The 2023 Atlantic hurricane season begins today and forecasters at Colorado State University (CSU) – the group that pioneered seasonal hurricane forecasts in the 1980s – released new numbers, raising their seasonal predictions from earlier forecasts.
The forecast team at CSU now predicts 15 named storms, seven hurricanes, and three Category 3 or stronger hurricanes across the Atlantic in 2023, activity that suggests an average to even slightly above average season ahead.
In mid-April, CSU forecasters called for 13 named storms, six hurricanes, and two Category 3 or stronger storms, a slightly below average year and their lowest seasonal hurricane forecast since 2019.
Forecasters look to ocean temperatures – both in the Atlantic and Pacific – as a harbinger for what may be in store for the Atlantic hurricane season.
Across the eastern equatorial Pacific, waters continue to quickly warm, this week reaching their warmest levels relative to average since the week of November 21, 2019, a remarkable 184-week high in the departure from average. Once waters top 0.5 degrees Celsius or higher across the bellwether eastern equatorial Pacific for several consecutive months, an El Niño is declared.
Government forecasters expect this will happen sometime in the next month or two.
On the Atlantic side, El Niño conditions in the Pacific typically portend a reduction in overall hurricane activity, all else being equal. The warmth in the eastern equatorial Pacific promotes storminess over the Pacific, with upper-level exhaust from the increased storminess blowing through the Caribbean and western Atlantic, where it amps up storm-busting wind shear, thwarting would-be Atlantic systems. Circulation patterns may also shift, with more sinking air over the Atlantic putting a lid on developing storms.
But in 2023, all else isn’t equal. The Atlantic is on a literal hot streak. The main development region of the Atlantic is nearly as warm as it’s been in the modern satellite era (since 1981) for this time of year, rivaling the warmth seen in the weeks leading up to the extremely active 2005 and 2010 hurricane seasons.
Additionally, as CSU forecasters noted in their forecast discussion today, warmth in the region of the tropical north Atlantic – historically the best leading indicator for seasonal Atlantic tropical activity – is at record highs. And in the near term, there appears to be no let-up in the warming trend across the Atlantic. A weaker subtropical ridge of high-pressure into mid-June should reduce normally brisk trade winds that would otherwise help to cool these waters.
If a moderate or even strong El Niño does develop by the traditional August-September-October peak of hurricane season, will the extra-warm Atlantic work to counteract El Niño’s usual soothing effect on Atlantic hurricanes?
With their latest forecast, CSU forecasters seem to suggest so. In fact, although the European forecast model shows a blockbuster El Niño taking shape by September, the same modeling system predicts only modest wind shear in the Atlantic, yet another indication that El Niño may not give us its usual reprieve in 2023.
Regardless of seasonal forecast numbers and overall activity, it only takes one bad hurricane to make for a bad hurricane season in South Florida.
Seasonal forecast numbers can’t tell us where storms will track and whether they’ll hit land. In 2010, a remarkable 12 hurricanes formed but none struck the U.S.
On the other hand, only 7 hurricanes formed in 1985, but six made U.S. landfall, tying for the most hurricane landfalls in a single hurricane season.
As always, prepare this season as you would any other year and have a plan before a storm threatens.
We continue to monitor a small but tenacious area of low pressure over the eastern Gulf of Mexico today, designated Invest 91L by the National Hurricane Center.
Despite 30 to 40 knots of heavy wind shear – a typically prohibitive development factor – the system drifted northward toward a lighter pocket of upper winds overnight and is firing off persistent thunderstorms closer to its center.
The National Hurricane Center increased formation chances from 20% to 50% early on Thursday, but the development window is narrow and will be quickly closing by the weekend.
Regardless of development, South Florida will see a spigot of deep tropical moisture on the east side of 91L and the potential for heavy rainfall today through Saturday.
Hurricane Hunters are scheduled to investigate the system this afternoon. If a tropical storm forms, its name would be Arlene, the second system of 2023 (a subtropical system formed back in January off the northeast U.S.) but the first named storm of the season.