Month: February 2018

Houston’s perpetual clouds continue

Posted by Matt Lanza at 6:45 AM

Statistically, I don’t know whether or not February has been Houston’s cloudiest month on record, but I think we all know it has to be close. Yes, we’ve had sunny periods at times, but they’ve been short-lived and fleeting. I’m not sure what the exact number is (we’ll probably tally it for you at the end of the month), but roughly 70% of the month appears to have had some level of overcast cloud cover. February averages somewhere around 45% cloud cover in Houston. Sunny weather will return eventually. That much we promise.

Today

Low clouds and fog are pretty prevalent this morning as this pesky front we’ve been dealing with begins to try and advance back north. Temperatures are all over the place, but it’s pretty easy to see the front.

Morning temperatures (6:30 AM) suggest grabbing a jacket north of Houston and perhaps putting on shorts southeast of Houston. (NWS)

The front has made it back to almost US-59. It’s in the 70s in southeast Houston, but 50s on the west and north sides. As the front pushes back north and west today, expect warmer, more humid air to win out just about everywhere. Low clouds and fog should gradually lift, but it may be a process in spots, meaning clouds and drizzle could mar a good chunk of the day. Folks well north and west of Houston may have the most trouble getting warm and clearing at all today.

Disturbances will continue to push through, but the heavy rain should stay oriented well to our north, where 1-3″ will be possible north of Waco and across the DFW Metroplex. Temps will top off in the mid or upper 70s southeast of Houston, perhaps near 80 with some sunny breaks. Northwest will probably see low-70s or so on average (warmer closer to Houston, cooler further away).

Weekend

Saturday will likely behave somewhat similar to Friday afternoon with an isolated shower, but mostly just AM clouds or fog, some sunny breaks, and humidity. Folks way north of Houston, such as up toward Huntsville, could see a little steadier rain Saturday morning. Again though, the bulk of the rain will stay well north.

With any sunshine, we’ll easily scoot above 80 Saturday, but otherwise it’ll be upper 70s. The front comes back at us tomorrow evening as a cold front. The good news is that while we should see some showers and perhaps a thunderstorm Saturday evening, it shouldn’t be anything too serious. Right now, I’d be on the lookout for that between 4 and 8 PM, maybe a little a later southeast. And any heavier rain you see will probably be brief.

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The cold front that has been driving all of the precipitation finally pushed through the Houston area during the overnight hours, and so we’re generally seeing low temperatures in the 50s this morning—with 40s to the west and far north of Houston. The front lies just offshore, so this cold weather won’t last as the warmer air pushes back onshore.

Temperatures on Thursday morning show the cold front has pushed through almost all of Texas. (Weather Bell)

Thursday

High temperatures today will be in the 70s under cloudy skies. Rain chances remain, but we’re not going to see the prolonged, heavier showers the region experienced on Wednesday. About half of the area probably won’t see any rain at all today, especially along the coast. Lows tonight will be warmer, as the onshore flow resumes.

Friday and Saturday

Friday and Saturday will be warmer and muggier under mostly cloudy skies, as Houston falls back into a pattern we’ve experienced a lot of this month. Expect highs in the upper 70s, with southerly winds, and warm nighttime temperatures in the 60s. Rain chances will be lower on Friday, and a bit higher on Saturday as moisture levels ramp back up and a cold front approaches and moves through the area during the evening or overnight hours.

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Why are thunderstorms so common during spring months?

Posted by Braniff Davis at 11:59 AM

As most Southerners know, the arrival of spring also means the arrival of severe weather season. On Wednesday morning, many Houstonians heard the first rumblings of serious thunder for 2018, and if history tells us anything, this is just the beginning of a potential spring full of thunderstorms, flooding, lightning and tornadoes. What is it about the springtime that initiates this activity?

Hot, Hot Heat

Thunderstorm formation depends on atmospheric stability. We’ll forego talk about lapse rates and latent heat for now, and describe stability in simple terms. During the wintertime, our atmosphere is generally very stable. This means that conditions in the air prohibit any vertical motion. For thunderstorms to develop, they need warm air to rise from the surface, then to cool and condense into a tall, vertical column of clouds. In a stable atmosphere, this is nearly impossible.

As winter turns to spring, two things occur that make the atmosphere much more unstable. First, the air around us, especially if that air comes in from the Gulf, becomes much warmer and much more humid. Yesterday, February 20th, Bush Intercontinental Airport recorded a high of 80°F, with relative humidity values staying above 70%. This warm, moist air mass created a perfect environment of instability around us.

This diagram shows how air, heated at the surface, rises in the atmosphere until it condenses into a cloud. (Ahrens)

Second, as days become longer and the sun rises higher in the sky, the sun heats the ground, which, in turn, heats the air directly above the ground. This warm air will eventually rise in an unstable atmosphere, pushing cold air out of the way, as the diagram above shows. As it goes up, the air begins to cool, and as it cools, the water vapor in the air will condense–into clouds! If the atmosphere remains unstable, and these pockets of warm, condensing air rise rapidly, we have the recipe for a thunderstorm.

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A round of thunderstorms moved through Houston during the overnight hours, dropping as much as 2 inches of rainfall for some areas pretty quickly, but now the Houston region is seeing a break that should hold through at least sunrise and probably the morning commute.

Wednesday

The cold front that’s helping to drive these showers (along with some kinks in the atmosphere moving northward into the region) isn’t going away, so there’s the potential for redevelopment of heavy rain later this morning and throughout the day. To that end, the National Weather Service has issued a Flash Flood Watch through 3pm this afternoon for most of the region, excepting the coast.

A flash flood watch is in effect until 3pm CT. (National Weather Service)

With that said, I don’t things will get too bad today, and probably at most we are looking at the potential for some short-lived street flooding during heavier downpours. Bottom line—check the radar before heading out for any trips beyond the local grocery store. The front should eventually make its way through most of Houston, leading to a somewhat cooler night in the 50s for most of the area except for probably along the coast.

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