Scientists have spent nearly three decades watching tropical cyclones twist and turn, and now a new study has found a way to put that data to work, identifying four warning signs that a tilted storm is about to straighten up and gain strength. The lead author, Michael S. Fischer, keeps the explanation simple.
“A tropical cyclone has to stand up straight before it can intensify,” said Fischer, an assistant professor in the Department of Atmospheric Sciences at the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science. “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.”
The Data Behind the Study
Fischer and his team at NOAA’s Atlantic Oceanographic and Meteorological Laboratory conducted the study using data from 1997 to 2024, which spans 28 hurricane seasons and includes 1,510 Doppler radar readings taken by NOAA Hurricane Hunter aircraft.
Fischer developed TC-RADAR — the Tropical Cyclone Radar Archive of Doppler Analyses with Recentering — with his colleagues, and the team built it. The archive tracks how storms behave in real time, which matters greatly, since a tilted storm is disorganized and hard to read.
The Four Warning Signs
The Journal of Geophysical Research: Atmospheres published “To Align or Not to Align? That Is the Question,” and the four indicators it describes are easy enough to explain with plain language.
- A compact, tightly organized circulation close to the ocean surface.
- A storm tilt positioned favorably relative to vertical wind shear.
- Stronger rising air and heavier rainfall near the storm’s lower-level center.
- An environment that includes warm ocean water, plenty of atmospheric moisture, and relatively weak winds in the middle levels of the atmosphere.
The TC-RADAR Database
The TC-RADAR database is the engine of this research. It includes 1,510 radar analyses from 28 hurricane seasons, and it allows researchers to compare storms that eventually became aligned with those that remained tilted.
The strength of it rests on the fact that it comes from real flights — radar data collected by Hurricane Hunter aircraft as they flew into storms. That data thus reflects what a storm actually looks like at the moment.
With a large amount of data at hand, the team could observe patterns that would be difficult to notice otherwise.
How the Signs Work Together
Why the first sign matters is because a storm needs to be compact at the surface before it can organize above. The second sign, the tilt, is critical — a storm whose circulation centers are lined up vertically can intensify, but one whose centers are tilted away from each other cannot.
Changes in wind speed or direction with height define what is known as vertical wind shear. When that shear is strong, it can disrupt a cyclone’s structure by forcing the upper parts of its circulation to move away from the center, closer to the ocean surface.
The third sign, stronger rising air and heavier rainfall near the lower-level center, is where the thunderstorms become part of the story themselves. Fischer argues that these storms are not just a sign of organization — they may also help pull the storm’s circulation upright.
The fourth sign is the environment: warm ocean water, plenty of moisture, and weak winds in the middle levels of the atmosphere. These conditions supply the storm with the energy it needs to grow.
The Forecasting Context
During operational flights, NOAA reconnaissance aircraft gather the measurements highlighted by the study, including low-level wind strength, storm size, thunderstorm coverage, and the direction of a cyclone’s tilt. These observations could potentially help scientists determine whether high-resolution hurricane forecasting models accurately reproduce the physical process that allows tilted storms to become vertically aligned.
The study could offer forecasters more hints about which disorganized tropical cyclones are starting to take on a structure that favors becoming stronger.
Fischer says that even a slight rise in forecast confidence a day ahead still gives communities in a storm’s path more practical time to get ready.
Why Early Warning Helps
Such storms are among the most perilous in nature, capable of shifting from a tolerable hazard to a catastrophic one within hours, leaving coastal communities and emergency managers with scant time to react.
Forecasters who can spot earlier when a poorly organized tropical cyclone is turning more favorable for strengthening may gain the chance to give communities extra time for evacuation decisions and other preparations.
The People Behind the Research
Assistant Professor Fischer heads the Department of Atmospheric Sciences at the Rosenstiel School. He is also a core faculty member at the Frost Institute for Data Science and Computing, which implies his method relies heavily on data analysis rather than just physical observation.
The paper lists three authors beyond Fischer, and George R. Alvey III is one of them; he holds degrees in meteorology and mathematics, and he is affiliated with the Cooperative Institute for Marine and Atmospheric Studies and NOAA’s Atlantic Oceanographic and Meteorological Laboratory, and Deelan Jariwala, who earned bachelor’.
What the Data Shows
The research contrasts storms that eventually lined up with those that stayed tilted. The vast 28-season record gave the team enough data to spot patterns that would be difficult to see otherwise.
Fischer said the storms that aligned already showed differences about a day beforehand — they had stronger, more tightly wound circulations near the surface and more widespread, vigorous thunderstorms lifting air near that center. His conclusion is that these thunderstorms may be doing more than signaling organization — they may also be helping to pull the storm’s leaning circulation upright.
The Path Forward
Now that the findings have been made public and the numbers have appeared, the job ahead is for those who produce forecasts to begin drawing on the four signs in their everyday work. Since NOAA already gathers the readings, the groundwork needed to put this into practice is already in place.
Practical performance will ultimately determine whether the signs become a standard part of the forecast process. The research draws on nearly three decades of data, but only actual storms can provide the true test.
This study hands forecasters something they did not have. It is no crystal ball, but instead a means of interpreting the warning signs of a storm’s path. That counts as progress for a field that operates under constant strain.
The title, “To Align or Not to Align? That Is the Question,” sums up the stakes of the study. A storm that lines up can become stronger; one that does not align will remain tilted and less capable of intensifying.
| Sign | What It Shows |
|---|---|
| Compact circulation | A tightly wound circulation close to the ocean surface |
| Favorable tilt | A storm tilt positioned relative to vertical wind shear |
| Rising air and rainfall | Stronger rising air and heavier rainfall near the lower-level center |
| Environmental conditions | Warm water, moisture, and weak winds in the middle levels |
Source material: “Hurricane Hunters reveal 4 warning signs that a storm is about to strengthen,” ScienceDaily.
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