As we head toward October, how is the season stacking up?

 

When I posted my hurricane Outlook in the Spring, I said this would end up an active season in spite of the idea of a moderate to strong El Nino; I outlined how those record warm Sea Surface Temperatures in the Atlantic Basin, would help counter the El Nino. My call then was for 14-20 named storms, 8-12 hurricanes, 3-5 major hurricanes. The CONUS could see 2-4 landfalls with one of them possibility being major. The ACE would be 100-150.

So far, the Atlantic hurricane season has been proceeding at a blistering pace. So far this year, there have been 17 named storms, including an unnamed subtropical storm off the East Coast in mid-January, and 6 hurricanes, of which, 3 were major  category 3 or above, Category 5 Hurricane Lee and Category 4 hurricanes Franklin and Idalia. Tropical Storm Harold made landfall in south Texas. After briefly attaining Category 4 strength on August 30, Hurricane Idalia made landfall in the Florida Big Bend as a high-end Category 3 hurricane, before making another landfall in South Georgia as a tropical storm. Hurricane Lee rapidly intensified into a Category 5 hurricane, then after narrowly missing New England, he made multiple landfalls in Atlantic Canada. Tropical Storm Ophelia made landfall in North Carolina.

Credit WPLG 10, Miami, Florida

 At the time of this posting, The North Atlantic ACE Index stands at roughly 123.5 points, which is 153% higher than the average for this time of the season.

Credit Dr. Ryan N. Maue

There are only 5 names left on the official list for the Atlantic Basin. 

We still have two months to go in this year’s hurricane season, based on the ACE index, we still have 22% of the season's activity ahead of us for October and November. An average hurricane season generates another four storms, two of which become hurricanes, from October through the season's end. So, there is plenty of time to add to the already impressive numbers.

The SSTs in the Atlantic basin are still at record warmth, particularly in the part of the Caribbean Sea and Gulf of Mexico most prone to late-season storms.

As we head into October, the Cape Verde season with the African easterly waves in the eastern Atlantic Ocean, and in the center of the Atlantic fades. This time of year, we typically look for the formation of tropical cyclones to happen in the northwestern Caribbean, or in the Eastern Gulf of Mexico off the coast of Florida, as well as the Western Atlantic along the East Coast. The reason for this is that, SST in the Atlantic Ocean typically start to cool and wind shear increases, so the majority of the tropical activity shifts back into the Caribbean and Gulf of Mexico, where water temperatures are usually still very warm, and old frontal boundaries tend to hang around, which often can be the focal point for tropical development.

On average, October ranks third behind September and August for months with the most named tropical systems in the Atlantic basin. In recent years, some of the strongest and most impactful hurricanes have struck in October. Some of which were, Hurricane Hazel which made landfall as a strong Category 4 between North and South Carolina on October 15, 1954, Category 5 Hurricane Michael in 2018 which caused catastrophic damage in both Mexico Beach and Panama City, Florida, with estimated sustained winds of 160 mph., Hurricane Delta in 2020 and Superstorm Sandy in 2012.

Dating back to the 1800s, there have been 172 tropical storms and 252 hurricanes in October. Eight of those storms have reached the strongest strength: Category 5 with sustained winds over 157 mph.

Hurricane season usually quiets down even more as we head into November, especially for the U.S, ​with just 56 total in 171 years of record keeping. November U.S. hurricane landfalls are extremely rare, with just four ever documented.

So, if you live along the Gulf Coast or along the East Coast, don't let your guard down when the calendar turns to October.

How is the 2023 Atlantic hurricane season stacking up to my hurricane outlook at this time?

 

The Season so far…

Atlantic hurricane season officially lasts from June 1 to Nov. 30 every year, but tropical cyclones can still form outside of the time window at any time.  That happened this year, with the formation of a subtropical storm that formed off the Northeast Coast on January 16.  The National Hurricane Center (NHC) has kept the storm unnamed, and have treated it as non-tropical.

Since the start the season has been active, with 13 named systems. Three of them have been hurricanes, with two of those becoming major hurricanes. From June 1^st through the third full week of July we had four named tropical cyclones, 

Tropical Storm Arlene formed on June 1^st, Tropical Storm Bret formed on June 19, Tropical Storm Cindy formed on June 24; then on July 14, Subtropical Storm Don formed. He then weakened to a subtropical depression early on July 16. Later the same day he was deemed a tropical depression. On July 17^th he was upgraded to a Tropical Storm; then he became a category one hurricane on July 22.

After Don, tropical activity in the Atlantic went on hiatus until the 20^th of August.  

Tropical Storm Emily formed on August 20^th; Tropical Storm Franklin also formed on August 20^th; Franklin struggled in the Eastern Caribbean, but after moving over the Dominican Republic, the environment become much more favorable; On the 26^th He became a Category 1 hurricane, then after rapid intensification he became a Major Category 4 hurricane on August 28^th, Tropical Storm Gert formed on August 22. After wind shear tore him apart, just enough circulation remained for him to make a comeback on September 1 when he regained tropical storm status, Tropical Storm Harold, formed on August 22, making landfall on Padre Island, Texas later on the same day, Tropical Storm Idalia formed on August 27, August 29 I Idalia became a Category 1 hurricane, then rapidly intensified to a Major Category 4 on August 30, just before landfalling, Idalia underwent an eyewall replacement cycle just before landfall, resulting in her loosing strength and making landfall in the Big Bend of Florida as a Strong Category 3,  Tropical Storm Jose formed on August 31^st, Tropical Storm Katia formed on September 2^nd, Tropical Storm Lee, formed on September 5^th, Lee will undoubtedly become the seasons third major hurricane of the 2023 hurricane season in a few days.

 

This seasons Accumulated Cyclone Energy (ACE) index so far…

 

Above, shows this season's ACE index as of 18:00 UTC on September 6, as calculated by Dr. Ryan N. Maue using data from the NHC, is approximately 59.335 units, which is 141% above average for this point in the season. Ace is used to express the energy used by a tropical cyclone during its lifetime, the higher the ACE number the stronger the storm and greater the potential for destruction it has.  The ACE of a season is the sum of the ACE for each storm and takes into account the number, strength, and duration of all the tropical storms in the season. This number represents sum of the squares of the maximum sustained wind speed (knots) for all named storms while they are at least tropical storm intensity, divided by 10,000. Therefore, tropical depressions are not included.

 

The real time ACE Statistics for the North Atlantic provided by Colorado State University.

 

 

As seen in the graph above, the peak of the season is from mid-August to late October. During this period, there is a spike in activity accounting for 78% of tropical storm days, 87% of category 1 and 2 hurricane days, and a whopping 96% of major (category 3, 4 and 5) hurricane days. So based on this, we’re now in the historical peak of the hurricane season, so there is still a lot of time for more hurricane this season.

 

Why all the activity this season? …

Typically, during an El Nino, Atlantic Basin tropical activity is below to well below the Climatological average. This is even more likely during a strong El Nino. This is due to how El Nino typically causes stronger upper-level winds along with stronger easterly trade winds, leading to disruptive vertical windshear, which lead to a lot of sinking air and much more stable atmospheric dynamics over the Caribbean, Gulf of Mexico and Atlantic Ocean.  But this year things are a bit different.  The Caribbean Sea and the Gulf of Mexico have seen quite a bit of shear, while the Eastern and Central Atlantic has seen much less in the way of disruptive wind shear.

In my hurricane outlooks I said, the we’ve never seen the Atlantic Basin so warm, during an El Nino. In the Outlook I said those record warm Sea Surface Temperatures (SSTs) in the Atlantic very well could counter what the El Nino would typically bring.

So based on everything I was seeing at the time, my call was for 14-20 named storms, 8-12 hurricanes, 3-5 major hurricanes. The CONUS could see 2-4 landfalls with one of them possibility being major. The ACE would be 100-150. When we look at the numbers so far this season, we can see my forecast is likely to verify.

When I issued my final outlook in May, most of the other weather outlets were calling for lower numbers than I was, but later on the weather outlets increased their forecast numbers to be in line with what I was calling for.

 So, despite a strengthening El Nino, and the likelihood for a strong to super El Nino, Those super warm SST, and atypical favorable upper-level winds across the Main Development Region (MDR) of the tropical Atlantic. The Atlantic Basin should remain active as we see these tropical waves continue to push off the West African Coast.

It remains to be seen if the Caribbean and Gulf will see wind shear become more favorable during the 2^nd half of the season. But it is worrisome that we’re now in what is called the Cape Verdie Season, which, runs in correlation to the peak of Hurricane Season, between middle of August and through September. As more numerus tropical waves move off of Africa this time of year conditions are more favorable for development. This year with the record warm water, these systems will have greater opportunity to strengthen into extremely powerful hurricanes, due to the shear amount of time they have over open warm waters. I still think the Northeast and Middle Atlantic are at an increased risk for a landfalling impact this season.

 

We will see how things go from here.