Tropical Storm Ela Little Threat to Hawaii; Category 3 Chan-hom Heads for China

Tropical Storm Ela, the first named storm of the 2015 Central Pacific hurricane season, got its name Wednesday night when an Air Force hurricane hunter aircraft found a small area of 40 mph winds to the northeast of the center. Named storms are rare in the Central Pacific (west of 140°W longitude) this early in the season; the last time the Central Pacific saw a named storm this early in the year was on June 21, 2001 (Tropical Storm Barbara). Ela's formation so early in the year was aided by ocean temperatures about 2°F above average. Ela is headed northwest at 15 mph on a path that should keep the center of the storm at least 200 miles to the northeast of the islands at the time of closest approach on Saturday. Satellite loops continue to show an unimpressive storm, with just one spot of heavy thunderstorms located to the northeast of the center of circulation. High wind shear of about 20 - 25 knots, due to strong upper-level winds out of the south, was keeping any heavy thunderstorms from developing on the southwest side of the storm, closest to the Hawaiian Islands. Ocean temperatures are marginal, near 25.5°C (78°F). The 8 am EDT Thursday run of the SHIPS model predicted that wind shear would slowly rise over the next few days, and ocean temperatures would stay cool, near 25.5 - 26°C. These conditions should cause weakening of Ela. Our two most reliable track models, the GFS and European models, show Ela dissipating by Saturday. I doubt Ela will bring much rain to the islands, and high surf will the main impact on Hawaii.


Figure 1. Typhoon Chan-hom as seen by the MODIS instrument on NASA'a Aqua satellite at 10:05 pm EDT Wednesday, July 8, 2015. At time time, Chan-hom was a Category 2 storm with 105 mph winds. Image credit: NASA.

Dangerous Category 3 Typhoon Chan-hom headed for China
Intensifying Category 3 Typhoon Chan-hom is headed northwestwards at 15 mph towards China, and promises to be a dangerous and very expensive typhoon for a portion of the country unused to strong typhoons. Thursday morning satellite images showed that Chan-hom was a huge storm with a prominent 15-mile diameter eye that was contracting as the storm continued its slow intensification process. Some dry air to the northwest of the storm was keeping the intensification rate relatively slow, as was the lack of a strong upper-level outflow channel. The typhoon is on a track to pass between Japan's Miyakojima and Okinawa islands today. Since Chan-hom's wind field is exceptionally large, with tropical storm-force winds that go out 230 miles from the center, these islands will receive an extended pummeling. As of noon EDT Thursday (midnight local time), Kadena Air Base on Okinawa had already seen sustained tropical storm-force winds of at least 39 mph for eight hours, with sustained peak winds of 58 mph, gusting to 78 mph, at 11:57 pm Thursday local time. With the center of Chan-hom expected to make its closest approach to the island near 2 pm EDT (3 am Friday local time), Okinawa can expect to see at least an 18-hour period of sustained tropical storm-force winds.

Wind shear will be light to moderate and ocean heat content will be high until just after the storm passes these islands, so intensification into a Category 4 storm by Thursday night (U.S. EDT) is likely. On Friday, as Chan-hom approaches China, ocean heat content will fall and wind shear is expected to rise, which should cause weakening. Even so, Chan-hom's very large wind field will be capable of bringing an usually high storm surge to the coast; I expect the storm surge will be one of the five highest in the past century for the coastal region just to the north of where the center makes landfall on Friday evening (U.S. EDT.) However, the exact landfall location in China is quite uncertain, as a strong trough of low pressure is expected to turn the typhoon northwards as the center nears the coast on Friday. As Chan-hom curves to the north a weakens due to interaction with land, the storm is expected to pass very close to Shanghai as a very large and very wet tropical storm. Significant wind damage, coastal flooding, and flooding due to heavy rain is possible in Shanghai, which is China's most populous city (14 million people.)

Dan Lindsey of NOAA/CIRA has put together two impressive loops of Chan-hom at sunset on July 9, 2015, as seen using the high-resolution 0.5 km imagery from the Himawari Satellite: zoomed out and zoomed in.


Figure 2. Triple trouble in the Pacific. From left to right: Tropical Storm Linfa (70 mph winds) just after landfall in South China; Category 2 Typhoon Chan-Hom (105 mph winds) approaching Okinawa; and Category 4 Typhoon Nangka (145 mph winds) passing through the Northern Mariana Islands. Six hours before this image was taken, Linfa was also a typhoon, making it the first time in twenty years the Northwest Pacific had seen three simultaneous typhoons (thanks go to TWC's Michael Lowry for this stat.) Image was taken by the JMA MTSAT at 0530Z on July 9, 2015. Image credit: NOAA Viz Lab.

Elsewhere in the tropics
Typhoon Linfa hit South China's Guangdong province on Thursday at 12:15 local time Thursday as a Category 1 typhoon with 75 mph winds. Linfa has since weakened to a tropical storm, and is expected to track west-southwest towards Hong Kong. Category 4 Super Typhoon Nangka (155 mph winds) is just below Category 5 strength, but is fortunately affecting only a sparsely populated portion of the Northern Mariana Islands. Nagka is on a track that could bring it near Japan on Friday, July 17, but it is too early to assess the risk this storm might pose to Japan. The Atlantic remains quiet, and is dominated by high wind shear and stable dry air. None of our reliable genesis models are showing tropical storm formation in the Atlantic over the next five days.


Video 1. Storm chaser James Reynolds is on Japan's ‪Miyakojima Island, and shot this impressive video (used here with permission) of the massive waves of Typhoon Chan-hom hitting the island. He is posting updates on his Twitter feed.‬

Jeff Masters