Isaias Came Within Hours of 1905's Latest-First-Hurricane Record

The Gulf under Isaias is as warm as it has ever been this deep into autumn: 30–31°C (86–88°F) along the storm's path, "the warmest on record for this point in October," according to Jeff Masters and Bob Henson of Yale Climate Connections. And still the Atlantic needed until 10:30 p.m. CDT on Wednesday, Oct. 7, to make its first hurricane of 2026, when dropsonde data from an Air Force Reserve hurricane hunter showed 75 mph sustained winds and the National Hurricane Center upgraded the storm.

That puts Isaias almost on top of the oldest late-start record in the books. In the UTC convention NHC's records use, the upgrade came at 0330 UTC on Oct. 8, while the hurricane center's best-track database logs 1905's first hurricane at 0000 UTC the same day, three and a half hours earlier. Whether 2026 ends up tied with 1905 or a close second will be settled in NHC's post-season best track, not this week.

As of the hurricane center's 4 a.m. CDT advisory Thursday, Oct. 8, Isaias had 80 mph winds about 420 miles south-southwest of the mouth of the Mississippi River, with a Hurricane Warning from Ocean Springs, Mississippi, to the Bay/Gulf County Line in Florida and landfall expected late Friday or early Saturday. The 128-day wait for it (129 days counted in UTC, as the chart below does) and the tropical storm forecast to approach Southern California this weekend trace to an El Niño that is still strengthening and that the Climate Prediction Center gives a better than 90% chance of becoming very strong. Shear, the brake El Niño applied all season, is also the biggest unknown at the coast, though this week's comes from a trough over the central United States.

The clock explains why headlines disagree. On Central time the upgrade fell on Oct. 7, so the Associated Press, which cited the National Weather Service for the 1905 date, wrote that Isaias "was short by one day of tying a 121-year-old record." Measured the way the record is kept, the gap is hours. The caveat: best-track entries sit at six-hour synoptic times, Isaias's figures are operational, and NHC re-analyzes every storm after the season.

Behind 1905, the next-latest first hurricane came in 1941, on Sept. 21, and two years, 1907 and 1914, never produced one at all. The modern-era mark belonged to Gustav in 2002 and Humberto in 2013, whose first best-track hurricane entries fall at 1200 UTC on Sept. 11, the latest since 1941. Isaias beat that pair by 26 days and 15.5 hours, which is why Masters and Henson called it "the latest first-forming Atlantic hurricane in reliable records by a wide margin." Against NHC's 1991–2020 average first hurricane of Aug. 11, it came 57 days late by the local calendar, close to two months.

Brakes in the sky, fuel in the water

A hurricane draws its energy from warm water, but only if its thunderstorms stack straight up. Vertical wind shear, the change in wind speed and direction with height, tilts those towers and pulls their tops off their bases.

El Niño, a warming of the central and eastern equatorial Pacific, has been manufacturing that shear. The NOAA Climate Prediction Center reported on Sept. 10 that the key Niño-3.4 region ran +1.8°C above normal in August, with eastern anomalies above +3.0°C, and gave a "greater than 90% chance of a very strong event." Its next update was scheduled for Thursday.

NOAA's Atlantic Oceanographic and Meteorological Laboratory spells out the chain: El Niño "generally lessens hurricane activity in the Atlantic Ocean via increased vertical wind shear across the region, making it harder for thunderstorms to organize into hurricanes." That influence "generally becomes more evident during the latter portion of the hurricane season, specifically from September through November," the very stretch this season went missing. Forecasters had expected a quiet season since NOAA's May outlook, and the agency's Aug. 6 update gave a 75% chance of a below-normal season.

"When El Nino emerges, it usually becomes the dominant factor in total hurricane season activity, and this El Nino continues to get stronger every month."

Matt Rosencrans, lead hurricane season forecaster, NOAA's National Weather Service

The fuel points the other way. Climate Central's Climate Shift Index, cited by Yale, found human-caused warming made the Gulf's readings "several hundred times more likely over the western Gulf." Warm water sets the ceiling on a storm's strength; shear decides how close it gets. For 128 days, shear won.

Isaias carries the tug-of-war inside it. NHC's Discussion 7, issued at 4 a.m. CDT Thursday, described "around 20 kt of westerly vertical wind shear" over "30 C sea-surface temperatures," and an eyewall that "keeps coming and going." It is a hurricane being fed and harassed at once.

What the coast faces, as of Thursday morning

The figures here come from the hurricane center's 4 a.m. CDT advisory on Thursday, Oct. 8. Isaias was moving east-northeast at 9 mph, expected to turn northeast and then north. A Storm Surge Warning runs from the mouth of the Mississippi River to the Steinhatchee River, Florida, and the surge is the number to plan around. NHC's figures assume the peak arrives at high tide, and the deepest water will occur along the immediate coast near and to the east of the landfall location.

Seven feet of water is over nearly anyone's head, and the wind-based category says nothing about it, which is why a hurricane's category is a poor guide to its flood risk. NWS Mobile, in a statement at 10:17 p.m. CDT Wednesday, warned of places that "may be uninhabitable for an extended period."

Tropical storm conditions should begin Friday, with hurricane conditions in the warning area Friday night into early Saturday. Rain from Friday through the weekend could reach 3 to 7 inches, locally 10, from far southeastern Louisiana to the Florida Panhandle; earlier figures from NWS Mobile, and CNN's, said 3 to 6, so note which product a number comes from. Isolated tornadoes are possible Friday night in coastal Alabama, the Panhandle and far southwestern Georgia.

"Residents in these areas should prepare for the possibility of long-duration power outages."

National Hurricane Center, Discussion 7, 4 a.m. CDT Thursday

Florida was already wet. DeSantis's executive order, signed Oct. 6 for 25 counties, says a stalled front left "saturated soils" in parts of North Florida, even as Yale describes drought along the heaviest-rain coast; different places, both true. Alabama Gov. Kay Ivey declared an emergency for 40 counties, writing on X: While I hope for minimal impacts, we must take preparations seriously.

Okaloosa County ordered coastal areas evacuated from noon Thursday, CNN reported, and on Dauphin Island, Alabama, a voluntary evacuation covers about 350 to 400 homes. Gulf Shores canceled the National Shrimp Festival, which drew an estimated 325,000 people last year, AP reported. Pensacola Mayor D.C. Reeves had the tone right: "This is really about preparation."

A trough, not the calendar, sets the landfall

Discussion 7 forecasts 110 mph at 1 a.m. CDT Friday, "just shy of major hurricane intensity," which starts at 111 mph. By 1 p.m. CDT Friday the forecast eases to 105 mph, because in the last 12 to 24 hours shear "ramps up to 40-50 kt, and this will likely impart some weakening."

Weaker on paper is not smaller on the ground. NHC says the wind field "may become broader and more asymmetric," with "gusty winds" well inland, and its first discussion on Oct. 6 warned that users are urged not to focus on the forecast points. The track splits too: guidance shows "further west physics-based models, and further east AI/Machine Learning-based models," and NHC leans on the Google DeepMind ensemble mean and a corrected consensus, "our best performing track guidance this year."

California's cold-water shield

In the Pacific, El Niño works the other way, and AOML notes it "often increases hurricane activity in the eastern and central Pacific basins." As of NHC's 2 a.m. PDT advisory Thursday, Rachel had weakened to a 70 mph tropical storm about 895 miles west of the southern tip of Baja California. A trough, not El Niño directly, will turn it northeast, and NHC expects it to "approach the coast of extreme northern Baja California and Southern California at or near tropical storm strength over the weekend."

That is neither "remnants" nor a hurricane. NWS San Diego put the chance of 1 inch or more of rain Saturday night through Sunday night at 20 to 30 percent near the coast and 45 to 55 percent in the mountains. When NHC stretched the cone to Anaheim on Wednesday, the San Francisco Chronicle reported San Diego's odds of tropical-storm-force winds at "less than 10%" as of Wednesday, a reminder that the cone shows track uncertainty, not storm size.

The cold California Current usually saves the state; the Chronicle noted offshore water is "still too cold to support a true hurricane." The known exception came on Oct. 2, 1858, when about 75 mph winds hit San Diego, a settlement of 4,325 people, blowing the schooners Plutus, Lovely Flora and X.L. ashore. Coral evidence suggests an El Niño may have kept the water warmer than normal that year, according to the storm's history on HurricaneScience.org.

Hilary in 2023 is often remembered as California's tropical storm, but the hurricane center's post-storm report on Hilary found it "degenerated to a post-tropical low over northern Baja California," even though operationally it was shown moving into Southern California as a tropical storm. FOX Weather says this weekend could mark only the third time since 1963 that tropical systems have affected both coasts at once, a claim that hinges on what Rachel is when it arrives.

The open questions are concrete: where the center crosses, how much shear trims Isaias first, and whether Rachel lands tropical or post-tropical. NHC's next advisories come at 10 a.m. CDT and 8 a.m. PDT. The question of 1905 will wait longer, for a single six-hour line in a best-track file written months after the water in Mobile Bay has gone back out.