With the storm-nurturing effects of a warm Atlantic likely to be only partially counterbalanced by a robust El Niño, an above-average Atlantic hurricane season is likely in 2023, the Colorado State University hurricane forecasting team says in its final seasonal forecast, issued August 3.
Led by Phil Klotzbach, with co-authors Michael Bell and Alexander DesRosiers, the Colorado team is calling for 18 named storms, 9 hurricanes, 4 major hurricanes, and an Accumulated Cyclone Energy (ACE) of 160 – the same numbers they gave in their previous forecast, issued July 6. These numbers account for the short-lived unnamed subtropical storm that occurred in mid-January, as well as the four other named storms that have occurred so far (Arlene, Bret, Cindy, and Don).
The long-term averages for the period 1991-2020 were 14.4 named storms, 7.2 hurricanes, 3.2 major hurricanes, and an Accumulated Cyclone Energy of 123. The Colorado outlook predicts the odds of a major hurricane hitting the U.S. this year to be 48%. It gives a 25% chance for a major hurricane to hit the East Coast or Florida Peninsula and a 31% chance for the Gulf Coast. The Caribbean is forecast to have a 53% chance of having at least one major hurricane pass through. All four of these likelihoods are slightly above their long-term averages. As Klotzbach put it, “It’s the clash of the titans: Record warm Atlantic sea surface temperatures and robust El Nino.”
The Colorado forecast uses a statistical model honed from 40+ years of past Atlantic hurricane statistics, plus dynamical model output from four groups: ECMWF (European model), UK Met Office (UKMET), Japan Meteorological Agency, and Centro Euro-Mediterraneo sui Cambiamenti Climatici.
UK Met Office still calling for a hyperactive Atlantic season
Among other seasonal outlooks being updated in early August, the UK Met Office continues to be among the most bullish. The latest UKMET outlook for the core June-through-November season in the Atlantic, issued on August 1, is calling for a 70% chance of 14-24 named storms, 6-12 hurricanes, 3-9 major hurricanes, and an ACE between 120 and 310. These ranges are near or just slightly below the UKMET outlook issued in May, but still leaning way above a typical season’s activity.
Khanun to swing back across Japan’s Ryukyu Islands
Typhoon Khanun was in the process on Thursday of making an about-face in the East China Sea, a near-180-degree right hook that will bring it back across the same island chain that it passed through earlier in the week. Khanun moved just south of Okinawa, the biggest of Japan’s Ryukyu Islands, while it was near peak strength as a large and fierce category 4-strength typhoon. The north side of Khanun’s inner core scraped the south end of Okinawa, and parts of the southern island experienced gale-force winds and even higher gusts accompanied by torrential rain for a full day or even longer. At least two deaths and 60 injuries have occurred, and about 25% of the homes across the Okinawa prefecture had lost power by early Thursday, reported EFE.
On its return visit to the Ryukyus, Khanun will be a much weaker entity. As of 8 a.m. EDT Thursday, the Joint Typhoon Warning Center pegged Khanun’s sustained 1-minute winds at 100 mph, making it the equivalent of a category 2 hurricane. Because Khanun is such a large system, some of its circulation is passing over waters upwelled over the last several days as the typhoon swings back eastward on Friday and Saturday. Showers and thunderstorms had waned dramatically on Thursday over Khanun’s northern half, and the typhoon’s inner eyewall had collapsed, leaving a huge outer eyewall more than 50 miles wide.
Khanun may hang on, though. Wind shear around the typhoon should diminish from 10-20 knots to less than 10 knots from Friday into the weekend, and an area of higher oceanic heat content near the Ryukyus may help keep the upwelling effects from greatly lowering the otherwise warm sea surface temperatures (around 29 degrees Celsius or 84°F). All told, Khanun should be able to remain a category 1 typhoon or at least strong tropical storm as it continues eastward, and it may reintensify somewhat as it passes over or near the Amami Islands, a subchain within the Ryukyus, by late this weekend. By the middle of next week, the main Japanese islands will likely contend with heavy rain from the typhoon (see Tweet below). Update (12:45 p.m. EDT Saturday): Now a tropical storm, but still with a sprawling circulation, Khanun has again passed east of Okinawa and will soon angle northward toward Kyushu in southwestern Japan. Enormous rainfall totals of 20-30 inches, perhaps even higher locally, can be expected on the eastern side of Kyushu’s mountainous landscape, including Miyazaki prefecture.
Dora is the Eastern Pacific’s second major hurricane of 2023; Atlantic is quiet
Compact but potent, Hurricane Dora vaulted to category 3 strength on Wednesday night some 700 miles southwest of Cabo San Lucas, Mexico, becoming the second major hurricane of the Eastern Pacific season, after category 3 Calvin in July. Dora briefly touched category 4 strength at 5 a.m. EDT Thursday, with top sustained winds of 130 mph; six hours later Dora was again a category 3, with top sustained winds of 125 mph. Dora was taking advantage of unusual warmth across the eastern tropical Pacific associated with El Niño: sea surface temperatures along Dora’s track on Wednesday were around 27-28 degrees Celsius (81-82°F), about 1 degree Celsius (1.8°F) above the average for this time of year.
Fortunately, Dora is well offshore and carving a innocuous path just south of due west across the remote Northeast Pacific. Dora will most likely pass several hundred miles south of Hawai’i early next week, perhaps still at or near hurricane strength. Update (12:45 p.m. EDT Saturday): Dora’s top sustained winds have continued to wax and wane, cresting to 140 mph late Thursday, dropping to 105 mph on Friday night, then re-surging to 115 mph on Saturday morning. It now appears more likely Dora will remain a hurricane as it passes well south of Hawai’i on Tuesday and continues westward. By late in the week, Dora could join the elite club (one every few years) of East Pacific hurricanes that cross the International Date Line and are reclassified as typhoons once they enter the Northeast Pacific.
Meanwhile, the Atlantic should remain calm through at least this weekend. No new tropical cyclones are expected to form over the next seven days, according to the 2 p.m. Thursday Tropical Weather Outlook from the National Hurricane Center (NHC). Update (12:45 p.m. EDT Saturday): The Atlantic outlook remains placid for at least the seven days up to August 12, according to NHC.
Introducing new Eye on the Storm YouTube series on extreme weather
Yale Climate Connections is debuting a new YouTube series about the wild world of extreme weather, featuring meteorologist Alexandra Steele. Join us for a virtual watch party on Friday, August 4 at 12 p.m. EDT at our YouTube channel to see the series premiere, “How bad could hurricanes get?” It features Yale Climate Connections meteorologist Dr. Jeff Masters and renowned climate communicator Susan Joy Hassol. See our post here about the series, which profiles Alexandra Steele.
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