Nida getting knocked by winds, and 97W piquing interestDecember 2, 2009 in Earth / Earth Sciences
Nida is now a tropical storm, and is being knocked around by wind shear in the Western Pacific. Satellite imagery has confirmed Nida's center of circulation is exposed and the storm is losing its circular shape. Meanwhile, System 97W located to Nida's southeast looks ominous on NASA satellite imagery.
Tropical Storm Nida's winds are around 57 mph (50 knots) today, December 2. Nida is moving west-northwest near 9 mph. At 10 a.m. ET, Nida was located about 505 nautical miles southeast of the island of Kadena, near 21.3 North and 134.8 East.
Kadena is a United States Air Force (USAF) base located in the towns of Kadena and Chatan and the city of Okinawa, in Okinawa Prefecture, Japan. Kadena Air Base is the hub of U.S. airpower in the Pacific, and home to the USAF's 18th Wing and a variety of associate units.
NASA satellite data has helped forecasters see that the storm is elongating. Visible data from NASA's Aqua satellite, using the Atmospheric Infrared Sounder (AIRS) instrument showed the storm stretching in a northeast to southwest direction.
In addition, the Joint Typhoon Warning Center (JTWC) noted "Animated multispectral satellite imagery showed a fully exposed low level circulation center (LLCC) nearly one degree to the southwest of increasingly sheared convection." The convection (thunderstorms) near the LLCC is making the center difficult to locate on satellite imagery. The JWTC also notes that "the latest microwave imagery (like that from AIRS and NASA's Advanced Microwave Sounding Unit (AMSU) instruments both on NASA's Aqua satellite) indicates a weakened low level signature as well."
The AMSU instrument on NASA's Aqua satellite also showed that Nida's warm core has contracted and has become increasingly asymmetric. In addition, the core has dropped several thousand feet into the mid to lower troposphere. That's an indication of a weakening storm.
Because wind shear has increased to over 34 mph (30 knots), Lida isn't expected to continue weakening and dissipate over open water in the next three days. In addition, Lida is no longer expected to swing north and track to the west of Iwo To, but will likely keep zigzagging to the west-northwest until it fades.
System 97W, however, looks interesting on NASA satellite imagery. In the latest AIRS imagery 97W can be seen to the east of Tropical Storm Nida. It is centered about 235 miles southeast of Guam, near 10.4 North and 147.1 East. The JTWC has upgraded the likelihood of tropical cyclone formation for this system to "fair."
"Nida getting knocked by winds, and 97W piquing interest" December 2, 2009 https://phys.org/news/2009-12-nida-97w-piquing.html