page_title: Tropical Storm Sanba (2018)
section_title: Meteorological history
hierarchical_section_title: Tropical Storm Sanba (2018) / Meteorological history
caption_attribution_description: English: Track map of Tropical Storm Sanba of the 2018 Pacific typhoon season. The points show the location of the storm at 6-hour intervals. The colour represents the storm's maximum sustained wind speeds as classified in the Saffir–Simpson scale (see below), and the shape of the data points represent the nature of the storm, according to the legend below. Saffir–Simpson scale Tropical depression≤38 mph≤62 km/h Category 3111–129 mph178–208 km/h Tropical storm39–73 mph63–118 km/h Category 4130–156 mph209–251 km/h Category 174–95 mph119–153 km/h Category 5≥157 mph≥252 km/h Category 296–110 mph154–177 km/h Unknown Storm type Tropical cyclone Subtropical cyclone Extratropical cyclone / Remnant low / Tropical disturbance / Monsoon depression
context_page_description: Tropical Storm Sanba, known in the Philippines as Tropical Storm Basyang, was a weak tropical cyclone that affected southern and central parts of the Philippines in mid-February 2018. Sanba developed as a tropical depression in the open Pacific Ocean on February 8. The system moved generally westward while slowly developing, finally attaining tropical storm status on February 11. Soon after, wind shear caused the system to lose organization and remain as a minimal tropical storm through February 11 and 12. During this time, Sanba moved westwards then west-northwestwards, making landfall over northeastern Mindanao on February 13. The system weakened into a tropical depression before making another landfall in southeastern Negros later that day. After traversing the Philippine Islands, Sanba failed to reorganize significantly in the Sulu Sea and dissipated two days later west of Palawan.
  As a developing system, Sanba brought minor flooding to Palau. From February 12 to 16, Sanba caused heavy rains, floods, and landslides across the southern and central Philippines, affecting over 250,000 people. About 40,000 people sought shelter in evacuation centers.
context_section_description: Sanba originated from a tropical disturbance that developed about 1,050 mi (1,690 km) southeast of Guam on February 6. The system was initially disorganized and broad, with little thunderstorm activity. Amid generally favorable environmental conditions consisting of warm sea surface temperatures between 28–29 °C (82–84 °F) and moderate wind shear, the disturbance began to develop rainbands and a more well-defined circulation. At 00:00 UTC on February 8, the Japan Meteorological Agency (JMA) deemed the system to have consolidated into a tropical depression. At this time, the system was tracking northwest around a subtropical ridge to the northeast, but soon turned west then southwest as another subtropical ridge to the northwest of the depression strengthened. Over the next day, moderate wind shear kept the depression relatively disorganized, with the circulation remaining elongated. A burst of convection developed over the system on February 10 as it turned to the west, leading the United States-based Joint Typhoon Warning Center (JTWC) to also declare that the system had become a tropical depression at 12:00 UTC. The system quickly increased in organization over the next few hours, with extensive rainbands wrapping into the circulation from the north. As a result, the JTWC and JMA upgraded the system to a tropical storm on February 11 at 00:00 UTC and 06:00 UTC respectively, with the latter naming the system Sanba. At 06:00 UTC, the JMA assessed Sanba to have winds of 40 mph (65 km/h) and a minimum pressure of 1000 hPa (mbar; 29.53 inHg), while the JTWC estimated winds of 45 mph (75 km/h).
  The convective organization of Sanba quickly unraveled over the remainder of February 11, as wind shear caused the storm's low-level circulation center to become exposed. The system entered the Philippine Area of Responsibility before 14:00 UTC, upon which the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) gave it the local name Basyang. Despite the warm ocean waters of the Philippine Sea and strong , and strong outflow channels facilitating thunderstorm development, wind shear kept convection displaced to the northwest of Sanba's center. This meant Sanba stayed as a minimal tropical storm as it headed west-northwest towards Mindanao. On February 13, at around 01:15 UTC, Sanba made landfall in Cortes, Surigao del Sur as a tropical storm. The terrain of the Philippines weakened the system to a tropical depression shortly after. Sanba made a second landfall in Dumaguete City, Negros Oriental at 13:00 UTC, before exiting into the Sulu Sea. Despite conducive sea surface temperatures near 27 °C (81 °F), Sanba's circulation was significantly disrupted by the mountains of the Philippines; the JTWC determined that the system's circulation was no longer closed by 18:00 UTC on February 13. A strong outflow channel briefly assisted convection to develop near Sanba's center on February 14 as the low-level circulation reorganized, and the JTWC assessed that Sanba briefly restrengthened into a tropical depression at around 15:00 UTC. Soon after, strong southeasterly wind shear removed thunderstorm activity from the center once again, leading the JTWC to declare Sanba to have degenerated into a tropical disturbance for the final time. The JMA continued to track the system as a tropical depression until February 16, when they declared that Sanba dissipated as a tropical cyclone at 12:00 UTC over the South China Sea.
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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