Why Adriatic weather can challenge experienced sailors?

After more than 40 years of sailing in different parts of the world, I thought I had developed a sound routine for interpreting weather forecasts before and during a passage. Like many experienced sailors, I would carefully examine the wind forecast, pressure systems, expected gusts and sea state before deciding whether to sail, where to anchor, or when to seek shelter.

Then, on a summer passage to Venice, I learned the important lesson that Adriatic weather can surprise experienced sailors...

During the night crossing of the northern Adriatic, from Pula to Venice, we encountered a violent Nevera early morning while still well offshore. Fortunately, we had sea room around us. As the wind rapidly strengthened in the 50 knots and the storm approached, we decided not to fight it but to bear away and run before the storm in open water under storm jib only. For nearly two hours we stayed well clear of the coast, allowing the worst of the weather to pass before turning back towards the Venetian Lagoon. It was an uncomfortable night, but it ended as a good seamanship story: the crew stayed calm, the boat behaved well, and we reached safely the Venice safely in the San Giorgio marina.

Belisama in San Giorgio marina in the Venice

Looking back, I was satisfied that we had made the right tactical decisions. But the surprise came later...

After a magic quiet night in the Compagnia della Vela San Giorgio marina, encouraged by improving weather and forecasts predicting only moderate winds for the coming night, we decided to anchor using 20 meter of chain in the narrow (50 meters wide)/shallow (5 meter deep) Torcello Canal, north-west of Venice, where we had been very safely using in the past, in order to visit Burano. After the previous experience coming to Venice, it felt as though the worst was behind us. It wasn’t.

Shortly after midnight, a violent convective storm (nevera) swept across the lagoon. The wind built with astonishing speed. Before we had time to respond, our anchor began to drag and the boat was driven sideways towards the shallow bank and their rocks. Within minutes, we were aground on the edge of the canal, unable to start engine because of the shallow rocks, hitting rocks and poles marking the limit of the canal, helplessly watching events unfold faster than we could react. Nothing in the forecast had seemed particularly alarming.

Belisama, the morning after gounding. The picture does not reflect the shaking and banging that occurred all night long!

A few days ago, the same questions came back to mind when several boats were driven ashore during another Nevera at Unije, one of the anchorages we regularly use when sailing from Pula. Many of those crews were almost certainly experienced sailors. Like us in Venice, they probably checked the weather forecast before dropping anchor or picking a buoy there. At 3:45 in the night, a sudden nevera struck the cove with winds over 60 knots. Many boats on buoys or anchor were dragged ashore with major structural damage for some of them.

from Hell in Potkujni. Storm strikes sailors at Unije: moorings torn away and boats crashed onto the rocks

A Croatian sailing friend of mine sent me a picture of a French sailing boat having drifted on shore in the same night, in the Zadar/Šibenik area further south.

A picture sent by a Croatian sailor friend from Šibenik on 21st July. Probably an Amel Santorin 46'

And today, I received the following picture from Zirje, off Šibenik...

I have never seen such an "epidemic'' of grounded boats in the past!

So, what had I failed to understand? It certainly wasn’t seamanship. We had reacted correctly in open water and escaped the first storm without damage. The problem was more subtle. I had been looking almost exclusively at the surface weather wind, pressure and gust forecasts. And that had worked for many years in the Baltic, North sea, Channel and Atlantic. Until the convection becomes one of the dominant weather process as in the northern Adriatic! 

The Northern Adriatic is narrow, enclosed, bordered by mountains, affected by sea breezes and katabatic winds (Bora), influenced by Alpine air masses, and subject to rapid convective development. Weather systems interact over relatively short distances. The atmosphere can change much faster than in many open-ocean environments.

I had not yet learned to ask the questions that experienced meteorologists routinely ask:

• Is the atmosphere unstable?

• Is there enough moisture to sustain deep convection?

• Is there a trigger capable of initiating thunderstorms?

• Can those storms become organised?

• And most importantly, where will they move relative to my boat?

The purpose of this series is not to criticise those decisions, nor to suggest that every nevera can be predicted with certainty. Rather, it is to show that there is another layer of weather information, often available to every skipper, that many of us simply never learned to use.

Learning to read that layer has completely changed the way I will now prepare for sailing in the Adriatic.
In the articles that follow, we will gradually build that understanding, from the large-scale weather systems that shape the Adriatic, to the local triggers that create Neveras, and finally to a practical decision-making framework that any skipper can use before leaving harbour.