April 06, 2009
Tropical Cyclone Lin Going Out Kicking South of the Fiji Islands
Hurricane Season 2009: Lin (Southern Pacific Ocean)
Tropical Cyclone Lin was an area of low pressure in the Fiji islands on April 3, and the next day strengthened into a tropical storm. Over the weekend of April 4 and 5, it wove its way southeast through the Fiji islands and is now in open waters in the Southern Pacific Ocean. Lin is now transitioning into an extra-tropical storm and kicking up waves in open waters.
Tropical Storm warnings that were in effect for the Fiji Islands have been dropped.
The second and last bulletin on Tropical Cyclone Lin was issued early on April 6 by the U.S. Navy's Joint Typhoon Warning Center, when Lin was reported 380 miles east-southeast of Suva, Fiji, near 19.7 degrees south and 176.2 degrees west. Lin had sustained winds near 45 knots (52 mph) and it was weakening. It was moving south near 13 knots (15 mph) while still kick up waves almost 15 feet high on its way out into the open ocean.
The Atmospheric Infrared Sounder (AIRS) is an instrument aboard NASA's Aqua satellite and it captured an infrared image of Lin on April 6. The AIRS image clearly shows a large temperature difference between Lin's cloud tops and the warm surfaces of the Earth (land and water).
In this image, the orange temperatures are 80F (300 degrees Kelvin) or warmer. Lin'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.
What Does "Conversion to an Extratropical Storm" Mean?
A conversion to "extratropical" status means that the area of low pressure (known as Lin in this case) eventually loses its warm core and becomes a cold-core system. During the time it is becoming extratropical the cyclone's primary energy source changes from the release of latent heat from condensation (from thunderstorms near the storm's center) to baroclinic (temperature and air pressure) processes. When a cyclone becomes extratropical it will usually connect with nearby fronts and or troughs (extended areas of low pressure) consistent with a baroclinic (pressure) system. When that happens it appears the system grows larger while the core weakens.
For updated forecasts from the Fiji Meteorological Service, visit: http://www.met.gov.fj/index.php
Rob Gutro, NASA's Goddard Space Flight Center