South Atlantic Hurricanes
Why are hurricanes rare in the South Atlantic? NOAA P-3 flying in eye of Hurricane Caroline. Note circular eye below aircraft. © NOAA
DB: This is Earth and Sky. At the Witte Museum in San Antonio, Texas, we recorded this question:
Alex Garcia: Hi, my name is Alex Garcia. Here’s my question: Why aren’t there any hurricanes in the South Atlantic Ocean?
JB: Alex, hurricanes can occur in the South Atlantic. A storm system scientists are calling a combination hurricane/tropical cyclone killed three people and destroyed 200 homes in Brazil last March. But South Atlantic hurricanes are rare.
DB: To make a hurricane, you need warm ocean water and weak, uniform winds overhead. If the wind increases too quickly or changes direction with height – that is, if there’s wind shear – then the hurricane is torn apart before it can start. In the South Atlantic, the water is generally cooler. There’s more wind shear, so hurricanes can’t organize.
JB: Also, the tropical North Atlantic has what’s called the “intertropical convergence zone,” where the trade winds from the northern and southern hemispheres converge. This special zone stays near or north of the equator throughout the year – a result of there being more land mass in the northern hemisphere than the southern. It spawns thunderstorms that can coalesce to form a hurricane – and it helps supply rotation to hurricanes.
DB: The result is that most hurricanes happen in the North Atlantic. Thanks for your question, Alex. And with thanks to the National Fish and Wildlife Foundation, we’re Block and Byrd for Earth and Sky.
Come see Earth & Sky’s Photo Gallery: Eyewitness photos from inside a hurricane.
Websites of interest:
National Weather Service – National Hurricane Center
Hurricane Hunters – the 53rd Weather Reconnaissance Squadron
Hurricane and Storm Tracking for the Atlantic and Pacific Oceans
Miami Museum of Science – Hurricane Main Menu
NOAA Satellite Services Division – Hurricane Catarina, 2004
NASA Earth Observatory Newsroom – Rare South Atlantic Tropical Cyclone
NASA Earth Observatory Newsroom – ““Hurricane” Catarina Strikes Brazil”:http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=16505
The following people were interviewed for today’s program. Our thanks to:
Dr. Courtney Schumacher
Assistant Professor
Department of Atmospheric Sciences
Texas A & M University
Dr. John W. Neilsen-Gammon
Professor and Texas State Climatologist
Department of Atmospheric Sciences
Texas A & M University
Additional Teacher Resources
NASA, Looking at Earth: Rare South Atlantic Tropical Cyclone
The South Atlantic is generally not thought of by meteorologists as a place where tropical cyclones form. The water temperatures are generally too cool and the vertical wind shear too strong. The area, so devoid of tropical storm activity that no government agency has an official warning system there, which is why this storm is unnamed.
NASA, Headlines: The Nameless Hurricane
On March 28th, a surprising hurricane crashed into the coast of Brazil. This article deals with the climatic implications.
