Hurricane Gabrielle has continued its trek across the northern Atlantic and is about to pass over the Azores at hurricane intensity. It is losing its tropical characteristics and will transition to an extratropical cyclone within the day -- though that will not diminish the significant impacts it will create in the Azores.
The islands have had fifteen hurricanes pass within fifty miles of them since records began, and the most recent was Lorenzo in 2019. Four of the fifteen were at Category 2 intensity, and the other eleven were Category 1: https://bsky.app/profile/bmcnoldy.bsky.social/post/3lzlq3kdb422e
I have my first-ever radar loop in the archive from the Azores, and you can find the latest version at https://bmcnoldy.earth.miami.edu/tropics/radar/:
In the western Atlantic, Invest 93L was upgraded to Tropical Storm Humberto on Wednesday afternoon, and Invest 94L is now centered just north of Hispaniola and is close to becoming a tropical cyclone -- the next name is Imelda.
Humberto is the season's 8th named storm, and the average date of 8th named storm formation was September 9. However, Humberto could also become the season's 3rd major hurricane in a few days, and the average date of 3rd major hurricane formation is October 28!
Conditions ahead of Humberto appear very favorable for intensification, and the 11am EDT advisory from NHC explicitly includes a period of rapid intensification on Saturday into Sunday. Beyond this 5-day forecast, it looks likely that it will make a turn to the northeast around the time it crosses 30°N. It does not appear that it will impact land along its journey.
Invest 94L, on the other hand, could create problems in the southeast U.S. It's currently fairly disorganized and centered north of Hispaniola and west of Humberto, but it looks likely that it will become a tropical depression or tropical storm sometime on Friday (the next name is Imelda).
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| Satellite loop of Invest 94L (left) and Tropical Storm Humberto (right). |
It is expected to intensify as it passes over the Bahamas, then the exact track is extremely challenging to predict because of the uncertainty in the intensity AND because of its proximity to Humberto -- it's possible the two cyclones will influence each others' tracks in a process commonly called the "Fujiwhara effect" (I have a mini-thread about this at https://bsky.app/profile/bmcnoldy.bsky.social/post/3lzlompr3vk2e).
A similar plot to what I showed above for Humberto is shown below for Invest 94L. The track density for the multi-model "super ensemble" indicates the highest probability of a track into the Carolinas, though south Florida and northward should also be on alert and paying close attention. If it does make landfall, it could be as a hurricane. This could also be a significant rainmaker for eastern South Carolina, North Carolina, and Virginia.
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We will have to wait and see how long it takes to develop, where the center ends up forming, and how close it gets to Humberto. It's a complex setup, but has the potential to have big impacts in the southeast U.S. in the next 4-6 days.
Looking at ACE again, the season is now up to 67% of average for the date, and although Gabrielle will stop contributing once it becomes an extratropical cyclone, Humberto (and possibly Imelda) will pick up and continue to accrue ACE in the coming days. As of today, this is the least ACE accrued through September 25 since 2016.
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