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.
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.
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.
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.
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.
There are three ways this heat wave may unfold.
The first is that the ridge is weaker and/or less expansive than the models currently forecast, which is possible as the Euro has a known heat bias and the GFS tends to overmix the atmosphere, leading to its own heat bias. Even in this scenario Wednesday through probably Sunday are in the 90s, but the heat and humidity are more standard summer heat rather than higher end. This seems least likely.
The second is that like many of our modeled heat waves, it ends up less hot in terms of air temperature and more humid. This would be more likely if the ridge ends up a bit further south, bringing us more southwest flow on the edge of the ridge. This is more impactful than option one, but probably comes with a shorter heat wave. That said, days of oppressive humidity would make outdoor activities on and around Independence Day very difficult.
The third option is that the ridge ends up further east and parks over us. That would bring a long duration and high end heat wave with temperatures pushing 100 but maybe a touch less humidity as a result. Even so, heat indices would be extremely high. This is probably the most impactful but is also an unlikely outcome.
Not really any great options there.
The Week Ahead
Monday-Tuesday
We will end June on a warming trend, as the low to mid 80s we've seen in recent days will be replaced with mid to upper 80s tomorrow and Tuesday with ever creeping humidity. Conditions look nice and dry however, other than the low risk of a pop up shower or thunderstorm. There's a chance a hot spot reaches 90 degrees but this is standard summer weather that I hope folks enjoy before we get truly hot.
Wednesday
The first day of July should be the start of the heat wave for most, even down to the shoreline. While there has been a lot of talk out there about extreme and dangerous heat, let's be clear--heat can be dangerous to people at any time if they do not take proper precautions. Folks that work outside already know this--stay hydrated, take plenty of breaks, and don't overdo it. Heat kills more than all other weather events in general. It's sneaky, so you don't need the highest echelon heat to cause problems.
Wednesday will have a nasty combination of heat and humidity and will lead to our first Big Heat day at least for inland CT with temperatures in the low to mid 90s but oppressive humidity pushing heat indices over 100 for most. As the first image showed, the NWS had much of CT under extreme heat risk. This is likely if we have temperatures overachieve and reach the upper 90s while dew points get close to the mid 70s as the Euro predicts below.
The first is that the ridge is weaker and/or less expansive than the models currently forecast, which is possible as the Euro has a known heat bias and the GFS tends to overmix the atmosphere, leading to its own heat bias. Even in this scenario Wednesday through probably Sunday are in the 90s, but the heat and humidity are more standard summer heat rather than higher end. This seems least likely.
The second is that like many of our modeled heat waves, it ends up less hot in terms of air temperature and more humid. This would be more likely if the ridge ends up a bit further south, bringing us more southwest flow on the edge of the ridge. This is more impactful than option one, but probably comes with a shorter heat wave. That said, days of oppressive humidity would make outdoor activities on and around Independence Day very difficult.
The third option is that the ridge ends up further east and parks over us. That would bring a long duration and high end heat wave with temperatures pushing 100 but maybe a touch less humidity as a result. Even so, heat indices would be extremely high. This is probably the most impactful but is also an unlikely outcome.
Not really any great options there.
The Week Ahead
Monday-Tuesday
We will end June on a warming trend, as the low to mid 80s we've seen in recent days will be replaced with mid to upper 80s tomorrow and Tuesday with ever creeping humidity. Conditions look nice and dry however, other than the low risk of a pop up shower or thunderstorm. There's a chance a hot spot reaches 90 degrees but this is standard summer weather that I hope folks enjoy before we get truly hot.
Wednesday
The first day of July should be the start of the heat wave for most, even down to the shoreline. While there has been a lot of talk out there about extreme and dangerous heat, let's be clear--heat can be dangerous to people at any time if they do not take proper precautions. Folks that work outside already know this--stay hydrated, take plenty of breaks, and don't overdo it. Heat kills more than all other weather events in general. It's sneaky, so you don't need the highest echelon heat to cause problems.
Wednesday will have a nasty combination of heat and humidity and will lead to our first Big Heat day at least for inland CT with temperatures in the low to mid 90s but oppressive humidity pushing heat indices over 100 for most. As the first image showed, the NWS had much of CT under extreme heat risk. This is likely if we have temperatures overachieve and reach the upper 90s while dew points get close to the mid 70s as the Euro predicts below.
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.
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.
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%.
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Thank you for reading SCW.
-DB
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%.
As always, please like, share, and interact with us on our social media--on Facebook to share our discussions, and follow us on Twitter @southernctwx to retweet our posts. Hit the buttons below to join.
Thank you for reading SCW.
-DB
