Another subtype of "Cold Fronts" is the "Cold Front in Warm Advection" (CF in WA). It is an important conceptual model especially in respect to the life cycle of a Cold Front. It occurs less frequently than a "Cold Front in Cold Advection" and shows dependence on season: in winter there are very few CF in WA whereas in summer they become as frequent as those in Cold Advection. Maybe it sounds like a contradiction that a system is called "Cold Front" although it is under the influence of warm advection. How can it then be a Cold Front? There are three main reasons:

• Because of a typically frontal, cyclonically curved, synoptic scale cloud band,
• Because of its belonging to a frontal system consisting of Warm and Cold Fronts (following the polar front theory) and,
• Because the vertical cross section shows a typical Cold Front - like downward inclined zone of high gradients of isentropes.

In satellite imagery CF in WA cloud bands often look similar to classical Cold Fronts but several times (a third of the cases) they consist only of low cloud bands. This is more frequent than with CF in CA (see Cold Front In Cold Advection ).

In several cases (about 40% of the 30 investigated) they look more fibrous and broken than classical Cold Fronts.

As with the CF in CA, CF in WA can be only a part of a frontal cloud band (the other part(s) is/are classical Cold Front and/or CF in CA) or they can appear as a complete frontal cloud band. Both types are shown below.

Two CF in WA are indicated. The northern one is the part consisting of lower cloud tops (darker grey shades in IR) within a longer frontal cloud band. It is worth mentioning that this part is in advance of a Wave - like cloud bulge (see Wave - Key Parameters ) around 50N/40W, a conceptual model which is typically connected with WA in the cloud bulge. The southern CF in WA indicates a complete frontal cloud band under WA. The cloud band across the Iberian Peninsula does not belong to the frontal system, but is generated by a superimposed jet stream. The jet axis coincides with the edge of the cloudiness. The deformation field shows a maximum above the cloud band.

But sometimes the CF in WA is only part of a classical Cold Front especially in westernmost sections.

The image shows a Cold Front in Warm Advection with prevailing low level cloudiness and some higher clouds embedded. There is not the bright appearance one would expect with a classical Cold Front.

The main reason for the development of a CF in WA is the overtaking of WA from an approaching new system.

In several cases a new frontal system approaches to the rear of the Cold Front leading to an overtaking of warm advection.

In this example the WA is in front of an approaching Warm Front band.
But other conceptual models showing some Warm Front - like features, such as Detached Warm Fronts, Baroclinic Boundaries and Warm Conveyor Belts, can also be the source of overtaking WA. A sequence of images shown below demonstrates the latter case. The sequence shows the approach of a pronounced WA maximum from N. Africa northwards into the Mediterranean. It becomes superimposed on a Cold Front cloud band there. The WA maximum is associated with a warm conveyor belt cloud system which develops over N. Africa and is later situated over the Mediterranean.