Weather Outside Your Window: Atmospheric river to transport tropical moisture to Atlantic Canada

By Courtney Travis, AccuWeather senior meteorologist

Published Jun 28, 2023 1:12 PM EDT | Updated Jun 29, 2023 4:52 AM EDT

AccuWeather meteorologists continue to monitor both the Atlantic and East Pacific Ocean basins for signs of new tropical activity.

The most recent tropical storm to form in the Atlantic basin was Cindy, which became the third named tropical system since the start of the season when it developed late on Thursday, June 22. After losing wind intensity, AccuWeather continued to track Cindy as a tropical rainstorm that could bring potential impacts to North America.

While Cindy has lost wind intensity and is no longer a trackable feature, the tropical moisture from what's left of the storm still remains and is now being transported to Atlantic Canada, thanks to a developing atmospheric river over the Atlantic Ocean.

"While we often hear about atmospheric rivers impacting the West Coast of the U.S., they can happen along the East Coast as well," said AccuWeather Meteorologist Alex DaSilva.

DaSilva explained that the influx of moisture will be aided by a dip in the jet stream across the Northeast, helping to transfer the lingering moisture from Cindy northward.

"The atmospheric river bringing the tropical moisture to Atlantic Canada will be beneficial for much of the region, which is currently in a drought," DaSilva added.

Much of eastern Quebec, Newfoundland, Labrador and Atlantic Canada is abnormally dry, according to the North American Drought Monitor. Portions of New Brunswick, Nova Scotia and Prince Edward Island are even in a state of moderate or severe drought.

Rainfall from Cindy is expected to impact parts of Atlantic Canada, and forecasters say as much as 1–2 inches could fall in just a couple of days. Given the dry soil, downpours producing an inch or more of rain in a short time could cause localized flash flooding issues.

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AccuWeather meteorologists continue to monitor other areas for tropical development in the Atlantic basin despite the waves of dry air and strong wind shear that are expected to prevent tropical development across most of the Atlantic into early July.

However, prior to midweek, forecasters were studying an area of disturbed weather several hundred miles to the southeast of Bermuda. Should an organized tropical feature come to fruition, it is likely to pass east of Bermuda before slowly moving northward.

The track of any feature that develops will be influenced by a dominant area of high pressure over the North Atlantic. Should this high remain strong and an organized tropical feature were to form, the feature is likely to pass east of Bermuda before slowly moving northward.

Adrian, first hurricane of 2023 in East Pacific, forms

The first named storm of the East Pacific tropical season formed on Tuesday when Tropical Storm Adrian took shape with winds of 45 mph. Adrian formed in one of two areas of the basin that AccuWeather meteorologists have been monitoring since last week.

As of Wednesday evening, Adrian had rapidly strengthened into a Category 1 hurricane located about 370 miles southwest of Manzanillo, Mexico, according to the National Hurricane Center (NHC). Adrian was moving to the west at a speed of 6 mph and had maximum sustained winds of 80 mph.

"Adrian is most notable because it's the first named storm and first hurricane of the tropical season. With a generally westward track expected for the coming days, Adrian is unlikely to have any impacts to land," DaSilva explained. Adrian is likely to remain a hurricane through the end of the week.

Adrian's formation during the final week of June marks an unusually late start to the East Pacific season. Only in 2016, when Agatha formed on July 2, did it take longer for the first named storm to develop in the basin.

The East Pacific hurricane season annually begins on May 15, a couple of weeks ahead of the Atlantic season which officially gets underway on June 1. The average first date that a named storm forms in the East Pacific is on June 10, according to the NHC. Several other areas in the East Pacific were monitored by AccuWeather forecasters in recent weeks, but none became organized enough to become tropical storms.

In addition to Adrian, meteorologists continue to scrutinize a tropical wave to the east of Adrian, closer to the southern shores of Mexico. It is possible that a tropical depression could form in this area in time for the weekend.

The potential for this storm to form closer to Mexico means that there could be some impacts felt in some coastal areas. At the very least, rough surf and strong rip currents may develop along Mexico's southern beaches from this weekend into early next week. It's not out of the question that some outer rain bands from a stronger tropical system could reach the southern Mexico coastline as well. This rain could lead to slowed travel and perhaps some flash flooding.

Due to expected effects in Mexico, the National Hurricane Center (NHC) designated that system as "Potential Tropical Cyclone Two-E" as of Wednesday evening. This gives the NHC the option to issue advisories on a system even before it develops a closed circulation, if it will impact land. As a result of Potential Tropical Cyclone Two-E, tropical storm warnings were issued for portions of the Mexican coast. Once the system develops a closed circulation, it becomes a tropical depression. This occurred Thursday morning, and the system became Tropical Depression Two-E. When it strengthens to a tropical storm, it will be given the name Beatriz, the next name on the 2023 East Pacific hurricane list.