Hello Gonzalo

Wait a minute. A hurricane? Spit out the morning coffee. How did that happen?

A few days ago, a small depression was working its way across the tropical Atlantic.

NOAA’s National Hurricane Center didn’t think much of this depression. Ten percent chance they told us. I swear – if they used emojis, it would have been the laughing emoji. Then, the next day, this one: 😬. The grimace. Suddenly the chance of it forming into a tropical storm was 40%. Then 80%.

I stared at the numbers. What had happened? The storm’s warning went from a shrugging ‘no way’ to: ‘of course there’s a storm coming’. In the matter of hours.

Yeah NOAA, use your emojis. Still, the source of confusion is clear. The weather models which NOAA uses and extrapolates for its forecasts have been largely in disagreement with each other.

Weather models are almost an algorithmic art form. Here, yachties tend to the GFS American-based model, and the European model, ECMWF as the most accurate. There is always debate as to which is the better forecaster. Generally people say the European one is superior. At least the Europeans do!

Apparently this is because it has more modern computers. Better algorithms. Though I keep hearing that the American GFS are also updating their systems.

At the moment, both models are at a forecasting divide. The consensus is this is a powerful, if small storm. It was named Tropical Storm Gonzalo yesterday and may be upgraded to a hurricane as it gets closer to the Eastern Caribbean in the next 24 hours. It has indeed taken everyone by surprise.

Suddenly, there is a hurricane watch for our beautiful Barbados. And St.Vincent and the Grenadines. Somewhere this Saturday there is rain and potentially catastrophic wind coming – though no one knows exactly where it will make landfall in the Windward Islands chain. Martinique is in the northern part of the Windward chain. Right now – just on the edge of the projected path.

Why is there such uncertainty? Partly because Gonzalo is a small cyclone and this itself is apparently unpredictable. Like a little race car – one of the veteran forecasters has called this storm. Unlike a huge 18-wheeler, he can change direction and speed fast.

Then, there is still lots of dry air on this eastern side of the Atlantic from all the recent Saharan dust which came across in the trade winds last month. So even though the sea surface is a whoppingly warm 29C, hurricanes don’t like dry air. This may be enough to halt and dissipate Gonzalo. A sub-tropical ridge from the north is also starting to hold the storm in place.

A last thing making Gonzalo’s path uncertain is the lack of real-time data from commercial aircraft. I never knew it before, but apparently passenger planes provide much meteorological information. This improves the algorithms of most forecasting models.

Right now, because commercial flights are still so limited, apparently this kind of data is up to 90% down. Aha. Meanwhile, we watch. Ready to move quickly if we have to.

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