It's a consensus: the Atlantic is in high hurricane gear
The US National Oceanic and Atmospheric Administration (NOAA) has made it a consensus: the Atlantic is on track to an above-average hurricane season.
NOAA forecasters increased the likelihood of an above-normal Atlantic hurricane season to 60% from the 30% chance given in May. Chances for a season to fit into the long-term average, the prior baseline scenario, have fallen to 25%.
As at other forecasting institutions, the 2023 season is considered a tug-of-war between a rising storm-suppressive El Niño conditions and highly storm-supportive warm sea temperatures.
That balance is shifting. El Niño's storm-suppressive powers “have been slow to develop” and concern is building that “the associated impacts that tend to limit tropical cyclone activity may not be in place for much of the remaining hurricane season.”
Compared to NOAA's May outlook, the August update increases the ranges for all forecast metrics.
NOAA sees the named storm count in a range of 14 to 21, inclusive of the 5 seen to date, versus a May forecast tally of 12-17. Likewise, the hurricane count is now with a 70% chance of hitting a range from 6 to 11 (prior 5-9), of which 2-5 should hit major hurricane status (prior 1-4). Measured by accumulated cyclone energy (ACE), the season will likely hit a range of 105 to 200% of the long-term median.
The announcement brings a hint of herd behaviour: NOAA joins a long list of top research institutions that have upped their forecasts towards an above average season.
The UK's storm researcher Tropical Storm Risk (TSR) has twice upped its forecast from an initial view to below normal activity and now has a central forecast some 15% above the 30-year average.
Likewise, researchers at Colorado State University have seen their outlook evolve sequentially from mostly double-digit percentage gaps to the 30-year average to a central forecast for ACE some 30% above average.
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