1.4.3 Give evidence from the synoptic weather map that the South Atlantic \( (1 \times 2) \) hlgh is ridging.

To identify evidence that the South Atlantic High is experiencing ridging on a synoptic weather map, you should look for specific features related to the arrangement and shape of isobars (lines of equal atmospheric pressure). Here are the key indicators: 1. **Bulged Isobars Extending Northward:** - **Shape of Isobars:** In the area of a ridge, isobars will bulge outward from the center of the high-pressure system. For the South Atlantic High, this means you'll see isobars extending northward into lower latitudes. - **Arching Pattern:** The isobars will form a pronounced arch or ridge shape, indicating an extension of high pressure into regions that might otherwise be influenced by lower pressure systems. 2. **Elongated High-Pressure Area:** - **Stretching of the High:** The South Atlantic High will appear more elongated than usual, rather than being compact. This stretching is a hallmark of ridging, showing that the high pressure is extending its influence over a broader area. 3. **Reduced Pressure Gradient:** - **Spacing of Isobars:** During ridging, the isobars near the ridge will be spaced farther apart compared to other regions. A reduced pressure gradient indicates weaker winds and more stable atmospheric conditions associated with high pressure. 4. **Subsiding Air Indication:** - **Weather Conditions:** Although not always directly visible on a synoptic map, ridging is typically associated with subsiding (sinking) air, leading to clear skies and stable weather. If the map includes weather symbols, fewer cloud symbols or indications of clear weather near the South Atlantic High support the presence of a ridge. 5. **Jet Stream Bending:** - **Jet Stream Position:** If the synoptic map includes jet stream trajectories, a ridge in the South Atlantic High would typically correspond to a southward bend (positive tilt) in the jet stream. This bending allows the high-pressure ridge to extend further north. **Example Illustration:** Imagine a synoptic map where the South Atlantic High is centered around 30°S, 40°W. If there is a bulge in the isobars extending northward toward 20°S, with the isobars arching outward in that direction, this bulge signifies ridging. The isobars around the bulge would be more spaced out, indicating a stronger, more stable high-pressure area extending into lower latitudes. **Summary:** On a synoptic weather map, ridging of the South Atlantic High is evidenced by isobars that bulge or extend northward from the high-pressure center, forming an arch-like pattern. This shape indicates an elongated, stable high-pressure system influencing a broader area, typical of ridging conditions. **Visual Aid:** While I can't provide a visual map here, envision isobars around the South Atlantic High curving outward toward the north, creating a ridge-like protrusion from the main high-pressure area. This visual pattern is the primary evidence of ridging. --- *Note: Understanding synoptic maps involves recognizing patterns in pressure systems. Practice by examining various weather maps to become familiar with identifying ridges, troughs, and other key features.* **References:** - Meteorological textbooks on synoptic analysis - Online resources explaining high-pressure systems and ridging ---