2023 hurricane outlook stabilises: CSU stands by ‘above average’ call
Colorado State University finally got comfortable with its 2023 Atlantic hurricane season forecast after having swung from confidence to concern during the run-up to the active season.
CSU held its forecasts for the 2023 season stable from July and continues to call for an above average season, including 18 named storms, nine hurricanes and an accumulated cyclone energy (ACE) reading of 160, 30% above the long-term norm.
CSU sees a 48% chance that a hurricane could hit the US coastline, tipped somewhat towards a gulf coast landfall rather than the ATlantic seaboard. Of the nine expected hurricanes, four could attain category three or above.
The calculus remains a tug-of-war between conflicting factors. Storm-supportive warm sea surface temperatures continue to trump the arrival of a “robust” El Niño which otherwise would tend to create wind shear capable of tearing apart systems before formation.
“While a robust El Niño has developed and is likely to persist for the peak of the Atlantic hurricane season, most of the tropical and subtropical Atlantic has record warm sea surface temperatures,” CSU analysts wrote.
The “extreme” water temperature “is anticipated to counteract some of the typical El Niño-driven increase in vertical wind shear.”
CSU’s views have been anchored in the split between opposing factors since the first 2023 forecast came out early April. But the balance of risks has shifted. CSU had first counted on the powers of El Niño to deliver a weaker than average year, had evolved to a near-average outlook by early June and shifted to the current forecast array by early July.
That variance highlights the “considerable uncertainty” which CSU sees in the outlook.
“We stress that there is considerable uncertainty with this season’s outlook given the large spread in model guidance, as well as uncertainty with exactly how El Niño will interact with the extremely warm Atlantic,” researchers wrote.
The forecasts issued include the five storms recorded to date in 2023, leaving 13 tropical storms and eight hurricanes to go.
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