The Joint Typhoon Warning Center (JTWC) reported that the 2015 western Pacific typhoon season was one of the busiest on record, while also being the most accurate season for JTWC forecasters.
"We experienced a very strong El Nino event in 2015, which drastically influenced the development and life cycle of tropical cyclones in the western North Pacific," said Bob Falvey, JTWC's director and senior meteorologist. "Historically, the warmer ocean waters during El Nino influence tropical cyclone formation areas rather than the total number of storms in a season. This fact held true in 2015, as more tropical systems developed further east in the Pacific Ocean, which resulted in longer over-water tracks and thus more time for intensification prior to making landfall."
Typhoon season in the western North Pacific spans the entire calendar year, as tropical cyclones can and have formed during every month. As a consequence of the shift in tropical cyclone formation area, a new record for the number of tropical cyclone forecasts/warnings issued was established at 887 for 2015. This represents a 48 percent increase versus the long-term annual average of about 600.
Longer duration tropical cyclones also translated into an increased number of incidents of three or more concurrent tropical cyclones, resulting in a significant increase in operating tempo for JTWC's watch teams.
Additionally, eight tropical cyclones reached "super typhoon" intensity. A typhoon is categorized as a super typhoon when sustained wind speeds reach 130 knots; typically only three to four super typhoons occur annually in the western North Pacific.
"While there is much talk about anti-access threats in the Western Pacific associated with quiet diesel subs, anti-ship cruise missiles and ballistic missiles, the single greatest anti-access threat in that region is a super typhoon," said Rear Adm. Tim Gallaudet, commander, Naval Meteorology and Oceanography Command.
Yet, despite being one of the most active tropical cyclone seasons on record, JTWC's forecast tracks were the most accurate at all forecast lead times (24, 48, 72, 96 and 120 hours) in its 56-year history. The forecast track is the path forecasters think a tropical cyclone will travel, and the accuracy of a forecast track tends to decreases with time.
In 2015, JTWC lowered its forecast track errors below the 100, 150 and 200 nautical mile thresholds for the three, four, and five-day forecast times, respectively, marking another first for the command. These forecast track error statistics represent a 25-35 percent improvement compared to just five years ago, providing commanders with improved forecast certainty.
"The continuous improvement we have seen in our track forecasts over the last five years demonstrates a significant return on investments made in satellite technology, weather models, training and analysis/forecasting techniques," said Capt. Steven Sopko, JTWC's commanding officer. "All of the credit for our performance in 2015 goes to the dedicated team of Navy and Air Force professionals who consistently perform at an extremely high level to safeguard Department of Defense personnel and assets, afloat and ashore across the Pacific."
The Joint Typhoon Warning Center traces its origins to the aftermath of Typhoon Cobra in December 1944 when the U.S. Navy's Task Force 38 lost three ships, 150 aircraft and more than 700 Sailors while operating in the Philippine Sea. This tragic event prompted many new initiatives aimed at improving tropical cyclone analysis, tracking and forecasting.
Today, JTWC, Fleet Weather Center, San Diego (FWC-SD) and the U.S. Air Force's (USAF) 17th Operational Weather Squadron (OWS) coordinate efforts to prevent future weather-related tragedies of this magnitude. Advances in tropical cyclone reconnaissance and forecasting over the past half century equip today's commanders with more accurate and actionable information to avoid or mitigate the impacts of tropical cyclones on afloat operations and shore-based installations.
FWC-SD uses JTWC tropical cyclone forecasts to provide sortie and ship divert/route recommendations to units operating across the Pacific and Indian Ocean basins. In 2015, 65 ships were sortied and another 198 ships were diverted from their original track due to tropical cyclones and other weather-related phenomenon.
The 17th OWS provides tropical cyclone satellite reconnaissance and uses JTWC forecasts to determine impacts to U.S. installations across the Western Pacific. In 2015, 17th OWS satellite analysts generated roughly 12,800 tropical cyclone fixes.
"The western North Pacific remains the most active area on the globe for tropical cyclone activity and nearly one third of the annual global tropical cyclones form in this basin," said Falvey. "Systems develop quickly and often become some of the strongest in the world."
In November 2013, Super Typhoon Haiyan cut through the central Philippines and JTWC's forecasts provided essential information to U.S. military planners coordinating large-scale United States Pacific Command (USPACOM)-led humanitarian assistance operations to the region. Similarly, in December 2015, warnings issued for Typhoon Melor were closely monitored by senior military leaders, as the typhoon took a similar path over the Philippines.
According to the Indo Asia-Pacific rebalance outlined by the secretary of the Navy's "Cooperative Strategy for 21st Century Sea Power", 60 percent of all U.S. Navy ships and aircraft are anticipated to be postured in the region by 2020. In the future, JTWC's tropical cyclone forecasts will play an increased role in military operations.
"The western North Pacific will continue to be a region of high tropical cyclone activity for the foreseeable future, posing a significant risk to military operations as the projected force realignment into the Indo Asia-Pacific Theater unfolds," said Sopko. "I am very confident that the dedicated men and women of the Joint Typhoon Warning Center are up to the challenge of continuing its long history of outstanding service to U.S. forces operating in the USPACOM AOR."
The Joint Typhoon Warning Center was established in 1959 at the direction of Commander, U.S. Pacific Command. JTWC was originally located in Guam, but was moved to its current location at Joint Base Pearl Harbor-Hickam in 1999. JTWC is jointly manned by U.S. Navy and Air Force personnel and falls under the operational control of Commander, Task Group 80.7 (Commander, Naval Meteorology and Oceanography Command). U.S. Air Force personnel are sourced to JTWC by the 17th Operational Weather Squadron and 557th Weather Wing.
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