Satellite reading, August 29 to September 4

Where to go to avoid sargassum seaweed

Most sargassum coverage reports the disaster. Very little of it answers the one question you have when a holiday is booked and paid for: where do you go so it is not on your beach? I have lived on Roatán since 2014 and I measure the algae by satellite, destination by destination. Here is what the data says, with its date and its method.

What the satellite sees, destination by destination

Over August 29 to September 4, the satellite saw algae across 18.2 % of the zone off Roatán, against 73.1 % off Cozumel. 4 times less, over the same week, with the same method.

The satellite map, week by week Floating algae density, August 29 to September 4
Atlantic sargassum belt seen from satellite, August 29 to September 4. The band crosses the ocean, climbs through the Lesser Antilles and pushes into the Yucatan channel. Blue is clear water, green to red is floating algae.

Drag to move · ctrl + scroll to zoom · double-click to zoom in

Blue = clear water. Green to red = floating algae. Roatán sits west of the belt, behind Honduras. Map by the USF Optical Oceanography Laboratory · USF SaWS · Open the full-size map

Reading of August 29 to September 4

Share of the zone where algae is detected, August 29 to September 4
Destination Country Algae detected Last week
Riviera Maya Mexico 78.6 % 61.4 %
Cozumel Mexico 73.1 % 54.5 %
Punta Cana Dominican Rep. 47.3 % 39.4 %
Samaná Dominican Rep. 34 % 62.6 %
Cancún Mexico 30.6 % 25.4 %
Guadeloupe Guadeloupe 30.4 % 20.6 %
Sosúa Dominican Rep. 29.9 % 26.2 %
Guardalavaca Cuba 25.1 % 11.3 %
La Romana Dominican Rep. 22.3 % 37 %
Runaway Bay Jamaica 20.6 % 10.2 %
Roatán Honduras 18.2 % 0 %
Juan Dolio Dominican Rep. 17.7 % 31.7 %
Barbade Barbados 15.5 % 1.6 %
Varadero Cuba 14.5 % 25.8 %
Martinique Martinique 9.9 % 5.1 %
Sainte-Lucie Saint Lucia 7.3 % 3.2 %
Saint Martin Saint Martin 3.7 % 0.6 %
St Kitts St Kitts & Nevis 3.5 % 2.5 %
Bequia St Vincent 3.4 % 0.5 %
Anguilla Anguilla 3.4 % 0.5 %
Grenade Grenada 2.9 % 2.7 %
Providenciales Turks & Caicos 2.6 % 1.9 %
Curaçao Curacao 1.3 % 0.2 %
Grand Cayman Cayman Islands 0.9 % 1.3 %
Antigua Antigua 0.4 % 1.7 %
Aruba Aruba 0.2 % 0 %
Barú Colombia 0 % 4.9 %
Grand Bahama Bahamas 0 % 0.3 %
Great Exuma Bahamas 0 % 0.7 %
Bermudes Bermuda 0 % 0.3 %
Cayo Coco Cuba 0 % 3.4 %
Cayo Santa Maria Cuba 0 % 5.3 %

Source: NOAA AOML, AFAI. Measures floating algae offshore, not sand on the beach.

Source: NOAA AOML, AFAI index. Method: AFAI index, satellite, share of pixels where the algae is detected. The reading covers the seven-day window of the satellite composite, not a smeared average. Each destination has a fixed box offshore of its beach, and it is the same box from one reading to the next, so the numbers compare to each other.

A measurement is not a promise. It says what the satellite saw that day.

Why Roatán gets so little of it

This is geography, not luck. The raft forms in the tropical Atlantic, drifts up toward the Lesser Antilles, then pushes northwest and funnels into the Yucatán channel. That corridor is what lands seaweed on Guadeloupe, Martinique, Cancún and the Riviera Maya.

Roatán sits southwest of it, in the western Caribbean. The main current runs north of the island. The beaches travellers actually use, West Bay and West End, face west and northwest, sheltered from the swell that carries the algae. That is also why the reef there is reachable straight from shore.

This geography does not change from one year to the next, which is what makes the measurement worth something. It describes a stable situation, not a lucky season.

When the season starts, and when it drops

The Atlantic belt builds in spring and peaks in summer. Winter is the quietest window across most of the region, which happens to be when North Americans travel south.

I am not going to hand you a curve per destination today. My own readings have just started, a curve needs several months before it means anything, and publishing seasonality drawn from three measurements would be inventing it. It will appear here once it is measured, carrying its date like the table above.

How I pick a beach for my travellers

The satellite gives you the zone, not the beach. Between two hotels two kilometres apart, the way the bay faces changes everything: a headland that cuts the swell keeps one beach clean while the next bay over collects all of it. That is not something you learn from a map, you learn it by living there.

Three things I look at before recommending a resort: which way the beach faces, whether a point or a reef breaks the swell before it arrives, and what the hotel actually does when algae shows up. That last one cannot be measured by satellite. You find it out by talking to people on the ground.

If you are torn between two resorts, send me your dates. I will tell you what the data shows for that window and what I know about each beach, then put a quote together if the destination suits you. I work in English, French and Spanish.

The rest of the island, and the resorts

Sargassum does not hit everywhere the same way, and the measurement above is only the starting point. Where to go next:

The webcams are the honest companion to this page. The satellite tells you the month, the camera tells you the morning.

Sargassum questions, answered

Which Caribbean islands get the least sargassum?

Coasts that face west and sit outside the main current get far less than the eastern face of the Lesser Antilles and the Yucatán peninsula. Over August 29 to September 4 the satellite read 18.2 percent of the zone off Roatán against 73.1 percent off Cozumel. That is a measurement, not an opinion, and it can be replayed.

Why does Roatán get so little seaweed?

The raft drifts up from the tropical Atlantic, enters through the Lesser Antilles and pushes toward the Yucatán channel. Roatán sits southwest of that corridor, in the western Caribbean, and its resort beaches face water the main current does not sweep.

When is sargassum season in the Caribbean?

Arrivals follow the Atlantic belt, which builds in spring and peaks in summer. Winter is the quietest window across most of the region. A per destination curve needs a run of readings, and I publish mine as it accumulates.

How is the measurement made?

It comes from NOAA's AFAI index, which spots floating algae by satellite. For each destination I set a box offshore of the beach and count the share of pixels where algae is detected. The same box is used from one reading to the next, so the numbers compare to each other.

Can I book a trip based on this page?

The measurement says what the satellite saw on a given date. It does not promise a clean beach the day you land. Send me your dates and I will tell you what the data shows for that window, then put a quote together if the destination suits you.

Want to know what it looks like for your dates?

Give me your window and your destination. I answer with the measurement for that period, then a quote if it suits you. Fast reply on Messenger, in English, French or Spanish.