Friday, April 7, 2017

25 Weather Myths and Faux Pas Debunked

Jon Erdman, Jonathan Belles
Published: April 7,2017
Legends and faux pas have survived through the years, but it's now time to debunk 25 common weather myths.

1. Myth: Lightning never strikes twice.

Some weather myths are simply benign and worth a chuckle. Some stubborn myths are dangerous.
We're highlighting and debunking 25 of those myths and faux pas we hear most frequently, starting with this long-held myth about lightning.
THE FACTS: 
  • Tall, pointed, isolated objects can generate strong enough electric fields to be struck repeatedly. For example, the Empire State Building in New York City is struck about 100 times each year, on average.
  • If a thunderstorm is slow-moving, some lightning-prone locations can get struck multiple times from a single thunderstorm.
  • Roy Sullivan, a park ranger, was struck seven different times, the most of anyone on record.

2. Myth: A hurricane's impact is determined by its winds.

THE FACTS: 
  • Yes, a hurricane's winds can produce significant structural damage, frequently extending well inland from the coast.
  • Half of the U.S. Atlantic tropical cyclone deaths from 1963-2012 were due to storm surge.
  • While wind speed is one factor, the hurricane's size (extent of hurricane and tropical storm-force winds) is also a major player in storm surge magnitude.
  • Recent examples of large, destructive storms relatively low on the Saffir-Simpson Hurricane Wind Scale near landfall:  Sandy (2012), Isaac (2012), Ike (2008).
  • Only 5 to 10 percent of U.S. Atlantic tropical cyclone deaths are directly from high winds.

3. Faux pas: "A waterspout came ashore and became a tornado."

THE FACTS:  

4. Myth: Florida is the Sunshine State.

THE FACTS: 
  • No offense to Florida tourism, but they can't hold a candle to the Desert Southwest when it comes to sunshine frequency.
  • Phoenix (211 days) sees more than double the number of clear days (three-tenths of sky with clouds or less) each year than Tampa (101 days).
  • Florida's wet season (May through mid-October) can, at times, feature daily thunderstorms with heavy rain. 

5. Myth: Seattle is the rainiest U.S. city.

(Photo credit: John Foxx/Thinkstock)
THE FACTS: 
  • Thanks to the Olympic Mountains to the west of the city acting as a rain shadow, Seattle picks up less precipitation each year (37.41 inches) than New York (49.92 inches) or Miami (61.92 inches).
  • That said, Seattle has more days with precipitation (152) than both New York (121) and Miami (135). 
  • Therefore, Seattle's rain is more frequent, but light.
  • Seattle is also one of the cloudiest U.S. cities, averaging only 43 percent of possible sunshine and 226 cloudy days during the year.
  • The Pacific Northwest also has a dry season. Less than one inch of rain typically falls in both July and August in Seattle.

6. Myth: Tornado Alley lies in the Plains states.

THE FACTS: 
  • "There is a substantial tornado threat for all states east of the Rocky Mountains, with the threat somewhat reduced in the Northeast," says Dr. Greg Forbes (Twitter), severe weather expert for The Weather Channel.
  • "A modern definition of Tornado Alley meant to include the longest, strongest, and deadliest tornadoes would include the Gulf Coast states, southern Tennessee Valley, and southern portion of the 'traditional tornado alley'," says Forbes.
  • Recent outbreaks outside the traditional Plains alley: April 2011 Superoutbreak | April 27-30, 2014 Severe Outbreak
  • MORE: Monthly tornado threat maps

7. Myth: Chicago is the windiest city.

THE FACTS: 

8. Faux Pas: "It's 90 degrees with 90 percent humidity."

THE FACTS: 
  • There are few locations in the world where these conditions would occur simultaneously.
  • A 90 percent relative humidity with an air temperature of 90 degrees requires a surface dew point of roughly 87 degrees.
  • According to Weather Underground's Christopher Burt, dew points that high occur along Ethiopia's Red Sea coast, the Gulf of Aden coast of Somalia and Persian Gulf.
  • Therefore, those complaining about these conditions in, say, New York City or Iowa, on a sweltering summer day are exaggerating.

9. Myth: It never snows in Florida.

A cold day, but an open beach on Jan. 9, 2010 in Ft. Myers, Fla. (iWitness/Shaidet)
THE FACTS: 
  • On rare occasions following a sharp Arctic front in January or February parts of Florida can see snow.
  • In early January 2010, flurries and sleet were observed as far south as the Miami suburb of Kendall.
  • In a January 1977 cold wave, West Palm Beach picked up its first snow on record. Flurries were seen in Homestead, the southernmost U.S. location to see snow of any kind.
  • MORE: 10 Shocking Snow Cities

10. Faux Pas: "It struck without warning."

THE FACTS: 
  • Given the technology available today and increased forecaster skill, the average lead time for tornado warnings is 13 minutes.
  • Eighty percent of tornadoes occur in tornado-warned areas.
  • Hurricane/tropical storm warnings are issued 36 hours in advance of those conditions arriving in the warned area. Watches are issued 48 hours in advance.
  • According to 2006 statistics, winter storm warnings are issued on average 17 hours in advance, with an accuracy of 89 percent.
  • While there are still cases that go unwarned, the statistics bear out the lion's share of hazardous weather is warned well in advance.
(MORE: The Future of Tornado Warnings: More Precise, More Lead Time, Fewer False Alarms)

11. Faux Pas: "It's a blizzard outside!"

THE FACTS: 
  • We understand the excitement of a snowstorm outside your window, but there are strict criteria to meet for a storm to qualify as a blizzard.
  • This criteria is easier to satisfy in rural, unforested, open areas where winds are stronger.
  • Heavy snowfall in the absence of strong winds is not a blizzard.
  • MORE: Blizzard Alley

12. Faux Pas: "A tornado touched down."

THE FACTS: 
  • "We now believe the tornado circulation forms quickly near the ground, rather than gradually building downward," says Dr. Greg Forbes (Twitter), severe weather expert for The Weather Channel.
  • On a related note, what may appear to be a funnel cloud may actually be a tornado, if the rotation at the surface does not yet have a condensation funnel, or hasn't ingested or lofted any dust or debris.
  • Also, the word "tornado" implies a circulation at the surface, so the oft-cited phrase, "Tornado on the ground" is redundant.
  • MORE: Tornado Central

13. Myth: "I'm 100 percent safe from lightning in my home."

THE FACTS: 
  • While seeking shelter indoors in a substantial shelter is best when you first hear thunder, you can still be struck if you're in contact with anything that conducts electricity.
  • Avoid electrical appliances, computers, landline phones and other wires. Also, avoid plumbing fixtures/showers, metal doors and windows.
  • On Aug. 20, 2013, a 15-year-old boy was burned from a video game system when lightning struck his home in Belville, N.C. 
  • MORE: Lightning's Shocking Damage

14. Myth: Raindrops are shaped like teardrops.

Shape of raindrops as they grow in size, then breaking up. (USGS)
THE FACTS: 
  • The smallest raindrops are spherically shaped.
  • As raindrops grow and fall, the drag force increases, flattening the bottom of the drop and the drop becomes more hamburger shaped.
  • Once the raindrop grows large enough, the drag force becomes high enough to split the drop into smaller drops.

15. Myth: "It's only a tropical storm."

THE FACTS: 
  • There is only 5 mph difference between a strong tropical storm (70 mph) and a Category 1 hurricane (75 mph). 
  • A large, slow-moving tropical storm can generate significant storm surge flooding. 
  • Recent example: Surge flooding from Isaac (2012) was largely set in motion while it was a tropical storm.
  • Slow-moving tropical storms, or inland remnants of prior hurricanes, can pose a major threat for heavy rainfall and inland flash flooding.
  • Rainfall flooding accounts for 25 percent of U.S. tropical cyclone deaths.
  • Recent examples: Debby (2012), Irene (2011), Allison (2001)
  • High surf and rip currents generated from a tropical storm can be deadly.
  • Tropical storms, or inland remnants of prior hurricanes can spawn tornadoes. 
(MORE: 4 Tropical Storms That Overachieved)

16. Myth: It's always sunny in Southern California.

THE FACTS: 
  • While much of California sees between 66 and 88 percent of possible sunshine each year, fog is common along the California coast in the morning, particularly in summer.
  • In the wake of cold season storms, dense tule fog can form in the Central Valley, sometimes persisting for several days.
  • MORE: How Fog Forms, Most Fog-Prone Areas
  • Los Angeles averages more than 2 inches of rain in December and March, and more than 3 inches of rain in January and February, when Pacific storms are directed into the Golden State.
  • CLIMATE AVERAGES: Los Angeles | San Francisco | San Diego

17. Myth: "Open windows when a tornado approaches."

THE FACTS: 
  • Homes don't explode from higher pressure trapped in the home as the low pressure tornadic circulation arrives. 
  • "Homes are porous, with cracks around doors and windows, vents for bathrooms and the clothes dryer, among others," says Dr. Greg Forbes, severe weather expert for The Weather Channel. Therefore, the pressure nearly equalizes on its own, according to Forbes.
  • A tornado's intense winds damage homes, not an explosion from a pressure difference.
  • You will simply waste valuable seconds opening windows, and you also risk letting the tornado's winds inside your home.
  • MORE: WeatherREADY tornado safety tips

18. Myth: Heat lightning


From the Florida Everglades.
(Credit: dhwicker/iWitness )
THE FACTS: 
  • Other than near-surface warmth most often generating thunderstorms, there's nothing magic about heat and lightning.
  • The term heat lightning refers to lightning flashes occurring too far away to hear thunder. 
  • How far away you can hear thunder depends on the weather conditions.
  • "In general, thunder cannot be heard more than 15 miles from the lightning strike," says Dr. Greg Forbes, severe weather expert for The Weather Channel.
  • In some cases, lightning can be seen from as far away as 100 miles.

19. Myth: Lightning always strikes the tallest object.

THE FACTS: 
  • Lightning will strike the best conductor of electricity at the surface, which may not be the highest point.
  • "If the object is within the distance of the forks in a lightning bolt, it will probably take a hit," says Dr. Greg Forbes, severe weather expert for The Weather Channel. However, a lightning channel will not make a large horizontal detour simply to hit the highest object.
  • "Even with antennae and guy wires above the launch pads at the Kennedy Space Center, sometimes the lightning strikes lower structures or the ground nearby," says Forbes.

20. Myth (sort of): "Paradise sums up Hawaii's weather."

THE FACTS: 
  • Hawaii does have a wet season during the winter months, as so-called Kona storms and tail ends of north Pacific cold fronts bring significant rain to both leeward and windward locations. 
  • Honolulu picks up 70 percent of its average annual rainfall from November through March.
  • Honolulu (17.05 inches each year, on average) is wetter than Los Angeles (14.93 inches).
  • The wettest location in the U.S. is Mt. Waialeale, on the island of Kauai, picking up 460 inches of rain each year. This is due to the persistence of moist northeast trade winds wringing out moisture over the mountain's slope.
  • Eight named tropical cyclones have affected the islands from 1979-2012, including Hurricane Iniki (1992), Hurricane Iwa (1982) and Hurricane Dot (1959).
  • Three tropical systems threatened or affected Hawaii in 2016: Darby, Lester and Madeline 
  • That all said, it's hard to argue with daily average highs in the 80s, morning lows from the mid-60s to mid-70s year-round, and only 89 days a year with measurable rainfall.
  • CLIMATE AVERAGES: Honolulu | Maui | Hilo

21. Myth: Highway overpasses are safe tornado shelters.

THE FACTS: 
  • The first video clip above sent shivers through many meteorologists. Put simply, never take cover from a tornado under a highway overpass.
  • Tornado wind speeds increase with height and accelerate as air is forced through narrow corridors such as under a highway overpass.
  • You could easily be blown out and/or bombarded by wind-lofted debris. Most bridges don't have girders to hold onto, as in the first video above.
  • "That was a weak tornado whose strongest side missed them," says Dr. Greg Forbes (Twitter), severe weather expert for The Weather Channel, in reference to the infamous Kansas turnpike video above.
  • Three were killed near or under overpasses during the May 3, 1999 Oklahoma outbreak. 
  • WHAT TO DO: If you see a tornado while driving

22. Faux Pas: "This thunderstorm was a monsoon."

THE FACTS: 
  • From the Arabic word for "season," a monsoon is any persistent wind that sharply changes direction from one season to the next.
  • The best example of this is the South Asian monsoon. Heating of the continent in late spring and summer drives a shift to southwest winds. In essence, this is a sea-breeze on a massive scale, heralding the rainy season. 
  • A much weaker example of this occurs in the southwest U.S. in summer (July through September).
  • No single thunderstorm on any given day is a "monsoon." The term describes a much larger-scale process than individual thunderstorms, no matter how strong they are or how much rain they produce.

23. Myth: Tornadoes or lightning are the greatest weather killers.

THE FACTS: 
  • Globally speaking, the deadliest weather-related disasters have been due to either flooding (up to 4 million killed in China in 1931) or tropical cyclones (Great Bhola Cyclone killed 300,000-500,000 in Bangladesh in 1970).
  • Outside of disasters like Hurricane Katrina, the Joplin tornado  or the April 2011 Superoutbreak, the greatest weather killer in the U.S., on average, is extreme heat. 
  • More than 700 people were killed in the Chicago heat wave of July 1995. More than 70,000 were killed during the European heat wave of 2003.
  • MORE: How weather patterns predict heat waves

24. Myth: Severe thunderstorms form from a clash of warm and cold air masses.

THE FACTS: 
  • You have likely seen a tornado documentary with a map of the central U.S. depicting a clash of warm and cold air masses.
  • While some squall lines with wind damage can be forced along a cold front, it is a vertical difference in air mass that is key for most severe thunderstorms.
  • Relatively warm, moist air near the surface topped by cold, dry air several thousand feet aloft increases instability.
  • "The strongest tornadoes are usually in the warm, moist air ahead of a cold front, not right on it," says Dr. Greg Forbes (Twitter), severe weather expert for The Weather Channel.
  • Some tornadic supercells can also form on the immediate cold side (to the north) of a warm front, as well, where wind shear is also maximized.
  • Finally, waterspouts and some non-supercell tornadoes called landspouts don't need a cold or warm front anywhere near them.

25. Faux Pas: "It is supposed to rain/snow today."

"It's supposed to rain today." You've likely heard someone say this at least once. It's one of the most misunderstood concepts in weather.
It's true there are situations where rain or snow is a certainty, during which the forecast simply says, "Rain tonight, ending by dawn tomorrow morning."
Most of the time, however, forecasts are given a probability of precipitation, or POP. This is the chance of seeing measurable precipitation at any location during a given time. For example, "Partly sunny today, with a 60 percent chance of showers and thunderstorms." This POP forecast also says six times out of 10, the same weather conditions would produce rain in your location.
That also means there's a 40 percent chance it won't rain, though. Regardless, there's a tendency to look at a POP higher than 50 percent as a certain forecast of rain or snow. "It's supposed to rain today."
The low side of the POP forecast can also cause indigestion.
In one scenario, a 20 percent chance of rain today may be followed by a 100 percent chance tonight. If the instigating weather system moves a bit faster than forecast, you could see light rain during your child's soccer game. If the chance is greater than zero, plan for it just in case.
In reality, these POP forecasts also imply a bit of uncertainty on the part of the forecaster. A 100 chance of rain shows high forecaster confidence. A 40 percent chance, greater uncertainty.
While we're addressing this, let's talk summer thunderstorms.
A forecaster can be confident there will be afternoon thunderstorms over a given area, but often times, the state of the science is not to the point of predicting County A will be soaked while neighboring County B stays dry. This is the "scattered thunderstorm" forecaster headache.
In this case, some forecasts may not have a POP, but rather specific adjectives that define how widespread thunderstorms will be:
  • Isolated:  10-20% areal coverage
  • Scattered:  30-50% areal coverage
  • Numerous:  60-70% areal coverage
  • No description:  80-100% areal coverage
So, yes, your afternoon baseball game can get soaked from an "isolated thunderstorm." Another day, you may be lucky enough to avoid rain despite a forecast of "numerous thunderstorms."
The bottom line is to remember the word chance in your forecast. Meteorology has come a long way over the past several decades, but it's still an inexact science.
MORE:  What Weather Words Mean
You can read about 10 weather terms you've never heard of here.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.
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