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Hurricane Season 2009: Joni (Southern Pacific Ocean)
Mar. 13, 2009

AIRS image of Joni on March 13, 2009> Click for larger image
Credit: NASA JPL, Ed Olsen
Environment Being Unkind to Cyclone Joni

Tropical Cyclone Joni is a fighter. Forecasters had almost written her off the day she came into being, but she's held her own for 48 hours and will likely keep together one more day. She's now running into an unkind environment: strong wind shear and colder sea surface temperatures. Those are two factors that can kill a tropical storm.

Joni isn't threatening any land masses, swirling around in the open waters of the southwestern Pacific Ocean. In fact, the nearest land mass is the island of Rarotonga, which is 390 miles north of Joni's location. Joni is near 27.2 degrees south and 159.2 degrees west. Joni is a tropical storm with sustained winds near 55 knots (63 mph) and is zipping along in open waters in a southern direction near 16 knots (18 mph). Tropical storm force winds extent out to 110 miles from Joni's center and they're kicking up 12 foot high waves.

The environment is about become very unkind to Joni. Stronger vertical wind shear (winds blowing at different levels of that atmosphere in different directions that can shear a storm apart) will also bring in drier air. Dry air will zap all the moist air and convection (rapidly rising air) that helps build thunderstorms that keep a storm going. In addition, sea surface temperatures continue to drop below 80 degrees Fahrenheit (which is the temperature necessary to maintain a storm's strength) the further Joni ventures southward.

NASA's Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured this visible image of Joni on Mar. 12 at 11:29 UTC (7:29 a.m. EDT). Joni is the round area in blue and purple located in the bottom left corner of this satellite image.

The infrared image clearly shows a large temperature difference between Joni's cloud-tops and the warm ocean temperatures. In this image, the orange temperatures are 80F (300 degrees Kelvin) or warmer. Joni's lowest temperatures (in purple) are associated with high, cold cloud tops. Those temperatures are as cold as or colder than 220 degrees Kelvin or minus 63 degrees Fahrenheit (F). The blue areas are around 240 degrees Kelvin, or minus 27F.

AIRS generates infrared, microwave and visible images. The AIRS infrared data creates an accurate 3-D map of atmospheric temperature, water vapor and clouds, all of which are helpful to forecasters.

Text credit: Rob Gutro/NASA Goddard Space Flight Center

Mar. 11, 2009

Joni Joins the Cyclone Count

AIRS visible image of Tropical Cylone Joni on March 11, 2009> Click for larger image
Credit: NASA/JPL
The Southwestern Pacific Ocean just gave birth to another tropical cyclone today: Joni. Joni, also designated cyclone 20P, is located about 95 miles east of the Island of Rarotonga.

Rarotonga is the most populous island in a group of islands known as the Cook Islands. Rarotonga is 14,750 feet above the ocean floor and is only 20 miles in circumference, with a total land area of 26 miles. The Cook Islands consist of fifteen small islands in the South Pacific Ocean.

On Wed. Mar. 11, Joni's sustained winds were near 35 knots (42 mph), and she was moving south at 6 knots (7 mph). Joni's center was located near 21.2 degrees south and 158.1 degrees west. Joni is expected to only survive two days, due to adverse atmospheric conditions.

The main area threatened by Joni is Rarotonga. The island can expect south-to-southwest sustained winds up to 25 knots (28 mph), gusting 40 knots (46 mph). Joni will also bring periods of occasionally heavy rain with thunderstorms and cause some low lying areas to flood. Other islands that will be affected by gusty winds include: Manuae, Mauke, Mangaia and Aitutaki and Palmerston.

NASA's Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite captured this visible image of Joni on Mar. 10 at 23:53 UTC (7:53 p.m. EDT). The satellite image shows that Joni doesn't have a signature circular shape, indicating that the storm is poorly organized.

Text credit: Rob Gutro/NASA Goddard Space Flight Center