Houston residents have started to see rain bands from Hurricane Harvey move onshore today. Unfortunately, this is but a taste of what awaits the city—and the entire Texas coast from south of Corpus Christi through the Beaumont area, as well as inland counties—for several days to come. I’d love nothing more than to write a post expressing some optimism about the rainfall forecast ahead, but as of now it looks really quite grim. So let’s get to it.

Harvey has intensified this afternoon, reaching 120-mph sustained winds and Category 3 status. It should come ashore the central Texas coast near Port Aransas on Saturday morning, by or before sunrise. The storm is going pack a major wallop in terms of both wind and storm surge. Residents in the area should have completed their preparations and evacuated, because conditions are starting to deteriorate. It is a life-threatening situation for people who have remained behind in low-lying areas between Corpus Christi and Matagorda.

Beyond Harvey’s landfall the situation remains a mess. An absolute mess. Last night we talked about three different scenarios for Harvey’s movement, post-landfall. And honestly, all three of them remain in play. The most important thing to understand is that our confidence in Harvey’s post-landfall track remains very low. Unfortunately the most likely scenario now is that Harvey isn’t going anywhere, any time soon. Therefore, we can say with high confidence that Harvey will produce a [googles a synonym for ‘sh–load’] large amount of rainfall over Texas.

Expect floods. Lots of flooding.

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If you’ve read this site carefully over the last 24 hours, you’ll recall that I’ve been discussing a scenario I’m calling the “Euro special.” (See, for example, here and here). Under this scenario, Harvey makes landfall along the central Texas coast, dithers around for a day or two, and then moves eastward, back over the Gulf of Mexico. During its latest run the GFS model latched onto this scenario, bringing Harvey back into the Gulf, before the system eventually moves north-northeast toward Houston or Beaumont, getting drawn toward a trough of low pressure in the Midwestern United States.

As of their most recent update, the professional hurricane forecasters at the National Hurricane Center have bought into this scenario, with some caution. “At this time it is too early to say whether the center will definitely re-emerge over the northwestern Gulf of Mexico,” Robbie Berg wrote in the 10am discussion. Here’s the track they went with:

Some thoughts

Such a track raises a number of unpleasant possibilities. In the interest of a free and frank discussion, you’ll have to indulge some speculation with this post. But this is a mature audience that seems to appreciate honesty. So here goes.

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Good morning, everyone. After an overnight lull in strengthening, perhaps caused by some dry air working its way into the circulation of Hurricane Harvey, the storm has begun intensifying again. As of 6am CT it had sustained winds of 110 mph, but with the central pressure continuing to fall, the storm’s winds will almost certainly increase. For Texas, there will be two epochs of Harvey: the catastrophic effects from wind and surge during the next day or so for the central Texas coast, and the unfolding, widespread, major flood event from Saturday through the middle of next week for a large swath of the state, including Houston. We will discuss both this morning.

Wind and Surge

We remain confident in the forecast track for Harvey during the next 24 hours, as it moves northwest across the Gulf of Mexico, and comes ashore somewhere near Port Aransas. If you live in, or have property from Rockport to Matagorda, preparations for devastating winds—probably about 120 mph sustained, but maybe higher—should be completed by early this afternoon.

Storm surge will be a major problem for low-lying coastal areas. According to the latest National Hurricane Center storm surge forecast, the following numbers represent the realistic “worst case” inundation. This means the depth of water above the ground. You can visit the site itself to zoom in to any location along the Texas coast.

• Mustang Island to Sargent, including Matagorda Bay: 6-12 feet
• Sargent to Jamaica Beach: 5-8 ft
• Jamaica Beach to High Island: 2-4 ft
• Galveston Bay (Seabrook, Shoreacres, Nassau Bay, Kemah, San Leon) 2-4 ft

For Houston, aside from the above surge numbers, the effects from the immediate landfall of Hurricane Harvey will be relatively modest. As we’ve discussed, winds Friday night and Saturday morning should be manageable, although some areas may briefly see some tropical storm-force winds. The power grid is designed to withstand these conditions—so hopefully most of us will keep the lights on.

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