1. Interactions Between Equatorial Waves and Tropical Cyclones Paul E. Roundy WWOSC August 2014

2. Intraseasonal variability of tropical cyclones Diagnose the most favored relationships in space and time between TC genesis and MJO Equatorial Rossby waves Mixed Rossby Gravity (MRG) waves Kelvin waves

3. Diagnostics Follow a simplified approach after Frank and Roundy (2006) Filter OLR and wind anomaly data at 850 hPa for broad bands of different “wave” types. Generate TC-genesis centered composites of filtered data including only periods of enhanced activity in the filter bands 10 years of additional data allows me to increase the wave activity thresholds for including an event

4. Madden Julian Oscillation Eastward-moving global intraseasonal feature of circulation and convection, no broad agreement on its dynamics

5. Madden Julian Oscillation Eastward-moving global intraseasonal feature of circulation and convection, no broad agreement on its dynamics Influences TC genesis in all basins, although most directly through modulation of convection in the Eastern and Southern Hemispheres

6. Madden Julian Oscillation Eastward-moving global intraseasonal feature of circulation and convection, no broad agreement on its dynamics Influences TC genesis in all basins, although most directly through modulation of convection in the Eastern and Southern Hemispheres Interaction with the extratropical circulation and Kelvin waves allows it to strongly influence the northeast tropical Pacific basin

7. Madden Julian Oscillation MJO impacts on the Atlantic basin are also substantial, including through its modulation of synoptic wave activity, the vertical distribution of moisture, and vertical wind shear

14. Equatorial Rossby Waves Intraseasonal Westward-moving waves

22. MRG waves Form circulations centered on the equator Waves disperse energy eastward while the waves move westward TCs can be sources of MRG waves, but MRG waves can modulate TC genesis (e.g., Dickinson and Molinari 2002 JAS)

23. From Kiladis et al. (2009)

24. From Roundy and Janiga (2012)

41. Kelvin Waves Waves move rapidly eastward ~10-30 ms -1

42. Kelvin Wave Theoretical Structure Wind, Pressure (contours), Divergence, blue negative

43. Kelvin Waves Frank and Roundy (2006) did not achieve robust results in ourcomposite analysis consistent with Kelvin waves, suggestingthat Kelvin waves might not contribute systematically to TCgenesis. Some theoretical arguments supported this point ofview.

44. Kelvin Waves Frank and Roundy (2006) did not achieve robust results in ourcomposite analysis consistent with Kelvin waves, suggestingthat Kelvin waves might not contribute systematically to TCgenesis. Some theoretical arguments supported this point ofview. Bad conclusion

45. Kelvin Waves Frank and Roundy (2006) did not achieve robust results in ourcomposite analysis consistent with Kelvin waves, suggestingthat Kelvin waves might not contribute systematically to TCgenesis. Some theoretical arguments supported this point ofview. Bad conclusion First clue to me was from watching numerous wave events overthe Indian basin followed by TC genesis over the Bay of Bengal

56. From Ventrice et al. 2012, Mon. Wea. Rev. Kelvin Waves and Atlantic TC Genesis:

57. Why? Theoretical Kelvin waves include no potential vorticity signature because the thermodynamics directly compensate for the dynamics Convectively coupled Kelvin waves modulate convection, and that convection generates a PV response, yielding PV “wakes” behind the waves (MacRitchie and Roundy 2012, JAS).

58. From Ventrice et al. 2012, Mon. Wea. Rev.

59. Kelvin Wave @ 70°E Negative PV anomalies prior to Kelvin wave passage Abrupt jump to positive PV anomalies following Kelvin wave passage Legend (contours are 4 W/m 2 ) MJO Active OLR Kelvin Active OLR

60. Kelvin Wave @ 70°E Negative PV anomalies prior to Kelvin wave passage Abrupt jump to positive PV anomalies following Kelvin wave passage Legend (contours are 4 W/m 2 ) MJO Active OLR Kelvin Active OLR + - + -

61. Kelvin Wave @ 90°E Negative PV anomalies prior to Kelvin wave passage Abrupt jump to positive PV anomalies following Kelvin wave passage Legend (contours are 4 W/m 2 ) MJO Active OLR Kelvin Active OLR

62. Kelvin Wave @ 110°E Negative PV anomalies prior to Kelvin wave passage Abrupt jump to positive PV anomalies following Kelvin wave passage Legend (contours are 4 W/m 2 ) MJO Active OLR Kelvin Active OLR

63. Composite Negative PV anomalies prior to Kelvin wave passage Abrupt jump to positive PV anomalies following Kelvin wave passage Legend (contours are 4 W/m 2 ) MJO Active OLR Kelvin Active OLR

64. Lag -3 Days For Reference:

65. Lag -2 Days For Reference:

66. Lag -1 Days For Reference:

67. Lag 0 Days For Reference:

68. Lag +1 Days For Reference:

69. Lag +2 Days For Reference:

70. Lag +3 Days For Reference:

71. Conclusions The MJO and equatorial waves modulate the locations and timing of TC genesis events over all basins Kelvin waves modulate TC formation and are far more important than originally reported by Frank and Roundy (2006)