Steven R. Jayne, a scientist at the Woods Hole Oceanographic Institution, made a total of four flights into Hurricane Irma and Hurricane Jose so he could deploy instrumentation to better understand the storms’ dynamics.
Flying with the NOAA Hurricane Hunters, he launched ALAMO (air-launched autonomous micro-observer) floats into the water below to take water temperature, pressure and salinity measurements as a storm approaches and up to a year after it passes.
Early observations of the data so far explain why Jose weakened after Irma raged.
Dr. Jayne flew into Irma three times. He made the first trip when the storm was east of Antigua and Barbuda, the second when it was north of Puerto Rico, and the third when it was near Cuba.
Dr. Jayne said the ALAMO makes measurements 300 meters deep in the water column, moving up and down the column. As a hurricane passes it creates an internal wave below the surface that mixes the warmer top layers with the cooler water (called the cold wake) below.
Jose followed the same path as Irma, crossing over the same floats, Dr. Jayne said. The cooler water left in Irma’s wake provided less fuel for Jose, suggesting a reason for why this storm weakened to a tropical storm rather than strengthening, Dr. Jayne said.
“Irma had gone on the same path,” Dr. Jayne said. “The cold wake provided less fuel for Jose to live off of.”
Hurricane Maria, on the other hand, passed a couple of hundred miles away from Irma’s path, over warm waters, remaining strong as it hit the Caribbean.
“Maria was far left of Irma’s track,” Dr. Jayne said.
The floats also measured a freshwater layer on the ocean surface from the rain that Irma dropped. He said scientists will continue to dig into the data in the months ahead to learn more about these storms.
Dr. Jayne has been flying into hurricanes for five years, using the ALAMO to research the interactions between the ocean and atmosphere during a hurricane.
The ingredients for a strong storm are warm water to live off of; humid, moist air; and weak wind shears high in the atmosphere, he said. Strong shears will rip a storm apart.
He said ocean water temperatures are getting warmer, but scientists cannot say concretely that climate change is the cause of this strong hurricane season.
“There have been bad years before,” Dr. Jayne said.
However, this was the first time Dr. Jayne had flown into a category 5 storm, and he said Irma was the longest-lasting category 5 recorded.
He said that the rides were rougher, with more bounce, than weaker storms he has flown into. This strong storm also had some other characteristics not regularly seen, such as the stadium effect.
“In the eye it’s clear and you see clouds all around like in a giant stadium,” Dr. Jayne said.