Month: September 2020

6:55 am CT Monday: Good morning. The overall situation with Tropical Storm Beta remains the same. Coastal regions are seeing very high water levels due to tides, surge, and prolonged easterly winds from Beta. We’re expecting intermittently heavy rain over the next few days in the greater Houston region, but we do not anticipate widespread flooding issues. Before diving deeper into the forecast I wanted to allay any lingering fears about a slow-moving tropical cyclone making landfall south of Houston.

We’ve been saying for days this will not be another “Harvey” for the area due to a variety of factors, including dry air over the state. We realize many of our readers have PTSD after that nightmare storm, and that’s why we created our flood scale messaging. As we have done since Friday, we’re still forecasting a Stage 2 event for the coast, and Stage 1 for inland areas. Rest assured, if another Harvey like-system approaches Texas, we will tell you. We’ll be shouting about a Stage 5 flood from the rooftops. This is not that, however. A radar image of Beta this morning (left) and Hurricane Harvey in 2017 shortly before landfall tells the entire story.

Beta summary

The storm has weakened over night, and now has sustained winds of 50 mph. It is moving slowly to the west, and will likely make landfall along, or south of Matagorda Bay later today or early Tuesday. The storm is continuing to battle moderate wind shear and the entrainment of dry air into its circulation. These factors are unlikely to change much as the storm nears the coast, and the National Hurricane Center anticipates it will remain at its current intensity until landfall. After this time it should slowly weaken as it tracks inland, or along the coast, before exiting to the northeast on Wednesday or Thursday.

Immediate threat

The most pressing problem at the moment is tidal surges along the upper Texas coast and along nearby waterways. Tides are running 4 feet or more above normal along the coast and locations such as Clear Lake, and affecting nearby roadways. Tides will remain high today and tonight before perhaps receding a bit on Tuesday, and likely considerably more on Wednesday. Take care on low-lying roads.

Rainfall potential

Due to the aforementioned dry air, we do not expect prolonged periods of heavy rainfall across most of the area, however we cannot rule out some training rainfall in isolated areas. Between now and Wednesday, our best guess remains that areas south of Interstate 10 will generally see 2 to 6 inches of rainfall, with areas north seeing 1 to 4 inches. However we probably will end up seeing some 10-inch bullseyes over the region. There may be some spotty flooding associated with this, but for the most part our area’s bayous can handle these kinds of rains. We’ll remain vigilant for any changes to this forecast.

Winds

Winds over the area likely reached their maximum extent early this morning—Galveston Fishing Pier reported a gust of 49 mph shortly after midnight—and should gradually wane later today. As we’ve been stating, Beta is a not a significant wind threat.

Weather ahead

Both Monday and Tuesday will see a high chance of rain, as bands of rainfall from Beta move onshore. Some training will be possible, but there also should be breaks between rainfall. Our biggest concerns for heavy rainfall are in Brazoria and Galveston Counties, where roads near the coast may already be submerged. Please do not drive into high water today. Highs likely will range from the upper 70s to low 80s. It’s worth noting that Sunday’s high temperature of 78 degrees was Houston’s coolest day since May 9th.

Wednesday should be somewhat of a transition day as Beta lifts away, to the northeast. We probably will see some trailing showers, but the threat of very heavy rainfall should have ended by then.

Thursday, Friday, and Saturday

The second half of the week should see the return of sunshine and, accordingly, highs in the 80s or low 90s. It will be a good time for the region to dry out

Cold front?

Our best global models indicate that a reasonably strong cool front will push into Houston early next week, perhaps around next Monday or Tuesday. It’s still a long way off, but the signal for this front is reasonably strong—we’re hoping to be able to celebrate Fall Day around before the end of the month, when nighttime temperatures in Houston fall to 65 degrees or cooler. So, fingers crossed!

Our next post will come no later than 2:30pm CT Monday.

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 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.

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.

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.

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.

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.

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.

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.

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’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.

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.

Overall our rainfall forecast has not changed. We are calling for a Stage 2 flood event for areas south of Interstate 10, and a Stage 1 event for areas north of the freeway. Be wary, not worried. pic.twitter.com/jXLmfZckPs

— Eric Berger (@SpaceCityWX) September 20, 2020

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.

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.

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.