RICHMOND — Get ready for a tropical soaking throughout Virginia on Tuesday.
As Hurricane Isaias whirled into range of Miami’s weather radar on Saturday, it had the ragged look of a storm that was struggling against the dry winds that surrounded it. By 5 p.m., it was back down to a tropical storm with 70 mph sustained winds.
But that weakening wind trend near Florida actually plays into a wetter outlook for Central Virginia, once the storm curves northeast on Monday night and Tuesday.
Three trends are coming into view:
» A now-weaker Isaias is more likely to favor the western side of the forecast paths we’ve seen recently. The center is most likely to remain inland as it parallels the coastline of North Carolina and Virginia, rather than going right over the beaches or staying offshore. A more powerful hurricane might have trended farther east.
» The storm’s center will take longer to reach our region than it first appeared, likely crossing eastern Virginia on Tuesday morning and afternoon. But the moist air surging northward ahead of it will meet an approaching front and wring out precursor rains as early as Monday.
» The combination of those trends means a wetter outlook for much of the state and a risk of flash flooding. Many areas will see a few inches of rain during a six- to 12-hour window, and some could see several inches.
There isn’t a great deal of east-west wiggle room in Isaias’ future path now. After hugging the Florida coast on Sunday, it will accelerate northeastward between the clockwise winds of a ridge over the western Atlantic, and the counter-clockwise flow around a trough over the Midwest.
But some uncertainty about its pace along that track has made the arrival time hard to pin down. Now, most computer models bring Isaias’ center, and most of its rain, across Central Virginia between late Monday night at the earliest and Tuesday evening at the latest.
By Tuesday night, Isaias will race up the Mid-Atlantic coastline and wind up in New England on Wednesday.
Though the waters between Miami and Myrtle Beach are warm enough to fuel a hurricane, the system is more likely to be a tropical storm by the time it affects Virginia. Hostile shearing winds and the interaction with land are the main factors that would keep its intensity in check.
Typically, the higher winds are on the right side of a storm’s path. So if Isaias’ center travels northeast across the coastal plain, the tropical storm-force winds are most likely to be felt around the Chesapeake Bay and the Eastern Shore.
Richmond should be in line for a breezy Tuesday at the very least, but some higher gusts to 40 or 45 mph can’t yet be ruled out. Given the track, the gusty wind potential is much lower for areas west of Interstate 95.
Heavy rainfall is the key thing to watch for inland parts of Virginia.
Tropical rainfall rates of 1 to 2 inches per hour could prove excessive and lead to flash flooding.
Given the storm’s size and speed, most of the rain would fall in a window of six to 12 hours sometime on Tuesday. The peak rainfall may occur in the morning or midday hours, but that can be better narrowed down by Monday.
Generally, we can expect totals of at least 2 inches on Tuesday throughout Central Virginia, with 3 to 4 inches of rain a realistic outcome.
In a high-end scenario, a narrow corridor near or just west of the storm’s track could see double those amounts. That several-inch rain zone might line up near Richmond, the Tri-Cities, Fredericksburg or Williamsburg if the storm stays on track.
Those heavier amounts are less likely to set up near Charlottesville, Lynchburg and the western Piedmont, but a steady rain of a lower magnitude is still a good bet for most corners of the commonwealth.
The storm’s thick clouds and rain also could keep Tuesday’s highs down into the mid- or lower 80s.
It’s not uncommon for tropical storms to spawn brief tornadoes. Though specifics are impossible to predict this far in advance, the eastern third of the state may see more of the spin-up tornado ingredients in place on Tuesday.
For Tidewater, the storm’s fast movement may keep coastal flooding concerns to a relative minimum, but beaches will see higher surf and rip current danger starting Sunday and the waters will likely be dangerous for small craft by Monday night.
By midweek, the rainfall runoff would lead to higher river levels across the Piedmont. Major river flooding appears unlikely because it’s a fast-moving storm, but the pattern of the rainfall will determine which rivers may go into minor flooding.
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