Heavy rains continue along the coast; assessing tropical threats

Anniversary Awareness: Ten years ago today we were watching the approach of Hurricane Ike, whose winds and storm surge pushed into Galveston on Friday, Sept. 12. I recall this time vividly, as I tried to grab a few hours of sleep in a darkened room in the Houston Chronicle‘s former downtown newsroom. Next door, at the Lancaster Hotel, a window blew out in my family’s room. I was powerless to help. Similar dramas played out across the region as the storm made a final landfall at 2:10am CT on Saturday morning. At the time, Ike ranked as the second costliest hurricane in U.S. history, behind only Katrina. It has since been bumped down to sixth, supplanted by Harvey, Maria, Sandy, and Irma. Unfortunately, the Houston region has yet to heed the lessons of Ike and enact any kind of surge barrier that would protect communities along Galveston Bay, expensive infrastructure along the Houston Ship Channel, or Galveston Island. The region remains highly vulnerable to a major storm surge event. On a personal note, a lot of the lessons I learned while covering Ike have made this site what it is today.

This house, in Gilchrist, remains standing after Hurricane Ike. Strong building codes matter. (Wikimedia)

And now, the forecast. We’ll break this down into three parts: Rainfall potential for Wednesday and Thursday, Invest 95L and this weekend’s weather, and finally, a tropics update on the terribly threatening Hurricane Florence and, for now, a fading Tropical Storm Isaac.

Wednesday and Thursday

As anticipated, rain showers developed offshore early Wednesday morning and have begun moving inland into Matagorda, Brazoria, and Galveston counties. Although these storms are less intense and widespread that rains on Tuesday morning, they are nonetheless hitting some of the areas most affected by the earlier rains. Caution is urged on roadways in coastal counties and a Flash Flood Warning is in effect until 8:30 am CT. This pattern will likely more or less continue, with coastal areas picking up an additional 1-3 inches on Wednesday and Thursday, with higher isolated totals. Inland rainfall totals should, for the most part, be significantly less than this.

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Tropics sizzling, but Houston threats seem manageable. Probably.

A solid round of showers and thunderstorms rolled through Houston on Monday during the daytime, dropping 0.5 to 2.0 inches of rain for most of the area. It now seems likely that the radar will quiet down for most of this evening, before heavier showers being to develop along the coast on Tuesday morning like on Monday morning. The National Weather Service has prudently kept a Flash Flood Watch in place for coastal counties, and the inland tier including Harris County, through noon Tuesday (Note: after this post was published Monday afternoon, the flood watch was extended until 6pm CT Tuesday. Our forecast remains unchanged.) The best hope is that the heaviest precipitation stays just offshore, rather than migrating on shore during the next 24 hours or so.

Area of flash flood watch. (National Weather Service)

Unfortunately, rain chances are not going to go away on Wednesday and Thursday. Although rain showers should be more scattered in nature, and perhaps less intense, we definitely can’t rule out locally heavy rainfall due to the tropical air mass and overall stagnant pattern. Given all of this, we expect accumulations of 1 to 3 inches for inland areas from now through Thursday, with 2 to 5 inches more likely for areas immediately along the coast (with higher isolated totals). The primary threat should be street flooding rather than significant stream and bayou flooding.

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Between rain and the tropics, Houston’s weather will be pretty lousy

Man, I hate this time of year. Invariably, the tropics reach their crescendo, and this year is no different. In fact, this is only the 11th time on record that three hurricanes have been active in the Atlantic simultaneously, Florence, Helene, and Isaac. This week, Hurricane Florence will rightly suck up a lot of the national oxygen—Matt did a commendable job of summarizing the risks to the Carolinas and beyond, and they are tremendous in terms of flooding, wind, and surge—but we have some homegrown threats to consider as well.

Tropics as of 7am CT on Monday. (National Hurricane Center)

For this post we are going to focus on the near-term threat of heavy rainfall on Monday and Tuesday, and then the late-week threat from a nascent tropical system. Did I mention that I hate this time of year?

Monday and Tuesday flood watch

The National Weather Service has issued a Flash Flood Watch for the coastal and inland tier of counties for 1pm Monday through Tuesday morning, and they admit they may have to extend it. Basically, we have a lot of low pressure hanging around and a super-moist atmosphere. I think at best we can hope for scattered, heavy rain showers; and at worst we probably will see some spots of 3 to 6 inches over the next two days. Most likely the hardest hit areas will be along the coast, and if we’re lucky the heaviest rains will fall offshore.

Area of flash flood warning in effect through Tuesday morning. (National Weather Service)

Both Monday, Monday night, and Tuesday will probably be similar in this regard. We’ll just have to watch radar trends and if you have to drive for more than a short errand, you should probably check road conditions at your destination. This shouldn’t be anything more than street flooding, but we can’t guarantee that.

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Another wet weekend in store for Houston

Houston will have another day of somewhat drier weather before a wetter pattern returns to the region through Monday. Yes, another soggy weekend. Sorry about that. Also, while we’re on the subject of bad news, if you’re wondering when fall’s first front might arrive, I’m afraid there just aren’t any really strong signals for that right now. I would not anticipate it coming before around Sept. 20, if then.

Thursday

The region should see some partly sunny skies today, so enjoy the sunshine while you can. Some isolated to scattered showers will be possible, but for the most part it should be a dry day. More sunshine will mean higher temperatures, so we can probably expect low 90s for most of Houston, with a smattering of mid-90s possible.

Friday, Saturday, Sunday, and Monday

Unfortunately, the pattern for this weekend looks wet, with low pressure in place overhead and a plenty moist atmosphere. Effectively this means that most areas of Houston (50 to 70 percent) will see rain on most days from Friday through Monday. Although the forecast models aren’t forecasting any rain bombs at this time that might lead to some street flooding, with this kind of atmosphere during the summer months we can’t rule out some heavier showers that temporarily clog streets.

Temperatures, as usual, will depend upon the extent of cloud cover and rainfall. Look for a range from the mid-80s to lower-90s. Humidity, of course, is guaranteed.

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