Catastrophic Hurricane Dorian Strikes The Bahamas; Future Track Confidence Increasing

Last night, Hurricane Dorian intensified into an elusive category 5 hurricane to the east of Great Abaco. It has since intensified to become the strongest hurricanes to make landfall not just in the Atlantic, but also across the planet, striking the Abaco islands with winds of 185mph and gusts up to 220mph. This makes Dorian the joint second strongest hurricane by wind speed ever recorded in the Atlantic basin, tied with several other storms in second place. The hurricane will remain catastrophically intense as it crawls through the northwestern Bahamas, including Great Abaco and Grand Bahama, before making an important northward turn sometime on Tuesday. Past then, while the forecast remains somewhat uncertain, confidence on the storm’s path is starting to increase.

Visible imagery of Hurricane Dorian making landfall on Great Abaco with a jaw-dropping presentation. (MSFC)

From a meteorological standpoint, Dorian’s satellite presentation is absolutely breathtaking. The core is almost perfectly symmetric and the eye is incredibly deep. In some ways, it’s a textbook hurricane. Aircraft Reconnaissance has been observing these winds increasing and the pressure dropping still, all the way down to 910mb. It is moving west at a measly 7mph, meaning that the core of violent, cataclysmic conditions is also not moving very fast. This means that the Abaco Islands are currently experiencing category 5 hurricane conditions that are barely chugging along. Comparisons can be drawn to Hurricane Irma in Barbuda 2 years ago, which struck the island at a similar intensity. However, Irma was moving more than twice as fast as Dorian. Given its extreme intensity, Dorian is tied with the Labor Day Hurricane of 1935 as the strongest hurricane to ever make landfall in the Atlantic by wind speed (although the Labor Day Hurricane was about 20mb deeper at landfall in the Florida Keys).

AF302 mission data, showing a falling pressure and increasing winds as Dorian progresses west. (Tropical Tidbits)

Dorian will likely remain catastrophically intense as it crawls west towards Grand Bahama, where similarly devastating conditions will strike by tonight. The ridge to the northeast has been stationary and getting farther away from the hurricane, and another ridge over the northeastern Gulf is causing the storm to slow even further. The hurricane will only continue to keep a steady motion for the next few hours and then slow down even further as it approaches Grand Bahama. There is the potential that the storm may weaken slightly if the internal structure of the storm adjusts through an eyewall replacement cycle. This would cause the maximum winds to decrease, but it also extends the storm’s wind-field and generates 2 sets of eyewalls, which is arguably more destructive. There is even the possibility that the hurricane stalls over Grand Bahama. Storm surges of up t0 20′ is a real possibility, and most parts of those islands are below that elevation. Winds of category 5 strength are a certainty, which are capable of causing total and complete destruction, especially given that the infrastructure on those islands is not very advanced. Because of the slow motion as well, heavy flooding rains will fall all across those islands, with totals above 25″ a probability. The slow movement as a whole means that these catastrophic conditions will only persist for longer, resulting in more damage. Even further south in the Bahamas, islands such as Eleuthera, New Providence, and northern Andros Islands could see dangerous conditions from Dorian, although not quite as severe as seen further north.

12z HWRF solution for Dorian, showing a very slow movement through the Bahamas before curving north on Tuesday morning. (WeatherNerds.org)

After this point, the hurricane should curve north near Grand Bahama on Tuesday morning as the trough starts to pick it up to its north. Confidence has increased that it will remain offshore Florida, however, impacts on the peninsula are all but certain. Just because the hurricane remains offshore does not mean that impacts stay with it as well. Hurricanes are not points on a map, but rather, they are large sprawling storms. As a result, tropical storm or even hurricane conditions are possible along the east coast of the peninsula, although the hurricane itself will be weakening as it tracks north. Tropical Storm Warnings and Hurricane Watches are in effect across the central east coast of Florida. Storm surge is likely up and down the peninsula up to 5′, which could increase depending on how close it tracks to the coast. Rainfall totals across the coastline could max out around 6″+ in some regions, especially further north along the coast. By Wednesday, the storm should be located offshore of Georgia, where similar conditions should be expected, although the storm may be slightly further offshore and will be weakening to category 2 or 3 strength. Impacts in Georgia will be more dependent on how close the storm tracks to the coast, given that the slight westerly component to the northward movement should stop once it reaches the latitude of Jacksonville, Florida.

[Image of probabilities of 34-kt winds]
Probability of Gale Force winds, with portions of central east Florida having a >90% chance of seeing tropical storm force winds despite the core being well offshore. (NHC)

As Dorian progresses further north towards the Carolinas, it will start to curve towards the northeast as another trough dips through the Midwest. This will cause most of the heavy weather associated with the storm to shift towards the northern half, which will push most of the heavy rainfall over land. The storm size will also inflate as it progresses poleward. As a result, the rainfall and flood threat is higher across the Carolinas and southeastern Virginia. While the model does indicate a brief landfall in North Carolina, that serves more as a technicality rather than being entirely crucial. By early Thursday, Dorian should be tracking offshore South Carolina and bringing heavy rains, storm surge, and high winds mainly to coastal areas. Impacts will be felt further inland in North Carolina, where a landfall would be most likely late Thursday. Because of this, the heavy rainfall should shift further inland as far west as Raleigh. Expected rainfall totals as of now peak around 10″ in coastal areas, but a further inland track would bring the maximum rainfall farther inland. These heavy rains can cause flash flooding in areas heavily impacted by flooding from Hurricane Florence one year ago. Further northeast, portions of Virginia, Maryland, and Delaware may also see impacts from the storm, although likely not as severe as further south.

12z GFS precip accumulation, showing a large area of high rainfal totals across the eastern Carolinas and Virginia. (College of DuPage models)

As for areas farther northeast, such as New England and Atlantic Canada, impacts are also likely from Dorian, although confidence is lower that far out given that they won’t start being felt for another 5+ days. Stay vigilant to the forecast, as impacts could be felt for some of these areas as well. While the hurricane will be weaker, the storm will be larger and possibly undergoing extratropical transition, so rough seas, high winds, and heavy rains are all possible, so stay tuned to the forecast.

NHC 5 day forecast for Hurricane Dorian, with the forecast track remaining mostly offshore, but impacts will not remain offshore.

There are other, much less significant systems active in the Atlantic. Closest to land is an area of disturbed weather north of the Yucatan Peninsula that has a 30% chance of development as it progresses west towards the coast of Mexico. The system remains broad and will take time to consolidate, but it will likely deliver heavy rains to coastal Tamaulipas in Mexico. Another disturbance also has a 30% chance of forming in 5 days to the southeast of Bermuda, but it should recurve east of the island and not be much of an issue. The system with the highest chance of development is Invest 91L, a tropical wave south of the Cabo Verde Islands with a high, 70%, chance of formation. Models show it tracking northwest into the open Atlantic, developing sometime during the middle of the week. Fortunately, no land areas should be effected by this as it tracks out into the open ocean away from land. The peak of the hurricane season is now only 9 days away.

NHC 5 day Tropical Weather Outlook, showing Hurricane Dorian, Invest 91L, and the other 2 disturbances.

Dorian remains a catastrophic hurricane as it pummels the Bahamas. Keep them in your thoughts and prayers as the storm has already been devastating for those islands. Stay tuned to your local officials, news outlets for the latest and most important information for your specific location. Preparations should be rushed to completion in Florida, and watches may be needed for Georgia and the Carolinas as early as tomorrow. Another article will be published either tomorrow or Tuesday retaining to Dorian and all things tropics. Stay safe, everyone.

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