The 2005 Pacific typhoon season was the least active typhoon season since 2000, producing 23 named storms, of which 13 became typhoons (including 3 super typhoons). It was an event in the annual cycle of tropical cyclone formation, in which tropical cyclones form in the western Pacific Ocean. The season ran throughout 2005, though most tropical cyclones typically develop between May and November. The season's first named storm, Kulap, developed on January 13, while the season's last named storm, Bolaven, dissipated on November 20. The season's first typhoon, Haitang, reached typhoon status on July 13, and became the first super typhoon of the year three days later.
The scope of this article is limited to the Pacific Ocean, to the north of the equator between 100°E and the 180th meridian. Within the northwestern Pacific Ocean, there are two separate agencies that assign names to tropical cyclones, which can often result in a cyclone having two names, one from the JMA and one from PAGASA. The Japan Meteorological Agency (JMA) will name a tropical cyclone should it be judged to have 10-minute sustained wind speeds of at least 65 km/h (40 mph) anywhere in the basin, while the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) assigns names to tropical cyclones which move into or form as a tropical depression in their area of responsibility located between 135°E and 115°E and between 5°N–25°N regardless of whether or not a tropical cyclone has already been given a name by the JMA. Tropical depressions that are monitored by the United States' Joint Typhoon Warning Center (JTWC) are given a number with a "W" suffix.
Seasonal forecasts
During the year several national meteorological services and scientific agencies forecast how many tropical cyclones, tropical storms, and typhoons will form during a season and/or how many tropical cyclones will affect a particular country. These agencies included the Tropical Storm Risk (TSR) Consortium of University College London, PAGASA and Taiwan's Central Weather Bureau. Some of the forecasts took into consideration what happened in previous seasons and the La Niña conditions that were observed during the previous year.
On March 14, TSR published their extended range forecast for the 2005 season, in which the anticipated that they would see tropical activity slightly below the average. They predicted that there would be a total of 25-26 tropical storms and 16 typhoons. The TSR, however, forecast that their number of intense typhoons would go slightly above the average, bringing their prediction of 10 intense typhoons. Their main reasons behind this is due to weaker trade force winds occurring in many parts of the basin, and there would be an enhanced cyclonic vorticity over the northwestern part of the Pacific. On April 27, the GCACIC made their first forecast for the season, expecting about 24 tropical storms developing, in which 15 of them would strengthen into typhoons. By May 5, TSR published their first forecast, still predicting a near average typhoon season. Around this time, 27-28 tropical storms, 17-18 typhoons and 9 intense typhoons were predicted, with the slight increase of the number of tropical storms were due to a slight increase in temperatures within the Niño 3.75 region.
TSR's second forecast was released on June 7, now predicting a slightly above average season, with the only change for their predicted cyclone numbers was a slight increase of intense typhoons to 9.4. The GCACIC made their second and final forecast for the season on June 24, slightly increasing their numbers to 25 tropical storms and 16 typhoons. The TSR maintained their predictions after their third forecast update on July 5. Sea-surface temperatures within the Pacific were predicted to be more warmer than that predicted back in the May forecast. On August 5, TSR released their fourth and final forecast for the season, still remaining the same numbers along with the same reasonings.
Seasonal summary
The Accumulated Cyclone Energy (ACE) index for the 2005 Pacific typhoon season as calculated by Colorado State University using data from the Joint Typhoon Warning Center was 309.9 units.
The 2005 season was a near-average season, the number of typhoons in the year was twenty-three, much less than the average of twenty-seven. The number of typhoons that made landfall in Japan was three, which is almost the average (2.6). In general, this is not a year in which the impact of typhoons has been especially notable. The number of typhoons that passed near Okinawa was eight, which is slightly larger than the average of seven, and this is because this year there are some typhoons moving through the Sakishima Islands towards the Taiwan or China. This year's major typhoons are reviewed below.
Although the season was quiet, some typhoons caused extensive damages in many places, especially in China where eight typhoons struck the country. First, Typhoon Haitang became the strongest storm in the basin this year and caused about $1.1 billion in damages in Taiwan and China in mid July. In August, Typhoon Matsa made landfall in Eastern China and caused about $2.23 billion in damages. Later that same month, two powerful typhoons made landfall, causing extreme damage and some casualties. Similar to Haitang, Typhoon Longwang made landfall in Taiwan and China at a strong intensity causing damages.
Systems
Severe Tropical Storm Kulap
On January 12, a tropical disturbance developed within an area of light vertical wind shear. This allowed deep convection to develop over a broad low-level circulation. The next day, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA) as the system continued to develop. Later that day, they issued their first advisory on Tropical Depression 01W while the storm was located about 215 km (134 mi) southwest of Chuuk. Several hours later, the Japan Meteorological Agency (JMA) also designated the system as a tropical depression. Early on January 15, the JTWC upgraded 01W to a tropical storm as the system turned towards the north. The northward movement was the result of the system traveling along the edge of a low to mid-level ridge located to the east. About 12 hours later, the JMA upgraded the depression to a tropical storm and gave it the name Kulap; which was contributed by Thailand and is the Thai word for rose. Kulap gradually intensified over the next two days, reaching its peak intensity with winds of 95 km/h (59 mph) 10-minute winds) around 1800 UTC on January 17, making it a severe tropical storm according to the JMA. However, at the same time the JMA assessed Kulap to have reached its peak intensity, the JTWC classified it as a minimal typhoon with winds of 120 km/h (75 mph) 1-minute winds). Shortly after reaching its peak intensity, the storm began to undergo an extratropical transition and weaken. Late on January 18, the JTWC issued their final advisory on Kulap despite the storm remaining tropical. The JMA considered Kulap to have been a tropical storm until early the next day. The storm dissipated as a weak extratropical system around 1200 UTC on January 19. Between January 13 and 14, the storm produced heavy rains over the island of Chuuk. Upwards of 300 mm (12 in) of rain fell during the two-day span, of which 166.6 millimetres (6.56 in) fell in 24 hours.
Severe Tropical Storm Roke (Auring)
A tropical disturbance formed on March 11, near the equator. It rapidly developed into Tropical Depression 02W on March 13 as it steadily moved north, then west towards the Philippines. Later that day, it entered warm waters as it was upgraded into Tropical Storm Roke. Due to a strong ridge of high pressure north of it, it moved west-southwest, attaining peak intensity as a severe tropical storm. Roke then entered the PAR, giving the name Auring later that day. It made landfall in eastern Visayas on March 16. The next day, Roke rapidly weakened due to cool waters and dissipated on March 18.
Roke is a male Chamorro name. Seven people were killed and damages amounted to $166,000 (2005 USD).
Typhoon Sonca (Bising)
A large area of convection formed on April 11. Late on April 14, a newly disorganized disturbance formed in that area and steadily intensified. The next two days, the disturbance interacted with another low-pressure area as it moved north towards warm waters. On April 17, the depression weakened due to strong vertical windshear. The JTWC designated as Tropical Depression 03W on April 18. Although the JMA started classifying it as a tropical depression on April 21. It rapidly intensified into a tropical storm, with the JMA naming it Sonca late on April 20. Very early on April 21, the PAGASA classified it as a storm, naming it Bising. Convection built up the storm again on April 22 and entered an area with favorable conditions. The next day, Sonca rapidly intensified into a Category 4 typhoon until it reached peak intensity on mid-April 24. Sonca rapidly weakened due to cool waters and dissipated on April 27.
Typhoon Nesat (Dante)
A tropical depression formed from a tropical wave late on May 28. It rapidly intensified into Tropical Storm Nesat on May 30, rapidly moving west. This was a powerful storm that formed on May 30 about 290 nautical miles (540 kilometres) south-southeast of Guam as Tropical Depression 04W. It was quickly upgraded to Tropical Storm Nesat overnight at 1800 UTC (0200 PHT May 31). Nesat is a Cambodian word for fisherman. On the evening of June 1, it strengthened into Typhoon Nesat. On June 2, it entered the Philippine area of responsibility and was assigned the name Dante for Philippine warnings. Typhoon Nesat (Dante) quickly grew to a Category 4 storm as it approached the Philippines, but it curved away to the northeast and did not pose a threat to land. Waxing and waning in strength it eventually became extratropical southeast of Honshū, Japan at tropical storm strength on the morning of June 10 at 0000 UTC (0900 JST).
Typhoon Haitang (Feria)
An upper-level low associated with an easterly wave occurred late on July 7. It became a tropical depression on the evening of July 11 as a poorly organized depression about 110 nautical miles (200 kilometres) west of Marcus Island, Japan at 1200 UTC (2000 JST). By 1800 UTC (0300 JST July 13), it had reached tropical storm strength and was named Haitang, a Chinese name for flowering crabapple. It grew to typhoon strength at 1800 UTC (0300 JST July 14) the following day. As it moved westward it continued to gain in strength, reaching Category three status as it entered the Philippine area of responsibility. PAGASA named the storm Feria for Philippine warnings on July 15. By July 16, the storm continued tracking west and became a threat to Taiwan and Japan's Sakishima Islands. Haitang strengthened into a Category 5 super typhoon. On July 17 it weakened to a Category 3 as it continued west, sparing Sakishima a direct hit but aiming directly for Taiwan. Typhoon Haitang made landfall near Hualien, Taiwan at 0000 UTC (0800 HKT) on the morning of July 18. Taking a full day to cross the island and over the interior mountains, it caused flash floods and landslides killing four people. Weakening to a tropical storm as it entered the South China Sea, it reorganized into a minimal typhoon as it approached the southeast China coast. Haitang made landfall for the second time near Wenzhou China on July 19 at 1200 UTC (2000 HKT). Moving inland, it rapidly lost its strength and dissipated. PAGASA stopped issuing advisories for the storm near Jiangxi on July 20.
There were 15 deaths in Taiwan and another 14 in mainland China.
Tropical Storm Nalgae
An upper-level low formed on July 17 near warm waters. It steadily intensified, moving north on July 20, with both JMA and JTWC upgrading it as Tropical Storm Nalgae. Later that day, it passed by an area of convection and cluster of thunderstorms, reaching peak intensity on July 21. It maintained its intensity until the afternoon hours of July 22, but the JMA classified it as a severe tropical storm. Nalgae rapidly weakened as it was downgraded into a depression on July 23 by both agencies. The JTWC made its final warnings on the morning of July 24 as it became extratropical. The remnants of Nalgae was absorbed by a large extratropical system from Tropical Storm Banyan on July 28. In post-analysis, the JMA downgraded it to a Tropical Storm.
Tropical Storm Nalgae formed from a tropical disturbance 325 nautical miles (602 kilometres) northwest of Wake Island on the morning of July 20. Nalgae is a Korean word for wing. Nalgae did not reach typhoon intensity or threaten land. It turned to the north and then east, avoiding Japan.
Severe Tropical Storm Banyan
A large tropical disturbance formed late on July 19, which formed in area of high convection and from the outflow of Typhoon Haitang. It rapidly intensified into a strong depression on July 21. While tracking northwards, it was named and upgraded as Tropical Storm Banyan later on July 22. Late on July 23, Banyan reached peak intensity of a severe tropical storm by the JMA until the sunset hours of July 24. Banyan rapidly weakened as it affected Japan by bringing heavy rainfall from July 25 to 28. It made landfall on July 26 and became a large extratropical system on July 27, which made the JTWC issued Banyan's final warning very early on that day. The system absorbed the extratropical remnants of Nalgae the next day and fully dissipated on July 31, affecting Alaska and Canada.