Hurricane Researcher Brian McNoldy on the Science Behind Sandy
https://www.youtube.com/embed/RhQktHY9aZgA video showing Sandy’s life from October 23 to October 31.
It was as a nine-year-old kid in Reading, Pennsylvania, that University of Miami scientist Brian McNoldy developed a fascination with hurricanes. “I think most of us have a storm,” he says. “Mine was Hurricane Gloria, in 1985.”
TV newscasters warned about the impending winds and rain. Local officials cancelled school for a few days. When the storm hit, it knocked out power. McNoldy went outside. “I can still remember how strong the winds were,” he says. “We didn’t get hit by the eyewall—just by the rainbands, but even that was pretty impressive.”
After earning undergraduate degrees in physics and astronomy at Lycoming College, a graduate degree in atmospheric science at Colorado State University, he landed at the University of Miami in January of 2012. “This is an up-and-coming school in hurricane research, and there’s a lot of momentum going here,” he says. “I'm happy to have the opportunity to be part of it.”
For his job, he works on something called “vortex initialization code” for a joint project with the Navy. It’s a series of sophisticated computer programs that allow scientists to take a crudely-represented hurricane out of a model analysis, replace it with a more realistic hurricane that has tuneable factors (such as intensity, size of the storm, etc.), and see how changes affect the forecast.
When he’s not working on the vortex code, he writes about hurricanes. “I started what, at the time, wasn’t called a blog, because they weren’t really there yet, in 1996,” he says. “For any storm—not even a storm, for any wave in the Atlantic, I would have my little list of people who were interested in what was going on, and I would send updates to them during hurricane season. I've been doing that for 16 years now.”
His audience has grown. From 2007 to 2010, he was invited to blog about hurricanes for The New York Times. In 2012, he started blogging for the Washington Post and the Rosenstiel School of Marine and Atmospheric Science. On October 22, when Sandy was still Tropical Depression 18, he was one of the first to report on the likelihood of it turning into the Northeast U.S. with possibly devastating consequences. We caught up with him to learn a bit more about the science behind Sandy.
When did you start watching Sandy?
I think some of the models were picking up on something forming in the Western Caribbean probably by about October 12 or 13. Some models picked up, run after run, something that would form in the Western Caribbean, and then would move north toward Cuba. That persisted and they ended up being right. The National Hurricane Center issued the first advisory on Tropical Depression 18 on October 22, then upgraded it to Tropical Storm Sandy later the same day. It eventually headed north over Jamaica and Cuba. I thought, Wow, that’s extremely impressive for those models.
On October 22, you blogged that there was a possibility it could hit the East Coast. How did you know that?
There are a few rather reliable global models. They’re models that run all the time, all year long, so they don’t focus on any one storm. They run for the entire globe, not just for North America. There are two types of runs these models can be configured to do. One is called a deterministic run and that’s where you get one forecast scenario. Then the other mode, and I think this is much more useful, especially at longer ranges where things become much more uncertain, is ensemble—where 20 or 40 or 50 runs can be done. They are not run at as high of a resolution as the deterministic run, otherwise it would take forever, but it’s still incredibly helpful to look at 20 runs.
Because you have variation? Do the ensemble runs include different winds, currents, and temperatures?
You can tweak all sorts of things to initialize the various ensemble members: the initial conditions, the inner-workings of the model itself, etc. The idea is to account for observational error, model error, and other sources of uncertainty. So you come up with 20-plus different ways to initialize the model and then let it run out in time. And then, given the very realistic spread of options, 15 of those ensemble members all recurve the storm back to the west when it reaches the East coast, and only five of them take it northeast. That certainly has some information content. And then, one run after the next, you can watch those. If all of the ensemble members start taking the same track, it doesn’t necessarily make them right, but it does mean it’s more likely to be right. You have much more confidence forecasting a track if the model guidance is in in good agreement. If it’s a 50/50 split, that’s a tough call.
On your Capital Weather Gang blog, you mentioned that Sandy was the second most powerful storm in terms of Integrated Kinetic Energy. Can you explain that and compare Sandy to past hurricanes in terms of her power?
Integrated Kinetic Energy (IKE) is a metric that quantifies the energy of a storm based on how far out tropical-storm force winds extend from the center (for a full description, see
Reinhold, 2007). If you take all of the winds that are tropical storm force or higher in Sandy, on average, when it was off the East Coast, they were around 500 miles out from the center. That is huge. For a smaller storm, which could be a lot stronger, you compute IKE and you’re likely going to end up with a smaller number. So, as far as this storm went, just because of how huge the wind field was, it ranked number two in all of the known IKE cases that we have of U.S. landfall. There are definitely some cases, like the 1938 Great New England Hurricane, that would be terrific to have, but we don’t have it because a very detailed wind structure must be known. But in terms of the more recent storms, Sandy was number two, behind only Hurricane Isabel in 2003.
Integrated Kinetic Energy (IKE) is the amount of energy contained in the surface wind, and that’s really good at creating a high storm surge. It’s that high energy in low levels of the hurricane that has a strong interaction with the ocean’s surface.
Hurricane Sandy's Integrated Kinetic Energy. Graphic: Brian McNoldy
A bigger storm with slower wind speeds would have a bigger storm surge than a smaller storm with higher wind speeds? Why?
The more time that strong winds blow over the ocean, the larger the swells can grow. Also, the more time you have onshore flow—wind blowing from the ocean onto the coast—the worse and more prolonged the coastal impacts can be. Instead of having 18 hours of coastal erosion and flooding, you might have three days of that.
How much has forecasting improved since Hurricane Katrina?
I don’t have a hard number available for that, but, offhand, I can say that there’s a trend that we are getting a lot more skilled in track forecasts. The tracks three days out and five days out are becoming more accurate. As far as intensity goes, there is not much of a trend there. In other words, the skill is not improving very quickly. In the case of Sandy, both the track and intensity forecasts were amazingly accurate. About as good as it could possibly be.
https://www.youtube.com/embed/uPQbh5PSr34A radar loop of Hurricane Sandy's landfall. Video: Brian McNoldy
And that was a result of what improving?
The National Hurricane Center has very skilled forecasters who utilize the model guidance to the best of their ability. But if the models are wrong, then forecasts made by looking at them are likely going to be wrong. In this case, most of the models eventually showed the northwest turn into the East Coast. If the model guidance erroneously showed it going northeast, NHC's error would have likely been very much on par with the models.
People are wondering how much Sandy is related to climate change. How do you answer that question?
I would say that you can’t really ever attribute a certain storm to climate change. It just doesn’t make sense. We’ve had extremely strong storms hit the East Coast for hundreds of years. This was not anything spectacular. It’s going to be remembered as something spectacular because it happened to create a storm surge that maximized in Manhattan. That’s luck—not good luck—but it’s luck. That’s exactly where the highest storm surge happened, and they happened to be low-lying enough that the storm surge could do all of that damage. If the storm had tracked 150 miles north of where it did, it wouldn’t have been as much of a mess. There still would have been severe coastal erosion and flooding, but no crippled NYC.
The same thing happened with Hurricane Katrina. That would have been a major natural disaster by itself, but then you have the man-made issue of the failed levees, which then flooded New Orleans. If that storm made landfall 25 miles further east, you would have had a very different outcome. You still would have had gigantic storm surges on the coast. But you would not have had the post-storm mess of what happened when the levees failed. The same with this storm: It’s not really a big deal to have a Category 1 hurricane hit the East Coast, but it managed to exploit weaknesses in some of the most vulnerable areas. As we like to say, “There's more to the story than the category.”
It’s more where it hit? And how it hit?
Exactly, it happened to come with a very large storm surge and hit probably the worst place that it could have, just by chance.
And the tide?
That’s important too. Sandy also happened to come at high tide, and not just any high tide, but it was a full moon, which made the tide extra high.
Do you think conditions associated with climate change exacerbated the effects of this storm?
No, I wouldn't attribute any component of Sandy to climate
change. The one thing that a warming planet and melting ice caps
does do is raise sea levels though. As time goes on, it will become
easier to flood coastal areas as sea level rises. As I mentioned,
there is a very long history of intense storms hitting the Northeast
U.S. This one wasn't really anything above the crowd. The precise
maximum storm surge timed with a full moon's high tide made it far
worse than it would have been at low tide.
Coastline of New Jersey after Sandy. Photo: NASA Goddard
And so what do you think the biggest lesson from Sandy has been so far?
It’s certainly that our coasts are very vulnerable. And that's not going to change any time soon, because people like to live near coasts. And that’s fine, but it comes with a lot of risk, because storms like this are going to keep happening. They always have. There are records of very big hurricanes hitting the Northeast from the 1500s and the 1600s. So, it’s not going to stop happening just because we have lots of people and really expensive stuff on the coast now.
One of the other things that resulted with this storm was constant communication. What was your takeaway on that?
Overall, I was pretty impressed with what I saw on Facebook and Twitter, which is increasingly becoming how people learn about news. From what I saw, most of the information that was being shared was good. There wasn’t a lot of misinformation going out.
The other thing that helped in this case, because it did end up being such a big deal, was the hype. A lot of storms get hyped—some end up warranting it, while others don't. When there is a nor’easter coming, there’s always big hype on TV. For Sandy, the message was clear: prepare for a major storm, and a significant storm surge, and strong winds. Nearly all of the warnings ended up being accurate, and so, in that case, the hype ended up being beneficial. It helped get the word out that this was not something to take lightly.
Also, be as prepared as you can before a major storm with fuel, food, and water. Being down in Miami now, there’s the routine at the beginning of hurricane season that you make sure you have lots of spare fuel, batteries, lots of spare food—non-perishables, and you just keep that throughout the season, hoping that you don't need to use it. People in south Florida are really good about not having that rush to go get everything right before a storm hits. It’s not the same in the northeast. People generally wait until two or three days before a storm and then there are panicked long lines at the store. After a hurricane, you can lose electricity for a week or two, and that’s just the way it is … you prepare as best you can to be self-sufficient. A message that we can all take away from this is to never underestimate nature's power.
This is the first in a series of interviews about Hurricane Sandy.
Part 2: Andrew Revkin on Lessons Learned From Sandy
Part 3: Dr. Ralph Ternier Talks From Haiti on Sandy and Cholera