All hurricanes begin as a swirling mass of thunderstorms. In most cases, hurricane development goes no further; but in a few, the thunderstorms consolidate into a distinct tropical wave. The National Hurricane Center designates such areas of interest with a letter-number combination (eg. L97). The process of naming a hurricane has begun.
The number assigned to these areas of interest cycles constantly between 90 and 99. The letter represents the hurricane region: “L” (Atlantic), “E” (eastern Pacific), “P” (south Pacific), “C” (central Pacific), “W” (western Pacific), “A” (Arabian Sea), “B” (Bay of Bengal), and S (southern Indian Ocean). Each region has its own separate number cycle. The next tropical wave to arise is given the next number in the cycle, whether or not the previous wave is still active. Thus far, there have never been more than ten tropical waves to watch at a time, so these same letter-number combinations are used again and again.
The tropical wave is now monitored until it either dies out completely or develops a closed convection. Systems which have almost died out continue to be monitored, as they can sometimes spring back into life upon entering an area where the conditions are more condusive to development. If the convection closes, the tropical wave designation is replaced with a tropical depression designation consisting of TD plus a number (eg. TD3).
The next step in naming a hurricane comes when the sustained winds of this system reach 39 mph (62 kph). At this point, the tropical depression officially graduates into a tropical storm and is given a name. This name will remain with that storm from that point onward, up until it loses its closed convection.
Prior to 1951, tropical storms and hurricanes were not named. Rather, they were referred to by their latitude and longitude; but it was quickly discovered that using short, distinctive names for storms led to far less confusion in storm-tossed communication. The new practice of naming a storm may have indirectly derived from the centuries-old Caribbean custom of naming storms for the saint’s day on which they struck an island, or perhaps from the much more recent World War II practice of naming storms (and bombers) after wives and girlfriends. For two years, the United States experimented with trying to name storms for the radio phonetic alphabet (Able, Baker, Charlie), but it never really caught on.
In 1953, the United States introduced the modern practice of giving all tropical storms familiar female names. It was not until 1979 that storms achieved gender equality and male names were included as well.
For the purpose of naming tropical storms and hurricanes (typhoons or cyclones outside the Atlantic), the waters of the world are divided into twelve zones:
* Atlantic * Eastern North Pacific * Central North Pacific * Western North Pacific * Western Australian * Northern Australian * Eastern Australian * Fiji * Papua New Guinea * Philippines [PAGASA] * Northern Indian * Southwest Indian *
Each region names only those storms which originate within their region. The name remains with the storm thereafter, even if the storm moves into a new region. Each region uses its own pre-established lists of names and has its own conventions to establish lists and change between them.
(There is an exception to the rule. Both the United States and Japan also track storms within the entire Pacific region: which can result in a Pacific storm having two names, especially within the Philippines [PAGASA] region.)
The United States (Atlantic, Eastern North Pacific) and the Australian regions use alternating male and female lists of 21 names in alphabetical order. The lists used by the United States and two Australian regions omit the letters Q, U, X, Y, and Z, ending the list at W. The Western Australian list alternates its ending names between W, Y, and Z.
In a unique approach, each country which is part of the Western North Pacific region providees one name drawn from the natural world (such as Nari, which means “Lily”) to the list. These names are then arranged alphabetically by the providing country.
The lists used by the United States start anew each year, using Greek letters if a given list runs out of names (as happened in 2005). Every other region uses its lists sequentially, beginning each new year with the next name in the previous year’s list.
Despite this system, a few post-1953 hurricanes never do receive names. Such a discrepency can occur whenever an accurate measure of the strength and circulation of a storm is not possible before the storm dissipates. Storms which had not entered the Caribbean Sea may never have been measured by Hurricane Hunters before they fell apart. In these cases, post-storm and post-season analyses may show that the storm did indeed achieve tropical storm or even hurricane strength. In the satellite era, post-season analysis can suggest a more accurate measurement of windspeed, sometimes promoting a tropical depression to tropical storm or a tropical storm to hurricane. The naming convention here is to leave the storm unnamed, but to assign it a number instead.
One of the most famous unnamed hurricanes of modern times is the Unnamed Hurricane of 1975, which came out of nowhere to strike the Pacific Northwest with devastating force. It is now recognised that on the last day of August, a cold-core low absorbed the remnants of Ilsa over warm waters of up to 82 degrees F (28 degrees C), enabling explosive intensification into a category 1 hurricane. Unfortunately for the residents of the Pacific Northwest, the Unnamed Hurricane was also such a small, tight storm that the nearest ship was well outside its tropical radius (not much larger than Cyclone Tracy the previous year) and measured only 40 mph (65 kph) winds. Satellite imagery does clearly show the eye, but at the time satellite data was not widely available to meteorologists, as it is today.
One convention all meteorological services hold in common is to retire the name of a tropical storm, cyclone, typhoon, or hurricane which has resulted in particularly high destruction or loss of life. This name will be replaced on future rotational lists by another pre-determined name starting with the same letter. Once a storm has caused that much devastation and heartbreak, there will never again be a storm which shares its name.
