Meteorology covers a wide variety of terminology that we often hear, but seldom understand and remember. Check out these weather words and be in the know!
Climate is the general weather pattern in a specific area that involves temperature, humidity, rainfall, air pressure and other meteorological variables over a long period of time. According to the National Aeronautics and Space Administration (NASA), some scientists define climate as the average weather condition based on 30 years of observation.
It is important to study climate as it plays a big role in our lives. Rising global temperatures can cause sea levels to rise or affect precipitation over a specific region, human health and various ecosystems. Climate change is one of our generation’s major concerns.
Season refers to the time of the year caused by the tilting of the Earth. The Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) says it is the division of the year based on the recurring astronomical or climatic phenomenon.
However, the location of an area, whether it is in the northern or southern hemisphere, affects its seasons. Other regions have complete seasons: winter, spring, summer and fall. Philippines, being a tropical country, has two official seasons – wet and dry. The wet season usually starts in June as the southwest monsoon or habagat prevails. Rainfall during this season is concentrated over the western sections of the country.
Meanwhile, dry season normally starts in March when warm and humid weather is experienced. Though the scorching heat is felt over all the country, PAGASA clarifies that the term “summer” is not applicable to the Philippines. Meteorologically, we only have the wet and dry seasons.
The convergence of winds coming from the northern and southern hemispheres results to group of convective clouds known as the ITCZ or Intertropical Convergence Zone. This weather system affects the country depending on the orientation of the sun or the season. Once it becomes active, it can be a breeding ground of weather disturbances or low pressure areas.
Aside from tropical cyclones, ITCZ is one of the weather systems that cause flooding and landslides because it triggers moderate to heavy precipitation over the affected areas.
PAR means Philippine Area of Responsibility, an area in the Northwest Pacific, where PAGASA monitors tropical cyclones that are expected to affect the country. Once a tropical cyclone enters PAR, it is automatically given a local name so Filipinos can easily remember it.
With a measurement of more than 4 million square kilometres, PAR covers the West Philippine Sea, Bashi Channel over the north, part of the Pacific Ocean in the east and Sulu and Celebes Seas in the south.
One must remember that the Philippine Area of Responsibility is different from the country itself. When we say a tropical cyclone is entering the PAR, it doesn’t mean that it will hit the Philippine landmass. It may still change its course or re-curve away from the country.
Filipinos often hear the southwest monsoon or habagat during the rainy season. Characterized by warm and moist air, it speeds up cloud formation, which dumps rains mostly over the western section of the country.
Once a habagat is enhanced by a tropical cyclone entering PAR, it can bring heavy downpour that may cause widespread flooding.
During the passage of “Ondoy” last 2009 and “Maring” in 2013, habagat brought enormous amounts to Luzon, which led to serious flooding.
After habagat comes the northeast monsoon or amihan, a wind system characterized by cold and dry air coming from Mainland China. It normally starts to prevail during mid-October just like this year, when its onset was officially declared by PAGASA on October 16, 2014.
Amihan is responsible for colder mornings and lower temperatures during the “ber” months. It also affects sea conditions and may direct tropical cyclones towards the Philippine landmass with a higher chance of landfall.
PAGASA issues thunderstorm warnings everyday mostly in the afternoon or evening. A thunderstorm is a weather disturbance that produces rains, gusty winds, lightning and thunder.
Thunderstorm formation occurs through water cycle, wherein heat serves as the main component. As the sun heats up the land or a body of water, warm air rises, producing clouds by means of condensation. Once the cloud becomes massive, precipitation follows in the form of rain, drizzle or hail.
Along with gusty winds and moderate to heavy rains, thunder and lightning also occur during a thunderstorm. Lightning is caused by the connection of the positive charges at the top of the cloud and the negative charges formed at the bottom. Due to lightning, thunder is produced by vibration of air particles.
Flooding in low lying areas is expected during thunderstorms.
8. TROPICAL CYCLONE
Tropical cyclone is the general term for a “bagyo,” which starts out from a cloud cluster that develops into a low pressure area (LPA), an area that has an atmospheric pressure lower than its surrounding locations.
A tropical cyclone is classified into three: Tropical Depression, Tropical Storm and Typhoon. Each of these is measured by its maximum wind speeds and not by its amount of rainfall. An average of 19 to 21 tropical cyclones enter PAR each year.
Landfall happens when the surface of a tropical cyclone intersects with a coastline. In this scenario, the landmass or the affected area will experience stormy weather with moderate to heavy rains and gusty winds. According to the National Oceanic and Atmospheric Administration (NOAA), it is possible for a cyclone’s strongest winds to be experienced over land even if landfall does not occur. In some instances, its strongest winds could also remain over the water even if it made its landfall.
Tropical cyclones can have a series of landfalls like what happened to Typhoon Yolanda wherein 6 landfall activities were recorded on the 8th of November 2013.
10. STORM SURGE
Storm surge is the abnormal rise in sea level associated with a tropical storm or typhoon. It is usually measured by deducting the normal high tide from the observed storm tide.
This event is never related to tsunami, which is a sea level rise brought by a strong earthquake. A tsunami is triggered by underwater seismic activities while a storm surge is generated by strong winds from a storm.
Sources: PAGASA-DOST, NOAA, NASA