Extended Abstract (88K)16C.1
Have there been any typhoons stronger than Super Typhoon Tip?
Karl Hoarau, Cergy-Pontoise University, Cergy-Pontoise, France; and G. Padgett and J. P. Hoarau
Super Typhoon (STY) Tip is still considered the strongest tropical cyclone to have formed in the Western North Pacific since the beginning of the reconnaissance era (ATCR). The minimum sea level pressure was measured at 870 hPa on 12 October 1979 at 0353 UTC (Dunnavan and Diercks, 1980), but the surface maximum sustained wind (MSW) of 165 knots over one minute was estimated from the pressure-wind relationship developed by Atkinson and Holliday (1977).
Since the end of routine aerial reconnaissance in the Western North Pacific (WPAC) in August, 1987, the primary question is: have there been tropical cyclones (TC) which reached an intensity greater than 165 knots, based on satellite imagery? Or, are we obliged to regard this intenisty as a superior limit for a tropical cyclone in the absence of aircraft measurements (Lander and Guard, 2001)? A second question is: if it is possible to have a TC with a surface MSW greater than 165 knots, what magnitude of Dvorak T-numbers, both manual and objective (ODT), should a TC display in order to be regarded as a stronger typhoon than Tip? In an attempt to answer the first question in the affirmative, we obtained satellite images of STY Tip as well as pictures of the strongest WPAC typhoons which have occurred since August, 1987.
The study indicates that STY Tip displayed a maximum ODT number of 8.2 well before the lowest pressure was recorded, a feature previously highlighted by Lander in the 1996 ATCR. In fact, on 11 October at 1529 UTC, a reconnaissance plane found a SLP of 900 hPa, although the ODT was already at 8.2 on the 1603 UTC GMS picture. Interestingly, manual Dvorak T-numbers reached 8.0 during a 4.5-hour period which ended one hour before the measurement of 870 hPa. These T8.0 numbers have been obtained by taking into account a band feature of 0.5T on the EIR pictures. At this time, the ODT was decreasing progressively at 7.8. This is the basis for agreeing with the 165 knots previously estimated and to believe that the 870 hPa was probably the minimum SLP.
Among the strongest TCs in the WPAC since August, 1987, we found three candidates which had ODT numbers higher than Tip, between 8.3 and 8.5, and for a longer time period. These TCs are: Yuri (Nov, 1991), Gay (Nov, 1992) and Angela (Nov, 1995). These typhoons reached manual Dvorak T-numbers of 8.0 without a spiral band and which persisted for six to twelve hours. A remarkable and common feature of these three cyclones was that the ODT and manual Dvorak T-numbers peaked at the same time. The peak MSW of Yuri, Gay and Angela have been estimated at 150 knots, 160 knots and 155 knots, respectively (1991, 1992 and 1995 ATCRs). In addition, in 1997 three TCs were estimated to have peaked at 160 knots: Ivan (Oct), Joan (Oct) and Paka (Dec). If the analysis of these latter typhoons justified 160 knots, this would strongly suggest that Yuri, Gay and Angela were even more intense. So, in conclusion, we believe that these three TCs could be classified at the top of the Dvorak scale with the MSW near 170 knots.
Session 16C, tropical cyclone best track and climatology I
Friday, 7 May 2004, 8:00 AM-9:45 AM, Napoleon II Room
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