The Slower Hurricane Dorian Moves, the More Dangerous It Is

The hurricane season officially begins June 1, but in reality the action heats up in late August and lasts until October. Hurricane Dorian is just a reminder we are on schedule. 

Dorian began life as a wave of low pressure moving through the tropical Atlantic. Most storm systems fade away. Not Dorian. He became Tropical Depression Number Five last Saturday afternoon. By early Saturday evening Dorian had graduated to Tropical Storm status, first threatening the Antilles, later Puerto Rico and the Dominican Republic. 

Dorian wasn’t yet well organized. The islands are small. He missed them all. 

As Dorian headed into warmer and open water beyond the U.S. Virgin Islands Wednesday afternoon he became a minimal hurricane with top winds of 75 mph. 

Florida is a much larger target than the islands. Florida has good reason to worry. Hurricane Dorian is coming and as much as we know there’s a whole lot we don’t, including exactly where and when it will strike. 

At 4:00 p.m EDT Hurricane Dorian was out in the open Atlantic at 24.8N 70.3W, about 595 miles east of West Palm Beach. Top winds are 115 mph with gusts up to 130 mph. It’s currently moving northwest at 9 mph. 

Hurricane Dorian is now a Category 4 storm on the Saffir-Simpson scale and expected to intensify. There are already Hurricane Watches and Warnings in effect for the Bahamas. Watches usually come 48 hours before the first winds hit. Too early for Florida. 

Dorian’s still out of radar range and a more dense network of sensors to help us model it.

We can see the hurricane has been brushing by an upper air low near Cuba. This frictional interaction slowed Dorian’s intensification until now, but the low is moving away and so is Dorian. 

Until this morning we hadn’t seen a visible eye either. That’s changed. Satellite images and a hurricane hunter recon flight confirm it. The eye is just one sign Dorian’s ramping up. 

In broad strokes, we've got a good idea Florida is Dorian’s destination. As for where in Florida and for how long, that’s still in-the-air. Please understand, as pretty as our maps are and as precise as the lines on those maps look, forecasting the exact outcome of a hurricane five days away is a fool’s errand! Science isn’t there yet. 

The rule of thumb is the slower the storm’s forward motion the tougher it is to accurately predict. Hurricane Dorian might move at a slow to walking pace or stall totally. Nothing could be worse, and it’s not an entirely unlikely outcome. 

That would mean Dorian just drifts offshore for days, battering the coast. We saw that last year with Florence and Michael, both of which caused monumental inland flooding. 

The current forecast brings the center of Dorian through the Northern Bahamas Sunday night and Monday then into Florida early Tuesday. Top winds are forecast at 140 mph. Few structures and little of Florida’s infrastructure are hurricane-proof at 140 mph! 

Dorian will also come with a tidal surge and flooding rain. There’s no prediction for Florida yet, but the Hurricane Center is already talking about tides 10-15 feet above normal in the Northern Bahamas. 

A tidal surge that height would overwash the barrier islands that flank the coast. A1A, Palm Beach and loads of other enclaves of the wealthy would be totally submerged. This would be a bad time to visit Mar-a-Lago, pretty much a geographic worst-case if current forecasts hold.

 And a stalled storm would make this worse and for a longer period. Even as Dorian’s winds subside its rain will continue to fall. Early projections see some areas getting 18 inches of rain—or more. That means inland flooding on top of the coastal concerns. 

Is this a product of human induced climate change? No one can say for sure. Certainly as a forecaster my methods of predicting these storms hasn’t changed. But in subtle ways the underlying conditions have. 

Water temperatures globally are warmer, the mother’s milk of hurricane formation. It’s tough not to worry over the connection. 

The good news, if there is any, is Florida’s recent history with hurricanes has scared folks. It’s difficult to think there’s anyone there who hasn’t seen or doesn’t know what hurricanes will do. That water flew off supermarket shelves so quickly is proof Florida is taking Hurricane Dorian seriously. If only that was enough. 

Meteorologist Geoff Fox has been forecasting the weather on TV so long that if he mentions it he'll never find work again. He's the recipient of seven Emmy Awards.