September 19, 2019
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Hurricane Dorian barrels toward Southeast U.S. as likelihood of direct hit on Florida decreases

NOAA via AP | BDN
NOAA via AP | BDN
This GOES-16 satellite image taken Saturday, Aug. 31, 2019, at 16:00 UTC and provided by National Oceanic and Atmospheric Administration (NOAA), shows Hurricane Dorian, right, churning over the Atlantic Ocean.

With peak winds of 150 mph, Hurricane Dorian is as imposing and threatening as ever as it churns toward Florida and the Southeast United States. But because of a shift in model forecasts toward the east, it is possible that Florida may miss the full fury of this severe hurricane while areas farther north into coastal Georgia and the Carolinas face an increasing risk.

Even so, the National Hurricane Center is urging Floridians not to let their guard down and to continue preparing for an “extremely dangerous” hurricane. As of 2 p.m. Saturday, the storm was centered 205 miles east of Great Abaco in the Bahamas, and was headed west at 8 mph. While not explicitly forecast, it’s possible the storm will reach Category 5 intensity for a time on Saturday.

“Life-threatening storm surge and devastating hurricane-force winds are still possible along portions of the Florida east coast by the early to middle part of next week,” the center wrote as a key message in its 5 a.m. bulletin. “Residents should have their hurricane plan in place, know if they are in a hurricane evacuation zone, and listen to advice given by local emergency officials.”

The Hurricane Center shifted its official forecast track east, just off the Florida coast, but still within striking distance of the state. “It should be noted that the new forecast track does not preclude Dorian making landfall on the Florida coast, as large portions of the coast remain in the track cone of uncertainty,” it wrote. “Also, significant impacts could occur even if the center stays offshore.”

If the storm makes a close pass to Florida, tropical-storm-force winds could arrive as soon as Sunday or Sunday night. Because the storm is predicted to be a slow mover, effects from wind, rain and storm surge – which is the storm-driven rise in water above normally dry land at the coast – could be prolonged, lingering through the middle of next week.

It seems more likely that northeastern Florida, rather than southeastern Florida, will experience hurricane conditions.

Although the risk of a hurricane disaster has decreased some in Florida, it has become more likely that coastal Georgia to the Carolinas will have to deal with serious effects from Dorian by the middle of next week.

“The risk of strong winds and life-threatening storm surge is increasing along the coasts of Georgia and South Carolina,” the Hurricane Center wrote. But even here, there is large uncertainty in the storm track.

Irrespective of the storm’s ultimate course near Florida’s east coast to the North Carolina Outer Banks – or even inland – significant coastal flooding is likely due to the force of Dorian’s winds and astronomically high or king tides.

Despite the uncertainty in Dorian’s track and its specific impacts along the southeastern U.S. coast, confidence is high that the northwestern Bahamas face a punishing hit from the storm. A hurricane warning is in effect for this region, and the Hurricane Center projects “devastating hurricane-force winds,” at least 10 to 15 inches of rain (with isolated 25-inch totals) and a “life-threatening” storm surge of 10 to 15 feet in areas of onshore winds. The storm may pass near or directly over the islands of Abacos and Grand Bahama while moving at a slow forward speed.

Minor fluctuations in the storm’s intensity are forecast through Sunday before a slow weakening trend beginning Labor Day, due to proximity to land and increasing wind shear. Even so, the Hurricane Center still forecasts 110 mph peak winds as the storm approaches the Carolinas on Wednesday night.

Dorian underwent an astonishing rate of strengthening Friday night, with its central pressure dropping 24 millibars in just six hours – plummeting from 970 to 946 millibars. The lower the pressure, the more intense the storm.

The risk to Florida of a direct strike has decreased because the predicted intensity of the high pressure zone that was supposed to push Dorian west into the state has weakened some. As a result, most models show steering currents collapsing as Dorian nears Florida, before it gets scooped up by a dip in the jet stream approaching the East Coast and starts turning north.

However, this collapse in steering currents is so close to Florida that some models continue to track the storm close enough for damaging impacts in parts of the state.

In its early morning discussion, the Hurricane Center wrote that models it “normally uses” shifted the storm track far enough east that “none of them forecast Dorian to make landfall in Florida,” but it cautioned some other models still bring Dorian over Florida. Significantly, one of these models is the UKMet, which is among the most accurate and a reason for Floridians to remain prepared.

Farther north into coastal Georgia and the Carolinas, the forecast is also a nail-biter. Just small differences in where the storm starts to turn north and eventually northeast and the shape of the turn will determine where and whether Dorian makes landfall.

Because it isn’t for another four to seven days before Dorian will make its closest approach to this zone north of Florida and forecasting the track has large errors so far out, it’s not possible to pinpoint if and where the storm will make landfall and how close it will track to the coast. Scenarios involving a direct hit, a graze and a near miss appear equally likely based on available forecasts. As the Hurricane Center writes: “Residents in those areas should continue to monitor the progress of Dorian.”

The shape of the coastline from northern Florida through the Carolinas means there is a risk of significant storm-surge flooding there even if the storm’s center remains just offshore.

 



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