It was officially classified as Tropical Depression Twenty-E on September 25, at 06:00 UTC, located south-southwest of Manzanillo, Mexico. At the time of its formation, the depression was located within a favorable tropospheric environment of warm sea surface temperatures and minimal vertical wind shear, featuring a well-defined center of circulation under an expanding area of strong convection. The depression maintained a trend of steady strengthening over the 24 hours: it was upgraded to Tropical Storm Rosa six hours after being classified, and became the tenth hurricane of the season a day later, at 12:00 UTC on September 26. The NHC remarked that Rosa's structure was well developed at the middle levels of the troposphere, with distinct rainbands wrapped around the southern semicircle of the cyclone. The hurricane leveled in intensity for eighteen hours before proceeding into another phase of rapid intensification; it reached major hurricane status at 18:00 UTC on September 27, peaking in intensity with maximum sustained winds of and a minimum central pressure of . This made Rosa the seventh Category4 hurricane of the year's season. After Rosa reached its peak, the hurricane's eyewall – an inner ring of clouds around the eye, marked by high winds – began to warm considerably, signaling the start of an eyewall replacement cycle. Rosa turned to the northwest on the afternoon of September 28 in response to an approaching mid- to upper-level trough, which would continue to influence the remainder of the hurricane's development. Now tracking over cooler seas, Rosa steadily weakened down to Category 2 by 00:00 UTC, September 29, while undergoing its eyewall replacement. Once the replacement cycle was completed, the storm briefly restrengthened because of its much-improved structure, with expanding outflow to the northeast of the eye. However, Rosa began to experience impinging wind shear from the developing trough, causing a misalignment between the upper and lower levels of the hurricane, as well as coinciding with a final weakening phase. Rosa turned to the north on September 29, ahead of the trough. The unrelenting wind shear – combined with progressively cooler seas and drier air – quickly eroded Rosa's core, disrupting the eye and convection over the southern half of the hurricane. At 12:00 UTC on September 30, the diminishing hurricane dropped to Category1 while being steered towards the northeast between the trough and a subtropical ridge. Rosa lost its hurricane status twelve hours later, proceeding towards the