Attachments
Executive Summary
The Annual Tropical Cyclone Report (ATCR) is prepared by the staff of the Joint Typhoon Warning Center (JTWC), a jointly manned United States Air Force/Navy organization under the operational command of the Commanding Officer, Joint Typhoon Warning Center.
The JTWC was established on 1 May 1959 when the Joint Chiefs of Staff directed Commander-in- Chief, US Pacific Command (USCINCPAC) to provide a single tropical cyclone warning center for the western North Pacific region. USCINCPAC delegated the tropical cyclone forecast and warning mission to Commander, Pacific Fleet. A subsequent USCINCPAC directive further tasked Commander, Pacific Air Force to provide for tropical cyclone (TC) reconnaissance support to the JTWC. Currently, JTWC operations are guided by USPACOM Instruction 0539.1 and Pacific Air Forces Instruction 15-101.
This edition of the ATCR documents the 2015 TC season and details operationally or meteorologically significant cyclones noted within the JTWC Area of Responsibility. Details are provided to describe either significant challenges and/or shortfalls in the TC warning system and to serve as a focal point for future research and development efforts. Also included are tropical cyclone reconnaissance statistics and a summary of tropical cyclone research or tactics, techniques and procedure (TTP) development in which members of JTWC were involved.
The major event in the tropics during 2015 was a strong El Nino, with sea surface temperature anomalies reaching +3 degrees Celsius above normal in December with the 3- month running mean anomaly remaining above +2 degrees Celsius from September 2015 to March 2016. The western North Pacific Ocean returned to near normal tropical cyclone activity, with 29 TCs forming in basin, compared to the long term average of 31. Two additional TCs formed in the Central North Pacific and subsequently crossed into the basin. Additionally, 9 of the 29 cyclones attained super typhoon intensity. As expected, long-lived El Nino conditions shifted the mean TC genesis region eastward, causing major DoD installations to experience significant cyclone impacts. Okinawa was impacted by 3 typhoons, Guam and the Commonwealth of the Northern Mariana Islands experienced impacts from 7 cyclones and mainland Japan had 3 cyclones make landfall.
Southern Hemisphere activity remained below the long term average of 28, with 16 cyclones in the south Indian Ocean / western Australia region and 9 in the south Pacific / eastern Australia region. Tropical Cyclone Olwyn (19S) made a direct impact on the USAF solar observatory at Learmonth Australia. Tropical Cyclone Pam (17P) reached a peak intensity of 150 knots as it tracked through the island nation of Vanuatu, resulting in catastrophic damage. The north Indian Ocean experienced normal activity of five cyclones, with 4 in the Arabian Sea and 1 in the Bay of Bengal. The most significant cyclones in the north Indian Ocean were Tropical Cyclone 04A (Chapala) and 05A (Megh) in the Arabian Sea, reaching peak intensities of 130 knots and 110 knots, respectively. Both cyclones followed nearly the same westerly track, passing near or over Socotra before making landfall in central Yemen.
Meteorological satellite data remained the mainstay of the TC reconnaissance mission in the support of the JTWC. Satellite analysts administratively assigned to the 17th Operational Weather Squadron, exploited a wide variety of conventional and microwave satellite data to produce 12,208 position and intensity estimates (fixes), primarily using the USAF Mark IVB and the USN FMQ-17 direct readout systems. Geo-located satellite imagery overlays available via the Automated Tropical Cyclone Forecast (ATCF) system from Fleet Numerical Meteorology and Oceanography Center and the Naval Research Laboratory-Monterey, were also used by JTWC to make TC fixes. This year, JTWC satellite analysts expanded the use of active and passive scatterometer data and began adding 35 knot wind structure information (radii) by quadrant to the position and maximum observed wind speed entries. This effort will assist in creating a more accurate initial state of tropical cyclones for use in numerical model initialization and wind radii forecasting.
The eastward shift in the mean genesis formation region led to numerous long-lived tropical cyclones. As a result, JTWC issued a likely record-breaking 1,193 tropical cyclone warnings throughout its area of responsibility. Additionally, forecast operations experienced two unprecedented periods of four concurrent tropical cyclones. Despite these challenges, JTWC western North Pacific mean forecast errors set new records for all lead times, with day 3 and day 5 errors below 100 nm and 200 nm, respectively, for the first time ever. Behind all these efforts and accomplishments are the dedicated team of men and women, military and civilian at JTWC. Special thanks to the entire JTWC N6 Department for their continued outstanding IT support and the administrative and budget staff who worked tirelessly to ensure JTWC had the necessary resources to get the mission done in extremely volatile financial times.
A Special thanks also to: FNMOC for their operational data and modeling support; the NRLMRY and ONR for their dedicated TC research; the National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite, Data, and Information Service (NESDIS) for satellite reconnaissance support; Dr. John Knaff, Dr. Mark DeMaria, and Mr. Chris Velden for their continuing efforts to exploit remote sensing technologies in new and innovative ways; Mr. Charles R. “Buck” Sampson, Ms. Ann Schrader, and Mr. Mike Frost for their outstanding support and continued development of the ATCF system.