Harvey inching closer to Houston

Quick note to lead: A Tornado Watch is posted for the entire area through 1 AM. We’ve just had numerous reports of confirmed tornadoes in northwest Harris County. We’ve had multiple other confirmed tornadoes since last night. While our focus remains on flooding, this tornado threat is a serious concern also. Make sure you have a weather radio or have the emergency notifications setting switched to “on” on your mobile device to get warnings for your location through tonight, as periodic tornadoes will be possible throughout the region.

Tropical Storm Harvey continues to explore Victoria and the Golden Crescent of Texas this evening. The center as of 5 PM was near Cuero in DeWitt County. Over the last several hours, Harvey has assumed a bit of an eastward drift. This has been fairly well captured on most weather models, and it’s why I think the most critical part of this storm’s legacy in Houston will play out over the next 18-24 hours. Let me explain.

Since about Wednesday or Thursday, it appeared that Harvey’s closest approach to Houston as a moderate tropical storm would be late tonight into Sunday before it drifted back west and south and further weakened. Though it would continue flinging periods of heavy rain our way, the core would be mostly out of the picture after tomorrow. Some of our shorter-term and highest resolution weather models are suggesting that Harvey’s center drifts a little closer to Houston tonight, bringing some of that core to the western part of the city, while continued onshore flow of moisture helps new rain and storms to form.

This would mean a major uptick in rainfall across much of the Houston area tonight. We’ve been fortunate so far for the most part. Bayous have filled, streets have flooded, but much of it has been manageable by our fairly rigorous rainfall standards here in Houston.

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The big question: Where will Harvey and its rains go?

This afternoon’s post will focus on now-Tropical Storm Harvey’s inland track. Where the center goes from here is going to make a big difference in terms of whether Houston sees widespread flooding—or not. Unfortunately, the track forecast has remained something of a mess.

But before that discussion, just a quick update on the state of rains in Houston. The heavy band we were concerned about this morning has slowly moved north-northeast of the central Houston area, and this has allowed the city and its bayous to dry out a bit. This is good, because we expect more rain bands to move into the area later today and especially tonight. For now travel is mostly safe, but try to stay off the roads unless you really need to go out, and complete any trips before dark. Also, if you’re wandering around outside, be careful of wildlife. It, too, is looking for shelter from rising waters.

Look what we found in League City, near Clear Creek, this afternoon. (Space City Weather)

Harvey’s track

The big question is where Harvey’s center (and its outer rain bands) will go over the next few days. While 10 to 15 inches over three or four days is a lot of rain, for most of Houston it is manageable. However, 20 inches or more will cause widespread problems.

What I think I know today is that there’s a chance the Houston region escapes catastrophic flooding. I feel better than I did yesterday at this time, when the forecast was almost completely grim. Let me explain why.

Both the GFS and European model runs have Harvey wobbling around south Texas, and the central-Texas coast today through Monday, and then they bring the center back out into the Gulf of Mexico near the point where it made landfall late Friday night. But neither model keeps it offshore for long, and at this time I don’t think significant re-intensification is a major threat. No, the long-term worry for Houston, the Texas coast, and much of southern and southeast Texas remains rainfall.

GFS ensemble model forecasts for Thursday morning. (Weather Bell/Space City Weather)

By Wednesday night and Thursday morning the GFS model ensemble solutions (shown above) start to diverge, with a slight majority dragging Harvey toward the Rio Grande and ultimately toward lower pressures over northern Mexico. This is a good scenario (Dying in the Rio) for Houston because it ultimately limits rainfall potential over the area. The remainder bring the storm north toward Houston (The Wandering 59 special). This results in more rainfall for Houston during the middle of next week, when we certainly will already be waterlogged.

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Harvey weakening, but sending its strongest rains into Houston

This post will provide a brief update on Hurricane Harvey’s official forecast track, and discuss what we’ve seen so far from the storm’s rains in Houston, and what to expect for the rest of the day. We’re still at the “manageable” stage in terms of rainfall, but it won’t take too much to push us into unmanageable.

Harvey

In its 10am CT update, the National Hurricane Center says Harvey remains a hurricane—but only barely so with 75mph winds. It is weakening, but in the process it has thrashed the central Texas coast, from Corpus Christi to Freeport, and inland areas such as Victoria for most of the last day.

From here on out, the official forecast track is basically summarized as follows: ¯\_(ツ)_/¯

Official National Hurricane Center track forecast at 10am CT on Saturday.

In their discussion, forecasters at the hurricane center wrote, “Based on this pattern, Harvey could easily meander for the next 4 to 5 days over southeast Texas as indicated in the NHC forecast. The only agreement among the track guidance is that Harvey is certainly not going anywhere fast.”

We discussed several scenarios for Harvey’s evolution in a post last night, and that thinking more or less holds up (here the National Hurricane Center is following “The Wandering 59 special”) But theirs is, frankly, a low-confidence track forecast. We will provide a comprehensive update on what we can say about Harvey’s track, and its implications for Texas rainfall early next week, by around 2pm CT today. Basically, our weather for Sunday and beyond depends on where Harvey goes.

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Saturday AM Harvey transitioning from hurricane to long rainstorm

Harvey has arrived in Houston.

Numerous flash flood warnings are posted right now across the Greater Houston area, as an eastern flank feeder band of the storm flows ashore.

Harvey slowly meandering between Victoria and Goliad, shipping intense rains into Houston. (College of DuPage)

 

These heavy rains are likely to continue throughout the day today. There may be lulls at times, but the dominant weather we see in Houston today is heavy rainfall, leading to street and possibly bayou flooding.

Rain totals have begun to add up. Generally 1-3″ north and east and 3-6″+ south and west since yesterday.

Rain totals through 6:45 AM Saturday are beginning to add up. (Harris County Flood Control)

 

As the day progresses, rain totals will balloon further. Some models show really impressive rain totals in the Houston area today. I would expect an average of 4-8″ today across the region, with higher amounts possible, especially on the south and west sides and perhaps a few spots east of the city with lesser amounts.

Bottom line in all this, you need to be prepared for significant travel inconvenience and disruption today. And if you can stay put, please do so.

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