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Annual Tropical Cyclone Report 2007

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Executive Summary

The Annual Tropical Cyclone Report is prepared by the staff of the Joint Typhoon Warning Center (JTWC), a combined Air Force/Navy organization operating under the command of the Commanding Officer, U.S. Naval Maritime Forecast Center/Joint Typhoon Warning Center (NMFC/JTWC), Pearl Harbor, Hawaii. JTWC was established in April 1959 when USCINCPAC directed USCINCPACFLT to provide a single tropical cyclone warning center for the western North Pacific region. The operations of JTWC are guided by USPACOM Instruction 0539.1.

This edition contains yet another modification to the content. While the standard tropical cyclone summaries by basin remain the core of the document, this year more detailed reviews of operationally or meteorologically significant tropical cyclones are included. The primary reason for this change is to document significant challenges and/or shortfalls in the tropical cyclone warning system to serve as a focal point for research and development efforts.

Year 2007 continued the below normal activity in the western North Pacific, with 27 tropical cyclones occurring compared to an average of 31. This below average activity trend is also apparent in the South Indian Ocean and South Pacific, with 24 cyclones compared to an average of 27. The North Indian Ocean was near normal with 6 cyclones compared to an average of 5. Of significance in the North Indian Ocean was TC 02A, Gonu, and TC 06B, Sidr. Gonu formed in the south central Arabian Sea and tracked west-northwestward into the Straights of Hormuz, reaching a peak intensity of 145 knots before making a rare landfall in Iran. Sidr, which formed in the central Bay of Bengal, had large societal impacts as it tracked northward and made landfall in Bangladesh after reaching peak intensity of 140 knots. Other significant cyclones include Super Typhoon 17W, Krosa, and Typhoon 23W, Hagabis. Krosa was significant because is underwent explosive intensification of 40 knots in 24 hours for two consecutive days, strengthening from a 25 knot tropical depression to a 100 knot typhoon. Hagabis was significant due to its unforecast turn to the east by JTWC and most of the numerical models.

Weather satellite data continued to be the mainstay for the tropical cyclone reconnaissance mission at JTWC.
Satellite analysts exploited a wide variety of conventional and microwave satellite data to produce over 8,600 position and intensity estimates. The USAF primary weather satellite direct readout system, Mark IVB, was threatened to be terminated due to funding issues, but thanks to the hard work by satellite experts at JTWC to show significant warfighter impacts, the Director of Weather decided to continue the program.

Advances in the numerical models and the careful use of the multi-model consensus, CONW, contributed to another record forecast year, whereby JTWC met or exceeded the USCINCPAC goal of 50 nm (24 hours), 100 nm (48 hours), 150 nm (72 hours), 200 nm (96 hours), and 250 nm (120 hours). 2007, however, was not without challenges for JTWC with individual cyclones such as STY 17W (Krosa) and TY 23W (Hagibis) presenting significant forecast challenges, with either intricate tracks and/or rapid changes in intensity.

Subsequently for 2008, while will we continue our efforts to improve our track forecasting, we will also refocus efforts to improve our intensity forecast capability. Intensity and structure continue to be a significant forecast challenges at other warning centers and was a major theme at the 62nd Interdepartmental Hurricane Conference in Charleston SC in March 2008.

Continuing dialogue and interaction with TC forecast support and research organizations such as the Fleet Numerical Meteorology and Oceanography Center, Naval Research Laboratory, Monterey, Naval Post Graduate School, and the Office of Naval Research for continued development of numerical TC models and forecast aids, including improvements to the Navy’s version of the Geophysical Fluid Dynamics Lab (GFDL) mesoscale hurricane model (GFDN) and implementation of the Hurricane Weather and Research Forecast model (H-WRF) is expected to improve complicated scenario forecast capability.

Behind all these efforts are people - the dedicated men and women at JTWC, including the entire N6 Department for their outstanding IT support with special thanks to Mr. Angelo Alvarez for his tireless efforts to keep the computers, communications and numerous websites working. Thanks also to the Navy and Air Force personnel across the Pacific who support our reconnaissance and forecasting functions, the researchers and programmers helping develop our knowledge base and tool kit to better forecast tropical cyclones. Without an integrated effort, the challenging task of locating and forecasting the movement and structure of tropical cyclones would be considerably more difficult. That entire TC community will continue to focus all available science and technology on providing the best possible support to you, our customers, who stand in harm’s way.