Before tropical cyclones can significantly strengthen, they generally must first become vertically aligned, with their rotating centers stacked through the atmosphere. New research using nearly three decades of NOAA Hurricane Hunter observations identifies four features that can help a tilted storm become aligned and more capable of intensifying.
Led by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science, its Cooperative institute for Marine and Atmospheric Studies, and colleagues at NOAA's Atlantic Oceanographic and Meteorological Laboratory, the study found that vertical alignment depends on a combination of storm structure, wind orientation and surrounding environmental conditions.
Rapidly intensifying storms can leave coastal residents and emergency managers with little time to prepare. A better understanding of these structural changes could help forecasters recognize when a disorganized tropical cyclone is more likely to strengthen, giving communities more time for evacuation decisions and other essential preparations.
"A tropical cyclone has to stand up straight before it can intensify," said Michael S. Fischer, the lead author and an assistant professor in the Department of Atmospheric Sciences at the Rosenstiel School. "Strong winds higher in the atmosphere can push the top of a storm's circulation away from the center near the ocean surface. Until those centers come back together, the storm usually cannot intensify substantially."
Four features that favor alignment
The study identifies four features that help explain whether a tilted tropical cyclone is likely to become vertically aligned: a tight circulation near the sea surface; a tilt that is favorably oriented relative to wind shear; stronger upward motion and heavier rainfall near the low-level center; and warm ocean water, abundant atmospheric moisture and relatively weak midlevel winds.
Meteorologists refer to the separation between a storm's lower- and middle-level circulation centers as "tilt." Vertical wind shear, or changes in wind speed or direction at different heights, can disrupt storm organization by pushing those centers out of alignment.
The researchers analyzed observations from the Tropical Cyclone Radar Archive of Doppler Analyses with Recentering, known as TC-RADAR, a database developed by Fischer and colleagues that contains 1,510 radar analyses collected by NOAA Hurricane Hunter aircraft during 28 hurricane seasons from 1997 through 2024.
"The storms that aligned already looked different about a day beforehand," said Fischer, who also is a core faculty member of the Frost Institute for Data Science and Computing, Earth Systems Science. "They had stronger, more tightly wound circulations near the surface and more widespread, vigorous thunderstorms lifting air near that center. Our findings suggest those thunderstorms are not simply a sign of organization. They may also help pull the storm's leaning circulation upright."
Because reconnaissance aircraft can measure low-level wind strength, storm size, thunderstorm coverage and tilt direction during operational missions, the findings also provide a way to test whether high-resolution hurricane models accurately reproduce the alignment process.
"Even a modest increase in forecast confidence a day earlier can provide more usable preparation time for communities in a storm's path," Fischer said. "This study gives us real-world evidence about what separates a storm that is becoming organized from one that remains tilted and less capable of strengthening."
up (left) with those that stay leaning (right). Aligning storms have a
stronger, more compact low-level circulation and more vigorous rising
air near the low-level center, which helps pull the tilted storm upright
The study, "To Align or Not to Align? That Is the Question," was published in the Journal of Geophysical Research: Atmospheres. In addition to Fischer, the authors are George R. Alvey III of the Cooperative Institute for Marine and Atmospheric Studies and NOAA's Atlantic Oceanographic and Meteorological Laboratory; Deelan Jariwala, who earned bachelor's degrees in meteorology and mathematics from the University of Miami in spring 2026; and Paul D. Reasor of NOAA's Atlantic Oceanographic and Meteorological Laboratory Hurricane Research Division.
The research was supported by the National Science Foundation under award No. 2241605.
