As a hurricane intensifies, hurricane hunters are in the sky doing something almost unimaginable: flying through the center of the storm. With each pass, scientists aboard these planes take measurements that satellites can’t, sending them to meteorologists at the National Hurricane Center.
Jason Dunion, a meteorologist at the University of Miami who has led hurricane field programs for the National Oceanic and Atmospheric Administration, described the technology the team uses to measure hurricane behavior in real time and the experience aboard a P-3 Orion as it dives through a hurricane’s eyewall.
What happens on board a hurricane hunter when you fly into a storm?
We’re essentially taking a flying laboratory into the heart of the hurricane, all the way up to Category 5. As we fly, we’re processing data and sending it to meteorologists and climate modelers.
In the P-3s, we routinely slice through the center of the storm, right into the eye. Imagine an X pattern: we continue to slice through the storm multiple times during a mission. These could be developing storms, or they could be Category 5s.
We usually fly at an altitude of about 10,000 feet, about a quarter of the distance between the ocean surface and the top of the storm. We want to cut through the roughest part of the storm because we are trying to measure the strongest winds for the Hurricane Center.
That must be intense. Can you describe what scientists experience on these flights?
My most intense flight was Dorian in 2019. The storm was near the Bahamas and quickly strengthened to a very strong Category 5 storm, with winds of about 185 mph. I felt like I was a feather in the wind.
When we came through the eyewall of Dorian, it was all seat belts. You can lose a couple hundred feet in a couple of seconds if you have a downdraft, or you can get an updraft and gain a couple hundred feet in a matter of seconds. It’s a lot like a roller coaster ride, except you don’t know exactly when the next up or down is coming.
At one point we had G-forces of 3 to 4 G. That’s what astronauts experience during a rocket launch. We can also zero G for a few secondsand whatever is not attached will float.
Even in the rough parts of the storm, scientists like me are busy on computers crunching the data. A technician in the back may have launched a dropsonde from the belly of the plane, and we’re checking the quality of the data and sending it to modeling centers and the National Hurricane Center.
What do you learn about hurricanes during these flights?
One of our goals is to better understand why storms rapidly intensify.
Rapid intensification is when a storm gains speed by 35 mph in just one day. That’s equivalent to going from a Category 1 to a major Category 3 storm in a short amount of time. Ida (2021), Dorian (2019), and Michael (2018) are just a few recent hurricanes that have intensified rapidly. When that happens close to land, it can catch people unprepared and become dangerous quickly.
Because the storm can become very intense in a very short time, we need to have hurricane hunters out to take measurements as the storm develops.
So far, rapid intensification has been hard to predict. We can see the ingredients coming together quickly: is the ocean warm down to great depths? Is the atmosphere nice and juicy, with lots of moisture around the storm? Are the winds favorable? We also look at the inner core: what does the structure of the storm look like and is it starting to consolidate?
Satellites can give meteorologists a basic picture of the weather forecast, but to really analyze the hurricane properly, we first need to deploy our hurricane hunters into the storm itself.
What does a storm look like when it rapidly increases in strength?
Hurricanes like to stand upright – think of a spinning top. So what we’re looking at is alignment.
A storm that hasn’t quite come together yet may have a low circulation a few miles out over the ocean that’s not aligned with the center circulation at 6 or 7 kilometers. That’s not a healthy storm. But a few hours later, we may fly back to the storm and find that the two centers are more aligned. That’s a sign that it could intensify quickly.
We also look at the boundary layer, the area just above the ocean. Hurricanes breathe: they take in air at low levels, the air flows up the eyewall, and then blows it out the top of the storm and away from the center. That’s why we get these huge updrafts in the eyewall.
So we can look at our dropsonde or tail doppler radar data to see how the winds are flowing at the boundary layer. Is that really moist air flowing into the center of the storm? If the boundary layer is deep, the storm can also take a bigger breath.
We also look at the structure. Often the storm looks healthy on satellite, but when we come in with radar, the structure is sloppy or the eye is filled with clouds, which tells us that the storm is not quite ready to intensify quickly. But during that flight, we can see the structure change quite quickly.
Air in, up, and out—breathing—is a great way to diagnose a storm. If that breathing looks healthy, it can be a good sign of an intensifying storm.
What tools do you use to measure and predict hurricane behavior?
We need instruments that measure not just the atmosphere, but also the ocean. Winds can steer a storm or tear it apart, but the ocean’s heat and moisture are its fuel.
We use dropsondes to measure temperature, humidity, pressure, wind speed, and send data back every 15 feet or so all the way to the ocean surface. All of that data goes to the National Hurricane Center and to modeling centers so they can get a better representation of the atmosphere.
One P-3 has a laser – a CRL, or compact rotational Raman LiDAR – that can measure the temperature, humidity and aerosols from the plane all the way down to the ocean surface. It can give us a sense of how juicy the atmosphere is, so how conducive it is to feeding a storm. The CRL operates continuously over the entire flight path, so you get this beautiful curtain underneath the plane that shows the temperature and humidity.
The planes also have tail doppler radars, which measure how moisture droplets are blowing in the air to determine how the wind is behaving. That gives us a 3D view of the wind field, like an X-ray of the storm. You don’t get that from a satellite.
We also launch ocean probes, called AXBTs (aircraft replaceable bathythermographs), ahead of the storm. These probes measure the water temperature at depths of several hundred meters. Normally, a surface temperature of 26.5 degrees Celsius (80 Fahrenheit) and above is favorable for a hurricane, but the depth of that heat is also important.
If you have warm ocean water that’s maybe 85 F at the surface, but 50 feet down the water is a lot colder, then the hurricane will mix that cold water pretty quickly and weaken the storm. But deep warm water, like we find in eddies in the Gulf of Mexico, provides extra energy that can fuel a storm.
We’re also testing a new technology: small drones that we can launch from the belly of a P-3. They have a wingspan of about 7 to 9 feet and are essentially a weather station with wings.
One of these drones dropped into the eye can measure pressure changes, which indicate whether a storm is getting stronger. If we could drop a drone into the eyewall and have it circle there, it could measure where the strongest winds are – that’s another important detail for meteorologists. We also don’t have a lot of measurements in the boundary layer, because it’s not a safe place to fly a plane.
You’ve also recently targeted the Cape Verde Islands off the coast of Africa. What are you looking for there?
Cape Verde is in the hurricane nursery of the Atlantic Ocean. The seedlings of hurricanes come from Africa and we are trying to determine the tipping points where these disturbances can develop into storms.
More than half of the storms we get in the Atlantic come from this nursery. And so do about 80 percent of the major hurricanes. So it’s important to know, even though the disruptions may precede the formation of a hurricane by seven to ten days.
In Africa, thunderstorms develop in the summer along the southern border of the Sahara Desert with the cooler, wetter Sahel region. The difference in temperature can create ripples in the atmosphere called tropical waves. Some of these tropical waves are precursors to hurricanes. However, the Saharan air layer – huge dust storms that roll off Africa every three to five days – can suppress a hurricane. These storms peak from June to mid-August. After that, tropical disturbances have a greater chance of reaching the Caribbean.
At some point, not too far in the future, the National Hurricane Center is going to have to do a seven-day forecast, instead of just five days. We’re working on how to improve that early forecast.
This article is republished from The Conversation, a nonprofit, independent news organization that brings you facts and reliable analysis to help you understand our complex world. It was written by: Jason Dunion, University of Miami
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Jason Dunion receives funding from NOAA, NASA, and the Office of Naval Research.