This grid of data for tropical cyclones in the North Atlantic took a bit of figuring out. It shows years along the Y axis the years from 1950 to 2020, and along the X axis dates, from the start of June till the end of November. In the cells is a single letter for the first occurrence of the tropical cyclone that has reached tropical cyclone category and been given a designator, they remain blank where a tropical storm has not occurred yet. The American only began giving tropical cyclones names since 1950 so that’s why the table of nearly 14,000 daily cells starts late. This has to be one of the weirder statistics I have ever had to visualise and I did it in response to the many articles claiming that 2020 was the earliest year that a ninth tropical cyclone had been named. To be honest I didn’t doubt that this year had been the earliest but I had to prove it for myself because I’m naturally skeptical about these things! I don’t think it’s the best way to gauge how active a season has been, that’s surely the running ACE total, which not only measures the longevity of all cyclones but also intensity.
What I think has happened since the start of the satellite era is that the NHC have become more and more proficient at identifying nascent tropical cyclones with an ever expanding number of tools, such as more sophisticated satellite sensors, sophisticated NWP models, doppler radar, six hourly reconnaissance aircraft and drop sondes plus a network of ocean weather buoys. This has lead to a bulge in the number of early tropical cyclones this year, many of which have not matured into full blown hurricanes and remain tropical storms.
As far as I can see on provisional data I’ve scraped from the NHC, 2020 stands in nineteenth position as of the 3rd of August using the running ACE metric. It may have thrown up more named storm for this date than any other season, which in itself is interesting because why is that? And why don’t they continue to develop into hurricanes?
What happens if we run out of names?
According to the National Hurricane Center website “In the event that more than twenty-one named tropical cyclones occur in the Atlantic basin in a season, additional storms will take names from the Greek alphabet.” It happened before in 2005 when six of the twenty seven storms were given a Greek letter. At the rate this season is going it looks likely that this will happen again. Buggar – I’ve just realised that I didn’t take more than twenty one storms in a season into account and may well have to rewrite some of my code – it’s not easy being a xmetman.