1. Andrew Burton Bureau of Meteorology, Perth, Australia Use of Scatterometer Winds in TC Forecasting Tropical Cyclone Warning Centre Perth

2. Application of Scatterometer to Tropical Cyclone Forecasting Formation Size (radius of gales) Wind distribution Not for absolute intensity (winds saturate at >60 90? knots)

3. Where to Get Scatterometer Data NRL Monterey http://www.nrlmry.navy.mil/tc_pages/tc_home.html NOAA/NESDIS QuikSCAT http://manati.wwb.noaa.gov/quikscat Storms page – includes ambiguities: http://manati.wwb.noaa.gov/cgi-bin/qscat_storm.pl Alternative NOAA site, with SSMI wind speeds: http://polar.wwb.noaa.gov/winds/globdata.html FNMOC http://152.80.49.210/PUBLIC/SCAT orhttp://www.fnmoc.navy.mil/PUBLIC/SCAT Remote Sensing Systems http://www.ssmi.com

4. NRL Monterey http://www.nrlmry.navy.mil/tc_pages/tc_home.html

5. NOAA/NESDIS QuikSCAT http://manati.wwb.noaa.gov/quikscat

6. FNMOC http://152.80.49.210/PUBLIC/SCAT/ Near Real-Time Ambiguity Removal FNMOC Ambiguity Removal over SSMI

7. Remote Sensing Systems http://www.ssmi.com

8. Differences Wind retrieval RSS uses KU-2000 wind retrieval method Others use QuikSCAT1 wind retrieval method Rain Flags Generally Multidimensional Histogram (MUDH) procedure – a statistical method based on “noisiness” of data RSS has similar approach though it is less conservative and hence rain affected areas are often smaller

9. Scatterometer Coverage

10. QuikSCAT: SeaWinds Measurements From Dr. M. Freilich, Oregon State University V-pol H-pol

11. SeaWinds: Swath Geometry From Dr. M. Freilich, Oregon State University Red = V-pol Blue = H-pol Edge View (2 solns) V-pol only Subtrack View (4 solns,but small angle var) Ideal View (4 solns, 90 deg var) Forward Look Backward Look

12. Scatterometry: 2-Look Solutions From Dr. M. Freilich, Oregon State University 1 2 3 4 Solution: wind ~10m/s at ?? deg From Dr. M. Freilich, Oregon State University

13. Scatterometry: 4-Look Solution(s) From Dr. M. Freilich, Oregon State University 1 2 3 4 Most-likely solution: 10m/s at 40deg From Dr. M. Freilich, Oregon State University

14. Ambiguities: The Chicken-Scratch Diagram

15. Location, Intensity, Wind Distribution Source: Tropical storms discussion group

17. 25 Jan 1800Z 26 Jan 0517Z 26 Jan 1800Z 27 Jan 1712Z 28 Jan 0427Z X X X X O O O O O 20S 170W 160W Small system (X) analysed for 3 days --no help from NWP model

18. Edge of swath (~ 7 wind vector cells) Rain effects Sensitivity to errors in NWP Practical wind regime 3-45? m/s (problems with both very light and very strong winds) Resolution (25km) – impact in tight gradients Ambiguity Removal Process and rain flag process can affect final solution Interpretation Challenges

19. Edge Problems Along the whole edge… or small portion… FNMOC DISPLAY

20. Rain Flags: MUDH vs RSS TC Ando RSS FNMOC-NOGAPS FNMOC-NRT Same Coverage Less Coverage

21. Position using the curvature outside ‘rain block’ region. Look for good north-south winds. Rain Effects – “tear drop”

22. Streamlines X Look for non-rain flagged winds Beware of winds perpendicular to the swath, even when they are not flagged TC Chris 03/02/02 0914Z

23. Isotachs X Look for min speed near centre TC Chris 04/02/02 1002Z

24. Errors in NWP Wrong Model Position? TC Guillaume 19/02/02 1341Z

25. Where is TC HUDAH? No circulation! ? Max Winds 95 knots Try to fix in trough equator-ward of the strongest winds

26. ? ? c c Max Wind 55 KTS (Light winds?) -----low skill AVN 19/12Z tau 24 20/2356Z 10S 20S In this case, poor model initialization combined with a lower skill nadir position, picks proper wind speed, but NO circulation center TC Paul Model initialization errors

27. Comparing Different Solutions FNMOC-NOGAPSFNMOC-NRT

28. NRCS imagery Normalised Radar Cross Section

29. 14 S 10 S 18 S 92 E88 E 84 E92 E88 E84 E Scatterometer winds give wrong estimate for centre Comparison between Quikscat solution from NESDIS 30/11/2001 at 0023Z and fair LLCC seen in SSMI near 14.4S 89.1E 30/11/2001 at 0218Z Microwave Imagery vs Quikscat

30. Analysis Methods - Summary Ignore the bad - streamline the good Tear-drop – curved end TC’s – equatorward side of max wind Compare different solutions Isotach method – ignore direction

31. Conclusions Provides coverage over data sparse areas Wind speeds generally good – useful for areas of gales etc Use the data if it makes sense Be aware of low skill areas and different ambiguity removal processes (compare!) Do not use in isolation