Research Spawns Stunning Hurricane Sandy Animations

By Andrew Freedman

Hurricane Sandy was one of the most destructive storms on record on the East Coast, tearing apart coastal communities from Maryland to Connecticut through a deadly combination of high winds and a record high storm tide. The storm was the result of a rare combination of events, as a purely tropical hurricane transitioned into a large hybrid storm, which had both tropical and extratropical characteristics.

In Sandy's wake, researchers have tried to gain a better understanding of the characteristics of this fascinating storm, and their work has already resulted in some interesting insights. 

Mel Shapiro, an atmospheric scientist who studies how tropical storms and hurricanes transition into powerful extratropical storm systems, recently produced a series of astonishing animated visualizations showing the inner workings of Sandy as the storm moved up the Eastern Seaboard and eventually made landfall on the evening of Oct. 29. 

These visualizations were produced with an ultra-high resolution computer model run at the National Center for Atmospheric Research in Boulder, Colo. Known as the ARW-WRF model, it used data from an operational computer model that the National Weather Service used to forecast the storm. 

The animation above shows the modeled horizontal wind speed, together with wind vectors at 1,000 meters in elevation. Brighter colors represent stronger winds, with red signifying winds greater than 45 meters per second, which is close to 100 mph. Credit: Science by Mel Shapiro and Thomas Galarneau. Visualization by Alan Norton, NCAR Computational and Information Systems Laboratory, using VAPOR visualization software.

The visualizations help show how Sandy was captured by upper-level winds, and pushed into the New Jersey coast, which was a track unprecedented in the historical record. Shapiro said that the upper-level air that was venting from the storm — think of it as if Sandy were taking a deep breath and then letting that air out — was highly asymmetrical, with most of the outflow streaming toward the Midwest “like a great bow wave,” pushing everything in front of it. 

In an interview, Shapiro said that as the storm approached landfall, colder air wrapping into the storm from the west came screaming around the south side of the storm, producing hurricane-force winds on the storm's southwest flank. That surge of cool air played a crucial role in maintaining Sandy's intensity, or even strengthening the storm, Shapiro said, since it sharpened the temperature gradient — or temperature differences — across the storm. He said he can't recall another storm like this, since it had cold air wrapping around an intact warm core. Tropical storms and hurricanes are so-called warm-core systems, while nor'easters and other extratropical systems have cool air near the center of the storm. “It’s a strange dude, you’ll never see another one like that,” Shapiro said.

Whether the storm was still a warm-core system at landfall is fraught with controversy, since the National Weather Service maintains that it had become more akin to a strong nor'easter at the point of landfall, and the National Hurricane Center did not issue hurricane warnings for New Jersey or New York City. The lack of a hurricane warning has major implications for homeowners and insurers, since it means that hurricane insurance deductibles don't kick in. 

The animation above shows modeled particle trajectories that demonstrate how the low level air comes into Hurricane Sandy and then ascends to the outflow jet at the top of the troposphere. The outflow jet can be seen in red colors moving away from the storm, toward the Midwest. Particle trajectories help show how the air was flowing throughout the storm. This was done by simulating the movement of particles inserted into a modeled storm environment. Credit: Science by Mel Shapiro and Thomas Galarneau. Visualization by Alan Norton, NCAR Computational and Information Systems Laboratory, using VAPOR visualization software.

The animation above shows a visualization of model-simulated radar images with horizontal wind vectors at 1,000 meters. Credit: Science by Mel Shapiro and Thomas Galarneau. Visualization by Alan Norton, NCAR Computational and Information Systems Laboratory, using VAPOR visualization software.

The animation above is a visualization of cloud-top temperature, with horizontal wind vectors colored by wind speed, to give a sense of the low-level airflow. Credit: Science by Mel Shapiro and Thomas Galarneau. Visualization by Alan Norton, NCAR Computational and Information Systems Laboratory, using VAPOR visualization software.

The animation above sheds light on some of the physics that went into making Sandy such a formidable storm, by looking at the role played by potential vorticity, which is a measure of atmospheric spin, on the potential temperature isosurface of 330 degrees as well as at 1,000 meters in elevation. Red colors show the highest potential vorticity. Credit: Science by Mel Shapiro and Thomas Galarneau. Visualization by Alan Norton, NCAR Computational and Information Systems Laboratory, using VAPOR visualization software.

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