Thursday, September 15, 2011

Tropical Storm Roke Update #4

Tropical Storm Roke remains a weak cyclone as it nears Okinawa Islands. The low-level center was last located approximately 330km east southeast of Okinawa and is just south of the Daito Islands. Maximum sustained winds remain at 65kph gusting to 90kph. Roke is moving west northwestward at 15kph.

Recent radar image from JMA now showing bands of moderate to heavy rain from Roke beginning to affect Daito Islands. Furthermore, Minami-Daito is reporting easterly winds of around 20 to 30kph with minimum pressure of around 990mb--indication that the center is just nearby (south). Expect rainfall amounts of 100 to 200mm in 24 hours.

Radar from JMA, for more images click HERE

Forecast for TS Roke remain well up in the air. We do know that it will begin to move closer to Okinawa within the next two days. Closest point of approach would be Saturday night/early Sunday morning as it moves just north of the Okinawa Islands. Winds of 30 to 50kph will begin affecting Okinawa and Amami tomorrow and will get stronger throughout Friday and Saturday.

Short-Term Forecast (image from NRLMRY); times indicated are Philippine Time-add one hour for Japan Time

You can see in this very simple steering flow chart (below) showing the location of the Ridge east of Japan (blue lines with the letter "H"). This is steering Roke to the west. What will happen is a trough will approach from the west (yellow line with the letter "L"). This will weaken the ridge in Japan and cause it to move eastward. At the same time, a new ridge is forecast to form in Eastern China (another blue line, this time in China) and due to the anti-cyclonic (clockwise) flow, this will steer Roke to the southwest. This is supposed to be temporary and Roke will meander just west of Okinawa in a week steering environment for until Tuesday next week. Computer models begin to diverge widely at this point and my forecast is siding with the ECMWF (EURO) output.

Personal Forecast (NOT OFFICIAL)

For an update on Tropical Storm Sonca, please read our other post. We'll have another update tomorrow.
Issued (09 UTC) 5pm PhT 091511

No comments:

Post a Comment