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.