Typhoon Shanshan struck southern Japan over the weekend, leaving behind at least 9
dead and hundreds injured. Heavy rains from the storm triggered mudslides on the
island of Kyushu in southwestern Japan.
Shanshan (known as Luis in the Philippines) began as a tropical depression (14W) on
the 10th of September 2006 in the central Philippine Sea. Initial movement was to
the northwest. On the evening of the 10th (local time) the depression organized into a
tropical storm and was given the name Shanshan. The system was upgraded to a Category
1 typhoon on the 11th and headed west. Shanshan continued to gradually strengthen,
becoming a Category 2 storm on the 12th with sustained winds estimated at 90 knots
(104 mph) by the Joint Typhoon Warning Center. It was at about this time that the
Tropical Rainfall Measuring Mission satellite (known as TRMM) flew over the storm.
Launched in November of 1997, TRMM was designed to measure rainfall over the global
Tropics using a suite of active and passive sensors, including the world's first
space-borne precipitation radar. TRMM has also proven to be extremely valuable
for monitoring tropical cyclones, especially over remote parts of the open ocean.
This first image from TRMM was taken on 12 September 2006 at 13:08 UTC as Shanshan
was passing through the northern Philippine Sea.
The image shows the horizontal
distribution of rain intensity within the storm. Rain rates in the center swath
are from the TRMM Precipitation Radar (PR), while those in the outer swath are from
the TRMM Microwave Imager (TMI). The rain rates are overlaid on infrared (IR) data
from the TRMM Visible Infrared Scanner (VIRS). The image shows that Shanshan has
a well-developed eastern eyewall containing intense rainfall (dark red arc). There
is tight banding (curvature) surrounding the center, which is indicative of a well-
developed circulation that is commonly associated with a mature tropical cyclone.
The next image was taken coincidentally with the first and shows a 3D perspective of
the storm courtesy of the TRMM PR. Higher echo tops are shown in red. The highest
tops exceed 15 km and are associated with the intense rainfall in the eastern eyewall.
These deep convective towers are what drive the storm's circulation by releasing heat
into its core.
Shanshan continued to track to the west and maintained Category 2 intensity for
another day before weakening slightly. However, as the typhoon approached Taiwan it
turned north and re-intensified eventually reaching Category 4 intensity with
sustained winds estimated at 120 knots (138 mph). Shanshan then moved off to the
northeast towards southern Japan, passing west of Okinawa. As the system approached
southern Japan, it began to weaken and made landfall on western Kyushu as a
Category 1 storm.
The final image was taken by TRMM at 8:31 UTC on the 17th of
September just as Shanshan was making landfall on Kyushu. An area of intense rain
(darker red) is located near the center over the western tip of Kyushu. A broad area
of light (blue) to moderate (green) rain extends out ahead of the storm. Shanshan
continued to weaken but is still expected to bring heavy rains to northern Japan as
it moves up the Sea of Japan.
