As a hurricane intensifies, hurricane hunters are in the sky doing something almost unimaginable: flying through the eye of the storm. With each pass, scientists aboard these planes take measurements that satellites can’t and send them to meteorologists at the National Hurricane Center.
Jason Dunion, a Meteorologist at the University of Miami, led hurricane field programs for the National Oceanic and Atmospheric Administration. He described the technology the team uses to assess hurricane behavior in real time and the experience aboard a P-3 Orion while diving through the eyewall of a hurricane.
What happens aboard a hurricane hunter when you encounter a storm?
Basically, we’ll take a flying laboratory into the heart of the hurricane, down to Category 5. As we fly, we process data and send it to meteorologists and climate modelers.
At the P-3, we routinely walk through the middle of the storm, right into the eye. Photograph a pattern – we kept going through the storm several times during a mission. They could be developing storms or they could be Category 5.
We typically fly at an altitude of about 10,000 feet, about a quarter of the way from the surface of the ocean to the top of the storm. We want to get through the hardest part of the storm because we are trying to measure the strongest winds to the Hurricane Center.
This has to be intense. Can you describe what scientists are experiencing on these flights?
My most intense flight was Dorian in 2019. The storm was near the Bahamas and rapidly intensifying to a very strong Category 5 storm, with winds around 185 mph. It seemed like a feather in the wind.
When we were passing Dorian’s eyewall, it was all seat belts. You can lose a few hundred meters in a few seconds if you have a downdraft, or you can hit an updraft and gain a few hundred meters in a matter of seconds. It’s a lot like a roller coaster ride, except you don’t know exactly when the next climb or descent is coming.
At one point we had G-forces of 3 to 4 Gs. This is what astronaut experience during a rocket launch. We can also get zero G for a few secondsand anything that is not tied down will float.
Even in the most difficult phases of the storm, scientists like me are busy on computers working on the data. A technician in the back may have dropped a probe from the belly of the plane, and we are checking the quality of the data and sending it to modeling centers and the National Hurricane Center.
What are you learning about hurricanes on these flights?
One of our goals is to better understand why storms intensify quickly.
Rapid intensification occurs when a storm increases in speed by 35 mph in just one day. This is the equivalent of going from a Category 1 storm to a large Category 3 storm in a short period of time. Departure (2021), Dorian (2019) and Michael (2018) are just a few recent hurricanes that have rapidly intensified. When this happens close to land, it can catch people unprepared and it becomes dangerous quickly.
Since rapid intensification can happen in a very short space of time, we have to be out there with the hurricane hunters taking measurements as the storm forms.
So far, rapid intensification is difficult to predict. We might start to see the ingredients come together quickly: Is the ocean warm at great depth? Is the atmosphere nice and juicy, with lots of moisture surrounding 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 basic insight, but we need to get our hurricane hunters into the storm itself to actually pick apart the hurricane.
What does a thunderstorm look like when it intensifies quickly?
Hurricanes like to stay upright – think of a spinning top. So one thing we look for is alignment.
A storm that is not yet fully formed may have a low-level circulation a few kilometers above the ocean that is not aligned with its mid-level circulation 6 or 7 kilometers above. This is not a very healthy storm. But a few hours later, we will be able to fly back into the storm and notice that the two centers are more aligned. This is a sign that it could intensify quickly.
We also look at boundary layer, the area just above the ocean. Hurricanes breathe: They take in air at low levels, the air rises up the eyewall, and then is expelled at the top of the storm and away from the center. This is why we have huge updrafts in the eyewall.
Therefore, we can look at our dropsonde radar or tail doppler data to know how the winds are flowing in the boundary layer. Could it be that really moist air is moving toward the center of the storm? If the boundary layer is deep, the storm can also breathe further.
We also look at the structure. Many times the storm looks healthy on the satellite, but we get on radar and the structure is sloppy or the eye may be full of clouds, which tells us the storm is not yet ready to intensify rapidly. But during this flight, we may start to see the structure change very quickly.
Air moving in, rising and leaving – breathing – is a great way to diagnose a thunderstorm. If this breathing appears healthy, it could be a good sign of an intensifying storm.
What instruments do you use to measure and predict hurricane behavior?
We need instruments that measure not just the atmosphere but also the ocean. Winds can drive a storm or destroy it, but the ocean’s heat and moisture are its fuel.
We use dropprobes to measure temperature, humidity, pressure and wind speed, and send data every 15 feet or so to the ocean surface. All of this data goes to the National Hurricane Center and modeling centers so they can get a better representation of the atmosphere.
A P-3 has a laser – a CRL, or Compact Rotational Raman LiDAR – which can measure temperature, humidity and aerosols from the aircraft to the ocean surface. It can give us an idea of how juicy the atmosphere is and how conducive it is to fueling a storm. The CRL operates continuously throughout the entire flight path, so you get this beautiful curtain below the aircraft showing the temperature and humidity.
Planes also have tail doppler radars, which measure how moisture droplets in the air are blowing to determine how the wind is behaving. This gives us a 3D view of the wind field, like an X-ray of the storm. You can’t get that from a satellite.
We also launched ocean probes called AXBTs – aircraft disposable bathythermograph – ahead of the storm. These probes measure water temperatures hundreds of meters deep. Typically, a surface temperature of 26.5 degrees Celsius (80 Fahrenheit) or higher is favorable for a hurricane, but the depth of that heat is also important.
If you have warm ocean water, perhaps 85 F at the surface, but just 50 feet deep the water is a little cooler, the hurricane will mix with the cold water very quickly and weaken the storm. But deep, warm waters, as we find in whirlpools in the Gulf of Mexico, it provides extra energy that can power a storm.
We’re also testing new technology – small drones that we can launch from the belly of a P-3. They have wingspans of about 7 to 9 feet and are basically a weather station with wings.
One of these drones launched into the eye could measure pressure changes, which indicate whether a storm is getting stronger. If we could put a drone on the eyewall and put it in orbit there, it could measure where the strongest winds are – that’s another important detail for meteorologists. We also don’t have many measurements in the boundary layer because it’s not a safe place for a plane to fly.
It also recently targeted the Cape Verde Islands off Africa. What are you looking for there?
The Cape Verde Islands are in the hotbed of Atlantic hurricanes. The seeds of hurricanes come from Africa and we are trying to determine the critical points for these disturbances to turn into storms.
More than half of the named storms we have in the Atlantic come from this nursery, including about 80% of major hurricanesso it’s important, even though disturbances occur perhaps seven to 10 days before a hurricane forms.
In Africa, many thunderstorms develop along the Sahara Desert’s southern border with cooler regions, humid Sahel region in the summer. The temperature difference can cause the development of ripples in the atmosphere that we call tropical waves. Some of these tropical waves are precursors to hurricanes. However, the Sahara air layer – huge dust storms that occur in Africa every three to five days or so – can suppress a hurricane. These storms peak from June to mid-August. After that, tropical disturbances have a better chance of hitting the Caribbean.
At some point not too far in the future, the National Hurricane Center will have to issue a seven-day forecast instead of just a five-day forecast. We are figuring out how to improve this advance prediction.
This article was republished from The conversation, an independent, nonprofit news organization that brings you trusted facts and 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.
