Major flooding in the Rio Grande Valley as Hanna moves into Mexico

Good morning. We’re here to offer up a brief update on Hanna as the storm works its way into Mexico this morning.

Houston area

Things are quiet this morning in Houston. There are some showers south and west of us and another batch moving across the coast of western Louisiana. As some of this works into Texas, we should see showers and storms become scattered across the area.

Showers and storms in Louisiana will likely work toward our area today, bringing at least scattered rains, some heavy, to the Houston area. (College of DuPage)

Some folks won’t see much, but others may see a couple inches of rain in an hour or two this afternoon. An isolated severe storm is also possible. More typical scattered showers and storms will continue to be possible tomorrow and Tuesday, as onshore flow continues.

Rio Grande Valley

Hanna has moved into Mexico this morning, but the storm’s rains continue in the Valley. Mission has probably been the hardest hit of any of the cities in that area, and a flash flood emergency is posted for that area through late morning, as upwards of 10″ of rain has fallen, with more coming.

The heaviest rain as this is being written is falling east of Mission and just west of Harlingen. Several more inches of rain is likely to fall today and tonight as Hanna dissipates inland in Mexico.

Totals are impressive, especially just north of the Valley.

Areas in purple on this map of estimated rainfall are likely to have seen 9 to 10 inches or more of rain so far. (NOAA NSSL)

You can just make Mission out as the western-most purple area on the map, with upwards of 9 to 10 inches of rain. Other hard hit areas include Weslaco and Harlingen. The area just northeast of there with maximum totals is estimated to have received close to 20 inches of rain.This is right on the Arroyo Colorado near Arroyo City on the Cameron/Willacy County line.

Conditions should improve in that area tomorrow with more scattered showers and storms, but flooding could worsen in spots still today before subsiding. We will have the latest on the rest of this upcoming week tomorrow morning.

Hurricane Hanna reaches Padre Island, brings heavy rains to South Texas

At 5 pm CT on Saturday Hurricane Hanna made landfall along Padre Island, with maximum sustained winds of 90 mph. For Houston, our forecast remains unchanged. We will see periods of at-times heavy rainfall, but it should be intermittent enough that the worst impact we anticipate is some brief street flooding. Heavy rains should be more scattered on Sunday and backing off further on Monday. The rest of this post will focus on South Texas, where Hanna’s rainfall potential is much more serious.

Radar image of Hanna shortly after landfall. (RadarScope)

The rapid intensification of Hanna over the last 24 hours has helped drive a storm surge of 4 to 6 feet into locations near Port Aransas and Corpus Christi. The storm’s strongest winds have come in the largely unpopulated area between Corpus Christi and South Padre Island; and as Hanna moves inland its winds should continue to die down. Looking ahead, inland rainfall and the resulting flooding will almost certainly be the biggest concern.

Torrential rainfall continues to fall across South Texas, and this is likely to continue from now through Sunday. Hanna is moving, but it is only sliding slowly to the southwest at about 8 mph. For the next 24 hours to 36 hours, before Hanna moves into Mexico, away from the Gulf of Mexico, and begins to dissipate, the storm will be capable of tapping the warm Gulf waters to produce heavy rainfall.

NOAA rainfall accumulation forecast between Saturday evening and Monday evening. (Pivotal Weather)

Some high resolution modeling suggests that an additional 6 to 12 inches of rainfall may fall in locations such as Hidalgo and Cameron counties during this time period. And with these kinds of widespread totals we can probably expect some locations to receive as much as 15 inches of additional rainfall. This will lead to significant flooding problems in a region of the state already strained by the COVID-19 pandemic.

Hurricane Hanna will make for a wet weekend in Houston

Good morning. As of 7am CT, the National Hurricane Center has just upgraded Hanna to hurricane status, with sustained winds of 75 mph. The storm should make landfall near or just north of Port Mansfield later today, and may strengthen further before doing so.

Storm surge projections for Hurricane Hanna. (National Hurricane Center)

For the greater Houston area, this ultimately will probably yield little change to our overall forecast for a rainy and breezy weekend. We are going to see elevated tides along the coast of 1 to 3 feet from Freeport to Galveston, and along other coastal areas. In addition, these regions near the water will see some stronger winds, with gusts likely above 30 mph, while inland areas see gusts of 25 mph or above.

Houston radar at 7:24am CT on Saturday. (RadarScope)

In terms of rainfall, we’re still expecting a wet weekend, with 2 to 4 inches of rainfall coming down across most of the area as Hanna’s outer rain bands traverse the area. Generally, these bands should be spread out, and keep moving—helping to limit accumulations. Some streets may briefly flood due to high rainfall rates, however. We can’t rule out some isolated accumulations of 6 or more inches over the southern part of the Houston region.

Healthy rain chances will continue through Monday or Tuesday before we finally return to somewhat more normal weather for summer, which is to say highs in the low 90s and scattered afternoon showers.

Hanna, Gonzalo, and a third tropical system. (National Hurricane Center)

After Hanna moves off, the tropics should remain active. While Gonzalo is expected to die in the southern Caribbean Sea there is another system behind it that will be spinning westward across the Atlantic Ocean toward the Caribbean. Most of the global guidance is bullish on this system eventually becoming a hurricane (it would be named Isaias), and it will probably be something for the islands, and eventually the United States to track. But it will be several days before we have any sense of where the storm may ultimately go.

Tropical Storm Hanna to deliver a glancing blow to the Houston area

Good morning everyone. Tropical Storm Hanna formed last night, and it wasted no time gradually getting itself organized. As this has been happening, Hanna’s forecast track has continued to shift south, taking most of the significant impacts expected from the storm out of the Houston area. A lack of significant impacts doesn’t mean we’ll have zero impacts, however, so we’ll break down what to expect here and farther south in Texas as well.

Now

As of 5:30 this morning, Hanna was over the Gulf, about 300 miles east-southeast of Corpus Christi. Hanna was moving slowly but steadily just north of due west, around 10 mph or so. Maximum sustained winds were estimated to be 40 mph, but a reconnaissance aircraft from NOAA is headed into the storm to see if that hasn’t increased somewhat. Based on Hanna’s satellite presentation, we can assume it probably has strengthened a bit.

Tropical Storm Hanna on Friday morning had a lot of storms, though most of them were somewhat displaced to the south and east of the center as it tracks west toward South Texas. (Tropical Tidbits)

You can see a robust area of thunderstorms near the center of the storm. If you want to lodge a meteorological complaint about Hanna, it would be that the vast majority of thunderstorms are displaced to the south and east of the center of the storm. In other words, despite the pretty serious look on satellite, the storm does suffer a bit from a lack of symmetry that could indicate that while it’s strengthening, it may not be taking off like a rocket. It is likely still feeling a bit of wind shear, especially on its eastern fringe that is holding it back a little. Still, this is not an unhealthy storm and forecasts of strengthening up through landfall will likely come to pass.

The current National Hurricane Center forecast tracks Hanna toward the coast, arriving tomorrow midday somewhere between about Corpus Christi and South Padre Island, likely close to Baffin Bay.

The official NHC forecast continues to keep Hanna well south of Houston, with the most significant impacts in South Texas, while our area sees mostly nuisance-type impacts. (NOAA)

This will direct the most significant tropical impacts south of Matagorda Bay. Hanna keeps moving west and then southwest into Mexico, where it should dissipate on Sunday night or Monday.

Quick overview of what to expect for the Houston area

Here’s a quick “user’s guide” for what to expect in the Greater Houston area.

Rain: Isolated storms Friday, scattered storms Saturday, more numerous storms Sunday and maybe Monday. Rain totals of 1 to 2 inches on average, with higher amounts possible anywhere, but especially the farther south you go, possibly in excess of 3 or 4 inches in Matagorda. Lesser amounts possible north.

Flooding: Some street flooding is possible with any downpours, as is always the case in our area. Significant, widespread street or bayou flooding is not expected.

Wind: You should not expect winds to get much past 15 to 20 mph in the Houston area. Tropical storm conditions should be confined to the coast, with gusts up to 30 to 35 mph in Galveston and perhaps a bit stronger toward Freeport and the Matagorda Bay region.

Tidal & marine impacts: We expect tides to run about 1 to 3 feet higher than normal for Galveston and maybe a tinge higher toward Matagorda Bay. Minor overwash or tidal flooding is possible. Rip currents will be strong, so please use extreme caution. Waves are expect to be about 4 to 6 feet, maybe higher farther south.

Severe weather: Brief spin ups are possible in thunderstorms, especially as you get close to the coast, where a waterspout or two could occur.

Details for the Houston area

For today, we would anticipate isolated to perhaps scattered showers and storms. Expect a general trend of storms near the coast this morning, spreading inland this afternoon. Some locally heavy downpours are possible, but today should not be much worse than a typical summer day.

As Hanna approaches the south Texas coast tomorrow, expect the potential for steadier, heavier rain south of Houston. This would include Galveston, but we would especially include far southern Brazoria, Matagorda, and Jackson Counties. Tropical Storm Warnings are hoisted from San Luis Pass southward, so those areas are the ones most likely to also see tropical storm conditions. Showers and storms to the north of there will be mostly scattered on Saturday. In other words, some of us will see some heavy downpours, others may not see much of anything. The chance of heavier rain is obviously higher the farther south you go in the area.

The Houston area’s best chance at more numerous showers and storms and heavier rain will probably come Saturday night and Sunday as a surge of moisture comes in off the Gulf and out of Louisiana. That may continue off and on into Monday as well. By Tuesday and Wednesday, we should slowly return to a more typical summer pattern, with hotter weather.

When all is said and done, we expect probably 1 to 2 inches of rain on average in the Houston area, with a skew toward higher amounts south of the city and lower amounts to the north.

The current forecast of total rainfall is about 1 to 2 inches on average for the Houston area. The big ticket rainfall totals from Hanna will likely be south of Corpus Christi and in the Rio Grande Valley (Weather Bell)

However, depending on exactly how storms set up on Sunday, we could see as much as 2 to 4 inches of rain in spots, with the highest likelihood of this being south of I-10 and on the south and east sides of US-59/I-69.

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