Wallace (Southern Indian Ocean)

Apr. 10, 2019 – NASA-NOAA Satellite Sees Tropical Cyclone Wallace Dissipating

Tropical Cyclone Wallace was dissipating in the Southern Indian Ocean when NASA-NOAA’s Suomi NPP satellite passed overhead.  Wallace was located off the northwestern coast of Western Australia.

Suomi NPP image of Wallace
NASA-NOAA’s Suomi NPP satellite passed over the Southern Indian Ocean and captured a visible image of Tropical Cyclone Wallace on April 10 as it continued to dissipate off the coast of Western Australia. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS).

The Australian Bureau of Meteorology or ABM noted that a Strong Wind Warning was in effect for the Esperance Coast and Eucla Coast on April 10 as Wallace continued weakening far off the coast of Western Australia.

NASA-NOAA’s Suomi NPP satellite passed over Wallace on April 10 and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument provided a visible image of the storm. The VIIRS image showed wind shear has pushed the bulk of the system’s clouds southeast of the center, and was tearing the storm apart.

At 11 p.m. EDT on April 9 (0300 UTC on April 10), the Joint Typhoon Warning Center issued the final bulletin on Tropical Cyclone Wallace. At that time, maximum sustained winds were near 35 knots (40 mph/65 kph). Wallace was centered near 16.9 degrees south latitude and 111.9 east longitude. That’s about 344 nautical miles north-northwest of Learmonth. Wallace was moving to the west.

Wind shear is forecast to increase over April 10 and Wallace is expected to dissipate by April 11.

By Rob Gutro 
NASA’s Goddard Space Flight Center

Wallace (Southern Indian Ocean)

Apr. 09, 2019 – NASA Imagery Shows Winds Tearing Tropical Cyclone Wallace

Visible imagery from NASA’s Terra satellite showed Tropical Cyclone Wallace being sheared apart from strong northwesterly winds. Clouds from Wallace stretched far inland over a well-known wilderness area.

Terra image of Wallace
On April 9, 2019, the MODIS instrument aboard NASA’s Terra satellite provided a visible image of Tropical Cyclone Wallace in the Southern Indian Ocean, off the coast of Western Australia. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS)

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.

On April 9, the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite provided a visible image of Wallace. Wallace’s center was over the Southern Indian Ocean and well off the Pilbara coast of Western Australia. Northwesterly winds were pushing the bulk of Wallace’s clouds southeast of its center.

Wallace’s southeastern quadrant was spreading clouds along the Pilbara coastline of northern Western Australia from Exmouth north to Port Hedland. Clouds were being pushed far inland and were streaming over Karijini National Park. The park is a large wilderness area in the Hamersley Range of Western Australia.

At 8 a.m. EDT (8:00 p.m. AWST local time), the Australian Bureau of Meteorology or ABM reported that Tropical Cyclone Wallace was located near 16.5 degrees south latitude and 113.9 east longitude. That is 560 km north-northwest of Karratha and 610 km north of Exmouth. Wallace was moving west-southwest at 7 kilometers per hour. Maximum sustained winds were near 45 knots (52 mph/83 kph).

ABM said “Tropical Cyclone Wallace will continue to weaken as it tracks westwards.

Wallace is forecast to be below tropical cyclone intensity by Wednesday [April 10] afternoon.

For updated forecasts from the Australian Bureau of Meteorology, visit: http://www.bom.gov.au

By Rob Gutro
NASA’s Goddard Space Flight Center

Wallace (Southern Indian Ocean)

Apr. 08, 2019 – NASA-NOAA Satellite Finds a More Circular Tropical Cyclone Wallace

NASA-NOAA’s Suomi NPP satellite passed over the Southern Indian Ocean and captured a visible image of what appeared to be a more organized Tropical Cyclone Wallace, off the coast of Western Australia.

Suomi NPP image of Wallace
NASA-NOAA’s Suomi NPP satellite passed over the Southern Indian Ocean and captured a visible image of Tropical Cyclone Wallace, on April 8, as it continued to move away from the coast of Western Australia. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS).

The Australian Bureau of Meteorology or ABM noted that only a High Seas Warning was in effect off the coast of Western Australia, as Wallace continues to track away from the coast.

NASA-NOAA’s Suomi NPP satellite passed over Wallace on April 8 and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument provided a visible image of the storm. The VIIRS image showed bands of thunderstorms from the western to the southern quadrants.

ABM noted on April 8 “An eye is starting to emerge on the most recent imagery with the system adopting a more circular appearance.” At 5:43 a.m. EDT (0943 UTC) satellite imagery showed strong convection (rising air that forms thunderstorms that make up a tropical cyclone) partially wrapping around the center to the west and south of the center.

At 8:41 a.m. EDT (8:41 pm WST local time, Western Australia) on April 8, Tropical Cyclone Wallace near 15.8 degrees south latitude and 115.8 east longitude. That’s about 560 km (348 miles) north northwest of Karratha. Wallace was moving southwest at 17 kilometers (10.5 miles) per hour. Maximum sustained winds were near 60 knots (69 mph/110 kph).

ABM stated that Wallace is forecast to strengthen over the next day or two before weakening below tropical cyclone intensity Wednesday [April 10] afternoon or evening.

A strong mid-level elongated area of high pressure or a ridge, located to Wallace’s southeast, will steer the system to the southwest overnight and then a more westerly track during Tuesday and Wednesday. Wallace is expected to remain well offshore from the Western Australian coastline and is not expected to affect the coast of Western Australia.

For updated forecasts, visit the ABM website: http://www.bom.gov.au/cyclone/index.shtml

By Rob Gutro 
NASA’s Goddard Space Flight Center

Wallace (Southern Indian Ocean)

Apr. 05, 2019 – Warnings Up in Western Australia as Suomi NPP Satellite Views Tropical Cyclone 23S

Tropical Cyclone 23S has developed north of the Kimberley coast, and generated warnings. NASA-NOAA’s Suomi NPP satellite passed overhead as the low pressure area consolidated into a tropical cyclone.

Suomi NPP Image of 23S (Wallace)
NASA-NOAA’s Suomi NPP satellite passed over the Southern Indian Ocean and captured a visible image of Tropical Cyclone 23S or Wallace, on April 5, as skirted the coast of Western Australia. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS).

23S is expected to be renamed Tropical Storm Wallace as it falls in Australia’s area of responsibility, and follows their naming list.

The Australian Bureau of Meteorology or ABM posted warnings from Kalumburu to Beagle Bay, not including Derby.

NASA-NOAA’s Suomi NPP satellite passed over 23S on April 5 and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument provided a visible image of the storm. The VIIRS image showed an elongated storm. The southeastern quadrant of 23S was over the Kimberly coast. The Joint Typhoon Warning Center or JTWC noted “animated multispectral satellite imagery which depicts isolated, deep central convection and shallow rain bands.”

JTWC stated at 5 a.m. EDT (0900 UTC) that 23S was located near 12.0 south latitude and 127.4 east longitude, about 207 nautical miles (238 miles/383 km) west of Darwin, Australia. 23S was moving to the west-southwest and had maximum sustained winds near 35 knots (40 mph/65 kph), making it tropical-storm force.

Tropical Storm 23S is forecast to move west-southwest while intensifying over the next four days as it moves parallel to the coast of Western Australia. The ABM noted “there remains a slight risk that the cyclone could approach the west Pilbara coast next week.”

For updated forecasts, visit the ABM website: http://www.bom.gov.au/cyclone/index.shtml

By Rob Gutro 
NASA’s Goddard Space Flight Center

Joaninha (Southern Indian Ocean)

Apr. 01, 2019 – NASA Finds Wind Shear Tearing Apart Subtropical Cyclone Joaninha

Visible imagery from NASA’s Terra satellite revealed that strong wind shear was adversely affecting Subtropical Cyclone Joaninha in the Southern Indian Ocean.

Terra image of Joaninha
On April 1 at 1:20 a.m. EDT (0520 UTC), the MODIS instrument aboard NASA’s Terra satellite provided a visible image of Subtropical Cyclone Joaninha that showed the storm was being adversely affected by vertical wind shear. Credit: NASA/NRL

On April 1 at 1:20 a.m. EDT (0520 UTC), the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite provided a visible image of Subtropical Cyclone Joaninha. Joaninha transitioned into a subtropical storm over the weekend of March 30 and 31. Joaninha’s center was surrounded by a swirl of clouds around its center with most of its clouds and thunderstorms pushed southeast of center. Strong westerly to northwesterly vertical wind shear were tearing the storm apart.

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.

On March 31 at 0300 GMT, March 31 (11pm EDT March 30), the Joint Typhoon Warning Center issued the final bulletin on Joaninha. At that time, Joaninha was located near 26.8 degrees south latitude and 69.8 degrees east longitude, about 796 miles east-southeast of Port Louis, Mauritius. It was moving south southwest. Maximum sustained winds at the time were near 35 knots (40 mph/65 kph) and it was weakening.

Joaninha continued to dissipate from adverse atmospheric conditions.

By Rob Gutro
NASA’s Goddard Space Flight Center

Joaninha (Southern Indian Ocean)

Mar. 29, 2019 – Satellite Finds Tropical Cyclone Joaninha Slammed by Wind Shear

One day makes a big difference when you’re a tropical cyclone. On March 28, Tropical Cyclone Joaninha still maintained an eye, and on March 29, once outside winds ramped up, the storm weakened quickly. NOAA’s NOAA-20 satellite provided an image of the storm that showed a large area of thunderstorms were pushed away from the center.

NASA-20 image of Joaninha
NOAA’s NASA-20 satellite passed over Tropical Cyclone Joaninha on March 29 at 5:24 a.m. EDT (0924 UTC) and captured this image of the storm, starting to show effects of wind shear. Credit; NOAA/NRL

On March 29, 2019 at 11 a.m. EDT (1500 UTC), Joaninha’s maximum sustained winds dropped to 65 knots. It was centered near 23.6 degrees south latitude and 68.6 degrees east longitude. That’s approximately 655 nautical miles east-southeast of Port Louis, Mauritius. Joaninha was moving to the southeast.

When NOAA’s NASA-20 satellite passed over Tropical Cyclone Joaninha on March 29 at 5:24 a.m. EDT (0924 UTC) the VIIRS instrument aboard captured a visible image of the storm. Satellite imagery showed struggling central deep convection (rising air that condenses into clouds and thunderstorms that make up a tropical cyclone) being pushed away from the low level circulation center to the east.

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.

Increasing westerly vertical wind shear above 30 knots continues to affect the system’s structure, leading to rapid weakening. That wind shear is forecast to increase, according to the Joint Typhoon Warning Center or JTWC. In addition, Joaninha is expected to move into sea surface temperatures cooler than the 80 degree Fahrenheit (26.6 degree Celsius) threshold needed to maintain a storm. Between the increasing wind shear and cooler waters, Joaninha is expected to continue to weaken.

JTWC also noted that within three days, “the cyclone will begin to transition from a tropical to subtropical storm with expansive, asymmetric, gale force wind radii as it merges with a cutoff low pressure area.”

By Rob Gutro
NASA’s Goddard Space Flight Center

Joaninha (Southern Indian Ocean)

Mar. 28, 2019 – NASA Finds Tropical Cyclone Joaninha Maintaining an Eye

Tropical Cyclone Joaninha is not yet ready to close its eye and weaken. Visible imagery from NASA’s Terra satellite showed Tropical Cyclone Joaninha maintaining an eye thanks to low wind shear and warm sea surface temperatures.

Terra image of Joaninha
On March 28, 2019, the MODIS instrument aboard NASA’s Terra satellite provided a visible image of Tropical Cyclone Joaninha in the Southern Indian Ocean. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS)

On March 28 the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite provided a visible image of Joaninha. Joaninha had maintained its eye, although appearing more ragged looking than in satellite imagery the previous day. The ragged eye was surrounded by powerful thunderstorms in a thick eyewall.

Moving Through Warm Sea Surface Temperatures

The sea surface temperatures in the area of the tropical cyclone were still warm enough to support and maintain the tropical cyclone. Infrared satellite imagery provides sea surface temperature data. Tropical cyclones need sea surface temperatures of at least 26.6 degrees Celsius (80 degrees Fahrenheit) and Joaninha is moving through an area where the sea surface temperatures range between 26 and 28 degrees Celsius (78.8 and 82.4 degrees Fahrenheit).

At 5 a.m. EDT (0900 UTC) on Thursday, March 28, 2019, maximum sustained winds near Joaninha’s center were near 115 knots (132 mph/213 kph). Joaninha was centered near 21.2 degrees south latitude and 67.4 degrees east longitude. That’s about 570 nautical miles east of Port Louis, Mauritius.

Joaninha is expected to move into an area that is unfavorable for it to maintain strength. The Joint Typhoon Warning Center or JTWC noted “Increasing westerly vertical wind shear associated with a mid-latitude trough (elongated area of low pressure) approaching from the southwest will compete with flow into that trough to produce a gradual weakening trend” as Joaninha tracks southward and along the edge of an area of elongated high pressure, located to the east.

In four days, Joaninha is expected to merge with an area of low pressure and transition into a subtropical storm.

What is a Sub-tropical Storm?

 According to the National Oceanic and Atmospheric Administration, a sub-tropical storm is a low-pressure system that is not associated with a frontal system and has characteristics of both tropical and extratropical cyclones. Like tropical cyclones, they are non-frontal that originate over tropical or subtropical waters, and have a closed surface wind circulation about a well-defined center.

Unlike tropical cyclones, subtropical cyclones derive a significant proportion of their energy from baroclinic sources (atmospheric pressure), and are generally cold-core in the upper troposphere, often being associated with an upper-level low pressure area or an elongated area or trough of low pressure.

In comparison to tropical cyclones, these systems generally have a radius of maximum winds occurring relatively far from the center (usually greater than 60 nautical miles), and are generally less symmetric.

By Rob Gutro
NASA’s Goddard Space Flight Center

Idai (Southern Indian Ocean)

Mar. 28, 2019 – Darkness in the Wake of Idai
Suomi NPP image of Idai aftermath
The image on the left shows the extent of electric lighting across Beira on March 9, 2019, a typical night before the storm hit; the image on the right shows light on March 24, 2019, three days after Idai had passed. Nearly all electricity and internet went out, except near the airport where relief organizations had set up a server.

In March 2019, Tropical Cyclone Idai pummeled through southeastern Africa to become one of the deadliest storms ever recorded to hit the Southern Hemisphere. The storm caused catastrophic floodinglandslides, and large numbers of casualties across Mozambique, Malawi, and Zimbabwe. One of the most affected areas was Beira, Mozambique’s second-largest port city of 530,000 people, where the cyclone made landfall on March 14.

The storm “destroyed 90 percent” of Beira, according to an initial assessment by a team from the International Federation of Red Cross and Red Crescent Societies. As of March 20, an estimated 1 million people were without electricity.

The image on the left shows the extent of electric lighting across Beira on March 9, 2019, a typical night before the storm hit; the image on the right shows light on March 24, 2019, three days after Idai had passed. Nearly all electricity and internet went out, except near the airport where relief organizations had set up a server.

These images of Beira’s nighttime lights are based on data captured by the Suomi NPP satellite. The data was acquired by the Visible Infrared Imaging Radiometer Suite (VIIRS) “day-night band,”which detects light in a range of wavelengths from green to near-infrared, including reflected moonlight, light from fires and oil wells, lightning, and emissions from cities or other human activity. A team of scientists from NASA’s Goddard Space Flight Center and Marshall Space Flight Center processed and corrected the raw VIIRS data to filter out stray light from sources that are not electric lights as well as other atmospheric interference, such as dust, haze, and thin clouds. The base map makes use of data collected by the Landsat satellite.

The cyclone also knocked out transmission lines in Mozambique that carry power to South Africa. The major state-owned utility company in South Africa has been administering controlled blackouts for more than a week to conserve energy until power lines are fixed, which may take weeks to months.

Idai dissipated on March 21, but had already dumped heavy rains on approximately 23,000 square kilometers (900 square miles) of land—an area larger than New York City and Los Angeles combined. In Mozambique, the storm inundated more than 360,000 hectares (900,000 acres) of crops, damaged at least 17,000 houses, and dozens of health units.

IMERG data on rainfall after Idai
The map above shows rainfall accumulation from March 13 to March 20, 2019. Many areas received as much as 50 centimeters (20 inches) of rain. These data are remotely-sensed estimates that come from the Integrated Multi-Satellite Retrievals (IMERG), a product of the Global Precipitation Measurement (GPM) mission. Local rainfall amounts can be significantly higher when measured from the ground. Credit: NASA

NASA Earth Observatory images by Joshua Stevens, using Black Marble data courtesy of Ranjay Shrestha/NASA Goddard Space Flight Center, Landsat data from the U.S. Geological Survey, and iMERG data from the Global Precipitation Mission (GPM) at NASA/GSFC. Story by Kasha Patel.

Joaninha (Southern Indian Ocean)

Mar 27, 2019 – NASA’s Aqua Satellite Keeps an “Eye” on Tropical Cyclone Joaninha

Visible imagery from NASA’s Aqua satellite showed a visible eye remained in Tropical Cyclone Joaninha is it continued moving through the central Southern Indian Ocean.

Aqua image of Joaninha
On March 27, 2019, the MODIS instrument aboard NASA’s Aqua satellite provided a visible image of Tropical Cyclone Joaninha moving through the central Southern Indian Ocean. Joaninha maintained a 15 nautical-mile wide eye. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS)

On March 27, 2019 the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Aqua satellite provided a visible image of Joaninha. Joaninha maintained its eye, and the eye was surrounded by powerful thunderstorms. Bands of thunderstorms spiraled into the center of circulation from the east.

The Joint Typhoon Warning Center or JTWC noted that animated multispectral satellite imagery showed that the ragged eye was 15 nautical miles in diameter.

At 11 a.m. EDT (1500 UTC) Tropical Cyclone Joaninha’s maximum sustained winds were near 110 knots (126 mph/204 kph). It was centered near 20.5 degrees south latitude and 67.0 degrees east longitude. That’s approximately 199 nautical miles (229 miles/369 km) east of Port Mathurin, Mauritius. Joaninha was moving to the east and is forecast to turn in a more southerly direction and begin weakening.

The Mauritius Meteorological Services (MMS) noted that there is still an active warning for Rodrigues. A High Wave warning remains in effect for Rodrigues until 10 a.m. local time on Friday, March 29. MMS’s warning noted “The intense Tropical Cyclone Joaninha is generating heavy swells of the order of 5 meters [16 feet] which are influencing the sea state around Rodrigues. Also storm surge will cause a rise in the sea water level of about 1.0 meters [3.2 feet] above the normal tides which will result in the inundation of low lying coastal areas particularly to the east, south and south-west.”

MMS strongly advised for fishermen, boaters and the public not to go out at sea and not to venture on the beaches until they are given the “all clear” from local authorities.

Joaninha is forecast to transition into a subtropical cyclone over the next several days.

For updated forecasts from the Mauritius Meteorological Services, visit: metservice.intnet.mu/

By Rob Gutro
NASA’s Goddard Space Flight Center

Joaninha (Southern Indian Ocean)

Mar. 26, 2019 – NASA Sees Tropical Cyclone Joaninha Affecting Mauritius

Visible imagery from NASA’s Terra satellite showed Tropical Cyclone Joaninha as it moved through the Southern Indian Ocean triggering warnings in the island nation of Mauritius.

Terra image of Joaninha
On March 26, 2019, the MODIS instrument aboard NASA’s Terra satellite provided a visible image of Tropical Cyclone Joaninha in the Southern Indian Ocean. Credit: NASA Worldview, Earth Observing System Data and Information System (EOSDIS)

Mauritius is an island nation, known for its beaches, lagoons and reefs. It is located to the northeast of Reunion Island.

The Mauritius Meteorological Services (MMS) issued several warnings on Joaninha. On March 26 a Strong wind and High Wave warning were in effect for Rodrigues valid until 10 a.m. local time on Wednesday, March 27, 2019.

MMS noted “The intense tropical cyclone Joaninha evolving to the east of Rodrigues is causing strong southerly winds to blow over the island. Gusts may reach 100 kph (62mph) in places. The cyclone is also generating heavy swells of the order of 5 to 7 meters (16 to 23 feet) which are influencing the sea state around Rodrigues. Also storm surge will cause a rise in the sea water level of about 1.5 meters (5 feet) above the normal tides which will result in the inundation of low lying coastal areas particularly to the east, south and south-west.”

On March 26, 2019, the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite provided a visible image of Joaninha. Joaninha had a 15 nautical-mile wide eye surrounded by powerful thunderstorms. Bands of thunderstorms spiraled into the center of circulation from the eastern quadrant.

On March 26 at 8 a.m. EDT (1200 UTC) Joaninha had maximum sustained winds near 115 knots (132 mph/213 kph). Joaninha was centered near 19.6 degrees south latitude and 65.2 degrees east longitude. That’s about 86 nautical miles (99 miles/ 159 km) east of Port Mathurin, Mauritius

Joaninha is moving through an area of warm waters, which will continue to fuel it. The Joint Typhoon Warning Center noted that the wind shear, outside winds that can affect a storm at different altitudes, was light, so it will not affect the storm on its track to the south for the next day or two.

For local updates from the MMS, visit: http://metservice.intnet.mu

By Rob Gutro
NASA’s Goddard Space Flight Center