Matt Lanza

TD Imelda marching north, heavy rain for many tonight

Tropical Storm Imelda has begun its transformation into a significant “blob” of rain over Southeast Texas this evening. Let us walk you through what we are expecting through Wednesday morning.

Now

Imelda is now classified as a tropical depression, and if I’m reading the radar correctly, the center as of 7:45 PM was located just west of Pearland and becoming more diffuse.

Tropical Depression Imelda is spinning away and crawling north this evening across Brazoria County. (RadarScope)

You can see from the radar loop above that Imelda has 2 or 3 areas of main concern, as it relates to rainfall. There is the main “core” of the storm over Brazoria County. This will be the primary rain producer this evening. As the center crawls north, that will come with it. This is what we are concerned about for the bulk of the Houston Metro.

The second area is a feeder band to the east of Baytown. That is aimed at parts of Galveston Island and north toward Chambers and Liberty Counties. That is not expected to move much, and within this region, expect heavy rain and potentially localized flooding overnight.

The third area is a band well to our east, aimed at the Beaumont/Port Arthur area or just west. That will be capable of some heavy rainfall tonight as well. But it may weaken a bit as this band near Baytown takes over.

So a lot happening here.

Overnight

I mentioned above that Imelda’s center is becoming more diffuse. That means that more erratic behavior of the storm track could occur. So expect that heavy rain currently located over Brazoria, Galveston, and southeast Harris Counties to lift north into the bulk of the Houston metro area. At nighttime, tropical systems can sometimes see rains intensify a bit. So I fully expect heavy rain at times in Houston and points south and east. At a minimum we would expect 2 to 5 inches of additional rain in these areas by sunrise on Wednesday. We could see some spots pick up as much as 5 to 8 inches or even more, however, and those would be the areas we’re most concerned with in terms of flooding. Again, that would be most likely from Downtown Houston south and east.

For those north and west of Downtown Houston, we expect periods of rain overnight, locally heavy. While we will monitor those areas for flooding risks, we do not think it is quite as serious as south and east. But given that there is still a degree of uncertainty with this system, the entire region should monitor the progress of the rain, both before bed and when you wake up. Do not assume tomorrow that you’ll be able to get to the airport or to work without issues, so make sure to check in on what has transpired overnight in the morning.

Wednesday daytime

We should see rains continue off and on through the day Wednesday. We could see a bit of a lull in the activity for a time during the afternoon hours before heavy rain sets back up late. Again, we have some uncertainty around exactly how tomorrow will unfold. Eric will have an update later this evening, and I will update you more on Wednesday’s outlook in the morning.

Wednesday evening and beyond

We expect another round of heavy rain tomorrow night, again in multiple areas. We’ll likely see the “core” of the storm reignite tomorrow night with heavy rain gradually lifting north of Houston. We aren’t entirely sure if that will be aligned over the center of the city or more to the east. We also will likely see another significant “feeder” type band east of Houston, though we’re not quite certain where that will be aimed. Check with us tomorrow for the latest on these aspects of the storm. We could see some very heavy rain from this, and with the grounds certainly saturated by then, we would expect a good amount of flooding risks, potentially significant to develop. We continue to expect event totals to be on the order of 5 to 10 inches on average, with isolated smaller areas seeing as much 20 inches or more.

(Space City Weather)

Eric and I will continue with a Stage 3 flooding event expectation for Imelda’s rains tonight, tomorrow, and Thursday. This remains an evolving situation though, and it would be best to check back for the latest several times through the event. Eric will have an update around midnight.

Hot and mostly dry weekend, with an update on the tropics

Over the last 5 days, most of us have seen at least some rainfall with a smattering of storms each day. Not all of us have seen significant rainfall, however.

Feast or famine in the rain department over the last 5 days. Some places have seen 2 to 3 inches, while others have seen next to nothing. (Harris County Flood Control)

Apologies for the map that is clearly excluding some parts of the area. If you’d like a bigger view, you can view recent rain totals at Harris County Flood Control. Amounts of up to 2 inches or so have occurred near Acres Homes, Sugar Land, and out by Katy, with higher amounts in a few spots near there. Then, you have spots like the East End, far northwest Harris County, and some pockets south and also northeast of Houston that have registered little to no rain at all. For those seeking rain, we’ve got nothing good to report for the next couple days.

Today & weekend

Today and tomorrow should be fairly straightforward forecasts. We should see ample sunshine and hot temperatures. Look for daytime highs in the mid- to upper-90s both days. Nighttime lows into Saturday morning should get to the mid- to upper-70s. If we’re looking for a bright spot in the relentless heat, it’s that the nighttime temperatures and humidity levels will not be terribly oppressive. Heat index values should be mostly under control.

High temperatures on Saturday will probably hit the upper-90s in most of the area. But humidity will not be terrible. (NWS forecast via Weather Bell)

Sunday gets a tiny bit trickier. Moisture from an area of low pressure in the upper atmosphere will take over most of the western Gulf but primarily offshore. We should see at least a few showers being flung toward Galveston and other areas southeast of Highway 59/I-69 on Sunday morning or afternoon. But most places will probably stay dry. We’ll start in the 70s and end in the mid-90s.

See full post

September sizzle slogs along

Autumn is really just a state of mind. In Houston it has to be because you certainly would never know it was just about autumn by stepping outside. The high temperature on Thursday was 99 degrees at IAH Airport. Hobby managed to hit 96 degrees. This heat will continue.

Today and weekend

Expect mostly a rinse (without the water) and repeat weekend of weather here in southeast Texas. We will have sunshine and heat. High temperatures should flirt with 100 degrees each day for Houston and points north and west. Coastal locations should top off in the mid-90s. Morning lows should be in the mid- to upper-70s. It may be a degree or two less hot on Sunday.

It should be around or above 100° all across eastern Texas and Louisiana today. (Pivotal Weather)

As Eric noted yesterday, we will definitely have a good shot at tying or breaking some long standing record high temperatures today and tomorrow. Sunday will still be possible but probably a bit less likely. The records:

Friday: 99° (1909)
Saturday: 98° (1963)
Sunday: 100° (1907)

Stay cool and do your best to conserve energy, particularly today.

Early next week

The dome of high pressure responsible for our surge of September heat is going to migrate off to the east next week. It won’t be far enough away to allow any kind of meaningful cool air to drop through the Plains, but it should be enough to at least allow sea breeze showers each day off the Gulf. This would be of the 20 to 30 percent chance variety. I would expect mid-90s each day, along with a bit more more humidity.

See full post

Dorian still lashing the northern Bahamas, still a category 5 storm

Note: This post will cover Hurricane Dorian, which presents no threat to Texas, but which we are covering due to general public interest. For Houston, there are no tropical threats for the foreseeable future. It just looks very hot with diminishing rain chances over the coming days. Our normal posts will resume tomorrow.

Hurricane Dorian has unleashed utter fury on the northern Bahamas over the last 24 hours. Great Abaco and Marsh Harbour took a direct hit yesterday while Dorian was at its peak intensity. Grand Bahama Island was hit directly overnight, and the storm’s forward motion has slowed to approximately 1 mph with the center about 30 miles northeast of Freeport.

Dorian is expected to gradually weaken a bit through the day today, though it will remain an exceptionally dangerous storm, likely of at least category 4 intensity. We are seeing signs of a possible eyewall replacement cycle underway though, which should allow the storm’s maximum winds to weaken, while the size of the wind field expands a bit. Dorian will fluctuate in intensity over the next day or two before beginning a more steady weakening trend as it lifts north later in the week.

Where is Dorian going?

Dorian’s official track forecast keeps some portion of the Florida coast in the cone, but the storm is still expected to track just offshore. (National Hurricane Center)

That remains a tricky question, but the good news if you live in Florida is that everything is basically happening the way it was expected to happen in terms of track as of this morning. Anytime a storm slows to 1 mph, there is some inherent uncertainty in the details of a track forecast. But weather modeling is almost entirely on board with a track very similar to Hurricane Matthew in 2016, as it moves up the coast just offshore of Florida, Georgia, and the Carolinas.

Dorian will be a close call in Florida and up the coast, but the vast majority of data keeps the center just offshore. (Weathernerds.org)

The latest European ensemble forecast from overnight is shown above. Again, this is just the European model run 51 different times with some tweaks in initial conditions to give a better idea of goalposts in the forecast. A few things to note. First, of the 51 ensemble members, there are still around 8 to 10 that bring the center onshore near Cape Canaveral or just south of there. While the odds aren’t high, they aren’t zero, so folks in Florida still need to be prepared. Even assuming the track stays 25 to 50 miles offshore as expected, that will still be close enough to deliver strong winds, surge, and plentiful beach erosion to the entire coast. Remember, Matthew took a similar track, and although no two storms are alike, it underscores that severe impacts can still occur without a landfall. The Florida coast will need to hunker down tomorrow through Wednesday.

As Dorian treks northward, finding its way between the high pressure over Texas and the one in the Atlantic, it will begin to accelerate. Again, this will be close to the coasts of Georgia and South Carolina, though probably still offshore. As it passes North Carolina, there will be some chance of a landfall near Cape Fear or Cape Hatteras as the storm passes. Folks in the Carolinas and Georgia should prepare for significant coastal impacts, as well as heavy rain. Again, as we saw during Matthew in these areas, significant impacts can still occur far from the actual center.

Dorian should finally exit at the end of this week, and hopefully we see no more threats to land masses for a bit.