Hurricane Danielle: latitude, summer without a cyclone… Why is the storm formed in the North Atlantic exceptional?

The alert is gone from a Spanish meteorologist, which announced Thursday, September 1 on Twitter to be concerned about abnormal activity intensity in the North Atlantic. A storm was forming, which could eventually take the direction of Spain, even from France. This Friday, the meteorological agencies, starting with Météo France, confirmed the importance of the storm spotted by the scientist, exceptional in more ways than one.

A “remarkably north” latitude

What struck Météo France right away was the “remarkably north” latitude at which the storm formed, baptized Danielle: “West of the Azores, at 38.1° N”, details the agency in an article. As she later clarifies, “rare are the systems forming at such a north latitude in the basin”. Rare, the word is weak: “On the history of NHC data (National Hurricane Centereditor’s note), less than 2% of the systems form further north”, adds Météo France.

The phenomenon, therefore extremely rare, can nevertheless be explained: it stems from the fact that this “low pressure zone” evolved “on abnormally warm waters” in this geographical sector. The temperature there was “around 26-27°C”, at values ​​usually measured in the tropics, the much more common cradle of these tropical storms.

An almost virgin summer

The other point that concerns meteorologists is that the formation of this storm Danielle occurs at the end of a summer which shone by the absence of similar phenomena. Nothing suggests that there is a cause and effect link there, but storm Danielle, as its name suggests (4th letter of the alphabet, editor’s note) is only the 4th tropical storm to make its appearance this season.

“The 2022 season started on June 2 with the formation in the Gulf of Mexico of a tropical system which became, on June 5, over the Atlantic, the tropical storm Alexafter crossing Florida”, explains Météo France. Since then? Only two storms, “Bonnie and Colin, respectively on July 1 and 2”, which were “short-lived”. So two whole months have passed without the slightest formation of storm, with in particular an immaculate month of August.

And it is an understatement to say that this finding is extremely rare, since it has only been made twice according to NHC data. A first time in August 1961 (“the season had subsequently been very active”, notes Météo France), and another in 1997, “where the whole season was not very active”, specifies the French agency again.

Storm Danielle could mark a real starting point for a series of tropical storms, “since in addition to Danielle, the NHC is following two other potential systems” this weekend, located further south.

Uncertain trajectory

Despite the exceptional nature of this storm, which therefore became a hurricane this Friday, September 2 around 5 p.m. (French time), forecasters are cautious about the sequence of events, and in particular its trajectory. Storm Danielle is indeed moving at a very slow pace so far, not facilitating the work of meteorologists.

Many scenarios are therefore still possible regarding its future direction. “It should head northeast in the coming days, but many uncertainties remain associated with the forecast of its trajectory,” said Météo France. If it were indeed heading towards the northeast, this would undoubtedly sign the end of its potential danger for the European continent, since by encountering colder waters, it would quickly lose intensity.

But a trend sends it – in an equally uncertain way nevertheless – towards the East and the European coasts. To be continued…