Hurricane Polo underwent explosive intensification in the eastern Pacific in late September 2026, reaching Category 5 status in less than 24 hours. The storm originated as a tropical disturbance off Mexico's Pacific coast in mid-September and became a tropical depression on September 20, followed by tropical storm status on September 21.

By September 22, Polo's maximum sustained winds increased by 90 knots (167 km/h or 104 mph) within a single day, meeting the technical definition of extreme rapid intensification. The National Hurricane Center described the strengthening as "truly remarkable" in its advisory discussions. NOAA's Hurricane Hunter aircraft measured winds near 285 km/h (180 mph) on that date, placing Polo among the strongest eastern Pacific storms on record.

Meteorologists noted that Polo developed in an environment with favorable conditions for intensification: low wind shear, high moisture, warm ocean temperatures, and high atmospheric instability. Sea surface temperatures in the region reached 32°C (90°F), approximately 2-3 degrees above the 2003-2014 average for late September. The storm passed over waters with high ocean heat content, which likely contributed to its sustained strength.

Satellite imagery captured on September 23 showed a large, clear eye and extensive outflow pattern as Polo churned off Guerrero, southwest of Acapulco. At that time, it maintained Category 4 intensity with winds of 230 km/h (145 mph), having recently completed an eyewall replacement cycle that caused a temporary weakening.

Experts cautioned against directly linking Polo's development to El Niño, though the broader regional context featured above-average tropical cyclone activity. Colorado State University data indicated the accumulated cyclone energy in the eastern Pacific was nearly double the seasonal norm as of September 24. The storm was expected to remain over the Pacific through the following week, with potential for a northeastward trajectory toward Baja California.

NASA Earth Observatory documented Polo's evolution using MODIS satellite imagery and sea surface temperature data from the Multiscale Ultrahigh Resolution (MUR) project. Researchers emphasized that while warm surface waters were a factor, the depth of ocean heat also played a role, with minimal cooling observed in the storm's wake.

Forecasters monitored Polo's progression using NASA's Worldview browser and GMAO's FLUID tool. The storm's rapid intensification occurred without direct attribution to El Niño conditions, though the overall seasonal activity aligned with patterns observed during El Niño events.