1. The Controversy Regarding HS3 Surface Pressure Observations During The Rapid Intensification of Edouard on September 14-15 Scott Braun NASA/GSFC

2. Controversy over Dropsonde Data During Sept. 14-15 Flight NHC night shift rejected HS3 dropsonde measurements of surface pressure during flight Morning shift reversed decision, upgraded storm intensity However, final storm report did not accept HS3 central pressure estimates

3. NOAA P-3 and GH MSLP Measurements Date/TimeLocation relative to center Psfc (mb) Wind Speed (kt) Estimated MSLP(mb)** P3 14/1500Eye center9834 P3 14/1707NE98480976 GH 14/2103N97289963 GH 15/0031N96786958 GH 15/0034S97756971 GH 15/0217W_SW97556970 GH 15/0428N97184963 GH 15/0552NW97268965 **Surface pressure adjusted 1 mb for each 10 kt Adjusted Psfc derived from lowest altitude pressure measurement

4. GH Surface Pressures and Winds Surface PressureSurface Winds Pressures and winds appear consistent with strong storm Wind barbs show storm-relative winds

5. NHC Final MSLP Time Series

6. P-3 drops North-side GH drops South-side GH drops North-side GH drops

7. The Beginning of a Convective Burst 9/14 1045 UTC 9/14 1145 UTC 9/14 1345 UTC9/14 1245 UTC Convective burst began near 1045 UTC on NW side of eye Over time, CB cloud shield expanded and moved to southern side As cloud shied expanded, the eye was obscured

8. The First P-3 Drop 9/14 1445 UTC 9/14 1457 UTC 9/14 1500 UTC NOAA P-3 dropsonde reported MSLP of 983 mb, 2 m s -1 surface wind The eye is still obscured by CB cirrus shield

9. Gradual Formation of a New Eye 9/14 1515 UTC9/14 1545 UTC 9/14 1615 UTC9/14 1645 UTC CB cloud shield continues to circle around southern to eastern sides New eye begins to for by ~1645 UTC 9/14 1618 UTC

10. Last P-3 Drop 9/14 1715 UTC 9/14 1707 UTC NOAA P-3 dropsonde reported MSLP of 984 mb, 41 m s -1 surface wind. Suggests possible MSLP closer to 976 mb, a 7 mb decrease from the dropsonde 2 hours before. Very small, well-defined eye present by 1715 UTC

11. GH dropsonde at 2103 UTC reported MSLP of 972 mb, 46 m s -1 (89 kt) surface wind. Suggests possible MSLP closer to 963 mb, a 13 mb decrease from the P-3 dropsonde 4 hours before. 9/14 2115 UTC 1 st GH “Eye” Drop 700 800 1000 600 500 400 300 200 100

12. 2 nd GH Eye Drop GH dropsonde at 0031 UTC reported MSLP of 967 mb, 44 m s -1 (86 kt) surface wind. Suggests possible MSLP closer to 958 mb, a 5 mb decrease from the GH dropsonde 3.5 hours before.

13. 2 nd GH Eye Drop GH dropsonde at 0031 UTC reported MSLP of 967 mb, 44 m s -1 (86 kt) surface wind. Suggests possible MSLP closer to 958 mb, a 5 mb decrease from the GH dropsonde 3.5 hours before. 700 800 1000 600 500 400 300 200 100

14. Edouard Appears to Undergo an ERC 9/15 0215 UTC9/15 0415 UTC9/15 0545 UTC 9/15 0815 UTC9/15 1315 UTC9/15 0645 UTC

15. Storm Evolution and Intensity Change CB begins Small eye forms Small eye begins breakdown Large eye begins to form >3 hPa/h pressure fall

16. Is the Observed Rate of Pressure Fall Likely? Used HURDAT data from 1970-2013 to compute 6-h pressure changes for all named storms during mid-August to mid-October Here expressed as 1-h pressure change rates and shown as a function of max. wind speed at time of pressure change 3 hPa/h rates only observed for storms that go on to become Cat 4-5

17. Is the Observed Rate of Pressure Fall Likely? Max wind change vs min SLP change 25 hPa/9.5 h (2.6 hPa/h) pressure drop implies ~31 kt increase in max winds Storm max wind should have increased from ~72 to ~103 kt (Cat 3) 2103Z Sep 14 sounding had 89 kt (46 m s -1 ) NHC had storm as 80 kt (strong Cat 1)

18. Is the Observed Rate of Pressure Fall Likely? Max wind change vs min SLP change 22 hPa/9.5 h (2.3 hPa/h) pressure drop implies ~28 kt increase in max winds Storm max wind should have increased from ~72 to ~100 kt (Cat 3) 2103Z Sep 14 sounding had 89 kt (46 m s -1 ) NHC had storm as 80 kt (strong Cat 1)

19. Conclusions P-3 and GH dropsondes were consistent with satellite indications of rapid intensification Several drops indicated likely central pressures in the 960’s mb Magnitude of pressure drop appears too intense (typical of Cat 4-5 storms and very rare) Do we declare that this was an unusual Cat 3 storm or re-examine the validity of the measurements? Is there a region of ~51 m s -1 somewhere in here?

20. Extra slides

21. 15 Past Storms With  P/  T≤3mb/h Anita (1977, 5)-18mb/6h, -32mb/12h in consecutive times Gloria (1985, 4)-24mb/6hsecond period of -30mb/12h Gilbert X 2 (1988, 5)-18mb/6h, -29mb/6h, -64mb/18h Hugo (1989, 5)-22mb/6h-39mb/12h Opal X 2 (1995, 4)-18mb/6h,-19mb/6h in consecutive times Edouard (1996, 4)-18mb/6h,-27mb/12h Bret (1999, 4)-21mb/6h Keith (2000, )-22mb/6h Iris (2001, 4)-25mb/6h, -38mb/12h Ivan (2004, 5)-22mb/6h,-32mb/12h Katrina (2005, 5)-21mb/6h Rita X 2 (2005, 5)-21mb/6h,-23mb/6h,-58mb/18h Felix X 2 (2007, 5)-18mb/6h,-27mb/6h,-50mb/18h Ike X 2 (2008, 4)-23mb/6h,-21mb/6h, -54mb/18h Igor (2010, 4)-22mb/6h,-39mb/12h, -50mb/18h

22. Is the Observed Rate of Pressure Fall Likely? Used HURDAT data from 1970-2013 to compute 6-h pressure changes for all named storms during mid-August to mid-October Here expressed as 1-h pressure change rates and shown as a function of max. wind speed at time of pressure change 3 hPa/h rates rarely observed Generally happen for systems of hurricane strength

23. GH Surface Pressures and Winds Surface Pressure Surface Winds Approximate RMW from 18Z P-3 LF radar image Dual-Doppler wind analysis at 0.5 km valid 15Z Pressures and winds appear consistent with strong storm HRD Doppler analysis suggests max winds (in NE eyewall) probably were not sampled by dropsondes

24. Each of Last 3 Eye Drops Entered Eyewall

25. 9/15 0041 UTC 9/15 0532 UTC 9/15 0949 UTC9/15 1520 UTC

26. 9/14 1126 UTC9/14 1813 UTC9/14 2119 UTC 9/15 0949 UTC9/15 1158 UTC 9/15 1520 UTC 9/15 0041 UTC9/15 0532 UTC9/15 0641 UTC

27. NHC Final MSLP Time Series Compared to P-3 and GH Dropsondes

28. NOAA P-3 and GH MSLP Measurements Date/TimeP (mb)GPS Alt.TempSLPWind Speed (ms -1 ) Adjusted Psfc (mb)** P3 14/15009834 P3 14/170798480976 GH 14/210397033.23299.2497489965 GH 15/003196630.00299.5497086961 GH 15/003497530.60299.4597956973 GH 15/021797430.80298.8997856972 GH 15/042897031.10299.4297384965 GH 15/055297131.40299.3097468967 **Surface pressure adjusted 1 mb for each 10 kt Psfc derived from lowest altitude pressure measurement with GPS altitude, adjusted to surface using corresponding temperature and hypsometric Eq.

29. NHC Final MSLP Time Series Compared to P-3 and GH Dropsondes