Adriatic micro-scale drivers

In addition to synoptic scale situation modified by mesoscale contributions, sailors in the Adriatic should consider the micro-scale drivers that may affect their exposure to local weather conditions while in anchorage. 

These factors may result from the local geography resulting in very local anabatic and katabatic winds as already mentioned in mesoscale drivers. However, these mesoscale drivers may be expressed at very different scales at the local level, not always captured on the local weather forecast. 

Several effect are influencing these factors:

Funnelling/venturi

All of the above can be affected by the local geography. Katabatic winds falling down the slopes may not have enough energy to go over islands elevation they encounter on their way and therefore tend to go around obstacles, funnelling through islands on their way.

This may result in an island looking like offering protection from Bora on a map, but not actually offering it because of a low altitude pathway allowing wind gust to get over the so-called “protected area”.

This is exactly what we encountered in Borovinje cove, as Bora was forecasted and Navily was indicating potential good protection. To be honest, some other posts were mentioning a funnelling effect. We did not sleep the whole night and left fin the following morning. See picture below. 

Anchoring in Borovinje, in a cove supposed to be protected from Bora NE winds.   

Turbulences and reversal

In the lee side of an island: 

• the air may tumble and swirl,
• with rapid changes in direction and speed over short distances.

In conclusion, micro-scale drivers are usually not taken into account in weather forecast but cannot be ignored as they will drive your stay in any precise location.

Synoptic drivers: cold fronts

A cold front is represented by a blue line with triangles oriented in the direction of the front movement. A cold front represents the leading edge of a cold air mass that pushes it way under a warmer, lighter air mass, forcing it to rise rapidly, as a bulldozer effect. This rising motion often creates towering clouds, showers, or thunderstorms, especially if the warm air is moist. As the front passes, there's typically a sudden drop in temperature, a sharp wind shift (often veering), and a quick rise in air pressure. Cold fronts usually move fast and bring abrupt, sometimes violent weather changes, making them especially important for sailors to anticipate. Wind can shift from SE (Jugo) to W or NW in Bora situations.

Example of a cold front moving over England and Britany on 14 July 2025

Synoptic drivers: warm fronts

A warm front is the leading edge of a warm, lighter air mass that slowly rises over a retreating cold air mass. Because the warm air ascends gradually, it forms layered clouds (starting with high cirrus and thickening to stratus), often bringing steady rain or drizzle over a long period. The approach of a warm front is marked by a slow drop in pressure, increasing humidity, and winds that back (e.g., from east to southeast). After the front passes, temperatures rise gently, the rain eases, and pressure stabilizes or rises slowly. Warm fronts usually move slowly and bring more subtle but prolonged weather changes than cold fronts.

Example of a warm front moving eastward across Ireland, https://meteo.hr/prognoze_e.php?section=prognoze_model&param=web_fronte_sutra12

When a warm front passes, the changes are more gradual and subtle than with a cold front, but they still can have a big impact on sailing... 

Mesoscale drivers, understanding regional weather drivers in the Northern Adriatic

When the synoptic map shows nothing special, the real action often comes from local and regional weather drivers.

In the Northern Adriatic, weather conditions are often influenced not just by global and synoptic patterns but by mesoscale drivers, regional-scale systems that operate over tens to hundreds of kilometres. These drivers can change wind strength and direction dramatically over just a few hours or even minutes, especially near coastlines and islands.

Understanding these mesoscale effects is essential for safe and comfortable sailing in this highly variable and geographically complex region.

40 knots bora katabatic wind in Senj, while only 10 knots in Mali-Lošinj, 

from Northeast over the Triest and Senj area on 9 June 2025.

Synoptic scale: understanding global weather drivers

Understanding weather begins at the global level, what meteorologists call the synoptic scale. The word "synoptic" comes from Greek and means "seen together" or "comprehensive." In meteorology, it refers to large-scale atmospheric patterns and interactions that influence the weather over wide areas.

Figure 1: synoptic chart over the Atlantic ocean and Europe, 6 August 2025

Synoptic scale level is the first level to consider when assessing weather before heading at sea. It gives an overview of the large scale drivers such as high and low pressure areas, front positions, clouds, winds, air and sea temperatures...

Setting the global picture: how air moves around the earth

“To understand what’s going to happen next in your sailing spot, you need to know what’s happening around the world.”

When planning a sailing trip, particularly in the relatively enclosed Adriatic, knowing where the wind comes from, where it might go next and what will be the drivers is vital. Most of the winds we experience aren't just random gusts. They are part of a much larger earth’s atmospheric circulation.

Figure 1. Idealised depiction (at equinox) of large-scale atmospheric circulation on Earth, Wikipedia

This post explores how the global engine of wind and weather works, and why it matters every time you raise your sails...

Adriatic weather forecast sites

This page is a compilation of links that I use to explore the weather situation in Northern Adriatic.