The potential and concern is increasing as computer guidance begins to hone in on the forecast for Tropical Storm Henri, which is currently sitting off the southeast coast of the US. In this update, we will provide a brief overview of where things stand and go into detail in the three scenarios we think are most likely for Henri as it moves toward New England. We expect tropical storm or hurricane watches to be issued for parts of New England, especially eastern New England, as early as tomorrow morning.
We are still too far out to get into specific details, but let this be the takeaway tonight: Henri, whether it is a tropical storm or hurricane, poses a serious threat to New England. This will not be a locked in forecast until much later, and now is the time to prepare.
Tropical Storm Henri is currently moving westward under the first upper level ridge that we discussed last night. The ridge has also been creating shear, which has been keeping the strength of Henri in check. That shear will decrease however over the next 12-24 hours, and that will set the stage for strengthening.
As that happens, a trough over the US will cut off and influence Henri. That will turn it north and effectively slingshot it toward New England. As discussed last night, as that happens another ridge will build over Canada, closing off the final escape route and all but guaranteeing that there's at the very least an extremely close approach by Henri.
We have high confidence that a turn north will bring Henri extremely close to New England. Now the devil is in the details. We have identified the three most likely scenarios for Connecticut as Henri gets to New England. The illustrations provided are only intended to show what the scenario would look like. Again, DO NOT LOCK IT IN.
Scenario #1--Near Miss/Glancing Blow
In this scenario, Henri comes north but rather than being pulled closer to CT, it passes just offshore of Cape Cod and continues a northeast heading away from the region.
This would spare most of CT from significant rain or wind on Sunday and Monday, but it would still bring coastal impacts. Along the shore in this scenario you could probably expect minor to moderate coastal flooding, rip currents, and relatively significant wave heights, especially in SE CT. For most, this would be a minor event at best with a little rain and maybe some breezes.
The illustration here comes from the midday 12z GFS run.
In this scenario, Henri continues a northward heading right into an area between Charlestown, RI and Martha's Vineyard. It also slows down significantly upon landfall, but keeps moving away from the region.
This would bring much more wind and rain to the state Sunday afternoon into Monday. It'd likely bring tropical storm conditions to central and eastern CT, heavy rain throughout the state with the heaviest in central and eastern CT, and coastal flooding impacts along the CT shoreline. This would be a meaningful hit, with flash flooding, coastal flooding, and substantial power outages.
For this illustration, we use the latest 18z GFS model run. Note that a shift west would bring even more wind and rain into CT and that looks possible given the totality of the guidance you don't see here.
This scenario, while not currently most likely, is something that is increasingly viable and why we are hitting preparation so hard. In this scenario, Henri makes landfall between New Haven and Westerly, RI. A track this far west means that Henri has maximized its intensity potential. Not good at all. Even worse, it'd be hitting and likely stalling over the state or just south of it Sunday into Monday.
I cannot emphasize enough how bad this would be, and it would be almost irrelevant if Henri is a strong tropical storm or category one hurricane. This would likely be high impact at least, and I am intentional in my wording here.
In this scenario we'd see long duration tropical storm to hurricane conditions, very heavy rain that could produce major river and flash flooding, and major coastal flooding depending on the heading (direction) and location of the storm. Widespread power outages would be likely, along with extensive tree damage.
For those that follow us, you know we don't like hyperbole. We say what we see and it is backed up by facts. This would really be a worst case scenario for Connecticut. You need to be prepared in case this comes to pass.
Rather than illustrate here, (if you want to see the model run I considered, look up the 12z Ukmet model), I am going to post the hot off the presses European Ensembles, which show another shift west that puts this potential scenario into greater play. Again, as I have posted already, DO NOT LOCK THIS IN. Image courtesy of weathermodels.com.
1) Additional changes to both the track and intensity forecast remain likely. We now know that an extremely close approach is highly likely. The final outcome is highly dependent on small changes in the steering pattern and intensity. Odds have increased for at least a moderate impact event. The forecast is coming into greater focus. DO NOT lock into specific computer model runs.
2) NOW is the time to prepare. Even in the worst case scenario, choose preparation over panic. Check your generators, supplies, and plans. Now is the time to act.
3) Timing for impacts currently look to be Sunday afternoon and Monday. This remains the same as yesterday, but conditions could begin to deteriorate under Scenario #2 and 3 as early as Sunday morning.
SCW will be providing updates as we receive additional information. As we track this system, please understand that we will be much slower to respond than usual.
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Thank you for reading.