On Monday afternoon, the fifth named storm of the 2024 Atlantic hurricane season formed about 300 miles east of the easternmost Caribbean islands.
Tropical Storm Ernesto is bringing gusty winds above 45 mph to the Leeward Islands this morning as conditions quickly deteriorate across Puerto Rico and the U.S. Virgin Islands on Tuesday.
Ernesto is forecast to make its closest approach to the U.S. territories by late Tuesday or during the overnight hours of Wednesday as a moderate tropical storm.
The biggest hazard Ernesto will bring to the islands is a considerable threat for flooding, with mudslides likely in areas of steep terrain. Rainfall totals could top 8 inches in some areas.
Gusty winds topping 60 mph are also possible, especially by late Tuesday, as Ernesto strengthens.
Waves approaching 20 feet will accompany the storm, bringing treacherous marine conditions into Wednesday, including areas of coastal flooding and beach erosion.
Ernesto will turn northward on Wednesday, with its center moving north and east of the Dominican Republic, and should become a hurricane by late tomorrow or early Thursday over western Atlantic waters.
A pronounced jet stream dip will allow Ernesto to escape into the North Atlantic, but the recurve will take the strengthening hurricane precariously close to Bermuda by the weekend.
Though Ernesto’s powerful circulation will drive significant swell to the Eastern Seaboard this weekend, it will not pose a direct threat to the mainland U.S. coastline.
Ernesto - A historically fast tropical storm
When it formed Monday afternoon, Ernesto was moving at 28 mph, a remarkably fast clip for a named storm in the deep tropics. In fact, fewer than 1% of named storms in the tropical belt ever achieve such a quick pace, mainly because the fast forward movement typically disrupts a tropical cyclone’s circulation.
Of those few named storms that have moved as quickly as Ernesto through the tropical belt, most have done so in the vicinity of Ernesto’s formation zone Tuesday.
Ernesto’s translational speed is a key piece to the bigger development picture. Even when it was upgraded to a tropical storm yesterday, its circulation wasn’t well established, with weak and variable winds to the south side of its broadly turning winds.
Although its fast forward motion from the east was enhancing the blustery tropical storm winds on the north side of its circulation, it was also counteracting what might otherwise be stronger and better-defined winds on its southern side.
As a result, a three-dimensional look at its circulation from the tail doppler radar of NOAA hurricane hunters flying Ernesto last night continued to find an open and struggling circulation.
Removing the fast forward speed, however, revealed a much more coherent circulation with little “tilt,” indicating a very conducive environment for strengthening once the developing storm slowed down.
Ernesto is now beginning to tap the breaks as we anticipated, with its forward speed at a still-swift but slower 18 mph. This has allowed for a noticeable improvement in the circular, “closed” appearance of its center this morning, as seen by NOAA hurricane hunters flying Ernesto this morning, compared to last night.
The more robust circulation is critical because it allows for more persistent thunderstorm growth that kicks off the flywheel of development. This morning, hurricane hunters are finding falling pressures in addition to an improved wind field. As Ernesto bends northward into Wednesday, it will continue to slow, which will keep it on a strengthening trend.
Bermuda in the crosshairs
The environment for strengthening looks ripe over the western Atlantic, with the jet stream dip pulling Ernesto northward also helping to enhance outflow on the northern side. Ernesto is expected to be near major Category 3 status as it approaches Bermuda over the weekend.
There still remains a decent spread in possible outcomes for Bermuda depending on whether Ernesto takes a track east, west, or over the islands, but those with interests in Bermuda should continue to monitor the forecasts closely this week as a powerful hurricane could be nearby as early as Saturday.
Models mute for now behind Ernesto
Yesterday, we discussed the overall conducive configuration of the tropical Atlantic for the remainder of August. At least for now, our long-range models aren’t sniffing out any strong signals for development behind Ernesto.
We’ll of course keep an eye on the next waves moving deeper into the western Atlantic, but the mainland U.S. is off the hook for another week.