Ivy first formed into a tropical storm at 18Z on the 22nd of February 2004 midway between Fiji to the east and Vanuatu to the west. The storm moved northwest for a day and gained strength becoming a minimal Category 1 cyclone at 18Z on the 23rd. Ivy then recurved toward the southwest on the 24th and continued to intensify threatening the Vanuatu islands. By 06Z on the 25th Ivy was bearing down on the island of Malakula in central Vanuatu with maximum sustained winds estimated near 90 knots (104 mph) by the Joint Typhoon Warning Center.
The Tropical Rainfall Measuring Mission (TRMM) satellite captured these unique images of Cyclone Ivy as it approached Vanuatu. The top image was taken at 05:48 UTC on 24 February 2004. It shows the horizontal distribution of rain rates observed by the TRMM Precipitation Radar (PR) in the center swath and the TRMM Microwave Imager (TMI) in the outer swath. The rain rates are overlaid on infrared (IR) data from the TRMM Visible Infrared Scanner (VIRS). At this time, Ivy was estimated to have sustained winds of 70 knots (83 mph). TRMM shows that Ivy is still in the process of organizing with no clear eye present yet. However, a substantial area of intense rainfall (darker reds) is detected near the center of the circulation. As hurricanes depend on the heat released from the condensation of water vapor to fuel their circulation, the presence of these rainrates near the center of the storm where they are the most effective, indicates the potential for further strengthening.
The bottom image shows Ivy almost a day and half later at 14:33 UTC on the 25th just before hitting the island of Malakula. The winds are now up to 90 knots (104 mph), and TRMM shows that Ivy now has a well-developed, symmetrical eye that is associated with mature tropical cyclones. The eye is surrounded by mainly moderate rainrates (green areas) with the most intense rainrates (dark reds) present in rainbands off to the east.
TRMM is a joint mission between NASA and the Japanese space agency JAXA.
Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).
