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The Influence of Extratropical Transition on Poleward Rossby Wave Breaking Lisa-Ann Quandt, J. H. Keller 1, S. C. Jones 1, A. Schneidereit 2, D. H. Peters.

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Presentation on theme: "The Influence of Extratropical Transition on Poleward Rossby Wave Breaking Lisa-Ann Quandt, J. H. Keller 1, S. C. Jones 1, A. Schneidereit 2, D. H. Peters."— Presentation transcript:

1 The Influence of Extratropical Transition on Poleward Rossby Wave Breaking Lisa-Ann Quandt, J. H. Keller 1, S. C. Jones 1, A. Schneidereit 2, D. H. Peters 2 Institute for Meteorology and Climate Research – Tropospheric Research (IMK-TRO) Weather Systems: Dynamics and Predictability (S. C. Jones) 1 DWD, Offenbach, Germany 2 IAP, Kühlungsborn, Germany

2 08/18/ Motivation Extratropical Transition (ET) (Jones et al., 2003, Klein et al., 2000,...) former Tropical Cyclone (TC) moves to the North new environment new storm characteristics (Frontogenesis) At upper levels: Interaction between the former TC and the Jet Stream (Davis et al., 2008)  ET System supports upper level Diffluence. Satellite images:

3 08/18/143 Rossby Wave Breaking (RWB) Diffluent Flow is required for P2 RWB. Idealized picture of asymmetric RWB events in a horizontal plane indicated by potantial vorticity (black lines): cyclonically sheared waves breaking predominatly in poleward (P1) or equatorward (LC2) direction, and anticyclonically sheared waves breaking predominantly in poleward (P2) or equatorward (LC1) direction; black arrows: westerly jet with horizontal shear; dashed lines: geopotential of a basic flow; and white arrows: meridional eddy fluxes down the gradient of the westerly jet. [Gabriel & Peters, 2008]

4 08/18/144 Hypothesis Diffluent FlowExtratropical Transition P2 Rossby Wave Breaking Diffluent Flow Is there a connection between ET and P2 RWB?

5 08/18/ Approach Ensemble forecasts of ECMWF Empirical Orthogonal Function Analysis Fuzzy Clustering Suitable forecasts? Largest variability? Different scenarios? Can we observe a RWB event during ET? Subsequent Blocking? How to quantify that observation?  Wave Activity Flux (WAF)

6 08/18/ Results of Hurricane Noel (2007) EOF Analysis Initialisation time: UTC Shown Quantities: Potential 2 PVU (shaded) and EOFs (red lines)

7 08/18/147 Comparison (with/without ET of Noel) Initialisation time: UTC Shown Quantities: Potential 2 PVU (shaded) and SLP (blue lines) With ETWithout ET

8 08/18/148 With ET Without ET 108 h 156 h 192 h

9 08/18/149 Wave Activity Flux (Takaya & Nakamura, 1997) Shown Quantities: 320 K (shaded), Geopotential 1000 hPa (black lines) & RWB-P2 (blue dotted lines) Figure: made by Andrea Schneidereit

10 08/18/ Results of Hurricane Jeanne (2004) Initialisation time: UTC Shown Quantities: Potential 2 PVU (shaded) SLP (blue lines) on the left and Wind Velocity with Wind 200 hPa on the right 108 h 156 h Case with ET

11 08/18/ Observed Interactions Trough Interaction Ridge Interaction Poleward anticyclonic RWB (P2) Poleward cyclonic RWB (P1) Suppressed equatorward anticyclonic RWB (LC1) with ETwithout ET

12 08/18/ Conclusion Diffluent FlowExtratropical Transition P2 Rossby Wave Breaking Diffluent Flow Is there a connection between ET and P2 RWB?

13 08/18/ Conclusion Diffluent FlowExtratropical Transition P2 Rossby Wave Breaking Diffluent Flow Is there a connection between ET and P2 RWB? Yes, it seems that ET may influence RWB!

14 08/18/ Summary Research Question: Does ET influence poleward RWB? Approach: Comparison of cases with and without ET Data: Ensemble forecasts (ECMWF) EOF Analysis + Fuzzy Clustering WAF Results: observed influence of ET on RWB interaction dependent on phasing importance of generation of upper level vortex

15 08/18/ Summary Research Question: Does ET influence poleward RWB? Approach: Comparison of cases with and without ET Data: Ensemble forecasts (ECMWF) EOF Analysis + Fuzzy Clustering WAF Results: observed influence of ET on RWB interaction dependent on phasing importance of generation of upper level vortex Thanks for your Attention! Questions? Thanks for your Attention! Questions?


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