May 13, 2008
Typhoon Rammasun Update
Hurricane Season 2008: Typhoon Rammasun (Pacific Ocean)
Typhoon Rammasun became a named storm on May 7, 2008. The storm system formed well away from the coastal areas of the Philippines, and reached Category 4 strength by May 10, making it a Super Typhoon. The typhoon weakened and fell apart over the next few days without ever making landfall.
This data visualization of the storm shows observations from the QuikSCAT satellite on May 10 at 6:12 p.m. local time (9:12 UTC), when Rammasun was near its peak strength. At this time, Rammasun had peak winds around 230 kilometers per hour (145 miles per hour, or roughly 125 knots). The image depicts wind speed in color and wind direction with small barbs. White barbs point to areas of heavy rain.
QuikSCAT measurements of the wind strength of Typhoon Rammasan and other tropical cyclones can be slower than actual wind speeds. QuikSCAT’s scatterometer sends pulses of microwave energy through the atmosphere to the ocean surface and measures the energy that bounces back from the wind-roughened surface. The energy of the microwave pulses changes depending on wind speed and direction.
To relate the radar signal to actual wind speed, scientists compare measurements taken from buoys and other ground stations to data the satellite acquired at the same time and place. Because the high wind speeds generated by cyclones are rare, scientists do not have corresponding ground information to know how to translate data from the satellite for wind speeds above 50 knots (about 93 km/hr or 58 mph).
Also, the unusually heavy rain found in a cyclone distorts the microwave pulses in a number of ways, making a conversion to exact wind speed difficult. Instead, the scatterometer provides a nice picture of the relative wind speeds within the storm and shows wind direction.
May 12, 2008
Typhoon Rammasun Rapidly Weakening, Heading Past Japan
After thundering with sustained winds higher than 100 mph, Typhoon Rammasun, which means "God of Thunder" in Thai, is weakening quickly as it passes south of the main island of Japan.
On Monday, May 12, 2008 at 15:00 Zulu Time (11:00 a.m. EDT), Rammasun's maximum sustained winds dropped to around 74 mph (65 knots). The typhoon was located near 30.2 degrees north latitude and 139.5 degrees east longitude, or 300 nautical miles west-northwest of Japan's island Chichi Jima. It has recently tracked northeastward at 28 knots (32 mph) and was generating waves as high as 19 feet.
The Joint Typhoon Warning Center (JTWC), the lead forecast organization for Rammasun, noted that the typhoon "has continued a rapid weakening trend, with intensity falling by 34 mph (30 knots), over the past 12 hours due to low ocean heat content and high vertical wind shear (winds that tear a storm apart)."
JTWC forecasters noted that Rammasun Is now undergoing extratropical transition. The latest forecast notes "recent animated infrared satellite imagery indicates a rapidly decaying system with a cloud-filled eye and decreased convective banding." The storm will likely become extra-tropical by Tuesday, May 13.
This infrared image (top) of Rammasun was created on May 12 at 4:05 Zulu Time (12:05 a.m. EDT) by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite.
This AIRS image shows the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of Rammasun. The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the Earth, revealing warmer temperatures (red). The main island of Japan is located north of the storm, and the northern edge of Rammasun's clouds (blue and purple) are seen over the southeastern part of Japan.
Rob Gutro, NASA's Goddard Space Flight Center
May 9, 2008
Typhoon Rammasun Intensifying in Open Waters Far South of Japan
The latest typhoon in the western Pacific Ocean is Typhoon Rammasun. Rammasun means "god of thunder" in the Thai language. Its winds are thundering at a sustained 80 knots (92 mph) with gusts to 100 knots (115 mph).
Rammasun developed from an area of disturbed weather between Micronesia and the eastern Philippines slowly early Wednesday, May 7.
On Friday, May 09, 2008 at 12:00 Zulu Time (8:00 a.m. EDT), Rammasun was located near 12.7 degrees north latitude and 132.2 degrees east longitude, or about 845 nautical miles south-southeast of Naha, Okinawa, Japan.
This "god of thunder" was moving north near 7 knots (7 mph) and is expected to continue tracking north, before turning eastward and staying south of Japan, into open waters of the western Pacific Ocean.
This infrared image of Rammasun was created on May 8 at 16:41 Zulu Time (2:41 p.m. EDT) by data from the Atmospheric Infrared Sounder (AIRS), an instrument that flies aboard NASA's Aqua satellite.
This AIRS image shows the temperature of the cloud tops or the surface of Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of Rammasun. The infrared signal of the AIRS instrument does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of Earth, revealing warmer temperatures (red).
Rob Gutro, NASA's Goddard Space Flight Center