Evaluating Tropical Cyclone Intensity Forecasts in the North Atlantic Using the NOAA Next-Generation Enterprise Ocean Heat Content Algorithm

Tropical cyclones (TCs) can rapidly intensify over the ocean, resulting in much more catastrophic impacts once they make landfall. This effect was seen in Hurricane Katrina, which went on to cause a record $161 billion in damage, and more recently in Hurricane Ida, which intensified rapidly over the Gulf of Mexico from a category 2 to a category 4 storm in just six hours before arriving on land later the same day. Improvements in TC intensity forecasting, particularly for rapid intensification and weakening (RI/RW) events, have historically lagged improvements in TC track forecasting, although recent advances in NOAA forecast capability have begun to address this lag. We present here a product which may be useful in further improving intensity forecasting. The heat content of the upper ocean, traditionally defined as the amount of energy stored in the ocean at sea temperatures of 26°C and above, can have a strong influence on both RI and RW events. However, it is becoming clear that it is important to consider additional physical characteristics of the upper ocean to determine the extent to which TCs are able to rapidly intensify.

The NOAA Next Generation Enterprise Ocean Heat Content (NGE OHC) algorithm, an empirical parameterization, generates depth-resolved ocean temperature and salinity profiles that will be used operationally to generate daily upper ocean heat content fields and support detailed analysis of coupled numerical hurricane models, particularly with regard to their potential for forecasting RI and RW. The method leverages the widespread dominance of low mode baroclinic variability in the ocean to directly estimate profiles from altimetry, sea surface temperature, and ancillary parameters. Real-time data used for estimating OHC include the NOAA/EUMETSAT Radar Altimeter Database System and the GOES-POES 5km Blended Sea Surface Temperature products, enabling us to produce the NGE OHC product daily at two resolutions: ~10 km along-track and ¼-degree gridded. In comparison with the current operational OHC product, the NGE OHC algorithm shows increased accuracy during extreme conditions, such as when extreme temperatures are present in the Gulf of Mexico (e.g., Hurricane Ida). We retrospectively compare the subsurface ocean conditions generated by the NGE OHC algorithm to output from the ocean-atmosphere coupled Hurricane Analysis and Forecast System (HAFS v1.0) and to in situ Argo float profiles for several case study TCs that underwent RI during the 2020–2022 Atlantic hurricane seasons. In particular, we will highlight TCs both within the Gulf of Mexico and within the broader North Atlantic Ocean where our improved OHC product may have enabled more skillful forecasts of the intensity of these storms.