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Tropical Cyclone
Advisories & Warnings
 South-East Indian
 Ocean, Arafura Sea,
 Gulf of Carpenteria,
 Coral Sea, Solomon
 Sea and Gulf of Papua
This web site is operated
on behalf of WMO by

Hong Kong Observatory
of Hong Kong, China.
Terminologies used in the region of South-East Indian Ocean, Arafura Sea, Gulf of Carpenteria, Coral Sea, Solomon Sea and Gulf of Papua
 
  1. Classification of tropical cyclones
  2. Cyclone characteristics
  3. Warning system related terms
  4. Warnings related terms
  5. Meaning of terms used for regional exchange
  6. Names of Tropical Cyclone at South-East Indian Ocean, Arafura Sea, Gulf of Carpenteria, Coral Sea, Solomon Sea and Gulf of Papua
 
 
  1. Classification of tropical cyclones
 
  2. Tropical Cyclone characteristics
 
  3. Warning system related terms
+     Used by Australia and Fiji
*     Used by Fiji
**     Used by Australia, Papua New Guinea, American Samoa and Somoa
***   Used by Australia
   
  4. Warnings related terms
  5. Meaning of terms used for regional exchange
  A  |  B  |  C  |  D  |  E  |  F  |  G  |  H  |  I  |  J  |  K  |  L  |  M  |  N  |  O  |  P  | Q  |  R  |  S  |  T  |  U  |  V  | W  |  X  |  Y  |  Z 
TERM MEANING
Advice See Tropical cyclone advice
   
Alert See Tropical cyclone alert.
   
Average wind speed Speed of the wind averaged over the previous 1**** or 10 minutes.
   
Central pressure Pressure at the centre of the tropical cyclone as measured or estimated.
 
Centre of the tropical cyclone The estimated position of the surface centre.
 
Confidence in the centre position Degree of confidence in the centre position of a tropical cyclone expressed as the radius of the smallest circle within which the centre may be located by the analysis.
  • Position good implies a radius of less than 30 nautical miles (55 kilometres).
  • Position fair, a radius of 30 to 60 nautical miles (55 to 110 km) and
  • Position poor, a radius of greater than 60 nautical miles (110 km).
 
Convergence zone A zone where air streams of different directions or speeds merge.
 
Cyclone See Tropical cyclone
 
Depression A synoptic low pressure area with extra-tropical characteristics where the average wind speed may exceed 33 knots (63 km per hour) or Beaufort Force 7.
   
Direction of movement
of the tropical cyclone
The direction towards which the centre of the tropical cyclone is moving.
   
Eye of the tropical cyclone The relatively clear and clam area inside the circular, convective wall clouds.
   
Gale force wind Average surface wind speed of 34 to 47 knots (63 to 87 km per hour or wind force of 8 or 9 in the Beaufort Scale).
   
Gale warning Meteorological message intended to warn those concerned of the occurrence or expected occurrence of gale force winds.
   
Gust Sudden, brief increase of the wind speed over its average value.
   
Hurricane or severe tropical cyclone A tropical cyclone with hurricane force winds.
   
Hurricane force wind Average surface wind speed 64 knots (118 km per hour, Beaufort Force 12) or more.
   
Hurricane warning Meteorological message intended to warn those concerned of the impact of a tropical cyclone with hurricane force winds.
   
Intertropical Convergence Zone (ITCZ) A relatively narrow zone where the trade winds from both the Northern Hemisphere and the Southern Hemisphere merge.
   
Mean wind speed See Average wind speed.
   
Monsoon depression
= Monsoon low
A tropical depression (or tropical low) embedded in the monsoon trough.
   
Monsoon trough A shear zone with westerly monsoon winds on the equatorial side and easterly trade winds on the polarward side.
   
Naming a Tropical Cyclone A non-frontal low pressure system of synoptic scale developing over warm waters will be named whenever observations and/or Dvorak intensity analysis indicate the presence of gale force or stronger winds near the centre which are likely to continue.
   
South Pacific Convergence Zone (SPCZ) A semi-permanent convergence zone found in the tropical South Pacific marked by the boundary between the usually cooler and stronger southeast trade wind flow and warmer and lighter east or northeast winds, or northwesterly winds when the SPCZ is active.
 
Special Advisory A message to a National Meteorological Centre giving information on a tropical disturbance or a tropical cyclone.
 
Special Weather Bulletin Bulletins issued, whenever the need arises, to put the community on the alert, to give progress reports on development or to give specific warnings of tropical cyclones or other disturbances.
 
Speed of movement
of the cyclone
Speed of movement of the centre of the tropical cyclone.
 
Storm force wind Average surface wind speed of 48 to 63 knots (88 to 117 kilometres per hour or Beaufort Fource 10 or 11).
 
Storm surge The difference between the actual sea level under the influence of a meteorological disturbance (storm tide) and the normal astronomical tide.
 
Storm tide The actual sea level as influenced by a weather disturbance. The storm tide consists of the normal astronomical tide and the storm surge.
 
Storm warning* Meteorological message intended to warn those concerned of the impact of storm force winds.
 
Sustained wind speed See Average wind speed.
   
Tropical cyclone A non-frontal low pressure system of synoptic scale developing over warm waters and having a definite organized wind circulation with a maximum 10-minute average wind speed of 34 knots (63 km per hour, ie. gale force) or greater near the centre.
 
Tropical cyclone advice A tropical cyclone watch and/or a tropical cyclone warning.
 
Tropical cyclone alert A special weather bulletin providing information on the progress of a cyclone still some distance away and with a significant probability of giving gales or stronger winds to a community in the next 24 to 48 hours.
   
Tropical cyclone season The period of the year with a relatively high incidence of tropical cyclones. In the South Pacific and South-East Indian Ocean, it is the period from 1 November to 30 April.
(Note: cyclones occasionally occur outside of this period.)
 
Tropical cyclone warning A warning of gales or stronger winds associated with a tropical cyclone occurring within 24 hours.
   
Tropical cyclone watch A forecast message of gales or stronger winds associated with a tropical cyclone occurring after 24 hours and before 48 hours.
 
Tropical cyclone year 1 July to 30 June.
 
Tropical depression
= tropical low
A tropical disturbance with a clearly defined cyclonic wind circulation in which the central position can be estimated, and a maximum 10-minute average wind speed of less than 34 knots (63 km per hour ie. gale force) near the centre. There may be gale force or stronger winds in one or more quadrants but not near the centre.
 
Tropical disturbance A non-frontal system of synoptic scale originating over the tropics with persistent enhanced convection and/or some indications of cyclonic wind circulation.
 
Tropical Disturbance Advisory / Bulletin / Summary A message for exchanging information, internationally, on a range of disturbances including tropical depressions and tropical cyclones.
 
Tropical low See Tropical depression
 
Tropical storm A tropical cyclone with gale or storm force winds.
 
Trough or trough of low pressure An elongated zone of low pressure, V-shaped in the easteries in the Southern Hemisphere and an inverted V-shape in the westerlies. The axis of a trough is known as the trough line.
 
Watch See Tropical Cyclone Watch
 
Wave setup Localised increase in the still-water sea level produced by breaking waves close to the shore.
   
Weather Bulletin A bulletin issued at regular times to give weather information and forecasts to the general public or marine interests.
   
* Storm warning: Papua New Guinea uses the term for all events with storm force or stronger winds
**** Used by Micronesia and USA (American Samoa)

The above information is extracted from World Meteorological Organization Technical Document, Tropical Cyclone Programme, Report No. TCP-24, Typhoon Cyclone Operational Plan for the South Pacific and South-East Indian Ocean, 2008 Edition
If you have any suggestions, please send an email to swic_wm@worldweather.org.