Month: October 2020

6:45 am CT Thursday: Good morning. We’re tracking near-term weather issues related to Hurricane Delta, which is still expected to come ashore in southwestern Louisiana on Friday afternoon or evening. Then, we can anticipate a sunny, hot weekend before a cool front arrives early next week to usher back fall-like weather into the region. That’s a lot to cover, so let’s jump right in with an update on Delta.

Hurricane Delta

The storm has slowly organized over night and now has 100 mph winds. Overall, the Delta track forecast remains pretty locked in, with the storm moving to the northwest, and commencing a northward turn Thursday night. Along this track, which is is supported by virtually all of the reliable guidance and therefore of high confidence, the storm will very likely come ashore between Cameron, Louisiana, on the eastern side, and White Lake on the west. As you may remember, Hurricane Laura made landfall near Cameron in August as a devastating Category 4 hurricane. Delta will be weaker, and perhaps a dozen or two miles further east, but it will nonetheless bring repeat misery to a region still reeling from catastrophe only six weeks ago. This is truly horrible.

In terms of intensity, forecasters at the National Hurricane Center expect Delta to intensify today, and possibly reach Category 3 before moving over the cooler waters in the northern Gulf of Mexico and encountering higher wind shear. It is forecast to come ashore with 105 mph winds, as a Category 2 hurricane. Let’s briefly address the three main effects from Delta.

Wind

Here’s the latest forecast for maximum wind gusts from Delta. Note, this is not sustained winds, but the maximum winds that may briefly pulse up during Delta’s strongest squalls. These strongest winds will be along, and to the east of the storm’s landfall location.

The strongest winds will occur on Friday. Much of the Houston area is unlikely to see Tropical Storm-force wind gusts, but coastal areas will definitely become quite windy during the day and evening, with the possibility of some gusts reaching 60 mph, especially along Bolivar Peninsula.

Surge

And here’s the National Hurricane Center’s forecast for “peak storm surge,” which represents the combination of surge and high tide for coastal areas. Again, the worst effects will be to the right of the storm’s landfalling location. For Houston, coastal flooding of 1 to 3 feet will be possible generally north of San Luis Pass, including around Galveston Bay and across the Bolivar Peninsula.

Rain

In terms of rainfall, we still have some uncertainties, as there should be a pretty steep rainfall gradient—a line along which, to the west, there will be virtually no rain, and to the east where there will be 1 to 2 inches. We think this line probably will fall somewhere in Houston, but whether it’s along the Interstate 45 corridor, or further east, is difficult to say. Here’s the official forecast for rainfall, but we would rate this as fairly low confidence. In Houston, we should see some outer bands of Delta moving through today, with the heavier rain chances on Friday. We expect no flooding issues in the metro area.

Thursday

Today should see increasing clouds with the aforementioned chance of rain showers, especially on the southern and eastern sides of the region. Despite the mostly cloudy skies this afternoon, expect highs to reach into the upper 80s, with a warm night, and lows only dropping into the 70s. Hello, humidity!

Friday

This will be the day with the most impacts in terms of surf, winds, and rain. Skies will be cloudy, and highs may struggle to reach 80 degrees for most areas. Winds amp up during the day on Friday, with gusty conditions during the afternoon, evening, and overnight hours as Delta pushes through. With the kinds of winds we’re expecting we do not anticipate power outage issues in Houston, although there could possibly be a few problems right on the coast.

Saturday and Sunday

Showers should be ending by late Friday night or Saturday morning, and skies are expected to clear fairly quickly. The weekend will be sunny and warm, with highs in the upper 80s to lower 90 degrees. My sense is that this weekend and early next week are probably the last times Houston will see highs in the 90s in 2020, but that is a guess, not a promise.

Next week

A cool front appears to be on track to arrive on Tuesday to sap some of the region’s heat, with another stronger front probably arriving by or before the weekend.

Our next update will come no later than 2:30pm CT today.

2:35pm CT Wednesday update: Good afternoon, and it’s good to be back. Thanks to Eric for dealing with an absentee site partner for the last couple weeks and getting us from Beta to Delta. I sincerely hope this is the last storm we have to write about for the Gulf this year.

Hurricane Delta is emerging into the Gulf from the Yucatan this afternoon.

After being one of the quickest intensifying storms on record, Delta has taken a beating over the last 18-24 hours and, while it’s holding its own, maximum sustained winds of 100 mph may be a bit generous here. Either way, Delta is now back over warm water with relatively low wind shear, so odds favor it beginning to reintensify tonight.

The track forecast has continued to nudge a bit farther west, however that trend appears to be stable or ending now, and I think we’re close to the maximum for how far west Delta will track.

The last big holdout, the European model, which had been advertising landfall near the Texas/Louisiana border has shifted east by a good 25 miles or more today, and virtually all reliable model guidance now has Delta’s landfall occurring between Cameron, LA and the western edge of Vermilion Bay, or very close to/slightly east of where Laura made landfall. A word of advice: Don’t focus too closely on every wobble and maneuver Delta makes over the next 24-48 hours. While there is still a small degree of uncertainty on the exact track of Delta, the odds that there would be a significant enough shift to detrimentally impact the Houston area is very, very, very small. We all brace ourselves for The Turn™ during these events, and it will happen.

As far as intensity goes, modeling has been slowly easing up on the excitement since last night. Some of that is likely due to what happened to Delta on approach into the Yucatan and land interaction. But as of this afternoon, virtually all intensity forecasts are for this to not get above a category 3 storm in the Gulf before it weakens on approach to the coast. Wind shear is going to likely increase significantly, and the storm will encounter cooler water as well beginning tomorrow night or Friday morning.

That said, the biggest change with Delta over the next couple days will likely be the expansion of its wind field. Larger storms usually have lower intensity ceilings, but they compensate for that by spreading tropical storm or hurricane force winds out over a larger area. You can see this wind field expansion on the HWRF model by looking at 10 meter winds (winds experienced at ground level will be somewhat lower than shown here). The map at left is this evening’s forecast, while the map at right is for Friday afternoon. Both maps are at the same spatial scale, and you can see how the tropical storm force wind field (green, yellow, red) basically doubles in size as Delta comes north.

Hurricane force winds are in purple here also. So despite Delta perhaps being weaker, it will likely have impacts spread over a large swath of Louisiana and perhaps eastern Texas, with a significant surge once again possible along and east of where the center goes.

Speaking of surge, the first National Hurricane Center surge outlook was posted today, showing the potential for as much as 11 feet of surge above ground level if Delta comes ashore at high tide on Friday.

These surge values are rough, though certainly not quite as catastrophic as those seen in Hurricane Laura. But 11 feet of water is a bad day, and unfortunately, the areas around Vermilion Bay that were hammered during Laura are going to get another significant event with Delta.

Locally in the Galveston Bay area, we expect surge impacts to be more like Laura than Beta, with minor overwash possible near Bolivar and perhaps down Bluewater Highway south of Galveston into Brazoria County. Surge should not be much worse than 1 to 3 feet above normally dry ground. Storm Surge Watches have not been posted in our area, but they are hoisted east of High Island. Tropical Storm Watches have been posted from San Luis Pass to High Island.

Will we see tropical storm force winds in the Houston or Galveston areas? My hunch right now is that we won’t see this in Houston. Galveston always has a chance to briefly get to tropical storm force gusts or even sustained winds at times. But this would be mostly a Friday issue. At this point we don’t expect significant problems from wind in the Houston or Galveston areas.

For folks in southwest Louisiana and around the Beaumont/Port Arthur areas, the story is a little less clear. Assuming the wind field does expand as expected, we would likely see tropical storm force gusts and perhaps a period of sustained tropical storm force winds (35-55 mph) in the Beaumont or Port Arthur areas. In Lake Charles, which is still far from recovered from Laura, we expect about an 80 percent chance of sustained tropical storm force winds (greater than or equal to 39 mph) and about a 30 percent chance of sustained hurricane force winds (greater than or equal to 74 mph). This will not be another Laura in Lake Charles by any means whatsoever, however given that many, many structures in the city have not yet been repaired, this does have the potential to produce some considerable damage, particularly the farther west it comes ashore.

As far as rainfall goes, we don’t expect to see much more than perhaps a few outer bands in the Houston and Galveston areas. Rain totals will be manageable and no flooding is expected in our area.

In Louisiana, up to about 6 to 8 inches will be possible along and east of where the center comes ashore, which could cause minor to moderate flooding issues but really isn’t all that bad as far as these storms go. Delta will be a quick mover and out of there by Saturday morning.

Unless something dramatic changes this evening, our next update will be our regularly scheduled update on Thursday morning.

7 am CT Wednesday Update: Good morning. We’ll take a quick look ahead at our forecast for this week and then turn our attention to Hurricane Delta, which made landfall near Puerto Morelos, in the Yucatan Peninsula, around 5:30 am CT today. It had maximum sustained winds of 110 mph. The hurricane will move into the Gulf of Mexico later today.

Wednesday

Today will be warm and sunny, with highs likely climbing into the mid- to upper-80s with light northeasterly winds. We should really start to feel the return of moisture at the surface today, so it will feel a bit more humid, and nighttime temperatures will be a few degrees warmer than Tuesday night, likely not falling below 70 degrees in Houston.

Thursday and Friday

Our weather on both of these days will depend heavily upon how close Hurricane Delta gets to Texas as it moves into the western Gulf of Mexico. In terms of precipitation, for now, we’ll guess (emphasis on guess) the eastern half the region sees perhaps 0.25 to 0.5 inch of rain, with lesser amounts west of Interstate 45. The best rain chances should come on Friday, and partly cloudy skies should help to limit temperatures into the low 80s. Winds may gust up to about 30 mph, or higher, especially on the city’s east side, and along the coast.

Saturday, Sunday, and beyond

Some showers may linger into early Saturday, but for the most part, the weekend looks warm and sunny, with highs near 90 degrees. There is the potential for a cold front to arrive on Tuesday or so of next week, but it may get hung up for a few days and not move in until later. Still, we do anticipate more fall-like weather to return in about a week, give or take.

Delta, Delta, Delta

Delta has weakened overnight due to the influence of wind shear at mid-levels of the atmosphere, and it may weaken a little bit further this morning as its center briefly crosses the northeastern corner of the Yucatan Peninsula. As it reaches the southern Gulf of Mexico, the storm should begin to re-intensify tonight, and the National Hurricane Center anticipates Delta briefly pulsing back up to a Category 4 hurricane over the Gulf. (We’ll see).

As the storm moves north it will encounter less favorable conditions and should be on a weakening trend near landfall Friday. Frankly, I have significant questions about how strong Delta will be at landfall, and anything from a Category 1 to Category 3 hurricane seems possible. Most likely, the further east the storm tracks, the stronger it will be.

In terms of track, our overall thinking has not changed in terms of approaching Texas and then turning north. As you can see in the forecast graphic above, as we get closer to Delta’s Gulf coast landfall, the “cone of uncertainty” in the National Hurricane Center’s official track has narrowed. It now essentially runs from the border between Texas and Louisiana, on the west side, to southeastern Louisiana. This reflects what we’ve been telling you over the last several posts, that the forecast models are generally in quite good agreement on a landfall between the Texas-Louisiana border and Morgan City. Landfall now looks likely to occur some time during the middle of the day on Friday, or during the evening.

Along this track, as noted above, the greater Houston region would only see moderate effects, including increased winds on Thursday and Friday, some decent rain chances, and moderate coastal flooding at high tides. We will need to continue to monitor the storm’s track closely, but the greatest likelihood remains that Delta will be a near-miss for our area.

In terms of Louisiana, Delta’s effects will depend heavily upon its intensity. It does seem really, really cruel that this storm will probably make landfall not too far from where Hurricane Laura did so in August. However, we do think Delta’s winds will probably be less at landfall than Laura, and surge as well. Because the storm is expected to be moving fairly quickly to the north-northeast, rainfall amounts should generally be less than 8 inches for most areas.

Our next post will come no later than 2:45 pm CT.