Briana Luthman, Ryan Truchelut, and Robert E. Hart Young Scholars Program, Florida State University Background In recent decades the technology used to classify tropical cyclones has improved, specifically in the use of satellites. This has created a bias in the trends of tropical cyclones. It makes it seem as if there has been a dramatic increase in the number of TCs over the past few decades, when in reality, they may have just been undetected. This has created difficulties in determining long-term trends of TC activity. This needs to be improved to better predict future TCs. Methodology Truchelut and Hart 2011 was a successful study that identified missing TCs using a reanalysis. But the study only applied to the Atlantic Basin for because it was a completely manual technique. Some major improvements were then made to the study, such as the use of a completely automated technique for identifying candidate events. This proved to be much faster, and this study was able to classify all basins back to This project was focused on the Western Pacific Basin from 1930 to This study also uses the automated technique to speed up the process of classifying the events. Truchelut and Hart 2011 used NHC criteria (Landsea et al., 2008) to classify the events, so this was included in this study as well. This involves classifying the candidate events into three categories. Type three is a possible missing TC, while type one is not a missing TC. Type two is the catch-all category, which includes events that have limited observations or dont meet all the criteria. See center panels for more information. Candidate Event Classification Criteria Summary and References The research resulted in about five possible missing TCs per year. It was found that most of the candidate events were ambiguous and had to be classified as type two. The automated technique was producing about thirty candidate events per year. The average season in the Western Pacific during this satellite era is tropical storms. Finding only five TCs per year suggests that this process can't find enough substantial cases in the Western Pacific to complete the record with something approximating average before This study shows that the automated technique can find some possible missing TCs. Even though there are not as many events as a normal season, it still is an efficient way to improve the historical record of TCs. Works Cited Landsea, C. W., et al 2008: A Reanalysis of the Atlantic Hurricane Database. J.Climate. Truchelut, R. E., and R. E. Hart (2011), Quantifying the possible existence of undocumented Atlantic warmcore cyclones in NOAA/CIRES 20th Century Reanalysis data, Geophys. Res. Lett.,38 Truchelut, Ryan and Robert Hart. "Global Identification of Previously Undetected Tropical Cyclone Candidates in NOAA/CIRES 20th Century Reanalysis Data." 30th Conference on Hurricanes and Tropical Meteorology, Ponte Vedra Beach, FL. 16 April Conference presentation. Observational Verification of Previously Unidentified Tropical Cyclones in the Western Pacific Basin Methodology, continued One drawback of the automated technique is that there are a large amount of events that have yet to be identified. The reanalysis of these events will take a large amount of time. This study focused on the Western Pacific basin because it is the most active for TCs. Also, this basin had no records prior to Within the last few decades the number of events in the Western Pacific Basin have dramatically increased with a large amount in the 1930s, as shown in Figure 5. TYPE 3 In order to be classified as a type three (Figure 3) there must be a closed circulation. There must also be two observations of either winds greater than 33 knots or pressures less than 1002 millibars close to the center of the event. The event cant be frontal in nature, and the anomalies have to be fairly symmetrical around the estimated circulation center. TYPE 1 In order to be classified as a type one (Figure 1) there must be a sufficient amount of observations to reasonably conclude that there is no surface circulation present. A closed circulation involves winds from the north, south, east, and west at nearly the same observation time. If a circulation exists, there cannot be any winds greater than 33 knots or pressures below 1002 mb. Additionally, if the event is clearly frontal or non-tropical, then it is a type 1. Type 2 Type two (Figure 2) includes all events that cannot be classified as type one or type three. These events usually have very limited observations. This is especially important when there is a significant warm anomaly. This type also includes events that have closed circulation but no low pressures / strong winds or vice versa. 24 total events 34 total events 18 total events 11 total events Number of Events Type Figure 1 This is a type 1 example from April 16 th, Figure 2 This is a type 2 example from March 31 st, Figure 3 This is a type 3 example from October 9 th, Figure 4 This sample observation describes the sets of four numbers located on the candidate event study maps. Figure 5 Trends in the number of candidate events for various ocean basins Results for the Reanalysis of TCs in Western Pacific Basin