Latest Update - September 8, 2005 11:28 a.m. EDT
Hurricane Season 2005: Typhoon Nabi
Typhoon Nabi was a Category 2 typhoon in the western Pacific when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this image on September 6, 2005 at 11:05 a.m. Tokyo time. It had sustained winds of around 160 kilometers an hour (100 miles per hour), and it was heading north across the southern end of Japan. The eye of the storm is roughly centered in the image, and the thick storm clouds completely hide the island of Kyushu. To the northeast of the eye, the smaller island of Shikoku and the largest Japanese island, Honshu, are also under the clouds.
These clouds brought a deluge to the southern islands and caused dangerous landslides in the region’s mountainous terrain. The landslides killed several people on Kyushu. As high waves pounded the coast, as much as 51 inches of rain may have fallen in 24 hours as the storm moved slowly northward into the Sea of Japan. The Japanese government had ordered evacuations for more than 100,000 people in the southern islands, according to reports from BBC News. Flights, road traffic, and ferry services were disrupted, and hundreds of thousands of people and businesses lost power. + High resolution image.
Credit: NASA image created by Jesse Allen, Earth Observatory, using data obtained from the MODIS Rapid Response team.
Typhoon Nabi Hits Southern Japan
Typoon Nabi, once a powerful super typhoon, made landfall on Japan's main
southern island of Kyushu with sustained winds reported at 126 kph (78 mph).
Nabi, which means "butterfly" in Korean, continued on over the southwestern tip
of Honshu, triggering mudslides and flooding along the way, before heading out
into the Sea of Japan. The storm left 17 dead and 9 missing in Japan, many as
a result of mudslides. Four people were also reported missing in Korea.
The Tropical Rainfall Measuring Mission (TRMM) satellite has followed Nabi's
progress across the West Pacific. TRMM was Launched back in November of 1997
to estimate rainfall over the global Tropics and has proven itself to be a valuable
platform for monitoring tropical cyclones, especially over remote parts of the
open ocean. With its array of active and passive sensors, TRMM can look into
the very heart of these storms. These two images of Nabi were taken by TRMM and
capture the storm during both its intensifying and weakening stages.
The first image was taken at 11:34 UTC on 31 August 2005 just after Nabi had
entered the easternmost part of the Philippine Sea and was in the process of
intensifying. The image shows the horizontal distribution of rain intensity
within Nabi. Rain rates in the center of the swath are from the TRMM
Precipitation Radar (PR), while those in the outer portion are from the TRMM
Microwave Imager (TMI). The rain rates are overlaid on infrared (IR) data from
the TRMM Visible Infrared Scanner (VIRS). TRMM reveals that Nabi has a small,
closed eye with intense rain (dark red areas) in the southwestern half of the
eyewall. The eye is surrounded by tightly spiraling rain bands (green and blue
arcs), all features of a maturing cyclone. The intense rain near the center
indicates were heat is being released into the storm and driving its
circulation. At the time of this image, Nabi as a Category 2 typhoon with
maximum sustained winds estimated at 95 knots (109 mph) by the Joint Typhoon
Warning Center. Nabi, which was in the process of intensifying, reached
Category 5 intensity by 18 UTC on the 1st of September with sustained winds
estimated at 140 knots (161 mph).
The next image shows Nabi at 08:29 UTC on 5 September as the large eye
of the storm is bearing down on southern Japan. This dramatic image from TRMM
reveals some important clues about the storm. The eye is now very large but
still closed with no rain visible in the broad center. The storm is still
relatively strong but in the process of slowly spinning down. The large eye
indicates that the wind field has spread out, something that can occur in the
later stages of strong tropical cyclones, making it unlikely that the storm
can reintensify. At the time of the image, Nabi was a Category 3 typhoon with
sustained winds estimated at 110 knots (127 mph). Nabi would continue to
weaken as it approached the coastline. TRMM is a joint mission between NASA and the Japanese space agency JAXA. Credit: NASA, Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang
The calm eye of Typhoon Nabi stands out like a bulls-eye in the center of the concentric circles of color that make up the storm. The colors represent wind speed, with purple and pink showing the highest winds, while tiny barbs show the wind’s direction spinning around the eye of the storm. The white barbs indicate regions of heavy rainfall. The image was created using data collected by the QuikSCAT satellite on September 1, 2005, when Nabi was growing into a powerful super typhoon with winds of 260 kilometers per hour (160 miles per hour, 140 knots) and gusts to 315 km/hr (196 mph, 170 knots). At the time this image was taken, however, Nabi had winds of about 213 km/hr (132 mph, 115 knots) with gusts to 260 km/hr (160 mph, 140 knots), making it the equivalent of a Category 3 hurricane on the Saffir-Simpson Hurricane Scale.
The wind speeds shown in this image don't match the winds reported by the Joint Typhoon Warning Center. This is because QuikSCAT measures near surface wind speeds over the ocean based on how the winds affect the ocean. The satellite sends out high frequency radio waves, some of which bounce off the ocean and return to the satellite. Rough, storm-tossed seas return more of the waves, creating a strong signal, while a mirror-smooth surface returns a weaker signal. To learn to match wind speeds with the type of signal that returns to the satellite, scientists compare wind measurements taken by ocean buoys to the strength of the signal received by the satellite. The more measurements scientists have, the more accurately they can correlate wind speed to the returning radar signal.
Typhoons and hurricanes are relatively rare. This means that scientists have few buoy measurements to compare to the data they get from the satellite and can’t match the satellite measurements to exact wind speeds. Instead, the image provides a clear picture of relative wind speeds, showing how large the strong center of the storm is and which direction winds are blowing. To learn more about measuring winds from space, check out NASA’s Winds web site. + High resolution image.
Credit: NASA image courtesy the QuikSCAT Science Team at the Jet Propulsion Laboratory