These visualizations show how the NCAR-based Advanced Hurricane WRF (Weather Research and Forecasting Model) has depicted various aspects of Hurricane/Superstorm Sandy unfolding over four days (96 hours) in October 2012, from 1200 GMT / 8:00 am EDT 10/26/12 to 1200 GMT / 8:00 am EDT 10/30/12. The model simulations were updated every second. In these videos, each frame is separated by 30 minutes of model time. Each segment in this compilation includes a full-frame visualization, followed by a zoomed-in version of the same sequence that shows the highest-resolution results (500 meters between points). All segments include vectors that show horizontal wind speed and direction at 1000 meters (about 3300 feet) above mean sea level. The length and color of the wind vectors correspond to wind speed (legend not shown). Longer vectors denote stronger winds. Each segment is also available as a separate video in this Playlist. --Simulation 1: (00:32--01:44) Temperature of the atmosphere at cloud-top height, overlaid with 1000-meter horizontal wind vectors. Shading of clouds corresponds to cloud-top temperature in degrees C (legend at upper left). Higher cloud tops are generally colder. --Simulation 2 (01:44--02:57) Maximum simulated radar reflectivity, overlaid with 1000-meter horizontal wind vectors. Colors indicate the reflectivity (in units dBZ) that a network of radars would observe if located across the ocean and nearby land. Warmer colors (higher dBZ) generally indicate more intense precipitation. . --Simulation 3 (02:58--04:12) Potential temperature at 1000 meters above mean sea level, overlaid with 1000-meter horizontal wind vectors. Potential temperature is the temperature that a parcel of air would achieve if it were raised or lowered from a given pressure height to the 1000-millibar pressure height. Values are shown in degrees Celsius (legend at upper left). --Simulation 4 (04:12--05:26) Wind speed at 1000 meters above mean sea level, overlaid with 1000-meter horizontal wind vectors. Color field denotes wind speed in meters per second (1 m/s = 2.24 mph). --Simulation 5 (05:27--06:20) Trajectories of air parcels, overlaid with 1000-meter horizontal wind vectors. Each strand shows the path taken by an air parcel over time, starting at the 1000-meter level. The model tracks new air parcels from the 1000-meter level as if the parcels were "seeded" every four hours, but no cloud seeding has occurred (the term refers to instructions given to the model to track a new parcel). Colors indicate potential temperature in Kelvins (legend at upper left; 273 K = 0°C = 32°F). This is the temperature each parcel would achieve if it were raised or lowered from a given pressure level height to the 1000-millibar height. When moisture in a rising air mass condenses to form clouds and precipitation, the heat added to the atmosphere through condensation can cause the potential temperature of an air parcel to increase. ABOUT THE COMPUTER MODELING Researchers began with observations collected at the beginning of the four-day period. They started, or initialized, the AHW model with those data. The model itself, which captures the atmospheric physics associated with hurricanes, then predicted Sandy's behavior over the following four days. The resulting "hindcast" (a forecast conducted after the fact) closely matches the actual behavior of the hurricane/superstorm. The modeling was performed using the Blue Waters Cray XE6 supercomputer at the National Center for Supercomputing Applications (NCSA). The simulation and resulting visualizations are among the most detailed ever conducted for a particular hurricane, with conditions tracked every 500 meters (about 1,600 feet) horizontally. Since the model includes 150 vertical layers, this means that weather conditions were calculated at more than four billion points for each second in the 96-hour simulation. Related story: http://www2.ucar.edu/atmosnews/opinion/10150/new-views-sandy CREDITS Science: Mel Shapiro and Thomas Galarneau, NCAR Visualization: Alan Norton, NCAR, using VAPOR (Visualization and Analysis Platform for Ocean, Atmosphere, and Solar Researchers: http://www.vapor.ucar.edu/) Simulation: Mark Straka, NCSA, and Peter Johnsen, Cray Inc. Postproduction: Perry Domingo, NCAR

• published: 26 Sep 2013
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