As summer transitions to fall, another hurricane season prepares to enter its peak. It's time to talk tropics.
As long as I can remember, I have been most fascinated by tropical meteorology. The complexity, unpredictability, and power of tropical cyclones has always caught my eye, and I have spent decades learning more about it. I've told this story before, but 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.
Tropical systems impact Connecticut and New England in a number of ways. Tropical systems, even if they are not major hurricanes, or even hurricanes, can cause catastrophic destruction over hundreds or even thousands of square miles.
Connecticut is far from immune from tropical impacts, and our recent history shows the types of impacts we can see. We've seen tropical remnants, a tropical storm hit, a near miss, and a direct hit. What we haven't seen, however, is a landfalling hurricane.
Connecticut has not seen a landfalling hurricane since Hurricane Gloria in 1985. It has not seen a major (Category 3+) hurricane since 1954. In fact, the last hurricane to make landfall in New England was Hurricane Bob just to our east in 1991.
To go this long without a hurricane strike in New England is actually highly uncommon.
According to research from CCHurricane, New England sees more tropical activity than one would expect. Looking at the period of record between 1850 and 2000, hurricanes made landfall in New England approximately once every eight years. Tropical storms hit once every four years.
The most interesting statistic from this research however is this: Since 1850 this is the first time New England has gone longer than 20 years without a hurricane landfall.
As CCHurricane notes in their research, it's possible the recent period is due to structural changes due to climate change, or perhaps the 1850-2000 period was an anomaly with no longer historical record. Either way, based on the last 150 years plus, New England is overdue for a hurricane.
At SCW, we believe in preparation over panic. This annual 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 and Tropical Storm Irene, where thousands of trees and branches on hundreds of power lines caused extreme power outages. Irene caused historic storm surge in parts of southern Connecticut.
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. This trough would need to be centered in the Great Lakes region especially, but the Ohio Valley could work too. if there's a cutoff low in this setup, it almost guarantees an impact as it induces a northward to north-northwestward motion of a system off the southeast US coast.
Most of the time, the troughs are further east, forcing a northeastward motion away from the coast. They induce a kick away from the coast rather than a capture toward the coast.
For the purposes of our illustration, 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 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. As I alluded to earlier, that's what I call a "kicker".
In July, we had a pattern that lent itself to tropical impacts, but there were no tropical systems. This month, we've seen a predominant pattern disfavoring tropical impacts. The window for impact looks small entering September, but not closed completely.
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.
Forecasts can be incredibly sensitive. An example from last year is Hurricane Fiona, which missed New England but hit Atlantic Canada. Even a few days out, the guidance shifted significantly from out to sea to hitting land. Troughing further to the west could have put part of New England in play.
Another great example that I've discussed before is Hurricane Henri. The National Hurricane Center (NHC) has the best tropical experts in the world and 48 hours before landfall their forecast was for 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.
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.
So, what can I expect this hurricane season?
Plenty of activity between now and September 20, followed by a quick drop off in activity in the basin.
Named Storms: 13
Major Hurricanes: 3
So far, we've had four named storms since August 20!
I don't think that pace will continue, but the next four weeks look to be the active period of peak season. This season had a wide split on whether the growing El Nino, which strongly favors a below normal season, would overcome truly historic warmth across the Atlantic basin. Most forecasting outfits have gone with an above normal season, but my forecast is near normal, with a higher number of named storms, but a normal number of hurricanes and major hurricanes.
I think right now climatology bringing lower shear, dry air, and subsidence means that we are active for the next month, out-dueling the Nino. However, by around September 20, favorable climo starts to fade around the basin. As that happens and the Nino influence grows, I think we see a quick shutdown of the basin. To be clear, that doesn't mean no storms, but it'll become much harder.
What are those factors?
After a three year Nina, we're solidly in an El Nino regime. Of course, every ENSO event is different, and intensity/location matters a lot. Given what I project, and I will admit I am not as good with the intensity/location stuff, as well as what I've seen so far, the fundamental atmospheric response in the Atlantic that allows for anomalously high shear through the basin has not yet occurred, despite the shear in the basin currently.
During the peak guidance actually shows a decrease in shear, but the influence of the Nino should eventually increase, bringing a wind down of activity around the basin, particularly the Caribbean. Without the historic warmth, the Atlantic would be certain to see a below normal season.
There are more, like the influence of SAL and the MJO, but for the sake of brevity, I'll stop here!
With an average season expected, I think the risk to the US and CT is about the same as usual. I do think the US continues its streak of a major hurricane making landfall in the US, however. As I mentioned earlier, we have to watch the upper level steering pattern.
I think it's less likely for us to see a system that develops further away, like current Tropical Storm Franklin, to impact New England because we see different orientation of troughing now than what we saw in July. El Nino actually favors more Main Development Region recurves.
However, anything that develops closer to home in the eastern Gulf or western Caribbean/southeast coast, will have a window of impacting New England, especially if we see a stronger subtropical Atlantic ridge, which I think is possible in early September. The window doesn't look wide open, but it's open enough and unpredictable enough to watch.
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.
The best way to prepare is to prepare when there is no storm imminent.
SCW will be here every step of the way.
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Finally, I would like to acknowledge the late Dr. William Gray, who was an inspiration as I grew up.
Thank you for reading and trusting SCW.