Good evening from Southern Connecticut Weather. 

The last two days brought increasing severe weather and widespread storms to Connecticut, but the heat has not fully broken. Tomorrow we expect the last hot and humid day under this hot period, but it will break as an energetic trough/front looks likely to bring another round of strong to severe thunderstorms to the state. The last two days the threat seemed relatively low and we saw scattered to unusually widespread severe/damage reports, complete with a confirmed EF-0 tornado in Harwinton yesterday and a supercell that brought tornado warnings to central Connecticut today.

The environment tomorrow looks even more robust on paper for severe potential. Tomorrow is a day to be weather aware no matter where you are.

Above: the latest SPC outlook for tomorrow. Most of CT is under a slight risk while parts of central and northern New England are under an enhanced risk due to the potential tornado threat. 

Severe Weather Perspective
Not all slight risk days are created equally, and these risk categories are forecasts just like everything else. Friday didn't have any tornado probabilities but we saw a lone tornado under the right conditions. Today started out with everyone in a marginal risk for severe weather, and by the afternoon I was frantically writing to tell locations to shelter in place because of a potentially tornadic supercell. The SPC identified the risk and put part of CT in a slight risk before the storms hit, which is great, but didn't issue a severe thunderstorm watch and we had multiple warnings over the course of the afternoon and evening. The bottom line, is that forecasting severe weather is extremely difficult, and because the risk is wide but the impacts tend to be local, everyone should be paying attention and not writing off anything. 

Tomorrow is one of those days where at least at this time the threat for severe weather looks higher than we'd normally expect on a "standard" slight risk day, but these things are never a slam dunk. 

First, although it is tempting, it's really important not to take the last two days of widespread strong storms and scattered severe weather as fully informing what happens tomorrow. Friday and today we saw storms take off under high instability and moisture, and just enough shear in the atmosphere for severe weather. The setup is different tomorrow in a meaningful way. 

Second, even though everyone should be on alert, truly severe weather--defined as 58mph wind gusts or higher, hail an inch in diameter or greater, or a tornado--doesn't happen for most people, even on "widespread" days. That's no reason to take severe weather potential any less serious, but it's important to keep perspective.  

Top: SPC tornado risk 
Bottom: SPC wind risk

The Overall Setup
It's important to look beyond the SPC probabilities above, which are impressive in their own right relative to what we usually see in CT. Note the higher probabilities to our north. 

Tomorrow will have all of the ingredients we need for thunderstorms, and many of the ingredients we need for severe thunderstorms. First, we will have more shear as a result of a trough (front) that will be advancing toward the state. This will allow for storms to potentially organize more efficiently than the last two days which had a lower shear environment. We will have lift with the energetic trough. We will have instability as tomorrow will be another hot and humid day, though there is a caveat here to be discussed shortly. Finally, we will have plenty of moisture, which will also be important to the forecast tomorrow. 

These ingredients combine to bring us an environment conducive for strong to severe thunderstorms, particularly storms that turn with height. In order to analyze severe weather potential aside from the new parameter metrics that you find, the fundamental tool is a sounding. This is a forecast of each layer of the atmosphere. 

Tomorrow the soundings for the afternoon all say the same. 

Above are the 18z 3km NAM soundings. There's a lot of information there that's hard to see, but these soundings for BDL, Hartford, and New Haven show a tornado sounding. That does not mean that each location will see anything close to a tornado tomorrow afternoon. It shows that the ingredients are present as forecasted on this one model. 

Let's look closer at the most recent sounding for Hartford from the 00z 3km NAM. Hot off the presses. 

Once again, this is a tornado sounding. The first thing to look at for that is up in the hodograph in the top right box. You can see turning with height, but at the higher levels you have a potential messier mode for storms. Today's supercell was able to take off today in central Connecticut because it was a discrete cell. It was the only game in town and as a result it did not have competition ahead of it to disrupt its maturation and cycling. That is a potential limiting factor tomorrow for tornadic activity. 

The second thing we see here are high dew points (green line) that gives plenty of low level moisture for storms. There is some dryness further up in the sounding so lapse rates look a little lower. That's another limiting factor. However, on the right side of the sounding you see high SRH, moderate to high CAPE, solid shear, and high moisture in the form of PWAT. 

One thing to note is the over 1200 J/kg of DCAPE. This kind of CAPE is often associated with strong straight line winds. If we do not have discrete storms tomorrow, we could see storms congeal quickly and form lines like we've seen the last two days, bringing heightened severe straight line wind risk. We think that's most likely tomorrow. 

Overall however, this setup is noteworthy for scattered to potentially widespread strong to severe storms. Adding to the tornado risk is the topography of the CT River Valley. This can be an area that develops a boundary that can further enhance turning with height, and pool moisture to overcome marginal lapse rates.

​On days like tomorrow, we watch that zone closely, just as we watch were the warm front in advance of the trough/cold front, sets up. Tomorrow that warm front looks to be in central New England, but as TW reminded us earlier, often times it's difficult to pinpoint were these fronts will go. 

Above: the 3km NAM depiction of storms between midnight tonight and midnight tomorrow. Not meant to be taken verbatim, but it shows the manifestation of the storms in the environment. 

The Forecast
Folks, tomorrow is a day to stay weather aware no matter where you are in Connecticut, but folks in northern and western CT need to be particularly vigilant. 

We expect additional showers and thunderstorms tonight, and some of those storms may be strong. There are severe thunderstorm warnings west so western CT should keep watch. 

Tomorrow should be hot and humid. We will be watching dew points as much as how much sunshine and destabilization we receive.

The timing of storms looks to be between 2-10pm. We really have to watch the earlier period to see if any discrete storms develop. Like today, any isolated storms could quickly become severe. Then we will be watching after approximately 5-6pm for a line of storms to congeal and bring a straight line wind threat through the state. Along this line we will be watching for notches that could cause brief spin ups, but the focus as it stands now would be on straight line winds with any line of storms. 

The greatest risk is likely to be in northern and western CT, but again, everyone should be weather aware tomorrow. Early day and early afternoon activities look fine, but be prepared to change on a dime depending on the radar. 

We expect an active day tomorrow. Stay tuned for updates throughout the day. 

A​s 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.

Thank you for reading and trusting SCW. 
​
-SCW Team (Written by DB)

Good morning from Southern Connecticut Weather. 

It was as good a weather weekend as you could get, with seasonable high temperatures, chilly nighttime lows, and dry conditions. In fact, despite being warmer than normal overall so far this June, we've had a number of beautiful days and the big rainfall periods have stopped--for now at least--as we're below normal in June rainfall. 

If you weren't paying attention, you'd think that this week will be a continuation of this beautiful stretch. 

Unfortunately, that's not the case. Now, while I think it's a good bet that someone who won't read this discussion will slide into the comments and claim that the coming heat wave is no big deal and is just typical "summer", folks that have followed SCW know that we don't do hyperbole. 

No, this isn't likely to be an epic all-time heat wave. No, this isn't something that folks need to be afraid of. However, there are a few things that make the coming heat wave notable, significant, and not typical summer.

First, the development of the heat wave is coming from a highly anomalous ridge of high pressure. You may have heard it being called the "heat dome". There is high confidence that the kind of ridge to setup over a very large part of the region will likely break June records for strength, and challenge annual records going back to 1950. 

Second, this kind of ridge, its placement, and its timing means that we're likely to experience an unusually strong heat wave for this time of year. Usually, our biggest heat comes in July. Both daily and monthly records may be challenged this week. 

Third, the duration of the heat wave is also going to be unusual. As a reminder, a heat wave is three or more consecutive days above 90 degrees. Those are common. What's less common is a stretch with highs above 95 degrees, and a stretch longer than three or four days. The impacts of heat on a person compound with the number of days the heat lasts. That's especially true on big heat days. 

This is likely to be a high impact and relatively long duration event for much of Connecticut. The coming heat is something to take seriously, even if we're not necessarily approaching all-timer distinction. 

Above: the 18z Sunday GEFS 500mb heights and anomaly depiction courtesy of Tropical Tidbits. This shows the movement, expansion, and amplification of a truly big ridge. For the most effective delivery of heat, you generally need to be north of the center of the ridge for southwest flow to advect in the greatest heat. As you can see above, Thursday and Friday look to be the days where the heat peaks. 

Monday
After another night of cool temperatures, the ridge is in place and will start to build today. That means that we start warming up with highs in the low to mid 80s inland. Along the shore, the theme will be a double edged sword. It will be slightly cooler with a southerly breeze, but humidity will be higher. The humidity today won't be too bad, but then the heat really begins. One thing to keep an eye on today is whether temperatures over or under perform.

Tuesday
The formal start to the heat wave is likely Tuesday. There are two things to watch. First, is the standard definition of heat wave. How many locations have consecutive 90 degree days and how many. The second is how many go and stay higher. Whether most hit 90--that's a near lock during the week. The second question of how many go and stay higher is much more tricky, even with consensus on the guidance about the strength of the ridge, because nuances like pop up thunderstorms, cooler than expected mornings, cloud cover, 850mb temperatures, and even wind direction will determine daily highs. 

​For coastal CT, temperatures will be lower, especially in SE CT because of the sea breeze, but like I said in the paragraph above, that means humidity and possibly lots of it. Inland, the hot spots of the CT River Valley will bake. Tuesday may be the easiest day of them all, too. At the shoreline, while the temperatures don't look record breaking, the duration of the heat will be notable. 

An Excessive Heat Watch has been issued for Hartford and Tolland counties, the first in over a thousand days for inland CT. 

Above: IEM (Iowa State) data on the last time an Excessive Heat Watch was issued. ​

Above: the current listing of watches and advisories. These may change depending on the heat and heat indices this week. Even SE CT should be prepared for hot and humid conditions, though the intensity of the heat will be least there. 

Wednesday
By Wednesday, we're kicking the heat into high gear. Inland areas should be in the low to mid 90s, but humidity is likely to be up a bit and for the hot spots, upper 90s are on the table. 

Above: GFS (top) and Euro (bottom) depiction to temperatures Wednesday early afternoon. These are not necessarily the highs for the day. Both model runs are from yesterday. 

Thursday-Friday
The end of the week is the period to watch for the highest heat. This is when the ridge starts to slide south, putting us in the region where the greatest heat advection is likely. This is where we go from run of the mill heat wave to higher end, should Tuesday and Wednesday fall a little short temperature wise. Expect higher humidity and temperatures in the upper 90s to near 100 for inland spots, and even at the shore, temperatures may reach over 90 in addition to potentially oppressive humidity. Heat indices over 100 are likely around the state. These are certainly the days to limit outdoor activities and check on the vulnerable. Nighttime temperatures will not fall that much, providing little relief to many. 

Each of these days, but especially Friday, will have the chance for pop up thunderstorms. These could be quick strong storms due to the amount of instability that builds. 

Now, let's talk about rarity. Yes, much of inland Connecticut sees temperatures in the mid to upper 90s during the summer. I wrote about that in our summer forecast. However, we don't see these kind of temperatures this early, and the duration of 95+ temperatures is rare. 

Thursday and Friday have potential to reach 100 degrees at both Hartford (city) and BDL. The last time BDL saw 100 degree temperatures was July 21, 2019. For Hartford (HFD), it was July 22, 2016. For either to hit 100, it would be the earliest on record. 

The last time BDL or HFD hit 100 in June, it happened in 1964 for BDL and 1952 for HFD. 

In fact, analysis from the fantastic Tomer Burg shows how anomalous June highs near 100 are. Even during the peak of the season, we hit 100 less than 1 out of every 3 years inland, and as you can see above, it hasn't happened recently. 

More important however, is the duration. Our record long heat wave using the 90 degree threshold is just 10 days in Connecticut. We're unlikely to top that here. However, for heat above 95 degrees, there's an outside shot of cracking the top 10-15 at BDL and HFD.  

When the temperature threshold is raised, the potential heat wave becomes more rarified, but first we have to see the temperatures get there. 

Saturday-Sunday
The heat wave is likely to extend into the weekend. The guidance is split however over just how long and intense the heat is. The Euro, which was once the most aggressive model, has pulled back substantially, while the GFS, has become more aggressive. This is a notable shift, but for now, I will expect the heat wave to continue through at least Saturday. Even if the heat declines, the humidity isn't going anywhere. 

Heat Precautions
During this period it's important for everyone to take heat precautions. The human body doesn't care about historical records. First and foremost, never leave kids or pets in the car. Each year, deaths happen around the country, even in cooler temperatures, because cars heat up extremely fast and can overcome anyone sitting in it on a warm to hot day. 

Heat is the leading weather related killer in America. This happens because folks don't have access to cooling, and because people underestimate the heat. Don't be one of those people. Stay hydrated, check on the vulnerable, and if you don't have access to air conditioning at home, know where your cooling centers are. If you work outside, it's essential that you take breaks and stay hydrated. 

With the big golf tournament likely during the peak of the heat, spectators and volunteers alike need to take extra precautions given the extended amount of time outside. 

Know the signs of heat illness and be sure to take quick action if you or anyone else around you starts to show signs. 

The Dailies
Monday: Mostly sunny. Warmer and more humid. Highs in the low to mid 80s. 

Tuesday: Mostly sunny and hot. Highs in the low to mid 90s inland, mid to upper 80s at the shoreline. Heat indices of 95-100. 

Wednesday: Mostly sunny and hot. Highs in the mid to upper 90s inland, mid to upper 80s at the shoreline. Heat indices of 100-105+.

Thursday: Mostly sunny and hot. Highs in the mid to upper 90s inland, upper 80s to low 90s at the shoreline. 100 degrees possible inland. Heat indices of 100-105+. Chance of thunderstorms 20%. 

Friday: Mostly sunny and hot. Highs in the mid to upper 90s inland, low to mid 90s at the shoreline. 100 degrees possible inland. Heat indices of 100-105+. Chance of thunderstorms 40%.

Saturday: Mostly sunny and hot. Highs in the low to mid 90s inland, upper 80s to low 90s at the shoreline. Chance of thunderstorms 20%. 

Sunday: Mostly sunny and hot. Highs in the upper 80s to low 90s inland, mid to upper 80s at the shoreline.

Bottom line: a high impact and long duration heat wave is set to hit the region this week. While not unprecedented, it's something to take seriously because of the duration and potential for multiple days of high end heat. 

​A​s 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.

Thank you for reading and trusting SCW. 

​-DB

Hello from Southern Connecticut Weather. 

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. 

Waves battering the Connecticut shoreline from the last hurricane to landfall in Connecticut: Hurricane Gloria in September 27, 1985. Image courtesy of the Hartford Courant.

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. 

Our Recent History
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.

Above: the best track positions for Hurricane Lee, courtesy of the National Hurricane Center (NHC). Graphical images below will also come from the NHC postseason tropical cyclone reports. Note how Lee was a category five hurricane in the open Atlantic before its turn north, and still a hurricane east of our region. 

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. 

Above: the best track positions for Hurricane Fiona, and the video of the damage survey I took in the location that saw the highest recorded wind gusts in Nova Scotia. Note the extensive tree and in some instances structural damage. 

​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. 

Tropical Storm Fred was also a Gulf system but this one stayed inland. This means it wasn't a tropical storm when it approached CT, but the impact was all the same with the system bringing additional heavy rain and a confirmed tornado in eastern CT. 

Hurricane Henri, the last storm to bring hurricane warnings to the CT coastline, followed right on the heels of the remnants of Fred. As you'll see below, Henri had a unique track. Normally, our hurricane impacts come from systems buried in the Bahamas, and are often long track hurricanes from the Cabo Verde islands. These are often the most powerful hurricanes that the Atlantic produces as they track for long periods of time over the very warm waters of the Main Development Region (more below). 

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. 

Finally, our active 2021 concluded with a truly historic event. 

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. 

2020: The Warning Shot--Hurricane Isaias
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. 

New England Tropical Climatology
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.

Above: a graphic showing the annual return period for a hurricane based on location. Looking at a longer period of record however shows a slightly different (and more frequent) story for New England. 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. 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.

Above is the GFS showing the overall progression of the system. Off the SE coast, there is Isaias. Contrary to popular belief, the powerful hurricanes we see are little more than a leaf floating on an atmospheric river, and are very sensitive to the position and strength to troughs and ridges in the upper levels of the atmosphere.

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". ​

Above is another visualization of what I'm talking about. Looking at the upper levels, for a landfalling New England hurricane you need a strong ridge over Atlantic Canada blocking the escape route as a trough is centered in the Great Lakes. These are usually very narrow "windows", which keeps us safe most of the time. This fantastic composite image is courtesy of meteorologist Eric Webb. 

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. 

Satellite image of Hurricane Gloria just off the Carolina coastline in September 1985. It has been nearly four decades since our last Connecticut (and New England) landfalling hurricane. We're overdue looking at the last 175 years of records but whether that happens this year or a hundred years from now is impossible to know. 

The 2024 Atlantic Hurricane Season 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. 

Forecast Factors
​
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 La Nina atmospheric response is the opposite to a Nino usually, with the eastern Pacific seeing less activity, and more instability and less wind shear in the Atlantic Main Development Region (MDR). This increases confidence in not only more hurricanes developing, but more major hurricanes developing in the MDR. 

AMO & WAM
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. 

Sea Surface Temperature & Oceanic Heat Content
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. 

Here's another comparison, looking at Oceanic Heat Content (OHC). The June 2024 OHC is just incredible. 

Finally, to put these images in context, let's look at the most recent daily average SST in both the MDR and an isolated look at the Caribbean. This data covers the years 1982-present and is both created and updated by the fantastic Dr. Kim Wood of the University of Arizona.

​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. 

The above factors give me high confidence that this is a well above normal season, and moderate confidence that this is a hyperactive season. 

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.  

A​s 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.

Thank you for reading and trusting SCW. 

​-DB

Hello from Southern Connecticut Weather! 

Spring in Connecticut was fairly quiet, and at times characterized by very wet and warmer than normal conditions. With the exception of a few isolated severe storm days and a lot of clouds, there hasn't been a lot to talk about. Spring tends to be our quiet season, and with the warmth that arrived just before Memorial Day, it looks like we've stepped into summer, even though the humidity has been mostly absent for now.

Meteorological summer begins today and lasts through August 31st. Summer is when we ramp up from the relative quiet of spring to the peak of our heat and thunderstorm season. This time of year also overlaps with the Atlantic hurricane season, though the peak of that season arrives in September. 

It's not a surprise that we're expecting summer to be warmer than normal. That tends to be the default state these days, though last summer our temperatures were about as close to normal as you could get. The tradeoff for that however was a near record wet summer. 

The ENSO state changing from El Nino to La Nina informs this forecast greatly, along with some teleconnections--though they do not correlate as much to sensible weather as during the winter. 

Given what we expect in the predominant upper level pattern, we do think that it will get more humid than normal and as a result of that flow, a little more active and solidly wetter than normal. 
 
Grab an iced coffee or cold brew and settle in. 

Above: the official NOAA forecast for ENSO for the remainder of 2024. There are high probabilities that La Nina sets in shortly as sea surface temperature (SST) anomalies are rapidly cooling in the key region off the west coast of South America that measures the presence of El Nino (warmer than normal SSTs) or La Nina (colder than normal SSTs). 

Below: the latest global SST anomaly analysis. There is a lot to unpack in this one image, but for the purposes of this section, you can easily see La Nina trying to build. ​

Connecticut Summer Temperature Climatology
Before we go to predictions, let's talk about what summer generally looks like in CT. ​

Above: the average high and low temperatures at BDL (Bradley Airport) and BDR (Bridgeport Airport). This plot goes back to 1951 to add a longer period of record. Average temperatures rapidly rise in June, followed by the peak and plateau in July, start of a gradual decline in August, and a steeper decline that occurs with the annual march to fall in September. Image courtesy of the fantastic Iowa State University Automated Data Plotter. 

The image above tells us that average highs are in the mid to upper 80s by the latter half of July, but they don't tell the full story of what's normal for us. 

There is a lot of data in the graphics below--also looking at BDL and BDR, but they are very helpful in showing us the different types of summers we get here in CT. 

High Heat
This type of summer is defined by relatively brief, but extreme periods of heat. For us in recent memory, 2011 is that season, where both Hartford and Bridgeport tied or set new all time record high temperatures just shy of 105. A season like this is defined by days or brief stretches where the high is 100 or greater. 

Durational Heat
Another type of summer is defined by long periods of high, but not necessarily extreme heat in an absolute sense. Think of long heat waves. This is a sneaky kind of heat because the duration makes it extreme. The impact on the human body amplifies when the heat is extended out longer, even if it's not record breaking daily maximums.

​For this type of summer, 2002 fit the bill in Hartford--look at the number of days that reached 95 when the yearly average is around 20 days at 90 or above. At the shoreline, 2016 was a hot one with 18 days reaching 90 when the average for the year is about half that. A season like this is defined by long heat waves or frequent short heat waves. 

Ho Hum
These are increasingly rare, but they're the normal (or near normal) type of summers where there's a lot of "chamber of commerce" type days that are beautiful with lower humidity and heat, and other periods where we have a heat wave, or close to it. It's warm to hot, but not all the time or overwhelmingly so. These are seasons defined by mid-July temperatures that frequently top out at 83-85 rather than 90 and above. 

We do have another type of summer however, and that's what we're predicting this summer...

SCW Summer Forecast: Temperature

Sultry Summer
These are probably the most uncomfortable kind of summers, even if the high temperatures aren't particularly memorable. They're sweaty, sticky, and plenty humid. It's far easier to achieve high heat when dew points are mixed out, but these are the kind of summers where you lose a few degrees of actual temperature and add a few degrees to the heat index because of all the moisture in the air. 

This is highly dependent on the upper level pattern. If we have strong Western Atlantic Ridging (WAR), which I do expect as we move deeper into summer, that will transport moisture from the western Atlantic and potentially the Gulf of Mexico, which are running warmer than normal. The warmer the temperatures in these regions, the more moisture that can be transported. Even though our actual sea surface temperatures are much colder than further south in an absolute sense, the anomalies set the stage for periods of elevated to oppressive humidity. Our dew point peak coincides with our highest annual temperatures but are more of a plateau, with low to mid 60s dew points as part of our daily average from late June through at least mid-August. 

With total 90 degree days being around 20 for BDL and 10 for BDR, I expect us to be slightly above normal in that category. The bulk of this heat will be in July and August as La Nina establishes itself right as we reach our climatological peak. It may not be hot now, but eventually it will be. 

The summer will be more memorable in the humidity category than the absolute temperature category, though keep in mind Hartford averages days in the mid to upper 90s while the coast gets hot days as well, though not as frequently. 

Above: the current SST anomaly analysis. This is the kind of map that combined with a La Nina lends itself to hot and humid summer conditions. Image courtesy of TropicalTidbits. 

Connecticut Summer Severe Thunderstorm/Tornado Climatology
Now let's talk about a normal CT summer when it comes to severe storms. The last 20 years have been very active on balance. 

Above is an accumulated line plot which shows the number of severe thunderstorm and tornado warnings combined for each year going back to 1986. On the right, you'll see the data itself, showing 11 warnings (I believe all severe thunderstorm warnings) so far in 2024, around normal. You'll see that once we get to summer, things go up dramatically, and the bulk of our warnings happen in summer and early fall. 

In order for severe thunderstorms to develop you need four key ingredients: Shear, Lift, Instability, and Moisture. 

Shear
In order to get a severe weather day, we need some sort of shear. You can have a high CAPE/low shear or high shear/low CAPE day, but you need shear for severe weather. 

Shear—is the change in wind speed (speed shear) and/or direction (directional shear)  with height in the atmosphere. Shear usually refers to vertical wind shear.

Speed and directional shear are important in severe thunderstorm development. With speed shear, a significant increase of wind with height will tilt a storm’s updraft. This allows an updraft and downdraft to occur in separate regions of the storm and reduces the risk of water loading and thunderstorm collapse. 

Directional shear helps initiate the development of a rotating updraft. This is key in the formation of a supercell—the most mature and dangerous type of thunderstorm. Supercells are thunderstorms consisting of one quasi-steady to rotating updraft (I.E. storm with rotation). These are the storms most likely to produce large hail, strong winds, and tornadoes. It doesn't need to look like the picturesque Midwest supercells to be dangerous. We saw that with supercells that produced hail in eastern CT and damaging winds in Griswold recently. 

What to watch for: areas of low pressure, especially tropical systems or upper level lows. 

Lift 
Lift is a critical ingredient for thunderstorm development, even the garden variety type. You can have moisture and instability, but if you don’t have lift, not much is going to happen. Lift provides the air the nudge it needs to rise and form convection. It happens a number of ways around the country, but in this region, we’re usually looking one major mechanism: a front. ​

The most common mechanism around here for thunderstorm initiation is the cold front. Fronts are the boundary between two air masses of different temperatures and air densities. When the cold front rolls through, the colder and more dense air behind the front lifts warmer and less dense air abruptly. When all the ingredients are together in the right quantities, you have showers and thunderstorms. In less frequent scenarios, we have warm fronts lifting north across the region. These are particularly noteworthy because they usually happen in an environment that is more favorable for supercells and tornadic activity. Another way in which lift can happen is along a sea breeze boundary that moves north during a summer day. 

Instability
Instability is another critical element of thunderstorm production, and the more instability there is, the more potential you add to a developing storm. 

Instability is the tendency for air parcels to accelerate (especially upward) when they are displaced from their original position. You don’t need a lot of instability for a garden variety thunderstorm, but you need Instability and usually significant amounts of it for for severe weather.

An unstable air mass is usually characterized by warm moist air near the surface and colder drier air aloft. This allows air that is forced upward to continue to rise on its own, which eventually will cool and develop the clouds and precip that make up a thunderstorm. High instability also contributes to prolific lightning events, which isn’t characterized as severe weather by the NWS but is deadly in its own right.

What to watch for: Convective Available Potential Energy, or CAPE—is a measure of the energy available for convection. CAPE is directly related to the maximum potential vertical speed within an updraft. 

As the National Weather Service notes, observed values in thunderstorm environments often exceed 1000 joules per kilogram (J/kg), and in extreme cases may exceed 5000 J/kg. Now, 5k CAPE around here is unheard of, but If we’re talking about a high CAPE day, your ears should perk up. 

There are various measures of CAPE out there, including surface based CAPE (SBCAPE), mixed layer or mean layer CAPE (MLCAPE), most unstable or maximum usable CAPE (MUCAPE), and downdraft CAPE (DCAPE). 

Moisture
Think of a hazy, hot, and humid summer day. If you asked people what they remember about the end of those days, many will answer that they remember the thunderstorms. Moisture is a key element in thunderstorm development. Without moisture, you’re not going to have precipitation!

What to watch for: if you want to know what kind of moisture we’re dealing with during this time of year, look at the dewpoint—which is a measure of atmospheric moisture. A dew point is the temperature to which air must be cooled (generally) in order to reach saturation. The higher the dewpoint, the more moisture in the air.

This was a key factor in last year's storms that dumped obscene amounts of rainfall, often in very little time.

As you can see above, each year we can expect a few dozen severe thunderstorm warnings and less than a handful of tornado warnings. Tornado warnings are tricky in CT, because they are often happening extremely quickly and are short track events. Images courtesy of Iowa State University. 

SCW Summer Forecast: Storm Activity

Active Summer
This summer is poised to be another active one, in line with some other recent years, as we look at severe warned numbers. I think this is in large part due to the predominant upper level pattern once again, which should allow for higher humidity and thus moisture to be present in the state. It's unclear how many fronts we get during the peak of the summer, but if there is more of a "heat dome" as is expected in the central US, that could put us in a "Ring of Fire" setup periodically that would allow for more thunderstorm activity. 

Above: an old Weather Channel graphic that helps visualize a Ring of Fire setup. An expansive heat dome over the Midwest or South forces energy to move around the periphery of the ridge, bringing active weather to the east. This is a setup I expect to see a couple times this summer as the Midwest deals with significant high heat. The counter to this is that I do believe at some point we will see more ridging in Atlantic Canada, which will make the Ring of Fire less likely. We will see how quickly, if at all, that develops. 

Much like the temperature forecast, I don't think this is an overwhelmingly stormy summer, but we'll have near to slightly above normal severe thunderstorms. It should be active. Tornadic activity is near impossible to predict in this region long range. ​

Above: thunderstorm life cycle with image courtesy of iAlert. 

​Connecticut Summer Precipitation Climatology
Finally, let's talk about water. We've had a lot of it in the last year, and for our corner of the country, we've been one of the wettest places in the entire lower 48 relative to normal in the last year. A lot of that started last summer, and continued straight through today. Summers usually have wet periods, but not this wet. 

Above: precipitation departures dating back to this time last year. Not only are we one of the wettest spots in the country, we have seen feet of rainfall greater than normal. Images courtesy of the NRCC. 

We know that summer is usually good for a few solid thunderstorms and even heavy showers. Last year kicked off a really bad series of storms that produced prolific rainfall totals and rates due to increased humidity and lack of forcing--enough to keep storms moving along. 

Flash flood warnings are part of our summers, but last summer was historic. 

Above: the flash flood warning count for the state going back to when the statistic was kept. It may not look like much, but 30 summertime warnings is a significant length ahead of the other active years.

SCW Summer Forecast: Precipitation

Wet Times Continue
It would be truly extraordinary, and I daresay unprecedented, to follow up an exceptionally wet summer 2023 with an even wetter 2024. Last year was unique in that the rainfall all happened absent the influence of a tropical system. 

While I think we won't be as wet as last summer, I do think we will be solidly wetter than normal, on the order of 110-130% above normal. Even this statement has me nervous for a few reasons. 

First, I do think that the increased moisture in the air will lead to additional high precipitation events, some localized via thunderstorms and other more widespread due to fronts or the occasional trough. It's unclear how frequently this happens. 

Second, we are expecting a historically active Atlantic hurricane season. For the purposes of this forecast, we need not assume a direct impact to receive a lot of rainfall. We only need to look at the remnants of Ida or Elsa or Fred a few years ago to see the impact remnant rainfall can be.

This is a big variable, and if I were to hazard a guess, I would say we get some significant rainfall from at least one tropical system this summer, likely in the latter part of the summer as the tropics become more active. That alone could make this forecast too low. 

Above, a radar image of Tropical Storm Elsa in July 2021. Elsa dropped between 2-6" of rain, more than a month's worth in spots, on the state. 

Overall Forecast
SCW expects to be busy this summer, as a combination of heat, storms, and wet weather will ensure an active summer. 

• There is high confidence that this is a warmer than normal summer with regard to temperature, though the most memorable aspect of the heat will be the long duration of humidity. 
  
  
• There is moderate confidence that this is a more active severe thunderstorm season than normal, though only slightly above, due to the likelihood of central US and western Atlantic ridging alongside possible troughing to our west pumping moisture and potentially giving a few active storm periods. 
  
  
• There is high confidence that this is a solidly above normal rainfall season, continuing the general trend of the last year. How the tropical season factors into this eventual outcome remains to be seen. It wasn't mentioned before, but I do not think this wetter than normal forecast necessarily means a continuation of the overcast skies that dominated our winter and spring. Climatology should give us sunny and dry periods. 

Hopefully you found this overview and forecast to be informative and interesting! Let's see how the forecast pans out.

A​s 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.
​
Thank you for reading SCW.
​
​-DB