2021 Atlantic hurricane outlook part 3

 

Will the 2021 Atlantic Basin hurricane season be as bad as 2020’s record breaking season?

 

This is the final installment of my 2021 hurricane outlook for the Atlantic Basin. If you’re reading this, it’s assumed you have read parts 1 and 2. Part 1 can be found here, and part 2 can be found here.  May 9^th – 15^th is National Hurricane Preparedness Week; so, posted the 3^rd part seems appropriate. You can find preparedness information at the end of part 2.

For this outlook, I run down through many of the particulars, updating on La Nina, how many tropical storms and hurricanes I am expecting, along with the probability of path of many tropical systems this season, Please Like and Share!

The Atlantic hurricane season runs from June 1 to November 30; the season peaks during August through the first half of October. This is when the ocean waters are typically at their warmest.

This outlook is based on many factors, including: La Nina and other teleconnections, Atlantic Basin Sea Surface Temperatures (SSTs), computer model guidance, atmospheric conditions in the North Atlantic, and past analogs years that exhibited a similar overall pattern.

 

Analogs:

I’ve came up with my final set of analog years. They are: 1887, 1996, 2005, 2008, 2011, 2012, 2017, 2020

Teleconnections:

The El Nino-Southern Oscillation (ENSO)

La Nina, we’re still in a moderate La Nina, the models do take it back toward neutral.  Meteorologist are split on whether the ENSO stays neutral or reverts back to La Nina conditions.  I still think we’re going to see the La Nina conditions reenergize later this year into the winter. But before that, the atmosphere isn’t going to respond to the neutral trend right away. Typically, the atmosphere response lags a few months, so we most likely won’t see a real drop off in tropical activity until late October or November.  La Nina, will result in much below average wind shear over the tropical Atlantic, Caribbean into the Gulf of Mexico (GOM).   Last seasons La Nina became one of the strongest in at least 10 years.

 

Here is a look at the latest IRI forecast chart of the ENSO for 2021.

 

 

The Atlantic Multidecadal Oscillation (AMO):

As I said in part 2, the AMO is generally positive. During the positive warm phase the conditions in the Atlantic Basin are much more favorable for tropical cyclone formation.

 

The North Atlantic Oscillation (NAO):

During a negative NAO tropical cyclone are more likely to make landfall in the GOM; we had a generally negative NAO during the 2020 season.

 

Conditions are going to be more favorable for tropical cyclone development over the eastern Atlantic and west Africa.  Due to a strong West African Monsoon.

I don’t think we will see as much Saharan Air Layer (SAL) …Saharan dust… this season as we saw last season. African dust over the Atlantic tends to make conditions over the Atlantic more hostile for tropical cyclone development. But even with 2020’s large and imposing dust layer, 2020 went on to be a hyperactive hurricane season.  A big reason for that was the strong La Nina in the Pacific.

The Bermuda High was very strong last season; this season it won’t be as strong, also it looks to be displaced a little more north and east. As a result, the East Coast is going to be at higher risk this season, due to the greater likelihood of tropical cyclones recurving out of the MDR into the western Atlantic off the Eastern Seaboard.

 

While the East Coast is going to be at a heightened risk, especially during the 2nd half of the hurricane season, that doesn’t mean the GOM won’t also be a risk.

There is going to be an enhanced risk for the Bahamas, Florida and the eastern GOM, unfortunately that might include Louisiana as well; who was hit very hard last season.

Last season the Southern and especially the southwest Caribbean was very active. This season is going to see a lot of that activity shift north into the northern Caribbean

 

Here is a look at the current Sea Surface Temperatures (SSTs) in the Atlantic Basin. in the Main Development Region (MDR), northern Caribbean, GOM, and along the East Coast and Atlantic Canada SSTs are well above average for this time of year; these temperatures are only going to get warmer as we move through the hurricane season.  Now the inter tropical convergence zone (TCZ) is slightly below average, but that too is going to warm up.

SSTs like these are typically seen prior to an active Atlantic hurricane season, and correlate very well with most of the analogs.    

 

With the warm SST in the Northern Caribbean, eastern GOM, and along the East Coast, we will have to be mindful of the possibility for rapid intensification as tropical cyclones move over that warm water.

 

 

 Courtesy of WeatherBELL Analytics

 

Courtesy of Coral Reef Watch

 

The overall pattern:

Last year, saw the most active Atlantic hurricane season in recorded history, with a total of 31 tropical cyclones, 30 named storms, 13 hurricanes, and 6 major hurricanes.  When we look back at April and May of last year and compare that to this year, we can see they’re remarkably similar to each other.

 

500mb images are courtesy of the University of Wyoming

 

500mb images are courtesy of NOAA/Storm Prediction Center

 

2M temperature charts are courtesy of NOAA/NCEI U.S. Climate Division

This Spring has seen a lot of persistent high latitude blocking near Greenland. This likely to continue. This is going to help allow for warmer water in the tropical Atlantic this season.

This season will most likely see quite a bit of upper level ridging in the Northern Pacific and in the Northwest Atlantic. If this does happen, the setup would help funnel tropical cyclones closer and into the East Coast.

 Conclusion:

Remember, even during an active year, there is no guarantee there will be a landfall. But with the pattern supporting the idea of recurving TC’s off the East Coast, the odds certainly support the idea of heightened landfall risk along the East Coast.  It’s been quite a while since the Northeast had to deal with a major hurricane. While there is no certainly; I think the Northeast is at a heightened risk for a major impact this season. 

 Like last year, I think we have a good chance to get through the entire naming list in the Atlantic Basin.

 The Atlantic Basin Numbers:

Accumulated Cyclone Energy (ACE)

ACE sums up the intensity and duration of storms. So, a weak, short-lived tropical storm counts for almost nothing, whereas a major, long-lived hurricane will quickly rack up dozens of points. The higher the ACE number the more powerful and destructive the storm or season:

 The ACE value for the 2020 Atlantic season ended up being 179.8

For 2021 I’m looking for an ACE value of 140-190

For 2021

Named Storms

18-26

Hurricanes

6-13

Major hurricanes

3-6

U.S. landfalling tropical cyclones

6-10

Well, that’s it, this is the last preseason outlook update. I could release some revisions to this during the season. Questions are always, welcome, either on here or on my Facebook weather page. The link to that page is here.