Tuesday, April 2, 2024

The 2024 Atlantic Hurricane Outlook part two

 

Here is part two of the 2024 Atlantic hurricane outlook. This is an extension of my analysis from my 2024 Hurricane Outlook Part One. I will take you through the reasons I think this is going to be a very busy season.

Link to part one.

The 2024 hurricane season is getting closer. The Hurricane Season starts on June 1’s and will end on November 30th.  The 2024 Hurricane season should be quite different as we transition from El Nino into A la-Nina.

 Sea Surface Temperature Anomalies (SST)…

 




In the Pacific

We still have slightly above average SST in the equatorial Pacific. But these are much cooler than they were a few months ago. We also have very warm SST in the Northwestern Pacific.

Both of these will play a big role in this year’s hurricane season.

In the Atlantic SST anomalies across the Main Development Region (MDR) (the area between the Lesser Antilles and the West Coast of Africa) are well above average. The SST in the Caribbean and Gulf of Mexico (GOM) aren’t quite as warm, but they are still above average. As we approach the heart of the hurricane season, these Atlantic Basin SST will become even warmer.

Average water temperatures since January in the Atlantic’s Main Development Region are 2 °F above last year, crushing previous highs by almost 0.6 °F.

Another thing we see in the Atlantic is cooler SST in the North Atlantic north of the MDR. This is another indicator of an active season. As this temperature contrast helps supply lift that the tropical waves can use to make it easier for convection to develop in the MDR that could lead to Tropical Cyclone development.

 The El Nino-Southern Oscillation (ENSO)…

The ENSO is a climate pattern that involves changing water temperatures in the Central and Eastern equatorial Pacific. There are three statuses of the ENSO: La Nina, neutral and El Nino.

Last year we were in a strong El Nino with SST anomalies peaked in November-December last year.

The primary metric used by NOAA to gage the strength of an ENSO event is the three-month-average temperature of the central tropical Pacific Ocean, specifically in the Nino-3.4 region.

The temperature anomaly—the difference from the long-term average, where long-term is currently 1991–2020—in this region is called the Oceanic Nino Index (ONI). We use a three-month average because ENSO is a seasonal phenomenon, meaning it persists for at least several months.

The threshold is further broken down into Weak (with a 0.5 to 0.9 SST anomaly), Moderate (1.0 to 1.4), Strong (1.5 to 1.9) and Very Strong (≥ 2.0) events.

While we don’t have official strength definitions, but, unofficially, an ONI anomaly of 1.5 °C or warmer is considered a strong El Nino. Last year the ONI peaked at 2.0 °C which would indicate a very strong El Nino.


Since November-December last year, SST have dropped. Some areas in the equatorial Pacific are already showing up cooler, as upwelling is bringing cooler water to the surface. We’re quickly heading toward neutral. We’re most likely going to become neutral sometime next month or in May. After that we should quickly move into La Nina. The chances are growing for a La Nina to develop by summer and hurricane season 2024.



The colder subsurface water temperatures are just beneath the surface. Looking back at the equatorial Pacific Nino regions, we can see region 1+2 off the South American Coast is already showing much cooler SST.

Typically, during La Nina hurricane seasons, the Atlantic Basin sees a more active season due to less wind shear and trade winds and more instability.

During a La Nina year that follows a strong El Nino like the one that is happening in 2024, the tracks of tropical cyclones tend to be more active in the Caribbean and GOM.



The El Nino events in the record (starting in 1950) with the largest Oceanic Nino Index values are 1972–73 (2.1 °C), 1982–83 (2.2 °C), 1997–98 (2.4 °C), and 2015–16 (2.6 °C). 1987-1988 El Nino reached (1.7 °C). 2009-2010 (1.5 °C) These seasons were all followed by a La Nina.

Possible Analogues… 

La Nina seasons following a strong El Nino

1973, 1983,1988,1995,1998, 2010 and 2016

 Other factors that will have an impact on activity…

Saharan air layer (SAL) could be an inhibiting factor, especially during the first part of the season. As I’ve said in the past, the SAL is a layer of hot dry that can contain Saharan dust, blown off of Africa and out over the Atlantic.

SAL creates atmospheric parameters that suppress tropical cyclone formation and intensification. Last season featured less than average SAL over the Atlantic. If that is again the case this year; it would increase the odds for an active season.   

The Bermuda/Azores High (BAH) is a large area of high pressure that develops over the subtropical Atlantic Ocean. It exerts a lot of influence on the track of tropical systems.

The location and strength of the BAH will also be important.  As this will determine how far west the TC can track. If the BAH is weak and farther east TCs will have a greater chance to curve north up into the Atlantic. On the other hand, if the BAH is strong farther west, there will be a greater opportunity of the TCs to make in into the western Atlantic along with the Caribbean and GOM.   

 Other Outlets…

AccuWeather is calling for 20-25 named storms, with 8 to 12 becoming hurricanes, 4 to 7 of those becoming major hurricanes (Category 3 or above with at least winds of at least 111 mph). They are predicting 4 to 6 U.S. landfalling TCs. They say the seasonal Accumulated Cyclone Energy (ACE) will be 175-225.

Colorado State University (CSI) is calling for 23 named storms, 11 becoming hurricanes, 5 of those becoming major hurricanes.

WeatherBELL Analytics says the season will have 25-30 named storms, with 14 to 16 becoming hurricanes. Of these they are calling for 6 to 8 major hurricanes, with a seasonal ACE of 200 to 240.  

Tropical Storm Risk (TSR) calls for 20 named storms, 9 of these becoming hurricanes and 4 of these to become major hurricanes, with a seasonal ACE of 160.

All of these have one thing in common; they are all calling for a very active and possibly explosive hurricane season.

 What does all of this mean?...

 Based on the early signs, everything is pointing toward an above average season in the Atlantic Basin.  Last season had very mixed signals. We had a strong El Nino, which typically leads to less Atlantic hurricane activity, VS, super warm SST in the Atlantic. We saw how that worked out. The 2023 season featured well above average activity in the Atlantic Basin. This season is looking to feature a La Nina, which typically increases the likelihood for tropical cyclone development in the Atlantic, along with SST in the tropical Atlantic even warmer than they were last season. So, I have high confidence that this season will be above average, with a decent chance for the season to become hyperactive.

Based on the SST temperature profiles, I think 2024 should be similar to seasons like 2020, 2017, 2011, 2010, 2008, 2005 and 1995.

While there is no guarantee that an active season results in several U.S. landfalling TCs. It does increase the odds.

 


The data shows that the risk for hurricanes making landfall, are almost double when the Atlantic is warm vs when it is cool. The data also shows the risk for landfalling hurricanes is almost two and a half times greater during La Nina seasons vs El Nino seasons.   

We also have those well above average SST in the Northeast Pacific. This favors a pattern that could be very similar to what we had in 2005, 2007 and 2020. Those years saw several U.S. Tropical Cyclone landfalls.

With the super warm water in the Atlantic there is a greater risk for TCs to rapidly strengthen. When you add in the increased risk for landfalling systems, the idea of rapid intensification is something to worry about.

In part one, I said the eastern Gulf Coast, Florida and the Carolinas are at an above average risk for direct impacts. With a slightly less risk for the Texas Coast, Middle Atlantic and New England seeing possible landfall TC risk.  That still seems to be true. The Caribbean is also going to be at a heightened risk.

 In Summary…

 The early indications are that the 2024 hurricane season is going to be well above average.

The U.S. will likely see multiple landfalling tropical cyclones.

 

I will be releasing part three in May.







You can find part 3 here