The following sources are ranked and described for use specifically in the Saronic Gulf / Aegean region. Use at least two sources before any passage decision. For the Saronic Gulf, POSEIDON and Windy are the primary daily tools; PredictWind is best for multi-day planning.
Run by the Hellenic Centre for Marine Research — the most authoritative and Aegean-specific marine forecast available. Provides sea state, wind, current, and wave models tuned for Greek coastal and island waters. Updated twice daily. The Greek professional sailing community trusts this above all else.
Best for: Aegean-specific wind and sea state accuracy, coastal current patterns, wave height forecasts. The single most important source for this trip.
The best visual interface for multi-model comparison. Layers available: ECMWF (most accurate global model), GFS, ICON, AROME (high-resolution European model — excellent for the Aegean). Switch between models to see where they agree and diverge. Bookmark the link above — it opens centred on the Saronic Gulf.
Best for: Visual situational awareness, comparing multiple model outputs, animated wind and wave overlays. Use AROME or ICON for highest Saronic resolution.
The official Hellenic National Meteorological Service. Provides marine bulletins, synoptic charts, and official Greek forecast products. Marine bulletins are broadcast on VHF and are the legal forecast standard for Greek waters. Check the daily marine bulletin for the Saronic area.
Best for: Official forecasts, frontal system tracking, weather warnings, and VHF-synced marine bulletins. Essential for understanding large-scale patterns.
Professional-grade offshore wind and routing model. Their proprietary PWE and PWG models often outperform GFS and ECMWF in coastal and island waters with complex topography. Subscription required for premium forecasts. Highly recommended for multi-day passage planning where Meltemi onset timing is critical.
Best for: Precise wind onset timing (especially Meltemi), multi-day passage planning, and when ECMWF and GFS disagree — PredictWind models often resolve the ambiguity.
Integrated wind and tidal stream overlays within the chart view. Convenient for a quick check on-passage without switching apps. Wind data sourced from the Navionics weather service (GFS-based). Tidal stream arrows are particularly useful for planning the Poros Strait transit.
Best for: Quick on-passage wind checks integrated with chart view, tidal current arrows in the Poros Strait, harbour approach wind direction visual.
The European Centre for Medium-Range Weather Forecasts — the gold-standard global numerical weather model. The ECMWF IFS model underpins most professional marine forecasts worldwide. Not a user-friendly consumer interface, but accessible via Windy.com (select ECMWF as the model layer). Reliable to 7 days; best in class at 3–5 days.
Best for: Most accurate 3–7 day global forecast foundation. Access via Windy or PredictWind rather than the ECMWF website directly.
The Aegean Sea and Saronic Gulf exhibit a very small tidal range, typically 20–40cm (spring tides rarely exceeding 40cm). Tide type is semi-diurnal mixed — two highs and two lows per day, with varying inequality between them. For practical purposes, tides are not a safety concern on this route. However, tidal currents in narrow channels can be relevant, and shallow anchorages should be checked at the lowest predicted water level.
Tidal currents in open water are weak, generally below 0.5kt. In the Poros Strait (narrowest point approximately 200m), current can reach up to 1kt and is the only tidal current of operational significance on this route. Direction should be checked before transit — it does not substantially affect passage timing but knowing the set helps with boat handling in the narrows.
| Stop | Tidal Range | Tidal Current | Anchoring Note | Practical Impact |
|---|---|---|---|---|
| Alimos Marina | 20–35cm | Negligible (<0.2kt) | Med-moor — tides irrelevant | None |
| Perdika / Aegina | 20–35cm | Negligible | Quay or anchor — minimum 2.5m. Range too small to matter. | None |
| Poros Strait | 20–40cm | Up to 1kt | N/A (transit only) | Note direction before entry. Ebb = S, Flood = N. Does not affect passage safety but assists boat handling. |
| Poros Town | 20–35cm | Slight at quay | Quay stern-to — depths 3–5m. Negligible range. | None |
| Ermioni Bay | 15–30cm | Negligible | Anchor 5–10m. Range too small to affect scope calculation. | None |
| Hydra Harbour | 20–35cm | Negligible | Water taxi wash is more relevant than tidal range at Hydra. | None from tides. Monitor ferry wash. |
| Bistiou Bay | 20–35cm | Negligible | Anchor 5–6m sand. 5:1 scope regardless — range too small to require adjustment. | None |
Note: For the most accurate tidal predictions for this trip, use the Navionics tidal overlay or query the POSEIDON portal for tidal stream data. The EMY also publishes annual tide tables for Greek ports.
All times local EEST (UTC+2). Sunrise/sunset computed for Athens (37.97°N, 23.72°E). Civil twilight end = when it becomes fully dark and navigation lights should be operating. July days are extremely long in Athens — over 14.5 hours of daylight. You will never need to sail in darkness on this trip if you follow the passage plan.
| Date | Day | Sunrise | Sunset | Day Length | Civil Twilight End |
|---|---|---|---|---|---|
| 4 Jul | Sat | 06:05 | 20:51 | 14h 46m | 21:22 |
| 5 Jul | Sun | 06:06 | 20:50 | 14h 44m | 21:22 |
| 6 Jul | Mon | 06:06 | 20:50 | 14h 44m | 21:21 |
| 7 Jul | Tue | 06:07 | 20:49 | 14h 42m | 21:21 |
| 8 Jul | Wed | 06:08 | 20:49 | 14h 41m | 21:20 |
| 9 Jul | Thu | 06:09 | 20:48 | 14h 39m | 21:19 |
| 10 Jul | Fri | 06:09 | 20:47 | 14h 38m | 21:19 |
| 11 Jul | Sat | 06:10 | 20:46 | 14h 36m | 21:18 |
Even our earliest departure (07:00 on Day 7) is a full hour after sunrise. Civil twilight ends after 21:15 every night — dinner ashore and sunset drinks are always possible. Navigation lights must be shown from sunset onward if underway.
Complete this briefing each morning before departure. Sources: POSEIDON + Windy minimum. Share findings verbally with crew at breakfast. The decision field (GO / WAIT / MODIFY) should be stated clearly and logged.
To be completed before each sailing day by the skipper
The Meltemi (Greek: Μελτέμι) is the dominant meteorological feature of Aegean summer sailing and will define almost every decision on this trip. It is a seasonal dry NW wind driven by a persistent thermal low over Turkey and a high over the Balkans, accelerated through the funnel shapes of the Aegean island groups. Understanding its rhythm is more important than any other piece of weather knowledge for this trip.
Typical pattern in July: Light to calm early morning (06:00–09:00). Wind begins to fill in from NW 5–10kt by late morning (09:00–11:00). Builds steadily through midday to 15–20kt by 13:00–14:00. Peaks at 15–25kt in the afternoon (14:00–18:00). Dies at or shortly after sunset. Repeats consistently for days at a time when established.
In the Saronic Gulf specifically: The Saronic is more sheltered than the open Aegean or Cyclades. The Meltemi is moderated by the surrounding mainland and islands. Expect 10–20kt rather than the 25–35kt that is common in the Cyclades. However, in a strong Meltemi period (e.g. NW pressure gradient >5hPa) even the Saronic can see 25kt+ in exposed areas. The key exposed stretches on our route are the open crossing from Aegina to the Methana/Poros area (Day 3) and the return passage north toward Alimos (Day 7).
Core strategy: own the morning. Every departure on this trip is scheduled in the 07:00–09:00 window. Short passages (Day 5: 10nm) are so fast in the morning that the Meltemi is irrelevant by the time we arrive. Longer passages (Day 7: 30nm) use the morning calm as a tactical resource and accept motoring for the second half.