|0600 UTC 1 Nov – 1200 UTC 2 Nov GOES-WEST IR|
Imagery and GFS sea level pressure (black contours)
and 925 mb temperature (color contours) analyses.
|1500 UTC 29 Oct – 0000 UTC3 Oct GOES-East IR|
Imagery, Radar, and Rapid Refresh sea level pressure
(black contours) and 925 mb temperature (color contours) analyses.
As Sandy moved northward, she acquired frontal characteristics that are commonly found in deep extratropical cyclones, such as the one over the Gulf of Alaska above. As we have discussed previously, this process is called extratropical transition. Her tropical warm-core became surrounded by cooler air and an increasingly strong frontal zone. As she made landfall, her thermal, cloud, and precipitation structure was more reminiscent of an extratropical cyclone than a hurricane. Her apparent eye (see last frame) may reflect the bent-back front encircling the low center rather than traditional hurricane eye-wall dynamics. Indeed, deep extratropical cyclones sometimes exhibit eye-like features surrounding the warm-core seclusion.
Drawing a boundary to distinguish between tropical and extratropical cyclones is convenient, but that boundary is ultimately imaginary and arbitrary. Understanding Sandy requires a broader perspective and consideration of both "tropical" and "extratropical" processes and storm characteristics.