1. Extratropical and Tropical Transition

2. Climatology of Extratropical Transition
(Figure obtained from Jones et al. (2003), their Fig. 1. © 2003, American Meteorological Society.)

3. Climatology of Extratropical Transition
(Figure obtained from Jones et al. (2003), their Fig. 2. © 2003, American Meteorological Society.)

4. Extratropical Transition Overview
(Figure obtained from Jones et al. (2003), their Fig. 11. © 2003, American Meteorological Society.)

5. Wind Field Evolution During ET
(10-m)
(Figure obtained from Evans and Hart (2008), their Fig. 5. © 2008, American Meteorological Society.)

6. Wind Field Evolution During ET
(Figure obtained from Evans and Hart (2008), their Fig. 7. © 2008, American Meteorological Society.)

7. Conceptual Model of ET
(Figure obtained from Klein et al. (2000), their Fig. 5. © 2000, American Meteorological Society.)

8. Cyclone Phase: Thermal Asymmetry
Storm-relative hPa mean thickness field (shaded) asymmetry within 500km radius:
3160m
3260m L
Adapted from slides provided by Bob Hart (FSU) at

9. Cyclone Phase: Thermal Asymmetry
Forming (B0) Mature(B0) Decay(B0)
Conventional Tropical cyclone: B  0 L L L
Developing(B>>0) Mature(B>0) Occlusion(B0)
Conventional Extratropical cyclone: B varies L L L
Adapted from slides provided by Bob Hart (FSU) at

10. Cyclone Phase: Thermal Wind
e.g., 700 hPa height
Z = ZMAX-ZMIN:
Isobaric height difference within 500 km radius
ZMAX
500 km
Proportional to geostrophic wind (Vg) magnitude
Z = d f |Vg| / g where
d = dist between height extrema, f = Coriolis, g = gravity
ZMIN
Vertical profile of ZMAX-ZMIN is proportional to thermal wind (VT) if d is constant:
hPa: -VTL hPa: -VTU
-VT < 0 = Cold-core, -VT > 0 = Warm-core
Adapted from slides provided by Bob Hart (FSU) at

11. Cyclone Phase: Thermal Wind
Warm-core example: Floyd 14 Sep 1999
Focus here on hPa
-VTL >> 0
Adapted from slides provided by Bob Hart (FSU) at

12. Cyclone Phase: Thermal Wind
Cold-core example: Cleveland Superbomb 26 Jan 1978
Focus here on hPa
-VTL << 0
Adapted from slides provided by Bob Hart (FSU) at

13. Downstream Development
(Figure obtained from Archambault et al. (2013), their Fig. 4. © 2013, American Meteorological Society.)

14. Downstream Development
(Figure obtained from Archambault et al. (2015), their Fig. 8. © 2015, American Meteorological Society.)

15. Downstream Development
strong interaction
weak interaction
(Figures obtained from Archambault et al. (2015), their Figs © 2015, American Meteorological Society.)

16. Downstream Development
Shading: ϴ (K) on 2 PVU surface
Bold Contours: wind speed on 2 PVU surface (>45 m s-1 every 5 m s-1)
Dashed Contours: mean sea level pressure (hPa, every 5 hPa)
t = 120 h
t = 156 h
t = 192 h
t = 240 h
(Figure obtained from Riemer et al. (2008), their Fig. 2. © 2008, Royal Meteorological Society.)

17. Downstream Development
t = 72 h
Shading: ϴ (K) on 2 PVU surface
Contours: meridional advection of ϴ (K s-1) on 2 PVU surface
Vectors: wind field on 2 PVU surface (m s-1)
Due to TC Itself
Due to TC Outflow
(Figure obtained from Riemer et al. (2008), their Fig. 6. © 2008, Royal Meteorological Society.)

18. Downstream Development
t = 72 h
Shading: ϴ (K) on 2 PVU surface
Contours: meridional advection of ϴ (K s-1) on 2 PVU surface
Vectors: wind field on 2 PVU surface (m s-1)
Due to TC as a Whole
Due to Divergent Flow
(Figure obtained from Riemer et al. (2008), their Fig. 6. © 2008, Royal Meteorological Society.)

19. Downstream Development
t = 132 h
Shading: ϴ (K) on 2 PVU surface
Contours: meridional advection of ϴ (K s-1) on 2 PVU surface
Vectors: wind field on 2 PVU surface (m s-1)
Due to TC Itself
Due to TC Outflow
(Figure obtained from Riemer et al. (2008), their Fig. 7. © 2008, Royal Meteorological Society.)

20. Downstream Development
t = 132 h
Shading: ϴ (K) on 2 PVU surface
Contours: meridional advection of ϴ (K s-1) on 2 PVU surface
Vectors: wind field on 2 PVU surface (m s-1)
Due to TC as a Whole
Due to Longwave Pattern
(Figure obtained from Riemer et al. (2008), their Fig. 7. © 2008, Royal Meteorological Society.)

21. Downstream Development
Contour: 340 K isentrope on 2 PVU surface
t = 108, 144, 180, 240 h
Thin: reference ET; dark grey: TC shifted SW; light grey: TC shifted further SW; dashed: reference sans ET
(Figure obtained from Riemer and Jones (2010), their Fig. 13. © 2010, Royal Meteorological Society.)

22. Post-Transition: Slow vs. Fast
Fast (left), Slow (right), valid at start time of ET
500 hPa heights (contour; dam) and height anomaly from monthly mean (shaded; dam)
850 hPa ϴe (shaded and contour; K)
SST (contour; °C) and departure from monthly mean (shaded; °C)
(Figure obtained from Hart et al. (2006), their Fig. 11. © 2006, American Meteorological Society.)

23. Post-Transition: Strengthen vs. Weaken
Weaken (left), Strengthen (right), valid at start of ET
500 hPa heights (contour; dam) and height anomaly from monthly mean (shaded; dam)
850 hPa ϴe (shaded and contour; K)
SST (contour; °C) and departure from monthly mean (shaded; °C)
(Figure obtained from Hart et al. (2006), their Fig. 12. © 2006, American Meteorological Society.)

24. Post-Transition: Warm- vs. Cold-Core
Cold-core (left), Warm-core (right), valid at end of ET
500 hPa heights (contour; dam) and height anomaly from monthly mean (shaded; dam)
320 K PV (shaded; PVU)
Vertical cross-section of PV (shaded; PVU) along cross-section in panels c,d
(Figure obtained from Hart et al. (2006), their Fig. 14. © 2006, American Meteorological Society.)

25. Post-Transition: Warm- vs. Cold-Core
Cold-core (left), Warm-core (right), valid at end of ET
850 hPa ϴe (shaded and contour; K)
SST (contour; °C) and departure from monthly mean (shaded; °C)
(Figure obtained from Hart et al. (2006), their Fig. 14. © 2006, American Meteorological Society.)

26. Tropical Transition Climatology
(Figure obtained from McTaggart-Cowan et al. (2008), their Fig. 10. © 2008, American Meteorological Society.)

27. Tropical Transition Climatology
(Figure obtained from McTaggart-Cowan et al. (2008), their Fig. 14. © 2008, American Meteorological Society.)

28. Tropical Transition: Composites
(Figure obtained from Davis and Bosart (2004), their Fig. 1. © 2004, American Meteorological Society.)

29. Tropical Transition: Convection
(Figure obtained from Davis and Bosart (2004), their Fig. 2. © 2004, American Meteorological Society.)

30. Tropical Transition: Shear Reduction
(Figure obtained from Davis and Bosart (2004), their Fig. 3. © 2004, American Meteorological Society.)