The meteorology behind Hurricane Sandy’s very low pressure
Nearly three years since Hurricane Sandy, many of her visual scars have faded. The memories of the storm, for many, have not. Meteorologically, Sandy remains just as incredible now as she was then — an unbelievable display of atmospheric power. One of the most fascinating aspects of Sandy was how strong she was, despite entering cooler waters. The meteorology behind her pressure is powerful and intricate, still, three years later.
Hurricanes have a strong warm core at the surface, weaken with height, and are barotropic — meaning there are no temperature or density gradients in their environment. This means that they are symmetric — their warm core is entirely surrounded by slightly cooler, but still abundantly warm air. The combination leads to hurricanes being vertically stacked (not tilted with height). Thus, hurricanes need warm water and weak upper-level winds in order to strengthen. Strong upper-level winds can choke a hurricane’s outflow channel, and advect in new airmasses of different temperatures — providing temperature gradients that hinder their development.
In further south latitudes, waters tend to be warmer, and the jet stream tends to be weak. As you head further north, however, the water becomes colder and the jet stream strengthens, leading to stronger upper-level winds. This helps to weaken a hurricane’s warm core at the surface, and tilt its vertically stacked structure, weakening the storm. However, as Sandy headed north, she was able to maintain category one hurricane strength with abnormally low pressures and eventually went on to cause widespread devastation. Why?