A Convective Explosion with a Developing Hurricane (Imagery credit: www.tropicaltidbits.com)

DISCUSSION: As of earlier this evening, there were several rather intense tropical cyclones spinning in different ocean basins around the world. However, among all these tropical cyclones, there was one particularly interesting tropical cyclone among the large global cluster of ongoing storms. This particularly interesting tropical cyclone was Hurricane Sergio. Even though Hurricane Sergio is only a Category 1 hurricane on the Saffir-Simpson Hurricane Wind Intensity scale as of tonight, there was something rather interesting and profound which occurred tonight as this storm was intensifying.
 
This particularly neat aspect of Hurricane Sergio this evening was the fact that the deep convection which fired on the eastern half of the inner core of Hurricane Sergio has cloud-top temperatures as cold as around -90°C. This is significant in the context of an intensifying tropical cyclone since it is not all that often that one will observe core convection have such cold cloud-tops even during periods of rapid intensification which it did not appear was occurring in association with Hurricane Sergio as of the past few hours. Having said that, it is worth noting that even without a period of rapid intensification occurring with a given tropical cyclone, you can still get very deep, intense convection at times.  This situation which is captured both in the image attached above as well as the brief animated gif of the period during which this deep convection “explosion” occurred.
 
What is most impressive about this convective burst on the eastern half of Hurricane Sergio is the fact that it occurred very unexpectedly with no forecasts being reasonably certain that this sort of convective burst would occur at the time it did. That being said, by the same token, it should also be noted that this storm had been moving over sea-surface temperatures greater than 26°C which is warm enough to support the intensification of tropical cyclones. Nonetheless, this just goes to show that there is still much for atmospheric science to learn about tropical cyclones to be able to make further improvements to tropical cyclone intensity forecasting. 

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© 2018 Meteorologist Jordan Rabinowitz