Project Summary

Since 1990, tropical cyclones affecting the U.S. are the costliest and deadliest weather events to affect the U.S [ref].  In that time, NOAA has steadily improved the hurricane track forecasts, but improvements to its intensity forecasts have lagged by comparison.  Warm ocean waters fuel tropical cyclones and can have a major impact on their intensity.  Rapid intensification events are becoming more common, as warming oceans provide more energy to storms.  Consequently, coastal communities at risk need accurate forecast information to help preparations.

The Hurricane Glider effort is a coordinated partnership led by NOAA with the goal to support NOAA’s improvement of intensity forecasts.  Scientists across more than 20 partner institutions collect subsurface ocean observations of temperature and salinity and deliver the data to NOAA.  These observations enable NOAA to simulate a more realistic ocean in the models that feed hurricane intensity forecasts, and they are also used for ongoing scientific research and model development.  

Over the last decade, scientific research has shown that there are Essential Ocean Features (EOFs) that impact hurricane intensity, and they can influence a storm to undergo rapid intensification, or even rapid weakening.  These essential ocean features include:

• Freshwater barrier layers (e.g. in the Caribbean, which sees freshwater inflows from the Orinoco and Amazon rivers; and the Mississippi River delta area)
• The Loop current and its eddies
• Gulf stream and its eddies
• Subsurface cold pool (in Mid Atlantic Bight, off the NJ coast)
• Subsurface warm pools

Gliders are uniquely suited to explore these EOFs.  They can:

• Sample across/into currents
• Remain out at sea for 100+ days
• Dive to >1000 m
• Transmit data in near real-time for use in forecast models
• Carry multiple sensors
• Use ballasting for propulsion

Project Timeline

Over the last two decades, NOAA has made significant improvements to its hurricane track forecasts; however, intensity forecast improvements have lagged in comparison. Warm ocean waters provide the fuel for tropical cyclones, and particular ocean features (e.g. the Loop Current, Gulf Stream, eddies, freshwater barrier layers, bottom cold/warm pools etc) can play a significant role in intensifying or even weakening a storm. IOOS Regional Associations (MARACOOS, SECOORA, CARICOOS and GCOOS) in coordination with AOML, WHOI, and Navy partners have been deploying gliders to monitor and track these "essential ocean features" through glider field campaigns every hurricane season.

The coordinated hurricane glider partnership began in 2013, when Rutgers University (a MARACOOS partner) and NOAA’s AOML in coordination with CARICOOS, both leveraged Sandy Supplemental funds to explore subsurface ocean features that impact hurricane intensification. The success of these partners motivated a massive growth in participating partners across the Atlantic coastal domain to roughly 25 institutions. Studies over that time revealed that when models assimilate ocean observations to simulate a more realistic ocean, the hurricane intensity forecast error is reduced. In 2021, NOAA’s operational global ocean model that feeds the hurricane models began assimilating glider observations, marking a major milestone in this project.