There has been a lot of chatter in recent weeks about the now underway Atlantic hurricane season. There is as close to unanimous agreement as you can get in meteorology that this year will bring an above average to hyperactive season. NOAA's forecast, which tends to land in the middle, issued its strongest forecast on the number of tropical storms, hurricanes, and major hurricanes.
Hurricane season lasts from June 1 until November 30, and every year the flood of forecast information can be a lot for anyone. This can create a sense of foreboding and anxiety. Here at SCW, we aim to provide information on what we expect, why we expect it, and most importantly, how to be prepared long before any potential storm threatens our region.
This year we anticipate a hyperactive season.
For those of you that have followed SCW for a while, you know that my "specialty" so to speak is in tropical meteorology. As long as I can remember, I have been fascinated by its complexity, and I've made quite a bit of effort to study it, including chasing, analyzing, and documenting hurricanes.
It's extremely hard to find seasonal conditions that have been more favorable for activity than the ones we see in 2024. It's important to note that active doesn't necessarily mean bad, but the flip side of that is it only takes one storm to redefine a landscape.
In recent years, I've put out a peak season forecast, predicting the total number of named storms (NS), hurricanes (H), and major hurricanes (MH) during the approximate peak of the season, August 20-October 20. This year, while I'll likely have a peak season forecast, I'm also expanding to include the entire season.
Let's dive in.
Tropical Cyclone Basics
Tropical cyclones (basically any organized tropical system) are part of a much larger global process that's essential to life. Tropical systems are big heat engines, which move warmth from tropical sections of the ocean to subtropical and northern latitudes, convert heat into wind, and radiate excessive heat out of tropical regions.
This provides balance in our oceans by cooling and turning over the waters, our atmosphere by transferring heat, and landmasses by providing as much as 20-25% of annual rainfall in certain parts of the world and culling old growth.
That said, when adding the human element, tropical systems can have devastating impacts, from shoreline damage from storm surge and maximum winds, to inland damage from flooding rains.
In order for tropical cyclones to form, you need warm water, low (enough) wind shear, and the ever present spin of the Earth to organize storms.
For hurricanes and major hurricanes, you need deep warm water, low wind shear, and sufficient instability (to allow for thunderstorm generation) and moisture. Unlike severe thunderstorms, which require high wind shear, for hurricanes to develop and intensify the cluster of thunderstorms need low wind shear to allow for the storms to organize and lower pressures.
We should know from recent years that tropical systems do in fact impact Connecticut and New England in a number of ways, sometimes with dramatic effect. Tropical systems, even if they are not major hurricanes, or even hurricanes, can cause catastrophic destruction over hundreds or even thousands of square miles.
In recent years, we've seen just what active hurricane seasons can do. It's worth taking a little time to review our recent history from this decade:
The Near Misses: Hurricane Lee (2023), Hurricane Fiona (2022)
The near misses for us have been historic hits for our friends in Atlantic Canada.
Hurricane Lee will be forgotten here, but it defied the odds in last year's El Nino to become a category five hurricane in the Atlantic before turning northward. This system missed Connecticut and most of New England, but at one time there were tropical storm warnings for eastern New England and it was a hurricane at essentially our latitude. Lee was a powerful post-tropical system when it struck New Brunswick and Nova Scotia.
Hurricane Fiona never truly threatened New England with the upper level pattern present, but I classify this as a near miss as an illustration of how extremely powerful storms can still make it north. Fiona, although it wasn't technically a hurricane when it made landfall in Nova Scotia, was recorded as the most powerful storm on record north of Charleston by pressure with a minimum central pressure just offshore of Nova Scotia at a staggering 932.7mb. I went to Cape Breton Island to document this storm, and recorded a wind gust of 65mph on the ground, rather than at the standard 10 meter height, indicating likely hurricane force wind gusts just aloft.
Hurricane force gusts were reported at mesonet stations around Nova Scotia, and one area on the north shore recorded a peak wind gust just shy of major hurricane force.
I went to that region after the storm passed to document the damage. Once again, Fiona is a reminder that objectively big storms are possible this far north, particularly if they are moving fast. Usually, once a storm reaches the Bahamas and turns north, it accelerates.
Preceding our near misses was a very active period in 2020 & 2021 that saw direct impacts from tropical storms and the remnants of tropical systems.
2021: Big Rain Tropical Impacts--Elsa, Fred, Henri, & Ida
This season brought big rainfall impacts to the state and the result was an extremely wet summer and numerous river flood and flash flood events.
Tropical Storm Elsa was a hurricane briefly in the Gulf of Mexico, and even though it trekked inland it crossed into the Atlantic and remained a tropical storm, bringing tropical storm warnings to CT at one point. The main impact from Elsa however was the rain, which brought significant rainfall to central and eastern parts of the state via a Predecessor Rain Event (PRE). These are powerful pseudo-atmospheric rivers that maximize rainfall from a nearby tropical system as it interacts with an approaching trough. We can be susceptible to these given the general steering pattern necessary to both bring a tropical cyclone into the region or kick it away from the coast before it reaches us for a direct impact.
Henri was not that. It was basically a storm that 95+ times out of 100 would stay harmlessly out to sea, but an anomalous upper level pattern steered Henri south, west, and then north, right into the region. The slow movement, which is another highly unusual thing for New England tropical systems, allowed for Henri to weaken before landfall right near the SE CT border, but that slow movement allowed for Henri to meander over the state, dumping heavy rain and causing major river flooding. These are the types of setups that can produce prolific and dangerous flooding.
Henri was far from the worst case scenario, bringing muted wind impacts to CT, but it was a legitimate tropical event, bringing tropical storm force wind gusts, major flooding, and storm surge impacts.
Hurricane Ida made landfall in Louisiana as an extremely powerful category 4 hurricane, but more people died in the Mid-Atlantic and New England (one tragic death here in Connecticut) than in Louisiana. This is because of exceptional setup for flash flooding that developed.
The remnants of Ida interacted with a trough and produced prolific flooding and a significant severe weather (tornado) outbreak in the Mid-Atlantic. Our state saw its first ever high risk of excessive rainfall, and while the story of Ida is often told in the catastrophic flash flooding that took place over NY and NJ, killing dozens, major flooding occurred in parts of CT too.
Hurricane Isaias was a tropical storm by the time it reached the latitude of Connecticut, but of all the systems in recent memory it was almost certainly the most impactful to most residents. New England has a hurricane return period is longest in the nation with good reason. it is difficult to get a tropical system up this way.
However, the benefit we receive in a truly widespread destructive storm being less likely each year gets periodically traded in for the kind of hit that leaves a more severe impact because the infrastructure has not been built to be resilient in the face of high end tropical wind and water damage.
There is no better illustration of this in recent memory than Tropical Storm Isaias, where thousands of trees and branches on hundreds of power lines caused extreme power outages. Here, 60+ mph wind gusts were recorded at BDL, but none of the wind gusts were close to hurricane force.
That's a sobering thought, and a warning shot that we need to be prepared for when the next bona fide hurricane approaches, whether that's two months from now or twenty years from now.
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, particularly in the last 150-175 years of our history is unprecedented.
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. Since 1850 this is the first time New England has gone longer than 20 years without a hurricane landfall.
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 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".
Our last hurricane, Gloria, was a long track hurricane that took advantage of this open window. Bridgeport reported sustained hurricane force winds (74 mph) and a peak gust of 92 mph. Waterbury, a location well inland, reported a sustained wind of 83 mph and a peak wind gust of 94 mph. It's almost impossible to imagine that today, especially considering that there's a generation of folks that have never experienced anything close living in the region now.
Finally, as I've said before, forecasts can be incredibly sensitive. Even a few days out, the guidance shifted significantly from out to sea to hitting land on Hurricane Fiona. Troughing further to the west could have put part of New England in play.
Another example is Henri. Just 48 hours before landfall the NHC forecast was for a strong tropical storm making landfall near New Haven. Then there was a hurricane warning. Then, just 24 hours later, right before landfall, Henri weakened on approach and made landfall in Westerly. Those are small changes that made a huge difference.
The point of taking the time to review our recent history and climatology is to emphasize that tropical systems are too powerful and complex to ignore or wait until the last minute to prepare.
Always choose preparation over panic.
With that, let's go to the forecast.
As mentioned right at the top, we expect a hyperactive season.
Named Storms: 28 (normal is 14)
Hurricanes: 13 (normal is 7)
Major Hurricanes: 6 (normal is 3)
Accumulated Cyclone Energy: 230 (normal is 123)
To put it in range form (for grading later)
Named Storms: 27-29
Hurricanes: 12-14
Major Hurricanes: 5-7
Accumulated Cyclone Energy: 190-245
With these activity numbers, 2024 would likely be a top 5 season in the historical record for the Atlantic basin.
The number of named storms isn't nearly as important as the number of hurricanes and major hurricanes. Named storms (read: tropical storms) can form quickly and be weak, whereas hurricanes and major hurricanes are more objectively strong.
Everything currently lines up for a hyperactive season. It's important to note that statistically, the more active a season is, the more likely the US coastline gets hit. I do expect that our streak of major hurricane landfalls in the US continues, though it's important to note that the last major hurricane strike on the East Coast that wasn't Florida was Fran in 1996. Jeanne hit the east coast of Florida in another historic season, 2004.
It does not matter when the first named storm or hurricane occurs when it's June and July. The overwhelming amount of activity happens in August-October. Very little can actually happen early in the season.
The only caveat to this is if we start seeing major hurricanes earlier in the season. Those are highly uncommon.
ENSO
Last summer brought us an El Nino, which normally suppresses Atlantic activity. While the season was a bit quieter than past well above average to hyperactive seasons, we still ended up with 20 named storms, 7 hurricanes, and 3 major hurricanes. This is in large part due to the warm Atlantic waters overcoming the atmospheric headwinds from the Nino.
This year is going to have no such barrier. The Nino is rapidly weakening and will likely fall to neutral territory as soon as next month. From there, a La Nina is expected to develop. This should bring an atmospheric response during the peak of the season that will be favorable for tropical cyclone genesis.
The Atlantic Multidecadal Oscillation (AMO) is a long term sea surface temperature anomaly pattern in the Atlantic. We have been in a warm phase of the AMO since around 1995, with no end in sight. This year in particular has a classic "horseshoe" appearance that suggests there will be less barriers to instability building in the MDR--which is essential for seedling waves to organize into tropical cyclones.
The West African Monsoon (WAM) feeds most of the tropical systems we see, because the vast majority of tropical cyclones and especially hurricanes/major hurricanes come from waves of convection that roll off the west coast of Africa. When the WAM is more active, as we expect it to be again this year, it means that we can expect the already impressive tropical waves we're seeing continue through the peak of the season this fall. Not all waves develop. In fact, it's important to have "sacrificial" waves that moisten the environment ahead of other waves. Sometimes big waves also push off dust from the Sahara, or the Saharan Air Layer (SAL). This could be a "fail mode" that holds back historic activity so it's something to be watched, but if the moisture and stability issues associated with an active SAL that have plagued the MDR are not as prominent this year, watch out.
If you've paid attention, this has probably gotten the most discussion in the news. Last year, these two factors combined to give us an active El Nino hurricane season. With a Nina likely this summer and fall, the historic warmth last year would have been cause to pause. This year however, we've seen truly unprecedented warmth in the Atlantic. It's not just that the Atlantic is much warmer than normal. It's that the extent of the anomalies, and depth of the warmth is unprecedented in the modern record as well.
First, let's look at absolute sea surface temperatures. You need 26 C temperatures to sustain a tropical system generally. These are temperatures that you should not see in many places early June but rather months from now. The top image (courtesy of Tropical Tidbits) is a June 6, 2024 SST plot. Compare it to the SSTs from late August (start of peak season) 2023. Note the Gulf, Caribbean, and area east of the Antilles.
For those interested in more technical analysis, also look at the colder temperatures in the subtropics compared to the MDR--that's a key signal, at least for now, that there won't be as many stability issues as prior years.
Immediately you see how 2023 and 2024 stand alone in warmth, and 2024 is on the path to surpassing 2023 with the additional support of a coming La Nina.
If you're still with me, I've thrown a lot at you. Let's wrap this up by talking about the most important part: preparation.
Preparing Long Before Any Threat
Preparation Over Panic should be your mantra. It is easier to take on storm preparation in bite size pieces than trying to do it all three days before a storm hits. The added benefit is that preparing for a hurricane also prepares you for something more likely, such as a severe thunderstorm.
June and July are not representative of what a season can be. It could be quiet for us all the way until September or October before there's something to watch. Don't let your guard down during the summer just because things may be quiet in the tropics. Quiet periods, even in active seasons, are normal. Remember however, the more active a season, the more likely something gets close.
That's all the more reason to prepare now.
Hurricane Strong remains a national resilience initiative that works to try to prepare residents for hurricane season.
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.
For inland folks, think about local flooding too. We're seeing bigger rainfall events, and those that are in vulnerable spots near rivers, creeks, and streams should be thinking about a plan of action if there is flooding as well.
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 that is elderly or vulnerable? Having a plan now will save you time and worry later. Do an insurance checkup as a key part of any storm preparedness plan.
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 is 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.
We should be preparing the same every year, regardless of the forecast.
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Thank you for reading and trusting SCW.
-DB