Tropical cyclones: Why we must observe the ocean to better protect people on land

Lessons learned from ocean observations during hurricanes Irene and Sandy pushed the U.S. to deploy a fleet of underwater robots during every hurricane season. As extreme weather events are becoming more frequent due to climate change, is it time to expand this hurricane forecasting capacity to other regions?

11 years after Hurricane Sandy hit the Caribbean islands and the East Coast of the United States in 2012, its destructive power is undoubtedly still vivid in the memories of its witnesses. The largest Atlantic hurricane on record, Sandy killed 233 people across the Caribbean and North America, and brought destruction with extreme winds, mudslides and flooding that inflicted almost US $70 billion in damage. 

“Just one year before that, we had Hurricane Irene, which was supposed to be a devastating storm – but then it kind of fizzled out. The next year, when alerts about Hurricane Sandy came up, people remembered Irene, and it was really difficult to convince anyone that this time it was going to be much bigger,” Dr Scott Glenn, distinguished professor at Rutgers University shares his memories. What he knew that the weather forecasters did not, was the alarming conditions below the ocean surface that warned the hurricane would be extremely powerful.

“When hurricanes Irene and Sandy hit, we had our underwater gliders – autonomous underwater vehicles that collect ocean observations, and they were deployed during both of these events. And right before Irene arrived, we saw the ocean cool very rapidly,” says Dr Glenn. “This cooling just pulled the energy out of the storm and rapidly weakened it. But there was no such cooling before Sandy, and so the heat would only fuel the storm.”

The ocean controls our planet’s water cycle, and even small changes within it can have a big impact on weather events on land. Such different ocean conditions observed before Hurricane Sandy raised serious concerns between scientists, including Dr Glenn himself, who quickly understood that this time the hurricane was not going to show any mercy. 

But surprising though it may seem today, 11 years ago weather forecasts were not automatically absorbing ocean data into their models. “I had this data from the gliders in the ocean, but at that time there was no way for me to communicate this. There was no way to add it to the information stream that reaches the forecasters,” he says.

Hurricane Sandy aftermath in Haiti (Credit: Logan Abassi / UN Photo)

Hurricane forecasts today – better than in 2012, but with room for improvement 

Since then, Dr Glenn and other oceanographers have worked hard to raise the importance of ocean observations in extreme event forecasting and to develop an operational system for data collection in the path of storms. 

Today the U.S. boasts a full hurricane glider fleet deployed during every hurricane season. These sturdy underwater robots can withstand destructive weather conditions in order to collect and transmit near real-time ocean data into the U.S. Integrated Ocean Observing System (IOOS), a part of the Global Ocean Observing System (GOOS). Since 2018, this data is included into hurricane forecast models, contributing to timely and more accurate warnings.

“By acting as an umbrella that facilitates the flow of data across global ocean observing networks, GOOS can provide prediction centers with more comprehensive and accurate global ocean data,” says Dr Weidong Yu, Co-Chair of the Ocean Observation Physics and Climate Panel. “This enables prediction centers to issue improved early warnings for severe storms, floods and droughts, protecting more lives and livelihoods worldwide.”

The powerful Cyclone Mocha that hit Myanmar and Bangladesh this May is a recent example of the critical importance of such ocean data. “The mobilization of humanitarian agencies against the threat of Cyclone Mocha was possible thanks to the real time monitoring of ocean and meteorological variables, which resulted in reliable forecasting and timely issue of an early warning,” says Dr Yu. 

Ocean gliders after successful recovery, 2020 U.S. Hurricane Season (Credit: NOAA AOML)

The Bay of Bengal faces the most deadly tropical cyclones on our planet, and experience from this region can help improve our ability to accurately and efficiently predict extreme weather events around the world. That is why it is one of the several pilot study regions within the Tropical Cyclone Project co-led by Dr Glenn through the GOOS Ocean Observing Co-Design programme under the UN Ocean Decade. 

Many countries around the world do not have the same ocean observing capacity as countries like the U.S., where Dr Glenn is based. “We have a really good idea of what needs to be done along the North Atlantic hurricane track, but now we want to expand that globally through GOOS. To do it, we bring different stakeholders from around the world together to participate in the co-design processes for improved tropical cyclone forecasting in different regions,” says Dr Glenn.

“For example, the Indian National Center for Ocean Information Services now collected its first ocean glider data from Cyclone Mocha. Together, we share experience and best practices so that emerging observing programs can spin up more efficiently,” he adds.

Extreme weather events are becoming more frequent

Many regions already face huge economic damage from tropical cyclones every year, and such events are becoming more frequent and intense as climate change progresses. Co-designing the ocean observations these regions need in order to improve their forecasting capability is an urgent necessity. 

“This year, the observed ocean surface temperature has already broken the global record. These changes have a significant impact on weather patterns and fuel extreme events,” says Dr Sabrina Speich, Co-Chair of the Ocean Observation Physics and Climate Panel. “The goal of the GOOS Ocean Observing Co-Design programme is to make rapid advances in our ability to predict these changes and adapt to them by strengthening collaboration among nations, operational services, observing operators and scientific experts.”

An underwater glider is deployed into the waters of the Bahamas in August of 2021 (Credit: Dr Nick Higgs, Cape Eleuthera Institute)

So far, the programme has been successful in gathering the necessary expertise, but there is a lot of work ahead. “Ocean observations are still very sparse and almost entirely funded through research projects and programs. Despite the progress made, the observing system remains fragile,” says Dr Speich. 

“A consistent flow of ocean data is critical to build effective hazard warning systems and for long-term adaptation to climate change and extreme events. But to ensure it, we need the involvement of more actors, including the private sector, as well as collaboration among governments, and sustained funding,” she adds.

In the Southern Hemisphere, East Africa recently had Cyclone Freddy – the longest and most intense tropical cyclone in history for this region. “They haven’t had this problem historically and are just starting to deal with it,” says Dr Glenn. “How do they start preparing for that? How do we get the ocean observing systems in place to improve those forecasts based on the needs of different regions?”

These are questions Dr Glenn and his team aim to explore through the Tropical Cyclone Project. Finding the right answers during this UN Decade of Ocean Science for Sustainable Development will bring a step change in our forecasting capabilities around the world, ultimately allowing us to save more lives and property on land.

Man looking out over flooded road and infrastructure damage in Mozambique (Credit: Denis Onyodi: IFRC/DRK/Climate Centre)

About GOOS:

The Global Ocean Observing System (GOOS) is the global home of ocean observing expertise. We lead and support a community of international, regional and national ocean observing programmes, governments, UN agencies, research organizations and individual scientists. Our Core Team of expert panels, networks, alliances and projects, supported by the GOOS Office, is in touch with ocean observing and forecasting around the world. We are a programme led by the Intergovernmental Oceanographic Commission (IOC) of UNESCO, with UN and science co-sponsors: World Meteorological Organization (WMO), UN Environmental Programme (UNEP) and the International Science Council (ISC).


The Intergovernmental Oceanographic Commission of UNESCO (IOC-UNESCO) promotes international cooperation in marine sciences to improve management of the ocean, coasts and marine resources. The IOC enables its 150 Member States to work together by coordinating programmes in capacity development, ocean observations and services, ocean science and tsunami warning. The work of the IOC contributes to the mission of UNESCO to promote the advancement of science and its applications to develop knowledge and capacity, key to economic and social progress, the basis of peace and sustainable development.

About the Ocean Decade:

Proclaimed in 2017 by the United Nations General Assembly, the UN Decade of Ocean Science for Sustainable Development (2021-2030) (‘the Ocean Decade’) seeks to stimulate ocean science and knowledge generation to reverse the decline of the state of the ocean system and catalyse new opportunities for sustainable development of this massive marine ecosystem. The vision of the Ocean Decade is ‘the science we need for the ocean we want’. The Ocean Decade provides a convening framework for scientists and stakeholders from diverse sectors to develop the scientific knowledge and the partnerships needed to accelerate and harness advances in ocean science to achieve a better understanding of the ocean system and deliver science-based solutions to achieve the 2030 Agenda. The UN General Assembly mandated UNESCO’s Intergovernmental Oceanographic Commission (IOC) to coordinate the preparations and implementation of the Decade.

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