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Seven tropical systems to watch, including longer term U.S. threat, on peak day of hurricane season

The oceans are blistering with activity, raising concern for eventual land impacts.

The National Hurricane Center's tropical outlook on Thursday morning. (NOAA/NHC)
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Sept. 10 marks the historical peak of Atlantic hurricane season, and right on cue the oceans are blistering with activity. Tropical Storms Rene and Paulette are whirling over the open waters, but there are signs something more ominous could be brewing. Meteorologists are monitoring a total of seven systems across the Atlantic.

Neither of the two named storms is particularly intense right now and won’t bring impacts to land in the near term. But a developing tropical wave soon to emerge off the coast of Africa is already causing meteorologists to raise an eyebrow, with the National Hurricane Center assigning it a “likely” chance of development. This potential storm would be named Sally. Computer models suggest it could take a track that eventually increases the threat for U.S. impacts, but that would be at least eight to 10 days into the future if it materializes.

Behind it, there is another strong tropical wave over Africa that could also eventually develop into a storm.

Much closer to home, yet another system with some tropical characteristics is slinging downpours and thunderstorms ashore over the southern Mid-Atlantic states and Carolinas, with isolated flooding possible. Two additional systems are sauntering into the Gulf of Mexico, with development possible.

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The jam-packed hurricane season has featured the earliest C, E, F, G, H, I, J, K, L, M, N, O, P and R storms on record, with four names left on the 2020 list before we revert to the Greek alphabet in assigning tropical storm and hurricane names.

A typical season contains closer to 11 tropical named storms.

While most storms have been weak and short-lived so far this season, we still have nearly half of the season to go. On Thursday morning, NOAA declared a La Niña event had taken shape in the Pacific. Tropical systems are more numerous in the Atlantic under such conditions.

Paulette and Rene

A pair of tropical storms, Paulette and Rene, are wandering aimlessly around the open Atlantic. The pair formed Sunday night into Monday, and, although the two initially remaining subdued by unfavorable weather conditions, things could soon change.

Paulette, about halfway between Africa and Florida, has winds of 50 mph. Rene, about 800 miles west-northwest of the Cabo Verde Islands, is producing maximum sustained winds of 50 mph.

Both storms look to attain hurricane status, Rene by Sunday and Paulette early next week. While Rene should remain over the open ocean without disturbing land, Paulette could make a close pass or direct hit to Bermuda by early next week. The National Hurricane Center estimates it will be at Category 1 strength by that point.

Three hurricanes have made landfall in Bermuda over the past decade, while Gonzalo’s eyewall clipped the island in 2010 with wind gusts to 130 mph.

There is a nonzero chance that Paulette could inch slightly farther west stronger than anticipated, but aside from an increased threat of rip currents and choppy seas, Paulette is unlikely to bring direct impacts to the Lower 48.

Paulette will likely remain a powerful storm system as it transitions from a hurricane to a mid-latitude “extratropical” system and moves into the North Atlantic by the middle to latter portions of next week.

Sally to likely form by this weekend

A tropical wave just exiting the coast of Guinea-Bissau in Africa shows all the signs of being an incipient named storm. The National Hurricane Center is calling for 90 percent odds of development of that wave in the next five days, noting “a tropical depression is likely to form by this weekend or early next week.”

Tropical depressions are the precursors to tropical storms and hurricanes.

On satellite imagery, the tropical wave is blistering with shower and thunderstorm activity, and weather models indicate it may be a sleeping giant — ready to quickly develop into something we may be tracking for quite some time.

The disturbance will probably begin to mature in the coming days, and the overall weather pattern suggests it will be steered west without turning out over the open Atlantic like Paulette and Rene. That’s thanks to blocking high pressure developing over the northeastern United States and adjacent North Atlantic. With the system likely to be suppressed south, it has a much greater chance of eventually impacting land from the Lesser Antilles into the Caribbean and perhaps eventually the Lower 48 states.

Additional waves exiting Africa prompt concern

Behind soon-to-be Sally, another tropical wave is lurking over Africa. Traversing western Burkina Faso and southern Mali at the current juncture, this wave, too, bears signs of intensification down the road.

The National Hurricane Center gives it a 40 percent chance of development over the next five days, but those probabilities may need to be upped by this weekend once it becomes apparent exactly where the wave will track.

A tropical depression could form by early next week, bringing heavy rain to the Cabo Verde Islands. There are mixed signals regarding its longer-term prospects, but — for the time being at least — it looks acutely less-favored to impact the Americas.

Tropical swirl bringing heavy rain to Mid-Atlantic, Carolinas

Showers and thunderstorms were pivoting onshore from the Delmarva Peninsula and Chesapeake Bay south toward eastern North Carolina on Thursday morning, in response to a trough of low pressure stationed just offshore.

While the system would likely become more interesting if it had more time to spend over the anomalously warm waters of the western Atlantic, the clump of unsettled weather is moving inland at present. That renders additional tropical development impossible.

Locally heavy rainfall is possible where downpours train, or move over the same areas repeatedly. A flash flood watch is in effect from the Virginia Tidewater north into New Jersey.

Dual disturbances in the Gulf of Mexico

A clumping of showers and thunderstorms east of the Bahamas was slowly propagating westward early Wednesday and showing signs of development. For the time being, wind shear — or a disruptive change of wind speed and/or direction with height — limited the systems near-term prospects of maturation.

The system is slated to cross the central and southern Florida Peninsula this weekend, bringing heavy downpours and 1-to 3-inch rainfall totals for some.

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Eventually, it will move into the eastern Gulf of Mexico early next week, where slow development is possible before it arrives along the northern Gulf Coast, perhaps in Louisiana, late in the weekend. Heavy rainfall is the primary concern.

Another weak system in the western Gulf will slowly pivot toward coastal Mexico in the coming days with enhanced shower and thunderstorm activity in Tamaulipas and Veracruz, but impacts on the United States should be negligible.