Storms in the Western Pacific Ocean

Typhoons, a type of tropical cyclones, are powerful storm systems that develop over warm ocean waters. In the Pacific Ocean, particularly the western Pacific, they play a critical role in shaping weather patterns and impacting human activities across numerous countries.

When is the Pacific typhoon season?

The Pacific typhoon season is active year-round, with peak activity from June to November. The months of August through October are particularly intense due to elevated sea surface temperatures. The western Pacific experiences around 25 to 30 tropical storms annually, with about half intensifying into typhoons.

An unusual November 2024 storm occurrence in the western Pacific Ocean

Early November 2024 saw the formation of four tropical storms at the same time in the western Pacific. NASA reported that around the time of that the satellite image was taken on November 11, 2024, these were the names and predicted conditions of the four storms:

Typhoon Toraji (Nika):

• Made landfall on northeastern Luzon, Philippines, about 40 minutes before the satellite image was acquired .
• Caused flooding, power outages in Aurora Province, and landslides in the Cordillera mountain range.
• Reached peak intensity the night before, with sustained winds of 130 km/h (80 mph), according to the Japan Meteorological Agency.

Typhoon Yinxing (Marce):

• Hit northern Luzon on November 7 with sustained winds of 240 km/h (150 mph), making it a super typhoon (Category 4 equivalent).
• Weakened before striking Vietnam and dissipated on November 12.

Typhoon Usagi (Ofel):

• Forecast to become the fifteenth tropical cyclone to impact the Philippines in 2024, following Toraji’s path.
• On November 11, it was a tropical storm but rapidly intensified into a super typhoon with winds of 240 km/h (150 mph) by November 13.
• Expected to make landfall on the Philippines later on November 13.

Tropical Storm Man-Yi:

• Forecast to intensify into a typhoon and make landfall in the Philippines on November 17.
• At the time of the image, had sustained winds of 85 km/h (50 mph).

According to the Japan Meteorological Agency, this is the first time that four named storms have been active in the western Pacific Ocean since record keeping began in 1951. The Philippines endured severe typhoon impacts in 2024, with Tropical Storm Trami and Typhoon Kong-Rey causing deadly flooding and landslides in Luzon in October.

How do typhoons form?

Typhoons originate from tropical disturbances, which are areas of organized thunderstorms over warm ocean waters. Several key conditions are essential for their development:

• Warm sea surface temperatures: Typically above 26.5°C (79.7°F), providing the necessary heat and moisture.
• Atmospheric instability: Allows warm, moist air to rise, leading to cloud formation and storm development.
• High humidity: In the lower to middle levels of the troposphere, sustaining the storm’s energy.
• Coriolis effect: The deflection of moving air due to Earth’s rotation, which helps in the development of the storm’s rotation.
• Low vertical wind shear: Ensures the storm’s structure remains intact, allowing it to strengthen.

These conditions are most prevalent in the western Pacific Ocean, making it the most active tropical cyclone basin globally.

How are typhoons classified?

Typhoons are categorized based on sustained wind speeds:

• Tropical depression: Winds up to 61 km/h (38 mph).
• Tropical storm: Winds between 62 km/h (39 mph) and 88 km/h (54 mph).
• Severe tropical storm: Winds between 89 km/h (55 mph) and 117 km/h (73 mph).
• Typhoon: Winds of 118 km/h (74 mph) or higher.
• Super typhoon: Winds exceeding 240 km/h (150 mph).

The Japan Meteorological Agency (JMA) and the Joint Typhoon Warning Center (JTWC) are the primary agencies responsible for monitoring and classifying typhoons in the Pacific.

What are the impacts of typhoons?

Typhoons significantly affect countries along the Pacific Rim, including the Philippines, Japan, China, Taiwan, Vietnam, and the Korean Peninsula. Key impacts include:

• Heavy rainfall and flooding: Leading to landslides and inundation of low-lying areas.
• Strong winds: Causing structural damage, uprooting trees, and disrupting power supplies.
• Storm surges: Elevated sea levels resulting in coastal flooding.

The Philippines, located in “typhoon alley,” faces approximately 20 typhoons annually, resulting in widespread socio-economic consequences.

Notable typhoons in history

Several typhoons have left a lasting impact due to their intensity and destruction:

• Typhoon Haiyan (Yolanda) 2013: One of the strongest tropical cyclones ever recorded, causing over 6,300 fatalities in the Philippines.
• Typhoon Tip 1979: The largest and most intense typhoon on record, with a diameter of over 2,200 km (1,380 miles) and peak winds of 305 km/h (190 mph).
• Typhoon Yagi 2024: A recent super typhoon with peak winds of 240 km/h (150 mph), causing significant damage in the Philippines and southern China.

How is climate change influencing typhoons?

Research suggests that climate change is altering typhoon behavior in several ways:

• Stronger storms: Warmer sea surface temperatures contribute to more powerful typhoons.
• Heavier rainfall: Increased atmospheric moisture results in more intense precipitation.
• Shifting paths: Changes in atmospheric circulation may alter typical typhoon tracks.

A 2024 study emphasized the growing variability in rainfall and intensification of typhoons, increasing their potential for severe impacts.

Reference

Zhang, W., Zhou, T., & Wu, P. (2024). Anthropogenic amplification of precipitation variability over the past century. Science, 385(6707), 427-432. DOI: 10.1126/science.adp021

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