Fujiwhara effect
From Biocrawler, the free encyclopedia.
The Fujiwhara effect or Fujiwhara interaction is a type of interaction between two nearby cyclonic vorticies. When the vorticies approach each other, their centers will begin orbiting cyclonically about a point between the two systems. The two vorticies will be attracted to each other, and eventually spiral into the center point and merge. When the two vorticies are of unequal size, the larger vortex will tend to dominate the interaction, and the smaller vortex will orbit around it.
The effect is named after Dr. Sakuhei Fujiwhara, the future chief of the Central Meteorological Bureau in Tokyo, who initially described it in a 1921 paper about the motion of vorticies in water.
The effect is often mentioned in relation to the motion of tropical cyclones, although the final merging of the two storms is uncommon. The effect becomes pronounced in these storms when they approach within about 1450 km (900 miles) of each other, and are at tropical storm strength or better.
A few sets of examples can be found in the busy 1995 Atlantic hurricane season. During the height of the season, Hurricane Humberto and Hurricane Iris took part in a brief Fujiwhara interaction. Iris then began interacting with a third storm, Tropical Storm Karen, which orbited and later merged with the more intense Iris. That same year in the Pacific, Typhoon Pat and Typhoon Ruth completed a full orbit around their centroid before collapsing into a single cyclone.
Sources
- USA Today - "Fujiwhara effect describes a stormy waltz" (http://www.usatoday.com/weather/wfujiwha.htm)
- Joint Typhoon Warning Center - Typhoon Pat (http://www.npmoc.navy.mil/jtwc/atcr/1994atcr/pdf/wnp/29w.pdf) (PDF)
- Edward N. Rappaport, NOAA Hurricane Research Division - "Hurricane Iris Preliminary Report" (http://www.aoml.noaa.gov/hrd/prelim/Iris_prelim.html)
