A Tropical Cyclone Wind Signal (TCWS) is a plain text warning to particular land area that may experience winds of at least strong breeze in strength on the Beaufort Scale (i.e., 39 km/h, 22 kt or higher) within at most 36 hours from the time the signal is put into effect during the passage of a tropical cyclone. A particular wind signal has an equivalent expected wind threat, length of time (in hours) before onset of expected wind threat, and potential impacts to the locality. The current TCWS system uses five (5) levels of wind signals that are numbered from 1 to 5, with a higher signal number associated with higher general wind strength and shorter warning lead time.
The following must be taken into consideration when using the TCWS system:
- The TCWS is meant to warn the public of the threat of general wind strength associated with a tropical cyclone. Owing to the presence of natural and artificial obstructions such as local topography or nearby buildings, winds in a particular area (local winds) may be substantially stronger from the general wind strength over the provincial or sub-provincial locality implied by the wind signal. For instance, local winds are generally stronger over offshore water and on high ground (i.e., on mountainous areas) and are weaker in areas that are sheltered from the prevailing wind direction.
- A wind signal is usually hoisted at the level of a province, independent component city, or highly urbanized city (except for Metro Manila who is collectively placed under a single wind signal level). However, if the meteorological situation requires, a wind signal can be issued at the level of a city or municipality.
- The extent and timing of hoisting of wind signals are based on the intensity, extent of strong winds or higher, and the forecast direction and speed of movement of the tropical cyclone at the time of issuance of a bulletin. As such, any change in intensity, extent of strong winds or higher, or movement of the tropical cyclone also determines the change in the wind signal over a given locality.
- Although the TCWS is a tiered system, the escalation or de-escalation of wind signals allows the skipping of wind signal levels. For instance, Wind Signal #1 on a particular locality can be upgraded directly to Wind Signal #3 without passing Wind Signal #2. However, this is only observed if the issuance of an intermediate tropical cyclone bulletin is not sufficient to rapidly change the level of the hoisted wind signal over a locality.
The current TCWS system has been in use since 23 March 2022 based on the adoption of best practices from other tropical cyclone warning centers and regionally-accepted operational standards, developments in objective forecast guidance, operational experiences and challenges encountered by typhoon forecasters, and feedback from end-users and stakeholders.
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Tropical Cyclone Wind Signal
Tropical Cyclone Wind Signal #1
WIND THREAT: 39-61 km/h (22-33 kt, 10.8-17.1 m/s)
WARNING LEAD TIME: 36 hours
POTENTIAL IMPACTS:
- House of poor construction (e.g., wood frame, bamboo, makeshift), old dilapidated structures, and other structures made of light materials will suffer minimal to minor damage.
- Some banana and similar plants are tilted, while twigs of small trees may sway with the wind. Rice crops, especially those in flowering and ripening stages, may suffer some damage.
- Minimal disruption to public transportation.
