Tornadoes are one of nature’s most destructive and terrifying forces. When conditions are right, these violently rotating columns of air can form quickly and decimate anything in their path. One interesting phenomenon reported by some tornado eyewitnesses is seeing unusual colors in the sky shortly before or as a funnel cloud forms. This article will explore what colors may appear before a tornado strikes, what causes them, and if they can be warning signs of an impending twister.
Common Tornado Sky Colors
Several colors have been associated with the skies preceding tornado formation. Some of the most frequently reported include:
Greenish-Yellow
A sickly greenish-yellow hue is one of the more common colors people recall seeing. This ominous shade is often described as similar to pea soup. Scientists believe it is caused by the mixing of warm moist air being uplifted rapidly into a thunderstorm updraft region along with cool outflowing precipitation. The combination of atmospheric conditions creates just the right scattering of light to produce this greenish tint.
Greenish-Black
Dark green fading into black is another commonly reported color. This foreboding shade is thought to be caused by deep plumes of water vapor mixed with rotating columns of condensation within a supercell thunderstorm. The lowered visibility produces a dark greenish cast that can transition to black as a tornado begins forming underneath.
Yellowish-Brown
A brown or tan haze has also been observed prior to some tornadoes developing. Dust and debris whipped up by a tornado’s inflow winds may contribute to this coloration. The brownish tint may also be the result of precipitation wrapping around the funnel cloud while it grows and descends. Dirt and sand mixed into the rotation likely accentuate the yellowish-brown tones.
Pink, Purple, and Red
More unusual, but sometimes reported colors include pink, purple, and red. These brighter hues are believed to come from the scattering of sunlight through high cirrus clouds. The ice crystals of these elevated clouds can create pastel pinks and purples as light passes through. Red may also be seen if the setting sun illuminates tornado clouds at just the right angle.
What Causes the Odd Colors?
There are several atmospheric factors that can contribute to the strange sky colors witnessed before some tornadoes:
– Mixing of warm, moist air and cool outflowing air creates green and yellow hues.
– Water vapor and condensation columns in thunderstorm updrafts produce dark greens fading to black.
– Dust and debris sucked into the tornado circulation add yellowish-brown tones.
– Scattering of sunlight through high altitude cirrus clouds creates pinks and purples.
– Position of sunset illuminating tornado clouds produces red hues.
The most common cause seems to be the collision of disparate air masses. When warm and cool air meet, condensation and changes in pressure create ideal conditions for tornado formation. Light passing through this turbulent mixture of gases, water droplets, and debris scatters into eerie colors.
Can Tornado Sky Colors Be Warning Signs?
While witness reports suggest unusual colors may herald tornado development, experts caution against relying on them as reliable warning signs. Here are a few notes regarding these colors and tornado prediction:
– Strange hues only occur preceding some tornadoes, not all. Lack of odd colors does not mean no tornado threat.
– Colors are not reported consistently prior to tornadoes in a given area. Regional variations exist.
– Other thunderstorms can also produce weird colors without developing a tornado.
– Brief time window between sky color changes and tornado formation limits utility as warning.
– Difficult for untrained observers to distinguish between regular storm colors and tornado precursors.
The Bottom Line
While eerie green, black, brown, pink, purple and red sky colors may occur before some tornadoes, they do not happen reliably enough to be considered reliable indicators on their own. Paying attention to official weather alerts, monitoring conditions, and seeking shelter when threatening storms approach is still the best way to stay safe. Treat strange colors as a curiosity rather than a reason to delay taking protective action.
Historical Accounts of Tornado Sky Colors
Looking through weather records, there are many firsthand descriptions of strange colors appearing before destructive tornadoes over the last century and a half. Here are a few intriguing historical examples:
Tri-State Tornado – March 18, 1925
This massive tornado tore a 219 mile long path through Missouri, Illinois and Indiana, killing 695 people. According to eyewitnesses, the skies turned a sickly greenish-black prior to its formation. Heavy dark clouds were observed swirling and rotating over the town of Ellington, Missouri before the half-mile wide funnel touched down.
Tupelo/Gainesville Tornadoes – April 5-6, 1936
A pair of deadly tornadoes struck Tupelo, Mississippi and Gainesville, Georgia two days apart. Observers described a ghoulish glowing green sky before the Tupelo tornado leveled much of the town. Similar greenish clouds swirled above Gainesville just prior to its devastating twister. Together these two storms killed at least 454 people.
Woodward Tornado – April 9, 1947
Regarded as one of the deadliest tornadoes in Oklahoma history, this massive twister killed 107 people in Woodward. According to local reports, the sky turned a dark greenish-black color shortly before the half-mile wide funnel touched down northwest of the city and carved a path of destruction.
Xenia Tornado – April 3, 1974
Claimed as one of the earliest documented cases of a greenish sky preceding tornadogenesis, witnesses reported the clouds above Xenia, Ohio turned an odd yellow-green hue shortly before a deadly F5 tornado struck the town. The storm killed 32 people, destroyed most of Xenia, and was part of a wider tornado outbreak across the eastern U.S.
Oklahoma City Tornado – May 3, 1999
Part of a historic tornado outbreak across the Southern Plains, this powerful twister produced eyewitness reports of a strange green tint to the clouds above Oklahoma City shortly before it formed. The tornado touched down just southwest of the city, becoming one of only two F5 tornadoes documented in the outbreak.
Famous Images of Tornado Sky Colors
In addition to eyewitness accounts, there are also several famous photos documenting the odd sky colors that sometimes precede tornadoes:
Union City, Oklahoma Tornado
One often-cited image shows a dark green, rolling thunderstorm cloud formation near Union City, Oklahoma just before it spawned a large tornado in 1973. The ominous greenish hue is believed to be caused by deep moisture and rotation within the updraft.
Blair, Nebraska Tornado
A 1984 tornado near Blair, Nebraska was preceded by a yellow-green sky according to storm chaser photos. The sickly coloration is attributed to warm, humid air being lifted ahead of the approaching storm.
Happy, Texas Tornado
Video footage of a 2007 tornado near Happy, Texas reveals purple-green clouds swirling at the tornado’s base as it formed. Meteorologists suggest light scattering through high altitude ice crystals produced the colorful effect.
El Reno, Oklahoma Tornado
During the 2011 supercell thunderstorm that generated the deadly El Reno tornado, unusual pink cloud formations were captured on camera by storm observers. The rare color is thought to have been produced by sunset light interacting with the storm’s updraft.
Pilger, Nebraska Twin Tornadoes
A twin tornado outbreak in Pilger, Nebraska in 2014 generated several photos of an odd yellow-brown haze preceding the twisters as winds lofted dust into the storm rotation. The brown tint accentuated the condensation funnel forming underneath.
Scientific Explanations
There are several scientific principles that help explain why tornado skies sometimes turn strange colors compared to an average thunderstorm:
Rayleigh Scattering
The scattering of sunlight by small particles is partially responsible for coloring tornado skies. Different sized particles scatter light in ways that produce different predominant hues.
Mie Scattering
Light interacting with larger water droplets and dust/debris also contributes to tornado color effects. The size of these particles bends light in ways that add brown and red tints.
Absorption of Light
Moisture and particles in the tornado environment can absorb certain wavelengths of light, causing a darkening effect and deep shades of green and black.
Additive Color Mixing
The combination of scattered and absorbed light blending together produces intermediary hues like yellow-brown and purple when multiple effects occur simultaneously around tornadoes.
Refraction of Light
Bending of sunlight passing through density gradients in the turbulent storm environment further alters the colors witnesses may see preceding tornadoes.
| Color Reported | Main Causes |
|---|---|
| Greenish-Yellow | Mixing of warm and cool air; light scattering off water droplets |
| Greenish-Black | Moisture absorption and reduced visibility |
| Yellowish-Brown | Dust scattering sunlight; precipitation wrapping around funnel |
| Pink, Purple, Red | Scattering through high altitude ice crystals; sunset light angle |
So in summary, the odd tornado sky colors arise from a combination of light scattering, absorption, refraction and mixing effects as sunlight encounters the complex environment within tornadic thunderstorms. The same principles that create colorful sunrises and sunsets are at play, but with the added turbulence of extreme weather.
Famous Tornadoes Preceded by Colorful Skies
Some of the most destructive and deadly tornadoes in history have had reports of strange sky colors leading up to their formation. Here are five infamous examples with the colors seen beforehand:
Tri-State Tornado – Greenish-Black
This massive 1925 tornado killed 695 people across a 219 mile path through the Midwest. Eyewitnesses reported black and greenish clouds rotating before it touched down.
Tupelo/Gainesville Tornadoes – Sickly Green
These two deadly 1936 tornadoes struck Mississippi and Georgia two days apart. Observers described an eerie glowing green sky prior to both tornadoes that together killed over 450 people.
Xenia Tornado – Yellow-Green
This 1974 F5 tornado devastated Xenia, Ohio as part of a wider outbreak. One of the earliest documented cases of odd green hues preceding tornadogenesis according to storm observers.
Oklahoma City Tornado – Greenish Sky
A 1999 F5 tornado struck Oklahoma City, killing dozens. Witnesses reported a strange green tint to the skies shortly before tornado formation within an intense supercell storm.
El Reno Tornado – Pink Clouds
Rare pink clouds were photographed preceding the violent 2013 El Reno twister that killed storm chasers. Thought to be caused by unusual scattering of sunset light through storm updraft.
These accounts demonstrate that while unusual sky colors alone don’t guarantee a tornado is coming, many catastrophic twisters have been preceded by sickly green, yellow, brown, pink or other odd hues in the minutes and hours before they formed.
Should I Be Concerned if I Notice Weird Sky Colors?
Spotting peculiar or ominous sky colors may understandably make someone worried a tornado could be imminent. However, while these colors do seem to precede some tornadoes, there are a few reasons they should not cause immediate alarm on their own:
– Many tornadoes lack any color sky changes, so lack of odd hues doesn’t preclude tornado formation.
– Storms can produce strange colors without spawning tornadoes. Don’t assume one will automatically form.
– Official meteorological warnings should carry far more weight than subjective color observations.
– Positioning of sun, time of day, and visibility conditions affect ability to perceive colors accurately.
– Brief period between color changes and actual tornado formation limits their utility.
The Bottom Line
Odd sky colors warrant paying closer attention to weather updates and radar but should not solely dictate actions. Have a safety plan ready regardless since many tornadoes can still occur with little or no color change. Get to shelter well before a tornado’s arrival and do not wait until you see or think one may have formed. Staying weather-aware is better than relying on colors aloft.
Conclusions
In review, a variety of colors like green, yellow, brown, pink, purple, black and red have been observed prior to some tornadoes throughout history. Photographs and eyewitness accounts confirm these eerie sky tones can precede formation of funnel clouds and tornadoes in the right atmospheric conditions. While scientific principles explain the causes of light scattering and absorption producing these hues, they occur inconsistently and cannot be relied upon as accurate tornado predictors.
Having a storm safety plan and seeking appropriate shelter when tornado warnings are issued is still the smartest reaction. But the next time you hear someone describe peculiar colors in the sky during tornado season, there may be some merit to the observation if proper caution is still taken. The mechanics of color production in extreme weather remains a fascinating area of study with much still to be learned about these occasionally ominous meteorological displays.