Mar. 18, 2019 – NASA-NOAA Satellite Catches Last Burst of Energy in Tropical Depression 03W
Tropical Depression 03W has dissipated in the Northwestern Pacific Ocean, but not without one last show of strength on infrared satellite imagery.
NASA-NOAA’s Suomi NPP satellite provided an infrared look at Tropical Depression 03W that revealed a burst of strong storms pushing high into the troposphere. 03W’s circulation center was also displaced from the bulk of clouds and precipitation. That’s an indication that vertical wind shear is affecting the storm.
What is Vertical Wind Shear?
In general, wind shear is a measure of how the speed and direction of winds change with altitude. In order to understand how it affects a tropical cyclone or hurricane, think of a tropical cyclone as a series of vertically stacked tires, all rotating. As you go up from the ground, each tire represents the rotation of the storm’s center at a higher level in the atmosphere. The different levels of rotating winds in the center of tropical cyclones need to be stacked on top each other to strengthen. If there are winds higher up that push some of the tires askew near the top, it affects the balance and rotation of the tires below. That’s what happens when vertical wind shear pushes against a storm. It pushes the center and weakens (or wobbles) the rotation of all of the tires.
The Satellite Data Reveal
On March 18 at 1:30 a.m. EDT (0530 UTC), the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard NASA-NOAA’s Suomi NPP satellite analyzed Tropical Storm Depression 03W off-center were as cold as or colder than minus 80 degrees Fahrenheit (minus 62.2 degrees Celsius). NASA research has found that cloud top temperatures as cold as or colder than the 70F/56.6C threshold have the capability to generate heavy rainfall.
The final warning for 03W was issued by the Joint Typhoon Warning Center or JTWC on March 18 at 0900 UTC (5 a.m. EDT). At that time, Tropical depression 03W, also known in the Philippines as Chedeng, was located near 6.6 degrees north latitude and 128.5 degrees east longitude. That’s about 170 nautical miles east of Davao, Philippines. Maximum sustained winds were down to 20 knots (23 mph/37 kph) in the remnant low pressure area.
The remnant low pressure area was moving to the west and are expected to move toward Mindanao, Philippines.
Mar. 15, 2019 – NASA Sees Development of Tropical Depression 03W Near Yap
Visible imagery from NASA’s Terra satellite revealed 03W that formed near the island of Yap in the Northwestern Pacific Ocean.
Yap State is one of the four states of the Federated States of Micronesia. The other three states include Kosrae State, Pohnpei State, and Chuuk State.
A tropical storm watch remains in effect for Yap and Ngulu in Yap State and Kayangel in the Republic of Palau.
On March 15, the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite provided a visible image of 03W in the Northwestern Pacific Ocean. The image showed an elongated storm.
At 2 p.m. EDT (1800 UTC) on March 15 (4 a.m. CHST on March 16 local time) the National Weather Service (NWS), Guam, noted that the center of Tropical Depression 03W was located near Latitude 7.9 degrees North and Longitude 140.9 degrees East. That’s about 130 miles south of Fais and about 220 miles east-southeast of Yap. 03W is moving west at 8 mph and is expected to maintain this general course and speed through the weekend, passing close to Koror on Sunday. Maximum sustained winds remain at 30 mph.
NWS noted “damaging winds are currently not expected at yap. However…the strongest winds are on the north side and 03w is expected to pass south of Yap…meaning that Yap will receive these strong winds as the center of 03w passes by. Small craft should return to port and any small loose objects should be brought indoors.”
03W is forecast to intensify slightly later today but keep below tropical storm force. 03W is forecast to weaken Sunday night, March 17. It is expected to dissipate near Mindanao, Philippines.