Hurricane Polo climbed to Category 5 in under 24 hours over record-warm Pacific water
The Met Office's Julian Heming credits this year's record El Nino for the ocean heat beneath the storm. Rapid intensification happens several times a year worldwide, and the two published accounts differ on Polo's peak winds.
The Scientist · Science desk
What happened
- Live Science reported that Polo went from a tropical storm to a Category 5 hurricane in less than 24 hours on Tuesday, 22 September, with winds reaching 180 mph.
- AFP's account of the same storm puts the climb at Category 1 to Category 5 inside a day, with sustained winds of 160 mph and further strengthening still forecast.
- By Wednesday, 23 September, the National Hurricane Center had downgraded Polo to Category 4 while still calling it "a very powerful major hurricane".
- The NHC does not predict a direct landfall, and warned that heavy rain may produce life-threatening flooding and mudslides along with extremely hazardous ocean conditions.
- Mexican authorities suspended classes in Pacific coast states including Guerrero and Michoacan, the first in line for the heavy rain.
Why it matters
- What doesn't add up contradiction Anyone reconstructing Polo's intensification rate from the coverage gets a different answer depending on the publisher, because the accounts differ both on the peak wind and on the category the storm started from.
- What it limits constraint A single storm cannot carry the El Nino attribution when rapid intensification already happens several times a year worldwide; the test needs event counts compared across El Nino and neutral seasons.
- Who's exposed exposure An offshore core spares Mexico's Pacific coast an eyewall but not the rainfall, so the flooding and mudslide exposure holds even if the forecast track never touches land.
- What it sets up precedent If the WMO is right that this El Nino runs to at least February 2027, the warm background under the eastern Pacific stays in place well past the end of this hurricane season.
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Julian Heming, an environmental scientist at the UK Met Office, gave Live Science the ingredient list by email. "The main requirements are high sea temperatures, low wind shear and upper air conditions which allow air to escape quickly from the top of the hurricane," he said [7]. Polo had all of them. Heming said the unusually warm ocean supplied abundant heat and moisture, while very moist air and weak winds higher in the atmosphere let thunderstorms organize and strengthen without being disrupted [9]. The storm also built a compact, well-defined core that concentrated its energy into a relatively small area [10].
On cause he was less guarded. Polo's rapid and sudden growth is testament to the dominance of this year's so-called super El Nino, Heming said, an El Nino that set a record on Monday as the most extreme on record and has amplified a number of extreme weather events globally [21]. In the same email he put the global rate of rapid intensification at "several times per year across the globe" [8]. One storm over hot water is consistent with the El Nino explanation and also consistent with that base rate. Separating the two takes a count of rapid intensification events in El Nino seasons against neutral ones.
NOAA identifies El Nino conditions when the eastern tropical Pacific sits at least 0.5 degrees Celsius above average, alongside matching changes in winds, surface pressure and rainfall [17]. "Super El Nino" is not a scientific term; it describes warming above 2 C [18], four times the level at which NOAA declares an event [19].
The two accounts of Polo disagree on more than wording. The 20 mph gap between the peak wind figures is consistent with readings taken hours apart, since AFP reported the storm was still forecast to strengthen [16]. The starting point is a harder problem: a climb from tropical storm strength and a climb from Category 1 are not the same rate across the same 24 hours.
For an emergency manager the useful measure is the gap between the hour the NHC first forecast Category 5 and the hour Polo got there, and neither account reports it. Local alerting did begin before the jump. On Monday, authorities in Acapulco used megaphones on the beaches and avenues to broadcast warnings of possible thunderstorms [14], urging people to take "preventive measures at home or at work, checking safety conditions in your home and locating your nearest temporary shelter" [15]. Acapulco was devastated by Hurricane Otis in 2023 [6].
Where the storm goes is still open. "There is currently a lot of uncertainty in the long term as to whether Polo will move further out to sea or turn north-eastwards towards Mexico," Heming said [11].
What to watch
- A post-season best track from the National Hurricane Center would fix Polo's peak intensity and the category the 24-hour climb began from.
- Measured rain totals and mudslide reports along Mexico's southwest coast over the coming days.
- Whether the system tracks far enough north to bring rain, rip currents and large swells to Southern California.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence74
- Adoption
- Not scored
- Hype gap+25
- Incentives
- Not scored
- Confidence70
Perspective Coverage
3 publishers- Builder
- Builder 45%
- Operator
- Operator 47%
- Investor
- Investor 8%
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Live Science reported that a Pacific cyclone named Polo went from a tropical storm to a Category 5 hurricane in less than 24 hours on Tuesday, Sept. 22, with winds reaching 180 mph (290 km/h).
- [2]
AFP reported that Polo intensified from Category 1 to Category 5 on the Saffir-Simpson scale in less than 24 hours, with sustained winds of 160 mph (260 kph), and was expected to strengthen further.
- [3]
The National Hurricane Center said in an update on Wednesday, Sept. 23, that Polo had been downgraded to a Category 4 storm but remained "a very powerful major hurricane".
- [4]
The NHC said: "The core of Polo is expected to be near the coast of southwestern Mexico during the next few days, although forecast to remain offshore."
- [5]
Although Polo was not predicted to make direct landfall, the NHC warned that heavy rain may produce life-threatening flooding and mudslides as well as extremely hazardous ocean conditions.
- [6]
Acapulco was devastated by Hurricane Otis in 2023.
- [7]
Julian Heming, an environmental scientist and researcher at the UK Met Office, told Live Science in an email: "The main requirements are high sea temperatures, low wind shear and upper air conditions which allow air to escape quickly from the top of the hurricane."
- [8]
Heming said: "Rapid intensification of tropical cyclones is something we see several times per year across the globe."
- [9]
Heming said the unusually warm ocean supplied Polo with abundant heat and moisture, while very moist air and weak winds higher in the atmosphere allowed thunderstorms to organize and strengthen without being disrupted.
- [10]
Polo developed a compact, well-defined core, which concentrated the storm's energy into a relatively small area and enabled it to intensify extremely quickly.
- [11]
Heming said: "There is currently a lot of uncertainty in the long term as to whether Polo will move further out to sea or turn north-eastwards towards Mexico."
- [12]
If the system moves northward, Southern California could see intense rainfall and coastal regions may experience hazardous rip currents and large swells.
- [13]
Classes were suspended in Mexican Pacific coast states including Guerrero and Michoacan, the first to be hit by heavy rain.
- [14]
On the beaches and avenues of Acapulco, in Guerrero, authorities used megaphones on Monday to broadcast messages about possible thunderstorms in the area.
- [15]
The Acapulco broadcasts urged: "We recommend taking preventive measures at home or at work, checking safety conditions in your home and locating your nearest temporary shelter."
- [16]
The two published peak wind figures for Polo differ by 20 mph: 180 mph in Live Science's account and 160 mph in AFP's.
- [17]
The National Oceanic and Atmospheric Administration identifies El Nino conditions when eastern tropical Pacific waters are at least 0.5 degrees Celsius (0.9 degrees Fahrenheit) above average, alongside changes in winds, surface pressure and rainfall consistent with the phenomenon.
- [18]
"Super El Nino" is not a scientific term; it refers to a very strong El Nino in which the warming of sea surface temperatures is higher than 2 C above normal.
- [19]
Warming above 2 C, the informal marker for a "super" El Nino, is four times NOAA's 0.5 C threshold for declaring El Nino conditions.
- [20]
Polo intensified rapidly as it moved over exceptionally warm Pacific waters associated with an extremely strong "super" El Nino that has taken hold off the Pacific since June.
- [21]
Heming said: "Polo's rapid and sudden growth is testament to the dominance of this year's so-called super El Nino, which set a record on Monday as the most extreme on record and has amplified a number of extreme weather events globally."
- [22]
The latest data from the World Meteorological Organization suggests the current El Nino could be the strongest on record and last until at least February 2027, leading to more extreme weather, pushing some areas into drought while others experience stronger storms, rainfall and flooding.
Sources
3 independent publishers whose own reporting we read for this story.
- livescience.comHow did Hurricane Polo get so powerful?
1 article · September 23, 2026
- nasa.govExplosive Intensification for Hurricane Polo
1 article · September 24, 2026
- phys.orgHurricane Polo strengthens to top Category 5 off Mexico
1 article · September 22, 2026
Topics and entities
Topics
- Tropical cyclone rapid intensification
- Eastern Pacific hurricanes
- El Nino