Severe Tropical Cyclone Zelia Hits Australia
Overnight in the eastern Indian ocean, a tropical storm underwent significant deepening to become Severe Tropical Cyclone Zelia. The name “tropical cyclone” might make one think of a comparatively weak storm compared to a hurricane, but that is because the names of these systems vary depending on the part of the world they take place. There’s no functional different between a hurricane, typhoon, or severe tropical cyclone, just a different ocean basin where they can be found. The category rankings are the same for all tropical cyclones, and as of sunrise on 13 February, it had become a Catergory 4 storm, with winds over 209 km/h (130 mph). Forecasts from the Australian Bureau of Meteorology indicate that it will continue to strengthen to a Category 5 system before taking a sharp left hand turn and heading south. Zelia is currently lashing the coast with winds and rain as it strengthens, and because of some locations will be under this system for many hours, some rainfall forecasts are in excess of 50 cm (20 inches).
The rapid development of an eye can be seen in the following loop of Band 13 (10.4 microns, the infrared window) from the Advanced Himawari Imager (AHI) aboard Japan’s Himawari-9 geostationary satellite, . Because this eye development took place in the nighttime hours, visible-wavelength imagery cannot be used to observe this process. Longtime viewers of tropical cyclone imagery might be slightly started to see Zelia spinning in a clockwise direction, but that’s expected for a Southern Hemisphere cyclone.
This strong intensification is not unexpected given the extremely warm sea surface temperatures found just northwest of Australia. The NESDIS High Resolution Sea Surface Temperature analysis (available from SSEC’s Real Earth) shows temperatures at or above 25 C (over 77 F), which contribute substantially to the latent heat processes needed for tropical cyclone development and maintenance.
For the latest updates, be sure to check the BOM’s Tropical Cyclone website.