Coastal Flood Advisory

Isaac may attempt to restrengthen before reaching the Gulf of Mexico

By Kristina Pydynowski, AccuWeather senior meteorologist
September 17, 2018, 12:57:04 AM EDT

Isaac has not met its demise over the Caribbean Sea as it may attempt to restrengthen into a tropical depression or storm before reaching the Gulf of Mexico early this week.

While once a hurricane over the central Atlantic Ocean, Isaac remains a weaker tropical rainstorm churning through the central Caribbean Sea.

"However, there is a small chance Isaac can regenerate into an organized tropical system as it approaches the Yucatan Peninsula or southern Gulf of Mexico by Tuesday or Wednesday," according to AccuWeather Senior Meteorologist Dan Pydynowski.

Isaac is moving into an area of lower wind shear and water that is more than sufficient to provide fuel for a tropical system.

Wind shear is the increase in wind speed with altitude or over horizontal distance. Strong wind shear can prevent a tropical storm from forming and cause a hurricane to weaken. A small amount of wind shear can vent a tropical storm or hurricane just enough to allow it to strengthen.

Isaac factors Sep 16

"AccuWeather meteorologists are not suggesting that Isaac will turn into another Harvey, which fell apart entering the western Caribbean and then rapidly regained strength while moving across the Gulf of Mexico," AccuWeather Senior Meteorologist Alex Sosnowski said.

“While people from the western Caribbean to the Gulf Coast of the United States should go about their business, they are urged to monitor the situation for any significant changes in Isaac’s strength, but at the same time not dismiss Isaac."

Regardless of strengthening, Isaac will continue to spread localized drenching showers and thunderstorms westward from Hispaniola to Jamaica and Cuba into midweek.

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There can be isolated incidents of flash flooding, but most of the downpours may just be a nuisance to residents and visitors by disrupting outdoor and vacation plans.

As soon as thunder is heard, the risk of being struck by lightning is present.

Outside of any short-term issues, the downpours will be beneficial in areas that are suffering rainfall shortages this summer.

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Rain and gusty winds would increase if Isaac organizes into a depression or storm. Seas may become choppy and more hazardous to swimmers and operators of small craft if this occurs.

The opportunity for Isaac to restrengthen may lessen as it enters the Gulf of Mexico later this week.

"Regeneration is unlikely at that time as Isaac will move into a zone of higher wind shear," Pydynowski said.

If Isaac is a tropical depression or storm at that time, such wind shear may cap further strengthening or cause it to weaken once again. Land interaction with the Yucatan Peninsula can also inhibit strengthening.

Even if Isaac never re-intensifies, it may still bring another round of downpours to Louisiana or Texas around Friday or Saturday. With the ground saturated from recent heavy rain, frequent downpours could trigger flash flooding.

While AccuWeather meteorologists monitor Isaac, another budding tropical system in the eastern Pacific Ocean could increase showers, thunderstorms and the risk for flash flooding across the Desert Southwest later this week.

Download the free AccuWeather app to keep up-to-date with any bulletins related to Isaac.

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