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Grading our Forecast of Tropical Storm Henri...

8/27/2021

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Good morning from Southern Connecticut Weather. 

Now that things are a little less hectic, it is time for us to review our final call forecast of Tropical Storm Henri. Henri was a hurricane but weakened to a tropical storm before landfall with estimated maximum sustained winds of 60 mph.

While the subjective impact in Connecticut was less than expected, we deal in data. How well did we actually do?

​Let's take a look. 
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Above: the track of Henri, which briefly became a hurricane in the day before final landfall, using "best track" data. The final official track will be issued by the National Hurricane Center (NHC) in a final tropical cyclone report. 

Timing
We expected the first rain to reach the coast between 3-5am and that was spot on. It was a close call as we saw a quasi-PRE just south of the state that brought extremely heavy rain to the NYC and NJ area. We expected tropical storm conditions to begin along the coast by 8am and that was a bit late--though wind was never really high end in this storm. The progression of the storm was accurate, but at the time of the forecast we were unsure about Monday. Overall, a good forecast. 

Grade: B+

Landfall Location & Intensity
Despite all of the guidance seemingly shifting east at the last minute, we were unmoved in keeping the landfall zone between New Haven and Westerly, RI. In the end, that was a great call, with Henri making landfall right at the eastern edge of our zone, as we stated in our final call. 

That said, intensity was a miss. To be clear, it's not like it was a big miss, as we anticipated a 70 mph landfall and got 60 mph, but we should have accounted for additional weakening causing a general lack of wind across more of CT. While the wind did occur in parts of CT, it was not nearly as strong or widespread.

Averaging out the A for the landfall location and C for intensity, we end up with a B for this category. 

Grade: B
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Wind
The less intense winds were good for the state, but bad for the forecast. Here's what we forecasted:

"We think that the eastward shift in track has reduced the wind potential slightly, but it won't really make much difference in the scheme of things. We expect the following during the worst part of the storm: 


  • Coastal areas: Sustained winds of 40-55 mph with gusts between 60-70 mph. Some isolated areas in SE CT may see higher gusts. Winds will be stronger the closer you are to the center, meaning the stronger winds will likely be east of New Haven and strongest in New London County. 

  • Inland areas: Sustained winds of 30-40 mph with gusts between 45-55 mph. Isolated higher gusts are possible near the center of the system."   

According to the Public Information Statement issued by the NWS on August 22, BDL recorded a gust to 44 mph, HFD recorded a gust to 43 mph, and Willimantic recorded a gust to 40 mph. That was short of our forecast range, but not terribly off. Note that these areas were closest to the center at one point. 

Along the coast, it was ugly. According to the Public Information Statement issued by the NYC NWS on August 22, Middletown recorded a gust of 47 mph, Groton got to 53 mph, but everything was 40 mph or lower. That's a terrible bust on our part. 

While we did specifically state that weakening would be taking place at landfall, and that being closer to the storm would increase the threat of damaging winds--exactly what happened in eastern and SE CT--that doesn't really help the grade.

Grade: D

Coastal Hazards
Data on the amount of surge and coastal erosion is hard to come by, but overall it looked like the coastal hazards were not as high impact as anticipated. That's likely due to the weakening that took place and more importantly, the intensification that never reached high end levels in the hours before landfall, which would have pushed more water into the Sound.

​That said, coastal hazards from landfalling tropical systems are one of the biggest threats we have in CT, and we would not have changed the forecast even with the benefit of hindsight. 

Grade: C

Severe Weather
Not much to be said here. This was an accurate forecast. The potential was isolated to eastern CT and while we did not see tornadoes, we saw three confirmed just to the NE of CT.  


Grade: A-

Rainfall
We warned followers that this would be a long duration rain event, and it was, lasting Sunday and Monday. We were a little too aggressive with our western zone rain forecast, but overall the 2-5 inch rain zone in eastern CT worked perfectly and the 5-10 inch zone worked in central CT, albeit on the lower end.

There was major flash flooding in spots, with major highways like I-91 and Rt. 2 closed for a period due to flooding. In my town of East Hartford, the Hockanum River saw a top 5 (preliminary) flooding event. Even so, we dodged a bullet for the widespread kind of flooding we thought was possible. 

Grade: A-

Observed storm total rainfall image courtesy of the National Weather Service (Boston). 
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Power Outages
We said power outages would be high to extreme impact and they weren't. Once again good for the state and terrible for the forecast. Winds did not verify, especially in coastal sections of CT, and that kept outages below even 50,000. Big bust. Lowest grade of the forecast. 

Grade: F


Overall Impact
We thought this would be a high impact event statewide and that wasn't the case. It was not on par with the big events we've seen recently, though we did have significant flooding take place in multiple parts of the state which helps the grade.

Although it was good that the impact was much lower overall, it only raises the chance that people are complacent in advance of the next big storm. I continue to believe that a bona fide hurricane making landfall in Connecticut would be catastrophic in Connecticut given our infrastructure and tree density.

It has been 30 years since Hurricane Bob made landfall to our east and 36 years since our last direct hurricane strike, Gloria. Our last major hurricane strike was the Great Hurricane of 1938, or the Long Island Express. Statistically, we are overdue for a hurricane strike and long overdue for a major hurricane impact. 

Grade: C-

Final Grade
Let's recap the grades that make up our final grade. Each are weighed equally. 

Timing: B+
Landfall Location & Intensity: B
Wind: D
Coastal Hazards: C
Severe Weather: A-
Rainfall: A-
Power Outages: F
Overall Impact: C-


This leads to our final grade, a decent but disappointing C+.


For this forecaster, who has closely studied and tracked tropical weather for more than 20 years, it is extremely disappointing personally to miss on the forecast, especially the wind and power outage aspects of the storm.

That said, I know that tropical meteorology is one of the hardest forecasting areas in the entire field, and a landfall on the other end of our zone, New Haven, would have produced vastly different results even at a landfall of 60 mph. These forecasts are always close, and that's why we work so hard to provide you with the latest information and hype-free analysis that is always backed up by data. 

We will continue providing the highest quality service we can, no matter how much nature complies. Grading ourselves after major events to hold ourselves accountable and learn from our mistakes is one way we do that. 
​
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
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