Record-breaking 2020 Atlantic Hurricane Season Ends

1 12 2020

Dale C. S. Destin|

Five tropical cyclones present in the Atlantic – September 14, 2020

The busiest Atlantic hurricane season ever ended last night. The season produced a record-breaking 30 named storms. It also produced 13 hurricanes, the second highest on record dating back to 1851. Further, there were six major hurricanes, Category 3 and over, which tied for the second highest on record. The record season took over 400 lives and caused over US$41 billion in damage.

Only once before a season exceeded 20 named storms – 2005 with 28 named storms, which is the record eclipsed by 2020. However, 2020 remains second to 2005 with respect to the number of hurricanes – 15, and the number of major hurricanes – 7. Six other seasons have a similar total of major hurricanes as 2020 – 2017, 2004, 1950 1996, 1933 and 1926. An average hurricane season has 12 named storms, 6 hurricanes and 3 major hurricanes.

Ranking of the 2020 hurricane season based on number of named storms, hurricanes, major hurricanes and ACE, compared to the records

Although the most eye-catching statistic for a given season is the number of storms, this is not the metric used to determine its overall activity. The Accumulated Cyclone Energy (ACE) index is the internationally accepted metric used to categorise the activity of a season. The ACE takes into consideration not only the number of named cyclones but also their strength and duration. Hence, based on the ACE, 2020 is the 13th most active hurricane season on record, with an ACE index of 180. The most active hurricane season on record remains 1933, with an ACE of 259, 44% more than 2020.

Based on NOAA’s classification, the 2020 season was extremely active or hyperactive. However, NOAA’s classification of season has its challenges, allowing for one season to simultaneously have two classifications. A better approach is to classify seasons strictly by the ACE index. This approach would make the 2020 season and above normal season but NOT well above normal or hyperactive, according to 268Weather’s classification. It fell short by seven ACE needed to take it to 187 – 268Weather’s current threshold for a hyperactive season.

268Weather’s seasonal hurricane forecasts accurately predicted a very high likelihood of an above-normal or active season. 268Weather is proud to be among the few to have gotten the forecast right from very early – April. 268Weather was the only entity to forecast over 28 names storms, up to 32 were predicted and 30 formed.

Animated satellite imagery of the named storms that occurred during the 2020 Atlantic Hurricane Season – May 13 through November 18. Credit: NOAA Satellites

It was a relentless hurricane season. It kept forecasters on their toes continuously. There was an average of 4-5 tropical storms per month since June with one forming about every week. Thankfully, we were not significantly impacted by any of the season’s two-and-half dozen named storms, over a dozen hurricanes and half dozen major hurricanes. Also, the Eastern Caribbean virtually got away “scot free” from significant impacts.

The 2020 season got off to an early start with Arthur on 16 May and Bertha 27 May. From May to July, there was a record nine storms. This is more storms than 80 of the previous 169 seasons, including 2014, 1997 and every season from 1991 to 1994. By September 18, the 21-name Atlantic list was exhausted when Tropical Storm Wilfred formed. Thus, the season “went Greek” i.e. the backup Greek List was turned to for names for the remainder of the season. To date, we are 9 names deep into the list with Iota being the last and the most powerful Atlantic hurricane for the year.

The Atlantic has done a 5-peat – produced five active/above normal seasons in a row. This is the longest such streak, on record. Further, it’s the most active hurricane season since 2017 and the second most active since 2005. Eighteen of the last 26 hurricane seasons, dating back to 1995, were above normal.

The reason for the large percentage of active hurricane seasons since 1995 is due to the positive or warm phase of the Atlantic Multidecadal Oscillation (AMO). Positive phases of the AMO are strongly linked to active eras of Atlantic hurricane seasons, which historically last for about 20 to 40 years.

Like other active years, this year’s activity is owed to an interrelated set of oceanic and atmospheric conditions linked to the warm AMO, such as warmer-than-usual North Atlantic sea surface temperatures (SSTs) and cooler-than-normal middle to eastern equatorial Pacific SSTs i.e. La Nina. These conditions which are also associated with weak wind shear caused the record-breaking, extremely active hurricane season.

Other notable records set by the 2020 season include the following:

  • Twenty-seven tropical storms broke the record for the earliest formation by number
  • A record 10 tropical cyclones rapidly intensified, tying 1995
  • This season is the record sixth consecutive year with pre-season named tropical cyclones
  • A record 10 tropical cyclones were named in September with 9 having their origin in the month, the most for any month
  • Iota became the only Category 5 hurricane to have its origin in November and the latest on record

For more details on the 2020 Atlantic hurricane season, our monthly summaries: May, June, July, August, September, October and November (coming soon).

This season has officially ended, but it is possible, although not probable, for additional storms to develop. Stay vigilant and make sure your family is prepared for all hazards, especially those related to weather and climate. The 2021 hurricane season will officially begin June 1 and 268Weather will issue monthly forecasts starting early April.

Hurricane Irma Got Relegated

17 03 2018

Dale C. S. Destin |

Hurricane Irma was relegated from being tied for the second strongest Atlantic hurricane, in terms of wind speed, to being tied for being the third strongest. This is according to the final report on the system issued last week by the U.S. National Hurricane Center (USNHC). The USNHC, in its post-mortem report, lowered Irma’s maximum sustained winds from 185 mph to 180 mph.


VIIRS Satellite Image of  Hurricane Irma When it was at its Peak Intensity and Made Landfall on Barbuda at 0535 UTC (1:35 am) 6 September, 2017.

The downgrade of Irma, by 5 knots (5.75 mph), is relatively negligible; however, from the record book standpoint, it is notable. And looking at the raw data, the USNHC may have still been generous with the peak winds of 180 mph – it could have been lowered further.

There are some other notable things gleamed from the report that I would like to share. A report I would recommend persons to read.

Recall that many persons blamed Irma on climate change, something that I and others continue to debunk? It turned out that Irma’s strength had very little to do with warm sea surface temperatures – the link that is being made to climate change, and more to do with low wind shear and available atmospheric moisture, according to the USNHC report – not climate change.

USNHC has confirmed what we already recognized – Irma was a very small hurricane. Her hurricane force winds extended only 24 km (15 miles) from the centre. On average, the hurricane force winds from a hurricane extends out 64 km (40 miles). Her small size saved Antigua from similar type destruction to what occurred in 1995 from Hurricane Luis.

Along parts of the track of Irma, the effect of the winds on the sea was reminiscent of a tsunami. For example, in Puerto Piloto, the sea retreated offshore by up to 12 metres (39 feet) due to the force of the southerly winds on the eastern side of Irma’s circulation. No doubt similar would have happened for parts of Barbuda and elsewhere.

Irma's Storm-Surge as Recroded by Our Station at River Road, Codrington, Barbuda

Irma’s Storm-Surge as Recorded by Our Tide Station at River Road, Codrington, Barbuda

For Barbuda, the was a tsunami-like surge of 2.5 metres (9.3 feet) measured by our tide gauge at River Road, Codrington, which is on the southern side of the island. It is likely that the surge generated by on the north side was higher. These surges inundated significant portions of Codrington and the island as a whole, which is very flat. At least half of the island lies within 25 feet of mean sea level. The Codrington Lagoon remains breached from the massive surges and waves created by Irma.

In addition to the tsunami-like surge, there were monster waves as high as 8 metres (26 feet) caused by Irma. Such large waves on top of the high surge would have caused seawater to inundate areas well inland, causing serious erosion and saltwater intrusion into aquifers and agricultural lands.

Also confirmed was the fact that the ECMWF was by far the best performing model with respect to the track forecast. However, all the models were left wanting with respect to the forecast of intensity.

In weeks we will have the first set of forecast for the upcoming hurricane season, stay tuned for those.

Don’t forget to take our weather survey, which will help us to better communicate the weather to you: Weather Survey.

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