Hurricane Polo's Explosive Intensification Off Mexico Coast Sets Record for Eastern Pacific Basin - Rapid Intensification Study

According to NASA Technology, a combination of environmental factors off the Pacific coast of Mexico led to the formation of one of the most powerful storms the eastern Pacific basin has witnessed, with maximum sustained wind speeds reaching nearly 285 kilometers per hour. This study was published in the Monthly Weather Review, 154(10), 2133-2149. In mid-September 2026, Hurricane Polo began as a tropical disturbance near the Mexican coast, as documented in the Monthly Weather Review, 154(10), 2133-2149. By September 20, it had organized sufficiently to be classified as a tropical depression, and the following day, it became a tropical storm.

Polo experienced a phase of what atmospheric scientist Gary Partyka of NASA’s Goddard Space Flight Center described as explosively rapid intensification. Partyka stated that the storm was situated in an environment considered "near perfect" for strengthening, which included high moisture, warmer ocean temperatures, weak wind shear, and substantial atmospheric instability.

Observers noted the extreme rapid intensification, which is technically defined as a storm's wind speeds increasing by at least 60 knots (111 kilometers or 69 miles per hour) within a 24-hour period. By September 22, the storm's maximum sustained wind speed had increased by 90 knots (167 kilometers per hour or 104 miles per hour) over a 24-hour span, reaching category 5 status. When NOAA's Hurricane Hunter aircraft surveyed the storm on September 22, researchers estimated winds approaching 285 kilometers (180 miles) per hour. Some analysts indicated this made it the third strongest storm ever recorded in the eastern Pacific by maximum sustained winds and the fastest to advance from a tropical depression to a category 5 storm.

On the afternoon of September 23, an image captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Aqua satellite showed Polo churning off the coast of Guerrero, southwest of Acapulco. At the time of the image acquisition, the storm was category 4 strength with maximum sustained winds of 230 kilometers (145 miles) per hour, having experienced an eyewall replacement cycle that caused a slight weakening.

Kristen Corbosiero, an atmospheric scientist at the State University of New York at Albany working on a NASA project utilizing satellite data to study tropical cyclone ventilation, commented that the satellite imagery showed Polo's large, clear eye and extensive outflow pattern. She added that weak winds above the system and good outflow at the top of the system also contributed to Polo's rapid intensification.

As Polo developed, it moved over areas where sea surface temperatures reached as high as 32 degrees Celsius (90 degrees Fahrenheit), which was 2 to 3 degrees warmer than usual for September 23. Surface waters across much of the region were above 27.8°C (82°F), which is the temperature generally needed to sustain and intensify hurricanes.

The map provided, which is based on data from NASA’s Jet Propulsion Laboratory’s Multiscale Ultrahigh Resolution Sea Surface Temperature (MUR SST) project, illustrates temperature anomalies—how much warmer or cooler the ocean surface was on September 23, 2026, compared to the project's 2003-2014 average for that date. Corbosiero also mentioned that the presence of warmer water deeper in the water column likely aided the storm's endurance. She noted that while hurricanes can sometimes churn up cooler deep water that slows intensification, the cool water wake behind Polo appeared minimal, and measurements and models indicated high ocean heat content at significant depths.

Both Partyka and Corbosiero advised against directly linking Polo's rapid intensification to the unusually warm surface temperatures associated with El Niño in the central and eastern Pacific Ocean. Corbosiero pointed out that other hurricanes in this region have intensified rapidly during La Niña and neutral conditions, citing Hurricane Otis in 2023 and Patricia in 2015 as examples of category 5 storms. Nevertheless, the overall level of tropical cyclone activity in the eastern Pacific typically increases during El Niño due to shifts in large-scale atmospheric and oceanic circulation patterns, which has been observed in 2026. Data from Colorado State University indicated that as of September 24, the accumulated cyclone energy in the region was nearly double the typical amount.

Individuals interested in tracking sea surface temperature anomalies or other storm aspects can utilize NASA's Worldview browser, a near real-time data viewer from the Short-term Prediction Research and Transition (SPoRT) project, and the FLUID tool from GMAO. Forecasters anticipate that Polo will remain over the Pacific until next week, at which point it might turn toward the northeast and head toward Baja California.