Tropical Cyclone Wind Signals
They are escalated, de-escalated or lifted depending on the expected strength of winds and the movement of the tropical cyclone relative to the affected areas.
[6] It was subject to further revisions after the catastrophic onslaught of Typhoon Haiyan (Yolanda) in 2013, which prompted the addition of a fifth warning level to emphasize extreme tropical cyclone winds.
The TCB also contains a plain-text discussion of the hazards threatening land and coastal waters and the PAGASA's track and intensity outlook for the cyclone.
Wind signals are hoisted and updated (escalated, de-escalated or lifted) usually in regular time intervals coinciding with the release of a TCB:[14] TCBs can also be released only twice a day (every 12 hours) when the tropical cyclone is too far away that it does not affect the Philippine landmass (whether or not the tropical cyclone is approaching the landmass), in which case no TCWS signals are raised.
Contrary to common misconception and as implied by its name, the purpose of the TCWS system is to warn the public of the threat of tropical cyclone winds, including its associated hazards and/or impacts on land areas.
The currently applied protocol by the country's Department of Education (DepEd) indicates that classes (from kindergarten to Grade 12) and work are automatically suspended in all public elementary and secondary schools located in localities where the TCWS system (regardless of the warning level) is in effect due to a tropical cyclone.
[18] The earliest issuance of a tropical cyclone warning in the Philippines happened on July 7, 1879, during the Spanish colonization era, when Federico Faura of the Observatorio Meteorológico del Ateneo Municipal de Manila (now known as the Manila Observatory) warned of a typhoon moving across Northern Luzon based on barometric readings.
[5] The primitive methods of meteorological observation and the lack of telegraph communications made it hard for the Observatorio, a Jesuit scientific institution established in 1865, to warn areas outside Manila promptly.
In 1884, the institution was formalized by royal decree as the Observatorio Meteorológico de Manila, leading to major improvements in their tropical cyclone monitoring and warning.
[3][2][1] PAGASA later expanded this to include details on the impacts of such wind intensities (particularly the potential scale of damage to agriculture and infrastructure) and the precautionary measures to be taken.
This four-tiered Public Storm Warning Signal system was in place for nearly two decades until amendments were made in 2015, two years after the disaster brought by Typhoon Haiyan.
[7][8] Alongside the TCWS, PAGASA also declared its official tropical cyclone intensity scale, which resembles the intensity scale stipulated in the ESCAP/WMO Typhoon Committee's operational manual[13] (implemented by the Japan Meteorological Agency (JMA), which is the WMO Regional Specialized Meteorological Center in charge of the Northwest Pacific basin).
[10][11][9] In a press release, PAGASA stated that the intensity scale and TCWS revisions are based on the "adoption of best practices from other TC warning centers and regionally-accepted operational standards, developments in objective guidance for TC wind swaths, operational experiences and challenges encountered by typhoon forecasters, and feedback from end-users and stakeholders.
