Kujira – Northwestern Pacific Ocean

Sep. 30, 2020 – NASA Imagery Reveals Kujira Transitioning into an Extratropical Cyclone 

Tropical cyclones can become post-tropical before they dissipate, meaning they can become sub-tropical, extra-tropical or a remnant low-pressure area. NASA’s Aqua satellite provided a visible image that showed Typhoon Kujira transitioning into an extra-tropical storm, and the effects of strong wind shear on the system.

Aqua image of Kujira
On Sept. 30 at 0300 UTC (Sept. 29 at 11 p.m. EDT), the MODIS instrument aboard NASA’s Aqua satellite provided a visible image of Kujira that showed the storm had transitioned into an extra-tropical cyclone in the Northwestern Pacific Ocean. Credit: NASA/NRL

What is a Post-tropical Storm? 

A post-tropical storm is a generic term for a former tropical cyclone that no longer possesses sufficient tropical characteristics to be considered a tropical cyclone. Former tropical cyclones that have become fully extratropical, subtropical, or remnant lows are classes of post-tropical cyclones. They no longer possesses sufficient tropical characteristics to be considered a tropical cyclone. However, post-tropical cyclones can continue carrying heavy rains and high winds.

What is an Extra-tropical Storm?

Often, a tropical cyclone will transform into an extra-tropical cyclone as it recurves toward the poles (north or south, depending on the hemisphere the storm is located in). An extra-tropical cyclone is a storm system that primarily gets its energy from the horizontal temperature contrasts that exist in the atmosphere.

Tropical cyclones have their strongest winds near the earth’s surface, while extra-tropical cyclones have their strongest winds near the tropopause – about 8 miles (12 km) up. Tropical cyclones, in contrast, typically have little to no temperature differences across the storm at the surface and their winds are derived from the release of energy due to cloud/rain formation from the warm moist air of the tropics.

Visible NASA Imagery Shows the Transition

Visible imagery from NASA’s Aqua satellite revealed Kujira’s extra-tropical transition under way as the storm appeared asymmetric due to wind shear.

On Sept. 30 at 0300 UTC (Sept. 29 at 11 p.m. EDT), the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Aqua satellite provided a visible image of the storm. Kujira’s center of circulation was surrounded by wispy clouds, while powerful southwesterly vertical wind shear (outside winds that push against a tropical cyclone) had pushed the bulk of clouds and showers northeast of the center.

Kujira’s Final Advisory

At 5 p.m. EDT (2100 UTC) on Sept. 29, the center of Post-Tropical Cyclone Kujira was located near latitude 38.6 degrees north and longitude 159.4 degrees east. That is about 802 nautical miles east of Misawi, Japan. The post-tropical cyclone was moving toward the northeast. As it was transitioning, it weakened from typhoon strength to tropical storm strength. Maximum sustained winds had decreased to near 55 knots (63 mph/102 kph).

In the last bulletin by the Joint Typhoon Warning Center at that time, forecasters noted “Environmental analysis indicates the system has drifted into high vertical wind shear, [greater than 40 knots (46 mph/74 kph) and cold (less than 25 degrees Celsius/77 Fahrenheit) sea surface temperatures] and has entered into the baroclinic zone.” Tropical cyclones need sea surface temperatures of at least 26.6 degrees Celsius/80 degrees Fahrenheit to maintain strength.

A baroclinic zone is a region in which a temperature gradient exists on a constant pressure surface. Baroclinic zones are favored areas for strengthening and weakening systems while barotropic systems, on the other hand, do not exhibit significant changes in intensity. In addition, wind shear is characteristic of a baroclinic zone.

Kujira is expected to complete extratropical transition and weaken to a post-tropical depression by the afternoon of September 30, 2020.

NASA Researches Earth from Space

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.

By Rob Gutro 
NASA’s Goddard Space Flight Center

Kujira – Northwestern Pacific Ocean

Sep. 29, 2020 – NASA’s Infrared View of Typhoon Kujira

NASA’s Terra satellite used infrared light to identify strongest storms and coldest cloud top temperatures in Typhoon Kujira as it tracked through the northwestern Pacific Ocean.

Terra image of Kujira
On Sept. 29 at 7:40 a.m. EDT (1140 UTC), the MODIS instrument aboard NASA’s Terra satellite gathered temperature information about Typhoon Kujira’s cloud tops. MODIS found the most powerful thunderstorms (red) were wrapping around the eye where temperatures were as cold as or colder than minus 70 degrees Fahrenheit (minus 56.6 Celsius). Credit: NASA/NRL

Infrared Data Reveals Most Powerful Storms

Infrared data provides temperature information about the cloud tops of the many thunderstorms that make up a tropical cyclone. The strongest thunderstorms reach high into the atmosphere and have the coldest cloud top temperatures. Tropical cyclones do not always have uniform strength, so infrared data helps forecasters know the location of the strongest side of a storm.

On Sept. 29 at 7:40 a.m. EDT (1140 UTC), the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite gathered temperature information about Typhoon Kujira’s cloud tops. MODIS found the most powerful thunderstorms had temperatures that were as cold as or colder than minus 70 degrees Fahrenheit (minus 56.6 Celsius). Those strongest storms were found wrapping around the eye. In addition, a large band of fragmented thunderstorms east of the center contained storms with those temperatures.

Cloud top temperatures that cold indicate strong storms with the potential to generate heavy rainfall.

Typhoon Kujira’s Status on Sept. 29

At 11 a.m. EDT (1500 UTC) on Sept. 29, Typhoon Kujira’s maximum sustained winds were near 65 knots (75 mph/120 kph), making it a Category One hurricane on the Saffir-Simpson Hurricane Wind Scale. Kujira was far from land areas, centered near latitude 36.5 degrees north and longitude 156.4 degrees east, about 814 nautical miles east of Yokosuka, Japan. Kujira was moving to the north-northeast. It is no threat to land areas.

Forecasters at the Joint Typhoon Warning Center in Honolulu, Hawaii noted that Kujira is forecast to become extra-tropical later in the day on Sept. 29. It is then expected to begin a weakening trend.

NASA Researches Tropical Cyclones

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.

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

 By Rob Gutro
NASA’s Goddard Space Flight Center

Kujira – Northwestern Pacific Ocean

Sep. 28, 2020 – NASA Casts an Infrared Eye on Tropical Storm Kujira’s Very Cold Cloud Tops

NASA analyzed the cloud top temperatures in Tropical Storm Kujira using infrared light to determine the strength of the storm. Infrared imagery revealed that the strongest storms were around Kujira’s center and in a band of thunderstorms on the western side of the storm.

Aqua image of Kujira
On Sept. 28 at 6:15 a.m. EDT (1015 UTC) NASA’s Aqua satellite analyzed Tropical Storm Kujira’s cloud top temperatures and found strongest storms (yellow) were around Kujira’s center of circulation and in a band of thunderstorms in its western quadrant. Temperatures in those areas were as cold as minus 80 degrees Fahrenheit (minus 62.2 Celsius). An area of strong storms with cloud top temperatures as cold as minus 70 degrees (red) Fahrenheit (minus 56.6. degrees Celsius) surrounded the center. Credit: NASA/NRL

The low-pressure area designated System 97W consolidated and strengthened into a tropical depression on Sept. 26 by 5 p.m. EDT (2100 UTC). On Sept. 27 at 11 a.m. EDT (1500 UTC), the Joint Typhoon Warning Center noted that the depression had strengthened into a tropical storm and was renamed Kujira.

An Infrared View of Kujira

One of the ways NASA researches tropical cyclones is by using infrared data that provides temperature information. Cloud top temperatures identify where the strongest storms are located. The stronger the storms, the higher they extend into the troposphere, and the colder the cloud top temperatures.

On Sept. 28 at 6:15 a.m. EDT (1015 UTC) NASA’s Aqua satellite analyzed Kujira using the Moderate Resolution Imaging Spectroradiometer or MODIS instrument. The MODIS imagery showed the strongest storms were around Kujira’s center of circulation and in a fragmented band of thunderstorms in the western quadrant. Persistent deep convection was also obscuring the low-level circulation center.

Temperatures in those areas were as cold as minus 80 degrees Fahrenheit (minus 62.2 Celsius). An area of strong storms with cloud top temperatures as cold as minus 70 degrees Fahrenheit (minus 56.6. degrees Celsius) surrounded the center. NASA research has shown that cloud top temperatures that cold indicate strong storms that have the capability to create heavy rain.

NASA provides data to tropical cyclone meteorologists so they can incorporate it in their forecasts.

Kujira’s Status on Sept. 28

At 11 a.m. EDT (1500 UTC) on Sept. 28, the center of Tropical Storm Kujira was located near latitude 29.7 degrees north and longitude 153.3 degrees east. That is about 286 nautical miles north of Minami Tori Shima. Minami Tori Shima is an isolated Japanese coral atoll located about 1,148 miles (1,848 kilometers) southeast of Tokyo, Japan.

Kujira had maximum sustained winds near 45 knots (52 mph/83 kph) with higher gusts. The storm is moving north through the open waters of the Northwestern Pacific Ocean.

Kujira’s Forecast

Kujira forecast to intensify and track north-northeastward through next 24 hours as it rounds a subtropical ridge (elongated area of high pressure.) Forecasters at the Joint Typhoon Warning Center expect Kujira will begin extratropical transition as it interacts with mid-latitude westerlies (winds) and encounters increasing vertical wind shear (outside winds that can weaken and tear a tropical cyclone apart).

NASA Researches Earth from Space

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.

By Rob Gutro 
NASA’s Goddard Space Flight Center