|
|
Tropical Cyclone Percy
| Title |
Tropical Cyclone Percy |
| Description |
Cyclone Percy continued its rampage across the South Pacific on March 1, 2005, after battering the Northern Cook Islands with its powerful 260-kilometer-per-hour wind gusts. This Moderate Resolution Imaging Spectroradiometer (MODIS [ http://modis.gsfc.nasa.gov ]) image taken by NASA?s Aqua [ http://aqua.nasa.gov/ ] satellite at 2:40 a.m. local time on February 28 (00:40 UTC on March 1), shows that the storm now has a clearly defined eye. When the image was taken, Percy had just passed over Pukapuku and Nassau, leaving both in shambles. According to news reports, no structures escaped damage on Nassau and just 10 buildings remain intact in Pukapuku. The storm had sustained winds of 213 kilometers per hour (132 mph) with gusts to 260 kph (160 mph), making it a Category 4 storm on the Saffir-Simpson scale. The storm is weakening as it moves south towards the southern Cook Islands and Rarotonga. Percy is the fourth cyclone to strike the Cook Islands in the past four weeks. NASA image courtesy Jeff Schmaltz, MODIS Land Rapid Response Team [ http://rapidfire.sci.gsfc.nasa.gov ] at NASA GSFC. The image is available in additional resolutions. |
|
Tropical Cyclone Percy
| Title |
Tropical Cyclone Percy |
| Description |
Already a powerful Pacific cyclone, Cyclone Percy exploded from a Category 4 storm to a Category 5 cyclone on March 2, 2005. NASA's QuickSCAT satellite captured the change in the above images, taken on March 1 and March 2. The images depict wind speed in color and wind direction with small barbs. The top image shows Percy early on March 1, as the storm was strengthening from a Category 3 storm to a Category 4 storm. The highest wind speeds, shown in purple, are scattered around the center of the storm. By early the next day (lower image), the strongest winds were well-organized around the eye of the storm, resembling a "mini-cyclone." As indicated by the darker shade of purple, the winds are also stronger than they were the previous day. Winds had strengthened around the outer edges of the storm as well. On March 2, high winds represented in red extend further out from the center of the storm, and the lower wind speeds shown in green and yellow cover a smaller area. When the lower image was taken on March 2, Percy was a Category 5 storm, with sustained winds of 260 kilometers per hour (161 mph) and gusts to 315 kph (196 mph). At the time, the storm was over open waters, missing the island nation's Palmerston atoll by 160 kilometers. The images, however, reveal lower wind speeds. This is because the power of the storm makes accurate measurements difficult. The 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, giving scientists a way to monitor wind around the world. Tropical cyclones, however, are difficult to measure. To relate the radar energy return 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 don't have corresponding ground information to know how to translate data from the satellite for wind speeds above 50 knots (about 93 kilometers per hour or 58 miles per hour). Also, the unusually heavy rain found in a cyclone distorts the microwave pulses in a number of ways, making a conversion to accurate wind speed difficult. Instead, the scatterometer provides a nice picture of the relative wind speeds within the storm and shows wind direction. After these images were taken, Cyclone Percy weakened and continued to move south. It is expected to continue to weaken and should just sideswipe the more populated capital of the Cook Islands, Rarotonga. Earlier in the week, Percy destroyed most of the structures on Pukapuka and Nassau, two of the northern Cook Islands. NASA image courtesy the QuickSCAT Science Team [ http://winds.jpl.nasa.gov/ ] at the Jet Propulsion Laboratory. |
|
Tropical Cyclone Percy
| Title |
Tropical Cyclone Percy |
| Description |
Already a powerful Pacific cyclone, Cyclone Percy exploded from a Category 4 storm to a Category 5 cyclone on March 2, 2005. NASA's QuickSCAT satellite captured the change in the above images, taken on March 1 and March 2. The images depict wind speed in color and wind direction with small barbs. The top image shows Percy early on March 1, as the storm was strengthening from a Category 3 storm to a Category 4 storm. The highest wind speeds, shown in purple, are scattered around the center of the storm. By early the next day (lower image), the strongest winds were well-organized around the eye of the storm, resembling a "mini-cyclone." As indicated by the darker shade of purple, the winds are also stronger than they were the previous day. Winds had strengthened around the outer edges of the storm as well. On March 2, high winds represented in red extend further out from the center of the storm, and the lower wind speeds shown in green and yellow cover a smaller area. When the lower image was taken on March 2, Percy was a Category 5 storm, with sustained winds of 260 kilometers per hour (161 mph) and gusts to 315 kph (196 mph). At the time, the storm was over open waters, missing the island nation's Palmerston atoll by 160 kilometers. The images, however, reveal lower wind speeds. This is because the power of the storm makes accurate measurements difficult. The 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, giving scientists a way to monitor wind around the world. Tropical cyclones, however, are difficult to measure. To relate the radar energy return 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 don't have corresponding ground information to know how to translate data from the satellite for wind speeds above 50 knots (about 93 kilometers per hour or 58 miles per hour). Also, the unusually heavy rain found in a cyclone distorts the microwave pulses in a number of ways, making a conversion to accurate wind speed difficult. Instead, the scatterometer provides a nice picture of the relative wind speeds within the storm and shows wind direction. After these images were taken, Cyclone Percy weakened and continued to move south. It is expected to continue to weaken and should just sideswipe the more populated capital of the Cook Islands, Rarotonga. Earlier in the week, Percy destroyed most of the structures on Pukapuka and Nassau, two of the northern Cook Islands. NASA image courtesy the QuickSCAT Science Team [ http://winds.jpl.nasa.gov/ ] at the Jet Propulsion Laboratory. |
|
Tropical Cyclone Percy
| Title |
Tropical Cyclone Percy |
| Description |
Percy, a powerful Category 4 cyclone, is the latest cyclone to threaten the South Pacific. In early February Cyclone Meena hit the Cook Islands, and in mid-February Cyclone Nancy also skirted the Cook Islands while Cyclone Olaf brushed the islands of Samoa and American Samoa. Percy started out as a tropical depression on February 24, 2005, near Tuvalu, just east of the international dateline. The system moved east-southeast staying north of Samoa and steadily increased in strength. It became a cyclone on February 25 and, two days later, grew into a powerful Category 4 cyclone with sustained winds estimated at 115 knots (132 mph) by the Joint Typhoon Warning Center. Percy then slowed down, weakened slightly and battered the atolls of Nassau and Pukapuka in the northern Cook Islands before turning south on February 28. Percy regained Category 4 strength on March 1, and then further intensified into a powerful Category 5 storm on the 2nd with maximum sustained winds estimated at 140 knots (161 mph). In November of 1997, the Tropical Rainfall Measuring Mission, or TRMM satellite, was launched to measure rainfall over the global tropics. TRMM has also turned out to be an excellent observational platform for studying and monitoring tropical cyclones, as shown by this series of images of Cyclone Percy. The top left image, taken at 08:29 UTC on February 28, just as Percy was raking the Nassau and Pukapuka atolls, shows the horizontal distribution of rain intensity. Rain rates in the center swath are from the TRMM Precipitation Radar (PR), the first and only precipitation radar in space, while rain rates 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). TRMM shows an asymmetrical eye with intense rain (dark red area) in the northern part of the eyewall. This rain indicates where heat is being released into the storm. Known as "latent heat," it is the heat released when water vapor condenses into liquid cloud droplets. It is most effective in driving the cyclone's circulation when it is released near the center as is the case shown here by TRMM. The right image was taken at the same time by the TRMM Precipitation Radar (PR), and shows a vertical cross section through the center of the storm looking east. The intense rain (darker red area) is associated with the tallest towers in the northern eyewall. The broad yellow area indicating moderate rain is associated with an outer rainband. At the time of these images, Percy was a Category 3 storm with sustained winds estimated at 105 knots (121 mph). The lower left image was taken at 08:18 UTC on March 2, 2005. At this time Percy was a strong Category 4 cyclone with maximum sustained winds estimated at 130 knots (150 mph). The center of the storm does not fall within the PR swath, which has a higher horizontal resolution than the TMI. However, the TMI is still able to show what appears to a double, eyewall. Mature, intense tropical cyclones undergo what it known as eyewall replacement cycles wherein an outer eyewall forms as a ring surrounding the inner eyewall. The outer eyewall eventually contracts and replaces the inner eyewall. The two eyewalls are evident as the two concentric rings of moderate rain intensity (green areas).TRMM [ http://trmm.gsfc.nasa.gov/ ] is a joint mission between NASA and the Japanese space agency JAXA. Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC). |
|
Tropical Cyclone Percy
| Title |
Tropical Cyclone Percy |
| Description |
Percy, a powerful Category 4 cyclone, is the latest cyclone to threaten the South Pacific. In early February Cyclone Meena hit the Cook Islands, and in mid-February Cyclone Nancy also skirted the Cook Islands while Cyclone Olaf brushed the islands of Samoa and American Samoa. Percy started out as a tropical depression on February 24, 2005, near Tuvalu, just east of the international dateline. The system moved east-southeast staying north of Samoa and steadily increased in strength. It became a cyclone on February 25 and, two days later, grew into a powerful Category 4 cyclone with sustained winds estimated at 115 knots (132 mph) by the Joint Typhoon Warning Center. Percy then slowed down, weakened slightly and battered the atolls of Nassau and Pukapuka in the northern Cook Islands before turning south on February 28. Percy regained Category 4 strength on March 1, and then further intensified into a powerful Category 5 storm on the 2nd with maximum sustained winds estimated at 140 knots (161 mph). In November of 1997, the Tropical Rainfall Measuring Mission, or TRMM satellite, was launched to measure rainfall over the global tropics. TRMM has also turned out to be an excellent observational platform for studying and monitoring tropical cyclones, as shown by this series of images of Cyclone Percy. The top left image, taken at 08:29 UTC on February 28, just as Percy was raking the Nassau and Pukapuka atolls, shows the horizontal distribution of rain intensity. Rain rates in the center swath are from the TRMM Precipitation Radar (PR), the first and only precipitation radar in space, while rain rates 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). TRMM shows an asymmetrical eye with intense rain (dark red area) in the northern part of the eyewall. This rain indicates where heat is being released into the storm. Known as "latent heat," it is the heat released when water vapor condenses into liquid cloud droplets. It is most effective in driving the cyclone's circulation when it is released near the center as is the case shown here by TRMM. The right image was taken at the same time by the TRMM Precipitation Radar (PR), and shows a vertical cross section through the center of the storm looking east. The intense rain (darker red area) is associated with the tallest towers in the northern eyewall. The broad yellow area indicating moderate rain is associated with an outer rainband. At the time of these images, Percy was a Category 3 storm with sustained winds estimated at 105 knots (121 mph). The lower left image was taken at 08:18 UTC on March 2, 2005. At this time Percy was a strong Category 4 cyclone with maximum sustained winds estimated at 130 knots (150 mph). The center of the storm does not fall within the PR swath, which has a higher horizontal resolution than the TMI. However, the TMI is still able to show what appears to a double, eyewall. Mature, intense tropical cyclones undergo what it known as eyewall replacement cycles wherein an outer eyewall forms as a ring surrounding the inner eyewall. The outer eyewall eventually contracts and replaces the inner eyewall. The two eyewalls are evident as the two concentric rings of moderate rain intensity (green areas).TRMM [ http://trmm.gsfc.nasa.gov/ ] is a joint mission between NASA and the Japanese space agency JAXA. Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC). |
|
Tropical Cyclone Percy
| Title |
Tropical Cyclone Percy |
| Description |
Percy, a powerful Category 4 cyclone, is the latest cyclone to threaten the South Pacific. In early February Cyclone Meena hit the Cook Islands, and in mid-February Cyclone Nancy also skirted the Cook Islands while Cyclone Olaf brushed the islands of Samoa and American Samoa. Percy started out as a tropical depression on February 24, 2005, near Tuvalu, just east of the international dateline. The system moved east-southeast staying north of Samoa and steadily increased in strength. It became a cyclone on February 25 and, two days later, grew into a powerful Category 4 cyclone with sustained winds estimated at 115 knots (132 mph) by the Joint Typhoon Warning Center. Percy then slowed down, weakened slightly and battered the atolls of Nassau and Pukapuka in the northern Cook Islands before turning south on February 28. Percy regained Category 4 strength on March 1, and then further intensified into a powerful Category 5 storm on the 2nd with maximum sustained winds estimated at 140 knots (161 mph). In November of 1997, the Tropical Rainfall Measuring Mission, or TRMM satellite, was launched to measure rainfall over the global tropics. TRMM has also turned out to be an excellent observational platform for studying and monitoring tropical cyclones, as shown by this series of images of Cyclone Percy. The top left image, taken at 08:29 UTC on February 28, just as Percy was raking the Nassau and Pukapuka atolls, shows the horizontal distribution of rain intensity. Rain rates in the center swath are from the TRMM Precipitation Radar (PR), the first and only precipitation radar in space, while rain rates 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). TRMM shows an asymmetrical eye with intense rain (dark red area) in the northern part of the eyewall. This rain indicates where heat is being released into the storm. Known as "latent heat," it is the heat released when water vapor condenses into liquid cloud droplets. It is most effective in driving the cyclone's circulation when it is released near the center as is the case shown here by TRMM. The right image was taken at the same time by the TRMM Precipitation Radar (PR), and shows a vertical cross section through the center of the storm looking east. The intense rain (darker red area) is associated with the tallest towers in the northern eyewall. The broad yellow area indicating moderate rain is associated with an outer rainband. At the time of these images, Percy was a Category 3 storm with sustained winds estimated at 105 knots (121 mph). The lower left image was taken at 08:18 UTC on March 2, 2005. At this time Percy was a strong Category 4 cyclone with maximum sustained winds estimated at 130 knots (150 mph). The center of the storm does not fall within the PR swath, which has a higher horizontal resolution than the TMI. However, the TMI is still able to show what appears to a double, eyewall. Mature, intense tropical cyclones undergo what it known as eyewall replacement cycles wherein an outer eyewall forms as a ring surrounding the inner eyewall. The outer eyewall eventually contracts and replaces the inner eyewall. The two eyewalls are evident as the two concentric rings of moderate rain intensity (green areas).TRMM [ http://trmm.gsfc.nasa.gov/ ] is a joint mission between NASA and the Japanese space agency JAXA. Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC). |
|
|
