Teban54 wrote:Hammy wrote:and it hasn't been reduced 500mb heights (Humberto's track should not have happened in September, being pulled north by an early spring-like cold low at that latitude_
Very minor correction that's a distraction from your overall comment, but: I feel that tracks similar to Humberto '13, where a CV storm is pulled north immediately near the CV islands, has become a bit more common over recent years. Examples include Katia '23, Hermine '22, Rose '21, Vicky '20, and to some extent Gabrielle '19, all in September.
As it would drastically deviate from the topic (and I enjoy investigating these things in my free time anyway) I wanted to give this it's own thread and address this in more detail now that I've figured out how to make the reanalysis maps
The situations listed are not abnormal, as some storms do recurve farther east, but the mechanisms behind this are key: Vicky in 2020 was interacting with Teddy (and also exited Africa north of 15N as the northeastern edge of the same monsoonal complex that spawned Teddy) and steered to the west after that once it felt the influence of the mid-level ridge.
Rose, Gabrielle, and Katia were all steered north through a combination of a breakdown in the ridging, and a descending upper level trough (Gabrielle in fact rotated around this--not uncommon at all in the eastern Atlantic, and curved west before recurving entirely), and Gabrielle/Katia likewise exited around 15N (this seems to be more common in recent years)
Hermine both exited at 16N, and also featured a ridge to the north, filled with weaknesses.
Breaking this down, and showing what makes 2013's conditions so unusual, and so winter-like, compared to the other examples. I've tried to standardize the colors for comparison consistency
Hermine in 2022
Gabrielle in 2019
Katia in 2023, the closest to Humberto--but about 583-584 dam, and not particularly unusual for an El Nino, which itself can produce somewhat spring-like upper air conditions.
Now here's where 2013 differed--580-581 dam, centered around ~25N, entirely cut off from another larger low to the northeast. What was particularly significant is this was strong enough to scoop up a hurricane out of the deep tropics, around 10-12N, and pull it straight to the north on the eastern edge of it rather than northwest as would be more typical of a storm following the weaknesses that can occur. And this was quite strong for this latitude no less
Returning to the 2013 comparison that was made by another poster, this year features an intense ridge, rather than these winter-like mid-level low centers, and does not feature the basin-wide, March-like wind shear that was also persistent through the entirety of 2013. And August 2013 featured two short-lived tropical storms, where this year featured a relatively long lived Cat 1, and a medium-tracker Cat 2.