4B.2 A COMPARISON OF TYPHOON BEST-TRACK DATA IN THE WESTERN NORTH PACIFIC: IRRECONCILABLE DIFFERENCES Mark A Lander1, University of Guam Global warming has taken on major increase in the average intensity of political ramifications, and many world hurricanes. While not every tropical leaders and other institutions claim it to cyclone is expected to have its intensity be one of the greatest threats to modern boosted in a warmer world, there is human civilization. In general, warming theoretical support for the notion that of the planet is considered to be there will be an increase in what is dangerous, even catastrophic. The known as the Maximum Potential greatest harm is not so much from Intensity (MPI). Since wind power rises warmer temperatures per se (although in proportion to the cube of the wind recent deadly heat waves have been speed, a small increase of wind speed in attributed to global warming), but from a high-end hurricane could have the effects of warmer temperatures on magnified consequences. Increasing a such things as the mean sea level, the high-end 150 mph CAT 4 hurricane by distribution of insects and other macro only 10 mph to a minimal 160 mph CAT and microbial pests, and changes in the 5 hurricane yields a wind power in the spatial distribution, annual number, and latter that is 21% higher than in the intensity of the world’s tropical former. cyclones. While the North Atlantic basin may When the number of hurricanes have entered an active period of more experienced in the North Atlantic TCs and more intense TCs, it is not so jumped dramatically in 1995, and clear that the rest of the globe has done remained generally much above average so. The world’s other TC basins: the in the years since then, global warming western North Pacific, the eastern North was automatically suspected to be aiding Pacific, the North Indian Ocean, the and abetting this change. The TC South Indian Ocean, and the South community split into two camps: (1) Pacific Ocean seem to be behaving as those who saw the increased Atlantic usual, and in the past several years, have hurricane activity as part of a natural been relatively quiet. There are some inter-decadal oscillation in the numbers statistics in these other global basins that of Atlantic hurricanes, and (2) those who have shown decreased activity in the viewed the increase in Atlantic hurricane most recent decade. At the time of this activity to be an artifact of rising global writing (August 2007), the entire temperatures. Not only has the number Southern Hemisphere had just finished a of Atlantic hurricanes been linked by lack-luster season with fewer than some to global warming, in addition, average number of TCs, and the globe theoretical results show that in a warmer had experienced a record for the longest world one might expect to see a small time period with no active TC. _______________________________ Oddly (and probably not widely Corresponding Author Address: Mark Lander known), only the North Atlantic Ocean UOG/WERI UOG Station Mangilao, Guam 96923 basin is currently having an over- email: [email protected] abundance of TCs. The 28 named TCs of 2005 broke a long-standing record for It is the thesis of this presentation that the highest annual TC count. The SST this effort will prove to be futile. The has gone up in all of the ocean basins by differences between these agency’s approximately 0.5° C over the past typhoon best-track data sets have several decades. During the prolific irreconcilable differences. Perhaps the 2005 hurricane season in the North creation of an independent data set, such Atlantic, the SST across much of tropics as the one produced by Kossin (2007) is of that basin was at an all-time historical the only way to examine trends in high. In a recent paper, Webster et al. western North Pacific tropical cyclone (2005) claim that there are already activity. observed increases in the number of very There are many changes over time in intense tropical cyclones in most of the the way that TCs were observed, global TC basins. The release of W2005 reconnaissance aircraft have come and caused an immediate firestorm in the gone from the western North Pacific, tropical cyclone community. Some of many classes of meteorological satellites the TC data sets do indeed show an entered and exited, and image increase in the proportion among all TCs acquisition technology changed over of CAT 4 and CAT 5 cyclones. The time from low-resolution, few-times-per- strongest rebuttal to the findings of day images from low earth orbit to a W2005 came from the community of suite of high-resolution imagery those researchers and forecasters with available from low-earth orbit and from great depth of knowledge in the geosynchronous orbit with continuous development of the TC best track data coverage. A steady increase in available sets. Such individuals claimed that the frequency bands (active and passive best track data sets were of insufficient microwave imagers, multi-channel quality to derive meaningful information infrared, and remotely retrieved ocean on secular trends, or that there were surface winds) has also occurred. inherent biases in the record so as to The U.S. Hurricane Research Division negate the statistical significance of the (HRD) is well underway in a project to findings of W2005. In this presentation, revise the Atlantic basin hurricane the focus will be the TC record of the database (or HURDAT). HURDAT is western North Pacific. It will be shown the official record of tropical storms and that the best track data sets of the two hurricanes for the Atlantic Ocean, Gulf primary agencies responsible for basin- of Mexico and Caribbean Sea, including wide TC coverage — the Joint Typhoon those that have made landfall in the Warning Center (JTWC) and the Japan United States. This database is utilized Meteorological Agency (JMA) — are so for a wide variety of purposes: setting of incompatible as to call into question the appropriate building codes for coastal utility of this data for climate studies. zones, risk assessment for emergency Many have suggested adjustments be managers, analysis of potential losses for made for the procedural differences insurance and business interests, between the JMA and the JTWC so as to intensity forecasting techniques, reconcile the discrepancies in their best- verification of official and model track data (e.g., one-minute VS ten- predictions of track and intensity, minute wind averages and different seasonal forecasting, and climate change conversions for Dvorak “T” numbers). studies. There are many reasons why a reanalysis of the HURDAT dataset was session held in Geneva in June 1988. It both needed and timely. HURDAT has a record of tropical storms and contained many systematic and random typhoons in western North Pacific that errors that needed correction. extends back to 1951. Additionally, as our understanding of There are substantial differences in tropical cyclones developed, analysis the best-track archives of these two techniques at the National Hurricane institutions, sufficient to negate the trend Center changed over the years, and led found by W2005 in the JTWC data. to biases in the historical database. There are many substantial differences Recent efforts led by the late Jose in the locations, intensities, and wind Fernandez-Partagas uncovered distributions of the tropical cyclones that previously undocumented historical these agencies both diagnosed and tropical cyclones in the mid-1800's to tracked. Intensities are sometimes early 1900's. found to vary by two Saffir-Simpson In the western North Pacific, there are Categories. The archived distribution of several institutions that archive statistics gales and typhoon-force winds can vary of the tropical cyclones. The Joint by hundreds of kilometers. The objective Typhoon Warning Center (JTWC), now of the work reported in this paper is to located in Pearl Harbor, Hawaii, has a examine and summarize the differences nearly 50-year record of tropical storms that are found between the JTWC and and typhoons for the western North JMA best track archives, and to attempt Pacific Basin. The JTWC is jointly to explain them. The ultimate goal is to manned by the U.S. Navy and U.S. Air establish a working group of tropical Force to provide tropical cyclone cyclone diagnostic experts to undertake reconnaissance and forecast support to a project similar to the HRD Hurricane the U.S. Military and other U.S. Re-Analysis Project for the historical Government agencies and assets in the record of the tropical cyclones of the eastern Hemisphere. The JTWC has a western North Pacific. continuous record of tropical cyclone The historical record of tropical activity in the western North Pacific cyclones has become important in the extending from 1959 to present. Until scientific and political challenges of the year 2000, it also provided the names climate change, and the risks of the ever- for the TCs of that basin. The Tokyo increasing human habitation in cyclone- Typhoon Center is the Regional prone regions. It is of the utmost Specialized Meteorological importance to make the record as Center (RSMC) for the analysis, tracking accurate as possible. Real-time and forecasting of western North Pacific validation data are often not available. tropical cyclones within the framework Despite efforts to minimize conflicting of the World Weather Watch information, the JMA and the JTWC are Programme of the World Meteorological often quite far from each other in their Organization (WMO). The Tokyo diagnostic assessments of tropical Typhoon Center was established at the cyclone intensity and wind distribution. Headquarters of the Japan Part of this conflict results from the use Meteorological Agency (JMA) in July of different wind averaging periods for 1989, following the designation by the the warning intensity.