*2.2. Meteomarine Features of the Molise Coast*

Wind, wind-generated waves, and astronomically and meteorologically induced sea level variations affecting the Molise coast are framed in the meteo-marine context that characterizes the Adriatic Sea.

Typical strong winds above the Adriatic Sea are generally of two types, Bora and Sirocco. Apart from these, any other class of windstorms has negligible importance regarding wave storms, both in frequency and intensity [26]. Sirocco is a humid, warm, and steady wind blowing over the Adriatic basin from SE-SSE. This wind is strongly influenced by the orography as it is channelled along the major axis of the basin by the Apennines and the Dynaric Alps. It blows on most of the length of the basin, usually not very strong, but is able to produce storms in the Central and Northern Adriatic areas [26]. On the other hand, Bora is a cold and gusty, strong, low-level, downslope wind blowing mainly from

NE, across the mountain barrier of the Dinaric Alps. Strong bora events may give rise to structured jets and multiple jet systems flowing through orographic gaps, with strong sub-basin scale spatial gradients across the Adriatic [27,28].

Because of the meteorological scenario above, wave climate in the Adriatic Sea is usually mild or moderate most of the year. However, the severity of wave climate varies throughout the basin depending on the relative importance of the dominant and prevailing winds, Bora and Sirocco, as well as on the fetch available for generating waves. In general, Bora is more intense than Sirocco and is fetch-limited, blowing mainly along the minor axis of the Adriatic, although it can suddenly attain very high speeds. On the contrary, Sirocco may blow over much larger fetches, along the major axis of the basin, and may grow slowly. Furthermore, Sirocco generally reaches the highest speeds in the eastern Adriatic regions and decreases while proceeding to the western coasts [27]. In particular, wind fields in the Central Adriatic Sea are strongly conditioned by the bordering orography, with the wind channelled along the main axis and with the presence of a reduced but still important effect of the transverse component.

In line with these, coastal topography and geometry also significantly influence wave generation by Bora and Sirocco in the Central Adriatic Sea. In particular, wave climate in the Central Western Adriatic Sea is conditioned by the presence of the Conero and Gargano headlands at its northern and southern limits, which significantly restrict the fetch in the longitudinal direction. Accordingly, potential fetches for the study area are larger along sectors oriented around the N and E directions and decrease towards the NE.

Given these wind conditions, waves approaching the Molise coast exhibit a bimodal directional distribution, with two prevailing directional sectors. One of these sectors is roughly represented by the directional quadrant between the NW and the NE, hereinafter referred to as the main wave direction, while the second directional sector extends from the NE to the SE, and is referred to as the secondary wave direction (Table 1). Wave fields approaching from the NE-SE sector are characterized by low and moderate significant wave heights, *Hs* < 3 m, and with the largest percentage of observations corresponding to events with *Hs* < 1 m. The contribution of low and moderate sea states also prevails in the NW-NE directional sector. However, in this case, the sea states may be more severe, with *Hs* values of more than 3 m and up to 6 m, although the frequency of these events is notably low. Nevertheless, the bimodal character of the bivariate distribution of *Hs* and wave direction becomes clearly unimodal and oriented mainly around the NNE subsector for sea states with *Hs* >3m[21]. In this sense, an analysis of the annual maximum significant wave height at the Ortona buoy (Sea Wave Measurement Network, RON) in the period of 1990–2006 reveals that this parameter ranges from 3 to 6 m, approaching from the N-NE directional sector, although the most severe events arrive from the N-NNE sub-sector (Figure 3A). The occurrence of these extreme episodes takes place during the late autumn, winter, and early spring months (Figure 3B). The main wave climate features of the Molise coast, including the Average Significant Wave Height (*Hs*) and the Average Significant Wave Height of sea states exceeding 2 m (*Ht*), as well as their associated periods, are reported in Table 1.

**Table 1.** Main wave climate features estimated for the Molise coast. Average Significant Wave Height (*Hs*) and the associated period (*Ts*); Average Significant Wave Height of events exceeding2m(*Ht*) and the corresponding period (*Tt*).


**Figure 3.** Annual maximum wave storms, directionality (**A**) and timing during the year (**B**) at the Ortona buoy (1999–2006). For the location of the Ortona buoy, see Figure 1.

In correspondence with the directions of the prevailing and dominant waves and the shoreline orientation of the Molise coast, longshore drift occurs in the north–south direction [21,29,30].

Regarding astronomical tides, the study area is microtidal and experiences ordinary tidal excursions of 30–40 cm [21], although the maximum high tide recorded in the tide tables is 0.6 m and the minimum height is –0.2 m, which are referenced to mean lower low water [31]. Sea-level oscillations induced by meteorological conditions (storm surges or meteorological residues) are obtained as the difference between the measured sea level and the predicted astronomical tide. Analyses of meteorological residues obtained from sea level measurements at the Ortona tidal gauge [32] for the period between 1979 and 2019 indicate that storm surge values range approximately between −0.15 m and 0.45 m. Nevertheless, more than 95% of the observations lie in the range of −0.07 m–0.27 m, and the probability of the occurrence of values greater than 0.3 m are less than 0.01.
