These flight patterns may look like boxes or stars, but they serve specific purposes for each storm.
Hurricane hunters don’t fly away from these storms like commercial airlines do. They fly right into them, but they don’t fly in and around the storms by accident. There is a method to madness.
There are two different groups of hurricane hunters, the National Oceanic and Atmospheric Administration (NOAA) and the US Air Force Reserve (USAF). Both organizations fly missions into tropical faults to record invaluable data for use by the National Hurricane Center (NHC) forecasters.
There are two main types of missions flown for the Hurricane Hunters, Fixed and Invest.
Fixed missions are for systems that meet tropical cyclone qualifications, such as tropical depressions, tropical storms, and hurricanes. The main goal is to mark the center of circulation, monitor wind speeds and pressure changes, as well as other variables that are difficult for satellites to measure in space.
For fixed missions, ‘Alpha’ is the most common flight pattern used to collect data in a tropical cyclone.
The cardinal points are the standard points on a compass: north, south, east, and west. Intercardinal directions are the diagonal points in between: northeast, southeast, southwest, and northwest.
Interestingly, the bigger, stronger storms tend to be the “easier” ones to fly.
â€œFrom my point of view as a meteorologist on board, the alpha pattern is theâ€œ easiest â€to fly. Since we usually fly these in stronger storms, there isn’t much doubt about where the storm center is, â€said DeHart. “The flights can be tough, of course, but at the end of the day we just fly through the storm center, collect the data and send it to NHC.”
The main objective of an investment mission is to determine whether a system meets the definition of a tropical cyclone; Storms that do not yet have a name or real tropical structural features.
For investment missions, the NHC often sends estimated coordinates of what it believes is the center of circulation that the missions target as their starting point.
However, invest missions naturally need to be a little more flexible with flight patterns, simply because there are so many unknowns in these types of storms.
“We never know what we’ll find, but we always have to think two or three steps ahead. So this really makes us have to think about meteorology.” [in each particular storm]”Said DeHart. â€œIs it a closed low or an open wave? Maybe it’s closed, but just extended? Is it fighting scissors? Are there several smaller eddies competing for the main center of circulation? Weak storms and investments can be very tricky and require a lot of thought. “
DeHart explains that the missions are ideal for the weaker, more uncertain storms. While the X pattern can be similar to the alpha pattern, it is flown at much lower altitudes, typically around 500 to 1,000 feet.
“As soon as a system becomes a tropical storm or hurricane, the hurricane hunters fly at higher altitudes, between 5,000 and 10,000 feet, depending on the severity of the storm,” said Jessica Kendziorek, director of public affairs operations at the USAF 403rd Wing.
The altitudes for the Delta and Box patterns are typically at or below 5,000 feet absolute.
â€œThe delta and box patterns are similar in that we fly around the periphery of the forecast center to see if we can observe winds in all four quadrants of the storm that would indicate a closed cycle. When we find a closed loop, we can walk confidently [find] the center; If not, we will continue the mission in ‘investment mode’, â€DeHart said.
NOAA focuses on research
Hurricane Hunters also fly a third type of mission that the Air Force rarely flies, according to DeHart, called synoptic missions.
For fixed missions, NOAA often flies a Figure 4, Rotated Figure 4 or Butterfly pattern.
“The patterns Butterfly and Figure 4 flown through the storm by the WP-3D are usually the ones that are used [find] the center of circulation “, said Jonathan Shannon, public affairs specialist for the NOAA Aircraft Operations Center Office of Marine and Aviation Operations.
The Rotated Figure 4 pattern is what it sounds like; the pattern in Figure 4 turned on its side.
“The goal of every flight is to collect data around the center of the storm, and these patterns allow us to fly efficiently through the different quadrants of a storm,” said Nick Underwood, NOAA Hurricane Hunter. “These data help predict the intensity of a storm and pinpoint where the center is.”
Investment missions flow the lawnmower and square spiral patterns to see if tropical features are indeed associated with the area in which they are being studied.
“The lawnmower pattern allows us to map a large area when we don’t have a center to target,” said Paul Flaherty, director of science at NOAA’s Aircraft Operations Center. “Once we are able to map a full circulation (usually by finding a westerly wind) we will move back to Figure 4 based on this newly identified center position.”
The Square Spiral Pattern is a survey mission designed to provide observations on the structure and properties including information on the vortex center, if any.
There is a unique third type of mission flight pattern that is widely used to study the surrounding atmosphere that helps forecasters determine the likely direction of the storm.
The star pattern focuses on a scan of the outer edges of the system. The closely related Star-2 pattern also makes an outer span of the system while also adding a circumferential loop near the center of circulation.
Recently, NOAA’s Gulfstream IV flew a Star-2 pattern around Hurricane Larry to study the storm’s runoff patterns and better determine where the storm was going.
“The flight pattern that you typically see from our Gulfstream IV is a circumnavigation of the storm itself and a sample of the atmosphere around and before the storm,” said Underwood. “These data help predict the storm trajectory.”
Regardless of which entity is flying, the operational missions are the backbone of the National Hurricane Center, tasked with providing life-saving information about a storm.
The NHC takes the data and uses it to provide guidance and advice to the public so that people know whether Elsa or Ida or Nicholas are still tropical storms or hurricanes.