Tropical Storm Phanfone Nears Guam; Typhoon Threat For Japan?

Jon Erdman and Nick Wiltgen
Published: September 29,2014



 
Tropical Storm Phanfone, formed this past weekend in the western Pacific Ocean, and is gathering strength east-northeast of Guam. Phanfone could eventually pose a threat as a strong typhoon next week. Let's break down what we know now.
(MORE: Expert Analysis | Hurricane Central)

Guam Impact

Phanfone is forecast to move northwest over the next several days. First up for Phanfone are the Mariana Islands.
While the center of Phanfone should track north of Guam, a tropical storm warning and a typhoon watch are posted for the northern Mariana Islands including Saipan, Tinian, Pagan, Alamagan and the surrounding waters.
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Phanfone may become a typhoon -- the western Pacific Ocean's equivalent of a hurricane -- before clearing the Marianas and moving on to the west-northwest.

Japan Typhoon Threat?

An exceptionally favorable environment of low wind shear and high sea-surface temperatures is anticipated as Phanfone continues to move to the west-northwest this week.
This should allow it to strengthen into a powerful typhoon later this week. A cycle of rapid intensification could occur, given the favorable environmental conditions. As a result, the U.S. military's Joint Typhoon Warning Center forecasts Phanfone to become the equivalent of a Category 4 tropical cyclone on the Saffir-Simpson Hurricane Wind Scale later this week.
With the potential for Phanfone to become a very powerful tropical cyclone, the forecast track becomes critical.
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Official forecasts from JTWC, as well as the Japan Meteorological Agency, show Phanfone gently curving northwestward and northward late this week, toward the end of the 5-day forecast period. This would take it past Iwo Jima and into a region of ocean west of Japan's Izu Islands and east of Japan's Ryukyu Islands, the two main north-south chains of small islands south of the Japanese mainland.
However, there are some key questions and uncertainties about Phanfone's track.
An east-west bubble of high pressure sitting to the north of Phanfone will keep the cyclone on its westward to west-northwestward course over the next few days. Eventually, however, Phanfone may reach a weak spot in that bubble -- and tropical cyclones are often drawn northward in those situations before eventually being forced northeastward by the prevailing westerlies, usually becoming post-tropical systems in the process.
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However, if this bubble of high pressure stays relatively strong and the weak spot doesn't materialize, Phanfone may not curve north and norhteast as quickly -- or even at all. The major computer forecast models are not in good agreement on this issue, which becomes a critical question roughly 5 to 7 days from now.
As a result, there are several plausible scenarios, including these:
- Phanfone curves sharply, passing south and east of mainland Japan and brushing the country with high waves and possibly a little bit of rain.
- Phanfone curves north a bit later, too late to miss Japan, and instead slams into the heavily populated Japanese mainland, anywhere from Tokyo in the east westward to Nagoya, Osaka, or Kobe in central Japan, or even Fukuoka in the west.
- Phanfone waits even longer to recurve or stays on a more westerly track altogether, taking it more toward Okinawa, Taiwan, and eventually China.
(MORE: Expert Analysis)
Stay with The Weather Channel and weather.com for more on this potentially dangerous typhoon.