Extratropical and Tropical Transition

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

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

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

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

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

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

Cyclone Phase: Thermal Asymmetry Storm-relative 900-600hPa mean thickness field (shaded) asymmetry within 500km radius: 3160m 3260m L Adapted from slides provided by Bob Hart (FSU) at http://moe.met.fsu.edu/cyclonephase/.

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 http://moe.met.fsu.edu/cyclonephase/.

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: 900-600 hPa: -VTL 600-300 hPa: -VTU -VT < 0 = Cold-core, -VT > 0 = Warm-core Adapted from slides provided by Bob Hart (FSU) at http://moe.met.fsu.edu/cyclonephase/.

Cyclone Phase: Thermal Wind Warm-core example: Floyd 14 Sep 1999 Focus here on 900-600hPa -VTL >> 0 Adapted from slides provided by Bob Hart (FSU) at http://moe.met.fsu.edu/cyclonephase/.

Cyclone Phase: Thermal Wind Cold-core example: Cleveland Superbomb 26 Jan 1978 Focus here on 900-600hPa -VTL << 0 Adapted from slides provided by Bob Hart (FSU) at http://moe.met.fsu.edu/cyclonephase/.

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

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

Downstream Development strong interaction weak interaction (Figures obtained from Archambault et al. (2015), their Figs. 5-6. © 2015, American Meteorological Society.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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.)

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

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

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

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

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