Jennifer King
IS 247 – Assignment 1
9.21.05
Analysis of a Visualization: “Hurricane Tracks” in National Geographic Magazine,
August 2005, pg. 78-79
I discovered “Hurricane Tracks” in National Geographic magazine and chose it
because it contains both a traditional bar graph composed of quantitative values
combined with a geographic visualization. National Geographic runs “softscience” articles for a general audience, and this visualization appeared in an
article about the risks of hurricanes from warming sea waters.
In detail, the two data sets consist of a bar graph of sea-surface temperatures in
the Gulf of Mexico from 1944 to 2004 (60 years), and two sets of visualizations of
hurricane tracks over the Gulf Coast region in decade-long spans, 1985-1994
and 1995-2004. Each item on the bar graph represents a single year (and
presumably an average of the temperatures for that year — the graph does not
state this explicitly) on the Fahrenheit scale with a midpoint of 83.0°F and a
range between 82.1°F to 83.6°F. The bar graph uses color to differentiate the
years prior to 1985 (grey), 1985-1994 (blue), and 1995-2004 (red). The use of
red and blue serves two purposes: first to denote a cooling cycle versus a
warming cycle, and second to link the bar graph with the corresponding data sets
on the hurricane tracking visualization. The text accompanying the graph
explains that hurricanes rise and fall in multidecadal cycles, providing a rationale
as to why the visualization is focused upon the two most recent ten-year cycles
(additionally, the data appears to neatly adhere to the decadal time frame).
The hurricane track visualization consists of the plotting of hurricane paths over a
map of the southeastern United States and the Gulf Coast. There are two
visualizations: one for years 1985-1994, and one for 1995-2004. Paths on the
1985-1994 map are tracked in blue to correspond to the temperatures on the bar
graph for that decade, which are cooler than the 1995-2004 span tracked in red.
Additionally, the visualization contains a legend illustrating that lower intensity
storms are tracked using thin lines, and higher intensity (category 3-5 hurricanes)
are tracked using thick lines. The use of color (in my opinion) does a better job at
communicating the relationship between hurricane frequency and temperature
than the line thickness does of showing intensity, as it is fairly difficult to clearly
distinguish between the thin and thick parts of the tracks. At the same time, the
impact of this visualization comes more from the difference between the number
of tracks in warmer versus cooler waters than in the difference in intensity. In
fact, if it were possible to count the number of hurricanes tracked in each data set
(not provided) and percentages were calculated of the breakdown between high
and low intensity storms, the actual difference between both may not be that
substantial though the 1995-2004 visualization looks more impressive.
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This visualization is meant to communicate rather than offer data for analysis as
many details that would allow for an independent analysis are missing, such as
whether or not the temperatures in the bar graph represent an average, or the
precise tracks of the hurricanes given in coordinates on a grid. Since the
visualization accompanies a full-length article in the magazine, it is intentionally
simple; the use of bars (rather than lines) clearly show the reader a range along
what must be the average (83.0°F) with temperatures above and below clearly
marked, and the lack of detail in the hurricane tracks only allows for a visual
comprehension rather than, say, offering detailed data about hurricane intensity.
Instead, the use of color both in the bar graph and the tracks traced on the map
are meant to communicate to the user quickly the point the accompanying article
is making: warmer sea-surface temperatures equal more frequent and intense
hurricanes.
This visualization is extremely effective in the role that it serves as an
accompaniment to a feature article about hurricanes. Since the article provides a
more detailed discussion about hurricanes and their frequency, the generality of
this visualization is appropriate for the context and succeeds in illustrating a point
that might be abstract to the reader of the article when considered merely as text.
As it is serving as a visual aid to a general-interest article, I find it forgivable that
some of the data is deliberately obscured, presuming the article fills in the blanks.
Aesthetically, the visualization is well-designed and makes good use of available
space (the top third of two facing magazine pages) without being crowded by
unnecessary detail. The monochrome background of grey land, geopolitical
boundaries (rendered in a noticeable but not overbearing lighter grey), and black
ocean clearly defines but does not detract from the brightly colored hurricane
paths laid atop. The positioning of the bar graph on the right draws the reader’s
attention first and is balanced nicely with the text box on the left. While I find the
intensity levels a bit hard to discern in the hurricane tracks, I’m not sure what
would have made them more distinct — dashed lines? Different colors or hues?
Those solutions might have made the tracks more busy and even less
discernable, so I’m not sure I’d recommend them. In summary, with regards to
audience and context, as well as aesthetics and the perceptual principles we’ve
studied, I think this is a successful visualization that communicates its purpose
clearly.
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