The Global Sumud Flotilla carrying aid to the Israeli-blockaded Gaza Strip departed Barcelona again on Monday evening, several hours after poor weather forced it to return to the Spanish port, according to a journalist travelling on one of the boats.

Earlier on Monday, the flotilla – which had set off from Barcelona on Sunday – said in a statement on X that strong winds of more than 30 knots (55.6 kilometres per hour, or 34.5 miles per hour) on the Mediterranean Sea could have posed a problem for smaller boats in the convoy.The flotilla said that it conducted a sea trial and made the decision to return to port in Barcelona to allow the storm to pass.

Mauricio Morales, a journalist reporting for Al Jazeera from on board the Alma boat, said that the flotilla began moving out from the port again at about 7:30pm local time (17:30 GMT) on Monday following a general meeting of all volunteers.The flotilla comprises dozens of small civilian vessels carrying volunteers and humanitarian supplies.

It planned to meet up with a second wave of vessels in Tunisia on Thursday, but that plan has now been slightly delayed.

This is the third aid flotilla of its kind in recent months to attempt to break the Israeli siege on Gaza. Previous attempts have been unsuccessful, with Israeli naval forces illegally intercepting the boats in international waters.

Organisers said the Global Sumud Flotilla is the largest maritime mission to Gaza, bringing together more than 50 ships and delegations from at least 44 countries. Other than the 20-some boats leaving Barcelona, more are expected to join from across the Mediterranean in the coming days, including from Tunisia and Sicily.

This flotilla is organised by four major coalitions that have participated in previous land and sea efforts to Gaza: the Global Movement to Gaza, Freedom Flotilla Coalition, Maghreb Sumud Flotilla and Sumud Nusantara.

Volunteers hail from countries that include Australia, Brazil, Colombia, South Africa and numerous European states. According to organisers, participants are unaffiliated with any government or political party.

On board the flotilla are Swedish climate activist Greta Thunberg, Brazilian activist Thiago Avila, former Mayor of Barcelona Ada Colau Ballano, Irish actor Liam Cunningham and Spanish actor Eduard Fernandez.

Many of the people involved have been part of past flotilla efforts.