From tropical depression to super typhoon: How PAGASA classifies tropical cyclones

Published February 20, 2021, 12:45 PM

by Jhon Aldrin Casinas

Due to its geographical location, the Philippines is prone to tropical cyclones which generally generate heavy rains and strong winds, and cause flooding on low-lying and flood prone areas in the country.

(Pexels)

As rainy season starts by June, people would often hear in the news words such as tropical depression, tropical storm, typhoon, and even super typhoon.

But, what is the difference? The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) gives us the following definitions: 

Tropical Depression (TD) – a tropical cyclone with maximum sustained winds of up to 61 kilometers per hour (kph) or less than 33 nautical miles per hour (knots).

Tropical Storm (TS) – a tropical cyclone with maximum wind speed of 62 to 88 kph or 34 to 47 knots.

Severe Tropical Storm (STS) – a tropical cyclone with maximum wind speed of 89 to 117 kph or 48 to 63 knots.

Typhoon (TY) – a tropical cyclone with maximum wind speed of 118 to 220 kph or 64 to 120 knots.

Super Typhoon (STY) – a tropical cyclone with maximum wind speed exceeding 220 kph or more than 120 knots.

As a tropical cyclone moves closer towards the country’s landmass, tropical cyclone wind signals would be raised in areas estimated to be affected by the weather disturbance.

Signal No. 1

Winds of 30 to 60 kph or intermittent rains may be expected in at least 36 hours from the time the tropical cyclone warning has been raised. Areas along the cyclone’s path may incur no to very light damage. Waves of 1.25 to 4.0 meters (m) in height may occur in open seas.

Signal No. 2

Winds of 61 to 120 kph may be expected in the next 24 hours. Structures may sustain light to moderate damage. Waves of 4.1 to 14 m in height may occur in open seas. A storm surge is possible at coastal areas.

Signal No. 3

Winds of 121 to 170 kph may be expected in the next 18 hours. Waves of about 14 m may be observed. Storm surge is possible at coastal areas. Structures along the cyclone’s path may suffer heavy damages.

Signal No. 4

Winds of 171 to 220 kph may be expected in at least 12 hours. Waves of more than 14 meters in height may occur. Storm surge of 2 to 3 m is possible at coastal areas. Very heavy damage on structures is expected.

Signal No. 5

Winds of more than 220 kph may be expected in the next 12 hours. A cyclone equivalent to a super typhoon will affect the locality. Waves of more than 14 m in height may occur, while storm surge of more than 3 m is possible at coastal areas. Structures in its path would sustain widespread damages.

PAGASA said an average of 20 tropical cyclones enter the country every year.

Of the number, about eight or nine of these cyclones cross the country’s landmass. 

 
CLICK HERE TO SIGN-UP
 

YOU MAY ALSO LIKE

["national","news","news"]
[2627000,2632347,2632333,2632321,2632329,2632323,2632314]