Tropical Transition Cases

4. Positively-tilted ridge-trough couplet - Ridge west (11 TCs; 10 null cases)

TCs: Edouard (2008), Erin (2007), Beryl (2006), Gaston (2004), Maria (2005), Cristobal (2008), Tammy (2005), Omar (2008), Ophelia (2005), Gabrielle (2007), Franklin (2005)
Null: V04-344, V05-094, V05-150, V05-270, V05-271, V06-175, V06-369, V07-205, V07-246, V07-269
Horizontal composite maps at time = T-12 h:

1. potential vorticity (shaded in PVU), pressure (solid contours every 20 hPa), and wind (standard barbs in kt) on the (a) 310, (b) 320, (c) 330, and (d) 340 K isentropic surface at time = T-12 h
TCs
 Null cases

2. (a) DT pressure (shaded in hPa), DT-850 hPa wind shear (standard barbs in kt), and 850-700 hPa layer-average relative vorticity (solid contours > 0 every 2.0x10-5 s-1), (b) sea-level pressure (solid contours every 2 hPa), 1000-500 hPa thickness (dashed contours every 2 dam), and 300 hPa wind speed (shaded in m s-1), (c) 700 hPa streamfunction (solid contours every 2x106 m2 s-1), nondivergent wind (standard barbs in kt), and precipitable water (shaded in mm), and (d) 400-200 hPa layer-average Qnd divergence (shaded in 10-16 K m-2 s-1) and Qnd-vectors (arrows in 10-11 K m-1 s-1), and 300 hPa streamfunction (solid contours every 3x106 m2 s-1) at time = T-12 h.
TCs
 Null cases

3. (a) 700 hPa relative vorticity (solid contours > 0 every 2.0x10-5 s-1), 1000-500 hPa thermal wind (standard barbs in kt), and advection of 700 hPa relative vorticity by the 1000-500 hPa thermal wind (shaded in 10-9 s-2), (b) 850 hPa potential temperature (solid contours every 2oC), nondivergent wind (standard barbs in kt), and coupling index (shaded in K), (c) 925-850 hPa layer-average relative vorticity (solid contours > 0 every 2.0x10-5 s-1), resultant deformation (shaded in 10-5 s-1), and wind (standard barbs in kt), and (d) 900-700 hPa layer-average relative humidity (shaded in %), 850-700 hPa layer-average relative vorticity (dashed contours > 0 every 2.0x10-5 s-1), and 300 hPa streamfunction (solid contours every 2x106 m2 s-1) and irrotational wind (standard barbs in kt) at time = T-12 h.
TCs
 Null cases

4. (a) 900-600 hPa thermal vorticity (shaded in 10-5 s-1), thickness (solid contours every 2 dam), and thermal wind (standard barbs in kt), (b) as in panel (a), except for the 600-300 hPa layer, (c) 450-250 hPa layer-average Qnd divergence (shaded in 10-16 K m-2 s-1) and Qnd-vectors (arrows in 10-11 K m-1 s-1), and 350 hPa streamfunction (solid contours every 3x106 m2 s-1), and (d) same as in panel (c), except for the 500-300 hPa layer at time = T-12 h.
TCs
 Null cases


5. Top row: Zonal vertical cross section of potential vorticity (shaded in PVU), potential temperature (solid black contours every 2 K), and meridional wind component [solid (dashed) blue contours > 0 (< 0) every 2 m s-1). Middle row: Zonal vertical cross section of relative humidity (shaded in %), relative vorticity (solid red contours > 0 every 2.0x10-5 s-1), potential temperature (dashed contours every 3 K), and vertical motion (thick black contours <0 every 1.5x10-3 hPa s-1). Bottom row: Zonal cross section of relative vorticity (shaded in 10-5 s-1), equivalent potential temperature (solid contours every 2 K), wind (standard barbs in kt), and potential vorticity (dashed blue contours at 1.5 and 2.0 PVU). All cross sections are at time = T-12 h.
TCs
 Null cases





6. Top row: Meridional vertical cross section of potential vorticity (shaded in PVU), potential temperature (solid black contours every 2 K), and zonal wind component [solid (dashed) blue contours > 0 (< 0) every 2 m s-1). Middle row: Meridional vertical cross section of relative humidity (shaded in %), relative vorticity (solid red contours > 0 every 2.0x10-5 s-1), potential temperature (dashed contours every 3 K), and vertical motion (thick black contours <0 every 1.5x10-3 hPa s-1). Bottom row: Meridional cross section of relative vorticity (shaded in 10-5 s-1), equivalent potential temperature (solid contours every 2 K), wind (standard barbs in kt), and potential vorticity (dashed blue contours at 1.5 and 2.0 PVU). All cross sections are at time = T-12 h.
TCs
 Null cases





7. Vertical profile of  various quantities in a box centered on the incipient tropical disturbance. TCs are in red and null cases in blue. All cross sections are at time = T-12 h.
Zmax-Zmin (m) in 10ox10o box
 Mean Horizontal Divergence (10-5 s-1) in 4ox4o box Mean OW Parameter (10-9 s-2) in 4ox4o box

Mean Zonal Wind (m s-1) in 4ox4o box Mean Meridional Wind (m s-1) in 4ox4o box Mean Relative Humidity (%) in 4ox4o box

8. Atmospheric soundings surrounding disturbance. TCs are in red and left wind profile, and null cases in blue and right wind profile.Temperature (dew point) in solid (dashed) contours.
Schematic of sounding locations
A     B     C
D     E     F
G     H     I

9. Nine 72-h backward air parcel trajectories beginning at T-0 h. Trajectory contours are colored by pressure level, and are overlaid at the T-0 h composite analysis of precipitable water. The trajectories are numbered, with the red numbers marking the starting point (at T-0 h) and black numbers marking the ending point (T-72 h). The white circles mark the trajectory position at T-24 and T-48 h.
starting level (hPa) -- disturbance type
200 -- TC
200 -- Null case
500 -- TC
500 -- Null case
700 -- TC
700 -- Null case
900 -- TC
900 -- Null case