Tropical Storm Vance had maximum sustained winds near 70 mph on the night of Oct. 22 in the eastern Pacific, and the National Hurricane Center in Miami forecast that it would become a major hurricane by early Saturday, Oct. 24. The prediction came in a public advisory issued at 9:00 p.m. CST on Thursday, Oct. 22, which is 0300 UTC on Oct. 23, with the storm centered about 460 miles south-southwest of Acapulco, Mexico.
Save more, waste less: The Cool Down’s newsletter sends smart, simple changes that help you and the planet in your everyday life.
We may earn a commission if you sign up.
A forecast of this kind is a probability-weighted projection, not a record of what the storm has done, and the advisory itself carries no watches or warnings for Mexico. What it does include is a hazard that does not depend on landfall: swells generated by Vance that are expected to reach the coasts of southern and southwestern Mexico this weekend and to continue into the following week, a stretch of several days over which beach and boating conditions can stay hazardous even where the weather itself is calm.
The 9 p.m. CST advisory and what it forecasts
The NHC public advisory, number 7, places the center near 10.5 degrees north and 101.9 degrees west, moving northwest at about 6 mph, with a gradual turn toward the north-northwest expected over the next day or so. Minimum central pressure was estimated at 991 millibars, down from 1,000 millibars in the advisory issued at 3:00 a.m. CST on Oct. 22, when winds were 50 mph, and tropical-storm-force winds extended up to 105 miles from the center. Its forecast line reads that rapid intensification is expected and that Vance is forecast to become a major hurricane by early Saturday.
The advisory’s wording about the surf is direct: the swells are “likely causing life-threatening surf and rip current conditions” along the affected coast, and residents are told to follow local weather office products. No tropical storm or hurricane watch was in effect for any coastline at that time.
The intensity path, from 70 mph to 120 mph
The companion forecast discussion, number 7, written by NHC forecaster Gibbs, spells out the numbers. Vance was a 60-knot, 70-mph storm at 0300 UTC on Oct. 23, with a strengthening inner core and a growing central dense overcast on satellite imagery. The official forecast calls for 95 knots, or 110 mph, by 0000 UTC on Oct. 24, and a peak of 105 knots, or 120 mph, around 1200 UTC that morning, which is 6:00 a.m. CST on Saturday.
In the forecast reasoning, Gibbs cited warm sea-surface temperatures, low wind shear and abundant mid-level moisture, and noted that the statistical guidance gave a 65 to 80 percent chance of rapid intensification over the next 24 hours, well above normal. Weakening should begin around 60 hours as cooler water, possibly churned up by earlier storms, and stronger shear take hold. The forecast eases the storm to 90 knots by 0000 UTC on Oct. 26 and 85 knots, or 100 mph, by 0000 UTC on Oct. 28.
The threshold matters because the storm is forecast to cross it only narrowly. According to the NHC, hurricanes of Category 3 and higher are known as major hurricanes, with Category 3 starting at 111 mph, so the 110-mph forecast for Friday evening is just short of it and the 120-mph peak clears it by a small margin.
Track uncertainty and the view from Mexico
Forecast confidence is lower for the track than for the near-term intensity. The discussion says models agree well through about 60 hours and then diverge: some keep Vance farther offshore on a westward path, while others bring it north-northwest toward the southwestern and west-central Mexican coast. The official track follows the consensus aids closely, and the discussion lists the possibility of impacts on the Mexican coast after about day three as a key risk.
The Associated Press reported, via CP24, that Vance formed on Wednesday, Oct. 21, about 520 miles south of Acapulco with 40 mph winds, a gain of 30 mph in about a day. Mexican outlet Uno TV, in its report on the formation, said Guerrero state’s civil protection secretariat judged that the storm represented no danger for the state for the moment and that it was maintaining permanent watch, while the federal civil protection agency said the distance meant no effects on land for now.
Those statements pertained to the storm as it stood on Oct. 21, and the advisory was issued a day and a half later. The text of the advisory advises residents of the Mexican Pacific coast to consult local weather office products, and readers there should also look to the next NHC advisories, which are issued every six hours as complete products, and to Mexico’s national meteorological service, because both the intensity and the track in this forecast are expected to change as new data arrive.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
Save more, waste less: Subscribe to The Cool Down →
We may earn a commission if you sign up.
More from Morning Overview
- Hybrids have 15% fewer problems than gas cars, while EVs and plug-in hybrids have about 80% more, Consumer Reports finds
- Regulators cleared the first U.S. small modular reactor, 4 months early
- Lake Powell sank to a record 3,517 feet, nearing the level that stops Glen Canyon Dam’s turbines
- Seven of Earth’s nine planetary boundaries are breached, and all seven are worsening
