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Tropical Cyclone
Advisories & Warnings
 Western North Pacific
 Ocean and South
 China Sea
This web site is operated
on behalf of WMO by

Hong Kong Observatory
of Hong Kong, China.
Terminologies and Acronyms used in the region of Western North Pacific and
the South China Sea by the Typhoon Committee Members
 
  1. General
  2. Classification of tropical cyclones
  3. Tropical cyclone characteristics
  4. Terms related to the warning and warning system
  5. Meaning of terms used for regional exchange
  6. Acronyms
  7. Names of Tropical Cyclone at Western North Pacific and the South China Sea
 
  1. General
  • Typhoon Committee Members
 
  2. Classification of tropical cyclones *
* Tropical cyclone is a generic term that includes tropical depression, tropical storm, severe tropical storm and typhoon.
 
  3. Tropical cyclone characteristics
 
  4. Terms related to the warning and warning system
 
  5. Meaning of terms used for regional exchange
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TERM MEANING
Average wind speed Speed of the wind averaged over the previous 10 minutes (mean surface wind) as read from the anemogram or the 3 minutes mean determined with the non-recording anemometer or estimated wind at sea by mariners using the Beaufort scale.
   
Bulletin Cyclone warning bulletin
   
Central pressure of a tropical cyclone Surface pressure at the center of the tropical cyclone as measured or estimated.
 
Centre fix of the tropical cyclone The estimated location of the center of a tropical cyclone.
 
Centre of the tropical cyclone The center of the cloud eye, or if not discernible, of the wind/pressure center.
 
Confidence in the center position Degree of confidence in the center position of a tropical cyclone expressed as the radius of the smallest circle within which the center may be located by the analysis.
  • Position good implies a radius of 30 nautical miles (55 kilometres) or less.
  • 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).
 
Cyclone Tropical cyclone
 
Cyclone warning bulletin A priority message for exchange of tropical cyclone information and advisories.
   
Direction of movement
of the tropical cyclone
The direction towards which the center of the tropical cyclone is moving.
   
Extra-tropical cyclone Low-pressure system which develops in latitudes outside the tropics.
 
Eye of the tropical cyclone The relatively clear and calm area inside the circular wall of convective clouds, the geometric center of which is the center of the tropical cyclone.
   
Gale force wind Average surface wind speed of 34 to 47 knots.
 
Gale warning Meteorological message intended to warn those concerned of the occurrence or expected occurrence of average wind speed in the range of 34 to 47 knots, or wind force 8 or 9 in the Beaufort scale.
 
Gust Instantaneous peak value of surface wind speed.
   
Low pressure area Region of the atmosphere in which the pressures are lower than those of the surrounding region at the same level. (On the weather map, the low pressure area is denoted with the capital L within the innermost isobar without showing the center position.)
   
Maximum sustained wind Maximum value of the average wind speed at the surface.
 
Mean wind speed Average wind speed.
   
Reconnaissance aircraft center fix
of the tropical cyclone, vortex fix
The location of the center of a tropical cyclone obtained by reconnaissance aircraft penetration.
   
Severe tropical storm A tropical cyclone with the maximum sustained winds of 48 knots (24.5 m/s, 89 km/h) to 63 knots (32.6 m/s, 117 km/h) near the center.
 
Speed of movement of the tropical cyclone Speed of movement of the center of the tropical cyclone.
 
Storm force wind Average surface wind speed of 48 to 63 knots.
 
Storm surge The difference between the actual water level under the influence of a meteorological disturbance (storm tide) and the level which would have been attained in the absence of the meteorological disturbance (i.e. astronomical tide).
(Storm surge results mainly from the shoreward movement of water under the action of wind stress. A minor contribution is also made by the hydrostatic rise of water resulting from the lowered barometric pressure).
 
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 occurrence or expected occurrence of average wind speeds in the range of 48 to 63 knots or wind force 10 to 11 in the Beaufort scale.
 
Sub-tropical cyclone A low pressure system, developing over sub-tropical waters which initially contains few tropical characteristics. With time the sub-tropical cyclone can become tropical.
   
Sustained wind speed Average wind speed. Average period of one, three or ten minutes is depending upon the regional practices.
   
Tropical cyclone Generic term for a non-frontal synoptic scale cyclone originating over tropical or sub-tropical waters with organized convection and definite cyclonic surface wind circulation.
(The term is also used for a storm in the South-West Indian Ocean in which the maximum of the sustained wind speed * is estimated to be in the range of 64 to 90 knots and in the South Pacific and South-East Indian Ocean with the maximum of the sustained over 33 knots.)
 
Tropical cyclone advisory A priority message for exchanging information, internationally, on tropical cyclones.
 
Tropical depression A tropical cyclone with the maximum sustained winds of 33 knots (17.1 m/s, 61 km/h) or less near the center.
 
Tropical disturbance A non-frontal synoptic scale cyclone originating in the tropics or sub-tropics with enhanced convection and light surface winds.
 
Tropical storm A tropical cyclone with the maximum sustained winds of 34 knots (17.2 m/s, 62 km/h) to 47 knots (24.4 m/s, 88 km/h) near the center.
 
Tropical wave A trough or cyclonic curvature maximum in the trade wind easterlies or equatorial westerlies. The wave may reach maximum amplitude in the lower middle troposphere, or may be the reflection of an upper-troposphere cold low or equatorial extension of a mid-latitude trough.
 
Typhoon A tropical cyclone with the maximum sustained winds of 64 knots (32.7 m/s, 118 km/h) or more near the center.
 
Typhoon force wind Average surface wind speed of 64 knots or more.
 
Typhoon warning Meteorological message intended to warn those concerned of the occurrence or expected occurrence of the mean wind speed of 64 knots (32.7 m/s, 118 km/h) or higher, or wind force 12 in the Beaufort scale.
   
Visual storm signals Visual signals displayed at coastal points to warn ships of squally winds, gales and tropical cyclones.
   
Weather warning Meteorological message issued to provide appropriate warnings or hazardous weather conditions.
   
Zone of disturbed weather A zone in which the pressure is low relative to the surrounding region and there are convective cloud masses which are not organized.
   
 
  6. Acronyms
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TERM MEANING
AFTN Aeronautical Fixed Telecommunication Network
AIREP Aircraft En-route Report
APT Automatic Picture Transmission
ASDAR Aircraft to Satellite Data Relay
   
DPSK Differential Phase-Shift Keying
   
EIR Enhanced Infrared
ESCAP Economic and Social Commission for Asia and the Pacific
   
FAX Facsimile
   
GMS Geostationary Meteorological Satellite
GOES Geostationary Operational Environmental Satellite
GTS Global Telecommunication System
   
HRPT High Resolution Picture Transmission
   
IR Infrared
   
JMA Japan Meteorological Agency
JTWC Joint Typhoon Warning Centre
   
LTP Long Term Plan
   
MANAM Manual Amendment
MDUS Medium Scale Data Utilization Station
MOS Model Output Statistics
MSL Mean Sea Level
MTI Moving Target Indicator
   
NESDIS National Environmental Satellite, Data and Information Service
NMC National Meteorological Centre
NMS National Meteorological Service
NOAA National Oceanic and Atmospheric Administration
NWP Numerical Weather Prediction
   
OPMET Operational Meteorological Data
   
RADOB Report of ground radar weather observation
RMC Regional Meteorological Centre
ROBEX Regional OPMET Bulletin Exchange
RSMC Regional/Specialized Meteorological Centre
RTH Regional Telecommunication Hub
   
SDUS Small Scale Data Utilization Station
S.VISSR Stretched VISSR
SAREP Report of synoptic interpretation of cloud data obtained by a meteorological satellite
SST Sea Surface Temperature
   
TC Typhoon Committee
TCP Tropical Cyclone Programme
TEMP Upper-level pressure, temperature, humidity and wind report from a land station
TOPEX Typhoon Operational Experiment
   
UNDP United Nations Development Programme
UTC Universal Time Coordinated
   
VIS Visible
VISSR Visible and Infrared Spin Scan Radiometer
   
WMC World Meteorological Centre
WMO World Meteorological Organization
WWW World Weather Watch
   
The above information is extracted from World Meteorological Organization Technical Document, Tropical Cyclone Programme, Report No. TCP-23, Typhoon Committee Operational Manual, Meteorological Component, 2005 Edition
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