Space City Weather

Well, they don’t call them natural disasters for nothing. For some residents, of course, last night was but a breezy affair. For others, especially along the coast, there is substantial wind and flood damage to contend with this morning from Hurricane Nicholas. And then there are the half a million customers in the greater Houston region without power this morning.

For those of you recovering today—and I count myself among you as power went out in my neighborhood, trees are down, my backyard flooded—it may not feel like it, but this storm could have been so so much worse. With this post I want to discuss that, but first lets update the status of Nicholas and present a short-term forecast.

Tropical Storm Nicholas

As of 10am CT, the center of Nicholas is very nearly directly over Houston, located just 10 miles southeast of downtown. As it has moved inland for nearly 10 hours, Nicholas has weakened to a storm with sustained winds of 45 mph. The storm is moving slowly, the northeast, at about 6 mph. It should continue to turn more easterly, and then dissipate over Louisiana in two or three days. The main rainfall threat has moved east, and the southern half of Louisiana could see 6 to 10 inches of rainfall over the next several days.

Short-term forecast

The forecast for today and Wednesday will allow for recovery in the greater Houston area. Some light, scattered showers will be possible today and Wednesday, but chances are fairly low and accumulations should be slight. The strongest winds, too, have moved east of the area despite the presence of Nicholas’ center.

If you’re without power, high temperatures today will be quite reasonable for this time of year, in the upper 70s. Humidity will be high, of course. Lows tonight will drop into the low 70s. Highs on Wednesday should reach the mid-80s with a mix of sunshine and clouds.

If you want a more hopeful thought, we’re seeing fairly strong hints in the models for a decently strong fall front moving into the region in nine or ten days time. That’s a long way out to forecast, so grain of salt and all that, but it is the right time of year for a front. So maybe, hopefully, fall is but 10 days away. I’m ready.

Nicholas could have been so much worse

First of all, if you can remember all the way back to Saturday, I presented three different scenarios for Nicholas’ track and eventual flooding in Houston. The first of these was the “Coast Hugger,” in which the storm remained close to the Gulf, brought 2 to 4 inches of rain to Houston and higher amounts along the coast, while keeping the heaviest rains offshore. This is largely what happened, with Nicholas remaining very close to the coast even after moving inland. If we look at satellite-derived precipitation totals for the last three days, the heaviest swath of 10-20 inches of rainfall came offshore.

A track even 40 or 50 miles further inland would have set up those heaviest rains directly across the Houston metro area, and created a much more serious flood situation. Hopefully this offers you some insight into the challenge of predicting these kinds of rain events. It was a very close call, a matter of miles, between significant inland rainfall flooding in Houston, and relatively clean bayous this morning.

The second factor is wind. Nicholas turned out to be a fairly nasty storm in terms of wind gusts, and pushed a larger storm surge—as high as 6.1 feet into Clear Lake—than predicted. This is a reminder of the power of a hurricane, even one that was “only” a minimal Category 1 storm. The truth is that the track of the storm was very nearly a worst-case one for Houston in terms of winds and putting a maximum storm surge across Galveston Island and into Galveston Bay.

It is September 14, the absolute peak of hurricane season in the Atlantic, and a time when sea surface temperatures in the Gulf of Mexico are at their warmest of the year. So this morning I’m thinking about what would have happened if we had not had some wind shear over the western Gulf of Mexico yesterday, or if Nicholas had been able to consolidate a more well defined and consistent center of circulation. It would have been much, much worse for all of us had a significantly stronger hurricane made landfall last night. So while we pick up the pieces this morning, realize Nicholas could have been much more of a terror.

Matt will have our next update—and probably our last update specific to Nicholas—at 5 pm CT today.

Good morning. A rollicking night across a healthy chunk of the Houston metro area continues this morning, as now-Tropical Storm Nicholas slowly, but steadily, passes through. As of 4:45 AM, Centerpoint’s website reports over 380,000 customers without power. Wind gusts of 45 to 55 mph are still occurring across southern and some eastern parts of the metro area, with gusts generally in the 30s to the north. The maps here shows the maximum wind gusts we’ve seen at various sites across the area since midnight.

You can see a list of highest reported wind gusts for the entirety of the storm (as of 5 A.M.) here. Judging by radar at 4:55 AM, Nicholas’s center was just getting ready to exit Brazoria County, just north of Rosharon. The center should pass very near or right over Houston a little later this morning. Maximum sustained winds were still reported to be 70 mph at the 4 A.M. National Hurricane Center advisory, though it’s likely to have weakened a bit further by now.

Wind impacts

As Nicholas continues to move north, you can expect gusty winds to travel north and east with the storm. Continued wind gusts of 45 to 55 mph are likely in the city of Houston and points south and east for another couple hours, with a general trend toward lessening wind overall. Areas north of Houston will likely see 35 to 45 mph gusts continue as well through the morning. This could continue to sporadically knock out power to folks across the area. If you have power, it would be a good idea to keep your phone charged, just in case you lose power. As winds subside a bit this afternoon, power crews should be able to get out to begin to repair damage. Power restoration may take somewhat longer where damage is more significant, namely along the coast and southeast of Houston. It would be a good idea to check in on anyone vulnerable, especially the elderly today, just to make sure they have what they need in case they’ve lost power.

Rainfall/Flooding

The good news in Houston is that serious flooding has not materialized in the city. The story is a bit different south and east of the city, however. The Harris County Flood Control maps of gauge status as of 5 A.M. shows several locations that are either flooding or close to flooding in far eastern Harris County and along Clear Creek or into Galveston and Brazoria Counties.

Some of the flooding south and east of Houston is coming as a result of surge on Galveston Bay. With the center of the storm over inland Brazoria County, winds have piled up water on the west side of the bay, leading to a generally 2 to 5 foot surge in many areas, highest along the bayshore in Harris or Galveston Counties.

Clear Lake even is close to a 6 foot surge. Expect these values to peak soon, with gradual improvement through the morning and into the afternoon.

Rainfall continues heavy at times, mainly in Houston and points east now. The circled area below is seeing rates at times over 1 inch per hour. This will be enough to cause some flash flooding, especially as you get into southeast Harris County, Chambers County, and Jefferson County.

While these rates are a little less than we feared, we will still see travel issues in spots east of the city, as well as south of the city as water continues to flow through the system. These conditions should improve a good bit by later this morning and especially this afternoon. The lopsided nature of this storm means that although the center may only just be on the east side of Houston by midday, the main impacts should be mostly out of our area by then.

Heavy rain and flooding risk will continue through the morning across Beaumont, Port Arthur, and into western Louisiana.

Later today and tonight

Though we expect the overall picture to greatly improve this afternoon, at least a few areas may see daytime heating lead to additional showers and storms popping up. Any of those would be capable of producing heavy rainfall, but they will be scattered and likely not widespread. We should see dry conditions tonight. High temperatures today will peak in the 70s, but if we do see any breaks in the clouds west of Houston, we could sneak into the 80s in a few spots. Certainly not terrible, but something to keep in mind if you are still without power this afternoon.

Eric will have our next update around 10 A.M.

Hurricane Nicholas made landfall at 12:30 am Tuesday on the eastern part of Matagorda Peninsula, about 10 miles west of the small city of Sargent. It had maximum winds of 75 mph at landfall. The storm is moving about 10 mph to the north-northeast, and along this track the storm should pass almost directly overhead Houston on Tuesday after sunrise. After that it should turn more to the northeast.

Winds

We’re starting to see wind gusts above 60 mph along the coast of Galveston Island, and we expect to see gusts in the 40s and 50s spreading inland over night. So far power outages in coastal counties range from about 90 percent of customers out in Matagorda County, closest to Nicholas, to about 20 percent in Brazoria County, to 10 percent in Galveston County. Further inland, Wharton and Austin counties have significant outages. More can be expected as Nicholas moves closer to Houston and Harris County this morning.

Rains

So far tonight we’ve seen a thick band of rain showers moving inland from Nicholas, and while the rains have been heavy they have not been excessively so. These rates of generally less than 2 inches per hour are helping to moderate totals. Overall accumulations through Tuesday should be 2 to 8 inches for coastal counties near Houston, with potentially more rain east near Beaumont as Nicholas tracks inland and slows down. Here is the latest rain accumulation forecast from NOAA for now through Wednesday morning.

For the Houston area, it’s likely that the heavier rainfall will wind down between sunrise and noon on Tuesday, with lesser chances afterward. Winds should die down as well. A sense of normalcy should return to our weather by Tuesday afternoon.

“Dirty” side of the storm

We often talk about the “dirty” side of a hurricane, which is located to the right of a storm’s center. This is where the strongest winds, rains, and surge typically lie. And this evening as Nicholas was moving into the Texas coast, its radar signature provided a textbook example of all the activity falling on the east side of the storm, with virtually nothing occurring to the west of the center.

Matt will have our next update by or before 5:30 am CT.

‘Twas the night before Tuesday, when all through the city
None were stirring, not even Harry Styles more’s the pity;
Dry stockings were hung by the chimney with care,
In hopes that St. Nicholas soon would not be there.

Alas, Nicholas is here. And he’s bringing lumps of coal for all. So we’d better discuss the forecast.

As of 10 pm CT, the National Hurricane Center says Nicholas has become a hurricane with 75-mph winds. Its center is presently located 20 miles southeast of Matagorda, Texas. The storm is moving to the north-northeast at 10 mph, and should come ashore the upper Texas coast later tonight, possibly near Sargent, Texas. No additional strengthening is anticipated, the hurricane center says. The storm is expected to cross the Houston region on Tuesday morning and then move into southeastern Louisiana and essentially stall before dissipating by Thursday or so.

Houston area rainfall

Our overall rainfall forecast remains largely unchanged. If you live inland of Highway 59 and Interstate 10, you’re very likely to miss out on heavy rainfall overnight and into Tuesday morning. My expectation would be for 2 inches, or less. If you live closer to the coast, particularly in Brazoria, Galveston, and Chambers counties, heavy rainfall is much more likely. Widespread totals of 4 to 8 inches are likely, with bullseyes of 10 inches or more that may produce localized flooding.

The radar image below tells the tale of the night. We can see the main band of thunderstorms along the Texas coast, but mostly offshore. This band of gnarly storms will to move to the northeast tonight, and how bad things get for the Texas coast will depend on how far inland it gets (or how far offshore it remains). Right now I’d be surprised if the heaviest rains pushed much farther inland than League City tonight. But we’ll see. I’ve also annotated the line where there’s no rain now. There probably won’t be much precipitation west and north of this line tonight, either, as Nicholas moves to the northeast.

As this system slogs toward the northeast over night, it will have the potential to drop rainfall across all Texas coastal areas. However, for now, it appears the heaviest rains will come over Galveston and Chambers counties, with lesser amounts further east, including the Beaumont and Port Arthur areas on Tuesday morning.

Wind and power outages

For inland counties, including Fort Bend and a majority of Harris County, this now appears more likely to be a wind storm rather than one of significant rains. As of 9:30pm about three quarters of Matagorda County were experiencing power outages as Nicholas battered its shores with hurricane-force wind gusts. These winds, although diminished, should spread inland over the next several hours. I’d expect at least scattered outages as trees fall into power lines.

When does this mess end?

Our confidence in when the heaviest rains from Nicholas push east of Houston remains middling, but I’d expect rains in Galveston County to wind down around sunrise or mid-morning.

Our next update will come at around 1 am CT.