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Typhoon Chan-hom Heads for China; Invest 96E a Threat to Hawaii

By: Jeff Masters 4:22 PM GMT on July 07, 2015

Category 1 Typhoon Chan-hom is headed westwards towards China, where it is expected to make landfall on Friday or Saturday. Chan-hom passed just north of Guam on Sunday, bringing sustained winds of 46 mph, gusting to 62 mph, to Andersen Air Base; a 3-day rainfall total of 13.83" was recorded. Satellite images show that Chan-hom is a large storm with a prominent eye, and it is expected to take advantage of moderate wind shear and very warm ocean waters and intensify into a Category 4 storm by Thursday.

Figure 1. Triple trouble in the Pacific. From left to right: Tropical Storm Linfa in the South China Sea, Category 1 Typhoon Chan-Hom, and Category 3 Typhoon Nangka. Image was taken by the JMA MTSAT-2 satellite at 0230Z on July 7, 2015. Typhoon Nangka is expected to intensify to Category 5 strength and pass near the uninhabited island of Agrihan in the Northern Mariana Islands on Thursday. Nangka could threaten Japan 8 - 10 days from now as a weaker storm. Tropical Storm Linfa hit the Philippines' northern island of Luzon over the weekend, and is expected to make landfall in China on Thursday as a tropical storm. Image credit: NOAA Viz Lab.

Forecast for Chan-hom
Chan-hom will be steered by a strong ridge of high pressure towards the west-northwest through Thursday, when the typhoon will pass near Miyakojima in the Miyako Islands of Okinawa Prefecture, Japan. Chan-hom is then likely to make landfall in Mainland China north of Taiwan on Friday afternoon or Saturday morning. However, landfall in China is not a sure thing, as a strong trough of low pressure is expected to turn the typhoon northwards as the center nears the coast on Friday. A potential worst-case scenario would be if Chan-hom turns northwards just before hitting the coast, and passes just offshore and very close to Shanghai as a Category 1 or stronger typhoon. The counter-clockwise flow of air around the storm could then potentially bring a significant storm surge to China's most populous city (14 million people.) The majority of Shanghai lies less than 2 meters (6.6 feet) above sea level, and the city is very vulnerable to flooding from storm surge and the heavy rains of typhoons. Shanghai is very important economically--about 14% of China's freight goes through the city. The models are divided in how they handle the trough of low pressure that Chan-hom will encounter late this week, and it is too early to say how much concern we should have for this worst-case scenario. According to 2011 New York Times article, engineers have stretched hundreds of miles of levees along the Yangtze River where it meets the sea in the city. The lowest of those levees were built to withstand a one-in-1,000-year storm surge, and defended Shanghai against the highest tidal surge in modern times, which came during Typhoon Winnie of 1997.

Figure 2. Latest satellite image of Invest 96E.

Invest 96E a threat to Hawaii
Hawaii needs to watch Invest 96E, located about 1300 miles east-southeast of the Big Island. Satellite loops show that 96E is close to tropical depression status, with a pronounced low-level spin and plenty of heavy thunderstorm activity. Wind shear is light, 5 - 10 knots, and ocean temperatures are warm, near 27.5°C. The 8 am EDT Tuesday run of the SHIPS model predicted that wind shear would rise to the moderate level, 10 - 20 knots, by Friday, and ocean temperatures would cool to a marginal 26°C. These conditions should prevent rapid intensification of 96E. Our two most reliable track models, the GFS and European models, show 96E coming within 200 miles of the Hawaiian Islands on Friday. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave 96E 2-day and 5-day odds of development of 90%. An Air Force hurricane hunter aircraft is scheduled to investigate 96E on Wednesday afternoon.

Hawaii has seen an unusual amount of hurricane activity over the past three years. Tropical Storm Flossie passed with 100 miles of the islands in 2013, and an unprecedented three hurricanes in one year passed within 200 miles of Hawaii in 2014. This included Hurricane Iselle, which made landfall on the Big Island on August 8, 2014 as a tropical storm with 60 mph winds--only the second recorded landfall of a tropical storm on the Big Island. Warmer than average ocean temperatures have made this action possible--ocean temperatures along the track of Invest 96E are about 2°F above average, similar to what was seen in 2014.

Jeff Masters


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.