This page is referenced in a CAREER proposal to the National Science Foundation by Jonathan E. Martin. Animation (in FLI format, click here for more information) of various data sets are displayed here as examples of the power of animation in illustrating elements of the complex behavior of extratropical weather systems.

Figure 2 of the proposal shows an 18h forecast image from a numerical simulation of the April Fool's Day Storm (valid at 0600 UTC 1 April 1997) that buried southern New England in more than two feet (60 cm) of snow. In that diagram several variables are depicted along with a set of 18h trajectories showing the ascent of warm sector boundary layer air in the warm frontal region of the storm. The following animation of the full 24h forecast of that event (initialized at 1200 UTC 31 March) illustrates how the warm frontal ascent was coincident with the development of a low-level PV anomaly. It also demonstrates the relationship between the upper tropospheric PV anomaly, the upper-level jet streak (yellow surface), and the development of the surface cyclone. The evolution of the surface fronts is suggested by the tendency of the 200 m absolute vorticity.

Animation of the 24h forecast from the perspective of Fig. 2 (2.1 Mb)

A similar animation but with a colored horizontal section of sea-level isobars is given in the next example. Note the relationship between the arrival of the significant tropopause depression (upper-level front) and the period of rapid sea-level pressure decrease.

Animation of the 24h forecast from the perspective of Fig. 2 but with colored sea-level isobars. (4.48 Mb)

The relationship between the upper tropospheric PV anomaly and the sea-level isobars can be seen in this plan view showing the 9 km PV (colored) overlayed with the sea-level isobars with values less than 1000 hPa (yellow). Isobars that seemingly "sprout" out of the ground are a result of local sea-level pressure decreases. Note that this occurs just downstream of the large PV gradient aloft; a theoretical point easily illustrated with VIS-5D.

Animation of the 9 km PV (colored) and the sea-level isobars with values greater than 1000 hPa (yellow) (2.4 Mb)

A plan view of the 200 m absolute vorticity shows the dramatic development of near-surface vorticity that was associated with this cyclone. Such a display could be used to demonstrate not only that the surface frontal zones are characterized by large values of vorticity, but also that there is significant structural and dynamical evolution over short periods of time in these cyclones.

Animation of the 200 m absolute vorticity (3.5 Mb)

The relationship between the upper tropospheric jet stream and surface cyclogenesis is easily illustrated in the following animation. The yellow isosurface is the 3-D 55 m/s isotach and is located at about 9 km. The sea-level isobars are colored and outlined in white every 4 hPa. Note how the cyclone deepens to the north of the jet axis and deepens most rapidly as the jet approaches.

Animation of the 55 m/s jet and the sea-level isobars (2.84 Mb)

This view of the 55 m/s jet isotach and the sea-level isobars is taken from the northeast. A set of warm sector, boundary layer trajectories (black lines) that rapidly ascend through the warm/occluded frontal portion of the cyclone are also depicted here.

Animation of the 55 m/s jet and the sea-level isobars as viewed from the northeast with warm sector trajectories (2.84 Mb)

This panel illustrates the evolution of the 312 K equivalent potential temperature surface over the course of the 24h forecast. Of particular interest is the "notch" in the surface that develops over southern New England ~9 hours into the forecast (2000 UTC 31 March). That "notch" is the trowal, a common structural feature of occluded cyclones. Notice how the set of warm sector trajectories (yellow lines) ascends directly through the trowal. These trajectories are the same ones portrayed in other panels in this presentation.

The 3-D structure of the frontal zones is made very clear in this representation of the data. Over a period of time, the student exposed to this type of weather data can acquire deep insights into the structure and evolution of the mid-latitude cyclone.

Animation of the 312 K Theta-E surface with warm sector trajectories overlayed (2.9 Mb)

The animations presented here are in FLI format. If you need information about FLI format or need to acquire an FLI player to view the animations, click here

The software used to animate the UW-NMS model output on this page is called VIS-5D. For more information on VIS-5D, and how you might get a version, click here.

Please send me your comments.

Jonathan Martin (

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