eye on the storm

September 2: Warm and Muggy Labor Day, Tracking Dorian

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LOCAL WEATHER

Scroll down if you want to get right to the details on Hurricane Dorian — we’ll just spend a few sentences and maps to update you on the pre-Dorian forecast. It will be warm and muggy for this Labor Day, with afternoon highs in the mid to upper 80s.

We could see a few pop-up showers or storms this afternoon, with the best chance south and southeast of the Triangle.

The HRRR model’s radar simulation from 10:00am through 10:00pm isn’t very impressed with our rain chances.

Our rain chances will be even lower Tuesday, so temperatures will be a couple degrees hotter.

Still hot on Wednesday, before Hurricane Dorian begins to spread rain chances toward us from the south by Wednesday night.

HURRICANE DORIAN

Dorian made landfall in the Bahamas yesterday with 185 mph sustained winds, and gusts to 225 mph. That makes it THE strongest Atlantic hurricane on record at landfall (tied with the 1935 Labor Day hurricane)…and it’s tied for the second-strongest Atlantic hurricane at ANY point in its life cycle. Hurricane Allen had 190 mph sustained winds in 1980.

Dorian has been creeping to the west over the last 24 hours, doing incredible damage to the Bahamian islands of Great Abaco and Grand Bahama. As of 11:00am, Dorian still has 155 mph sustained winds with gusts to 190 mph, as it drifts westward at just 1 mile per hour.

Over the next 24 hours, Dorian will make minimal progress to the west-northwest, which means Grand Bahama in particular will continue to be punished by Category 5 winds, 20+ foot storm surge, and intense rain.

The storm will begin turning to the north on Tuesday — the National Hurricane Center’s latest forecast shows is running parallel to (but just off) the coasts of Florida and Georgia. While the center of circulation will remain offshore, the storm is large enough that the outer bands will interact with land, so Dorian will slowly weaken. Even with that gradual weakening, it will still be a major Category 3 hurricane by Wednesday night. It finally weakens to Category 2 by Thursday morning.

Dorian will turn to the northeast Wednesday night and Thursday, bringing the storm right along the coasts of South and North Carolina. While the slow weakening trend will continue, Dorian is still forecast to be a Category 2 storm as it passes Wilmington on Thursday and heads for the Outer Banks.

The “cone of uncertainty” still includes the possibility that Dorian takes a sharper turn and heads out into the Atlantic, or the possibility that Dorian tracks just inland from the coast. The forecast model data closely mirrors the NHC forecast, but each model shows a slightly different track.

We can separate the possibilities for Dorian into three categories — along the coast, farther from the coast, or farther inland. Farther from the coast is obviously the best-case scenario for everyone involved. The inland track would help diminish Dorian’s wind speeds — but as the winds relax, the heavy rain would spread out even further. That path would bring the potential for flooding and isolated tornadoes to more of central North Carolina.

One of the better tropical forecasting models, NOAA’s HWRF model, does push Dorian onshore in South Carolina, and follows a slightly inland track into North Carolina. It’s an outlier for now, but its track record does give this scenario some credibility.

The current just-barely-off-the-coast path is the most-likely scenario, which still brings the potential for localized flooding and tropical storm force (39+mph) winds to central North Carolina. Specifically, areas along and east of I-95 will feel the greatest impact.

Every mile matters! If Dorian’s path follows the inland path, every area on that threat map will get adjusted inland by the same distance (or even more, as the storm spreads out). I’m most concerned about flooding in that scenario…and the forecast data is still all over the place. The European forecast model shows the heaviest rain closer to the coast, with rainfall amounts below 4″ in our neck of the woods, even along the southern Coastal Plain.

But the American GFS model, while it shows a very similar path for Dorian’s center of circulation, spreads the heavy rain much farther into central North Carolina. This is more than enough to cause flooding problems, especially in poor drainage areas.

The Weather Prediction Center’s rainfall outlook (working in conjunction with the NHC) shows that the dividing line between “not much rain” and “way too much rain” will fall right across central North Carolina.

We’ve still got a long way to go with this storm, and tropical systems have given us plenty of practice in “expecting the unexpected.” While the heavy rain and wind threats will be greatest along the coast, be prepared for the possibility of localized flooding and some power outages here in central North Carolina as well. We’ll be here all week keeping an eye on the latest data, and we’ll keep you updated!

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