Radius of outermost closed isobar

{|class="wikitable" style="float: right; font-size: 92%; margin-right: 0px;" ! colspan=2 style="background: #ccf;" | Size descriptions of tropical cyclones |- ! ROCI || Type |- | Less than 2 degrees latitude || Very small/midget |- | 2 to 3 degrees of latitude || Small |- | 3 to 6 degrees of latitude || Medium/Average |- | 6 to 8 degrees of latitude || Large |- | Over 8 degrees of latitude || Very large |- |}

The radius of outermost closed isobar (ROCI) is one of the quantities used to determine the size of a tropical cyclone. It is determined by measuring the radii from the center of the storm to its outermost closed isobar in four quadrants, which is then averaged to come up with a scalar value. It generally delimits the outermost extent of a tropical cyclone's wind circulation.

Use of this measure has objectively determined that tropical cyclones in the northwest Pacific Ocean are the largest on Earth on average, with North Atlantic tropical cyclones roughly half their size. Active databases of ROCI are maintained by the National Hurricane Center for systems tracked in the eastern north Pacific and north Atlantic basins. Provided by Wikipedia