CEBU CITY -- Around 19 to 20 tropical cyclones enter the Philippines' area of responsibility every year, said the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa).
To keep the public informed about the weather status of the country, Pagasa issues Tropical Cyclone Warning Signals (TCWS) and other warning advisories.
TCWS indicates the strength of a typhoon and the severity of its impact to the public, while rainfall and thunderstorm advisories are issued to alert the community with regards to rain measurement and flood possibility.
SunStar sat down with Pagasa-Visayas Chief Oscar Tabada to deeply understand the warning system of the weather bureau.
Here is a guide to Pagasa's Tropical Cyclone Warning System:
Pagasa classified tropical cyclones according to strength and grouped them according to the maximum sustained winds felt in areas near their center or eye.
TCWS Number 1 (Tropical Depression): From the first issuance of the first warning signal, affected areas should expect the storm bringing 30 to 60 kilometers per hour (kph) of wind within 36 hours.
Impacts of the wind may cause no significant damage to structures.
The public is advised to monitor the latest "Severe Weather Bulletin" issued by Pagasa every six hours.
TCWS Number 2 (Tropical Storm): Affected areas are advised to expect the storm packing 61 to 120 kph of wind within 24 hours, and storm surge is possible at coastal areas.
According to the National Oceanic and Atmospheric Administration, storm surge is an abnormal rise of water generated by a storm. It is produced by water being pushed toward the shore by the force of winds moving around the storm.
Pagasa said storm surge has the ability to destroy natural and man-made structures, thus residents in coastal areas are advised to evacuate and look for a higher ground.
"There is misconception, there is no storm surge that will develop if we have only a not so strong wind. For example in depression category, below 61 kph ang wind niya, dili gayud na ka generate og storm surge. (Winds below 61 kph will not generate storm surge)," Tabada said.
In this second warning, impacts of the wind may cause light to moderate damage to structures.
People traveling by sea and air are advised to cancel the trip if not necessary.
TCWS Number 3 (Severe Tropical Storm): Affected areas must expect a storm with 121 to 170 kph of wind within 18 hours. Storm surge is possible in this third warning signal.
The storm may cause moderate to heavy damage to structures.
People from low-lying areas are advised to evacuate to higher grounds.
TCWS Number 4 (Typhoon): In this warning signal, affected areas must expect a storm with 171 to 220 kph of wind within 12 hours. Storm surge of two to three meters is possible at coastal areas.
The storm may cause heavy to very heavy damage to structures.
The public is advised to stay in safe house and evacuation centers, while all travels and outdoor activities should be cancelled.
TCWS Number 5 (Super Typhoon): Signal Number 5 is the highest warning signal of Pagasa. In this warning signal, affected areas must expect a storm packing with more than 220 kph of wind within 12 hours.
Storm surge of more than three meters is possible within coastal areas.
The storm may cause very heavy to widespread damage. The public is advised to stay in safe houses or evacuation centers, while all travels and outdoor activities should be cancelled.
Rainfall warning
Aside from TCWS, the weather bureau issues rainfall warning classified into three different colors: Yellow, Orange, and Red.
Graphics courtesy of gov.ph and pagasa.dost.gov.ph.
Yellow warning: Heavy rain, equivalent to two gallons of water per square meter per hour, is observed in one hour and expected to continue in the next two hours.
The public is advised to monitor the weather condition as flooding is possible.
Orange warning: Intense rain, equivalent to four to eight gallons of water per square meter per hour, is observed in one hour and expected to continue in the next two hours.
The public is advised to be alert for possible evacuation, flooding is threatening in the affected areas.
Red warning: Torrential rain, equivalent to eight gallons of water per square meter per hour, is observed in one hour and expected to continue in the next two hours.
The public is advised to evacuate as serious flooding is expected in low-lying areas.
Thunderstorm warning
The weather bureau also issues thunderstorm warnings to the public.
Tabada said thunderstorm is a short localized weather disturbance that brings heavy rain that may cause flooding. It may affect areas within a radius of four kilometers for one to two hours.
"Thunderstorm actually ang occurrence ana mga one hour ra wagtang dayon na siya, but grabe ang downpour ana, mostly maka cause gayud na og flashflood. (Thunderstorm may occur only for one hour, but it brings heavy rain that may cause flashfloods)," said Tabada.
The Pagasa-Visayas chief said hazards such as tornado, water spout, lightning, and thunder may occur during thunderstorms.
Tabada urged the public to follow what the government says during disasters and calamities, emphasizing that nothing is more precious than a life of a person.
Pagasa's advisories may be accessed through their Facebook page, Twitter account, and website. (Sunnex)