Tag: Joaninha 2019

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.

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

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.

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

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.

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

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.

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

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.

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

Mar. 25, 2019 – NASA Finds Heavy Rainfall around Tropical Cyclone Joaninha’s Center

NASA calculated the rainfall rates occurring in Tropical Cyclone Joaninha as it moved through the open waters of the Southern Indian Ocean.

Data from the Global Precipitation Measurement mission (GPM) is used to develop rainfall total estimations and provided a look at rain Joaninha was generating.

GPM is a joint mission between NASA and the Japan Aerospace Exploration Agency, JAXA. GPM also utilizes a constellation of other satellites to provide a global analysis of precipitation that are used in the IMERG calculation. NASA’s Integrated Multi-satellitE Retrievals for GPM (IMERG) data were used to estimate the rate in which rain was falling in Joaninha on March 24.  Rainfall rates were often greater than 0.75 inches (19 mm) per hour around the center.

What Is IMERG? 

At NASA’s Goddard Space Flight Center in Greenbelt, Maryland, those data are incorporated into NASA’s IMERG or Integrated Multi-satellitE Retrievals for GPM. IMERG is used to estimate precipitation from a combination of passive microwave sensors, including the Global Precipitation Measurement (GPM) mission’s core satellite’s GMI microwave sensor and geostationary IR (infrared) data. IMERG real-time data are generated by NASA’s Precipitation Processing System every half hour and are normally available within six hours.

IMERG creates a merged precipitation product from the GPM constellation of satellites. These satellites include DMSPs from the U.S. Department of Defense, GCOM-W from the Japan Aerospace Exploration Agency (JAXA), Megha-Tropiques from the Centre National D’etudies Spatiales (CNES) and Indian Space Research Organization (ISRO), NOAA series from the National Oceanic and Atmospheric Administration (NOAA), Suomi-NPP from NOAA-NASA, and MetOps from the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).  All of the instruments (radiometers) onboard the constellation partners are inter-calibrated with information from the GPM Core Observatory’s GPM Microwave Imager (GMI) and Dual-frequency Precipitation Radar (DPR).

Tropical Cyclone Joaninha’s Status

On March 25 at 11 a.m. EDT (1500 UTC), Joaninha had maximum sustained winds near 105 knots (121 mph/195 kph). It was centered near 18.3 degrees south latitude and 62.9 degrees east longitude, about 335 miles east-northeast of Port Louis, Mauritius. Joaninha was moving to the southeast and is expected to continue in that general direction.

A tropical cyclone warning class 4 remains in force at Rodrigues. At 11 a.m. EDT (1500 UTC) wind gusts of 87 knots (100 mph/161 kph) were observed, which will increase as the cyclone passes.

The Joint Typhoon Warning Center forecast expects Joaninha to continue to move southeast, while intensifying to 110 knots (126 mph/204 kph) by March 26, as it passes close to Rodrigues Island. After 3 days, the cyclone will start to weaken as conditions deteriorate.

By Rob Gutro
NASA’s Goddard Space Flight Center

March 22, 2019 – NASA Catches Development of Tropical Cyclone Joaninha

Visible imagery from NASA’s Terra satellite showed Tropical Cyclone Joaninha in the Southern Indian Ocean, far to the east of Madagascar.

On March 22 the Moderate Resolution Imaging Spectroradiometer or MODIS instrument aboard NASA’s Terra satellite provided a visible image of Joaninha soon after it developed. Born as Tropical Depression 22S, it quickly intensified into a tropical storm and was renamed Joaninha. Convective (rising air that consolidates into clouds and storms) bands of thunderstorms spiraled into the center of circulation from the north and east. The center of circulation was obscured by high clouds.

At 11 a.m. EDT on March 22, 2019, maximum sustained winds near Joaninha’s center were near 46 mph (40 knots/74 kph). Joaninha was centered near 15.0 degrees south latitude and 62.4 degrees east longitude. That’s about 760 nautical miles southwest of Diego Garcia in the Central Indian Ocean. Diego García is an atoll, located just south of the equator.

Joaninha is forecast to move south, later southeast, while continuing to intensify. The Joint Typhoon Warning Center or JTWC expects Joaninha’s sustained winds to peak at 115 mph (100 knots /185 kph). The storm is forecast to pass far to the east of Mauritius and La Reunion Island. After four days, at the tropical cyclone will start to weaken as conditions deteriorate.

By Rob Gutro
NASA’s Goddard Space Flight Center, Greenbelt, Md.