DISCUSSION: There is no debate that the Friday morning landfall of Tropical Cyclone Fani brought about truly horrific consequences for a good portion of the eastern half of the subcontinent of India. Having said that, with most of the worst of the event having unfolded and concluded up to this point in time, is most certainly worth it and necessary to take a look back and see how this event unfolded. More specifically, it is often most interesting to evaluate how and to what extent the physical structure of a given tropical cyclone evolves during its lifetime and more specifically during its landfall and post-landfall period(s), respectively.
Through utilizing the Cooperative Institute for Meteorological Satellite Studies (CIMSS) Morphed Integrated Microwave Imagery at CIMSS (MIMIC), there are several more profound insights which can be gained from this recent and historic tropical cyclone which formed and intensified within the Bay of Bengal (i.e., to the south and east of eastern India). First off, upon analyzing the pre-landfall phase of Tropical Cyclone Fani, you can clearly see how it maintained a structurally-sound eye and eye-wall. You can determine the fact that it had a structurally-sound eye-wall by seeing how towards the beginning of the brief loop, there was a relatively consistent coverage of yellow to red-colored banding around the clear eye which indicates the presence of deeper convection surrounding the immediate center of the storm’s circulation. Thus, as you may suspect, this was around the time at which Tropical Cyclone Fani was near and around the period of peak intensity.
After that time, upon a bit closer investigation, you can also see how there was a slight widening of the average diameter of the eye in the hours leading up to the landfall of Tropical Cyclone Fani. A gradual widening of an eye during the last 24 hours preceding a landfall is quite common with tropical cyclones around the world (under most environmental circumstances) and is most often an indication of a process known as an eyewall replacement cycle occurring. During this process, the common consequences to an average tropical cyclone is that there is a widening of the eyewall, a corresponding increase in the size of maximum wind speed field, and sometimes a weakening of the maximum wind speeds by at least 5 to 15% of the original maximum sustained wind speeds.
Once the storm made landfall, you can then observe how the storm fully broke down in terms of its organization and that the eye collapsed quickly which is an inevitable factor when a tropical cyclone interacts with any sizable landmass. Such landmass interactions degrade the internal structure and organization of a tropical cyclone since this interaction cuts off the critical inflow of warm, moist air towards the center of the storm. Thus, this process facilitates a rapid weakening of the storm from that point forward and this is exactly what you are seeing with Tropical Cyclone Fani during the post-landfall phase of this tropical cyclone as it moved northward towards southern Bangladesh.
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© 2019 Meteorologist Jordan Rabinowitz