Author: Matt Lanza

20Sep

Beta on track for a Texas landfall Monday as a tropical storm

Posted by Matt Lanza at 8:49 PM

8:50 pm CT Sunday: Good evening folks. Matt started this post earlier, but Eric is stepping in to finish it due to a family matter. Read to the end to find out what took Matt away—and you’ll understand the lengths to which we’ll go to make sure we’ve got Houston covered in times of severe weather!

It’s been interesting to watch the evolution of Tropical Storm Beta today. The storm looked terrible this morning, had a renaissance this afternoon, and has now reverted back to mostly unimpressive, but standard tropical storm fare. You can see how it has progressed on satellite through the day, from morning thunderstorms with an exposed center to afternoon storms under a consolidated looking center to a broad, weaker looking storm this evening.

Beta’s evolution today has led to it looking fairly different at times but packing mostly the same punch as it had when the day began. Click to enlarge. (College of DuPage)

All in all Beta is who we thought it was: A moderate tropical storm fighting shear and dry air but occasionally feeling the hospitality of a warm Gulf of Mexico. We expect only slight changes, if any, in intensity over the next day or so as it nears the Texas coast and likely comes ashore on Monday.

Beta’s forecast track and intensity is very little changed this evening versus where it was 12 to 18 hours ago. The storm picked up a little forward speed today and is currently about 150 miles east-southeast of Port O’Connor and the entrance to Matagorda Bay. Beta will move generally west or west-northwest through the night and into tomorrow, eventually making landfall by around Noon tomorrow, give or take. After this the storm will eventually turn to the northeast, perhaps passing near Houston over land, or offshore. During this time it should gradually become more disorganized. It should be gone by Wednesday or Thursday. Good riddance!

Rainfall

In terms of precipitation, we’re still in the same place we’ve been for awhile with our Flood Scale. We have a Stage 2 flood alert for coastal areas south of Interstate 10, and a Stage 1 event for areas north of Interstate 10. Neither the global models or the regional models that can better model convective storms are showing really aggressive rainfall totals that would lead to significant widespread flooding this week.

Regional convective model forecast for rainfall through Tuesday morning. (NOAA)

Beta’s heaviest rains should come between Monday morning and Wednesday morning, and some of our best regional models suggest a reasonably healthy band of showers could move into Houston around sunrise tomorrow. (We’ll see). We generally expect 2 to 8 inches of total additional rainfall across the region, with higher isolated amounts, and our greatest concern is pockets that may see the majority of that rain in a couple of hours. This should generally cause street flooding, but we’ll be watching closely for trouble spots.

Wind speeds

We’ve been tracking winds this evening, and there have been some gusts near tropical storm-force along Galveston Island. We think winds will probably pick up a little bit more during the overnight hours before beginning to back off Monday morning. Most of the Houston area—and certainly locations north of Interstate 10—are unlikely to see prolonged tropical storm-force wind gusts from Beta. Here’s a look at the European model’s forecast swath of maximum wind gusts from the storm.

European model for maximum wind gusts in Houston this week. (Weather Bell)

Sustained winds will be lower. This should not be enough to cause significant electricity problems for inland areas, although we may see some power outages right along the coast.

Coastal surge

The most dramatic effect our region has seen from Beta has been rising waters along the coast due to the storm’s easterly winds and surge. We expect the highest levels to occur with high tides this evening along the coast, and again on Monday morning. Very high water levels will persist into Tuesday before really beginning to ramp down on Wednesday. We have already had reports of many low-lying roads on Bolivar Peninsula and the West End of Galveston Island becoming impassable.

Coastal flooding outlook for Galveston. (National Weather Service)

 

Our next update will come no later than 7:30am CT Monday.

Matt’s end note: I’m about to become a father for the second time, and nature called upon us this evening. I’ll be taking a break from the site for a little while for obvious reasons, but will pass along the good news when possible! Stay safe!

20Sep

Beta testing the forecast this afternoon, but overall it remains on track

Posted by Matt Lanza at 2:27 PM

2:30 pm CT Sunday: Our post this morning was sour on Beta. Maybe we trash talked it too much. I don’t know. What I do know is that it looks much healthier than I expected 5 to 6 hours ago, and it’s conceivable that Beta is at least making an attempt to form into a hurricane — temporarily. We still feel that despite the changes in the near-term, the overall forecast ideas we presented earlier today still hold. The area most likely to perhaps see some forecast changes because of what Beta is doing right now would be the Matagorda to Freeport area, which could see some slightly stronger winds or slightly higher surge if Beta does indeed strengthen a bit further.

Beta intensifying?

According to the 1 PM National Hurricane Center advisory, Beta still had 60 mph maximum sustained winds, mainly north and east of the center. The reconnaissance aircraft that sampled Beta this morning found ample support for these winds. But over the last 3 hours or so, Beta has clearly begun a burst of intensification.

Beta has clearly improved its structure this afternoon and is likely intensifying a bit. (College of DuPage)

Beta actually looks like a reasonably competent tropical cyclone now. In fact, if you look at radar, you can see a nascent eye-like feature developing. That doesn’t make it a hurricane, but it does mean that it has organized itself, perhaps feeling a brief pause in shear or dry air and the very warm Gulf water it sits over.

Beta has presented an eye-like feature on radar this afternoon. That doesn’t make it a hurricane, but it does indicate strengthening. (GRLevel3)

My guess is that Beta is a strong tropical storm at the moment. But as it approaches the coast, a wall of dry air awaits its arrival. It will be tough to keep that dry air out of the circulation. And the expectation will remain that Beta begins to weaken as it approaches land. That has been the hypothesis since day one, and that still holds true today. The only way that changes is if Beta can insulate its inner core enough from the drier air that is waiting. That’s always a tough call, so we want to continue watching it, but the expectation is that dry air will begin to take a toll on this core later today or sometime tonight.

We discussed our wind forecast expectations in the morning update, and those are unchanged at this time.

Sunday rain

For much of the Houston area, rain has been falling this afternoon, heavy at times. Totals have generally been one inch or less.

Beta’s outer bands are flinging rain, heavy at times, across the area. Most places will end up with less than an inch when this rain tapers off later. (Weathernerds.org)

You can see the outer bands of Beta with some heavier rain indicated in yellow on the loop above. This initial wave of rain should taper off a bit later today, but we will likely continue to see gusty showers or even some thunderstorms at times into tonight.

Total rainfall forecast

NOAA has updated their rainfall forecast for the event total, and they have indeed brought values down a little bit further. It looks like they shaved off about 1 inch in Houston to as much as 3 or 4 inches Galveston. Granted, some rain has already fallen, but not as much as has been removed. So, some good news there.

A view of the updated NOAA forecast rainfall from southeast Texas across Louisiana through Thursday evening. (Weather Bell)

As we’ve been stating, we don’t want folks to just assume this is a non-event; you should remain vigilant in the days ahead. There will be periods of heavy rainfall. But as far as major, widespread flooding, we do not see that scenario as being likely at this time. Still, it may be good to take sensible precautions if you live in a typically flood prone area, particularly with respect to street flooding, just to be safe. In tonight’s update, we’ll offer some thoughts on how Monday’s rainfall may play out.

Marine impacts

We covered this in depth earlier this morning as well. At Galveston, at the railroad bridge near Tiki Island, we saw about 4 foot water levels this morning. Expect that to be about a foot or so higher tonight and end up in the 5 to 6 foot range.

Tides will be rising again soon in Galveston, which should yield another round of widespread minor to moderate coastal flooding. (NOAA)

This will cause widespread moderate coastal flooding along the entire coast and bayfronts as well. Expect that to continue much of tonight and Monday morning, with only a slight drop in tides Monday afternoon, followed by a similar peak in tide levels tomorrow night before things subside. This will be aggravated by 8 to 12 foot seas and higher waves offshore.

That’s all for now. Our next update will be posted no later than 9 pm CT on Sunday evening.

20Sep

Beta drifting toward the Texas coast, mostly status quo this morning

Posted by Matt Lanza at 9:01 AM

9 am CT Sunday: Good morning. The good news, right off the top, is that we’re basically in the same place with Tropical Storm Beta as we were 12 hours ago. Beta is truly struggling right now, dealing with things from dry air to wind shear, all of which make Beta a very lopsided storm. It’s still capable of causing problems, particularly with marine impacts and rainfall at a localized level, but we don’t see the forecast looking any worse today. And in some aspects, it looks better. Let’s swing through things.

Beta now

We will start by looking at the water vapor satellite loop over Texas and the Gulf this morning. The “drier” colors (dark red, brown, orange) that you see over Texas indicate voluminous amounts of dry air over the area. Go step outside this morning. It’s the driest air we’ve had this early in the day since June 11th in Houston. You can see it on satellite, but more importantly, you can feel it outside.

Using the water vapor channel on satellite can show us copious amounts of dry air over Texas that will work to limit Beta’s intensity. (Weathernerds.org)

That will not help Beta at all. In fact, as Beta moves toward the coast, it’s arguably going to encounter even more of this dry air.

Additionally, Beta is sitting under about 15 to 20 knots of southwesterly wind shear. If you look closely at the map below, you’ll see Beta’s forecast track and the shear values in green, yellow, and red.

The moderate wind shear over Beta has not relented, and in fact, it may get stronger as Beta approaches the Texas coast. (University of Wisconsin CIMSS)

As Beta approaches the Texas coast, Beta’s wind shear situation will not get any more favorable, and in fact, it may get worse, with 20 to 30 knots of wind shear over Texas.

So, all this is to say that Beta is unlikely to get any stronger up to landfall. There is probably even some risk it may weaken a bit.

Beta currently has maximum sustained winds of 60 mph, but those are heavily displaced to the north and east of the center. That said, the wind field radius is 195 miles from the center. For a weak tropical storm, that’s a very large wind field. And this is why marine impacts are such a significant issue. More on that in a second.

Beta track & wind forecast

So we talked intensity above. Expect maximum sustained winds to hold at 60 mph or lower as it slides west toward the Texas coast today and tomorrow. Beta’s center will likely stall near or just inland from where it makes landfall on Monday night and Tuesday before resuming movement, this time off to the northeast on Tuesday night and Wednesday. Beta should be through with us by Wednesday night or Thursday.

Beta will track toward the coast tonight and tomorrow, stalling for a time into Tuesday before exiting Wednesday and Wednesday night. (NOAA)

Beta’s actual winds here in the Houston & Galveston areas will vary. North of I-10, winds will probably never exceed 30 to 35 mph and mostly in gusts. There should be few issues with wind there. South of I-10, winds could gust to 45 mph or so, and there’s at least a chance a brief period of sustained tropical storm force winds (39 mph or higher) is achieved in southernmost areas. Still, problems are expected to be minimal and power outages would probably be isolated in this situation. At the coast and along the bayfronts from Matagorda through Galveston and toward Cameron, LA, wind gusts of 35 to 50 mph will be possible at times as Beta moves in tomorrow. More sporadic power outages and perhaps some minor tree damage could occur in those areas. Overall, wind is not expected to be a serious issue for the vast majority of the region.

Beta marine impacts

The most significant problems from Beta will probably be caused by the marine impacts and the combination of heavy rain and high tides. Highway 87 and Blue Water Highway west of San Luis Pass experienced overwash overnight, and with tides expected to be about 1 to 1.5 feet higher tonight into Monday morning, the coastal flooding situation in those areas will only get worse. We will see tide levels at Galveston around 5 feet or a bit higher.

The tide forecast at Galveston is expected to peak late today and early Monday around 5 feet, and then it should hold in the 4 to 5 foot range (or a smidge higher) into Tuesday. (NOAA)

Coupled with 8 to 12 foot seas, we will see tides only drop slightly during low tide, so this will be a problem for several days with continued minor to moderate tidal flooding along the coast and bays. We should begin to see improvement in these areas by Tuesday afternoon or evening.

Beta rainfall forecast

We conclude with rain, the most challenging part of the forecast. Eric and I are going to maintain our flood scale posture of Stage 2 south of I-10 and Stage 1 north of I-10.

Weather models are generally poor at forecasting rain amounts with specificity and exact location, but the one trend that has been undeniable since yesterday has been to take heavier rain on the Texas coast and offshore and shift it more to Louisiana. The current rainfall expectations from NOAA still show high amounts on the coast.

NOAA’s forecast of total rainfall has dropped considerably since yesterday but remains high enough to warrant Flash Flood Watches. (NOAA)

These amounts are down pretty substantially from yesterday, however, now with 10 to 15 inches expected along the coast and 4 to 10 inches of rain in the Houston metro over the next five days. If these change further later today, I believe it will be to shift some of the higher totals more into Louisiana.

That said, this remains a very difficult and challenging rainfall forecast. For today, expect rain bands to begin to pivot into our area. Rain is already approaching Bolivar and Winnie and expect that to continue coming west today.

The outer bands of Beta’s core will begin to approach the coast this morning and afternoon. (College of DuPage)

As we go into tonight, look for continued squally weather with periods of heavy rain and thunderstorms at times, especially south of I-10. We don’t feel that this will be a continuous rain event for the area, but it will come in bursts at times. This is generally good for bayous and creeks to be able to handle the rainfall without a ton of serious trouble. Where this could get a little more bothersome is if the core produces some heavy rain as it moves ashore tomorrow or Tuesday, especially south and west of Houston. That would be the most likely time we see rainfall rates that could cause some issues. But as of now we feel that for the most part the area can handle what is being thrown at it this week. Beyond Monday and Tuesday, there’s still some uncertainty, but pockets of rain are likely and in small areas (size-wise, think over like a couple communities or so) we could see heavier downpours and some more troublesome flash flooding. We’ll be watching all this closely and update you through today and tomorrow and beyond on any changes in potential or any ways we can get more specific about where heavier rain will fall.

In the meantime, we will have our next post no later the 2:30 pm CT Sunday afternoon.

18Sep

Tropical Storm Beta very slowly begins to organize to our south

Posted by Matt Lanza at 8:51 PM

Apologies for being a few minutes late: Toddler life.

So Eric’s post from earlier this afternoon tackled a number of things, including track risks, our flood scale update, and the coastal impacts expected from now Tropical Storm Beta. In this update, I am going to focus primarily on the now and next couple days. We will close with a quick bigger picture update.

Tropical Depression 22 was upgraded to Tropical Storm Beta with the 4 PM advisory package from the National Hurricane Center (NHC). One of their key points, something that seems to be further backed up by the reconnaissance aircraft flying in Beta as I write this, is that the center is both somewhat elongated and seems to be perhaps a bit to the east of where it initially was expected. It’s important that we make note of how these changes in the specific location of the center impact the models over the next 12 to 24 hours. So, a satellite loop of Beta shows a storm that’s more like a “blob” of thunderstorms than a well-defined tropical storm

Beta initially being a blob is in line with what we’ve seen from a lot of storms early on over the last couple seasons. (Weathernerds.org)

But if you look at the data from the Hurricane Hunters in the storm, there are pockets of winds supportive of a moderate tropical storm already. Winds will likely be increased this evening during the 10 PM update to at least 55 or 60 mph. So despite the “blobby” nature of Beta, it’s already fairly formidable. With us heading into the typical nighttime ramp in tropical thunderstorms, we would expect additional gradual strengthening of Beta tonight.

As we go into Saturday, a number of things may happen with Beta’s center. It may come a bit to the north. It may meander not far from where it sits currently, or it may even reform in another section of the storm. It’s for these reasons that the storm track and rainfall impacts beyond the weekend are extra uncertain. We know that at some point tomorrow, Beta will begin to feel the influence of the strong area of high pressure to our north, which will be responsible for the glorious weather we have tomorrow morning.

The surface weather map forecast for Saturday afternoon shows Beta being squeezed south by high pressure over the Eastern U.S. (NOAA WPC)

As that happens, Beta will basically screech to a halt and begin to drift west. And that will be Beta’s M.O through Monday: A slow drift west.

So what does that mean for our weekend? One strategy I have found in the many slow moving storms we’ve had around here in recent years is that it makes the most sense to focus most on what we know, the next 36 to 48 hours, and then touch base at a high level on the future. So let’s do that.

Saturday should start off sunny and pleasant. Look for clouds to gradually filter in during the afternoon, particularly south and east of Houston. A shower or two is possible by evening toward Galveston, Freeport, or Matagorda. No serious weather expected.

On Saturday night, we could begin to see some of the northern outer bands from Beta creep toward the coast, so I wouldn’t rule out a couple periods of showers or storms after midnight for coastal adjacent communities.

As we go through Sunday, look for this chance of storms continue at the coast and gradually spread inland. The way things are lining up right now, I would think we see outer bands on the coast off and on throughout the day. Inland areas may see some scattered storms, and perhaps a more organized, heavier single band of activity pivots across the region east to west through the morning and afternoon. Overall, conditions through Sunday evening should be manageable across the entire area.

Rain totals through Sunday evening should be at most an inch or two along the coast, with lesser amounts inland. (NWS forecast via Weather Bell)

Rain totals by Sunday evening will likely be 1 inch or so on average at the coast, with risk for perhaps up to 2 inches or so between Freeport and Matagorda, right up along the coast. For the Houston metro, we probably range from minimal rain north and west to a quarter or half-inch in the city to perhaps three-quarters of an inch south and east of the city. Again, these are average amounts. Some will see less, some a bit more.

Coastal areas will begin to notice the rough surf and stiff, steady breeze pick up, and coastal flooding is likely to commence by Sunday’s high tide cycles (see Eric’s earlier post for more on that).

Sunday night into next week

Beyond Sunday evening, we expect Beta to approach the coast near Corpus Christi Monday and stall out for a time by Tuesday. This will keep continued periods of rain and storms in our area with breaks likely, but the heaviest rain will stay to our south and west. There is also a chance that heavier rain event could break out well out ahead of Beta. This would be from about central Louisiana into North Texas, away from the Houston area.

A plume of deep tropical moisture straight out of the Pacific, with perhaps some additional contribution from the southwest Atlantic is going to basically converge on Louisiana. You can see this on the GFS forecast of precipitable water for midnight Monday night/Tuesday.

High precipitable water forecast around Beta may direct a distinct band of heavy rain into Louisiana and up north and west into northeast Texas. (Weather Bell)

This has been a more pronounced model wrinkle today that seems to suggest heavy rain will break out east of the Houston area and possibly east of the Beaumont area also. This would direct heavy rain into Louisiana that may perhaps expand and arc north and west into northeast Texas maybe north central Texas as well. The heaviest rain in that situation would stay both to our southwest and east on Monday and Tuesday. I don’t want to say that’s the “likely” scenario here, because a lot can change depending on how Beta is oriented at that time. If the storm is farther inland, that plume could end up much closer to Houston. If Beta is more offshore, we remain on the fringe of the heavier rain chances. So a lot of uncertainty here. We will keep you posted. Beta should begin to exit Wednesday and Thursday. But details are very much TBD at this time.

Eric will have our next update by 9 am CT on Saturday.