As many of you know, I am all about tropical.
As long as I can remember, I have been most fascinated by the complexity, unpredictability, and power of tropical cyclones. The first tropical experience I remember is Hurricane Floyd in 1999, which passed right over my house in central Connecticut as a tropical storm. I remember being glued to the television and satellite as it rolled up the coast, and the power going out in my elementary school as the trees swayed in the wind.
Of course, not all tropical systems are as "gentle" to Connecticut (and elsewhere) as a weakened tropical storm. Tropical systems, even if they are not major hurricanes, can cause catastrophic destruction over hundreds or even thousands of square miles. Hurricanes have, even in recent years, been responsible for thousands of deaths, mostly from flooding and the aftermath of the storm. As we have seen firsthand, Connecticut is not immune from tropical impacts, as the state received direct impacts from a highly unusual four systems last season: Fred (remnants), Tropical Storm Elsa, Tropical Storm Henri, and after the worst hurricane impact last year in the US--the remnants of Major Hurricane Ida.
Connecticut has not seen a landfalling hurricane since Hurricane Gloria in 1985. It has not seen a major (Category 3+) hurricane since 1954. The closest hurricane approach was Bob, in 1991.
It has become a common phrase, but we are long overdue for a hurricane strike in New England. Although we have had a number of storms like Irene, Sandy, and Isaias that have helped cull the overgrown and dead trees in CT, it may not be enough. It is not hyperbole to say that a bona fide hurricane strike would be catastrophic in New England depending on the exact track.
At SCW, we believe in preparation over panic. This special discussion is designed to help readers understand the basics of tropical systems and tracking so you know to prepare long before any type of system, whether a hurricane or tropical remnants, threatens Connecticut.
Let's start with the basics.
In New England, the hurricane return period is longest in the nation with good reason. it is difficult to get a tropical system up this way.
That cuts both ways. A damaging storm is less likely each year, but it also means that when a damaging storm does happen, the impacts are more severe because the infrastructure has not been built to be resilient in the face of wind and water damage.
There is no better illustration of this than Tropical Storm Isaias, where thousands of trees and branches on hundreds of power lines caused extreme power outages.
In order for a tropical system to truly threaten New England, you need to thread the needle between a strong ridge of high pressure to our north/east that would block the exit of a tropical system, and a trough to the west of the region (in the Great Lakes region especially, but the Ohio Valley could work too, along with a cutoff low which would almost guarantee an impact) that induces a northward to north-northeastward motion of a system off the southeast US coast. Depending on the trough orientation, sometimes that can cause a northwestward movement, like Henri last year.
For the purposes of our illustration though, we look at an imperfect, but obvious example from 2020's Tropical Storm Isaias.
Here, there is a big ridge to the east that prevents escape, and a big trough in the Great Lakes region (perhaps a little far west for a classic New England landfall) that pulls the system inland over the Carolinas and north. The center of Isaias moved to our west, but we had major wind damage. If you see a similar ridge/trough combination, watch out.
Often, we see troughing over the region or just to our west, and no ridge. That forces systems well out to sea well before it reaches our shores. That's what I call a "kicker" and that's the predominant pattern right now. Seeing this pattern is how we know that most of the time we see a system off the US coast we know it is going to recurve harmlessly out to sea.
The upper level pattern is critical.
When tracking tropical, utilize ensemble forecasts heavily when there is a weak or emerging signal for a system to develop. Using operational guidance like the Euro or GFS will steer you in the wrong direction if you don't know what to look for.
If someone posts something from 10 days out of a hurricane hitting the area, it's almost certainly hype and should be ignored until there's more data.
A great example of the complexity of hurricanes is Hurricane Henri last year. The National Hurricane Center (NHC) is the most accurate tropical forecasting organization in the US and quite likely on the planet. This was their forecast within 48 hours of landfall, showing a strong tropical storm making landfall near New Haven!
Just 24 hours later, right before landfall, it was much further east.
We know what happened. Henri weakened on approach and made landfall in Westerly. That's a small change that made a huge difference.
Bottom line, these things are too unpredictable to ignore or wait until the last minute to prepare for.
One more fact to underline this point: of all the category 5 hurricanes to hit the US, none of them were major hurricanes in the 72 hours before impact.
Things change fast in tropical forecasting. Choose preparation over panic.
Plenty of activity.
I am in line with Colorado State University, who is my go-to for detailed technical tropical analysis. We both predict 10 hurricanes and 5 majors, and I go ever so slightly higher on named storms because every year we seem to get a surprise quick spin up that adds to the numbers.
Right now, conditions are not favorable for development, but that's normal. Based on the three systems we already have, we are already about a month ahead of a normal season.
The guidance suggests that pattern will change by the end of the month, and we are likely to be rapidly ramping up to the peak of the season weeks before the average peak in September. Even more so this year because of the pattern coming into view.
What are those factors?
First and foremost, we are in a La Nina. La Nina is huge because it influences weather patterns on a global scale. In a Nina, the Atlantic usually sees significantly reduced wind shear. Lower wind shear is critical to allowing tropical cyclones to develop and develop into hurricanes and major hurricanes. A La Nina also allows for more atmospheric instability over the ocean, a good breeding ground for the thunderstorms that eventually organize and become hurricanes.
A second factor is sea surface temperatures and Tropical Cyclone Heat Potential/Oceanic Heat Content. It may not feel like it since it's still early July, but the extent and depth of warm sea temperatures are critical. This year, as we've seen for nearly a decade, we expect high levels of heat content in the ocean. Of particular importance to me are the warm anomalies in the Main Development Region, the central and eastern Atlantic--where big storms form, and in the Gulf/Southeast Coast--where storms maintain intensity on final approach. Both look robust.
The third factor is what happens with the West African Monsoon. Most of the tropical systems we see and the vast majority of major hurricanes come from waves of convection (storms) that roll off of Africa. When the West African Monsoon is more active, as it is this year, that means expect big waves to come in August and September.
What does that mean for the US and what does that mean for Connecticut?
It's a big deal.
CSU forecasters use projected Net Tropical Cyclone Activity against their forecast to determine the probabilities for impact this season, and also utilize climatology statistics from different periods. For more information about their report, you can read it here. Details on how they calculate their probabilities can be found on Pg 2 and 40-42.
Statistically, we see much higher probabilities for Connecticut this year. To be clear, the odds are low for a hurricane and especially major hurricane in an absolute sense, but they are about as high as you'd see them given that the odds are calculated based on projected activity.
The basic takeaway is this: the more active the hurricane season, the more likely we see a tropical impact here. I don't believe we'll see the four systems we saw last year, but with a well above average season, statistically New England has a much higher chance of a tropical impact. At this range, it's impossible to say if that potential will be realized. Rather than speculate, I will just say that we will be watching.
Currently, the predominant pattern would likely prohibit any tropical activity from reaching us, but with peak summer coming where ridging generally becomes more dominant, I do think the pattern will change.
To what, we will have to wait and see.
How do I prepare?
Hurricane Strong is a national resilience initiative that works to try to prepare residents for hurricane season. It only takes one storm--like an Irene, Isaias, or Ida, to make a season very bad for you. Preparing now could be a series of small steps that save you time, money, and worry in the future.
The Four Basics
1. Know Your Zone--know your evacuation zone in case you need to leave. In CT, that's most likely to be right at the coast, where flooding would occur. The majority of deaths caused by tropical systems are flood related--storm surge or inland flooding. You can find the evacuation maps here.
2. Make A Plan--this seems self-explanatory, but what would you do if you lost power? Needed to evacuate? Needed to get supplies? Check in on a loved one? Having a plan now will save you time and worry later.
3. Build An Emergency Kit--You don't need to make all your purchases at once, but if you wait until a day or two before a storm hits you will run into empty shelves for some items and potentially higher prices. This can be helpful even if there isn't a storm.
4. Stay Informed--Get your information from trusted sources. Don't panic or dismiss a threat just because of one model run or model cycle. Stay level headed and use quality information to make an informed decision.
This season we need to be prepared.
The center of Tropical Storm Isaias passed to our west, which put us on the windy side of the storm. It wasn't a hurricane. It was a weakening tropical storm that was interacting with a trough and it caused extensive damage. Hundreds of thousands of customers lost power for days. Many were caught unprepared. This is an image from the Journal Inquirer of East Hartford, where the town was impacted with substantial tree damage and power outages.
In each of the last two active Atlantic seasons, we saw significant impacts from tropical storms. No one should be surprised that another active season with similar conditions could bring similar results.
SCW will be here every step of the way.
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Finally, I would be remiss if I also didn't take a moment to acknowledge the late Dr. William Gray, who was an inspiration as I grew up. It is an honor to forecast for you utilizing many of the methods he pioneered. For more on the incredible CSU meteorologists, visit their website.
Thank you for reading and trusting SCW.