Wacky winter dumps snow on every single U.S. state | Science News for Students

Wacky winter dumps snow on every single U.S. state

A slowing jet stream may explain the recent cold and snow that surprised even Florida
Jan 9, 2018 — 6:45 am EST
snowy palm trees
In regions where palm trees grow, one doesn’t expect to see snow. But it can happen, and did last week in parts of the southern United States.

Slushy roads. Ice-topped power lines. Droopy branches sagging beneath the weight of accumulated snow. It sounds like something straight out of a New England winter. In fact, this was the scene right after New Year’s in Florida. And that shouldn’t be, right?

The ocean surrounds this so-called Sunshine State on three sides. That water is as warm as a bathtub’s. This balmy seawater heats the atmosphere all around it. The result? Florida simply doesn’t get that cold.  It normally doesn’t, anyway.

That’s why any snow in Florida is rare.

U.S. snow map
This map shows snowfall over the lower 48 U.S. states from the start of the winter through January 4, 2018. Every state has seen snow fall over at least a portion of it.

But this U.S. winter is not typical.

By year-end, every U.S. state had recorded snow in 2017. Snowfall in Hawaii? Yep. It has mountains whose high elevations poke into the cold upper atmosphere. Texas? You bet. That was back on December 8. So what’s been behind all of this recent wacky winter weather?

The jet stream is a river of air in the upper atmosphere. It races from regions of warmth to those that are cold. It’s the atmosphere’s way of balancing temperature differences. Sometimes, when this river of air snakes too far south, it can drag cold air with it. That’s how a chunk of Arctic air managed to sneak all the way down to the Gulf Coast.

In early December, the jet stream brought an exceptionally vigorous surge of cold air to the Deep South and northern Gulf of Mexico. In the first week and a half of December, this blasted many normally warm states — ones that tourists typically flee to in hopes of escaping cold northern winters.

Corpus Christi is one of the southernmost cities in Texas. It saw snow for the first time since Christmas 2004. This past December it picked up 2.54 centimeters (an inch) of the fluffy white stuff. That number doesn’t tell the whole story, however. That total is what the “official” National Weather Service observation station recorded. But that office is in town. Just a few miles northwest, a full 12.7 centimeters (5 inches) of snow fell. If that had instead blanketed Corpus Christi, that town would have set an all-time record!

lightning map
Map points to sight of lightning strikes during a snowstorm near Corpus Christi, Texas, on December 8, 2017.

It’s challenging to see any lightning during a snowstorm. But you can detect when it’s near by the muffled thunder that may rumble through dense clouds. This thundersnow occurred on the west side of Corpus Christi. That’s where several heavy snow bands formed along the cold front. Three bolts of lightning even struck the ground!

December’s snow made it all the way down to the Mexican border. It created a vista that many residents had never seen before. After all, you don’t usually see snow falling in the midst of palm trees. Ironically, Corpus Christi had by that time this winter picked up more of the frozen white stuff than had so far hit the traditionally snowy cities of Boston, Chicago, Minneapolis, Detroit and Denver.

As this storm system raced east, snowflakes continued to fly. They fell on Arkansas, Louisiana, Mississippi, Alabama and Florida. Farther north in Georgia, the accumulation was more impressive. Many overachieving locations picked up 15.24 centimeters (half a foot). Most meteorologists chalked it up to a freak event. Surely that wouldn’t happen again anytime soon, right?


Another band of heavy snow materialized near New Orleans, La., on January 2, 2018. It trekked into northern Florida. The National Weather Service office there, in Tallahassee, announced winter storm warnings for much of the area. This weather system carried snow and freezing rain all the way up the Atlantic coastline. In New England, it became a weather “bomb.” That means it intensified extremely quickly. Meteorologists described its boost in strength as “explosive.”

Florida’s dusting

The National Weather Service in Tallahassee shared a map showing several communities that picked up 0.64 centimeter (a quarter inch) of ice cover. A widespread dusting of snow to a couple centimeters blanketed much of the Florida panhandle and upper parts of the state’s peninsula. No snow fell farther south, where it was warmer. (Miami, for instance, hasn’t seen snow in nearly 41 years.)

Despite being rare, a Florida snowfall is not unheard of. Irene Sans is a meteorologist at WFTV News in Central Florida. She also serves on the board of the American Meteorological Society. She had predicted Florida’s recent snow, yet still was amazed to see it.

Florida snow map
Amazing amounts of snow and ice hit northern Florida, last week, as this National Weather Service map shows.
National Weather Service/Tallahassee

“It is rare, but it can happen,” she says. “Tallahassee received just a little. It wasn’t much, but enough for many to remember for years. Luckily, this little snow quickly melts.” She jokes that “many of us in Florida do not know how to drive in the snow.”

Maureen McCann works for the American Meteorological Society. She also is a television meteorologist and forecasts weather in neighboring Orlando. She recalls that snow has fallen in local warm-weather zones a few times before. “Central Floridians may remember when snow fell in January 1977.” It accompanied a major outbreak of cold temps, she says. Snow didn’t return again until 2010, and that was at an especially inconvenient time. “It occurred the weekend of the Disney Marathon. Runners who anticipated doing the race in warmer weather were unpleasantly surprised.”

What’s more surprising about this winter’s Florida snow, according to McCann, is how warm it’s “supposed” to be in Orlando at this time of year: 71º Fahrenheit (21.7º Celsius).

Farther north, Savannah, Ga., didn’t quite break its all-time record snow total this month — but the region came close. It picked up 3 centimeters (over an inch). This storm also brought something worse: freezing rain. It glazed roads, sidewalks, cars and even trees with ice. Winds to 113 kilometers per hour (70 miles per hour) blew moisture onto most surfaces. It left the entire area a dangerous, if glistening, wonderland.

dog in snow
Savannah, Ga., got a near-record snowfall last week. Here’s a jacketed dog strutting through the white stuff there on Jan. 3, 2018.
Ben/Flickr (CC BY-NC-ND 2.0)

Savannah’s previous snow record was set 28 years ago. That December 1989 storm dumped 9.1 centimeters (3.6 inches). Jeremy Nelson is the chief meteorologist at WJCL 22 News,  which serves coastal Georgia and South Carolina. He was blown away by the snow. He called it “a winter storm that will be remembered for decades.”

“The biggest snow in 28 years hit Savannah on Wednesday, January 3,” he explained. “The storm started with freezing rain before switching over to snow. Most areas picked up two to three inches of snow. Even the beaches along the Atlantic Ocean picked up an inch of snow!”

Charleston, S.C. also came close to setting a new record. Its top snowfall of 15.2 centimeters (6 inches) fell as part of that same 1989 storm. For now, that old record still stands.

A role for climate change?

So why has the South seen so much frozen precipitation lately? The answer may lie with global warming. Though it may seem surprising, the more Earth warms, the more rivers of frigid air may flow south toward the Gulf of Mexico.

And the reason? The Arctic is warming significantly faster than the rest of the planet. That concept is widely accepted by climatologists. It also appears dramatically in data being collected by NASA satellites and other weather-monitoring instruments used by the National Oceanic and Atmospheric Administration. As northern polar regions warm, the temperature contrast between them and temperate zones — such as the continental United States — diminishes. One result is that the jet stream slows down.

How could a slowing jet stream mean more cold air flowing south? Researchers have recently found some clues.

The jet stream’s speed was not the major issue in the past few weeks’ weather. The recent wacky events relate instead to the amplitude of the jet stream. That’s a fancy word for its waviness.

Jennifer Francis is an atmospheric scientist at the Institute of Marine and Coastal Sciences. It’s at Rutgers University in New Brunswick, N.J. She teamed up with Stephen Vavrus at the Center for Climatic Research. That’s at the University of Wisconsin in Madison. Together they were able to relate a slowing jet stream to a wavier jet stream. To do this, they used archived weather maps. Then they tracked how wavy the jet stream was each day over a period of four decades.

bomb cyclone
This was a scene in New York City on January 4, 2018 as a bomb cyclone sent a blizzard northward up the East Coast of the United States from Florida to New England.
Several Seconds/Flickr (CC BY-NC-ND 2.0)

As the climate continues to warm, they argue, the jet stream will only become wavier. When a jet stream slows, it will also tend to meander more. Then it gets wavy and wonky. And that means a normally northerly flowing stream of cold air might detour into the South, dumping unexpected frozen precipitation along the way.

The frequency of so-called “high amplitude days” in the United States — when the jet stream is extra wavy — has spiked by more than 20 percent in the winter. That’s compared to the average prior to 1979. Actually, the most dramatic spike in wavy days has been showing up in the fall, Francis and Vavrus reported a few years back. This is “when sea-ice loss and increased atmospheric water vapor augment Arctic warming.”

When the jet stream gets wavy, it’s easier for pockets of cold Canadian air to slosh southward. That cold air piles up in the troughs of jet stream waves. Therefore, a wavier pattern can yield sporadic bursts of cold air, even in the Deep South.

As oceans warm, the amount of water vapor in the atmosphere will only rise. And that will feed more moisture into these Arctic outbreaks that now can turn into snow.

Some people have claimed that the recent episodes of snow in weird locations disproves global warming. In fact, the contrary is true. These wacky weather patterns may be a seemingly strange symptom of climate change. As the world continues to warm, Francis warns, we’re going to have to expect the unexpected. Get ready, she says: “An increase in extreme weather events” is in store.

Power Words

(for more about Power Words, click here)

amplitude     A measure of the height of a recurring wave in some signal, water or beam of radiation. In sound, wave amplitude corresponds with intensity — loudness or softness.

archive     To collect and store materials, including sounds, videos, data and objects, so that they can be found and used when they are needed. The term is also for the process of collecting and storing such things. People who perform this task are known as archivists.

Arctic     A region that falls within the Arctic Circle. The edge of that circle is defined as the northernmost point at which the sun is visible on the northern winter solstice and the southernmost point at which the midnight sun can be seen on the northern summer solstice. The high Arctic is that most northerly third of this region. It’s a region dominated by snow cover much of the year.

Atlantic     One of the world’s five oceans, it is second in size only to the Pacific. It separates Europe and Africa to the east from North and South America to the west.

atmosphere     The envelope of gases surrounding Earth or another planet.

average     (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.

climate     The weather conditions that typically exist in one area, in general, or over a long period.

climate change     Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.

climatology     The study of climate over seasons, decades or millennia. Climate varies over time and this field looks at measuring all aspects of climate and using such data to better understand what factors are behind those changes. Scientists who study climatology are known as climatologists.

continental United States      Also known as the lower 48 states, these are all U.S. states except Alaska and Hawaii. They all reside below Canada and above Mexico.

elevation     The height or altitude at which something exists.

frequency     The number of times a specified periodic phenomenon occurs within a specified time interval. (In physics) The number of wavelengths that occurs over a particular interval of time.

global warming     The gradual increase in the overall temperature of Earth’s atmosphere due to the greenhouse effect. This effect is caused by increased levels of carbon dioxide, chlorofluorocarbons and other gases in the air, many of them released by human activity.

jet stream     A fast-flowing, high-altitude air current. On Earth, the major jet streams flow from west to east in the mid-latitude regions of the Northern and Southern Hemispheres.

lightning     A flash of light triggered by the discharge of electricity that occurs between clouds or between a cloud and something on Earth’s surface. The electrical current can cause a flash heating of the air, which can create a sharp crack of thunder.

marine     Having to do with the ocean world or environment.

meander     A bend in a stream or to move slowly and with no straight path in mind.

meteorologist     Someone who studies weather and climate events.

moisture     Small amounts of water present in the air, as vapor. It can also be present as a liquid, such as water droplets condensed on the inside of a window, or dampness present in clothing or soil.

NASA     Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.

National Oceanic and Atmospheric Administration (or NOAA)     A science agency of the U.S. Department of Commerce. Initially established in 1807 under another name (The Survey of the Coast), this agency focuses on understanding and preserving ocean resources, including fisheries, protecting marine mammals (from seals to whales), studying the seafloor and probing the upper atmosphere.

outbreak     The sudden emergence of disease in a population of people or animals. The term may also be applied to the sudden emergence of devastating natural phenomena, such as earthquakes or tornadoes.

palm     A type of evergreen tree that sprouts a crown of large fan-shaped leaves. Most of the roughly 2,600 different species of palms are tropical or semitropical.

peninsula     A parcel of land that is that is attached to the mainland but surrounded by water on three sides.

precipitation     (in chemistry) The creation of a solid from a solution. This can occur if there is too much of a chemical to dissolve completely into a solution. It also can be a sign that some chemical reaction is taking place. (in meteorology) A term for water falling from the sky. It can be in any form, from rain and sleet to snow or hail.

resident     Some member of a community of organisms that lives in a particular place. (Antonym: visitor)

satellite     A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.

sea     An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

sporadic     An adjective that describes events that occur infrequently and at unpredictable intervals.

temperate     In geography, areas that are cooler than the tropics but warmer than polar regions.

trough      A channel, gully or depression in the land that can collect liquids. Or a container with a U-shaped bottom from which animals may feed or drink. (in physics) the bottom or low point in a wave.

water vapor     Water in its gaseous state, capable of being suspended in the air.

wave     A disturbance or variation that travels through space and matter in a regular, oscillating fashion.

weather     Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.


Journal: J.A. Francis and S.J. Vavrus. Evidence for a wavier jet stream in response to rapid Arctic warming. Environmental Research Letters. Vol. 10, January 6, 2015. doi: 10.1088/1748-9326/10/1/014005.

National Weather Service archives: xmACIS2 http://xmacis.rcc-acis.org