By the time you read this on Friday, Tropical Storm Erin will likely be the first hurricane of the Atlantic season. In fact, the National Hurricane Center expects it to become a major hurricane later in the weekend, which means it will reach or exceed a Category 3 rating on the Saffir-Simpson scale. Here is the latest information on what is expected to be a large, powerful hurricane and whether it will impact the United States.
U.S. Territories Will Be Affected
Puerto Rico and the U.S. Virgin Islands will be impacted by Erin. Though the storm will pass just north of the islands, it has a fairly large footprint. NHC wrote Friday morning, “Tropical Storm Erin is expected to produce areas of heavy rainfall beginning late Friday and continuing through the weekend across the northernmost Leeward Islands, the U.S. and British Virgin Islands, as well as southern and eastern Puerto Rico.” I would not be surprised if the expected 2 to 6 inches of rainfall causes landslides or mudslides in elevated terrain, Additionally, flash flooding in susceptible areas and urban regions is possible.
Tropical Storm Watches are currently up for some of the islands as wind speeds in excess of 39 mph could scrape them as the storm passes just north of them. Locations at higher elevations could be particularly vulnerable to the higher wind speeds. As someone who cruised to the U.S. Virgin Islands earlier this summer, the track of Erin is a reminder of why I advised my wife not to book it after August 1. During day excursions, my meteorological eye was focused on the homes near sea level and in the hills.
What about the U.S. Mainland?
What about the U.S. mainland? There has been a lot of chatter and hyperbole about Erin over the past several days. In this hyper-media and social media era, people start talking about these storms before they have even formed. At the time of writing, Erin is still trying to become better organized. On Friday at 5:00 am, NHC wrote, “Erin has struggled to become better organized tonight, as the system is still trying to establish an inner core.” However, they expect it to move into a more favorable environment for strengthening later Friday morning. Sea surface temperatures are quite warm along the forecast track, and wind shear is expected to slightly decrease.
Our best global models indicate that the East Coast of the U.S. should be spared from a direct hit by Erin. There is an “atmospheric escape door” that the storm will likely slip through that will take the storm into the North Atlantic Ocean somewhere between the U.S. East Coast and Bermuda. Earlier in the week, the European AI model had the storm coming perilously close to the Carolinas. At that time, I cautioned readers not to jump on that train too early. While AI offers promise, the first generation of AI weather models will need some time, and to be fair, it was still over ten days out.
NOAA’s Weather Prediction Center noted, “Shortwave energy ejecting from an initial trough over the Northwest into Canada will help flatten the flow over the northern tier allowing for a more progressive trough across eastern Canada/the Northeast. This should help pick up what should be Hurricane Erin and steer it away from the East Coast quickly.”
That trough and a high-pressure system over the Atlantic Ocean are critical for creating that “escape door,” and there are some differences among our best models. For example, the European model solution, while still offshore, does bring Erin a bit closer to the U.S. coast than the American GFS model. While the exact position varies by model, they all indicate that Erin will not make landfall in the U.S. However, there will be indirect impacts along the coastal East Coast, so if you reside or visit next week, you should take precautions at the beach. Large swells and rip currents could be a problem much of next week from Florida up through the Mid-Atlantic region.
