eye on the storm

August 29: Calm Weather Locally, Tracking Dorian

Weather
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WEATHER

It’s a good thing that the weather over central North Carolina will be so calm for the next few days, because we’ve got our hands full trying to figure out what Dorian is going to do this weekend.

Humidity levels dropped overnight, and we get to enjoy a couple days in “nice” territory on the Muggy Meter, with one more “tolerable” day on Saturday.

Highs today will reach the 80s — comfortably warm, considering the low humidity.

The lower the humidity, the more temperatures can drop overnight. We’ll drop to the 50s and 60s by early Friday — below 60° in the Triangle for the first time since mid-June!

Just a couple degrees warmer on Friday, close to normal for late August.

We’ll reach back up to around 90° on Saturday, then the humidity slithers back in for Sunday and Monday. That will lead to a chance for a few spotty showers or storms, with the best chance south of the Triangle.

Don’t cancel any outdoor plans for Sunday and Labor Day, just have an indoor “just-in-case” alternative in mind. Our rain chances trend upward by mid-week, as the remnants of Hurricane Dorian come into play. Speaking of Dorian…

HURRICANE DORIAN

As of this morning, Dorian is a Category One hurricane, with 85 mph sustained winds and gusts over 100 mph. The storm is re-organizing itself, a precursor to further intensification.

The National Hurricane Center’s latest forecast shows Dorian becoming a major Category Three storm by tomorrow night as it tracks to the northwest.

The NHC forecast farther down the line shows Dorian maintaining that Category Three strength (getting awfully close to the 130 mph Category Four threshold) as it makes a turn to the west and slows down. The “Space Coast” of eastern Florida is still in the crosshairs for landfall early Monday morning, but the cone of uncertainty extends all the way from Miami to Savannah.

The westward curve to Dorian’s path will be caused by a “Bermuda high” — a mountain of calm air steering everything around it. If the high weakens, the storm can go farther north, if the high gets stronger, Dorian will be pushed farther south. There’s plenty of warm water to fuel its development regardless of which path it follows.

The forecast model data isn’t being very helpful beyond 72 hours or so. There are three scenarios that could play out this weekend:
1) The Bermuda High pushes Dorian straight west. The storm slows down, but maintains enough momentum to make landfall near the Space Coast, then weakens as it moves inland. The remnants turn north, eventually bringing rain to central North Carolina.
2) The Bermuda High weakens, and Dorian slows down even more before landfall. The storm turns north before landfall, becoming more of a threat to the coasts of Georgia and South Carolina…maybe even North Carolina.
3) The Bermuda High gets even stronger or drifts to the southwest. Dorian charges inland closer to West Palm Beach or even Miami, then moves quickly across the Florida peninsula. The storm emerges into the warm waters of the Gulf, then turns northward for another landfall in the Florida panhandle.

The global forecast models largely favor the first scenario, which is what the National Hurricane Center is forecasting. That’s the direction I’m leaning as well. But a few models still project a northward turn before landfall…those models are outliers for now, but we’re going to have to keep a close eye out for that potential trend.

Looking at just the 51 members of the European forecast models ensemble, they seem evenly split between all three potential scenarios.

The “spaghettios” animation from the European ensemble shows all 51 versions of Dorian’s position and strength through the middle of next week — this really illustrates the uncertainty in the long-range forecast.

With the extended forecast so up in the air, here’s a breakdown of what we know, what we think we know, and what we don’t know yet.
WHAT WE KNOW: Dorian will strengthen over the next 48 hours, and its track will take a turn to the west. It will eventually turn back to the north.
WHAT WE THINK WE KNOW: Dorian will become a major hurricane before landfall sometime Monday, and its forward progress will slow down. The slowing trend will lead to a threat of coastal and inland flooding, and significant coastal erosion wherever the storm makes landfall. (The fact that Dorian’s landfall coincides with abnormally high “king tides” just makes it that much worse.)
WHAT WE DON’T KNOW…YET: Will a small pocket of higher wind shear in Dorian’s path significantly impact its intensification? When does that turn to the north occur — before landfall? Right afterward? Much later, after the storm is in the Gulf?

The hurricane hunters will be out gathering more data today, and over the next several days. That data is crucial to giving us a picture of the storm’s structure, which the forecast models then use to simulate its future movement and strength. THERE WILL BE MORE CHANGES TO THE FORECAST. It’s important, even over the holiday weekend, to stay plugged into the forecast for those changes. I’ll be posting updates on social media (here are links to my Twitter, Facebook and Instagram feeds), and of course we’ll be on-air with updates during our regular newscasts. We’ll be impatiently waiting on every batch of new data, so we can evaluate any potential shifts.

What should you do? Depends on your plans! If you were heading to Florida this weekend, I’d be ready to pull the plug on that. If you’re heading to the North Carolina coast for the holiday weekend, I certainly wouldn’t cancel — but I would stay aware of any changes to Dorian’s path.

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