Those seemingly random flight patterns may look like boxes or stars, but they serve specific purposes for each individual storm.
Hurricane hunters do not fly away from these storms like commercial airlines. They fly directly into them, but they don’t fly randomly into and around the storm. There is a way to madness.
There are two distinct groups of hurricane hunters, the National Oceanic and Atmospheric Administration (NOAA) and the US Air Force Reserve (USAF). Both organizations fly missions into tropical disturbances to record invaluable data to be used by forecasters at the National Hurricane Center (NHC).
For Hurricane Hunters, there are two main types of mission flows, fixed and investment.
Fixed missions are named for systems that meet tropical cyclone qualifications, such as tropical depressions, tropical storms and hurricanes. The main purposes are to characterize the center of circulation, to monitor changes in wind speed and pressure, and other variables that are difficult for satellites in space to measure thoroughly.
For fixed missions, ‘alpha’ is the most common flight pattern used to collect data in a tropical cyclone.
The cardinal directions are the standard points on the compass: north, south, east, and west. The intercardinal directions are the diagonal points in the middle: northeast, southeast, southwest, and northwest.
Interestingly, larger, stronger storms are “easier” to blow into.
“From my perspective as an onboard meteorologist, the alpha pattern is the “easiest” to fly. Because we usually fly on strong storms, there’s not a lot of question about where the storm center is,” DeHart said. . “The flights can certainly be tough, but at the end of the day we just fly through the storm center, collect the data, and send it to the NHC.”
The primary objective of an investment mission is to determine whether a system meets the definition of a tropical cyclone; Hurricanes that do not yet have a name or an actual tropical structure feature.
For investment missions, the NHC will often send projected coordinates of where they believe the center of circulation is, where the missions will aim for their starting point.
However, investment missions by nature have to be a bit more flexible to flight patterns, as there are so many unknowns with these types of storms.
“We never know what we’re going to find, yet we always have to think two or three steps ahead. So really we need to think about meteorology [in each particular storm],” DeHart said. “Is this a closed low or an open wave? Maybe it’s closed but just tall? Is it struggling with shear? Are there many smaller swirls competing to be the main circulation center? Weak storms and investments can be very difficult and require a lot of thought from us.”
DeHart explains that the missions are ideal for weaker, more uncertain storms. While the X pattern may be similar to the Alpha pattern, it is flown at much lower altitudes, typically around 500 to 1,000 feet.
“Once a system becomes a tropical storm or hurricane, hurricane hunters begin flying at altitudes of 5,000 to 10,000 feet, depending on the severity of the storm,” said Jessica Chief of Public Affairs Operations with the USAF 403rd Wing Kendziorek said.
Flight levels for delta and box patterns are typically at or below 5,000 feet of absolute altitude.
“The delta and box patterns are similar in that we would fly around the perimeter of the forecast center, seeing if we could observe winds in all four quadrants of the storm that would indicate a closed circulation. If we found a closed circulation so we can confidently go [find] middle of; If not, we will continue the mission in ‘investment mode’,” DeHart said.
NOAA focuses on research
According to DeHart, Hurricane Hunters also fly a third type of mission, which the Air Force rarely flies, called synoptic missions.
For fixed missions NOAA often flies the Figure 4, swirling Figure 4 pattern, or butterfly pattern.
“Butterfly blown through by the storm by WP-3D and Figure 4 patterns are commonly used [find] center of circulation said Jonathan Shannon, public affairs specialist for the NOAA Aircraft Operations Center Office of Marine and Aviation Operations.
Rotated Figure 4 The pattern is as it appears; Figure 4 Pattern turned to the side.
“The goal with every flight is to gather data around the center of the storm, and those patterns allow us to fly efficiently through the different quadrants of the storm,” said Nick Underwood, NOAA Hurricane Hunter. “This data helps to predict hurricane intensity, as well as determine where the center is.”
For investment missions, lawnmowers and square spiral patterns are flown to determine whether there are true tropical features associated with the area they are investigating.
“The lawnmower pattern allows us to map a large area even when we don’t have a center to target,” said Paul Flaherty, the science branch chief of NOAA’s Aircraft Operations Center. “Once we are able to map out an absolute circulation (usually by finding a westerly wind), we will return to Figure 4 based on that newly identified center position.”
Square Spiral Patterns is a survey mission intended to supply observations on the structure and characteristics, including information about the vortex center, if it exists.
A unique third type of mission is the flight pattern, which is often used to sample the surrounding atmosphere to help forecasters know in which direction a storm is likely to move.
The star pattern focuses on scans of the outer edges of the system. The closely related STAR-2 pattern also spans the system’s outer span, while also adding in a circumferential loop near the center of circulation.
Recently, NOAA’s Gulfstream IV flew a STAR-2 pattern around Hurricane Larry to examine outflow patterns from the storm and better determine where the storm was headed.
“Generally the flight pattern you’ll see from our Gulfstream IV is a circulation of the storm, as well as a sample of the atmosphere around and beyond the storm,” Underwood said. “This data helps to predict the track of the storm.”
No matter which unit is flying, operational missions are the backbone for the National Hurricane Center, which is tasked with providing essential life-saving information about hurricanes.
The NHC takes the data and uses it to issue guidance and advice to the public, so people know whether Elsa or Ida or Nicolas are still tropical storms or have become hurricanes.
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