Matt Lanza

Late-June tropical Atlantic update: Continued quiet for a bit

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.

Widespread Saharan dust is spread out across virtually the entire Atlantic basin right now, which should help limit tropical activity for a little while longer. (University of Wisconsin/NOAA)

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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Mid-June update on the tropical Atlantic—likely quiet until early July

Eric and I had a conversation this spring to discuss some new ideas for the site, and ways to help readers navigate hurricane season. We absolutely feel people’s uneasiness every time it rains here, and a general sensitivity to the rumor and speculation that springs to life during hurricane season. So we have decided that every week or two, we will publish a more in-depth outlook for tropical activity in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico so that you understand what’s happening, and what could happen in the next couple weeks.

Tropical outlook in a sentence

Tropical development is unlikely over the next week or so across the Atlantic Basin, but we are eyeing July for a possible increase in activity.

Near-term summary

Historically, we would watch the Bay of Campeche and Gulf this time of year for development.

Historically, storms have formed in the Gulf and Bay of Campeche in the final third of June. (NOAA/NHC)

As of now, no tropical activity is expected over the next week, as conditions should remain mostly unfavorable for storms to develop in those areas and elsewhere.

Looking at satellite imagery from Tuesday morning, we have a couple tropical waves moving across the eastern Caribbean and a couple disorganized waves elsewhere.

The tropics show a few disorganized disturbances and mostly calm conditions today. (College of DuPage)

None of these waves is a candidate for development as of right now, and if anything, they should fizzle out and stay safely away. So: Good news, as we just don’t see much of anything out there.

Weather model fantasy-land

One of the biggest hurdles to good tropical information during hurricane season in the social media era is a tendency for folks to mention a model solution with zero context or just because it shows something extreme. You’ll see something like, “This model is just one solution but it shows a category 10 hurricane in the Gulf in 15 days! You probably shouldn’t believe it, but here it is anyway.”

Is there anything showing up on the models in days 10-15? Not at this time. The GFS model, which is the most frequent offender with fantasy-land storms is quiet right now. The GFS tends to have a bias early in the hurricane season, and then again later in the hurricane season. The bias is worst in May and early June, where it can often spin up systems in the Caribbean that never materialize. I tried to run the math on it last season, and during the month of May 2018, 79% of the time the GFS showed a storm beyond day 10, it never materialized.

Now, the GFS model was recently upgraded which should hopefully lead to reduced false alarms, but we won’t know much about that in practice until next May. Within the season, it still seems to show more false alarms than not, and Eric and I try to sort through the noise for you. Let this just serve as a reminder to be cautious of extreme modeled solutions posted on social media without much context.

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High humidity reclaims the throne this weekend

After a week that saw one of the longest June stretches of relatively comfortable humidity in recent memory, we will shift back into the thick of summer today and this weekend.

Today & weekend

Look for sunshine and some clouds today. We’ll top out in the low-90s once again, and humidity, though still relatively low for June, will begin to inch upwards. As of 5 AM, we ended a streak of 71 consecutive hours at Bush Airport with dewpoints of 70° or lower.

We talked a little more about dewpoints earlier this week.

Beginning tomorrow, with the humidity back in force, we can expect clouds, sun, and at least a few showers or a thunderstorm along the sea breeze as it lurches inland in the afternoon. I suspect most of us will be dry Saturday, but you’ll want to have the umbrella nearby to be safe. The morning starts in the mid- to upper-70s, and the afternoon will top out in the low-90s.

Sunday poses a trickier forecast, as the environment looks a bit more favorable for scattered showers and thunderstorms inland. We’ll likely see some activity along the sea breeze again as it moves inland from the Gulf, but we’ll also see a scattering of inland storms, especially north of I-10 and west of I-45. Temperatures will be a little warmer in the morning Sunday, bottoming out in the upper-70s or near 80 degrees. The afternoon should be near 90° where it rains or in the low-90s elsewhere.

Air quality, dust, and wind

I want to briefly focus on some other issues this weekend.

Air quality: Another ozone action day is in effect today, which means air quality is going to be unhealthy for sensitive groups. That said, it should not be quite as high as it was yesterday because winds should be a little stronger today. But those in sensitive groups (particularly elderly, children, or folks with lung or respiratory ailments) should take it easy and try to stay indoors when possible, especially in the afternoon.

Air quality is again forecast to be in the “unhealthy for sensitive groups” criteria int he Houston area due to high ozone levels Friday. (EPA)

Dust: Saharan dust! It’s back! Look for the first real Saharan dust cloud of the season to reach our shores Saturday morning. The dust should dissipate on Monday. This should only be a minor dust event, but it could mean the color of the sky dulls a bit; think more gray than blue, even without clouds. Sunsets and sunrises could be a little bit more interesting looking.

Saharan dust will appear over Houston this weekend, though it should not be a significant event. (NASA)

You may notice more haze than usual or even a little irritation if you have allergies or respiratory ailments. We may get another minor dust event around midweek.

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One more mostly nice day before typical summer returns to Houston

Dry air poured back into Southeast Texas yesterday, and despite high temperatures near 90 degrees, it really didn’t feel bad at all. In fact, dewpoints dropped into the 50s officially at IAH Airport for the first time in June since 2017. We’ve got one more day of this nice stuff today before we return to more standard summer.

Today

Sunshine dominates once again. With dry air in control, we should again see humidity drop to near “comfortable” levels for many parts of the area. Look for high temperatures to pop back to 90 or better for most, however.

Air quality today will be a little better than yesterday, but still unhealthy for sensitive groups due to ozone. (EPA)

Winds will again be on the light side, so expect air quality to be fairly stagnant once again. While not as bad as Wednesday, today will again be an ozone action day, with poor air quality this afternoon. If you’re in a sensitive group or struggle on bad air quality days, take it easy and try to stay indoors later today. If you’re ever curious about the air quality outlook, the Texas Commission on Environmental Quality publishes 4-day forecasts each day. You can bookmark that link here.

Friday

Look for another sunny day tomorrow. The difference will be in the humidity. Dewpoints are expected to slowly rise late tonight and most of the day Friday, and they should end up back around 70, or uncomfortable, by Friday evening. Expect us to start the day pleasant (mid-60s) and finish hot (low-90s). Air quality will improve a bit as onshore winds kick up during the day.

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