In this 3-D map of potential temperature, relatively cool air wraps around Sandy's core near the surface (purple and blue colors), while air parcels gain heat from moisture condensing into clouds and precipitation as they ascend through the storm’s core.
From ClimateCentral (by Andrew Freedman)
Scientists have recently developed awe-inspiring visualizations of Hurricane Sandy, which
devastated the Northeast and Mid-Atlantic states a year ago.
The visualizations, created using state-of-the-art computer models,
provide some of most detailed looks at any hurricane to date.
Scientists based at the
National Center for Atmospheric Research (NCAR)
in Boulder, Colo., used an advanced hurricane computer model to create
mesmerizing images and animations that almost succeed in making the
destructive and deadly storm appear to be a beautiful work of art.
The hurricane went through multiple phases.
After rumbling through the
Caribbean and striking Cuba, it veered north-northeastward just off the
East Coast.
The storm was officially classified as a post-tropical
cyclone as of 7 p.m. EDT on Oct.29, 2012, only an hour before it made
landfall, and after hurricane force winds had already begun buffeting
the New York and New Jersey coastlines.
Climate Central
posted the initial round of visualizations
from this team in January.
But now, a team including NCAR's Mel
Shapiro, the National Center for Computing Applications (NCSA), Cray
Computing, and the U.S. Office of Naval Research has produced addition
simulations at even higher resolution.
The visualizations show how Sandy’s life cycle was unique — going
through multiple tropical and non-tropical phases as it interacted with
the jet stream and surface weather features, such as a cold front draped
along the East Coast.
Ultra-fine-scale simulations of Sandy’s near-surface
winds (upper right) and cloud-top temperatures (lower right) closely
resemble the observations derived from satellite data (at left).
Credit: UCAR.
Robert Henson, a meteorologist and science writer with the University Corporation for Atmospheric Research in Boulder
published a story about the new data, explaining the many never-before-seen atmospheric interactions that it reveals.
“As Sandy moved northeast, contrasting air masses created a
pseudo-frontal system along the edge of the Gulf Stream’s warm water.
The vorticity, or circulation, along this frontal zone (picture an
atmospheric rolling pin oriented along the Gulf Stream) was gradually
ingested by Sandy and tilted into vertical vorticity (now picture the
rolling pin standing on one end),” Henson wrote.
“This helped the
storm’s core to intensify, tighten, and regain its Category 2 status.
It’s roughly similar to the smaller-scale process by which a supercell
thunderstorm can ingest, tilt, and concentrate spinning air to produce
storm-scale circulations (some of which can generate tornadoes).”
This intensification came as the storm was shoved westward into the
U.S. by an area of blocking high pressure in northeastern Canada and a
huge dip in the polar jet stream.
Life cycle of Hurricane Sandy: Potential Temperature. Credit: UCAR.
Henson makes an important point about Sandy’s winds, writing, “Even
while Sandy was still a full-fledged hurricane, its circulation was so
large that its northern edges were more akin to an extratropical
(nontropical) cyclone. About 24 hours before Sandy made landfall, cool
air began to wrap around its warm core, eventually surrounding it.
Although this process meant Sandy was doomed as a tropical storm, it
also may have intensified Sandy’s low-level winds.”
On a highly technical level, Henson notes that Sandy developed a rare
“warm seclusion,” which typically occurs in strong winter storms over
the ocean when pockets of warm air form within their cold cores.
As a
hurricane, Sandy had a warm core, meaning that temperatures near the
storm’s center were warmer than the surrounding air, but colder air
eventually worked its way into the center of the storm.
“This is the
first time such a dramatic warm seclusion has been documented in a
landfalling U.S. hurricane,” Henson wrote.
NCAR’s Shapiro worked with the
NCSA to
create the most detailed simulations of Sandy.
In the computer model
runs, each horizontal grid point was separated by just 1,600 feet, a far
more fine-scale presentation than the typical grid boxes used in most
operational computer models used for weather forecasting.
For example,
the National Oceanic and Atmospheric Administration's (NOAA)
highest-resolution operational hurricane forecast model, known as the
HWRF, is currently being run at a resolution of 27 kilometers, meaning
each horizontal grid point is separated by nearly 17 miles.
Life cycle of Hurricane Sandy: Surface Wind Speeds. Credit: UCAR.
The calculations required 58 hours of time on a supercomputer known as
“Blue Waters.
“ Since the model includes 150 vertical layers, that means
that weather conditions were calculated at more than 4 billion points
for each second in a 96-hour simulation,” Henson wrote.
That program is aimed at dramatically
improving forecasters' ability to anticipate changes in tropical storm
and hurricane intensity, which currently lags far behind their ability
to accurately forecast a storm's eventual track.
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