On May 4, 2008, an area of low pressure formed in the Pacific Ocean to the southeast of Yap.
The next day, the Joint Typhoon Warning Center (JTWC) upgraded the area of low pressure to a tropical disturbance and assessed the disturbances chances of forming into a significant tropical cyclone within 24 hours as poor.
This was because the developing low level circulation center was weak.
Early on May 6, the JTWC upgraded the disturbances chances of forming into a tropical cyclone within 24 hours to "fair", as the low level circulation center had consolidated further.
A Tropical Cyclone Formation Alert was then issued later that day, by the JTWC who upgraded the disturbance's chances of becoming a tropical cyclone by the next day as good.

Early the next day both the Japan Meteorological Agency (JMA) and the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) designated the tropical disturbance as a tropical depression with PAGASA assigning the local name of Butchoy to the depression.
 At this time the depression was located 790 km, (490 miles), to the east of Mindanao in the Philippines.
Later that morning the JMA started to issue full advisories on the tropical depression as forecasts showed that the depression could become a tropical storm within 24 hours.
The JTWC then designated the depression as Tropical Depression 02W. Later that day both the JTWC and the JMA reported that the depression intensified into a tropical storm, with the JMA assigning the name Rammasun to the storm.

Rammasun continued to intensify and was designated as a severe tropical storm late on May 8.
The next day both the JMA and the JTWC reported that Rammasun had intensified into a typhoon.
Later that day the JTWC reported that the typhoon had rapidly intensified within the last six hours and had become a Category 3 typhoon on the Saffir–Simpson hurricane wind scale.
At the same time the JMA were reporting that Rammasun had winds of 150 km/h (90 mph).
The typhoon then continued to intensify quickly with the JMA reporting that Rammasun had winds of 160 km/h (100 mph), the JTWC then reported that Rammasun had become a Category 4 typhoon with winds of 225 km/h (140 mph).
Later that day both the JMA and the JTWC reported that the typhoon had reached its peak winds.
The JMA reported peak winds of 195 km/h (120 mph) whilst the JTWC reported that Rammasun had peak winds of 250 km/h (155 mph), making it a category 4 super typhoon.
Typhoon Rammasun's minimum pressure was officially estimated at 915 hPa which tied with Intense Tropical Cyclone Hondo as second strongest storm of 2008.

The JTWC kept Rammasun as a super typhoon until early on May 11, when they reported that the typhoon had weakened into a category four typhoon, while the JMA were reporting that the typhoon had wind speeds of 175 km/h (110 mph).
Later that day both agencies reported that the typhoon had weakened even further, with the JMA reporting that Rammasun had winds of 160 km/h (100 mph), while the JTWC reported that Rammasun had weakened into a Category 3 typhoon.
The JTWC then reported within their next advisory that Rammasun had weakened into a Category 2 typhoon whilst the JMA reported that the typhoon had winds of 140 km/h (90 mph).
The next day as the Typhoon moved out of PAGASA's area of responsibility Rammasun was downgraded to a Category 1 typhoon by the JTWC.
Later that day the JMA downgraded Rammasun to a Severe Tropical Storm whilst the JTWC downgraded it to an extratropical cyclone and released their final advisory on the system.
The JMA continued to issue advisories on severe tropical storm Rammasun until early the next day when they downgraded it to an extratropical low.
On May 4, 2008, an area of low pressure formed in the Pacific Ocean to the southeast of Yap. The next day, the Joint Typhoon Warning Center (JTWC) upgraded the area of low pressure to a tropical disturbance and assessed the disturbances chances of forming into a significant tropical cyclone within 24 hours as poor. This was because the developing low level circulation center was weak. Early on May 6, the JTWC upgraded the disturbances chances of forming into a tropical cyclone within 24 hours to "fair", as the low level circulation center had consolidated further. A Tropical Cyclone Formation Alert was then issued later that day, by the JTWC who upgraded the disturbance's chances of becoming a tropical cyclone by the next day as good.
Early the next day both the Japan Meteorological Agency (JMA) and the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) designated the tropical disturbance as a tropical depression with PAGASA assigning the local name of Butchoy to the depression.  At this time the depression was located 790 km, (490 miles), to the east of Mindanao in the Philippines. Later that morning the JMA started to issue full advisories on the tropical depression as forecasts showed that the depression could become a tropical storm within 24 hours. The JTWC then designated the depression as Tropical Depression 02W. Later that day both the JTWC and the JMA reported that the depression intensified into a tropical storm, with the JMA assigning the name Rammasun to the storm.
Rammasun continued to intensify and was designated as a severe tropical storm late on May 8. The next day both the JMA and the JTWC reported that Rammasun had intensified into a typhoon. Later that day the JTWC reported that the typhoon had rapidly intensified within the last six hours and had become a Category 3 typhoon on the Saffir–Simpson hurricane wind scale. At the same time the JMA were reporting that Rammasun had winds of 150 km/h (90 mph). The typhoon then continued to intensify quickly with the JMA reporting that Rammasun had winds of 160 km/h (100 mph), the JTWC then reported that Rammasun had become a Category 4 typhoon with winds of 225 km/h (140 mph). Later that day both the JMA and the JTWC reported that the typhoon had reached its peak winds. The JMA reported peak winds of 195 km/h (120 mph) whilst the JTWC reported that Rammasun had peak winds of 250 km/h (155 mph), making it a category 4 super typhoon. Typhoon Rammasun's minimum pressure was officially estimated at 915 hPa which tied with Intense Tropical Cyclone Hondo as second strongest storm of 2008.
The JTWC kept Rammasun as a super typhoon until early on May 11, when they reported that the typhoon had weakened into a category four typhoon, while the JMA were reporting that the typhoon had wind speeds of 175 km/h (110 mph). Later that day both agencies reported that the typhoon had weakened even further, with the JMA reporting that Rammasun had winds of 160 km/h (100 mph), while the JTWC reported that Rammasun had weakened into a Category 3 typhoon. The JTWC then reported within their next advisory that Rammasun had weakened into a Category 2 typhoon whilst the JMA reported that the typhoon had winds of 140 km/h (90 mph). The next day as the Typhoon moved out of PAGASA's area of responsibility Rammasun was downgraded to a Category 1 typhoon by the JTWC. Later that day the JMA downgraded Rammasun to a Severe Tropical Storm whilst the JTWC downgraded it to an extratropical cyclone and released their final advisory on the system. The JMA continued to issue advisories on severe tropical storm Rammasun until early the next day when they downgraded it to an extratropical low.
Typhoon Rammasun (2008)