Hurricane Polo intensified by 90 kt in 24 hours and reached Category 5

The US National Hurricane Center called the 24-hour, 90-kt increase “truly remarkable”; aircraft analysis later put Polo briefly at 180 mph with a 892-hPa centre.

At the 24 September 8 p.m. MST checkpoint it was a 150-mph Category 4 moving west offshore, and both intensity and track could still change.

How large was 90 kt

One knot is 1.852 km/h, so the daily increase was about 167 km/h. That is three times the NHC rapid-intensification threshold of 30 kt in 24 hours. The operational estimate may be adjusted in post-season analysis.

Why did intensity fluctuate

Powerful hurricanes can form an outer eyewall that replaces the inner one. Peak winds may temporarily ease while the wind field expands. Dropping from Category 5 to 4 therefore reflected structural change, not instant disappearance.

Hazards for Mexico

The centre was expected to remain offshore, but outer rainbands affected Guerrero, Michoacán, Colima and Jalisco. Authorities prepared for flooding, landslides, rising rivers and dangerous surf. Offshore centres can still cause damage.

What the category omits

The Saffir–Simpson scale uses one-minute maximum sustained wind. It does not combine rainfall, flooding, landslides or waves, so crossing the 157-mph Category 5 line does not switch those hazards on or off.

Forecasts move

The latest 24 September display showed Polo heading west away from the coast while allowing renewed strengthening. This article cannot replace local evacuation advice; NHC, Conagua and civil-protection alerts take priority.

Next checks

NHC issues regular advisories and intermediates. Track wind radii, rainfall, waves, landslide alerts and local orders together. Final peak intensity will be reanalysed in the post-season cyclone report.

Primary sources and independent checks

Official release: NHC rapid-intensification discussion

Earlier official research plan: NHC Polo advisory archive

Independent report: Mexico Conagua advisory

Additional official source: AP independent report

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