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Understanding the Habagat season – and preparing for it!

Jam Salazar | Sept. 13, 2017

With the recent weather systems passing by the Philippine Area of Responsibility (PAR), such as Typhoon Lannie and Tropical Storm Maring, we are yet again susceptible to different hazards brought by torrential rains and possible flooding.

If there is one key aside from disaster preparedness, it is understanding the dynamics of how these weather systems form and dissipate. This is the Habagat season, and WeatherPhilippines is here to walk you through it.

The Southwest Monsoon Wind

There are factors to consider when we talk about Monsoons. These are major wind systems that seasonally reverse its orientation of wind caused by difference between annual temperature trends over land and oceans. It blows from colder regions of High Pressure Area (HPA) toward warmer regions of Low Pressure Area (LPA). Monsoons are associated with the annual shift of wind patterns throughout the globe. It changes gradually, according to the order of seasons. Called monsoon systems, they have an impact on a regional scale in terms of rainfall distribution, amount of moist and warm air that feed into developing Tropical Cyclones, which we normally refer to as ’Bagyo’’ in the Philippines. In concept, these monsoon clouds travel from vast oceans where the sea surface temperature (SST) is warmer and moister.

Why does the Southwest Monsoon, locally known as Habagat, bring on-and-off moderate to heavy rains in a particular time and place? As they move from one place to another, they gather energy from the sea, where build up of clouds is certain to transport precipitation as opposed to a developing Low Pressure Area (LPA) to the East of the Philippines. (See Fig-1)

On the other hand, an LPA is characterized by rising of warm air. It becomes lighter as it increases in height and cools to saturation point. As it does, the water vapor within condenses to form clouds while the air expands and converges into a central point towards the Low Pressure. One distinctive indicator is when the flow of air takes a counter-clockwise orientation.

Recent surface analysis around the region with two (2) distinct Tropical Cyclones inducing the Southwest Monsoon (Habagat).
Recent surface analysis around the region with two (2) distinct Tropical Cyclones inducing the Southwest Monsoon (Habagat).

The Habagat wind prevails during June through September, and during this time, the migration of the Intertropical Convergence Zone (ITCZ) is parallel to the East of Visayas, thus the formation of LPAs in the process. In many instances, these monsoon clouds bring torrential rains crucial to agriculture and providing stability in temperature right after the hot dry months of March through early May of every year. The Philippine shores are just secondary recipient of the Southwest Monsoon. It emanates mainly from the South Indian Ocean and the Australian Continent, pushed by High Pressure Areas (HPAs) upwards crossing the Equator and is received by LPAs developing just above it. When this happens, a sustained inflow of moistures comes to play, thus the flooding rains that usually swamp the Western sections of the country.

Preparedness and Survival Tips

Just this week, a lot of photos and stories of people stranded due to flooding circulated around social media platforms. If you were in their situation, how would you have handled it? Here are some helpful ways to avoiding casualties during typhoon-related disasters:

  1. Emergency kits. Always make sure that your house has survival items stored and easily accessible when your family needs it. Generally, it should contain items such as a first aid kit, flashlight, batteries/power banks, drinking water, empty containers for water storage, infant needs (if you have a small child), sanitary supplies, and instant meals enough to last up to three days.
  2. Calamity plan. Create a general plan of what to do in case a calamity strikes and brief your family about it. Inform them about places to go and items to bring with you in case you need to evacuate immediately.
  3. Secure important documents. Keep all your important documents in one secure place or container that cannot be penetrated by water. Make sure that you can easily grab and bring it during times of disaster.
  4. Know your emergency numbers. Be knowledgeable of whom to contact during disasters. Keep a laminated list of these numbers and provide a copy to each family member.
  5. Track hazard warnings. Determine what levels of typhoon warnings or rain alerts are hoisted in your area. Downloading a weather mobile application that provides accurate and localized weather information is a great way to stay ahead of the weather.

While it is nearly impossible to predict other weather systems such as thunderstorms, staying weather-updated during the Habagat season will help you and your family anticipate and prepare for possible impacts of developing severe weather systems.