Eric Berger

One sentence summary

Franklin has intensified into a major hurricane, with 130 mph sustained winds, overnight; but the bigger threat to land is Tropical Storm Idalia, which could become a major hurricane before striking Florida’s Gulf coast later this week.

Tropical Storm Idalia

We’re going to start with Idalia, because that poses by far the biggest threat. As of this morning, Idalia is nearing hurricane status with 65 mph winds, and it will probably reach that milestone later today. Unfortunately, it is likely to strengthen further over the next two days as it crosses over Gulf of Mexico waters that are extremely warm and, critically, moves into an upper atmosphere that should not significantly hamper intensification. For now, the National Hurricane Center forecasts that Idalia will become a Category 3 hurricane prior to landfall, but the storm could easily be a category stronger or weaker by Tuesday night as it nears the Florida coast. The one saving grace here is that Idalia will only have a little more than 24 hours over the open Gulf of Mexico waters to strengthen, and some modest wind shear may limit its ceiling.

So where will Idalia go?

Later today the storm will cross the far Western edge of Cuba, and then move into the Southeastern Gulf of Mexico. After that it will move north-northeast, toward Florida. Our best forecast models are increasing in confidence, but there’s still some uncertainty in where Idalia’s most devastating winds and storm surge will go. The most likely area for landfall is the Big Bend area of the Florida coast, but a landfall from Panama City down to Tampa remains possible. The populated area of Tampa is on the right side of the storm, susceptible to the strongest winds and storm surge. However, based upon our best forecasts right now, the Tampa region would miss out on Idalia’s worst. But it’s going to be close.

Hurricanes produce three major threats: inland rainfall, storm surge, and damaging winds. In Idalia’s case, inland rainfall is slightly less of a concern because the storm is expected to maintain a reasonably high forward motion on Tuesday and Wednesday, as it crosses Florida and Georgia. That is not to say there will not be inland flooding from Idalia, particularly in areas such as Georgia and the Carolinas, but it should be mitigated by forward speed.

So the bigger issues are likely to be storm surge and damaging winds. Both of these effects will be most intense along the line of the storm’s track, and to its right-hand side. We can see this in the forecast “wind gust swath” from the European model. Now this is just one model run, and most definitely subject to change, but it gives you a sense of how the worst of the winds will be relatively localized, near the core of of the storm. Wind gusts of up to 130 mph are possible, based on this forecast.

As for storm surge, this again will depend on the track’s location. For now the worst of it looks to occur in the Big Bend area of the Florida coast.

We will have an update on Idalia later today. The bottom line is that if you live in Florida, including the Tampa area, today is the last full day to make preparations for the impending storm. This is a storm to be taken seriously. Tropical Storm-force winds could arrive in parts of the state as early as the middle of the day on Tuesday.

Major Hurricane Franklin

Franklin has continued to strengthen overnight, and as of 7:35 am ET this morning the National Hurricane Center reported that the storm had reached sustained winds of 130 mph. Some further strengthening is likely later today as Franklin continues passing over warm waters and enjoys low wind shear.

Fortunately—very fortunately—Franklin is behaving for a storm in the Western Atlantic Ocean. Its projected track will follow a course far enough off the Atlantic seaboard of the United States to spare the coast of any significant effects. Moreover, Franklin should remain just far enough west and north of Bermuda to also spare the small island of its worst effects. Some tropical storm warnings may still be necessary for Bermuda, but it should be miss out on anything close to the worst of what the Atlantic season’s first major hurricane could dish out.

So go on Franklin, get on with your bad self.

What else is out there?

After Franklin and Idalia there is another system likely to develop from a tropical wave that will move off Africa on Tuesday. However, we don’t anticipate that this system will track toward the Caribbean Sea or the United States. It likely is not a concern as we head into early September.

One-sentence summary

There are several tropical systems to track but the most intriguing area to focus on lies in the Gulf of Mexico, where a tropical wave may bring beneficial rains to some lucky area early next week.

Happening now: Three waves to watch

Let’s start out with this morning’s tropical weather outlook from the National Hurricane Center. These are published every six hours during the Atlantic hurricane season, and provide a good overview of where the experts at the Miami-based center expect action over the next seven days.

Those orange-blob tropical disturbances in the eastern Atlantic are certainly eye-catching, and this is definitely the time of year when we start to worry about waves moving off of Africa, and traversing the Atlantic Ocean to threaten the United States, Caribbean islands, and Mexico. But I don’t think we’re going to have to worry too much about either of these waves.

The easternmost disturbance has a 40 percent chance of developing, the hurricane center says. I say have at it, because this system is very likely to get pulled northward into the central Atlantic Ocean. The system probably has about five days to become something before conditions become marginal to sustain a tropical storm or hurricane. So a fish storm, maybe.

The closer tropical wave has a 50 percent chance of developing, according to the hurricane center. As Matt noted yesterday, if the wave tracks more westward than northwestward, it will eventually run into some drier air as it approaches the Caribbean. Still, given its potential to get closer to the Caribbean islands, this is a wave probably worth watching a little more closely over the next week. Fortunately, it faces an uphill climb to become anything of note.

The medium range (days 6 to 10): The Gulf wave

Finally, the National Hurricane Center has highlighted a tropical wave forming in the Gulf of Mexico next week, giving it a 20 percent chance of developing. The Gulf is blazing hot, and the old adage I always stick to is that you never want to see a low pressure system there in August or September. However, in this case there are a lot of factors working against the tropical low, including its fairly rapid forward speed. So there are probably a fair number of Gulf coast residents eying the tropical system as a potential salve to drought conditions. Texas, in particular, could use a good soaking.

Whether that happens is going to depend on a rather stout high pressure system over the Central United States. The map below shows a rather intense high developing over Iowa, Missouri, Nebraska and Kansas next week. If the high is too strong, it will force the Gulf system south of the Upper Texas coast and Louisiana. If the high is further south than that, then again, it will force the wave south, toward South Texas. If the high is weaker or further north, it would allow the wave to come to the Upper Texas coast or Louisiana.

Beyond the Gulf wave, and the two aforementioned systems in the Eastern Atlantic Ocean, there’s not too much else to track in the medium-term.

Fantasyland (beyond day 10): No more Mr. Nice Gyre

There is also not much to grab on to in the models right now as we get toward the final few days of August. I do think there’s the potential for some action in the Western Caribbean Sea about 10 days from now, probably related to the Central American Gyre, which is basically a broad monsoonal low-pressure system over Central America. (A more detailed discussion can be found here). There’s no specific threat to point to, but it is not out of the realm of possibility that a tropical low could develop here and lift north into the Gulf of Mexico by late August. As this is super speculative, it’s not something I’m losing sleep about.

Nor should you.

One-sentence summary

There is some sporadic tropical wave activity out there in the Atlantic right now, but nothing worth getting too worked up about—but next week, maybe?

Happening now: Not a whole lot

This morning’s satellite snapshot of the Main Development Region for tropical systems, between Africa and the Caribbean Sea, shows some waves dinking and dunking along. But there’s just not much that’s too impressive out there. And anything that gets too frisky is likely to get sliced up like sushi due to fairly high wind shear levels across much of the basin.

I would expect this pattern to persist for the rest of this week.

The medium range (days 6 to 10): Some tropical-ish near Cuba?

The medium-term is a little bit more interesting. Various ensemble members of the European model, in particular, seem to latch on to a low pressure system in the northwestern Caribbean Sea this weekend, and drag a weak low pressure system into the Gulf of Mexico next week. I’m not bullish on development, but if anything does it probably would be driven westward into Mexico due to the persistent high pressure over Texas.

The models are also latching onto a tropical wave that will probably emerge off the coast of Africa this weekend, and suggesting it may have some chance of developing in a week to 10 days over the open Atlantic Ocean. That’s certainly possible, and something we’ll perhaps be discussing in the coming days. We shall see. For now, there’s not much more to say.

Fantasyland (beyond day 10): All eyes on the Main Development Region

The main take-away is that, overall, we’re in a good position heading into mid-August. There are no signs of the tropical Atlantic imminently lighting up like a Christmas tree. That doesn’t mean it won’t happen, but there are no signs that it will. Which is great.

The other thing to say is that our focus, increasingly, is going to be on the Main Development Region, and new tropical waves emerging off of Africa. This wave train typically becomes much more prominent during the final weeks of August and, of course, throughout September.