These Scientists Intentionally Fly Into Hurricanes

NOAA’s WP-3D Orion (top) and Gulfstream IV-SP (bottom)
NOAA’s WP-3D Orion (top) and Gulfstream IV-SP (bottom)
NOAA

Hurricanes are a terrifying display of nature's power. Even last century, a perfectly sunny day could turn into unimaginable horror without any warning at all, as storms leveled entire towns and upended thousands of lives. We've come a long way since those dark days, and now we can watch hurricanes churn over the ocean in weather broadcasts in time to get out of the way. One of the best ways we can follow these storms is thanks to the men and women who make up the so-called (yes, actually) Hurricane Hunters.

The Hurricane Hunters are scientists working for both NOAA and the United States Air Force who fly airplanes into the worst parts of a hurricane to tell us first-hand what the storm is doing. Bad-ass scientists began regularly flying into storms (on purpose) after World War II, and today the practice is a standard part of hurricane forecasting in the United States. If satellite and radar imagery of a storm are like doctors taking an x-ray of your body, the work of the Hurricane Hunters is like drawing blood, sampling the inside of the storm to get a good idea of what it's doing at the moment.

NOAA's two famous Hurricane Hunter aircraft are Lockheed WP-3D Orions—nicknamed "Miss Piggy" and "Kermit"—that are equipped with special sensors and devices that help the meteorologists look at the storm and understand what makes it tick. The U.S. Air Force's 53rd Weather Reconnaissance Squadron also operates a fleet of 10 WC-130J Hercules aircraft that utilize similar equipment when they fly out into storms.

radar image of Hurricane Matthew, September 2016
A radar image of Hurricane Matthew over the southern Caribbean Sea on September 30, 2016, taken from a NOAA WP-3D Orion.
NOAA-AOC/Google Earth

All of the aircraft are equipped with Doppler weather radar that helps both the airplane crew and meteorologists back on dry ground understand the internal structure of a storm. This radar imagery is useful for seeing the structure of the eyewall—important for determining its strength and longevity—as well as information about rain bands and any intrusions of dry air that could affect the storm's future.

The most important feature of all Hurricane Hunter aircraft is dropsondes, or small tubes filled with weather sensors that are dropped from the aircraft into the storm. Dropsondes work on the same principle as weather balloons, but the sensors go in the opposite direction—up to down. These sensor packages measure conditions like temperature, dew point (moisture), and air pressure, while GPS sensors help determine wind speed and direction. This information is relayed back to the crew in real-time. Dropsondes help meteorologists measure the lowest surface air pressure within the eye of a storm as well as the highest wind speeds in the storm.

One of the most innovative tools the Hurricane Hunters use is a piece of technological wizardry known as a Stepped-Frequency Microwave Radiometer, or SFMR. The SFMR is a device attached to the wing of the aircraft that monitors the amount of microwave radiation being reflected beneath the plane by factors like waves, sea foam, and rainfall rates. Meteorologists are able to use data collected by the SFMR to accurately estimate the wind speed beneath the aircraft. In fact, the National Hurricane Center was able to use data collected by an SFMR on one of the Air Force's planes to determine that Hurricane Patricia's peak winds reached a record-breaking 215 mph [PDF] off the western coast of Mexico in October 2015, which is the highest wind speed ever recorded in a tropical cyclone anywhere in the world.

NOAA also uses a Gulfstream IV-SP aircraft to survey the environments around and ahead of tropical cyclones as they draw closer to land. These aircraft fly at high altitudes and release dropsondes to measure both moisture and wind speed and direction to help meteorologists better understand the environment into which the storm is heading. This data, along with more frequent weather balloon releases on land, can be ingested into weather models to help forecasters create more accurate predictions for the eventual track a tropical storm or hurricane will take—and help keep you safe.

Why Does Humidity Make Us Feel Hotter?

Tomwang112/iStock via Getty Images
Tomwang112/iStock via Getty Images

With temperatures spiking around the country, we thought it might be a good time to answer some questions about the heat index—and why humidity makes us feel hotter.

Why does humidity make us feel hotter?

To answer that question, we need to talk about getting sweaty.

As you probably remember from your high school biology class, one of the ways our bodies cool themselves is by sweating. The sweat then evaporates from our skin, and it carries heat away from the body as it leaves.

Humidity throws a wrench in that system of evaporative cooling, though. As relative humidity increases, the evaporation of sweat from our skin slows down. Instead, the sweat just drips off of us, which leaves us with all of the stinkiness and none of the cooling effect. Thus, when the humidity spikes, our bodies effectively lose a key tool that could normally be used to cool us down.

What's relative about relative humidity?

We all know that humidity refers to the amount of water contained in the air. However, as the air’s temperature changes, so does the amount of water the air can hold. (Air can hold more water vapor as the temperature heats up.) Relative humidity compares the actual humidity to the maximum amount of water vapor the air can hold at any given temperature.

Whose idea was the heat index?

While the notion of humidity making days feel warmer is painfully apparent to anyone who has ever been outside on a soupy day, our current system owes a big debt to Robert G. Steadman, an academic textile researcher. In a 1979 research paper called, “An Assessment of Sultriness, Parts I and II,” Steadman laid out the basic factors that would affect how hot a person felt under a given set of conditions, and meteorologists soon used his work to derive a simplified formula for calculating heat index.

The formula is long and cumbersome, but luckily it can be transformed into easy-to-read charts. Today your local meteorologist just needs to know the air temperature and the relative humidity, and the chart will tell him or her the rest.

Is the heat index calculation the same for everyone?

Not quite, but it’s close. Steadman’s original research was founded on the idea of a “typical” person who was outdoors under a very precise set of conditions. Specifically, Steadman’s everyman was 5’7” tall, weighed 147 pounds, wore long pants and a short-sleeved shirt, and was walking at just over three miles per hour into a slight breeze in the shade. Any deviations from these conditions will affect how the heat/humidity combo feels to a certain person.

What difference does being in the shade make?

Quite a big one. All of the National Weather Service’s charts for calculating the heat index make the reasonable assumption that folks will look for shade when it’s oppressively hot and muggy out. Direct sunlight can add up to 15 degrees to the calculated heat index.

How does wind affect how dangerous the heat is?

Normally, when we think of wind on a hot day, we think of a nice, cooling breeze. That’s the normal state of affairs, but when the weather is really, really hot—think high-90s hot—a dry wind actually heats us up. When it’s that hot out, wind actually draws sweat away from our bodies before it can evaporate to help cool us down. Thanks to this effect, what might have been a cool breeze acts more like a convection oven.

When should I start worrying about high heat index readings?

The National Weather Service has a handy four-tiered system to tell you how dire the heat situation is. At the most severe level, when the heat index is over 130, that's classified as "Extreme Danger" and the risk of heat stroke is highly likely with continued exposure. Things get less scary as you move down the ladder, but even on "Danger" days, when the heat index ranges from 105 to 130, you probably don’t want to be outside. According to the service, that’s when prolonged exposure and/or physical activity make sunstroke, heat cramps, and heat exhaustion likely, while heat stroke is possible.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This article has been updated for 2019.

Is the Heat Index Real?

MarianVejcik/iStock via Getty Images
MarianVejcik/iStock via Getty Images

Complaining about the humidity is a mainstay of small talk. “It’s not the heat that gets you, it’s the humidity” is a common refrain around the South, just as “it’s a dry heat” is a go-to line in the desert Southwest. The clichés aren’t wrong on this one—a hot and humid day can have a dramatic effect on both your comfort and your health. We can measure this very real impact on your body using the heat index. 

The heat index is the temperature it feels like to your body when you factor in both the actual air temperature and the amount of moisture in the air. If the heat index is 103°F, that means that the combination of heat and humidity has a similar physical impact on your body as it would if the actual air temperature were 103°F. Even though it’s tempting to think of the heat index as an exaggerated temperature that only exists to make the heat sound worse than it really is, scientists came up with the measurements after decades of medical and meteorological research devoted to studying the impact of heat and humidity on the human body. It’s the real deal.

The dew point is an important component of the heat index. The dew point is the temperature at which the air would reach 100 percent relative humidity, or become fully saturated with moisture like on a foggy morning. Since cooler air can’t hold as much moisture as warmer air, lower dew points reflect lower moisture levels and higher dew points indicate higher moisture levels. Dew points below 60°F are comfortable, while readings reaching 70°F and even 80°F range from muggy to downright oppressive.

Measuring humidity on a hot day is important because moisture is how your body naturally cools itself off. Your sweat cools the surface of your skin through a process known as evaporative cooling. If the air is packed with moisture, it takes longer for your sweat to evaporate than it would in more normal conditions, preventing you from cooling off efficiently. The inability to lower your body temperature when it’s hot can quickly lead to medical emergencies like heat exhaustion or heat stroke, which is why the heat index is such an important measurement to pay attention to during the summer months.

The heat index is generally considered “dangerous” once the value climbs above 105°F, and your risk of falling ill increases the higher the heat index climbs.

Dry climates can have the opposite effect on your body, with the distinct lack of moisture in the air making it feel cooler to your body than it really is. Summers get oppressively hot in places like Arizona and Iraq, but the heat doesn’t affect residents as severely because the air is extremely dry. Dew points in desert regions can hover at or below 32°F even when the air temperature is well above 100°F, which is about as dry as it can get in the natural world.  

In 2016, a city in Kuwait measured the all-time highest confirmed temperature ever recorded in the eastern hemisphere, where temperatures climbed to a sweltering 129°F during the day on July 21, 2016. The dew point there at the same time was nearly 100 degrees cooler, leading to a heat index of just 110°F, much lower than the actual air temperature. That’s not necessarily a good thing. Extreme heat combined with extreme aridity can make your sweat evaporate too efficiently, quickly dehydrating you and potentially leading to medical emergencies similar to those you would experience in a much more humid region of the world. 

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This story has been updated for 2019.

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