The extremely active 2020 Atlantic hurricane season has burned its way through the alphabet with 30 named storms including 14 hurricanes and 7 majors.
The two seasonal hurricane predictions that I trust the most are from the state of Colorado under the direction of Dr. Phil Klotzbach and the NOAA Climate Prediction Center. Both outfits have a long track record of accuracy, experience, and transparency.
State of Colorado
17 named storms, 8 hurricanes, 4 major hurricanes, ACE = 150
NOAA outlook
13-20 named storms [Ana through Victor]
6-10 hurricanes, 3-5 severe hurricanes, ACE = 110% – 190% of median (130)
Historical context of the 2020 season
In 2020, the Accumulated Cyclone Energy (ACE) was approximately 185 units – a metric of storm and seasonal activity that combines intensity and duration. It’s pretty easy to calculate ACE: square the recommended wind speed and add it 4 times a day. The simplest example is a severe Category 3 hurricane at 100 knots for 1 day = 4 units of ACE. A tropical storm at 35 knots for 1 day has only 0.49 units of ACE. More intense storms will power up the ACE, particularly the giant open ocean hurricanes on a 10-day course from the coast of Africa and around the Bermuda high.
The 2021 season forecast of CSU = 150 and NOAA = 140-250.
In the past 50 years, in 1995, the Atlantic Basin went from an inactive to an active era. In fact, the mean ACE doubled from 68 to 135 between the two periods. There are several theories for changing Atlantic hurricane activity including the Atlantic Multidecadal Oscillation (AMO) and the reduction of aerosols against the backdrop of anthropogenic global warming. When will the AMO cycle soon shift back to a colder state with inactive hurricane activity? I would go for 2030.
Next 7 days
No tropical storm activity is expected in the Atlantic. That’s no surprise considering it’s early June and we don’t see much activity climatologically – even in the extremely busy season.
Week 2
If you look at the ECMWF ensembles around mid-June, there is an air of activity in the Gulf of Mexico. Here sea temperatures are very warm, but wind shear is usually high, making storms one-sided and difficult to develop.
The chances of development for something – a named storm – are likely in the 10-20% range right now. We will have plenty of time to see the stormy GFS model and its ensembles. The 2021 season will have two fully comparable ensemble systems from ECMWF and NOAA for medium-term hurricane forecasting. In the end.
The weather models published here are from a subscription service, which is aptly named “Weather Models,” and costs about $ 10 per month annually. Of course there are plenty of free resources on the internet today, but I would be flying blind if I didn’t have access to the best of everything.
Updates ahead I will update this newsletter daily until the end of the hurricane season. I still have to find out the schedule. But I have a lot of other weather and climate-related topics to cover while we wait for the hurricane season to heat up – and it sure will.
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