In mid-September 2026, a tropical disturbance formed off the Pacific coast of Mexico, evolving into a tropical depression by September 20 and a tropical storm the following day. The system subsequently experienced a period of extreme rapid intensification, a technical designation for storms that increase wind speeds by at least 60 knots within 24 hours. By September 22, Polo’s maximum sustained winds had surged by 90 knots in a single day, reaching Category 5 status.

Gary Partyka, an atmospheric scientist at NASA’s Goddard Space Flight Center, described the event as “explosively rapid intensification,” noting that the storm benefited from an environment characterized by high moisture, atmospheric instability, and minimal wind shear. NOAA Hurricane Hunter aircraft measurements on September 22 estimated wind speeds near 285 kilometers per hour. Analysts suggest this makes Polo the fastest storm on record to transition from a tropical depression to a Category 5 hurricane, as well as one of the three strongest in the eastern Pacific by wind speed.

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Satellite imagery from NASA’s Aqua mission captured the storm on September 23 as it churned southwest of Acapulco. By that time, the system had weakened slightly to Category 4 strength following an eyewall replacement cycle. Kristen Corbosiero, an atmospheric scientist at the State University of New York at Albany, noted that the storm’s structure was supported by effective outflow and warm water temperatures. Sea surface temperatures in the region reached 32 degrees Celsius, significantly higher than the 27.8-degree threshold typically required for hurricane maintenance.

While the 2026 eastern Pacific season has seen elevated cyclone activity, experts caution against attributing Polo’s specific behavior solely to El Niño. Although large-scale circulation patterns associated with El Niño often increase regional storm frequency, similar rapid intensification events have occurred during La Niña and neutral conditions in the past. As of September 24, forecasters were monitoring the storm as it tracked through the Pacific, with potential movement toward Baja California expected in the following week.

Source: NASA