Tag: Nangka 2020

Oct. 14, 2020 – NASA Finds Wind Shear Affecting Tropical Storm Nangka Post-Landfall  

Tropical Storm Nangka made landfall south of Haiphong, Vietnam and began to weaken. NASA’s Aqua satellite revealed wind shear was affecting the storm as it continued to push inland.

The Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA’s Aqua satellite captured a visible image of Tropical Storm Nangka on Oct. 14, 2020 at 2:25 a.m. EDT (0625 UTC) that revealed after the storm made landfall it began weaken. In the imagery, strong storms continued to circle the center and were in the northern quadrant.

On Oct 14 at 5 a.m. EDT (0900 UTC), Nangka was centered near latitude 20.2 degrees north and longitude 106.1 degrees east, about 59 nautical miles southeast of Hanoi, Vietnam. Nangka tracked west-northwestward and further inland and was being affected by vertical wind shear.

In general, wind shear is a measure of how the speed and direction of winds change with altitude. Tropical cyclones are like rotating cylinders of winds. Each level needs to be stacked on top each other vertically in order for the storm to maintain strength or intensify. Wind shear occurs when winds at different levels of the atmosphere push against the rotating cylinder of winds, weakening the rotation by pushing it apart at different levels. Once a tropical cyclone makes landfall, the topography contributes to wind shear that weakens a storm’s circulation.

Nangka is forecast to move further inland while dissipating over the mountainous terrain of northwest Vietnam and northern Laos over the next day and a half.

About NASA’s Worldview and Aqua Satellite

NASA’s Earth Observing System Data and Information System (EOSDIS) Worldview application provides the capability to interactively browse over 700 global, full-resolution satellite imagery layers and then download the underlying data. Many of the available imagery layers are updated within three hours of observation, essentially showing the entire Earth as it looks “right now.”

NASA’s Aqua satellite is one in a fleet of NASA satellites that provide data for hurricane research.

Tropical cyclones/hurricanes are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

By Rob Gutro
NASA’s Goddard Space Flight Center

Oct. 13, 2020 – NASA Sees Tropical Storm Nangka Soaking Hainan Island

Using a NASA satellite rainfall product that incorporates data from satellites and observations, NASA estimated Nangka’s rainfall rates as the storm soaked Hainan Island, China early on Oct. 13 (EDT).

Nangka formed in the South China Sea and moved in a westerly direction over the last couple of days.

Nangka’s Status on Oct. 13

At 11 a.m. EDT (1500 UTC), the center of Tropical Storm Nangka was located near latitude 19.1 degrees north and longitude 110.0 degrees east just over Hainan Island, China. It is about 286 nautical miles east-southeast of Hanoi, Vietnam. Nangka is moving toward the west-northwest.

Maximum sustained winds are near 50 knots (58 mph/93 kph) with higher gusts. Nangka is forecast to strengthen slightly in the Gulf of Tonkin (the body of water between Hainan Island, China and Vietnam) and then weaken as it moves toward Vietnam.

Estimating Nangka’s Rainfall Rates from Space

NASA’s Integrated Multi-satellitE Retrievals for GPM or IMERG, which is a NASA satellite rainfall product estimated on Oct. 13 at 8 a.m. EDT (1200 UTC) that Nangka was generating as much as 30 mm (1.18 inches) of rain per hour around the center of circulation.

Rainfall throughout most of the storm and in fragmented bands of thunderstorms north and east of the center was estimated as falling at a rate between 5 and 15 mm (0.2 to 0.6 inches) per hour. At the U.S. Naval Laboratory in Washington, D.C., the IMERG rainfall data was overlaid on infrared imagery from Japan’s Himawari-8 satellite to provide a full extent of the storm.

What Does IMERG Do?

This near-real time rainfall estimate comes from the NASA’s IMERG, which combines observations from a fleet of satellites in near-real time to provide near-global estimates of precipitation every 30 minutes. By combining NASA precipitation estimates with other data sources, we can gain a greater understanding of major storms that affect our planet.

What the IMERG does is “morph” high-quality satellite observations along the direction of the steering winds to deliver information about rain at times and places where such satellite overflights did not occur. Information morphing is particularly important over the majority of the world’s surface that lacks ground-radar coverage. Basically, IMERG fills in the blanks between weather observation stations.

NASA Researches Tropical Cyclones

Hurricanes/tropical cyclones are the most powerful weather events on Earth. NASA’s expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

For more than five decades, NASA has used the vantage point of space to understand and explore our home planet, improve lives and safeguard our future. NASA brings together technology, science, and unique global Earth observations to provide societal benefits and strengthen our nation. Advancing knowledge of our home planet contributes directly to America’s leadership in space and scientific exploration.

For more information about NASA’s IMERG, visit: https://pmm.nasa.gov/gpm/imerg-global-image

For updated forecasts, visit the Hong Kong Observatory: https://www.hko.gov.hk/en/index.html

By Rob Gutro
NASA’s Goddard Space Flight Center