Good evening from Southern Connecticut Weather! 

While we've psychologically turned the page to fall, it officially begins on Tuesday. The week ahead looks cooler than normal, but the main story is the high uncertainty we have with a possible coastal storm at the end of the week. Let's dive in. 

Above: the 12z European AI depiction of pressure anomalies for the coming week. This gives us a sense of the strength/orientation/position of high and low pressure systems. Most of the week is under the influence of a Canadian high pressure, but then we watch the development of a coastal storm. 

Monday
So far this month, we've been wetter than normal, and around normal in temperature. In fact, for both Hartford and Bridgeport, temperatures for the month so far are within one degree of normal. Hartford has been right around normal in terms of rainfall, but many have not. 

The week ahead will be colder than normal, in large part due to the Canadian high that you see above. As we move into the final third of September, our average high temperature is in the mid 70s and falling, and for most of the week ahead we're going to be hard pressed to get out of the 60s. 

Tomorrow the showers that linger tonight will fade, but with a northeasterly wind, it will be a cool and partly to mostly cloudy day. We should be dry after the morning, but it's just an ok day.

Tuesday-Wednesday
Our Tuesday and Wednesday look dry, but I want to keep very slight chances for showers/drizzle as a weak system tries to slide up underneath the state. That said, the overall forecast is pretty mundane, with more northeasterly wind, cool temperatures, and partly to mostly cloudy skies. We should start to see a coastal storm take shape well to our south, but that won't impact us during the first part of the week.  

Above: a high resolution NAM depiction of surface conditions Tuesday into very early Wednesday. I think we stay dry, but there could be some isolated showers/drizzle around, especially in the southern portion of the state. 

Thursday-Sunday
This is a large block of time, but they are grouped together because this is when we are most likely to see impacts from the main weather story of the week--a coastal storm that is expected to develop offshore. Much like a typical fall or winter storm, the signal for a storm has been there for a few days thanks to the upper level pattern, and I have high confidence that a storm of some sort will form. Aside from that, however, there is a lot to sort out. 

Across guidance, we see a sprawling storm that works its way up the coast as high pressure remains in place to our north. It could be a standard nor'easter, or it could be a subtropical or "hybrid" storm with a mix of tropical and baroclinic features. That doesn't matter for us as much in terms of impacts because at the very least the pressure gradient between the low and the high pressure will make this period breezy. How windy we get however will depend on the strength and track of the storm. 

The GFS, which seems to be an outlier at the moment, keeps the most impactful part of the storm well offshore. Even so, we would have at least one day (Saturday) of rain and possibly some coastal flood issues. 

Above is just a depiction from the GFS of the storm at its closest. I'm discounting this currently as it is an outlier among guidance. 

Most of the other guidance tells a very different story, with our low becoming a potent early fall storm that hugs the coast, bringing multiple days of rain. Here is the 12z Euro depiction for the storm. The details matter far less than the overall picture--there's the chance we see a rainy and windy storm in the latter portion of the week, that could bring coastal flood issues depending on track. 

Our split weekend streak with beautiful Saturdays and rainy Sundays is at risk--this time the whole weekend is at risk. Stay tuned as we continue to monitor this storm. 

The Dailies
Monday: Rain showers possible early. Mostly cloudy and seasonably cool. Highs in the mid to upper 60s. Chance of rain early 20%. 

Tuesday: Mostly cloudy with a chance of showers. Highs in the mid to upper 60s. Chance of rain 20%. 

Wednesday: Partly cloudy and cool. Highs in the low to mid 60s. Chance of rain 10%. 

Thursday: Partly cloudy. Highs in the low to mid 60s. 

Friday: Mostly cloudy with a chance of rain. Breezy. Highs in the mid to upper 60s. Chance of rain 30%. 

Saturday: Mostly cloudy with rain. Breezy. Highs in the mid to upper 60s. Chance of rain 50%. 

Sunday: Mostly cloudy with rain. Breezy. Highs in the mid to upper 60s. Chance of rain 50%. 

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

Good evening from Southern Connecticut Weather. 

The high heat of July has faded away. The bite of the summertime sun has diminished some. The days are getting shorter. Time marches incessantly, but when it comes to weather and seasonal change, when the transition picks up in earnest varies by year. Some seasons, like last summer, the march toward fall began early, right around the time we turned the page to August. Pretty unusual. 

Some years, the seasonal transition happens late. Think of the many recent winters where the start of it resembled extended fall more than winter itself. 

For those new to us, while the march toward another season technically begins as soon as an astronomical season begins, we write around the time the seasonal change becomes more notable. Summer is not over. There will still be warm and humid days, but change is in the air, and it's time to talk about it. The biggest question we've gotten after an extraordinarily wet summer and building El Nino is...will our wet pattern will continue into fall? 

Above: a plot showing the departure of precipitation from May 25, 2026 through August 22, 2026. This was before even more rain fell today. As you can see, virtually all of Connecticut is well above normal through most of Meteorological Summer, even though the first month of that summer (June) was well below normal. 

Recapping Summer
I don't want to jinx the last week of Meteorological Summer, but it looks pretty quiet--at least for most of the week. Winter, spring, and the first third of summer were very dry, but in July, the flood gates opened, in some cases, literally. Our pattern shifted in a big way, with a combination of high humidity, frequent thunderstorms in some parts of the state, and several unusual summertime synoptic storms--think of our coastal non-tropical systems focusing heavy rain along a warm front--leading to what seems like weekly deluges. 

As you can see above, it's been wet! Parts of southern CT especially have seen upwards of two feet of rain between late June and now. That has all but wiped out significant rainfall deficits across the state. 

We've gone from virtually the entire state being 3-6" below normal...

To the departure being wiped out... 

The image above is a bit deceiving. While it looks like northern and eastern CT is in a deficit, BDL and Groton are now ever so slightly above normal for the year, while Bridgeport is nearly five inches above normal for the year while being nearly five inches below normal as of July 1! 

I expected an active summer with several troughs moving into the region, and that's proven to be right. However, I also expected a near to just above summer for precipitation. While that was a big departure from the previously dry six months, it wasn't enough. With a week left, Bridgeport has already broken the record for the wettest summer on record. This was a record that stood since 1972! 

As for temperatures, I expected a slightly warmer than normal summer, and with seasonable temperatures likely the final week of Meteorological Summer, it looks like this will be spot on with departures not too warm. I thought the Nino would lead to a more humid than hot summer, and that's proven to be true. Once again, summer humidity has been the story outside of the big heat wave in July. 

First Look at Fall
We're writing this now because the seasonal transition is accelerating to the point that it's meaningful. The last 90 degree day at BDL and Bridgeport was on August 9. Although the humidity has still be around, believe it or not it's been on the decline as well. Guidance is now united in bringing more persistent troughing in the coming weeks, meaning cooler conditions on balance, more rain, and a continued decline in warm and humid days. 

Above: 12z EPS 500mb projections. Note the frequent periods of troughing all the way into September. With a ridge in the south we will still see periods of humidity, but this looks like a heralding signal for moving toward more fall like weather, especially as we turn the page into September. 

The El Nino event is strengthening, and I think it will continue to have a significant impact on our weather, which is interesting considering that it hasn't been the case (yet) for other parts of the country. The plot that I shared when looking at the summer forecast ended up being pretty wise, as we ended up much wetter than normal. Updating it with similar strong and ascending El Nino events in the fall, both the temperature and precipitation composite analogs show a near normal fall. 

That said, it's important to look at current conditions and how the overall pattern has evolved. I think we're right around normal for temperature in Meteorological Fall, which runs from September through November. I think there's at least one month in there that runs below normal temperature wise. It's just hard to forecast a season to be below normal with the warmer background state in our climate. 

As for precipitation, I think a big part of the deluges we've seen this summer has been the oppressive humidity. Summer is a time when we can see very efficient rainfall due to the amount of moisture in the air, and the seasonal transition subtly removes that moisture and humidity. So as we see fewer high humidity days, I think we see fewer weeks with downright deluges. We're also past our summer thunderstorm peak climatology, so that also helps reduce the chances of big rain events. 

That said, we start to transition from summer rainfall events to more nor'easter type events, especially as we get deeper into fall. So while the higher end rain events will start to decline in the coming weeks, I do still think we end up in a continued active and generally wet pattern. I don't think it's nearly as wet as summer, but perhaps slightly above normal. 

Updating the Winter Outlook
With a strong El Nino all but a guarantee and likely peaking or holding during winter, I just wanted to take a second to update some of the strong Nino analogs. Not much changed on the temperature front. It's going to be hard for the northeast to escape a warmer than normal winter. 

Much more goes into the winter forecast than just ENSO, but warmer than normal and wetter than normal continues to be favored. 

​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.
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Thank you for reading SCW.

​-DB

Good evening from Southern Connecticut Weather! 

What a weekend! After a beautiful Saturday which featured some isolated showers late, we had an even better Sunday with seasonable temperatures and low humidity. Summer heat will return this week, and as we move further into July we gradually climb toward the peak of summer warmth. Let's dive in. 

Mid-July Climatology
Before looking at what should be a mostly quiet week ahead, let's take a quick look at what's normal for this time of year. July is our warmest month historically, which makes sense as summer reaches its apex. 

As of today, July 12, the average high/low temperature at BDL (Hartford) is 85/64, and those averages continue to rise gradually until we peak in the coming week. Officially, BDL will hit its highest average high temperature of 85.6 on July 15 and then hold for a few days before we see a decline starting July 23. At Bridgeport, we reach our highest average high temperature of 83.8 on July 16, and begins to decline on July 26.

Of course, we can get plenty hot after the peak of the season--averages are just averages after all--but the climate record is clear: much like a roller coaster, usually after that brief but extended moment at the top, the descent is fast. We're not quite marching toward Fall yet, but it's coming...

The Week Ahead
The nice temperature regime from this weekend will be a distant memory this week as a big ridge of high pressure currently bringing historic heat to places like Montana and Utah shifts east. We will not get the worst of the heat by a long shot, but our predominant flow will change, reintroducing heat and humidity to the region. 

Above: An EPS projection of the 500mb heights over much of North America by Tuesday afternoon. Note that the center of the ridge is to our west and we're once again on the line of a ring of fire pattern. This time, it may keep the storms to our north with some possible exceptions. 

Monday
Tomorrow will continue our dry period but we will see increasing temperatures and humidity levels. There's an outside chance a place like BDL hits 90, but I think for most of us the mid to upper 80s will be where we land. Chance of showers/storms looks very low. 

Tuesday-Thursday
This is the period where another heat wave is possible, especially inland. We will see the heat and humidity ramp up in a big way, and highs in the mid to upper 90s are possible inland on Tuesday and Wednesday. Combine that with high to oppressive humidity and heat advisories are possible for heat indices near to just over 100. Now, this isn't anything like the big heat wave we recently had around July 4th, but heat is heat if you're not staying hydrated and practicing heat safety guidance. Just be a little extra cautions, and for those sensitive to bad air quality be prepared for some poorer air quality potential on Tuesday and Wednesday.

Tuesday will have strong to severe thunderstorms well to our north in Canada and Northern New England, and it doesn't look like the risk will extend down here. Wednesday could bring a greater risk of storms, but for now, it's just something we will keep an eye on. 

Above is a GFS plot of possible temperatures Tuesday through Wednesday. Expect 90s each day including down to the shore. Thursday likely brings our last day of 90s for the area, but temperatures should be coming off their peak by this point. 

Friday-Sunday
Being on the edge of the ring of fire pattern, if the ridge shifts a little we could be in for increased chances of showers and thunderstorms as ripples of energy move fast through the steering flow. That looks possible as a trough tries to develop toward the end of the forecast period and the ridge gets suppressed south.

However, for now, there doesn't look to be a locked in heightened risk of showers/storms, just increasing chances generally. Temperatures will fall below 90, but still remain in the seasonable to seasonably warm range. Humidity should drop briefly after the heat breaks, but we start warming back up pretty quickly--as is usually the case during the peak of summer. 

The Dailies
Monday: Mostly sunny and warmer. Highs in the mid to upper 80s. 

Tuesday: Hazy, hot, and humid. Highs in the mid to upper 90s and a touch cooler at the coast wherever there is a sea breeze. Chance of storms 10%. 

Wednesday: Hazy, hot, and humid. Highs in the mid to upper 90s and a touch cooler at the coast wherever there is a sea breeze. Chance of storms 30%. 

Thursday: Hazy, hot, and humid. Highs in the upper 80s to low 90s. Chance of storms 10%. 

Friday: Mostly sunny. Highs in the low to mid 80s. 

Saturday: Partly sunny. Highs in the low to mid 80s. Chance of storms 20%. 

Sunday: Partly sunny and warmer. Highs in the mid to upper 80s. Chance of storms 40% 

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

Good afternoon from Southern Connecticut Weather. 

So far, we've been mostly spoiled with seasonable daytime temperatures and modest humidity at best. That's all coming to an end as we close June and enter July. While July is historically our warmest month of the year, interestingly, in the last couple of years we've had our hottest temperatures occur outside of July. Well, that looks unlikely this year, as guidance has been hinting at the potential of a higher end heat wave. Let's dive in. 

Above: The NWS Heat Risk graphic, showing the potential for major heat related impacts in CT and extreme heat impacts in much of Connecticut as early as Wednesday. Heat Risk is something that's been around a few years and it takes a more wholistic look at how the heat and humidity on that day could impact the population. It's a useful tool that helps us separate standard summertime heat from something higher end. 

The Pattern Shift
The overall pattern in the week ahead is actually straightforward. For months, we've been dealing with modest to strong troughing over our part of the world, which has helped keep temperatures in line for the most part. That's going away for a while as a strong ridge develops over the central U.S. and opens the door for heat and humidity to get advected into the region. 

Above is a look at the European Ensembles (EPS). Note how at the very start we go from a more zonal pattern to an amplified pattern as a big trough in the western U.S. that's actually bringing snow to the higher elevations is pumping our ridge over the central and then eastern part of the country. One other thing you may see is the potential for the flow to favor thunderstorms in a "Ring of Fire" kind of pattern, rather than a more traditional hot and dry every day until the big bang at the end kind of heat wave. 

How far east the ridge extends and how strong it is--two things we do not know with certainty yet--will determine just how long lasting and high end this heat wave is.

What we do know however is this: significant heat and humidity are coming. 

Above: An Extreme Heat Watch has been issued by the NWS, as they have increasing confidence of a period of very high heat indices in the coming week, especially Wednesday through Friday. 

We know a heat wave is coming--officially that's three consecutive days or more of 90 degree or greater air temperatures. However, there's more to heat than the air temperature in our region. Humidity is a huge factor on how much strain gets put on our bodies.

What makes this different from other normal summer heat waves is that this looks like a "Big Heat" heat wave. I define Big Heat as air temperatures 95 or above and/or heat indices 100 or above. 

We get Big Heat days just about every summer. They're rough but manageable. When they're strung together, that's when we really start talking about major impacts because it usually means there's no opportunity to cool off at night. 

They don't happen often but they do happen, as you can see below. 

Big Heat air temperatures for consecutive days are more rare, especially after you get past three days. 

That would be brutal. One other thing to keep in mind here: localized humidity may very well be higher than what we see at official reporting stations. All of the local vegetation adds moisture to the air. It could be the case that while the heat index at BDL is 101 for example, it's significantly higher at home. 

With high heat and humidity and the pattern suggesting that we could see fast moving shortwaves (or triggers) moving though the atmosphere, strong to severe thunderstorms in the afternoon and evening will be possible. We will need to be at close range to properly weigh the daily risk. This might be the highest chance of storms until July 4th. 

Thursday-Friday
This is probably the worst of the heat, but it could extend into the holiday. While the NWS currently calls for part of the state to reach 100 degrees both days, we really want you to focus on the humidity, which may make for truly extreme heat indices.

For the northern CT River Valley, this may be dangerous heat. Even if air temperatures don't reach 100, the humidity will be high end. We could see heat indices officially top 110, which is rarefied air in Connecticut. Once again, there will probably be a chance of isolated to scattered strong to severe storms and I have no reservations saying that some local weather stations could see heat indices easily push above 110. ​

Above: A look at the historical record for heat index at BDL and BDR. Official heat indices topping 110 degrees are quite rare at BDL and exceedingly rare at BDR. 

July 4 & July 5 (my birthday!)
It is an open question as to whether the heat relents enough on Independence Day to end the Big Heat wave. For central CT, I think we're still in the mid to upper 90s with heat indices well into the 100s, but it's looking like we could see a greater chance of showers and thunderstorms (again, some of which may be strong to severe) that could keep temperatures from reaching their potential. Temperatures likely remain in the 90s with high humidity statewide. I think fireworks displays look fine for now, but this is something we'll need to keep watching at this range.

As for Sunday, we may see the first break in the heat then, but that all depends on the extent and intensity of the ridge. This does strike me as the kind of heat wave that ends with a bang, but whether that happens on Sunday or beyond is TBD. 

Overall, it's about the get hot. No, you won't spontaneously combust when you walk outside, and no, it's not the end of days, but this is a heat wave to take seriously. 

The Dailies
Monday: Partly to mostly sunny with seasonably warm conditions. Highs in the mid to upper 80s. Chance of showers/thunderstorms 10%. 

Tuesday: Partly to mostly sunny with seasonably warm conditions. Highs in the mid to upper 80s. Chance of showers/thunderstorms 10%. 

Wednesday: Hazy, hot, and humid. Highs in the mid to upper 90s with heat indices between 100-110. Chance of storms 40%. 

Thursday: Hazy, hot, and humid. Highs in the upper 90s to around 100 with heat indices between 105-110 officially, higher on home stations. Chance of storms 20%.   

Friday: Hazy, hot, and humid. Highs in the upper 90s to around 100 with heat indices between 105-110 officially, higher on home stations. Chance of storms 20%. 

Independence Day: Hazy, hot, and humid. Highs in the mid to upper 90s with heat indices between 100-110. Chance of storms 40%. 

Sunday: Hazy, hot, and humid. Highs in the low to mid 90s and heat indices around 100. Chance of storms 40%. 

​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​

Good evening from Southern Connecticut Weather! 

Some love them.

Some hate them.

For some, they invoke good memories and a sense of nostalgia, a reminder of the change in season. For others, the memories were scarring, invoking fear and dread. Thunderstorms are a seasonal rite of passage in our part of the world where we have four distinct seasons. 

Two severe weather days earlier this week, which produced wind damage in western and SW CT towns, heralded the arrival of summer weather. What leads to thunderstorm development in Connecticut? How often does severe weather actually happen? Why do some storms seem to fizzle when they get to my backyard?

Let's take a look. 

Above: A 2023 photo from southeast CT--taken by one of my dear friends. Note how lightning is striking in a storm on the left, but there's clear skies just to the right! This is a great reminder that it doesn't necessarily need to be raining where you are to be very close to lightning. When thunder roars, head indoors! 

What Makes A Thunderstorm
Thunderstorms are a critical element in nature's effort to bring balance to the atmosphere. If you notice, we almost never see thunderstorms occur on dry 70 degree and sunny days. Thunderstorms tend to be a summer phenomenon in Connecticut, during the season where we have the ingredients in the atmosphere for their development.

For a thunderstorm (convection) to develop you generally need four elements in play: Shear, Lift, Instability, and Moisture (SLIM for short). In Connecticut, some of these are easier to get than others, and timing and location in Connecticut matters a lot. You don't need me to tell you that NW CT most often sees strong to severe storms while it is less common in far SE CT. 

Above: A National Weather Service image of the ingredients necessary for thunderstorm development. 

The amount of these ingredients vary based on location. This is why thunderstorms don't just blow up over every part of the state at the same time. Usually, you need to reach a critical mass and a trigger (Lift) to initiate storms. When you have high enough amounts of each, you can end up with severe thunderstorms. 

Severe thunderstorms are defined as a storm with 58 mph or greater wind gusts, one inch (quarter size) hail or greater, or a tornado. Of course, we have all kinds of "non-severe" hazards with thunderstorms, including flash flooding and lightning. 

Let's look at each ingredient a little closer. 

Shear
Shear is the change in wind speed (speed shear) and/or direction (directional shear) with height in the atmosphere. 

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. 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 some level of wind shifting aloft for severe weather. 

The highest shear days come with synoptic (large scale) systems that include areas of low pressure, deep troughs, and tropical systems. 

Above: a diagram of a thunderstorm. Note how warm air in advance of the storm gets "sucked" in while the cool downdraft leads to the precipitation that brings us our weather. With shear, the structure is allowed to grow and the thunderstorm intensifies. 

Lift 
Lift is a critical ingredient for thunderstorm development. Even if you have an oppressively hot and humid day, that's usually not enough for a thunderstorm. If you don't have some lift, which comes in the way of a forcing mechanism, not much is going to happen.

Lift provides the atmosphere what it needs to rise and form convection. It happens a number of ways around the country, but in this region, if we're looking at statewide convection we’re usually looking one major mechanism: a front. ​

Above: an image showing the four major types of lift. Lift happens year round, but in the summer the type of lift helps determine how far along storms will get. 

Convective lift happens on days where you may see the pop up shower or thunderstorm. This is when the sun heats the area so much the surface heating creates its own lift. For severe thunderstorm purposes here it's the weakest kind of lift and doesn't usually create severe storms or even strong thunderstorms in CT. 

Orographic lift is something that actually helps in NW CT due to geography. The mountains may not be high, but the rising air from the Hudson River Valley into the Berkshires/NW Hills can lead to organized thunderstorm development. Once that lift is lost as storms move east, they can collapse absent another potent forcing mechanism. 

Convergent lift is when low pressure moves into the region and the convergence of air near the low results in lift. As mentioned above, this can coincide pretty well with out high shear days. 

Finally, we have our most common mechanism for widespread thunderstorm initiation--frontal lift. They don't just come from the north as a cold front passes, though that's probably most common. Along the coast if there is a strong enough sea breeze it can bring a frontal boundary inland that can become a focal point for thunderstorms. These boundaries don't go too far inland, but can lead to storms in southern CT. Fronts are the boundary between two air masses of different temperatures and air densities. When the cold front (or sea breeze 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. 

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 precipitation that make up a thunderstorm. High instability also contributes to prolific lightning events.

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. Having 5,000 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). Each tell us something a little different about the kind of thunderstorms we may see. 

Moisture
The last ingredient, moisture, is often the first ingredient we look to for thunderstorm potential. 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, there's no precipitation. 

We often have ample moisture available. On days with a southerly breeze, we are getting moisture directly from the Atlantic Ocean. With more humidity in the last 30 years, we've had even more moisture to wring out of the atmosphere on thunderstorm days. if you want to know what kind of moisture we’re dealing with during this time of year, look at the dew point—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 dew point, the more moisture in the air. Generally, you need dew points 60 and above for thunderstorms. Storms generally don't happen in the winter and spring (among other reasons) because the air is too dry. 

Why Do Storms Fizzle In My Backyard?
As I mentioned above, the ingredients for thunderstorms are not equal across the state at the same time. That's why often times it's harder for central and especially eastern CT have trouble getting big thunderstorms. Yesterday is a great example of this. 

Here's the radar image of the storms moving through the state yesterday. The got further because there was more lift, but lift was strongest in western CT. Second, note the time. In NW CT, when you were coming off the peak heating of the day, there's more energy to work with at 6:30pm compared to eastern CT around 8pm and later.

Then there's a subtle feature around Waterbury. The severe storm produced an outflow boundary. Basically downward flowing air forced out cooler and drier air ahead of what were potent storms, leading to more stability in the atmosphere ahead of the storms and the storm collapsing. 

Timing matters quite a bit. The earlier mid-afternoon storms tend to take advantage of greater instability. That tends to allow storms to get further in the state. But the southerly wind ahead of these fronts often pull in more stable air, making it harder for storms to sustain themselves as the propagate east. 

Above: The life cycle of a thunderstorm. Storms are usually, not not always, maturing in western and central CT, and dissipating in coastal and eastern Connecticut. 

Thunderstorm Climatology
Finally, it's no surprise that our severe weather really takes place in the summer. While May tends to be the kickoff of our convective season, by far the most severe weather takes place in Meteorological Summer--June, July, and August. The worst tends to be centered in July, when we have our warmest and most humid period of the summer. By August we're on the decline and not how quickly September falls off! 

This year, when we have the expectation of more troughs hanging around and frontal boundaries moving through the region, it looks like it may be an active year for storms. 

Severe Thunderstorm and Tornado Watches are issued by the Storm Prediction Center (SPC) in Norman, OK. Severe Thunderstorm and Tornado Warnings are issued by the local forecast office of the National Weather Service. In Litchfield County, that means NWS Albany issues your warnings. In Hartford, Tolland, and Windham County that means NWS Boston is issuing your warnings. In our southern four counties, your warnings are issued by NWS NYC. 

In advance of storm days, the SPC issues outlooks for the country. Here are the categories they use. For Connecticut, a slight risk tends to be the highest category we reach, though each season an enhanced can happen once or twice. A moderate risk is exceedingly rare in CT.