motion at the bottom of the wall cloud.

Classic Supercells Supercells are rare types of storms compared to the other clouds we have examined thus far. The most important atmospheric feature that must be present in order for a regular thunderstorm to become a supercell is wind shear. In essence, wind shear is a change in wind speed and direction with height. Think of it this way: at the base of your clouds, the wind is coming from the southwest. As you go higher up, winds come out of the south or even south east. This creates a corkscrewing type of motion in the thundertorm’s updraft, which

makes it capable of going upwards at greater speeds and lasting longer than regular updrafts. Supercells are easy to identify, because this wind shear sculpts the clouds into fantastic spaceshiplike formations. Storm chasers often refer to these as “motherships” or “stacked plates” due to their round and often striated appearance. If you see a supercell, take a picture! And of course, be prepared to take shelter. Supercells are known for producing large hail and strong tornadoes.

Inflow

Rotating Winds (Shear)

Rain & Hail Storm Base

dra ft

Anvil

Veering Winds

Inflow

Surface Moisture

Low-Precipitation Supercells Low-precipitation supercells are a specific breed of supercell thunderstorm characterized by a notable lack of precipitation. While classic supercells have well-defined rain and hail cores that sometimes intersect with the updraft base, low-precipitation supercells often have limited or almost no precipitation, and a rain-free storm base. However, this doesnâ&#x20AC;&#x2122;t

mean that LP supercells arenâ&#x20AC;&#x2122;t capable of producing severe weather. While they may not drop much rain, LP supercells are known for producing sporadic large hail stones, and rarely, tornadoes. From a visual standpoint, LP supercells are the easiest to identify as such because there is no rain obscuring their updraft structure.

High-Precipitation Supercells High-precipitation supercells are characterized by their tendency to produce copious amounts of precipitation. They are known to cause prolonged downpours and vast amounts of hail and wind. Visually, HP supercells look like huge rainy monsters. There is no separate updraft base and rain/hail core. When you look at the sculpted updraft base, the precipitation core is often located immediately inside and below it. HP supercells can also often be identified

by the presence of a green glow. This glow is caused by sunlight refracting through heavy precipitation and hail in the thunderstorm. If you see an HP supercell coming, bring any potentially fragile outdoor objects inside (if you own a car, park it in the garage or a parking structure). Get inside, and seek shelter away from windows. HP supercells have been known to blast through plastic siding and glass windows with wind-driven hail.

Tornadoes Obviously no decent discussion of storms would be complete without touching on the subject of tornadoes. The Midwest is one of the most active areas in the world for tornadoes, though they do occur elsewhere (even along the coasts). While the jury is still out in the scientific community when it comes to determining what specifically causes a storm to produce a tornado, we at least have a good grasp as to what it looks like when it happens. When a thunderstorm updraft begins to spin, complex things begin to happen that we don’t 100% understand yet. However, we know it usually results in the production of a rotating wall cloud. As mentioned previously in the wall cloud diagram, a rotating wall cloud will look like the “close” part of it is going from left to right and the “far” part is going right to left. This motion shows winds are tightening into an area of circulation beneath the wall cloud. Another noteworthy feature is the RFD (rear flank downdraft) cut, which

is basically a punch of dry air that wraps down around the storm. When this RFD punches into the storm, it can increase the cross-directional winds and result in a tornado, or it can occlude the mesocyclone (cut it off) entirely. Identifying tornadoes can be a little tricky, as people are quick to jump to the conclusion that any cloud close to the ground is a tornado. For this reason, we’ve also included examples of ominous clouds that are not tornadoes. Tornadoes are characterized by rotating winds, often accompanied by a condensation funnel, with a ground circulation. If it’s not kicking up dust, it’s just a funnel. And if it’s not rotating, it’s more than likely just scud. But at any moment, a funnel can grow into a full-blown tornado, so it’s important to be able to recognize these early stages. If you see a tornado, report it to 911 or your local weather office immediately. Seek shelter in the nearest fortified building, and keep updated on the weather by using an emergency radio.

Storm Base

RFD Punch

Occluded Meso & Funnel

Tightening Rotation

Wall Cloud Tornado

Shelf Clouds Shelf clouds are often misreported as wall clouds or even tornadoes due to their ominous, grungy appearance. Unlike wall clouds, however, shelf clouds are long, linear, and nonrotating. While things like funnels and even gustnadoes can form along the front edge of these clouds, they generally pose a minimal threat for violent tornadoes. Strong winds associated with shelf clouds can kick up dust and cause damage to trees and other strucutres. If you see one coming, don’t panic. It’s not a tornado, but it’s still a good idea to secure any loose outdoor objects and seek shelter.

Scud Clouds Scud clouds may look ominous and dangerous, but they’re completely harmless. People often mistake scud clouds for wall clouds hanging below storms. However, there’s one easy way to tell a threatening wall cloud from harmless scud: scud clouds aren’t attached to the storm base. Another easy way to spot the difference? Take note of how long the feature persists. If it dissipates in a minute or so, it’s likely just scud. If the feature retains the same general shape for 5 to 10 minutes, it may be a wall cloud attempting to establish itself.

Conclusion I hope that this book provides at least a little more insight into the world of severe weather for anyone who reads it. Our eyes are the greatest tool we have when it comes to increasing awareness about dangerous weather, and a trained eye is a helpful one. You never know when a couple of minutes

of advance warning will be able to make the difference between a safe evening and a life-threatening one. So when youâ&#x20AC;&#x2122;re outside and there are storms in the forecast, keep an eye on the sky, and you just might end up saving the day.

Get Certified Interested in learning more about severe weather? Contact your local weather office and ask about SkyWarn spotter training classes. Taught by professional meteorologists, these (free) classes are a valuable resource and a wonderful source of knowledge for any weather enthusiast. Get your whole family certified, and increase everyoneâ&#x20AC;&#x2122;s weather awareness! Visit http://www.nws.noaa.gov/skywarn/ for sign up information and to find out when your local weather office is hosting these classes.

Glossary Anvil Anti-cyclonic Backing winds Base Cap Cirrus Cold front Convection Cumulus Dew point Downburst EF scale Flanking line Flash flood Funnel Ground clutter Gustnado Hail Hook echo HP storm Humidity Inflow Instability Jet stream

The top of a thunderstorm that spreads outward in a rounded shield shape Counter-clockwise spin (northern hemisphere) Winds turning into (perpendicular to) a front The bottom of a thunderstorm updraft Warm air prohibiting further upward development of storms High, thin, often wispy clouds An incoming surge of cold air Warm, moist air “exploding” upwards Puffy clouds with the beginnings of vertical development A measure of moisture in the air Strong downward winds, often accompanied by heavy rain Intensity of a tornado based on wind damage The main line of convection feeding into a thunderstorm A rapid rise in flood water, often caused by intense precipitation The “beginning” of a tornado that hasn’t touched the ground Junk picked up on radar not associated with precipitation A whirlwind of rotating air, often along an outflow boundary. Caused at the surface, not connected to the cloud base. Ice pellets or balls falling from a thunderstorm Depiction of a rotating thunderstorm on radar. Often looks like a “ball” of precipitation tapering to a peninsula. High-precipitation thunderstorm. Area of rotation is obscured by large hail and heavy rain. How thick/muggy/moist air feels Air flowing into and being ingested by a storm A measure of how easy it is for air to expand upwards Strong winds high in the atmosphere that steer storm systems

Kelvin-Helmholtz waves Lenticular cloud LP storm Mammatus Moisture Outflow Overshooting top Pileus Precipitation core Reflectivity RFD Scud Severe thunderstorm Shear Shelf cloud Stratus Squall line Supercell Surface heating Tornado Cone Wedge Rope Stovepipe Elephant trunk Updraft Virga Wall cloud Warm front

A braided or breaking wave pattern caused by instability A rounded, smooth, lens-shaped cloud downwind of mountains Low-precipitation thunderstorm Round clouds often underneath thunderstorm anvils. Indicative of strong, persistent storms (not necessarily tornadic). Water vapor in the atmosphere Air flowing out (away) from a storm A “bump” above a thunderstorm anvil above the updraft A “cap” cloud above a storm fighting to break through the cap Downdraft area of a storm with hail and precipitation How precipitation is depicted on radar (heavy precip = “high” reflectivity) Rear-flank downdraft, dry air falling behind and wrapping around a storm Low, ragged clouds that are not attached to the thunderstorm base A thunderstorm capable of producing damaging hail (1” in diameter) and strong winds (58 mph) Change in wind speed and direction with height Horizontal thunderstorm cloud associated with a gust front Low gray clouds A strong line of thunderstorms, often brings damaging winds A persistent, rotating thunderstorm updraft Instability created when the sun heats the surface of the earth A rotating cylinder of air capable of significant damage A tornado that is wider at the top and thinner at the surface A tornado that appears wider than it is tall A long, slender tornado resembling a snake A relatively short cylindrical tornado An irregular cylinder with curves or horizontal displacement The “explosive” part of a storm that pushes moisture upwards Precipitation that evaporates before reaching the ground A lowered cloud beneath the base of a thunderstorm, associated with the development of tornadoes A surge of warm air

About the Author Evan Ludes is a photographer and graphic designer based out of Omaha, Nebraska. He started photography in 2007 and has continued to expand his craft since. When heâ&#x20AC;&#x2122;s not working on freelance design, he can often be found driving towards thunderstorms and scouring eastern Nebraska for new photo locations. Evanâ&#x20AC;&#x2122;s work has received recognition both in print and on air, including an interview with The Weather Channel and publication in the 35th Annual College Photo Contest book. His work can be found in several galleries in the Omaha area as well as online at www.FramedByNature.net. email: phone:

evanludes@framedbynature.net 402-547-1269