Typhoon Rammasun, known in the Philippines as Typhoon Glenda, was a powerful typhoon that is one of the only four Category 5 super typhoons on record in the South China Sea, with the other ones being Pamela in 1954, Rai in 2021 and Yagi in 2024. Rammasun had destructive impacts across the Philippines, South China, and Vietnam in mid July 2014. It was the strongest typhoon to hit the Chinese province of Hainan since Damrey in 2005. Rammasun is a Thai word for thunder god. After Lingling and Kajiki earlier in 2014, Rammasun became the third tropical cyclone, and first typhoon to directly impact the Philippines in 2014. The ninth named storm and the third typhoon of the annual typhoon season, Rammasun formed in the Intertropical Convergence Zone, an area near the equator where the northeast and southeast trade winds come together, and slowly drifted northwest. Having passed through the islands of Micronesia, the system turned west and quickly moved under the influence of a subtropical ridge (STR). Rammasun posed a significant threat to Luzon, as it was expected to reach typhoon intensity before making landfall there. Though initially forecast to make landfall in Cagayan Valley, the storm followed a more westerly path and was later forecast to make landfall in Rapu-Rapu, Albay in Bicol Region and then pass through Bataan and Zambales before brushing past Metro Manila.

In preparation for the storm, Governor of Guam Eddie Calvo declared the island in Condition of Readiness 3 and later upgraded it to Condition of Readiness 1. On July 11, NASA satellites revealed Rammasun passing directly over Guam. The American National Weather Service stated that an unexpected rise in wind shear kept the system from intensifying much further before reaching Guam. Rammasun only made landfall on Guam as a tropical depression, with winds much weaker than earlier anticipated. However, under the system, the island received a substantial amount of rainfall, making that day the wettest in around 3 months. The United States territory received 25 to 50 mm (0.98 to 1.97 in) of rain. Along with the Philippines, Taiwan also expected impact from Rammasun. Moderate to heavy rainfall was predicted through most of the country. Chinese meteorologists were focusing on second and/or third landfalls in the Chinese Hainan province and northern Vietnam. Residents of Hong Kong were also warned of rainfall and subsequent landslides.

Following the closure of maritime seaports, more than 100 passengers were reportedly stranded at the Port of Batangas, along with 39 rolling cargoes. Meanwhile, at least 841 passengers were stranded in five ports in the Bicol region, namely Matnog, Tabaco, Bulan, Cataingan and Pilar. A total 50 flights were cancelled and over 100 thousand families were evacuated as the typhoon neared landfall. The Philippine Department of Health said that they have prepared all government hospitals to aid the rescue and relief process during and after the typhoon. They claimed that they are much better prepared now, than they were for earlier typhoons. Ahead of the landfall, a city in the province of Albay had declared a state of calamity. At around 17:00 Philippine Standard Time (09:00 UTC), Rammasun's eye passed directly over Rapu-Rapu, Albay while the storm was at its initial peak intensity. Various parts of the National Capital Region reported power outages during the storm. They were reportedly caused by "a temporary system balance at 1:29 a.m. due to a sudden plant outage." Laguna is one of the badly hit by the typhoon At least 6,000 people were stranded at various seaports throughout the country due to the storm.

On July 9, the United States Joint Typhoon Warning Center (JTWC) started to monitor a tropical disturbance, that had developed to the east of the Micronesian State of Chuuk. At this time the system had a broad and ill-defined circulation center which was associated with flaring and disorganized atmospheric convection. Over the next day the system gradually consolidated within an area of favorable conditions, with convection wrapping around the systems obscured low level circulation center. The system was subsequently declared a tropical depression during the next day, by both the Japan Meteorological Agency (JMA) and the JTWC with the latter assigning it the designation 09W.

Early on July 11, the JTWC reported that the system had intensified into a tropical storm, after they had assessed the intensity slightly higher than the Dvorak estimates from various agencies. Later that day as the system approached Guam, the JTWC reported that the system had not intensified into a tropical storm and downgraded it to a tropical depression. This was because of the lack of supporting Dvorak estimates from various agencies and various observations from Guam, that showed the system was a poorly defined low level circulation center with deep convection sheared to the northwest of the center. Early on July 12, the JMA reported that the depression had become a tropical storm and named it Rammasun, as the system passed through the Rota Channel to the north of Guam. Later that day as Rammasun moved westwards under the influence of the subtropical ridge of high pressure, the JTWC reported that it had regained tropical storm status after Dvorak estimates from various agencies supported it and the low level structure of the system had improved.

Rammasun entered the Philippine area of responsibility and was given a local name, Glenda on July 13. The storm maintained intensity while a burst of deep central convection developed and the LLCC became slightly more well defined. Over the next couple of hours, vertical wind shear decreased gradually. Rammasun tracked in a westerly direction along the periphery of the steering subtropical ridge. Outflow improved along the southwestern quadrant and Rammasun became a typhoon. The LLCC consolidated while convective banding became well defined and tightly wrapped. During July 14, both the JTWC and the JMA upgraded Rammassun to a typhoon after Dvorak estimates from various agencies suggested maximum sustained winds of 65 knots (120 km/h; 75 mph).

Shortly before its Philippine landfall, Rammasun developed a 10 nautical miles (19 km; 12 mi) wide eye. The storm had vigorous equatorward and westward outflow. At that time, the storm was peaking at 80 knots (150 km/h; 92 mph) 1-minute sustained winds and 75 knots (139 km/h; 86 mph) 10-minute sustained winds. Though initially expect to maintain that intensity and make landfall before weakening into a tropical storm again due to land interaction, Rammasun further intensified. Some six hours later, the JTWC spotted a 20 nautical miles (37 km; 23 mi) eye, twice as wide as previously reported. The 1-minute sustained winds were set at 100 knots (190 km/h; 120 mph), equivalent to Category 3 of the Saffir-Simpson Hurricane Wind Scale (SSHWS). Rammasun continued to strengthen, despite land interaction. Post landfall, the storm's windspeed continued to rise, as it was located in a very favorable environment. JTWC initially reported winds of 110 knots (205 km/h; 125 mph) 1-minute sustained winds before correcting it to 115 knots (215 km/h; 130 mph) in their best track, making it a Category 4-equivalent typhoon.

By 00:00 UTC on July 16, Rammasun's eye had re-emerged into the South China Sea. The typhoon lost its eye feature due to its interaction with Philippine's rugged terrain. The convective structure had slightly degraded. However, convective banding remained tightly wrapped around the LLCC.