Joe D’Aleo CCM, Weatherbell.com
The 2020 hurricane season in the Atlantic Basin is the most active in history with 30 named storms, breaking the previous record set in 2005 (which had 28). 6 storms were major storms including Iota, setting a record for the latest Major hurricane.
The Gulf and Central America were hard hit, reminiscent of the 1988 to 1900 period (see).
Despite the busy Atlantic, the Pacific was quiet and the hemisphere as a whole had a quieter than normal (80% of normal) season.
The ACE of 179.8 ranks 13th behind 2017 and 2005 and the top year 1933.
An active season was expected -‐ several factors pointed to it. LA NINA AND LOW SHEAR IN THE ATLANTIC
We have a La Nina in place.
Gerry Bell showed how La Ninas produce fewer east Pacific storms and less shear to the east which favors more Atlantic storms.
Weak easterly shear is seen in the Main Development region and Caribbean consistent with persistent La Nina Pacific suppression.
2017 was a no shear year with a much higher ACE (ranked 7th with
224.9 versus 179.8 so far in 2020). Strong westerly shear was seen from 2014 to 2016.
The pressure anomalies reflect the low pressure and storm tracks beneath the 40N ridge.
WARM ATLANTIC MODE OF THE AMO
The Atlantic is warm.
The warm Atlantic not surprisingly generates more storms.
In the figure above, the red columns represent the seasonal AMO and black lines the number of Atlantic names storms
LOW SOLAR AND COLD HIGH ATMOSPHERE
Hodges and Elsner (FSU) found low solar led to colder high atmosphere favoring more instability and perhaps stronger storms.
Indeed check out the 100mb temperature anomalies since July in the Atlantic Basin including the Caribbean.
So we had the ‘perfect storm’ in the Atlantic Basin with a La Nina leading to low vertical shear, the warm mode of the AMO providing more heat energy and low solar leading to a colder high atmosphere and greater instability. Even with the large number of storms and 6 majors, the ACE index still trails years like 2017 and 2005 and 10 others.
Not every meteorologist believes 2020 holds the record for most named storms. Due to advances in technology, forecasters are able to identify smaller subtropical storms that may have gone unnoticed in the past.
“When one wants to do a fair comparison of storms now versus storms in the past, you really have to be careful about how to interpret the raw number,” Christopher Landsea, chief of the tropical analysis and forecast branch at the National Hurricane Center, said, according to the New York Times. “There has been a lot of hype about the record number of storms and, yes, it’s been a busy year. There have been horrific impacts. But is this really a record? The answer is no.”
The ACE supports that. And the decadal trend for landfalling hurricanes and major hurricanes has been down.
Weatherbell’s hurricane lead Guru Joe Bastardi commented on the season.
Summing Up the N Hemisphere Tropical Season
- Yes most named storms in the Atlantic. Weatherbell underdone on total names
- Yes highest impact year on the US coast (no surprise as we made a huge deal about that from April)
- ACE at 180 within our ACE range from March! 13th highest on recordBTW another abysmal year by the Euro models. We put out that ACE in March. At that time the Euro was forecasting 80% of average
- Here is where it gets interesting: ACE/Storm was 6 ranking DEAD LAST way back in Last as far as ACE/Storm. How bad was it? The AVERAGE ACE/STORM in the other 21 seasons was 12! The closest to this year was another mega named year 2005 but that was a respectable 9
The obvious conclusion is 2 fold,
- Some of these should not have been named or would not have been in previous years. Now if you don’t want to accept that fine, but it means more storms, but weaker. It is absolutely astounding to see the ace/storm HALF the average of the all the other samples.But it gets worse as far as the hype:
- The total ignoring of the lack of activity in the Pacific Basin and globally.
I keep hearing global this and global that which of course applies only if one is going to ignore the fact that the number one area for ACE (Pacific) was so far below normal -‐ Western Pacific was 52%, the eastern Pacific 56%.
The total ACE between the two is normally 426. This year, so far, ACE there was 226. So the basin with 4 times the normal of Atlantic, is only 50% of its normal! For the northern hemisphere was 80% of normal. So even with the hyper Atlantic season.
GLOBALLY we were BELOW average.
So there is no question the impact of the western hemisphere is a huge record breaking deal, and should be talked about, But if you want perspective and the whole picture, there is plenty to counter the idea that this is an example of some kind of atmospheric apocalypse, But you have to look and if you do, you will see that there is plenty to talk about on the other side of the coin.
Of course the coin that is flipped when it comes to pushing ideas today always seem to come up one way.