June 2011  Tropical Cyclone Season

How do storms get their names and who chooses them? Former MetService Ambassador, Bob McDavitt, explains the history behind naming storms, how they are categorised, and his insight into the 2011 tropical cyclone season that caused widespread damage.

The first storm in our area this season was named TASHA on Christmas Day and very quickly made landfall near Cairns. It played a small part in the annual wet season that has proved so extreme over northern Australia during December and January.

Cyclone VANIA, the second this season, was named near Vanuatu on 12 January. Following that came VINCE, named on the same day off northwest Australia, then by ZELIA which was named on 14 January in the Coral Sea.

The main storms of the season occurred in late January:

On 22 January, WILMA was named near Samoa and the next day ANTHONY was named in the Coral Sea. WILMA sideswiped Northland, Cormandel, and Bay of Plenty on 29 January, and ANTHONY faded as it made landfall over Queensland on 30 Jan. Also on 30 Jan, YASI was named east of Vanuatu. It went west across the Coral Sea and grew to a super Category 5 storm that brought widespread damage to eastern Australia from 3 to 5 February.

Three more cyclones formed north of New Zealand and moved off to the southeast: ZAKA on 6-8 Feb, ATU on 15-23 Feb and BUNE on 23-28 March. BUNE’s eye moved over Raoul Island in the Kermadec Group and this was covered by a MetService blog (http://blog.metservice.com/2011/03/the-eye-of-the-storm/).

West Australia was visited by three cyclones: BIANCA (25-29 Jan), CARLOS (15-26 Feb) and DIANNE (16-22 Feb).

The History of Naming Storms

Christopher Columbus was the first recorded writer about tropical cyclones. For several hundred of years storms were named arbitrarily: an Atlantic storm that ripped the mast off a boat named Antje became known as Antje’s hurricane. In the Spanish-speaking islands of the Caribbean, storms were named after the Saint’s day on which they arrived.

Near the end of the nineteenth century, Australasian meteorologist Clement Wragge named tropical cyclones (and droughts) after political figures. On occasion he described the tropical cyclone in uncomplimentary terms, such as causing distress, displaying erratic behavior, wandering aimlessly, or frequently changing its mind.

During World War II, when American bomber crews flew missions from Micronesian to Japan, they informally used the names of girlfriends and wives for the tropical cyclones they encountered. By the early 1950s, American meteorologists used their phonetic alphabet (ABLE, BAKER, CHARLIE, etc.) to identify tropical cyclones in the Atlantic. Starting in 1953, female names in alphabetical order were used by the US National Weather Service. Then, in the late 1970s, the lists of names were extended to include alternating male and female names.

Who Chooses the Name?

When winds rotating around the core of a cyclone in the tropics build to gale force, the cyclone is given a name to uniquely identify it. This is done by the appropriate Tropical Cyclone Warning Centre (TCWC). The current list of available names is prepared well in advance by the Tropical Cyclone Committee of the World Meteorological Organization (WMO) through its World Weather Watch and Tropical Cyclone Programmes.

Traditionally, the tropical cyclone formation areas are divided into seven basins (see map). To help monitor cyclone activity in these basins, the WMO Tropical Cyclone Programme has established Tropical Cyclone Warning Centres (TCWCs) for each basin. Their areas of responsibility extend across the regional boundaries of the Regional Specialized Meteorological Centres (RSMCs) of the WMO, which are outlined in red on the map. The RSMCs have regional responsibility to provide weather advisories, bulletins and warnings on tropical cyclones, while the TCWCs supplement this work by observing, naming and forecasting tropical cyclones.

In our region, MetService operates the Wellington RSMC, working closely with the Nadi TCWC and the Nadi RSMC (operated by the Fiji Meteorological Service) to coordinate the various bulletins and warnings for our respective areas of responsibility. MetService also serves as a backup for the Nadi TCWC in the event that Nadi experiences an outage. The Australian Bureau of Meteorology runs a TCWC at Brisbane. The naming boundary between the Brisbane and Nadi centres is along longitude 160 degrees East, which explains why the names of cyclones heading for New Zealand may seem to jump around the alphabet.

The Tropical Cyclone Committee provides each TCWC its own list of names. These are chosen to be short, familiar to users, and easy to remember so that their use helps communicate warnings, especially when multiple cyclones have formed. The names are used in alphabetical order, alternating male and female, but occasionally letters such as Q are skipped. Names may be skipped if deemed inappropriate for some reason – e.g. a similarly-named cyclone is already active in the area, or if it matches the name of a public figure currently in the news. Cyclones retain the same name if they cross a regional boundary (except in the Indian Ocean) or if they decay and then regenerate.

In regions such as the northwest Pacific and the Atlantic, each season starts with A on the list. In our part of the world the lists are used sequentially, so the first name used each season is the one immediately following the last one used.

In the Australian list, this season started with Tasha, followed by Vince, then Zelia. Their next alphabet is: Anthony, Bianca, Carlos, Dianne, Errol, Fina, Grant, Heidi, Iggy, Jasmine, Koji, Lua, Mitchell, Narelle, Oswald, Peta, Rusty, Sandra, Tim, Victoria, and Zane.

In the Fiji list, this season started with Vania, followed by Wilma, Yasi, and Zaka. Atu and Bune. Their next alphabet is: Atu, Bune, Cyril, Daphne, Evan, Freda, Garry, Heley, Ian, June, Kofi, Lusi, Mike, Nute, Odile, Pam, Reuben, Solo, Tuni, Ula, Victor, Winston, Yalo, and then Zena.

Categories

Mariners may have heard of the intensity of a tropical cyclone given as a category between one and five. Worldly mariners will have noted that the category scale used in the South Pacific is different from the Saffir-Simpson category scale used around America. (See the chart showing the category scale that applies to the Australia/New Zealand area).

On average, 86 tropical cyclones originate each year, with 47 reaching hurricane strength. These systems act like safety valves, helping to spread out any build-up of heat in the tropical oceans. In the South Pacific the annual average is between eight and ten, of which one reaches New Zealand in nine years out of ten. The South Pacific cyclone season is officially from the start of November to the end of April.

Bob McDavitt retired from the MetService in 2012. FMC thanks Bob for his valued contribution as the Bulletin weather columnist over many years. This column was originally published in the June 2011 FMC Bulletin

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