With a little more than 10 days to go, we’re still in the realm of considerable uncertainty about the forecast for the 2018 Houston Marathon, but the good news is that the forecast remains fairly consistent from model run to model run. This can give us some small confidence that weather for the marathon will be a bit cooler than normal.
On Tuesday I discussed the use of ensembles, and for the sake of comparison I’ve looked at each individual member of the European ensemble (12z) run from today to determine what kind of temperature anomaly is forecast for the morning of Sunday, January 14th. Broken down by percentages, here’s what we have today:
After 2017 in Houston, which featured everything from the costliest hurricane to ever strike the United States to a rare December snow, we can hardly guess what the near year will bring. (Certainly, we can be relatively confident in heat and humidity). Whatever this way comes, be it snow, rain, or intense heat, we’d like you to know that Space City Weather will be here every step of the way.
And that is why I am so thrilled to announce today that our sponsor during last year’s hurricane season, Reliant, has stepped forward to support the site for all of 2018. The company, and its president Elizabeth Killinger, believe strongly in the value we bring to to the Houston community, and they wanted to support our efforts. That means two important things for readers of Space City Weather.
One, we will have no outside advertising on the site. None. No auto-play videos. No pop-ups. Just a clean interface. This should make for lightning fast load times. Perhaps most importantly, it means we do not have to generate clicks for the sake of clicks. We don’t need to clickbait you because the value of our site isn’t determined by traffic. So if there’s not much to say about a 95-degree day in August, we won’t waste your time (or ours) by saying much.
Two, neither Matt nor I has much of a background in business or marketing. We’re scientists. We’re meteorologists. We’re writers. We just want to inform, entertain, and help you make decisions about weather and your lives. To that extent, having Reliant sponsor the site for all of this year means we can focus on weather, and pay with bills, with a minimum of distraction.
Finally, let me just say that I’m personally pleased that Reliant is back. Their very name is part of the ethos of this site. We aspire to provide a source of reliable information about weather in the greater Houston area. They’re a reliable provider of electricity and home services to the same market. It’s a great match for the new year.
Houston saw some scattered light snow and sleet on Tuesday evening, but drier air at low levels of the atmosphere prevented more widespread coverage. After this system moved out of the area, skies began to clear from west to east across the region after midnight and this allowed for very cold temperatures to settle into southeast Texas. As of 6:30am CT, lows range from about 20 degrees in College Station, to 25 in the city of Houston, to 30 degrees in Galveston. Up north, this is nothing. But for Houston, this is very cold—with many sites tying or breaking record low temperatures for January 3. If you’re tired of this, there’s good news. We’ve seen the worst of it now.
When you look at forecast low temperatures for Wednesday morning, suddenly the mid-20s doesn’t seem all that bad. (Pivotal Weather)
Wednesday through Friday
One big thing happens today: full sunshine returns to Houston. It’s been awhile. But the next three days should see nearly continuous sunshine during the daytime hours. This will allow for a sloooow warming trend, from highs today in the low 40s to the low 50s by Friday. Overnight lows, too, should climb from around 30 degrees Wednesday night to about 40 degrees by Friday night.
Hello fellow marathon runners and volunteers. In 12 days, it will be all over but the recovery. And now that the big training runs are over, all that we can do is trust our preparation, and hope for good—cold—weather on the big day. To that end, for the rest of this week, I’ll be providing afternoon updates on what we can expect for Sunday, Jan. 14th.
Of course any weather forecast beyond about seven days out is going to have a lot of uncertainty, and anything beyond 10 days is even more problematic. But that does not mean such forecasts have zero value. The best way to look at weather this far out is to study the ensemble forecasts of the main global models. These are the 50 or so lower resolution runs of a given model, with slightly different initial conditions. By looking at the spread in output from these models, we can gauge the probability of cold, normal, or warm weather for 12 days from now. Looking at the 12z runs of the European and North American models, here’s what I have for you.
Starting with the European model I have broken down the possibilities for start line temperatures into four different categories:
Warm: 3 degrees F or more warmer than normal
Normal: +3 to -3 degrees within normal (average high is 65, low is 47 degrees)
Cold: -3 to -10 degrees below normal
Very cold: -10 degrees or more below normal
In looking at each individual ensemble member of the European model, here are the Houston temperature anomaly outputs sorted by category:
Warm: 5
Normal: 4
Cold: 33
Very cold: 8
Too obtain probabilities, just multiply those numbers by two. So, roughly, according to the European model this afternoon, there is a 20 percent chance of warm or near-normal weather for the marathon, and an 80 percent chance of cold or very cold weather.
Looking at the GFS model, the we can see the mean of the ensemble members for January 14th is about 2 Celsius degrees (4 degrees Fahrenheit) below normal. But this model isn’t as cold as the European model.
Average temperature anomaly produced by the GFS ensemble members. (Weather Bell)
This is a much better forecast for the 2018 run than what we saw in 2017 (warm and very humid), but it is far from locked in. There are also some concerns.
The models are suggesting that some kind of fairly strong cold front moves through the region toward the end of next week, and this could bring with it some decent precipitation. If that front is late, we could still be warm for the marathon. Or the front could drag through on a Friday or Saturday, leaving behind some cold rain for the marathon itself. That, obviously, wouldn’t be ideal either. All that said, I’d still rather be looking at probable cold weather more than just about anything.
