NASA Measures Winds in Tropical Cyclone Victor

Victor (Southern Pacific Ocean)

NASA Measures Winds in Tropical Cyclone Victor

NASA's RapidScat instrument found the strongest winds in Tropical Cyclone Victor were occurring south of its center on January 20. Imagery from NOAA's GOES-West satellite revealed that Victor still maintained hurricane-strength and an eye.

NOAA's GOES-West satellite captured this image of Tropical Cyclone Victor in the South Pacific on Jan. 20 at 1500 UTC (10 a.m. EST).

Credits: NASA/NOAA GOES Project

As Victor continues moving in a southerly direction a gale warning was posted for the island country of Niue. Tonga is located to the west and the Cook Islands to the east.

RapidScat is an instrument on the International Space Station that measures surface winds over oceans. On Jan. 20 at 2 a.m. EST, RapidScat saw Tropical Cyclone Victor's strongest winds south of the center at 34 meters per second (76 mph/122 kph).

On Jan. 20 at 2 a.m. EST, RapidScat saw Tropical Cyclone Victor's strongest winds (red) south of the center at 34 meters per second (76 mph/122 kph).

Credits: NASA JPL, Doug Tyler

At 0900 UTC (4 a.m. EST), Tropical Cyclone Victor had maximum sustained winds near 65 knots (75 mph/120.4 kph) so it was still maintaining status as a Category 1 hurricane on the Saffir-Simpson Scale. It was centered near 21.6 degrees south latitude and 168.9 degrees west longitude, about 360 nautical miles east of Tonga. Victor was moving to the west-southwest at 4 knots (4.6 mph/7.4 kph).

NOAA's GOES-West satellite captured an image of Tropical Cyclone Victor in the South Pacific on Jan. 20 at 1500 UTC (10 a.m. EST) that showed the storm maintained an eye, and had powerful bands of thunderstorms around the center.

Forecasters at the Joint Typhoon Warning Center expect Victor to weaken steadily over the next few days, before turning to the south and becoming extra-tropical.

Rob Gutro
NASA’s Goddard Space Flight Center

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Jan. 19, 2016 - NASA Sees Wide-Eyed Tropical Cyclone Victor

NASA satellites and instruments have been monitoring Tropical Cyclone Victor, a hurricane in the South Pacific Ocean with a large eye. NASA's Aqua satellite, NASA-NOAA's Suomi NPP satellite and the RapidScat instrument aboard the International Space Station have all gathered data on the storm.

On Jan. 16, 2016 (left) RapidScat measured Victor's strongest winds near 30 meters per second (67 mph/108 kph) in all quadrants except the western side. On Jan. 18 (right) slightly weaker. By Jan. 18 strongest winds had increased to 36 mps/80.5 mph/129.6 kph in all but the northern side.

Credits: NASA JPL, Doug Tyler

The RapidScat instrument that flies aboard the International Space Station measured Tropical Cyclone Victor's wind speed at the surface. Surface wind speed is always lower than speeds at higher altitude.

RapidScat is an important tool for meteorologists, because maximum sustained winds are not always equally distributed in a hurricane or tropical storm. RapidScat sustained wind data shows forecasters the location of the strongest winds in different quadrants of a storm. On Jan. 16 RapidScat measured Victor's strongest winds near 30 meters per second (67 mph/108 kph) in all quadrants except the western side, which was slightly weaker. By Jan. 18, the storm was hurricane-strength and those strongest winds had increased to 36 meters per second (80.5 mph/129.6 kph) and shifted to the western, southern and eastern quadrants of the storm.

On Jan. 18 at 00:45 UTC (Jan. 17 at 9:45 p.m. EST) the MODIS instrument aboard NASA's Aqua satellite saw Tropical Cyclone Victor in the South Pacific Ocean.

Credits: NASA Goddard MODIS Rapid Response

On Jan. 18 at 00:45 UTC (Jan. 17 at 9:45 p.m. EST) the MODIS or Moderate Resolution Imaging Spectroradiometer instrument aboard NASA's Aqua satellite provided a visible light image of Tropical Cyclone Victor. At that time, Victor's eye was almost due east of the Cook Islands.

On Jan. 19 at 01:00 UTC the VIIRS instrument aboard NASA-NOAA's Suomi NPP captured this image of a wide-eyed Tropical Cyclone Victor in the South Pacific Ocean.

Credits: NASA Goddard Rapid Response

By Jan. 19 at 01:00 UTC when NASA-NOAA's Suomi NPP satellite passed over Victor, the eye had moved southeast of the Cook Islands. The VIIRS instrument aboard Suomi NPP captured another visible image of the wide-eyed hurricane and observed that the eye was more open than it was during the time the Aqua satellite passed overhead. The eye was about 35 nautical miles (40 miles/64 km) wide. The Suomi image showed strong bands of thunderstorms wrapping into that ragged eye.

Later in the day at 0900 UTC (4 a.m. EST), Victor's maximum sustained winds were near 80 knots (92 mph/ 148.2 kph). Victor was moving to the southwest at 6 knots (6.9 mph/11.1 kph). It was centered near 20.9 degrees south latitude and 167.3 degrees west longitude, about 410 nautical miles west of Rarotonga, Cook Islands.

Forecasters at the Joint Typhoon Warning Center expect Victor to continue moving in a west-southwesterly direction while slowly weakening over the next couple of days. By. Jan. 22, Victor is forecast to turn to the south and will have weakened to tropical storm status and transition into an extra-tropical storm.

Rob Gutro
NASA's Goddard Space Flight Center