Undertstanding the Power of a Hurricane’s ‘Hot Tower’ Clouds

Hurricane Isabel (2003) as seen from orbit during Expedition 7 of the International Space Station. The eye, eyewall and surrounding rainbands that are characteristics of tropical cyclones are clearly visible in this view from space.Photo: Mike Trenchard

We’ve been told that the heart of a hurricane or its “eye” is usually placid and streaming with light. But scientists have found that the region surrounding the eye is swathed in the energy it produces.

Around the heart of the hurricane is a “hot tower” or a convective burst. This phenomenon is thought to form just before the storm strengthens significantly. These ferociously tall clouds may be the reason hurricanes grow stronger so quickly. When viewing photos of hurricanes, hot towers appear as heightened rain clouds reaching above the barrier around the eye of the hurricane.

Hot Tower in Hurricane Bonnie 1998. Altitude of clouds are exaggerated. From NASA.Photo: Josheshi

Talkin’ about Another Kind of Battery Here
The powerful energy given off by the hot towers supplants excessive amounts of power in a shortened time frame, right into the center of a hurricane. This scenario gives the impression of a supercharged boost right into the hurricane’s workings. What you get is decreased surface pressure resulting in faster wind acceleration.

Hurricane Wilma at record intensity southeast of the Yucatan Peninsula on October 19, 2005Photo: Jeff Schmaltz, MODIS Rapid Response Team, NASA, Goddard Space Flight Center

The island of Cozumel is shown through the eye of Hurricane Wilma in this composite image.Photo: NOAA Satellite and Information Service

Fizzling Out? Don’t Think So

The manner in which the sections of air, or vortices, located in the eye convey warm, water-laden air into the hot tower may explain the hurricane’s force not being lost even when it comes across cooler waters. That excess power of the vortices keeps the storm brewing.

Storm pathPhoto: jdorje

Cloud “Modeler”
In the late 1950s, a physicist named Joanne Simpson argued that trade cumulus clouds were significant, and analysis using measurements were vital to understanding how the clouds drove tropical cyclones. She and her team were given the first equipped airplane, an old PBY-6A laden with instruments that measured wind motions, humidity, liquid water, air pressure, temperature and several other variables. The trip, their first, solidified Ms. Simpson’s reputation as a pioneering scientist.

Satellite video of Wilma's lifespanPhoto: NASA

Doubtful But True
Along with that success, Ms. Simpson helped move meteorology in a new direction by revealing a process by which energy brought about by the condensation of water inside tall, rhombus-shaped, cumulonimbus clouds gives off the energy required to sustain the Hadley circulation and keep the trade winds blowing. This was called the “hot tower hypothesis”. It was not well-received, yet Ms. Simpson was able to further show that this hot tower of transferred energy is plausible and that it comes to pass continuously in equatorial regions.

Waves in the trade winds in the Atlantic Ocean-areas of converging winds that move along the same track as the prevailing wind-create instabilities in the atmosphere that may lead to the formation of hurricanes.Photo: NASA

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