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12 Must-Know Terms this Rainy Season

PAR? Lows? What are those? The wet season is upon us, and the first step to preparation is understanding important weather terms.
We may be used to the rainy season, but most of us are still unfamiliar with the weather jargon we hear on TV. To be in the know, here are 12 weather words to help you prepare for the coming rains.
1. Intertropical Convergence Zone (ITCZ)
When the northeastern and southeastern winds converge to form a chain of clouds, it is known as a weather system called the Intertropical Convergence Zone (ITCZ). The ITCZ becomes a breeding ground for Low Pressure Areas.
2. Low Pressure Area (LPA)
When the heat or pressure in the atmosphere is generally nearer to the ground, it creates a Low Pressure Area (LPA), which forms rain clouds. This is because the water from the surface evaporates faster into clouds. LPAs, or lows, are commonly formed within ITCZs and can possibly evolve into storms or typhoons.
3. Thunderstorm
Thunderstorms are formed by accumulated clouds building up from evaporated water through the water cycle. Thunderstorms are characterized by strong winds, thunder and lightning, as well as rain. Lightning happens when positive charges from accumulated clouds connect with negative charges in clouds and even objects on the surface of the earth. Thunder is followed by lightning because of the vibration of air in the atmosphere.
4. Philippine Area of Responsibility (PAR)
The Philippine Area of Responsibility, or PAR, is a 4 square-kilometer area that is bound by an imaginary line that surrounds the Philippines. The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) exercises its mandate within the PAR to ensure that the country’s weather is monitored, allowing it to broadcast warnings if necessary. Once storms or typhoons enter the PAR, they are given Filipino names that were prepared at the start of the year.
5. Flash Flood
This is a type of flood that is caused by heavy rainfall during a short period of time (less than 6 hours). Flash floods may be caused by overflowing bodies of water, such as rivers, and by clogged sewage systems in urban areas.
6. Storm Surge
This typically occurs when tropical storms or typhoons affect a body of water, causing higher water levels and erratic waves. Storm surges raise the water level higher than its peak during high tide. Because of the sudden rise in water level, storm surges tend to breach towards land and cause major flooding. This is not to be confused with tsunamis, which are associated with waves caused by underwater seismic activity.

7. Tropical Cyclone Warning Signal (TCWS)
These are warnings issued by PAGASA to inform the public of the current weather situation, and to prepare them for weather disturbances. Last May 2015, PAGASA revised the TCWS to include Super Typhoons, adding an additional warning, Signal number 5, to the current system. This was revised because of the frequency of typhoons with winds 220 kph hitting the country – the last one being Typhoon Yolanda. These warning systems are classified according to wind speeds, not on the amount of rainfall.

8. Tropical Depression

This is characterized by wind speeds at 30 to 60 kph, with light or no damage to high-risk structures. This is classified as Signal No. 1 under the TCWS. PAGASA releases this warning with a lead time of 36 hours.
9. Tropical Storm
This type of weather has wind speeds between 61 to 120 kph, with light to moderate damage for high- and medium-risk structures. Coconut trees start to tilt at this point. PAGASA classifies this as Signal No. 2 and gives a lead time of 24 hours upon issuance.
10. Severe Tropical Storm
A tropical storm elevates to a severe tropical storm when winds go up to 121 to 170 kph, with possible storm surges happening in areas that are near bodies of water. This may cause heavy damage to structures and knock down small trees. PAGASA issues Signal No. 3 when this happens, with a lead time of 18 hours.
11. Typhoon
Wind speeds reach 171 up to 220 kph during a typhoon, with a high chance of storm surges happening in coastal areas. High to medium risk structures are prone to very heavy to heavy damages. Billboards and poorly-constructed roofs are blown down. PAGASA considers this as Signal No. 4, with a lead time of 12 hours once the agency issues it.
12. Super Typhoon
This is the most extreme type of weather disturbance classified under the TCWS, falling under Signal No. 5. Super Typhoons have winds of more than 220 kph, creating extensive infrastructure damage and uprooting trees completely. It is expected to make landfall within 12 hours after PAGASA issues this warning.
It’s important to know these terms so we can better prepare ourselves and our loved ones for rains and floods. Now that you know more about the weather, make sure to share your knowledge with others!