Isaias passing by Charleston, flooding around high tide a concern Monday night

CHARLESTON, S.C. (WCIV) — Tropical Storm Isaias is making its pass by the Lowcountry Monday afternoon, as it gains speed and becomes better organized on its way north.

The 5 p.m. advisory from the National Hurricane Center shows the storm's center about 60 miles south-southeast of Charleston, moving north-northeast at around 16 mph. That's up from 9 mph only 12 hours earlier, showing the storm picking up speed.

The storm's maximum sustained winds remained near 70 mph at 5 p.m.,as they have for much of the day. Higher gusts have been observed at sea, while sustained winds of 45 mph and a gust of 52 were recorded at Folly Beach.

The storm was showing better organization as of 5 p.m., and forecasters still are expecting Isaias to strengthen and become a hurricane again before making landfall somewhere near the South Carolina-North Carolina border later Monday evening.

Georgetown and Horry counties remain under a Hurricane Warning in South Carolina, with coastal areas of North Carolina up to Surf City above Wilmington also under the hurricane warning.

As for Charleston and the Lowcountry, skies had begun to clear along the coasts of Beaufort and Colleton County south of Charleston as of 5 p.m., with the last of Isaias rain bands making their way onshore along the storm's northward trek.

Isolated heavy rain continued to fall Monday afternoon, putting flood-prone Charleston on alert for an increased risk of flooding later in the evening.

ABC News 4's Storm Tracker team of meteorologists predict high tide in the Charleston Harbor to peak near 7.5 feet shortly before 9 p.m. Coastal flooding begins around the Charleston Peninsula with tides around 7.2 feet under normal conditions.

However, Isaias is expected to have mostly passed by Charleston leading up to high tide, and any abnormal coastal flooding one might expect at high tide amid tropical weather may be minimized by the dissipating impacts of the storm when the tide peaks.

Storm surge likely will not contribute to flooding in the Charleston area, as Isaias is forecast to produce minimal if any storm surge along the southern portion of South Carolina's coast.

In fact, if the storm continues to pick up speed, its winds will be offshore around the time of high tide, according to Meteorologist Sonya Stevens. In that scenario, flood impacts may not be much of an issue beyond what's normally seen in flood-prone areas.

As of 5:30 p.m., only two streets on the Charleston Peninsula were closed for flooding: Broad Street between Rutledge and Ashley Avenues, and Colonial Street between Broad and Tradd Streets. You can monitor street closures in the City of Charleston on its dedicated website.

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