Weather Terms RVers Need to Know

All the winter storm advisories, alerts, watches, and warnings that we’ll soon start seeing can be confusing. The National Weather Service does a great job of disseminating weather predictions but sometimes it can be hard to know just what is what.

In the year 350 B.C., the Greek philosopher Aristotle gave one of the earliest descriptions of weather patterns in a text called Meteorologica. It included some of mankind’s first attempts to observe and record natural phenomena like water evaporation and earthquakes. Although it was a far cry from the Weather Channel, Meteorologica was the start of something that had eluded human beings for time immemorial: the ability to understand—and even predict—the weather.

Modern weather forecasting is a $7 billion-a-year industry—and for good reason. Despite all the advanced technology of modern society, humans are still pretty much at the mercy of the elements. America’s GDP can fluctuate by more than $1.34 trillion depending on the weather. In 2020 alone, more than 60,000 weather events killed 585 people in the United States and injured more than 1,700 more with flash floods, tropical storms, heat, tornadoes, ice storms, and thunderstorms doing most of the damage.

Weather forecasters are easy targets because, like football referees, people tend to take notice only when they get it wrong. The reality, however, is that meteorologists are right in astonishing percentages. When weathermen and women issue seven-day forecasts, they’re accurate about 80 percent of the time—90 percent for five-day forecasts.

If someone had told Aristotle that human beings would one day be able to accurately predict the weather nine times out of 10, five days in advance, he likely would have laughed at their overactive imagination.

It’s important to note that climate and weather are not interchangeable terms. Weather describes the short-term—day-to-day and hour-to-hour—state of the atmosphere including temperature, precipitation, wind, and visibility. Climate, on the other hand, measures average weather patterns over several decades.

I used a variety of scientific sources to compile this list of common weather terms that RVers should know and understand.

Coachella Valley, California © Rex Vogel, all rights reserved

Atmospheric pressure

Humans inhabit the very bottom of the Earth’s atmosphere and everything above creates atmospheric pressure. High-pressure systems form when downward pressure creates a clockwise air rotation, unlike low-pressure systems which generate counter-clockwise rotation. Both phenomena which are measured with barometers are critical to predicting weather events.

Black ice

Vehicle accidents are the leading cause of winter-related fatalities so when a meteorologist warns about the potential for black ice drivers should take it seriously. Black ice gets its name because it’s so thin that it’s nearly invisible on the road surface but the ice itself isn’t black. Black ice forms when sudden temperature increases causing snow to melt and drip onto roadways that are still cold enough to make the liquid water freeze on contact.

Blizzard

Not just any big snowstorm qualifies as a blizzard. A storm must meet three criteria to earn the harshest classification in winter weather. Blizzards have frequent wind gusts of at least 35 mph, sustained falling or blowing snow that reduces visibility to less than a quarter-mile, and these conditions are maintained for at least three consecutive hours.

Breezy and windy

The terms windy and breezy are sometimes used interchangeably but they don’t describe the same phenomenon. Breezy conditions involve air moving between 12 and 22 mph during pleasant conditions. Windy days, on the other hand, involve stronger winds up to 50 mph during stormy or inclement weather.

Dew point

The dew point represents the temperature to which air would have to be cooled to reach a level of moisture saturation. When it reaches the dew point, droplets of water or dew begin to form on solid objects like grass and vehicles.

Drought

Most people know droughts result from an extended lack of precipitation and abnormally high temperatures but overpopulation and land overuse are contributing factors, too. Droughts are among the most destructive forces in nature—only hurricanes are more economically damaging to the United States.

Usery Mountain Regional Park, Mesa, Arizona © Rex Vogel, all rights reserved

El Niño

The opposing warm half of ENSO is called El Niño (The Boy) which occurs irregularly every two to seven years and is often followed closely by a La Niña (see below) pattern. It warms the oceans and creates the opposite effect in terms of not just ocean temperatures but atmospheric pressure. It, too, is associated with irregular and sometimes severe weather patterns.

Flash flood

Flash flooding occurs when large amounts of water from sudden torrential rains—or occasionally an incident like the breaking of a dam—gushes through a narrow area that isn’t capable of absorbing high volumes of water. In many cases, flash floods which can roll cars and destroy houses happen in the immediate aftermath of extended droughts where parched land can’t absorb the influx of water quickly enough.

Flood crest

Flooding is one of the deadliest and most destructive weather phenomena in the country and on the planet. Weather professionals use specific terminology to describe rivers as they rise from excess water. A flood crest is the peak—the highest level the water will rise—which is the most significant and dangerous time of a flood but also an indication that the flood will soon recede.

Freezing rain

Freezing rain is formed through the same general process that creates sleet (see below) but they’re not the same thing. Sleet falls to the ground as ice. Freezing rain, on the other hand, remains in liquid form until it hits a cold object and then instantly freezes on contact.

Frost

Gardeners make their plans according to the first and last frost schedules in their respective agricultural zones. The frozen version of dew, frost occurs when cold, moisture-soaked air deposits water that freezes and leaves an icy film on things like plants and car windows.

Hail

Unlike sleet (see below) which is ice formed by rain falling through very cold air, hail is a much more dangerous phenomenon associated with much more dangerous weather. Hail forms when powerful updrafts inside of thunderstorms force water well above the freezing level. That water freezes into large hailstones which eventually become too heavy for the updraft and come crashing down to Earth.

Daytona Beach, Florida © Rex Vogel, all rights reserved

Haze

The dreaded three H’s are hazy, hot, and humid. Hot is self-explanatory, humidity deals with the level of moisture in the air but what exactly does it mean to be hazy? A haze can look like a thin fog but it isn’t caused by precipitation. Hazy conditions occur when large amounts of fine, dry particulate matter like dirt are suspended in the air which scatters light and gives the lower atmosphere a cloudy appearance.

Heat index

The heat index is essentially the same thing as the wind chill factor (see below) but for the opposite sensation of environmental exposure. It represents how hot the temperature feels when humidity is considered. The more humid the air, the less perspiration can evaporate which cripples the human body’s cooling system and makes it feel hotter when it’s humid outside.

Heat wave

Heat waves are long periods of abnormally warm weather. To qualify as a heat wave, it must last for at least two days and consist of temperatures that are outside the region’s historical average.

Ice storm

Ice storms are extended episodes of freezing rain that occur when precipitation falls in liquid form and freezes on contact. It becomes an ice storm when a quarter-inch or more of ice accumulates creating dangerous conditions. Ice storms which can be deadly and cause a lasting impact can add 500 pounds to the weight of power lines and increase the weight of tree limbs by a multiplier of 30.

Jet stream

Jet streams are thin but intense winds in the highest reaches of the atmosphere. Following the boundaries of cold and warm air, jet streams blow west to east although their flow sometimes shifts to north and south. Not only do these rivers of air affect global weather and help meteorologists identify atmospheric patterns but they’re crucial to air travel as flying into and out of them can dramatically affect fuel consumption and flight time.

La Niña

One half of the El Nino-Southern Oscillation (ENSO) phenomenon, La Niña (The Girl) is a global weather pattern that describes a dramatic cooling of ocean temperatures in the Western Hemisphere. La Niña is known for its disruptive impact on weather specifically heavy rainfall and an increase in low-pressure systems.

Okefenokee, Georgia © Rex Vogel, all rights reserved

Microburst

Microbursts are among the most dangerous and unpredictable weather phenomena on Earth and they form inside of already-dangerous thunderstorms. Updrafts—columns of rapidly rising air—sometimes suspend large amounts of rain and ice and when the updraft weakens, there’s nothing left to hold all that water and ice in place. That leads to a massive downdraft which sends the core of the column crashing to the ground and, upon impact, bursting out in all directions, leading to tornado-like winds, pressure, and destruction.

Nor’easter

Nor’easters are major, dangerous storms that are exclusive to the Northeastern United States. Geography, however, is not where these storms get their name. Nor’easters are named for the direction in which the storm’s most intense winds blow. Those winds are usually severe and they’re known to bring rain and snow and cause flooding and storm surges.

Polar vortex

The menacing phrase polar vortex is a relatively new term for winter weather forecasting but meteorologists have understood it as a concept for decades. A polar vortex occurs when a large section of very cold air, usually the coldest in the entire northern hemisphere, is pushed down the North American continent as far south as the Midwestern and Northeastern United States.

Relative humidity

Relative humidity is closely related to dew point (see above) but the two terms are not interchangeable. This term describes the amount of atmospheric moisture that exists relative to the amount that would exist if the air was saturated.

Severe thunderstorm

There are garden-variety thunderstorms and severe thunderstorms and when meteorologists mention the latter, the public should take it seriously. To be classified as severe, thunderstorms must include two potentially deadly elements: winds of at least 58 mph and hail at least one inch in diameter.

Sleet

One of the more unpleasant precipitation events associated with winter is sleet which stings the skin and turns roads and sidewalks into ice-skating rinks. Sleet graces the world with its presence when rain or melted snow freezes and turns into ice on its way from the sky to the ground.

Bernheim Forest, Kentucky © Rex Vogel, all rights reserved

Storm surge

It’s common to hear meteorologists warn that storm surge is one of the deadliest and most dangerous parts of major weather events like hurricanes. The phenomenon occurs when significant storms cause an abnormal rise in seawater above the limits of the astronomical tide. Storm surges can cause rapid, significant, and deadly flooding in coastal regions.

Tropical depression

Before a weather event graduates into a tropical storm, it’s a tropical depression. The infant stage of a hurricane, a tropical depression is a tropical cyclone with maximum sustained winds up to 38 mph.

Tropical storm

People sometimes use the terms tropical storm and hurricane interchangeably but one is an evolution of the other. Tropical storms form in the same places and under the same conditions as hurricanes but they achieve maximum sustained wind of just 39–73 mph. If a tropical storm’s maximum sustained winds hit 74 mph, it becomes a hurricane.

Watches and warnings

Meteorologists issue precautions to inform residents about the likelihood of serious and fast-moving weather events like tornadoes and severe thunderstorms. Watches are less serious and indicate that conditions are present for the formation of a severe weather event. Warnings, on the other hand, indicate that an event has been identified by a person or radar, a tornado or thunderstorm is imminent and to seek shelter immediately.

Wind chill

Everyone in North America north of a certain latitude knows there are two temperatures they have to consider when getting dressed in the morning in winter—the actual temperature reading and the one that counts: the wind chill factor. Also known as the feels-like temperature, wind chill represents how cold the weather feels on human skin when the chilling effect of the wind is taken into consideration.

Avery Island, Louisiana © Rex Vogel, all rights reserved

Wintry mix

Two words cold-weather commuters never want to hear are a wintry mix. When precipitation travels through an above-freezing warm layer of air followed by a cold, below-freezing layer, snow, sleet, and freezing rain can fall simultaneously.

Since we’re talking weather, here are a few related articles:

Worth Pondering…

In the spring, I have counted 136 different kinds of weather inside of 24 hours.

—Mark Twain (1835-1910)

Flash Floods: Safety Tips for RVers

TURN AROUND DON’T DROWN

Historic rainfall around St. Louis, Missouri on Tuesday (July 26, 2022) led to flash flooding that submerged cars in a river of water on Interstate 70 and trapped people inside their homes. Flash flooding led to numerous road closures across the St. Louis metropolitan area after a record-setting 6 to 10 inches of rainfall caused widespread flash flooding, the National Weather Service’s (NWS) office in St. Louis reported. St. Louis recorded 8.06 inches of rainfall in five hours since midnight shattering the city’s old daily rainfall record of 6.85 inches logged in August 1915, the NWS said.

Flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

Devastating flash floods throughout eastern Kentucky have left eight residents dead, dozens of homes submerged in water, and others completely swept away from their foundations. Multiple counties across Appalachia Kentucky have endured torrential rains since early Thursday morning (July 28, 2022) as floodwaters began rushing down the hillsides and completely swallowing up portions of the Kentucky River sending residents searching for high ground until rescue teams could save them.

Airports, parking lots, and the entire Las Vegas Strip which houses some of the world’s most famous casinos and hotels were also flooded Thursday. Heavy rain filled countless buildings as the city put a flash flood and severe thunderstorm warning in place.

Clean-up following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

People often have a hard time envisioning the power of moving water. Each year when heavy rains pummel North America’s deserts or mountains, another camper endures a flash flood camping weather disaster. Those who live to tell about it are shocked to learn how these torrential storms can destroy everything in its path—including RVs.

The severity and speed of flash floods make them one of the most harrowing weather events adventurers might encounter. They occur when excessive water fills normally a dry canyon or wash and when creeks and rivers rise rapidly from rainfall within their watershed.

Clean-up following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

According to the National Severe Storms Laboratory, a creek that’s only six inches deep in the mountains can swell to a ten-foot-deep raging river in less than an hour if a thunderstorm lingers over an area for an extended period of time.

More on severe weather: Lightning and Thunderstorms: Safety Tips for RVers

According to the National Weather Service (NWS), flash flooding can happen nationwide. It is also the number one weather-related killer in the U.S. On average, 86 people die each year because they attempted to drive through floodwaters—and unfortunately, that number is increasing.

It takes as little as six inches of water for a vehicle to be swept away.

Evacuation following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

According to FEMA:

  • Six inches of water will reach the bottom of most passenger cars causing loss of control and potential stalling
  • One foot of water will float many vehicles
  • Two feet of rushing water will carry away most vehicles including SUVs and pickups
Clean-up following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

According to the U.S. Geological Survey, water one foot deep typically exerts 500 pounds of lateral force on a vehicle. Once your vehicle is floating, the floodwater becomes your steering wheel. If that water is moving, your vehicle could be swept away, tipped on its side or flipped.

Rising water can enter your vehicle in a manner of minutes, even seconds.

Evacuation following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

The best advice is never to drive through flood waters of unknown depth. As the NWS has campaigned for years: TURN AROUND DON’T DROWN!

NEVER try to walk, swim, or drive through such swift water. If you come upon flood waters, STOP! TURN AROUND AND GO ANOTHER WAY.

More on severe weather: 5 Tips for Avoiding Extreme Weather While RVing

Some people risk destroying their vehicles and potentially losing their lives by driving through floodwaters. It’s a scary experience to come across rising water on the road during a rainstorm, not knowing if you’ll stall out. It is not worth the risk!

Flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

What is Flash Flooding?

Flooding begins within six hours and often within three hours of heavy rainfall (or other cause). Flash Floods can be caused by several things but are most often due to extremely heavy rainfall from thunderstorms. Flash Floods can occur due to dam or levee breaks and/or mudslides (debris flow).

The intensity of the rainfall, the location, and distribution of the rainfall, the land use and topography, vegetation types and growth/density, soil type, and soil water content all determine how quickly the flash flooding may occur and influence where it may occur.

Flash Flooding occurs so quickly that people are caught off-guard. Their situation may become dangerous if they encounter high, fast-moving water while traveling.

Evacuation following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

How do Flash Floods occur?

Several factors contribute to flash flooding. The two key elements are rainfall intensity and duration. Intensity is the rate of rainfall and duration is how long the rain lasts. Topography, soil conditions, and ground cover also play an important role.

Flooding along rivers often occur seasonally when spring rains coupled with melting snows fill river basins with too much water, too quickly. Torrential rains from hurricanes or tropical storms can also produce river flooding.

More on severe weather: Severe Weather: Tornado Safety Tips for RVers

Occasionally, floating debris or ice can accumulate at a natural or man-made obstruction and restrict the flow of water. Water held back by the ice jam or debris dam can cause flooding upstream. Subsequent flash flooding can occur downstream if the obstruction should suddenly release.

Flash floods occur within a few minutes or hours of excessive rainfall, a dam or levee failure, or a sudden release of water held by an ice jam. Flash floods can roll boulders, tear out trees, destroy buildings and bridges, and scour out new channels. Rapidly rising water can reach heights of 30 feet or more. Furthermore, flash flood-producing rains can also trigger catastrophic mud slides. You will not always have a warning that these deadly, sudden floods are coming. Flash flooding occurs within six hours of the rain event. Flooding is a longer term event and may last a week or more.

Evacuation following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

Where do Flash Floods occur?

Flash Flooding is possible anywhere and everywhere. The normally tranquil streams and creeks in your area can become raging torrents if heavy rain falls overhead or even upstream of your location. Flash Flooding can also occur on city streets and highway underpasses.

Key points to keep in mind include:

  • Do not attempt to cross any water higher than your ankles
  • As little as six inches of water flowing quickly can knock an adult down
  • Less than two feet of water can sweep a car away or stall it out with you stuck inside
  • You rarely have time to move your RV; get to higher ground and stay safe

TURN AROUND DON’T DROWN

Flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

Some historical data

Dam break: May 31, 1889, Johnstown, Pennsylvania; the worst flood in United States history; 36-40 foot wall of water; 2,200 died

River flood: December 1991-January 1992, south-central Texas; wide-spread river flooding on the Guadalupe, Brazos, Trinity, and Colorado River basins; up to 17 inches of rain; 15 died; $100 million in damages

Flash flood: June 14, 1990, Shadyside, Ohio; four inches of rain in less than two hours produced a 30-foot high wall of water; 26 died; $6-8 million in damages

Flash flood: August 1, 1985, Cheyenne, Wyoming; six inches of rain in three hours; 12 died; $61 million in damages

Flash flood: June 9, 1972 Black Hills, South Dakota; 15 inches of rain in five hours; 238 died; $164M in damages

Plan ahead: Identify where to go if told to evacuate.

Evacuation following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

Choose campsites carefully to avoid flash flood camping disasters

Flash floods are especially common in the desert. But according to Scientific American, flash floods can happen in both urban and remote settings. Pretty mountain areas are especially vulnerable if the snow melts quickly after a rain storm. Other susceptible areas to worry about are recently burned hillsides.

More on severe weather: Excessive Heat Warnings: Safety Tips for RVers

Weather experts also say that fast-moving water can take out everything in its path—even the largest RVs. The risk is there but don’t let it keep you at home. If you know how to avoid a flash flood camping weather disaster in the first place, you can stay safe. The campsite you choose to park in is the best place to begin.

Evacuation following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

Disaster-proof your campsite

Many RVers love the adventure of wilderness camping. When wilderness RV camping, safety is very important. Don’t park your rig until you find a safe-looking site with a low risk of flooding.

Use common sense and pay attention to your local surroundings. Assess the area. If there’s even a small chance of rain, don’t camp in a canyon or near low spots or anywhere with steep mountain walls closing in on you.

Clean-up following a flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

Keep a weather band radio available especially when camping in storm-prone areas. Leave before a major storm is forecast to strike.

Check weather reports. Flash floods can strike miles from the origin of a storm. Don’t assume that blue skies overhead mean it is safe. Keep an eye on the weather forecast for your region.

Know your escape route. If rain starts falling and your gut instinct is telling you to leave, take a look around to find the fastest way out to safety.

If hazardous weather prompts evacuation warnings by officials, do what is requested. If you’re lucky enough to drive your RV out of the campground, don’t waste time taking your hoses, chairs, etc. Your sewer hose isn’t worth your life.

Flash flood at Catalina State Park, Arizona © Rex Vogel, all rights reserved

In conclusion

Preparing for weather oddities and calamities is part of the RV lifestyle. Nobody expects a flash flood camping disaster but things happen fast when the water rises and it only takes minutes for a deadly catastrophe. If all else fails and you still get trapped in a campground during a flash flood, don’t try to drive your way out of it. Run for the highest ground you can find and you just might live to tell about your dramatic flash flood campground evacuation.

Worth Pondering…

In the spring, I have counted 136 different kinds of weather inside of 24 hours.

—Mark Twain (1835-1910)