Choi-Wan, which began as a tropical depression back on September 12 about 500 miles (~800 km) east-southeast of Saipan, became the third category 4 typhoon in the Pacific this year as it was approaching the Northern Mariana Islands on September 15 (local time). Today, September 16, Choi-Wan is a Category 5 typhoon. The Tropical Rainfall Measuring Mission satellite (better known as TRMM) has served as a valuable platform for monitoring tropical cyclones since its launch back in 1997, especially over remote parts of the ocean. TRMM captured its first image of Choi Wan at 23:34 UTC on September 13, 2009 as the storm was moving due west about 200 miles (~320 km) east-northeast of Saipan. The image showed the horizontal distribution of rain intensity inside the storm. Rain rates in the center of the swath were created from the TRMM Precipitation Radar (PR), the only spaceborne radar of its kind, while those in the outer portion were created from the TRMM Microwave Imager (TMI). The rain rates were overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS). Although not fully formed on September 13, it was evident in the TRMM satellite imagery that Choi-Wan already had a well-defined eye structure with an eyewall wrapping all the way around the center except in the southeastern quadrant. Associated with the areas of heavy rain are intense thunderstorms that are fueling the storm by releasing heat into its core. Rain features surrounding the eye appeared all tightly curved, which is consistent with a mature cyclonic circulation. At the time of that first image, Choi-Wan was still just a Category 1 typhoon with maximum sustained winds estimated at 65 knots (~75 mph) by the Joint Typhoon Warning Center, but it would quickly intensify into a Category 4 storm with sustained winds estimated at 120 knots (~138 mph) less than day later. Choi-Wan passed through the Northern Marianas as a Category 4 storm on the afternoon (local time) of the September 15 before heading northwest into the Philippine Sea where it intensified even further into a powerful Category 5 Super Typhoon.
TRMM captured another image of Choi-Wan at 23:20 UTC on September 15 (September 16, 9:20 a.m. local time) as it was moving northwest through the eastern Philippine Sea after passing through the Northern Marianas Islands. The storm now had a near perfect eye surrounded by a very intense eyewall with very heavy rain on its western side. Overall the storm is also very symmetric both in its cloud and rain patterns. This highly symmetrical structure is a manifestation of its extreme intensity and cyclonic structure as features are quickly wrapped around in a circular orientation. At the time of the second TRMM image, Chan-Woi was a Category 5 Super Typhoon with sustained winds estimated at 140 knots (~161 mph). TRMM is a joint mission between NASA and the Japanese space agency JAXA. On September 16 at 11 a.m. EDT (1 a.m. September 17 local time) Choi-Wan still had maximum sustained winds near 161 mph, and was a Category Five typhoon. It was moving west-northwest near 8 mph. It was located about 335 miles south of Iwo To (formerly known as Iwo Jima) near 19.5 north and 141.5 east. The storm is expected to recurve to the north and remain east of Japan. |
So far, there have been 16 tropical depressions in the Eastern Pacific, and Marty grew from the sixteenth. Three of the depressions never grew into tropical storms. Marty, however, has maximum sustained winds near 40 mph and is expected to strengthen. At 11 a.m. EDT today, he was located about 320 miles south-southwest of the southern tip of Baja California, near 18.9 north and 112.4 west. Marty is moving near 3 mph and has a minimum central pressure near 1003 millibars. The GOES-11 satellite captured an image of Tropical Storm Marty off the western Mexican coast on Wednesday, September 16 at 2:45 p.m. EDT. GOES is operated by the National Oceanic and Atmospheric Administration. NASA’s GOES Project, located at NASA’s Goddard Space Flight Center, Greenbelt, Md. creates some of the satellite images from the GOES satellites. Currently Marty is no threat to land, but he’s expected to move close to Baja California by the weekend. Text credit: Rob Gutro, NASA/Goddard Space Flight Center |
