Batten down the hatches: Hurricanes outlook revised to above average
Call it Climate Change 1, El Niño 0, at least in the hurricane forecasting game.
The US National Oceanic and Atmospheric Administration is the latest modeller to predict an above average hurricane season, adjusting its earlier forecast of a near normal season for the Atlantic.
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 storm-supportive record high warm sea temperatures.
The NOAA, which runs the former Climate Prediction Centre, said 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 NOAA is the latest in a long list of top research institutions to 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.
The NOAA noted that the Atlantic basin experienced an active start to the hurricane season with five storms that have reached at least tropical storm strength, including one hurricane already. An average hurricane season produces 14 named storms, of which seven become hurricanes, including three major hurricanes.
“The main climate factors expected to influence the 2023 Atlantic hurricane activity are the ongoing El Niño and the warm phase of the Atlantic Multi-Decadal Oscillation, including record-warm Atlantic sea surface temperatures,” said Matthew Rosencrans, lead hurricane season forecaster with NOAA’s Climate Prediction Centre. “Considering those factors, the updated outlook calls for more activity, so we urge everyone to prepare now for the continuing season.”
El Niño conditions are currently being observed and there is a greater than 95% chance that El Niño will continue through the Northern Hemisphere winter, according to the latest ENSO discussion from the Climate Prediction Centre.
