Fig. 1.
Illustrative example of a frontal wave-train observed over the central North Atlantic and western Europe at 00Z on the 30 October 2020. Panel (a) displays the SLP pattern (contours interval 5 hPa) and the accompanying frontal palette. Remaining panels display the contemporaneous pattern of (b) the 2 m temperature (coloured contours every 30K), (c) the geopotential height (white isolines, gpdm) and temperature (contours interval 5°) on the 850 hPa surface and (d) the SLP field (white isolines every 5 hPa) and the geopotential field on the 500 hPa surface.
Fig. 2.
Depiction of the surface patterns of a finite amplitude Eady edge wave on a zone of uniform baroclinicity confined by rigid lateral walls. Panels show the distribution of (a) the potential temperature and (b) the relative vorticity (See text for further details).
Fig. 3.
A schematic of the basic states for the prototype cold and warm frontal configurations. The profiles refer, respectively, to the along-front velocity (U), and the across-front buoyancy pattern (B). The symbol L denotes the location of the parent cyclone.
Fig. 4.
Upper panel shows the dispersion diagram of the dimensionless frequency (ω*) and dimensionless wavenumber (K) for Eady edge wave perturbations for two baroclinic settings. The continuous curves are for the C1 and C2 modes on an idealised cold front, whilst the dashed lines are for the counterpart E1 and E2 modes on a zone of uniform baroclinicity. Lower panels show the across-front buoyancy profiles of the C1 and C2 modes for, respectively, K = 0.5 and 1.5.
Fig. 5.
As for Fig. 4, but now for the W1 and W2 modes on an idealised warm front, and the across-front buoyancy profiles are both for K = 2.0.
Fig. 6.
Schematic of the potential temperature distribution at the surface following a transient forcing by an upper-level PV anomaly. Panels (a and b) depict, respectively, the initially induced cold-warm couplet, and the subsequent evolution of propagating coherent wave-packets of long (half width L 1) and intermediate (half width L 2), and the stationary pulsating short (half width L 3) wave-packet.