Hermine is currently over North Carolina bringing flooding rains. She is moving quickly to the north-northeast. Early in the frame you can clearly make out the core and where the "eye" was. In the last 2 frames it's clear the eye has become exposed and Hermine has weakened from a Hurricane to a Tropical Storm as she spins over land. She is expected to move back over water and regain strength as an extratropical storm.
TPC's track nicely shows how Hermine's resurgence over the Atlantic. She is likely to become a Hurricane again late Sunday or early Monday. Tropical Storm warnings and watches are in effect for the Tri-State area.
As Hermine tracks north, she is going to run into High Pressure which acts as a block. This block will force Hermine to retrograde back west toward the coast instead of meandering out to sea. This is a big blow for residents on the NJ shore and south shore of LI because a full moon is in the forecast this weekend. The strength of a category 1 Hurricane moving due west + overlapping tide cycles due to the slow movement will result in disastrous and horrific storm surge. These areas could be looking at a surge of 7 to 8 feet if latest model guidance comes to fruition.
Here is a look at 500mb height anomalies from the 12z EPS. This gives you a better look of the block to the north. The ridge prevents Hermine from escaping out to sea. As she departs North Carolina, she is expected to track NNE and get fairly far east before turning back west. This is the main reason why the storm surge forecast looks nightmarish for folks along the coast.
The teal line is the track I expect Hermine to take. It is not much different from the one I showed yesterday. I think the retrograde will occur east of the Delmarva before heading NNE, where she is likely to stall for 2 full days. How far west in her retrograde does she go is the main question left to be answered.
Check out these 925mb winds from the GFS and their time stamps. Sustained Tropical force winds over much of the area is possible for 2-3 days. The yellow shading translates to 35-50mph winds at the surface, while the red could mean gusts at Hurricane force for the immediate coast and 60-70mph for those just inland. The issue is these winds will remain with us for longer than 2 days since Hermine is expected to stall off the coast. The combination of high winds and rain could lead to prolonged power outages, especially since for safety reasons many powerline crews do not begin repairs until the winds die down.
Figuring out how much rain falls is the trickiest part of the forecast since we're uncertain with Hermine's exact track still. Look how close the purple, blue, and grey shadings are to the coast. A shift of just 50 miles west puts much of NJ in flooding rain. The NJ shore and east end of Long Island is a good bet to see at least 3 to 6 inches of rain. Add the 5-7 foot storm surge and near Hurricane force winds, the NJ shores are in line for a very dangerous storm and they should start making preparations NOW.
One thing that caught my attention is dry air tries to get entrenched into this storm by early Monday. That could hinder rainfall totals a bit, especially for those away from the coast. Something to watch...
Take note that I am forecasting winds for the brunt of the storm. There will be times on Tuesday and Wednesday where these winds will verify too (see graphic with time stamps). Overall, I expected Tropical Storm force winds for those in red over a 2-day period with Hurricane Force (74+ mph) very likely for a period of time Sunday night into Monday early afternoon. 850mb winds are shown to be over 75mph in some locations. Those in blue will see Tropical Storm force winds too, but probably not over 2 days worth. Again, this is a tricky forecast because if Hermine tracks closer to the coast then the Hurricane Force winds could extend further inland. It will not take much for that red to overspread much of the area. Regardless, TS force is still bad and could cause many issues.
I have low confidence with my rain forecast. I expect to have an update out tomorrow afternoon with updated maps. I am confident the NJ shore will see at least 3" of rain, but it could also go as high as 10" depending on the track.
Another historic storm for the east coast. What a time to be alive if you're a weather junky like me. The dynamics at play and unprecedented track make Hermine one of the most unique tropical systems I've ever tracked. I noticed some of the news outlets may be underplaying Hermine a bit. While I do not think this will be Sandy-level, she will kind of be Sandy-like with the due west movement toward the coast and that in itself could be disastrous for the shores.
More to come tomorrow. I will have more in the way of timing and impacts.
Have a good night.
-Francesco Paparatto
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