hurricanes

Building Community to Solve the Big Challenges in Weather, Water, and Climate

Some thoughts following the AMS Summer Community Meeting

By Isabella Herrera, AMS Policy Program

How can the weather, water, and climate enterprise better collect and use socioeconomic data to keep vulnerable populations safe from environmental hazards? What are the challenges of establishing a national network to monitor the planetary boundary layer? How are we dealing with radio frequency interference that hampers weather monitoring and forecasting? These questions can be answered only through collaborative efforts across the weather, water, and climate enterprise. One of the most important roles of the American Meteorological Society is to convene meetings where WWC professionals can delve into these vital topics.

The AMS Summer Community Meeting is a perfect example of that convening ability in action. Professionals from the private, public, and academic sectors come together, both in person and virtually, to share their visions for the future of the weather, water, and climate enterprise(s). 

Having now worked for the American Meteorological Society for just over a year, I was very excited to have the opportunity to attend the AMS Summer Community Meeting for the first time in Minneapolis this August. At this two-day conference, attendees immersed themselves in discussions about current challenges, opportunities, and efforts throughout the AMS community and related fields.

A conduit for collaboration

As an in-person attendee this year, one thing that struck me was how the Summer Community Meeting served as a conduit for conversation. Information and ideas flowed easily between the various presenters, panelists, and the audience. For example, sessions focused on commercial radar services and NOAA research allowed the public and private sectors to share their perspectives. They presented pressing issues, opportunities for potential collaborations, and the work currently being done across the enterprise.

Summer Community Meeting attendees listen to a discussion of NOAA’s Next Generation Weather Radar (NEXRAD) system.

Some of the topics covered at this meeting included: updates on national policy; the NOAA Precipitation Prediction Grand Challenge; pressing issues in radar and forecasting, such as moving the national radar network beyond the WSR-88Ds; and the operations of the National Severe Storms Laboratory. My colleagues from AMS discussed the new and ongoing initiatives of the AMS Policy Program, such as: enhancing the effectiveness and potential of the weather enterprise over the next decade and beyond (see page 823 of the October issue of BAMS), the 2024 Summer Policy Colloquium, and the role of the AMS in enabling the future of both the climate and ocean enterprises.

Hurricane prediction gets personal

I was fascinated by some of the discussions about extreme weather and the increasing frequency of Billion-Dollar Weather and Climate Disasters. Attendees from the National Weather Service highlighted the widespread efforts to improve our forecasting and modeling of extreme weather events. 

Discussions about major tropical storms particularly resonated for me, especially with Hurricane Idalia making landfall in Florida during the Meeting. I was born, raised, and currently reside in the Sunshine State, so I’m well-attuned to hurricane season and planning for impending storms. Hurricane Idalia is a perfect example of how advancements in hurricane models and forecasting have allowed meteorologists and WWC professionals to more accurately predict and communicate extreme weather hazards (such as the rapid intensification of the storm right before it made landfall), thus saving lives. I was able to witness some of this behind-the-scenes work. 

Compared with being at home refreshing the National Hurricane Center’s webpage and listening to advisories on the local news, as I had during previous hurricane seasons, this was an invaluable experience.

Reunions

Photo: Larry Hopper and Isabella Herrera at the Summer Community Meeting
Isabella Herrera and Larry Hopper at the AMS 2023 Summer Community Meeting. Photo: Isabella Herrera.

I was delighted to see fellow AMS Summer Policy Colloquium alum Larry Hopper presenting on current and emerging radar technologies as part of a Panel Discussion on Weather Radar Research. Reconnecting with Colloquium alumni is something that I’m looking forward to at the AMS Annual Meeting in January, and although the dates have yet to be announced for next year’s Summer Community Meeting, I’m already excited to hear about the initiatives across the WWC enterprise for 2024.

I saw so many others reunite with their colleagues, too (from graduate school, from years of working in the field together, or from previous AMS meetings). It reminded me that, in addition to creating connections, collaborations, and conversation across the weather, water, and climate enterprise, the AMS has another integral part to play in this space: building community.

A Few Takeaways from the “State of the Climate in 2022”

Map of significant global weather and climate anomalies and events of 2022.

Record-high greenhouse gases, sea levels, monsoons, and droughts—and a volcanic vapor injection

By Michael Alexander, Lead, Atmosphere Ocean Processes and Predictability (AOPP) Division, NOAA, and BAMS Special Editor for Climate

The annual NOAA/AMS State of the Climate report has just been released, with a comprehensive global look at the climate in 2022. Produced by the NOAA National Centers for Environmental Information (NCEI) and the American Meteorological Society, the State of the Climate Report maps out the complex, interconnected climate phenomena affecting all parts of the globe. It also charts global progress in observing and understanding our climate system. 570 scientists from 60 countries contributed to this year’s report, including a rigorous peer review, making it a truly global endeavor. 

As the senior editor on this project, I wanted to share with you a few highlights. Click here to read the full report, published as a supplement to the Bulletin of the American Meteorological Society.

New record-highs for atmospheric greenhouse gases CO2, methane, and nitrous oxide.

It was yet another record-setting year for atmospheric carbon dioxide and other greenhouse gases. 2022 saw an average concentration of 417.1 ± 0.1 ppm for atmospheric CO2; methane and nitrous oxide also reached record highs. 

Graphs of yearly global surface temperature compared to the 1991-2020 average for each year from 1900 to 2022, from 6 data records, overlaid on a GOES-16 satellite image from September 22, 2022.  Image credit: NOAA Climate.gov.

Warmest La Niña year on record.

Despite being in the typically cooler La Niña phase of ENSO, 2022 was among the six warmest years on record, and was the warmest La Niña year ever recorded. Summer heat waves left annual temperatures at near-record highs in Europe, China, the Arctic, and Antarctica (parts of Europe set daily or seasonal heat records), and New Zealand experienced its warmest year ever. High-pressure “heat domes” helped elevate local temperatures in many areas, including parts of North America and Europe. 

Record-high global mean sea level and ocean heat.

Global mean sea level reached 101.2mm above 1993 levels, setting a new record for the 11th year in a row. 2022 also saw record-high global ocean heat content (as measured to 2000 meters below the surface), although La Niña moderated sea-surface temperatures.

Image credit: NOAA

Complex climate picture.

Global warming trends continued apace, but of course numerous large-scale climate patterns complicated the picture. In 2022 we saw the first “triple-dip” La Niña event (third consecutive La Niña year) of the 21st century. The Indian Ocean Dipole had one of its strongest negative events since 1982, which led to increased temperatures and precipitation in the eastern Indian Ocean. Along with La Niña, this contributed to record-breaking monsoon rains in Pakistan that caused massive flooding and one of the world’s costliest natural disasters. We also had a positive-phase winter and summer North Atlantic Oscillation affecting weather in parts of the Northern Hemisphere. 

A bad year for drought.

For the first time ever, in August 2022, 6.2% of the global land surface experienced extreme drought in the same month, and 29% of global land experienced at least moderate drought. Record-breaking droughts continued in equatorial East Africa and central Chile. Meanwhile, parts of Europe experienced one of their worst droughts in history, and China’s Yangtze River reached record-low levels.

Warmth and high precipitation at the poles.

2022 was the firth-warmest year recorded for the Arctic, and precipitation was at its third-highest level since 1950. The trend toward loss of multi-year sea ice continued. Meanwhile, Antarctic weather stations recorded their second-warmest year ever, including a heatwave event that collapsed the Conger Ice Shelf, and two new all-time record lows in sea-ice extent and area set in February. On the other hand, record snow/icefall due to atmospheric rivers led to the continent’s highest recorded snow/ice accumulation since 1993.

Image credit: NOAA

Notable storms: Ian and Fiona.

85 named tropical cyclones were observed across all ocean basins, an approximately average number. Although there were only three Category 5 storms, and the lowest recorded global accumulated cyclone energy, the year produced Hurricane Ian, the third-costliest disaster in U.S. history, as well as Hurricane Fiona, Atlantic Canada’s most destructive cyclone.

Massive volcanic injection of atmospheric water vapor.

The Hunga Tonga-Hunga Ha’apai submarine volcano in the South Pacific injected a water plume into the atmosphere of unprecedented magnitude (146+/-5 Terragrams, about 10% of the stratosphere’s total water) and height (reaching into the mesosphere). We don’t yet know what, if any, long-term effects this will have on the global climate, although the increase in water vapor has interfered with some earth system observations. 

The full report is a comprehensive and fascinating analysis of our climate system in the previous calendar year. I urge you to read it and communicate your own takeaways from the State of the Climate in 2022. You can read the press release here.

Infographic at top: World map showing locations of significant climate anomalies and events in 2022. Credit: NOAA.

Recent Trends in Tropical Cyclone Fatalities in the United States

Satellite photo of Hurricane Gonzalo (a ball of swirling clouds) over the Atlantic near Puerto Rico; other larger cloud systems are seen in the upper part of the photo, eclipsed by the curvature of the Earth in the top right. Photo taken by GOES East satellite at 1445Z on October 14, 2014. Photo credit: NOAA.

New data from the past ten years reveal increased prominence of freshwater floods and indirect fatalities in hurricane deaths

Guest post by Dr. Michael Brennan, Director, National Hurricane Center; Daniel Brown, Warning Coordination Meteorologist, National Hurricane Center; and Leah Pope, Hydrologist, Northwest River Forecast Center

The National Hurricane Center’s mission to “save lives and mitigate property loss” is not just achieved by issuing effective watches, warnings, and forecasts of tropical cyclones. We also spend a large portion of the “offseason” educating the public, emergency managers, and our media partners about the risks that tropical cyclones (TCs), including hurricanes, pose to life and property in the United States. Those include natural hazards such as storm surge, wind, and rip currents, and also includes dangerous conditions in the aftermath of a landfalling tropical cyclone, which may lead to “indirect” fatalities. These are deaths which are not directly due to the forces of the storm, but which would not otherwise have occurred. NHC routinely compiles and assesses TC-related information through vehicles such as our Tropical Cyclone Reports (TCRs). Data from the most recent decade reveal that fatality trends may be changing.  

Note:  The fatality data presented here do not include any fatalities from Hurricane Maria in Puerto Rico, since there was no specific, definitive cause provided for those deaths.

Direct Fatalities

Aerial photo of a peninsula/barrier island that has been breached by a storm surge. Sand, buildings, and other structures have been washed away or damaged, including visible broken lines of sandbags, a damaged bridge, damaged trees, and obliterated buildings; only one house appears to still be standing.
Storm surge damage from Hurricane Ike, Bolivar Peninsula, Texas, 2008. Photo credit: NOAA.

Previous studies by Rappaport (2014) and Rappaport and Blanchard (2016) summarized direct and indirect fatality data from Atlantic basin tropical cyclones in the United States for the 50-year period 1963–2012. During that period, nearly 9 out of 10 tropical cyclone-related direct deaths in the United States were due to water. Storm surge was responsible for nearly half (49%) of the direct deaths, and over one-quarter (27%) were due to rainfall-induced freshwater flooding.  

In response, the National Weather Service (NWS) and NHC worked to improve outreach, education, and communication of storm surge and rainfall hazards. We introduced new real-time storm surge maps in 2014, and in 2017 introduced a storm surge watch/warning that highlights the risk of life-threatening storm surge inundation. 

New Data Suggest Changing Trends

Since 2012, the United States has experienced 21 hurricane landfalls, including 8 major hurricanes, and more than 20 tropical storm landfalls. Eighteen of these hurricane landfalls, including all of the major hurricanes, occurred during 2017–22 after a relatively quiet period. Given the significant number of tropical cyclone landfalls in recent years, and increased deployment of warnings around the storm surge hazard, NHC examined and compared fatality data from the most recent 10-year period (2013–22) to the earlier studies.

Hazard % of direct fatalities from this cause
(1963–2012)		% of direct fatalities from this cause
(2013–2022)
Storm Surge49%11%
Freshwater Flooding27%57%
Wind8%12%
Surf/Rip Currents6%15%
Offshore Marine Incidents6%3%
Tornadoes3%2%
Other1%1%
Note: Due to rounding, numbers may not add up to 100%.

During the most recent 10-year period in the United States, about 57% of direct tropical cyclone deaths were due to drowning from freshwater (rainfall) flooding. Surf and rip current fatalities have become an increasing threat, making up about 15% of direct fatalities in the past decade. These fatalities often occur one or two at a time from distant storms hundreds of miles offshore. Florida, North Carolina, and New Jersey experienced the highest number of TC-related surf and rip current fatalities. Storm surge and wind-related deaths account for 11% and 12% of the direct fatalities, respectively.  

Every hurricane is different, however. Hurricane Harvey in 2017 had the largest number of direct deaths—68, 65 of which were due to freshwater flooding in Texas—in the past decade. Hurricane Ian (2022) was the second deadliest with 66 direct fatalities, 41 of which were due to storm surge in Florida. More than 65% of those who died from direct causes were men, with about 60% of the victims over the age of 60.

Indirect Causes

Image of a boat stranded on land, leaning against a wind-destroyed structure and a power line, amid other debris, including destroyed buildings and cars. Three people stand next to the boat observing the damage.
Aftermath of Hurricane Ike in Galveston, Texas, 2008. Photo credit: NOAA.

The recent study revealed that over the past 10 years there has been nearly an equal number of indirect deaths as direct fatalities. Indirect fatalities are due to a wide range of causes, including traffic accidents (16%), preparation/cleanup accidents (15%), carbon monoxide poisoning (12%), lack of medical care (11%), power problem/electrocution (11%), post-storm heat deaths (9%), unknown causes (9%), cardiac-related deaths (7%), and evacuation-related deaths (5%). 

The largest number of indirect deaths in the past decade occurred in association with Hurricanes Ian (90), Irma (82), Michael (43), Harvey (35), and Laura (34). Most (75%) of the indirect deaths are associated with major hurricane landfalls, which leave communities very vulnerable and often with long-duration, widespread power outages. More than half (57%) of the victims were over the age of 60. Younger victims tended to die in vehicle accidents; for older victims, medical-related issues, heat, evacuation, and other accidents were more likely causes of death.

Improving Warnings and Public Understanding

The results of these most recent studies have led the NWS and NHC to increase messaging on the hazards and causes of both direct and indirect fatalities. We continue to highlight rainfall flooding and storm surge risk through the Weather Prediction Center’s Excessive Rainfall Outlook, Flood Warnings from local NWS offices, and increased emphasis on the Storm Surge Warning. These warnings are the loudest “bells” that the NWS can ring during life-threatening flooding. We encourage our media and emergency management partners to work with us to encourage timely public response and personal preparedness ahead of these threats. 

Additionally, with the increased percentage of rip current fatalities associated with high surf and swells from distant hurricanes, the NWS has created new infographics to explain this deadly beach hazard, and is working on graphics to better highlight the threat in real time.

During the highly impactful 2020 hurricane season in the United States, there were more fatalities associated with carbon monoxide poisoning from the improper use of generators than there were from storm surge. After that season, NHC and the NWS developed infographics and worked with media and emergency management partners to highlight that threat. While it is difficult to determine the effectiveness of that messaging, it is encouraging to know that there were no carbon monoxide related-fatalities in the aftermath of Hurricane Ian in 2022 in Florida, despite its devastating impacts and widespread power outages in that state.   

NHC relies on relationships with media, emergency management partners, and the entire weather enterprise to help reach the public before, during, and after tropical cyclone threats. These efforts undoubtedly increase awareness, encourage preparation, and save lives. We hope to continue to improve our messaging and understanding of the threats and causes of injuries and fatalities to better meet our collective mission.  

Visit the National Hurricane Center online.

Header photo: Hurricane Gonzalo in the Atlantic. Photo taken by GOES East satellite at 1445Z on October 14, 2014. Photo credit: NOAA.

This post was invited based on a presentation given by Dr. Brennan at the 50th Conference on Broadcast Meteorology, which took place in Phoenix, Arizona, June 21–23, 2023. The conference was organized by the American Meteorological Society Board on Broadcast Meteorology and chaired by Danielle Breezy and Vanessa Alonso.

An Anticipated Increase in Earth's Strongest Storms

GoniA little more than two weeks ago, Supertyphoon Goni blasted ashore in the Philippines with top sustained winds of 195 mph, becoming the strongest landfalling tropical cyclone on record. It topped STY Haiyan’s 190 mph land strike just seven years ago. With Hurricane Iota in the Caribbean explosively intensifying 100 mph in under 24 hours to reach Category 5 intensity Monday, it set a new record of five consecutive years of Cat 5 hurricanes in the North Atlantic tropical cyclone basin. Among the seven catastrophic hurricanes, starting with Matthew in 2016, were Dorian and Irma, packing 185 mph and 180 mph steady winds, respectively, with peak gusts well over 200 mph.
Goni is the latest formidable example of an increasing trend in tropical cyclone intensity. While Goni established a new landfall wind intensity record, Iota and other recent major hurricanes Eta, Zeta, and Delta set or challenged records for most intense hurricanes so late in the season.
PercentilesJames Elsner of Florida State University says this is to be expected. His research stated in 2008 that there was an upward trend in the intensity of the most intense tropical cyclones. Rising ocean temperatures, as theory predicted, were driving the trend. And with oceans continuing to warm along with Earth’s climate since then, Elsner anticipated the continuing upward trend. New research published in the Bulletin of the American Meteorological Society confirms his prediction, finding that another 3.5 to 4.5 percent increase in intensity has occurred with the strongest tropical cyclones during the period 2007-19.
Globally, all basins show upward trends, Elsner says, with the North Atlantic and Western North Pacific revealing the steepest and most consistent upticks.

An Anticipated Increase in Earth’s Strongest Storms

GoniA little more than two weeks ago, Supertyphoon Goni blasted ashore in the Philippines with top sustained winds of 195 mph, becoming the strongest landfalling tropical cyclone on record. It topped STY Haiyan’s 190 mph land strike just seven years ago. With Hurricane Iota in the Caribbean explosively intensifying 100 mph in under 24 hours to reach Category 5 intensity Monday, it set a new record of five consecutive years of Cat 5 hurricanes in the North Atlantic tropical cyclone basin. Among the seven catastrophic hurricanes, starting with Matthew in 2016, were Dorian and Irma, packing 185 mph and 180 mph steady winds, respectively, with peak gusts well over 200 mph.

Goni is the latest formidable example of an increasing trend in tropical cyclone intensity. While Goni established a new landfall wind intensity record, Iota and other recent major hurricanes Eta, Zeta, and Delta set or challenged records for most intense hurricanes so late in the season.

PercentilesJames Elsner of Florida State University says this is to be expected. His research stated in 2008 that there was an upward trend in the intensity of the most intense tropical cyclones. Rising ocean temperatures, as theory predicted, were driving the trend. And with oceans continuing to warm along with Earth’s climate since then, Elsner anticipated the continuing upward trend. New research published in the Bulletin of the American Meteorological Society confirms his prediction, finding that another 3.5 to 4.5 percent increase in intensity has occurred with the strongest tropical cyclones during the period 2007-19.

Globally, all basins show upward trends, Elsner says, with the North Atlantic and Western North Pacific revealing the steepest and most consistent upticks.

We May Be Able to Further Improve Hurricane Track Forecasts After All

ZetaZeta blossomed into the 11th hurricane of this hyperactive season Monday and its forecast track takes it ashore on the Gulf Coast by midweek. The National Hurricane Center (NHC) on Monday said computer models had become more tightly clustered with the forecast in the Gulf, “resulting in an increase in track-forecast confidence,” and Hurricane Zeta is expected to become the United States’ record 11th storm landfall in a single season.

Such confidence is a reflection that NHC’s tropical storm and hurricane track forecasts, which go out 5 days, have substantially improved in the last 25 years. But, a 2018 essay in the Bulletin of the American Meteorological Society (BAMS) found that such improvements in track forecasts have slowed, raising concern about making them any better and extending them out beyond 5 days with any skill. While that study suggested improvements may have reached a limit, new research also published in BAMS finds a way to further refine them in the coming decades. Using a different interpretation of track position errors than the earlier article, the research moves the predictability limit for tropical cyclones out a day per decade to 6-8 days in the next 10-30 years.

Late Season Hurricanes Bring Research Opportunities, Too

After a veritable flurry of storms in the Atlantic since August, the basin has gone quiet following the landfalls of Tropical Storm Beta in Texas, and Post-Tropical Storm Teddy in Nova Scotia. But late-season storms are quite common in the Atlantic, and as this hyperactive hurricane season combines with confirmed La Niña conditions, this year it seems almost like an expectation. And that means people on the coast need to stay alert to what’s going on in the atmosphere, but it also means there’s still promise for additional hurricane research this year.

Recent Octobers have seen a couple of very intense and even catastrophic hurricanes develop and make landfall. The last big one was Hurricane Michael, which slammed the Florida Panhandle in 2018. In 2016, Hurricane Matthew roared to life in the Caribbean, reaching Category 5 intensity on the Saffir-Simpson scale before crashing into Hispaniola as a Cat. 4, and then menacing the Florida coast for days and eventually swirling into the Carolinas.

Matthew turned out to be a late-season success for NOAA’s Sensing Hazards with Operational Unmanned Technology (SHOUT) project.  SHOUT evaluated the ability of observations taken by the high-altitude, unmanned Global Hawk aircraft to improve forecasts of high-impact weather events, which are “one of the most critically needed capabilities of weather services around the world,” write lead author Gary Wick and his colleagues in their article on SHOUT in the Bulletin of the American Meteorological Society.

NASA’s Global Hawk flew 15 missions sampling Hurricane Matthew and 5 other tropical cyclones as well as 3 winter storms in 2015 and 2016. Instrumented with GPS dropwindsondes and remote sensors, Global Hawk’s data were examined in real time by forecasters, assimilated in operational weather prediction models, and applied to data impact studies, demonstrating positive results.

BAMS asked Wick a few questions about his work and SHOUT in particular (for the full answers, see the print or digital edition of the magazine):

BAMS: What would you like readers to learn from your article?

Gary Wick: The primary message we would like to convey is that Global Hawk can provide highly useful observations of high-impact weather events that would be very difficult to obtain with any other
existing aircraft or observing system.  It was possible to consistently see the potential for forecast benefit across a wide range of models.

Gary_Wick-and-Global_HawkBAMS: How did you get into this focus on improving operational hurricane forecasts with unmanned aircraft?

GW: I was fortunate to have participated in both the NASA-led Genesis and Rapid Intensification (GRIP) and Hurricane and Severe Storm Sentinel (HS3) campaigns and was able to observe the potential application of the Global Hawk to tropical cyclone research.  The distinct goals of those campaigns, however, didn’t allow for a real focus on the operational hurricane forecasting problem.  We in the NOAA UAS Program were extremely excited when support from the Disaster Relief Act of 2013 gave us the opportunity to conduct a dedicated campaign to examine the impact of observations from the Global Hawk on forecasts of high-impact weather.

BAMS: What got you initially interested in meteorology?

GW: My path to this project was really quite indirect.  My interests growing up really centered around planes, due in part to living close to the old Denver airport.  As a kid, I would frequently ride my bicycle out to the end of the runway and watch planes take off and land.  These interests led me to study Aerospace Engineering as an undergraduate where I just happened to take a class one year in environmental aerodynamics taught by a scientist from a predecessor of my current NOAA laboratory.  This class introduced me to remote sensing and I ended up pursuing graduate studies centered primarily around satellite-based remote sensing.  The work with UAS in general and this project in particular allowed me to come full circle, in a sense, combining my many interests in aircraft, remote sensing, and weather.

BAMS: What surprised you the most in the SHOUT project?

GW: As someone whose personal work hadn’t centered around atmospheric models, assimilation, and weather forecasting, it was surprising to me early on how providing weather models with more, high quality, direct observations wouldn’t necessarily improve the resulting forecasts and, in some cases, could actually degrade them.  One might naively think that better data could only lead to a better final product.  After gaining an appreciation of how challenging it is to achieve meaningful forecast improvements through addition of any data to our current observing and assimilation systems, I was
very pleasantly surprised that it does appear that the highly unique observations enabled by the Global Hawk still have the potential to help us improve our forecasts of high-impact weather events.

BAMS: What was the biggest challenge you encountered in the experiment?

GW: As with seemingly any field project, our biggest challenge was probably obtaining the weather events we were hoping to study during the necessarily limited duration of the campaign.  Through the multiple years of the GRIP, HS3, and SHOUT campaigns, the Global Hawk developed almost a reputation as a “hurricane repellent” due to the limited number of storms during the experimental periods.  Perhaps the most interesting storm sampled during the SHOUT campaign, Hurricane Matthew in 2016, actually occurred after the scheduled end of the experiment.  Fortunately, we were able to extend the campaign and collect some very valuable additional observations.

Matthew_GHBAMS: What’s next? How will you follow up?

GW: Several additional studies are underway to better evaluate the impact of all the different observations collected in different and the most recent models. NOAA is still working to evaluate and increase the number of UAS observations (particularly from smaller platforms) to help conduct our mission.

Hurricane Sally's Extreme Flood Potential

Hurricane Sally is inching ashore in southeast Alabama Wednesday morning and has started to flood parts of the central Gulf Coast with an expected 1-2 feet of rain, maybe more. With that much rain forecast, it seems likely to join other recent catastrophic flood disasters Harvey (2017) and Florence (2018) in ushering in a new era of rainier storms at landfall that bring with them an extreme rain and flooding threat.
Sally_rainfall-3
Recent research by NOAA’s Tom Knutson and a team of tropical weather and climate experts in the March Bulletin of the American Meteorological Society and blogged about here determined with medium-to-high confidence that more and more hurricanes in our future warming world will be wetter at landfall.
And with more wetter storms on the way, better communication about these potentially deadly impacts from copious rainfall is needed. Another BAMS article we blogged about addressed this by creating an Intuitive Metric for Deadly Tropical Cyclone Rains. Its authors designed the new tool—the extreme rainfall multiplier (ERM)—to easily understand the magnitude of life-threatening extreme rain events.
Co-author James Kossin explained to BAMS:

Water presents a much greater hazard in a hurricane than wind does, but the Saffir-Simpson categories are based on wind-speed alone. Salt-water hazards along and near the coast are caused by storm surge. Coastal residents are warned about these hazards and are provided with evacuation plans. Fresh-water flooding from extreme hurricane rainfall, however, can happen inland away from evacuation zones, and pose the greatest threat to life and property in these areas where people tend to shelter-in-place. Compound hazards such as dam failures and land-slides in mountainous regions pose additional significant threats. In this case, effective warnings and communication of the threats to inland populations is paramount to reduce mortality. This work strives to present a tool for providing warnings based on people’s past experience, which gives them a familiar reference point from which to assess their risk and make informed decisions.

Lead author Christopher Bosma:

We started out this project focused on analyzing the catastrophic and record-breaking rainfall associated with Hurricane Harvey. But, as we started to finish our analysis of that system, just a year later, Hurricane Florence brought devastating and torrential rainfall to the Carolinas, which forced us to go back and revisit some of our initial analysis. The fact that multiple major storms happened in quick succession grabbed a lot of headlines, but, from a research and scientific perspective, it also provided a chance to note how the messaging used to describe these systems had changed (or not) and think of other ways to use the metric we had developed.

ERM is not yet operational, but that is the researchers’ goal, to “convey effective warnings to people about fresh-water flooding threats,” Kossin says.
Hurricane Sally is one such extreme rainfall flood threat, with “significant to historic flooding” likely, the National Weather Service says.

Hurricane Sally’s Extreme Flood Potential

Hurricane Sally is inching ashore in southeast Alabama Wednesday morning and has started to flood parts of the central Gulf Coast with an expected 1-2 feet of rain, maybe more. With that much rain forecast, it seems likely to join other recent catastrophic flood disasters Harvey (2017) and Florence (2018) in ushering in a new era of rainier storms at landfall that bring with them an extreme rain and flooding threat.

Sally_rainfall-3

Recent research by NOAA’s Tom Knutson and a team of tropical weather and climate experts in the March Bulletin of the American Meteorological Society and blogged about here determined with medium-to-high confidence that more and more hurricanes in our future warming world will be wetter at landfall.

And with more wetter storms on the way, better communication about these potentially deadly impacts from copious rainfall is needed. Another BAMS article we blogged about addressed this by creating an Intuitive Metric for Deadly Tropical Cyclone Rains. Its authors designed the new tool—the extreme rainfall multiplier (ERM)—to easily understand the magnitude of life-threatening extreme rain events.

Co-author James Kossin explained to BAMS:

Water presents a much greater hazard in a hurricane than wind does, but the Saffir-Simpson categories are based on wind-speed alone. Salt-water hazards along and near the coast are caused by storm surge. Coastal residents are warned about these hazards and are provided with evacuation plans. Fresh-water flooding from extreme hurricane rainfall, however, can happen inland away from evacuation zones, and pose the greatest threat to life and property in these areas where people tend to shelter-in-place. Compound hazards such as dam failures and land-slides in mountainous regions pose additional significant threats. In this case, effective warnings and communication of the threats to inland populations is paramount to reduce mortality. This work strives to present a tool for providing warnings based on people’s past experience, which gives them a familiar reference point from which to assess their risk and make informed decisions.

Lead author Christopher Bosma:

We started out this project focused on analyzing the catastrophic and record-breaking rainfall associated with Hurricane Harvey. But, as we started to finish our analysis of that system, just a year later, Hurricane Florence brought devastating and torrential rainfall to the Carolinas, which forced us to go back and revisit some of our initial analysis. The fact that multiple major storms happened in quick succession grabbed a lot of headlines, but, from a research and scientific perspective, it also provided a chance to note how the messaging used to describe these systems had changed (or not) and think of other ways to use the metric we had developed.

ERM is not yet operational, but that is the researchers’ goal, to “convey effective warnings to people about fresh-water flooding threats,” Kossin says.

Hurricane Sally is one such extreme rainfall flood threat, with “significant to historic flooding” likely, the National Weather Service says.

The Forecast for Huge Numbers of Hurricanes in 2020: Not a "New Normal"

Thursday NOAA updated its forecast to an “extremely active” Atlantic hurricane season. That has some news outlets linking the  19-25 predicted named storms to Earth’s future—even warmer—global climate. The future looks like it will indeed bring high levels of overall “activity” due to the intense, damaging hurricanes of a warming world (regardless of whether the frequency of storms overall changes). And, of course, settling into a new “norm” isn’t going to happen while warming is ongoing. But the huge number of storms forming? That’s a lot of what the public takes away from the forecast, and that profusion of named storms is not projected to be characteristic of seasons to come.
As we blogged here in May, recent research published in the Bulletin of the American Meteorological Society finds there’s no evidence to support an increasing trend in tropical cyclone frequency.
NOAA-2020-outlook-update2In that assessment of the current literature, Tom Knutson (NOAA) and other top tropical experts reviewed a number of peer-reviewed studies and determined that a majority found the numbers of named storms actually decrease in climate projections as we move deeper into this century. But there was no consensus among the authors to either support or refute those studies since their research also showed that “there is no clear observational evidence for a detectable human influence on historical global TC frequency.”
Their assessment did find that we can expect stronger and wetter hurricanes in our warming world and, notably, a possible uptick in the number of intense (Category 4 and 5) hurricanes. It’s these storms that have Knutson and his colleagues most concerned since a majority of hurricane damage is done by the big ones. Their increase is alarming even if the number of storms goes down.
Notable with this week’s forecast update is a prediction close to record territory. “We’ve never forecast up to 25 named storms” before—more than twice a season’s typical 12—noted Jerry Bell, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center. He went on to say there will be “more, stronger, and longer-lived storms than average” in the Atlantic Basin, which includes the Caribbean Sea and Gulf 0f Mexico. In an average season there are six hurricanes,  and three of those grow into major hurricanes.