Matt Lanza

Dorian still lashing the northern Bahamas, still a category 5 storm

Note: This post will cover Hurricane Dorian, which presents no threat to Texas, but which we are covering due to general public interest. For Houston, there are no tropical threats for the foreseeable future. It just looks very hot with diminishing rain chances over the coming days. Our normal posts will resume tomorrow.

Hurricane Dorian has unleashed utter fury on the northern Bahamas over the last 24 hours. Great Abaco and Marsh Harbour took a direct hit yesterday while Dorian was at its peak intensity. Grand Bahama Island was hit directly overnight, and the storm’s forward motion has slowed to approximately 1 mph with the center about 30 miles northeast of Freeport.

Dorian is expected to gradually weaken a bit through the day today, though it will remain an exceptionally dangerous storm, likely of at least category 4 intensity. We are seeing signs of a possible eyewall replacement cycle underway though, which should allow the storm’s maximum winds to weaken, while the size of the wind field expands a bit. Dorian will fluctuate in intensity over the next day or two before beginning a more steady weakening trend as it lifts north later in the week.

Where is Dorian going?

Dorian’s official track forecast keeps some portion of the Florida coast in the cone, but the storm is still expected to track just offshore. (National Hurricane Center)

That remains a tricky question, but the good news if you live in Florida is that everything is basically happening the way it was expected to happen in terms of track as of this morning. Anytime a storm slows to 1 mph, there is some inherent uncertainty in the details of a track forecast. But weather modeling is almost entirely on board with a track very similar to Hurricane Matthew in 2016, as it moves up the coast just offshore of Florida, Georgia, and the Carolinas.

Dorian will be a close call in Florida and up the coast, but the vast majority of data keeps the center just offshore. (Weathernerds.org)

The latest European ensemble forecast from overnight is shown above. Again, this is just the European model run 51 different times with some tweaks in initial conditions to give a better idea of goalposts in the forecast. A few things to note. First, of the 51 ensemble members, there are still around 8 to 10 that bring the center onshore near Cape Canaveral or just south of there. While the odds aren’t high, they aren’t zero, so folks in Florida still need to be prepared. Even assuming the track stays 25 to 50 miles offshore as expected, that will still be close enough to deliver strong winds, surge, and plentiful beach erosion to the entire coast. Remember, Matthew took a similar track, and although no two storms are alike, it underscores that severe impacts can still occur without a landfall. The Florida coast will need to hunker down tomorrow through Wednesday.

As Dorian treks northward, finding its way between the high pressure over Texas and the one in the Atlantic, it will begin to accelerate. Again, this will be close to the coasts of Georgia and South Carolina, though probably still offshore. As it passes North Carolina, there will be some chance of a landfall near Cape Fear or Cape Hatteras as the storm passes. Folks in the Carolinas and Georgia should prepare for significant coastal impacts, as well as heavy rain. Again, as we saw during Matthew in these areas, significant impacts can still occur far from the actual center.

Dorian should finally exit at the end of this week, and hopefully we see no more threats to land masses for a bit.

Category 4 Dorian threatens much of the Southeast coast

Hurricane Dorian exploded into a category 4 monster hurricane overnight, and it will next torment the northern Bahamas. From there, it will drift a bit more and then turn north, but exactly where that turn occurs will determine how severe the impacts are for Florida, as well as perhaps for areas farther up the coast. Let’s walk through things.

Now

One look at a satellite loop of Dorian tells you all you need to know about the storm in its present state.

Dorian is nearly a textbook major hurricane as it meanders its way toward the Bahamas. (Tropical Tidbits)

Dorian is menacing, with maximum sustained winds of 150 mph, making it a strong category 4 hurricane on the Saffir-Simpson scale. Over the next 2 to 3 days, Dorian will likely fluctuate in intensity.. But in general, expect it to remain at least a category 3, major storm. It’s not impossible to think Dorian could briefly attain category 5 status at some point. But typically, when storms get this strong, there are various ups and downs in intensification periods that are challenging to predict.

Dorian’s track

In 2016, Hurricane Matthew approached the Florida coast from the southeast. It brushed the coast but never made landfall in Florida, yet it was still a billion dollar storm for the state. In 2017, Irma approached the Keys from the southeast, while it was expected to make a sharp turn north. In that instance, 25 to 50 miles difference in where that turn occurred would mean huge differences in impacts for the entirety of the Florida Peninsula. It did approximately $50 billion in damage in what was not even close to a worst case scenario for the state. And now we have Dorian, which has been threatening a direct hit on Florida, but that has been contingent on the exact timing of a turn to the north. Multitudes of options, including a track into the Gulf or a right turn out to sea have been viable scenarios. The trend today has continued to shift toward more of a Matthew-type “brush,” as Eric discussed yesterday.

Dorian is moving west, as you see from the satellite image above. The latest NHC forecast implies that Dorian will approach the Florida coast and then turn north.

The National Hurricane Center predicts Dorian will turn north either along the coastline and just inland or just offshore. All areas in the cone should prepare for potential hurricane impacts. (NOAA)

We say it ad nauseam, but we really mean it: Do not focus on the implied track of the center here. Focus on the cone. The future track of Dorian will be contingent on the exact strength and orientation of high pressure to its north, as well as the trajectory, strength, and orientation of an upper atmospheric disturbance (trough) in the Midwest and East next week. These are all things that can change subtly in the hours and days ahead, forcing Dorian to track a few miles in one direction or another. Any shift in those expectations would have significant impacts on what conditions are experienced on the coast.

In fact, if you look at the latest spread of European ensemble members from last night’s run, you can see a wide dispersion of possible tracks.

Each line represents a possible track of Dorian’s center (impacts will extend well away from the center) over the next 6 days. While most solutions stay offshore, it’s still a very, very close call. (Weathernerds.org)

Yes, only a handful of members track the storm across Florida now. It’s not the favored outcome, but it remains a possible outcome. Again, this is why we urge folks to focus on the cone.

So Dorian should turn north after hammering the northern Bahamas. The turn north should occur either along the Florida coast or 50-100 miles offshore. Coastal impacts will still be significant, even in a miss. Dorian will generally track slowly north before eventually turning toward the northeast. Again, timing matters here because the Carolinas are in the way. It’s plausible that Dorian makes it far enough west to eventually make a landfall in South or North Carolina. We have a few extra days to iron that out. As Dorian moves north, it should slowly weaken a bit as well.

Regardless of landfall or no landfall, Dorian promises a few things: Rough surf, coastal flooding, potential surge, and beach erosion for the coast from Florida through at least North Carolina. Also, Dorian should bring a healthy amount of rainfall.

Dorian will be another big rainmaker for the coastal Southeast, with 6 to 10 inches of rain along the coast likely. (NOAA)

Rain totals should be about 6 to 10 inches along the coast from West Palm Beach to Cape Hatteras. Higher amounts are possible, and rain could extend farther inland in the Carolinas as well. Conversely, if Dorian does track farther offshore, closer to the right edge of the current forecast cone, these rain totals will be a good bit lower. But the most probable scenario right now suggests heavy rain along the coast.

Barring any significant changes today, we will update you again tomorrow morning.

Lastly, the National Hurricane Center is also assigning about a 20 percent risk of development in the southern Gulf from the disturbance we’ve discussed all week here on the blog.

There is low risk for a system to organize in the southern Gulf, but it should stay south of Texas and well south of Houston, preventing any impacts here. (NOAA)

That is currently likely to travel toward Mexico, and it is unlikely to develop significantly. We should not see any impacts in Houston from this system. There are other systems likely to develop in the far east Atlantic off Africa next week, but none of those looks like a serious concern at this time. The Gulf is expected to turn quieter for a stretch beginning later next week.

Rain chances fizzle this weekend in Houston, as Dorian creeps toward Florida

We saw a few showers in the area on Thursday, but for the most part it was a much calmer day than Wednesday. Some folks in our area have been bypassed by these showers more often than not lately, and it’s beginning to add up across much of Texas.

Drought is beginning to expand across much of the state of Texas. (U.S. Drought Monitor)

The latest drought update released on Thursday shows about 75 percent of Texas in abnormally dry or drought conditions. In the Houston area, as Eric so aptly described on Thursday, we’ve been playing “rainfall roulette” lately. Fort Bend County? Abnormally dry. Brazos Valley? Abnormally dry or in drought. Across Houston and southeast, it’s been almost comical, with Hobby Airport about 2 inches above normal this month thanks mostly to one big storm on August 19th. Galveston, meanwhile, is almost 2 inches below average for the month. IAH Airport? About an inch below normal.

Over the next couple days it would seem that just a few of us will see downpours, while many will stay dry, so drought will continue as an emerging storyline into September.

Today

Look for a typical summer day today: Sun, clouds, hot, and scattered hit or miss downpours. Rain will be mostly near the coast in the morning, especially toward Matagorda Bay. Showers should migrate inland for a lucky handful of communities in the afternoon. We should reach the mid-90s this afternoon, though it will feel 5 to 10 degrees hotter than that.

Weekend

Both Saturday and Sunday look partly to mostly sunny and hot. Morning lows will start off in the mid- to upper-70s, while daytime highs should easily peak in the mid-90s. Rain chances? The better chance is on Saturday, but even that will just be a handful of isolated showers. I would anticipate a mostly dry weekend.

See full post

Wednesday evening tropics update: Hurricane Dorian to threaten Florida this weekend

Quick local note: Strong to severe thunderstorms are racing through the Houston metro as of 5:30 PM. We expect these to drop south and east through 7 to 8 PM, bringing much of Houston a burst of heavy rain yielding perhaps 1 to 2 inches, as well as gusty winds. Areas south and east of Houston are likely to see some heavy rain from this as well. Areas north and west of Houston are mostly done with storms now or should be soon. The storms should begin to diminish and shift offshore after sunset.

Radar at 5:30 PM showed miserable conditions for commuters leaving the Inner Loop. Storms will press south and east this evening. (RadarScope)

On to the tropics. Interest regarding Hurricane Dorian has spiked today as the track has shifted a bit and the upgrade to a hurricane occurred this afternoon. We’re here to walk you through what the future may have in store regarding Dorian.

One sentence summary

Hurricane Dorian is likely to impact the Florida Peninsula around Labor Day before heading into the eastern Gulf of Mexico where it could impact the eastern or central Gulf Coast next week, east of Texas, though there is still some degree of uncertainty.

Now

Dorian is located just northwest of St. Thomas in the U.S. Virgin Islands, as of the National Hurricane Center’s (NHC) 4 PM CDT advisory. Satellite shows a fairly healthy looking system that has managed to keep itself together in the face of adverse conditions around the storm.

Hurricane Dorian beginning to exit the Virgin Islands and Puerto Rico on Wednesday evening. (Weathernerds.org)

Dorian’s maximum sustained winds are 80 mph, and it’s currently moving to the northwest at 14 mph.

Through the holiday weekend

Dorian will take a cruise east of the Bahamas over the next couple days. As this occurs, high pressure over the Atlantic is going to begin building back to the west. This will force Dorian to begin to turn more to the west instead of northwest by the time we get to Friday night or Saturday.

High pressure building from near Bermuda west to the Southeast will force Dorian to turn west toward Florida over the weekend. (Pivotal Weather)

Around this time, forecast uncertainty begins to rapidly increase, unfortunately. The most likely scenario right now indicates that Dorian will remain on a westward heading toward the Florida Peninsula. Whether that’s aimed toward Miami, West Palm, Vero, Melbourne, or somewhere else is contingent on when Dorian turns and how sharp of a turn it is. Thus, you have to assume that at this point, the entirety of the Florida Peninsula needs to monitor Dorian’s progress, and they are all in the cone of uncertainty still.

The NHC forecast for Dorian shows a major hurricane approaching somewhere along the Florida Peninsula on Labor Day. (NOAA)

If you are planning a Labor Day weekend trip anywhere on the Florida Peninsula, you must be aware of this storm and that there is an increasing chance of some kind of impact beginning later Sunday or Labor Day Monday. We can’t tell you specifically what to do, but it’s a scenario you need to be aware of.

Beyond Labor Day

Uncertainty roofs beyond Monday regarding Dorian’s track. Much will depend on what’s happening over the Plains, how strong a trough of low pressure is across the Midwest and Mid-Atlantic, and ultimately how much the high pressure ridge over the Atlantic wants to build back to the west. This means numerous scenarios involving Dorian are in play.

The most likely scenario at this point, or at least the one favored by most weather models and ensemble members involves Dorian moving into the eastern Gulf of Mexico and then gradually turning to the northwest and north toward the central or eastern portions of the Gulf Coast. While we continue to believe this will not ultimately be a concern for Texas, we should continue to monitor Dorian’s progress through the weekend, especially given the high degree of uncertainty that exists right now. We will gradually gain some color on this tomorrow and Friday and can hopefully completely rule out certain possibilities for us here.

The bottom line on Dorian:

  • The odds of a major hurricane impacting Florida around Labor Day have increased significantly today.
  • There is still a high amount of uncertainty on track and exact timing of impacts, and folks from Louisiana through the Carolinas should be watching Dorian closely. In Texas, for now, we should just be checking in once a day to make sure we’re still in the clear.
  • If you have travel plans to the Florida Peninsula for the holiday weekend, it’s critical you remain tuned in and aware of this storm.
  • Besides major hurricane impacts in the region wherever the storm hits, extremely heavy rainfall will be possible over Florida and the eastern Gulf Coast or Southeast early to mid-next week.

That other Gulf system

Eric this morning noted the other feature we’re watching: A disturbance near Cuba. We expect that to arrive in the southern Gulf of Mexico this weekend. Weather modeling this afternoon continued to keep that pointed mostly well to our south and either into far south Texas or Mexico by midweek next week. Most also did not suggest it would strengthen a whole lot. Still, given the uncertainty surrounding Dorian and any potential interplay between Dorian and that disturbance (the systems won’t merge, but one could impact the other depending on location and intensity), we are going to continue to watch this one. The disturbance could also become a significant rainmaker for parts of South Texas or Mexico.

The good news is that after these two systems run their course, conditions look quiet in the Gulf again for a little while. More from Eric on Thursday morning.