Composite Analysis of Tropical Cyclogenesis
over the North Atlantic during 2004-2008
KEY:
Click on the image to view the 48-h loop from T-48 h to T-0 h.
Times are relative to the NHC-defined time of TC genesis for TCs, and
the time of initial peak in 900 hPa vorticity for null cases.
a=upper-left panel; b=upper-right; c=lower-left; d=lower-right.
Dynamic tropopause (DT) defined at 2.0 PVU surface.
1.0 degree NCEP GFS analyses dataset used.
Tropical
Transition Cases (strong TT, weak TT, and
trough induced are combined)
1. Events
beneath upper-level cutoff low (7 TCs; 9 null cases) **Loops are now 72-h
at 6-h intervals. Air parcel
trajectories added!!
2. Positively-tilted ridge-trough
couplet (21 TCs; 16 null cases)
a. Foldover
west (11 TCs; 10 null cases) **Loops are now 72-h
at 6-h intervals. Air parcel trajectories added!!
b. Foldover
east (9 TCs; 4 null cases) **Loops are now 72-h
at 6-h intervals. Air parcel trajectories added!!
(schematic)
3. Strong trough northeast of
incipient disturbance (0 TCs; 21 null
cases)
4. Broad upstream trough (13
TCs; 27 null cases) **Loops are now 72-h
at 6-h intervals. Air parcel trajectories added!!
5. Deep southwesterly flow (0
TCs; 8 null cases)
6. Deep westerly flow (0 TCs; 6
null cases)
Tropical
Developments
1. Eastern North Atlantic low-level
baroclinic southerly track (7 TCs;
10 null cases) **Loops
are now 72-h at 6-h intervals. Air parcel trajectories added!!
2. Eastern North Atlantic low-level
baroclinic northerly track (0 TCs;
9 null cases)
3. Western Caribbean nonbaroclinic
(10 TCs; 3 null cases)
4. Main development region nonbaroclinic
(18 TCs; 20 null cases)