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Global Guide to Tropical Cyclone Forecasting:
CHAPTER 7: WARNING STRATEGIES

7.6 WORKING WARNING AND RESPONSE STRATEGIES:
THE PHILIPPINES EXAMPLE

In terms of frequency, strength and hazardous terrain, allied to prevailing socio-economic conditions few countries exceed the vulnerability of the Philippines to the impact of tropical cyclones. The Philippines approach to a warning-response strategy is briefly outlined here as an example of the methods used by a vulnerable country with limited resources.

The Philippines is a nation of 70 million people spread over 7000 islands of which some 3000 are populated. Fourteen regions administered by commissioners are divided into hundreds of provinces administered by governors, which in turn are comprised of cities and municipalities with elected mayors. At the community level is about 45,000 locally autonomous Barangays, each covering 5 km², with around 1000 people and led by an elected Barangay captain. Each year warning and preparedness personnel are confronted with around 20 tropical cyclones, of which 8 or so make landfall on the islands. The Philippines area of warning responsibility extends from 5-24^oN and from 115-135^oE. Taking into account typical 24, 48 and 72 h mean forecast errors of about 200, 400 and 600 km, respectively, it is easily demonstrated that 72 h in advance the whole of the Philippines may be subject to threat of landfall, 48 h in advance most of the more vulnerable central and northern regions, and 24 h in advance several islands and communities. When additional margins are included for the peripheral effects of the disturbance and the potential for major forecast errors, much of the Philippines is under direct threat from all cyclones that occur in the region.

By Presidential Decree, the Philippines Government, through its civil defence administration, has established a national Calamities and Disaster Preparedness Plan, published by the OCD (1987), which is frequently updated. This plan provides a highly decentralised organisational and operational disaster preparedness structure, with uniform functional procedures that are implemented by disaster coordinating councils, each with their own emergency operations centres. This national organisation extends from a national headquarters in Manila, through regional, provincial and municipal councils and down to the Barangays. A municipality may be surrounded by some 20 Barangays. Due to the generally mountainous and irregular nature of the Philippines landscape and huge sea frontages even adjacent Barangays may possess distinctly different levels of vulnerability, thus each deserving its own hazard contingency plan. While progress has been made, the self-reliance ideal of having a local resource of trained, largely volunteer, staff at the Barangay level, responding to typhoon warnings in accord with documented and rehearsed local contingency plan is far from being achieved under current socio-economic circumstances.

The national weather service, PAGASA (Philippine Atmospheric, Geophysical and Astronomical Services Administration), has made excellent progress in promoting public understanding of its warning system through the conduct of community response surveys and hazard awareness and education programs. Particular emphasis has been placed on the role of the decentralised broadcast media, and press, in assisting warning objectives. One of PAGASA's guiding principles is that awareness programs must be community specific, hazard specific and audience specific in terms of potential disaster risk. This requires that the local warnings be similarly patterned and made entirely comprehensible to affected communities. In consultation with government and non-government bodies, aided by community testing, PAGASA has recently modified its national warning format, including redesigned public storm signals, which have been increased from 3 to 4. These progressive steps have been taken to counter recent trends of increasing losses of life and property damage due to typhoons in the Philippines. The aim is to impress on people the preparedness impact of the message, especially by providing people enough lead time and arousing their awareness according to the ascending order of the gravity of the threat.

The modified format comprises three stages of public warning notices; weather advisories, issued daily at 3 pm, for tropical storms outside or bordering the region of responsibility, severe weather bulletins for tropical cyclone Alerts, issued at 11 am and 11 pm for tropical cyclones within the region of responsibility, but not offering a threat within 36 h, and severe weather bulletins for tropical cyclone Warnings, issued at 5 am, 11 am, 5 pm and 11 pm for cyclones providing a threat within 36 h.

One, or more of 4 Public Storm Signals, accompanies the issue of each tropical cyclone warning. These are defined as:

No 1 - a tropical cyclone will affect the locality, with winds of less than 60 km h^-1 within 36 h;

No 2 - a tropical cyclone will affect the locality, with winds of 60-100 km h^-1 within 24 h;

No 3 - a tropical cyclone will affect the locality, with winds of 100-185 km h^-1 within 18 h;

No 4 - a very intense typhoon will affect the locality, with very strong winds in excess of 185 km h^-1 within 12 h.

The redesigned number system contains three categories of information:

• (a) the meteorological conditions expected to prevail within stated times limits;
  
  
• (b) the impact of the given range of winds speeds on common objects such as trees, crops and structures, to enable the people to perceive the likely effects in terms of their own experience; and
  
  
• (c) statements of the seriousness of the danger, containing desired precautionary measures by the public and recommendations for implementation by disaster agencies.
  

The full description for each signal, with qualifying notes, is appended for consideration of national weather services which either do not use such a system for the public, or currently rely on far more complex systems introduced for maritime purposes.

The storm signal system does not necessarily imply the physical hoisting of signals, but implies public announcement, generally by radio, of the relevant number. Blasts on warning sirens are used in populated areas. The writer's experience in conducting cyclone preparedness seminars in the Philippines is that the public quickly learns to differentiate between the relative threat implied by each signal through recognition of various preparedness measures, such as suspension of school classes. A typical PAGASA bulletin warning containing public storm signal announcements is:

Severe Weather Bulletin Number Twelve. Typhoon Warning (Trining) issued at 5 am today 27 October 1991 (Valid for broadcast until the next bulletin at 11 am today).

Typhoon Trining has slightly weakened and changed its course and is now heading towards Cagayan.

At 10 am today, 27 October 1991, the center of typhoon Trining was estimated based on satellite and surface data about 130 km east of Aparri, Cagayan, or at (18.4N 123.0E) with maximum sustained winds of 205 KPH near the center and gustiness up to 240 KPH. It was moving west at 19 KPH during the past six hours.

Trining is forecast to continue to move west northwest at 19 KPH and expected to landfall over Cagayan this afternoon, Its center is expected to be 280 km west northwest of Aparri, Cagayan or 180 km west northwest of Laoag City by 8 am tomorrow morning or at (19.0N 119.3E). Trining is expected to move west northwest starting tonight. It is likely to weaken within the next 12 hours.

Public Storm Warning Signal number Four is now in effect over Batanes Group, Northern Cagayan including Calayan and Babuyan Islands where stormy weather with winds in excess of 185 KPH will be experienced today. Coastal waters are extremely dangerous to all types of sea vessels.

Public Storm Warning Signal number Three remains in effect over the rest of Cacayan, Kalinga Apayao, Ilocos Norte, Isabella, Abra, Mt.Province and Ilocos Sur.

Public Storm Warning Signal number Two remains in effect for the rest of North Luzon.

Areas under Public Storm Warning Signal number Three and Two will have stormy weather today and seas will be very rough and dangerous to all seacrafts. Residents under signal number Four, Three and Two should take precautionary measures against strong winds and those living in coastal areas should be prepared against big waves coming from the sea.

Public Storm Warning Signal number One remains in effect over Metro Manila and the rest of Luzon. These areas will have occasional rains and occasional gusty winds today and coastal waters will be rough.

The public and the Disaster Coordination Councils concerned are advised to take appropriate action and watch for the next bulletin to be issued at 5pm today.

PAGASA utilises a standard documentary format and flow chart entitled "Typhoon Prediction and Warning Process" that sets out details of its analysis, diagnostic, forecasting and warning processes, and formats. This helps facilitate the rapid compilation of update bulletins for technical and public purposes. These include warnings and advisories for farmers and agricultural industries, and flood forecasting purposes.

Posters and leaflets explaining the enhanced amended public storm signal numbers were widely disseminated in the Philippines prior to their introduction at the end of the 1991 typhoon season. Considerable illustrated information relating to typhoons and other natural hazards is incorporated in school textbooks. For younger children a video using animated puppets depicting hazards such as typhoons, floods, earthquakes and volcanic eruptions is used in community hazard campaigns.

Contents Appendix: Ch7