Tropical depressions, or *áp thấp nhiệt đới* in Vietnamese, are a vital part of the tropical weather system. Understanding these weather phenomena is crucial, especially for regions prone to their formation and impact, such as Southeast Asia. A tropical depression is essentially the first stage in the lifecycle of a tropical cyclone, which can eventually develop into a tropical storm or even a typhoon/hurricane. They are characterized by organized systems of thunderstorms with a defined surface circulation and maximum sustained winds of less than 39 miles per hour (63 kilometers per hour). This wind speed threshold distinguishes them from stronger tropical systems. Formation typically occurs over warm ocean waters, at least 26.5 degrees Celsius (80 degrees Fahrenheit), providing the necessary heat and moisture to fuel the developing storm. Convergence of air near the surface, often influenced by pre-existing weather disturbances like troughs or fronts, initiates the spin. This spin is further intensified by the Coriolis effect, a force caused by the Earth’s rotation. The Coriolis effect is minimal near the equator, which is why tropical cyclones rarely form within a few degrees of the equator. As warm, moist air rises, it cools and condenses, releasing latent heat. This latent heat further warms the surrounding air, causing it to rise even faster and create a self-reinforcing process. This process leads to the development of thunderstorms and the intensification of the low-pressure center. While tropical depressions are the weakest form of tropical cyclone, they should not be underestimated. They can bring significant amounts of rainfall, leading to flash floods and landslides, particularly in mountainous regions. The heavy rainfall can also inundate low-lying coastal areas and cause significant damage to infrastructure. The associated winds, although not as destructive as those in stronger storms, can still cause damage to weak structures and uproot trees. Moreover, the rough seas generated by a tropical depression can pose a significant hazard to maritime activities. Monitoring and forecasting tropical depressions are critical for issuing timely warnings and preparing communities for potential impacts. Meteorological agencies use a variety of tools, including satellites, weather radar, and surface observations, to track the development and movement of these systems. Numerical weather prediction models are also employed to forecast the storm’s track, intensity, and potential rainfall. In Vietnam, the National Center for Hydro-Meteorological Forecasting plays a crucial role in monitoring and predicting *áp thấp nhiệt đới*. They issue warnings and advisories to the public and relevant authorities, allowing them to take necessary precautions to mitigate potential damage. These precautions might include evacuating residents from vulnerable areas, reinforcing infrastructure, and preparing emergency response teams. The intensity and impacts of a tropical depression can be significantly influenced by various factors, including the sea surface temperature, atmospheric conditions, and interaction with landmasses. Landfall, in particular, can weaken a tropical depression by cutting off its supply of warm, moist air and increasing friction. However, even after weakening, the remnants of a tropical depression can still produce significant rainfall and flooding. Therefore, understanding the characteristics, formation, and potential impacts of tropical depressions is essential for effective disaster preparedness and risk reduction in vulnerable regions. Constant monitoring, accurate forecasting, and timely warnings are crucial for minimizing the devastating effects of these seemingly less powerful, but still potentially dangerous, weather systems.