If you missed it, Eric and I have decided to start doing tropical updates for you every week or two through hurricane season. We had our first one last week, which was rather detailed. This week, we’ll be a little more succinct!

Tropical outlook in a sentence

The Atlantic basin continues to be void of much interesting tropical activity, and it will likely continue that way for the next week to 10 days.

Near-term summary

Dust, dust, dust. And shear. Those two things are characterizing the Atlantic basin today. Dust from the Sahara Desert continues to roar across the Atlantic. This tends to be a fairly common feature in the early parts of hurricane season. We’ve noticed it a lot more in recent years, and I’m not sure if that’s because of some functional change or just because our observational capabilities have gotten so much more sophisticated. Either way, the last few years have seen a lot of Saharan dust in the basin in June and July.

From the satellite image above, you can see where dust (yellow/orange/red) is located, as well as cloud cover (gray). Virtually the entire Atlantic basin is littered with Saharan dust right now. This includes the Gulf of Mexico. Some of that thicker dust is likely to appear in Houston’s skies in the days ahead.

Why does this matter? Well, Saharan dust is extremely important globally. It’s a major source of nutrients for phytoplankton, and it helps to fertilize the Amazon. It obviously doesn’t come without problems, as the dust can irritate those who have sensitive respiratory systems, allergies, or asthma. It reduces air quality, and we may well see that here in Houston for late this week.

But from a tropical point of view, Saharan dust can help hinder systems from developing. The dust is indicative of dry air in the atmosphere. Obviously, hurricanes need moist air. Think about our weather here in Houston. On days with a “cap” in the atmosphere, there’s a barrier that exists preventing or limiting how high cloud tops can go. That reduces our thunderstorm chances. The Saharan air layer can act as a “cap” as well, preventing storms from billowing up. It doesn’t entirely prevent tropical storms or hurricanes from developing, but it can severely limit how well developed they can become. So curse the dust when it irritates your sinuses, but thank it for helping to keep the early part of tropical season under wraps.

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Good morning. The radar is a bit quieter this morning, so before jumping into the forecast I wanted to note a dubious record the city set last weekend. According to World Climate Service on Twitter, Saturday was the most humid day on record at Houston’s Bush airport (which has recorded hourly data since 1969), with an average hourly dewpoint of 79.7 degrees Fahrenheit. The four days from June 20 through June 23, in fact, ranked as four of the top six spots for daily mean dewpoint in Houston. As a reminder, here’s how Matt recently characterized dewpoints, and how they feel:

• 70s means uncomfortable, or typical summer
• 60s means humid, but not terrible
• 50s means mostly comfortable
• 40s or less means very comfortable or dry

Now, on to the forecast.

Wednesday

In case you were wondering, dewpoints this morning are generally in the low 70s. We’re going to see another day with scattered, daytime showers across Houston. Accumulations should be less than Tuesday, but we can’t rule out some areas seeing a 1 inch or so of rainfall, with a higher bullseye under the slowest-moving storms. Most of the area will probably see 0.25 inch or less. Highs will get up to around 90 degrees, although local temperatures will depend upon the extent of sunshine your area receives. High pressure should begin to build in this evening, shutting down rain chances area-wide.

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Storms are firing again this morning, primarily to the south and east of Interstate 69, where a few areas have already picked up 1.5 inch of rainfall. We’re going to remain in a pattern where there is the potential for storms through the next 12 to 24 hours before higher pressure returns to the area until the weekend.

Tuesday

Overall, our atmosphere should remain moist for pretty much all of today, with precipitable water values of 2 inches or greater, meaning it won’t take too much of a spark to generate showers and thunderstorms. This pattern will allow for the development of on-and-off showers, moving generally to the east-northeast. Unfortunately, storm movement will be fairly slow, which will allow for some areas to see totals of 1 to 3 inches, and some street flooding. Although the rain has developed near the coast this morning, various models show the potential for development at most any location later today. Clouds and intermittent showers should help keep highs in the upper 80s for most of the region.

Wednesday

Pressures begin to build, and this should help to limit storm activity. However, with a still-moist atmosphere, I think at least about 30 percent of Houston should see at least some brief showers. Highs will get into the low- to mid-90s, as some sunshine returns.

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A broken line of showers and thunderstorms is pushing through Houston on Monday morning. These storms have been a little more frisky than anticipated north of the city, dropping 1 to 3 inches of rain, but they appear to be weakening as they move through central parts of the metro area toward the coast. These storms should move through Houston by mid-morning and then off the coast by or before noon. The primary threats are wind gusts above 30mph and brief, heavy rainfall. The primary benefit is cooler air thanks to a “cold pool” in the atmosphere that is helping to drive this morning’s storms. Alas, it won’t last.

Monday

After this area of relatively unstable air moves away from Houston later this morning, rain chances should fall significantly—leaving the region with only isolated, to scattered showers for the rest of the day. Winds will remain blowy, with gusts up to about 20mph. Partly to mostly cloudy skies should help moderate temperatures for the remainder of the day, limiting them to perhaps 90 degrees or even the upper 80s. Low temperatures on Monday night may get into the upper 70s for inland areas, but we won’t see too much cooling.

Tuesday

This has the potential for another wet day, as an upper-level disturbance moves through the atmosphere from west to east. This will provide a healthy chance of showers, probably about 50 percent, later in the day. Forecast models are hinting at the potential for another 1-2 inches of rain from this system for parts of Houston that get hit—and probably little to no rain for those that don’t. This is because storms that develop on Tuesday may be fairly slow moving. Highs will be in the low 90s.

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