Typhoon Rammasun, known in the Philippines as Typhoon Butchoy, was recognized as the second typhoon of the 2008 Pacific typhoon season by the Japan Meteorological Agency (JMA) and the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA). Rammasun was also recognised as the third tropical storm, the second typhoon and the first super typhoon of the 2008 Pacific typhoon season by the Joint Typhoon Warning Center (JTWC).

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Typhoon Rammasun (Butchoy)

Typhoon Rammasun shortly after peak intensity on May 11
Meteorological history
Formed	May 7, 2008
Extratropical	May 13, 2008
Dissipated	May 14, 2008
Violent typhoon
10-minute sustained (JMA)
Highest winds	195 km/h (120 mph)
Lowest pressure	915 hPa (mbar); 27.02 inHg
Category 4-equivalent super typhoon
1-minute sustained (SSHWS/JTWC)
Highest winds	250 km/h (155 mph)
Lowest pressure	922 hPa (mbar); 27.23 inHg
Overall effects
Fatalities	4 direct
Injuries	40
Damage	$9.6 million (2008 USD)
Areas affected	Philippines, Japan
IBTrACS
Part of the 2008 Pacific typhoon season

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Rammasun formed on May 5 as a tropical disturbance. The next day the Joint Typhoon Warning Center issued a tropical cyclone formation alert on the developing disturbance. On May 7 both the JTWC and the Japan Meteorological Agency designated the disturbance as a tropical depression, while PAGASA named the depression Butchoy. Later that day both the JMA and the JTWC upgraded the depression to a tropical storm with the JMA naming the storm Rammasun. On May 9 both the JTWC and the JMA upgraded Rammasun to a typhoon. The next day the JMA and the JTWC reported that Rammasun had reached its peak winds of 195 and 250 km/h (121 and 155 mph) respectively, which made Rammasun a Category 4 super typhoon on the Saffir-Simpson Hurricane Scale. After reaching its peak intensity, Rammasun weakened and was downgraded to severe tropical storm on May 12, before the JTWC declared it extratropical and issued their final advisory. The JMA did not issue their final advisory until several hours later. Within Japan an estimated 10 hectares (25 acres) of farmland were damaged. In all, the typhoon killed four people, injured 40 others and caused $9.6 million (2008 USD) worth of damage in both the Philippines and Japan.

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.^[1] This was because the developing low level circulation center was weak.^[1] 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.^[2] 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.^[3]

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.^[4][5] At this time the depression was located 790 km (490 mi), to the east of Mindanao in the Philippines.^[5] 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.^[6] The JTWC then designated the depression as Tropical Depression 02W.^[7] 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.^[8][9]

Rammasun continued to intensify and was designated as a severe tropical storm late on May 8.^[10] The next day both the JMA and the JTWC reported that Rammasun had intensified into a typhoon.^[11][12] 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.^[13] At the same time the JMA were reporting that Rammasun had winds of 150 km/h (93 mph).^[14] The typhoon then continued to intensify quickly with the JMA reporting that Rammasun had winds of 160 km/h (99 mph), the JTWC then reported that Rammasun had become a Category 4 typhoon with winds of 225 km/h (140 mph).^[15][16] 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 (121 mph) whilst the JTWC reported that Rammasun had peak winds of 250 km/h (160 mph), making it a category 4 super typhoon.^[17][18] Typhoon Rammasun's minimum pressure was officially estimated at 915 hPa which tied with Intense Tropical Cyclone Hondo as second strongest storm of 2008^[18][19]

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 (109 mph).^[20][21] 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 (99 mph), while the JTWC reported that Rammasun had weakened into a Category 3 typhoon.^[22][23] 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 (87 mph).^[24][25] 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.^[26][27] 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.^[28][29] The JMA continued to issue advisories on severe tropical storm Rammasun until early the next day when they downgraded it to an extratropical low.^[30]

The name "Rammasun" was one of the 10 original names submitted by Thailand to the ESCAP/WMO Typhoon Committee for use from January 1, 2000.^[31] Rammasun is the Thai god for thunder. The name was last used in the 2002 Pacific typhoon season,^[32] though it was retired in 2015 after Typhoon Rammasun (the same name used for the 2014 season, Typhoon Glenda in the Philippines) left considerable damages in the Philippines, China and Vietnam. The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) also assigned the local name of "Butchoy" to Rammasun;^[5] the name "Butchoy" was last used by PAGASA to name a tropical depression in the Philippines in 2004 to name Tropical Storm 02W.^[33]

Within the Philippines, PAGASA issued no public storm warning signals, as the storm was too far away from the country to prompt the issuance of such advisories. However, they did warn that the cyclone was expected to enhance the southwest monsoon and bring rain over Central and Southern Luzon, Visayas and Mindanao.^[5][26]

• Other tropical cyclones named Rammasun
• Other tropical cyclones named Butchoy
• Typhoons in the Philippines
• Timeline of the 2008 Pacific typhoon season