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What to know about Hermine and how it may affect the Northeast

Tropical Storm Hermine formed earlier today in the Central Gulf of Mexico, after several days of being tracked and obsessively monitored by meteorologists and weather hobbyists alike. Regardless, the storm has strengthened over the last 24 hours and is expected to continue to do so as it moves northeastward towards the Florida Peninsula. Thereafter, forecast models have taken a dramatic turn in their handling of the storm system.

Current forecast model guidance and ensemble data suggests that Hermine, after making landfall along the Florida Peninsula, will track northeastward along the Southeast Coast before re-emerging off the Mid Atlantic shoreline. As this occurs, the storm will begin to interact with an upper level system which is forecast to drop southward through the Ohio Valley and Mid Atlantic States. This interaction may pull Hermine westward back towards the Mid Atlantic and/or Northeast US coasts by late this weekend into Labor Day.

Why is this type of evolution possible? 

An amplified pattern in the atmosphere will allow an unusual amount of energy to drop southward into the Ohio Valley late this week and weekend. With a large ridge forming over the Atlantic Ocean and another in the Central US, Hermine will be forced between the two features and “guided” up the East Coast.

What happens thereafter is critical — and forecast models suggest that the amplified pattern will allow Hermine to interact and phase with the aforementioned energy over the Ohio Valley. Such a process is sufficient to pull the storm westward, back toward the Eastern Seaboard.

GFS model showing two key features with Hermine that may aid in bringing the storm up the East Coast as they interact.

GFS model showing two key features with Hermine that may aid in bringing the storm up the East Coast as they interact.

These patterns are fairly unusual, but have occurred before. Typically, when two large blocking ridges exist, as forecast models show, a sprawling high pressure develops to the north — and acts as a “block” to force the system to slow down. Models are suggesting this exact process later this weekend with Hermine.

What kind of impacts can we expect? 

Such a system is very likely to produce a myriad of impacts near its track — and several hundred miles around it. However, the strength of the system and its exact interaction with the upper level energy over the Ohio Valley will dictate how much the system really strengthens, where it tracks, and who feels the greatest impacts.

Regardless, areas within and near the track of the system can expected heavy rain, strong winds, and the potential for coastal flooding and beach erosion. The storm system may draw in a considerable amount of energy from the east, if if tracks south of our area, resulting in considerable concerns from the mentioned coastal flooding and storm surge. It remains to be seen, as mentioned, how strong the winds will be and which areas will be hit the hardest — as the track of the system is still a significant uncertainty.

GFS model showing very strong onshore winds pushing into the NJ Coast on Sunday.

GFS model showing very strong onshore winds pushing into the NJ Coast on Sunday.

Do we know the exact track of the storm yet?

In short, no. Forecast models continue to hone in on a general track area. Overall, the trend over the past 24 hours has been westward — closer to the Mid Atlantic Coast. Several global weather models take the storm system to a position near the Mid Atlantic Coast early Sunday morning, with strong winds and coastal flooding along the NJ and NY Beaches. Other models remain further east with lesser impacts.

What should I do to prepare?

For now, conduct basic storm preparation procedures, especially if you live along the coast or in a storm-prone area. Make sure to have an evacuation plan, consider if your area is prone to high winds or flooding. If you live along the beaches, closely monitor the forecast and remain vigilant of any planning you may need to conduct based on forecasts over the next 24 hours.

It is important to stress that considerable uncertainty still exists with the track and intensity of the storm system, which is still in the Central Gulf of Mexico. While confidence is increasing in impacts throughout the NJ, NY area , the degree of those impacts remains highly uncertain and may vary greatly depending upon location.

The best advice at this time is to continue to monitor forecasts while conducting basic and standard preparatory procedures. More updates are scheduled, based on the latest data, for Thursday afternoon.

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