Good evening from Southern Connecticut Weather. 

You know us. We do not hoist the high end warning flags unless necessary. Despite a higher degree of uncertainty than we'd like, we're hoisting.

Our level of concern is increasing as we've watched a complex evolution between a coastal low, inverted trough, and anomalously high precipitable water and easterly fetch combine tomorrow to bring a widespread significant rain event, and potentially major rainfall event in some part of the region. 

Adding to the concern is the very high rainfall we've seen this summer and September, which has caused a lot of basement flooding issues and higher water tables. 

It goes without saying that tomorrow and Saturday are now a SCW Period of Interest. 

Above: the latest Weather Prediction Center (WPC) excessive rainfall outlook for tomorrow. While a moderate risk of excessive rainfall is different than having a moderate risk of severe thunderstorms, the synoptic setup tomorrow into Saturday suggests that a lot more rain is coming to Connecticut. Image courtesy of Pivotal Weather. 

Overall Setup
You may be wondering "where did this come from?" but we have been talking about the potential for Friday rain the last few days. We were intentionally silent on the setup because of the uncertainty but now inside 24 hours there is greater certainty in heavy rain. 

A coastal low develops well offshore, but because of the upper flow extends an inverted trough over some part of the region. If you're wondering why you're hearing about an inverted trough in fall and not winter, you are onto something. Usually we only talk about inverted troughs (IVTs) during winter storms, but this time we have a setup that is ripe for a heavy rain event. 

IVTs are notoriously difficult to predict. This time is no different. 

What we think is that as the coastal low develops tomorrow, the IVT sets up over eastern NJ, NYC, the lower Hudson Valley, and some part of western CT. SW CT in particular back to New Haven is a particular risk zone that the WPC has highlighted, but it should be noted that anywhere from around Hartford and points west could see heavy rain. 

The inverted trough will be enhanced by anomalously high moisture aloft, a persistent easterly flow pushing moisture into the trough, and a slow moving coastal low. That's tomorrow. The low is slow to depart, which puts Saturday at risk. Rain would be gone by early Sunday, but like last weekend, we have to watch for a lower probability delayed but not denied event with the track of the low. 

Let's look at the global camp and high resolution camp. 

Globals (Euro/GFS)
As the low meanders to our south, Saturday could bring moderate to heavy rain to eastern areas, as depicted in the 12z Euro depiction below along with its projected rainfall total. Rather than the intense high end rainfall totals of the high resolution models, the global models have a more widespread and spread out (over time) rain event. It's 2-4 inches of rain which would cause some issues, but nothing like what the high resolution guidance attempts to do. 

It should be noted that just a few inches would make September more wet than our outrageously wet July in a number of places. A 4" rainfall equates roughly to a month's worth of rain in September. 

Here's the GFS, which has been slow to make this a widespread rain event but the latest model run is now on board. It is disfavored for now given how much correcting it has had to do. Note that even on the GFS, heavy rain happens in western CT, even though it's later Friday into early Saturday. Unlike the Euro, there is less rain east on Saturday, but it could still be a blah kind of day verbatim. 

Images courtesy of Tropical Tidbits and Weathermodels.com. 

The globals having a widespread rainfall Friday and Saturday gives us confidence in a floor of a significant rain event. Discounting the GFS, I think the general overall rain totals in the state Friday-Saturday will be 2-4" with higher totals the further west you are. 

It'd be great if it remained that cut and dry, for lack of a better term, but it's not. Let's look at the high resolution guidance and why this could be a major rainfall event somewhere in CT. 

High Resolution Guidance (HREF/NAM/HRRR)
Let's start with a recap of the rainfall this month. Thanks to a series of coastal storms, including the remnants of Tropical Storm Ophelia, much of Connecticut has seen 1.5x to double normal rainfall this month alone, and this could be the biggest rainfall event of the month for some. 

The high resolution guidance has gone big with a narrow area of extremely high rainfall totals tomorrow. Synoptically, a narrow area where a "firehose" of moisture makes sense. You can see it in the global models and certainly in the high resolution guidance. The questions really are 1) where does this firehose set up and 2) how high end can it be. 

I think some of these are overdone, hence the general 2-4" rainfall forecast. However, there is likely to be an area, most likely in western and SW CT, where even more rainfall occurs.

In consulting with GP and SA, we don't think that area is going to be very wide, but anyone from Hartford (in case the IVT is further east) to western CT needs to be weather aware tomorrow. This is something where we need to watch radar trends to see exactly how thing set up. 

Here's the latest HRRR. Rather than post the (likely) overdone high res totals of the HRRR, it's just worth saying that it's not out of the question to see 6+ inches of rain in the areas where the heavy rain trains. If that were to occur, expect flash flooding as early as tomorrow morning.

Once again, stay weather aware as this forecast evolves. Do not drive through flooded roads. 

The HREF mean is concerning as this is an ensemble of high resolution guidance. Do not take this verbatim, as any shift east could put more of CT in the more high end rainfall zone and a shift west could take much of CT out of it. 

Overall

• Flood watches have been issued for Fairfield, New Haven, and Litchfield counties. It is possible those get expanded further east. 
• A significant rainfall event is likely Friday and Saturday, with general rainfall amounts of 2-4". Higher rainfall totals are more likely in western CT, and flash flooding will be possible. 
• A major rainfall event is possible tomorrow, particularly in western and SW CT as an inverted trough becomes a focal point for heavy rainfall. In this area, some spots could see rainfall totals in excess of 6", with flash flooding likely. Central CT should watch out in case the inverted trough sets up further east. 
• Saturday is more uncertain, but some rainfall seems likely, making at least the early part of the day messy. 
• Rain should clear by early Sunday, and Sunday looks like a decent day. 

Given the rainfall this month, the synoptic setup for a firehose of moisture somewhere between NJ, NYC, and western CT, this event requires close attention by everyone. 

Stay tuned as frequent updates will likely be required tomorrow. Take this one seriously. 

​-DB/GP/SA

Good evening from Southern Connecticut Weather.

Our beautiful work week is going to turn into a wet, raw, and breezy weekend as a tropical disturbance off the southeast coast is poised to develop and move northward. Let's dive in. 

Above: the latest National Hurricane Center (NHC) track for Potential Tropical Cyclone Sixteen. 

Overall Setup
This setup is pretty straightforward. We commonly see subtropical or tropical systems develop this time of year off of decaying boundaries off the southeast coast, and that's what's happening here. A broad area of low pressure is currently non-tropical off the southeast coast, and is expected to consolidate some and intensify.

Frequently, we see these systems go harmlessly eastward and out to sea, but this time, we have an Atlantic ridge that will strengthen and steer this low northward to north-northwestward. As that happens, a strong high pressure will develop to our north, blocking it from going out to sea until it gets close to our latitude and a weakness between the two ridges develops.

The general track guidance is now a high confidence forecast, and the GFS depiction below shows this steering pattern well. 

CT Forecast
Tomorrow looks like another great day. The low pressure is likely to become a tropical storm as it heads north into North Carolina. The next name on the list is Ophelia. 

Future Ophelia is likely to take a track that allows for tropical moisture to push into CT on Saturday. Unfortunately, even the morning hours are now looking wet, as moisture from the storm pushes into the state from south to north around 7am. One thing to watch is the push of heavy rain. The guidance for the most part has kept the heaviest rain offshore on Saturday, which reduces flooding risk. However, we need to see if this changes over the next few days as a boundary could set itself up somewhere south of CT allowing for more efficient (read: heavier) rainfall. 

Here's the GFS depiction of that push of moisture on Saturday. It looks like a rainy, raw, and windy day, far more than what we saw with Lee. There may be some minor coastal flooding with a persistent onshore flow, and that's something we'll be watching.

Winds could be on the order of 25-35mph, maybe a little higher at the immediate shoreline, as a gradient between the strong low to the south and high pressure to the north clash. 

Again, above you see the area of intense rain stay offshore as future Ophelia makes landfall in NC and moves into the Mid-Atlantic. 

That's not the end of the rain, however. While there may be a break late Saturday into early Sunday, the remnants of Ophelia will turn northeast, putting the remnant low below CT most likely. As this happens, the rain may be enhanced near the center, meaning that Sunday may be even worse than Saturday even as the wind diminishes. The timing is still uncertain, but heavy rain is possible Sunday into early Monday. 

Once again, the GFS (and other guidance) depicts something similar. 

As a result, the weekend looks terrible. The potential for heavier rainfall Sunday raises the risk of flooding, but for now, there's more uncertainty on where Sunday's heavy rain axis sets up. 

Overall Impact
What is likely to become Ophelia is likely to bring a washout weekend. I do not anticipate significant power outages or coastal flooding issues. It won't rain heavy all the time, but between Saturday morning and early Monday morning we could see 1-3+ inches of rain. Considering that most of the state has already seen well above normal precipitation for the month of September, and the summer overall, we have to watch for flooding if the wetter solutions play out. As a reminder, the entire month of September usually sees around 4" of rain. 

This is likely to play out like another very wet nor'easter. 

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 and trusting SCW. 
​
-DB​ 

Good evening from Southern Connecticut Weather. 

Hurricane Lee is one of the classic "long track" storms we haven't seen in quite some time. As a result, there has been an abundance of time for the hype machine on social media to rev up. 

Let's take a fact-based look at Hurricane Lee, the potential scenarios, and possible impact on CT this coming weekend. 

Above: the current National Hurricane Center (NHC) forecast track. The NHC track only goes out five days, and as you can see, the projected center line is not forecast to be over NYC, Boston, or any part of CT at 2pm on Saturday. This is consistent with the overwhelming majority of track guidance. 

Where is Lee Now and What is the Short Term Forecast?
Hurricane Lee is currently a major hurricane well north of Puerto Rico, moving west-northwest at a slow 7 mph. Lee is expected to slow down even more, as it rounds the periphery of a ridge of high pressure over the Atlantic. It is rounding the ridge because a trough is causing a weakness that will allow for Lee to turn northward by late Wednesday or early Thursday. 

Above: 18z GFS operational run out through hour 78, courtesy of Tropical Tidbits. Lee turns northwest and then northward in the next few days, west of Bermuda. This is a high confidence forecast, and I am using the operational of the GFS here because 1) it has a nearly identical depiction to other guidance and 2) it is a short term forecast. 

​Guidance begins to split in agreement after roughly passing the latitude of Bermuda. 

A hurricane turning north this far east would almost always get swept out to sea by the trough (blue shading and lowering heights) over the eastern US. Normally, for a direct CT or southern New England landfall threat, a hurricane reaches the Bahamas before turning north.

However, in this instance the guidance also agrees that the original trough above moves out before sweeping Lee harmlessly out to sea. That allows for the Atlantic ridge to build back in to the north of Lee, effectively blocking that out to sea path. 

As that happens, a second trough sweeps in from the eastern US, which forces Lee to take an extended northward, or critical to New England, possible north-northwest heading before eventually getting shunted east. Below are the 12z EPS and GEFS (ensemble) runs. These images are courtesy of Weathernerds.com. 

Remember that ensembles are individual runs that have environmental conditions tweaked and then aggregated to give a sense of model forecast spread. The top image is the GEFS run. The animation below it is the EPS, European ensembles. 

Two things stand out.

First, the ensembles do not follow the operational runs you may have seen that bring Lee closer to eastern New England.

Second, the ensembles do not show a significant risk of a direct hit on CT from Lee.

It's important to remember that the center of a storm is not the only place where impacts happen. Lee is expected to expand quite dramatically and bring wind and rain well away from its center. However, an offshore track would significantly minimize the rain and wind hazards for CT. 

What's Going to Happen From Here?
That's still unclear. We're only now reaching the point where we can start to narrow the goal posts. There is high confidence in a turn north, and high confidence in an extended northward heading. There is also high confidence that this will not be a major hurricane once it reaches New England's latitude. Why? Sea surface temperatures are expected to drop off dramatically, and this will happen as shear increases, dry air is possibly entrained into the system, and it begins merging with the incoming trough to become extratropical.

​Lee will be larger, slower, and weaker, once it reaches New England's latitude. That doesn't mean weak storm, but it allows you to contextualize better. 

Above: the NHC track superimposed on the current sea surface temperature plot. Note how temperatures drop off rapidly once Lee gets north of the Gulf Stream in the Atlantic (north of where it says "Hour 96"). Image courtesy of Tomer Burg's phenomenal site. 

​It is still unclear whether we see a bend NNW toward New England, and a long enough motion on that heading to put CT at risk of significant impacts. 

In collaborating with GP this evening, he noted that he could only find two hurricanes that made landfall in Maine (the higher risk zone should this keep north): Hurricane Edna in 1954 and Hurricane Gerda in 1969. This shows how rare this kind of track actually is. That's still reflected in the super ensemble, a collection of all the major ensembles, also found on Tomer's site. 

Scenarios
With everything above, and my own analysis of the projected steering pattern, I divide up potential impacts in three scenarios.

• Atlantic Canada Landfall (most likely Nova Scotia)--60%
  • It is becoming increasingly likely that the second trough pulls Lee on an extended northward heading, and that Lee will not be able to fully escape, even if there is a last minute trend east which fits New England hurricane climatology. 
  • In this scenario, there are few impacts on CT. High surf and rip currents would be possible along with some minor coastal flooding, but there would likely be few if any rain showers or gusty winds--gusty enough to cause problems. 
    
    
• New England Landfall--30% (25% Eastern New England/5% Southern New England)
  • Eastern New England--Cape Cod and Maine, are far more favored for a landfall or center scrape because the ensembles have not meaningfully put southern New England at risk even as they have generally shifted west until recent runs today. 
  • In this scenario, there are significant impacts. Obviously the southern New England scenario would be high impact, but in dealing with the more likely--a scrape of the Cape--we probably see rain and strong winds, especially in eastern CT, in addition to possible coastal flooding on Saturday.
• Out to Sea--10%
  • Respect still should be given to a sharper than anticipated eastward shift, but this looks increasingly unlikely. 

Should I Worry?
At SCW, we preach Preparation over Panic. There is no reason to worry, and definitely no reason to panic, over the potential track of Lee. At this range, a lot can still change as we're narrowing the goal posts, because even 100 miles can make a difference in what our weather is. We won't know exact track for a few more days at least. 

At this point, there are a couple of small but important steps that you can take to prepare in case this ends up more impactful. I've posted before and this advice is evergreen. 

The Four Basics
1. Know Your Zone--given what I said above, it's unlikely this is a bad enough hit to require an evacuation, but know your evacuation zone in case you need to leave. In CT, that's most likely to be right at the coast, where flooding would occur. The majority of deaths caused by tropical systems are flood related--storm surge or inland flooding. You can find the evacuation maps here. 

2. Make A Plan--this seems self-explanatory, but what would you do if you lost power? Needed to evacuate? Needed to get supplies? Check in on a loved one? Having a plan now will save you time and worry later. 

3. Build An Emergency Kit--You don't need to make all your purchases at once, but if you wait until a day or two before a storm hits you will run into empty shelves for some items and potentially higher prices. This can be helpful even if there isn't a storm. 

4. Stay Informed--Get your information from trusted sources. Don't panic or dismiss a threat just because of one model run or model cycle. Stay level headed and use quality information to make an informed decision. 

Stay tuned as we continue to update this forecast in the coming days. 

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 and trusting SCW. 
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-DB​ ​

Good evening from Southern Connecticut Weather! 

The first day of September has been a spectacular one, with the morning staring in the 40s for many and highs in the 70s. A spectacular Labor Day Weekend is on tap with a taste of fall today and (to a lesser extent) tomorrow for fall lovers, and a return to warmth and heat Sunday and especially Monday for those hanging onto the last days of summer. 

Above: the precipitation departure for meteorological summer. The story of the summer in a nutshell: it was a wet one. This was made all the more impressive by no tropical systems or remnants impacting the region. 

Reviewing Meteorological Summer 2023
Meteorological summer runs from June 1-August 31, and it was wet with normal temperatures. Looking at the climate reports from the National Weather Service for the two official reporting stations for Hartford and Bridgeport:

Hartford

• Hartford finished with an average temperature 0.2 degrees above normal, so basically normal. Our average high temperatures this summer were nearly one degree below normal, while our low temperatures were just over a degree above normal. 
• It was very wet in Hartford, with 19.08" of rain, most of which fell in July and August. This is 6.42" above normal!
  
• Hartford had a below normal number of 90 degree days, and while July was warm due to humid conditions, August was below normal in temperature.  
• Hartford had 50 days with at least light rain. 

Bridgeport

• Bridgeport finished with an average temperature 1.0 degrees below normal and also had a well below normal season of 90 degree days. It only had 3 all summer. 
• Bridgeport, like much of southern CT saw less rain than northern CT. BDR recorded 13.13" of rain, still 2.06" above normal. 
• Bridgeport had 42 days with at least light rain. 

Now that we move into September, what are the climate normals?

September Normals
Hartford
September 1 Average High Temperature: 81
September 1 Average Low Temperature: 59

September 15 Average High Temperature: 76 
September 15 Average Low Temperature: 54

September 30 Average High Temperature: 70
September 30 Average Low Temperature: 48 

Average Monthly Rainfall: 4.39"

Bridgeport 
September 1 Average High Temperature: 80
September 1 Average Low Temperature: 64 

September 15 Average High Temperature: 76 
September 15 Average Low Temperature: 60

September 30 Average High Temperature: 70 
September 30 Average Low Temperature: 54

Average Monthly Rainfall: 3.96"

Labor Day Weekend
As I said earlier, spectacular weekend with something for everyone. A strong ridge is in place throughout the weekend, meaning dry conditions each day. For those that love fall, today was a treat with temperatures reminiscent of mid to late September. Saturday is a little warmer with highs in the low 80s, but it'll feel great with sunny conditions.   

We start to see the warmth pick up however on Sunday. I originally thought it'd hold off until Monday, but that won't be the case. It'll be great beach or cookout weather on Sunday, with highs in the mid to upper 80s and increasing humidity, though it won't be oppressive. 

Labor Day looks excellent as well, especially if you like summer. It'll be hot though, especially inland. Expect a little more humidity with highs in the upper 80s at the shore to low 90s inland. For inland areas, this'll likely be the start of a heat wave, and quite possibly summer's last stand. 

Tropical Update
Meanwhile, the tropics are on fire. As we reach the peak of the season we've already had two major hurricanes in the basin. The basin remains favorable for tropical activity, and I expect the first long track tropical system to develop in the next week from the orange area below. For now, there are no threats to Connecticut, but this is a time to stay vigilant. 

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 and trusting SCW. 
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-DB​