Typhoon Vongfong (2014)

Map plotting the storm's track and intensity, according to the Saffir–Simpson scale

Map key

Saffir–Simpson scale

  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown

Storm type

Tropical cyclone

Subtropical cyclone

Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

On September 30, a tropical disturbance began to persist near Ebon Atoll of the Marshall Islands, before the Japan Meteorological Agency (JMA) started to monitor the system as a low-pressure area early on the next day.[15][16] Due to increased consolidation and favorable conditions, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert early on October 2, shortly before the Japan Meteorological Agency (JMA) upgraded the system to a tropical depression.[17][18] More than a half of day later, the JTWC upgraded the system to a tropical depression and designated it as 19W, as a microwave imagery has already revealed the formative banding.[19] When the tropical depression was tracking along the southern periphery of a deep subtropical ridge, the JMA started to issue tropical cyclone advisories at 00:00 UTC on October 3, shortly before the JTWC upgraded 19W to a tropical storm because of further consolidation.[2][20] In the afternoon, the JMA upgraded it to a tropical storm and named it Vongfong, when the fragmented banding was wrapping broadly into the slowly consolidating low-level circulation center with a weak eye-like feature.[1][21]

Under low vertical wind shear and excellent outflow, the JTWC indicated that Vongfong had intensified into a typhoon at 06:00 UTC on October 4, as well as the JMA upgraded the system to a severe tropical storm at noon.[3][22] With an improved northeastward channel into a tropical upper tropospheric trough (TUTT) cell, the storm briefly formed a pinhole eye on October 5, and the JMA upgraded it to a typhoon approximately 330 km (210 mi) east of Guam at 09:00 UTC.[4][23] However, an area of subsidence north of the system and moderate to strong vertical wind shear began to impact Vongfong's development later.[5] The typhoon continued struggling to develop further early on October 6, as the broken convective banding was wrapping into a re-consolidating low-level circulation center.[24] In the second half of day, microwave imageries revealed that a thick eyewall structure had formed under a large central dense overcast, and a new but larger eye began to develop. Moreover, moderate vertical wind shear was being offset by excellent equatorward outflow and the motion of the system, when Vongfong was passing through the Northern Mariana Islands.[25]

Typhoon Vongfong as seen from the International Space Station on October 9.

Once Typhoon Vongfong entered the Philippine Area of Responsibility shortly after 06:00 UTC on October 7, the PAGASA named it Ompong.[6] The system started to undergo rapid deepening early on that day, owing to low vertical wind shear and multiple outflow mechanisms including a TUTT cell positioned to the east. The JTWC upgraded it to a super typhoon at noon, as the system had formed a 40 km (25 mi) round eye surrounded by a symmetric annulus of intense convection.[7] Vongfong reached peak intensity six hours later, when the system's T-number of the Dvorak technique had increased to 7.5 according to both of the JMA and the JTWC, becoming the first tropical cyclone to reach that status since Haiyan in 2013. As the result, the JMA indicated that the maximum ten-minute sustained winds had increased to 215 km/h (134 mph) and the system's atmospheric pressure had dropped to 900 hPa (27 inHg).[8] The JTWC also indicated that Vongfong had become equivalent to a Category 5 hurricane on the Saffir–Simpson hurricane wind scale, with maximum one-minute sustained winds at 285 km/h (177 mph). Additionally, although the typhoon was still generally tracking westward, it noticeably slowed down due to the weakening subtropical ridge.[26]

The system continued maintaining peak intensity and tracked west-northwestward on October 8, although the JTWC indicated that the eyewall had slightly warmed.[27] Having remained at peak intensity for 18 hours and at Category 5-equivalent intensity for 30 hours, Vongfong began to gradually weaken due to an eyewall replacement cycle.[28] The JMA reported that Vongfong had become a large typhoon in the afternoon.[29] Moreover, the system started to track northward along the western periphery of an extension of the subtropical ridge, as well as the poleward outflow channel was slightly diminished owing to the filled (weakened) TUTT cell which previously enhanced outflow.[9] Early on October 10, the JTWC downgraded Vongfong to a typhoon, as the eye became more ragged and surrounded by elongated convection.[30] The typhoon then turned north-northwestward in the afternoon due to some migratory ridging building in the north, when excellent outflow was being enhanced along the poleward side because of the mid-latitude westerlies.[31]

Vongfong totally lost the eye feature owing to increasing southwesterly vertical wind shear on October 11, yet its circulation grew even larger.[32] After crossing Okinawa Island and entering the East China Sea at 15:30 UTC, the overall structure of Typhoon Vongfong diminished more, resulting in the beginning of a significant weakening trend.[10][33] On October 12, the convective organisation was almost diminished, as the only remaining deep convection became contained to the northern flank. Moreover, cold air stratocumulus clouds were observed streaming into the western periphery of the system, as the low level circulation center had become partially exposed and elongated caused by strong vertical wind shear. Because of these reasons, the JTWC downgraded Vongfong to a tropical storm early on that day.[11] The system accelerated east-northeastward along the northwestern periphery of the subtropical ridge in the afternoon and made landfall over Makurazaki, Kagoshima at 23:30 UTC, right before the JMA downgraded Vongfong to a severe tropical storm only a half of hour later.[12][13][34]

On October 13, Vongfong made landfall over Sukumo, Kōchi at 05:30 UTC, Awaji Island, Hyōgo at 10:30 UTC and Izumisano, Osaka at 11:00 UTC, yet the system had started the extratropical transition because of the formation of weak fronts.[35][36] Isolated deep convection was displaced over the east quadrant of the exposed low-level circulation due to strong westerly vertical wind shear.[37] Vongfong became completely extratropical at 00:00 UTC on October 14, shortly after the system arrived at the area off the Pacific coast of the Tōhoku region.[14] Late on October 16, the extratropical system crossed the International Date Line.[38] The storm split into two systems south of the Alaska Peninsula during the afternoon of October 17; however, the low that constituted Vongfong's remnants was absorbed into the new storm only a few hours later, early on October 18.[39][40]

• Other tropical cyclones named Vongfong
• Other tropical cyclones named Ompong
• Typhoon Melor (2009)
• Typhoon Jelawat (2012)
• Typhoon Neoguri (2014)
• Typhoon Phanfone (2014)
• Typhoon Malakas (2016)

Wikimedia Commons has media related to Typhoon Vongfong (2014).

• JMA General Information of Typhoon Vongfong (1419) from Digital Typhoon
• JMA Best Track Data of Typhoon Vongfong (1419) (in Japanese)
• 19W.VONGFONG from the U.S. Naval Research Laboratory