Typhoon Phanfong a Heavy Rainfall Threat for Japan

Dangerous Category 3 Typhoon Phanfone is steaming northwest at 11 mph towards Japan, and is likely to bring that nation serious flooding problems over the weekend. Satellite loops show that Phanfone is a large and well-organized typhoon with a prominent eye and a large area of intense thunderstorms. However, conditions for intensification are no longer as favorable, with wind shear now a high 20 knots on Friday morning. Ocean temperatures remained warm, though, near 30°C (86°F). Ocean temperatures will cool sharply and wind shear will rise further on Saturday as the typhoon approaches Japan, weakening the storm. Our two top models for predicting typhoon tracks, the GFS and European, predicted with their 00Z Friday runs that Phanfone would hit the main Japanese island of Honshu near 18 UTC on Sunday. The Joint Typhoon Warming Center continues to maintain a forecast keeping the core of the storm offshore of Japan, as they believe Phanfone will be unable to penetrate very far westward into the strong upper-level westerly headwinds that will be present over Japan this weekend. Phanfone will be steadily weakening as it approaches Japan, and should be no stronger than a Category 1 storm at its point of closest approach. Heavy rains from Phanfone will arrive in Japan on Saturday, and are likely to bring dangerous flash flooding and mudslides. The Friday morning 06Z run of the GFDL model predicted that Phanfone would dump widespread rains of 8+ inches across much of Japan. One area of particular concern is the Mt. Ontake volcano, which erupted last Saturday, killing 47 and leaving dozens missing. Phanfone's heavy rains will mobilize Mt. Ontake's ash deposits into dangerous mudflows, seriously complicating the search for victims of Japan's deadliest volcanic eruption in 90 years.


Figure 1. MODIS satellite image from NASA's Aqua satellite of Typhoon Phanfone taken at 01:55 UTC October 3, 2014. At the time, Phanfone was a Category 3 storm with 125 mph winds, and had a 35-mile diameter eye, after completing an eyewall replacement cycle. Compare this to the 5-mile diameter eye seen the previous day (Figure 2, below.) Image credit: NASA.


Figure 2. The pinhole 5-mile diameter eye of Typhoon Phanfone as seen by the VIIRS instrument on the Suomi satellite on October 2, 2014. Image credit: Dan Lindsey, NOAA.


Figure 3. Predicted precipitation for Typhoon Phanfone as simulated by the GFDL model at 06Z Friday October 3, 2014. Phanfone was predicted to dump widespread rains of 8+ inches (yellow colors) across much of Japan. Image credit: NOAA/GFDL.

Next up for Japan: Tropical Storm Vongfong?
The Western Pacific's newest tropical storm, Tropical Storm Vongfong, formed Thursday evening in the Pacific waters about 1800 miles east of the Philippines. The storm is headed west-northwest at 11 mph, and is expected to intensify into a major typhoon by early next week. This storm may also be a threat to Japan 8 - 10 days from now.

Tropical Storm Simon a potential threat to Mexico's Baja Peninsula
In the Eastern Pacific, Tropical Storm Simon, with sustained winds of 60 mph at 11 am EDT Friday, was headed west-northwest at 9 mph away from the coast. Simon is expected to recurve to the north early next week, and could be a heavy rainfall threat to Mexico's Baja Peninsula on Tuesday and Wednesday. However, the models are in substantial disagreement on the long-range fate of Simon. The usually reliable European model keeps the storm well to the west away from Mexico's Baja Peninsula through Friday of next week, while most of the rest of the reliable models (GFS, UKMET, GFDL, and HWRF) show landfall in the Central Baja Peninsula on Tuesday or Wednesday. NHC is currently splitting the difference between these two extremes, since it is unclear which model solution will be correct. If the GFS model is correct, Simon could bring another round of heavy rainfall to the Southwest U.S. late next week.

Quiet in the Atlantic
Our top three models for predicting tropical cyclone genesis show nothing developing in the Atlantic over the next five days. A major outbreak of dry air from the Sahara, unusual for this time of year, is currently in progress over the Tropical Atlantic, which will make it difficult for anything to form between Africa and the Lesser Antilles Islands over the coming week.

Hurricane expert Steve Gregory offers his take on what rest of hurricane season might bring in his Thursday afternoon post.

Jeff Masters