5.2                                   More on conventional surface and frontal analysis

The synoptic scale may be viewed as a link between the over–arching broad–scale flow and the meso/micro–scale through which the weather actually directly affects the particular area of interest. It may be argued, for example, that, gust fronts or sea breeze fronts aside, fronts characterise this link. On the one hand fronts are mesoscale across their usual direction of travel but are synoptic–scale along their length. Also typically the mesoscale structure of fronts is determined to a large extent by the synoptic–scale environment.

5.2.1                                Fronts near the Antarctic continent  

It is of interest to note that there is a dearth of information in the literature on atmospheric frontal characteristics at high southern latitudes let alone the forecasting of such features. (Ironically, there are far more references to oceanic fronts). On the one hand this is surprising given that the Norwegian polar–front theory became the basis for atmospheric frontal analysis pretty much world–wide (Saucier, 1955, p. 268). On the other hand, even today the Antarctic may be regarded as data sparse. And one suspects that the liberties in the application of frontal analysis in the early days of aviation reported by Beckworth (1976, p. 329) might equally apply today in the Antarctic context due to a lack of a consistent approach. It would be interesting to examine, for example, if the Norwegian cyclone model was the most appropriate model for all, or even many, cases in the Southern Hemisphere. As Shultz et al. (1998, pp. 1,767–68) have pointed out the Norwegian model is not without its critics and may be most appropriate for the area for which it was developed. Shultz and his colleagues compare the Norwegian model with the relatively new Shapiro–Keyser cyclone–frontal model (see Shultz et al.,1998, p. 1,770) for a brief description of this model and Shultz et al. (1998, p. 1,787, Figure 15) for sketches of the two conceptual models in the Northern Hemisphere context.

Figure 5.2.1.1 has adapted the Shultz et al. sketch (their Figure 15) of these models to the Southern Hemisphere context. A priori, fronts that impact on the Antarctic coast may arguably have more in common with the Shapiro–Keyser model, particularly the last stage, than they do the Norwegian model. It may well be that both the above models are applicable in the mid–latitudes of the Southern Hemisphere, where many of the high–latitude storms originate, according to the background flow in which each cyclone is embedded (by analogy see Shultz et al. (1998, p. 1,787). However, if either frontal type reaches the Antarctic coast it becomes more like the Shapiro–Keyser model. However, this speculation would need to be tested against numerical and observational data. In view of the doubt about the characterisation of fronts near the Antarctic continent this section will deal primarily with the forecasting of synoptic scale low depressions and anticyclones.

5.2.2                                Conventional analysis over the oceans

The term "conventional" here refers to the analysts' normal use of MSLP observations and satellite interpretation along with the analysis cycles of NWP models to derive a MSLP analysis. For oceanic areas of the Antarctic there appears little difference in approach when compared to the oceans elsewhere in the world, the above comments regarding frontal/cyclone models notwithstanding.