The RapidScat instrument that flies aboard the International Space
Station (ISS) provided data about Tropical Cyclone Joalane's surface
winds that showed how the strongest sustained winds consolidated as the
tropical cyclone intensified and developed an eye. As of April 9,
warnings were in effect at Rodrigues Island in the Southern Indian Ocean
as Joalane approached.
RapidScat measured the surface winds within Tropical Cyclone Joalane
late on April 7 and on April 8, revealing that the strongest winds
consolidated over a 24 hour period. RapidScat measured Joalane's winds
on April 7 from 23:19 to 00:52 (7:19 p.m. to 8:52 p.m. EDT) and April 8
from 10:07 to 11:40 UTC (6:07 p.m. to 11:40 p.m. EDT).
The strongest sustained winds up reached up to 30 meters per second
(67.1 mph/108 kph). During the earlier pass on April 7, those strongest
wind speeds were north and east of the developing eye, and extending
south and east in a wide band of thunderstorms. On April 8, the
strongest surface winds became more concentrated and circled the entire
center (which was an eye at that time). Sustained winds of 30 meters per
second (67.1 mph/108 kph) were also seen in occurring bands of
thunderstorms south and east of the center. The data was generated into
images at NASA's Jet Propulsion Laboratory in Pasadena, California.
On April 9 at 05:50 UTC (1:50 a.m. EDT), the Moderate Resolution
Imaging Spectroradiometer or MODIS instrument aboard NASA's Aqua
Satellite captured visible-light data of Tropical Cyclone Joalane. That
data was made into an image by the MODIS Rapid Response Team at NASA's
Goddard Space Flight Center in Greenbelt, Maryland. The image showed
banding of thunderstorms in the southwestern and northeastern quadrants
of the storm, wrapping into the storm's center. The eye of the storm now
just 7 nautical miles (8.0 miles/12.9 km) wide according to microwave
data was obscured by clouds in the visible MODIS imagery.
A Class I tropical cyclone warning was posted on April 9 at
Rodrigues. For updated forecasts for Rodrigues Island, visit the
Mauritius Meteorological Services website at: http://metservice.intnet.mu/.
By 1500 UTC (11 a.m. EDT), Joalane's maximum sustained winds were
still at 80 knots (92 mph/148.2 kph), just where they were 24 hours
before. Joalane is still a strong Category 1 hurricane on the
Saffir-Simpson hurricane wind scale. Joalane's center was near 17.0
south latitude and 65.7 east longitude, about 513 nautical miles (590.3
miles/ 950.1 km) east-northeast of Port Louis, Mauritius. As it was 24
hours before, Joalane was still moving at 6 knots (6.9 mph/11.1 kph) but
shifted its path from the south-southeast to due south.
Joalane is moving south into an area of cooler sea surface
temperatures and increased vertical wind shear. It is expected to start
weakening in a day while transitioning into an extra-tropical storm.
Rob Gutro
NASA's Goddard Space Flight Center
Weather and Disaster related posts relating to the Western- and Southern Cape Areas. Also some interesting worldwide weather,disaster and space weather/mission posts at times.
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