Matt Lanza

Potential Tropical Cyclone 1 will potentially bring flash flooding to South Texas and Mexico

10 AM Wednesday update: PTC 1 is now Tropical Storm Alberto. We will have an update early Wednesday afternoon on the rain and surge issues impacting the Texas coast.

Headlines

  • Potential Tropical Cyclone #1 to bring marine impacts and heavy rain to portions of Mexico and Texas over the next couple days where flash flooding is quite possible.
  • Atlantic development remains fairly unlikely east of Florida, but some additional rain chances may arrive there this weekend or next week.
  • A second system, perhaps very similar to PTC #1 will track toward the Bay of Campeche Sunday or next week, bringing additional heavy rain chances into Mexico and/or Texas.

PTC #1 brings the rain tonight and tomorrow to Mexico and Texas

Late yesterday, Invest 91L was given the tag Potential Tropical Cyclone #1. Why? The National Hurricane Center needed to issue watches for a system that had not yet developed into a technical surface low and had winds of tropical storm strength. Basically, it’s their way of saying “We need to alert on this storm, but it hasn’t met meteorological criteria for formation yet.” From an impacts and what you experience on the ground standpoint, little has changed since yesterday.

PTC #1 is expected to become a tropical storm tonight or tomorrow before scooting ashore in northern Mexico. Impacts from PTC 1 will extend far from the storm with low-end tropical storm force winds, rough seas, and torrential rain in the northwest Gulf of Mexico. (NOAA NHC)

We still expect this system to move ashore in northern Mexico sometime tomorrow evening. It will deliver a variety of impacts to Mexico and Texas, including coastal flooding (also in parts of SW Louisiana), rough seas, and gusty (but likely not damaging) winds. Scattered power outages in South Texas can’t be entirely ruled out, but they would likely not be severe.

Moderate to locally major coastal flooding is expected between Cameron, LA and South Padre Island, TX with onshore winds and rough seas elevating tides, likely closing some roads and causing some isolated property impacts. (NWS Corpus Christi)

But the main thing I think to watch with this system will be the rain. Rain will push ashore in Texas and Louisiana later today and later tonight to the south into Mexico. Based on what we see on modeling and satellite this morning, it would seem that the heaviest rains will take aim to the south of Houston, more toward Matagorda Bay and eventually Corpus Christi.

A satellite image from late Tuesday morning shows deeper moisture offshore of Texas, aimed toward the middle and southern coast, particularly from near Matagorda Bay and southward. (College of DuPage)

And indeed, this seems to be where modeling is rather consistently now focusing the heavier rain chances tonight and Wednesday. You can see from the rainfall map below that we’re expecting anywhere from 2 to 4 inches in the Houston area to 6 to 10 inches near Corpus Christi. I included the plus sign in my annotation on the map because the reality is that there will likely be embedded higher amounts anywhere in the entire region, depending on exactly where any banding features setup, a forecast that’s impossible to pin down more than a couple hours in advance.

Rain totals will peak on the middle Texas coast with anywhere from 6 to 10 inches and locally higher amounts from just south of Corpus Christi up through Matagorda Bay. (NOAA)

Flood Watches are in effect for the entire Texas coast, RGV, and South Texas. Most of this rain will be welcome in interior Texas, where it has been quite dry. The rain in Mexico will hopefully be manageable, but as always in the mountains, we’ll need to watch for mudslides. Some fairly intense rain is also possible on the southern periphery of PTC 1’s circulation, delivering heavy rain to Central America, including 16 to 20 inches (400 to 500 mm) to portions of El Salvador and Honduras.

Significant rain is likely for Central America as well, with portions of Nicaragua, Honduras, El Salvador, and Guatemala seeing impressive totals. (NOAA)

Travel tomorrow may be difficult across South Texas, so expect to run into delays or flooded roads. Conditions will improve a bit on Thursday and especially Friday. For the latest on Houston conditions, visit our Space City Weather site.

Southwest Atlantic system

Meanwhile, we continue to keep tabs on the disturbance in the Atlantic that the NHC gives about a 20 percent chance of developing over the next week. This one is likely to be a nothingburger for the Southeast and Florida and may just serve to elevate rain chances a bit this weekend or next week.

Southwest Gulf of Mexico: Take two

As we see PTC 1 exit late this week, quieter weather will build into the Texas and Mexico coasts, with just some isolated to scattered daily thunderstorms. But then by later in the weekend or early next week, we may get almost a carbon copy of this system: Likely lower-end in intensity, moisture-laden, and tracking toward northern Mexico. The problem will again be rainfall I think. While much of the rain from PTC 1 is welcome and will soak in, if a second system follows suit, the math gets a little more challenging.

Heavy rain is possible again, as you can see from rainfall anomalies between Saturday and Friday of next week on the GFS ensemble. (Tropical Tidbits)

Currently, the heaviest rain is expected to fall just south of where PTC 1’s rains will hit hardest. However, it is far enough out in time and with enough uncertainty to think that we will see things change with this. Interests along the lower Texas coast and in Mexico will want to monitor the next system’s progress closely, particularly with respect to the rainfall outlook. We’ll keep you posted.

Elsewhere, things look fairly quiet with no other systems of note at this time.

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South Texas flooding risks increase this week as near record amounts of atmospheric moisture plow ashore

As of Tuesday Noon, a new post has been updated: Potential Tropical Cyclone 1 will potentially bring flash flooding to South Texas and Mexico – The Eyewall

Headlines

  • A developing flash flood threat will occur in Texas this week, with heavy rain between Houston and Brownsville. Heaviest rains seem likely between Matagorda Bay and Corpus Christi.
  • Invest 91L in the Bay of Campeche continues to show signs that it will develop into a lower-end system before coming ashore in northeast Mexico midweek.
  • An Atlantic disturbance may approach the Southeast coast later this week, with low odds of lower-end development.
  • An additional system or large area of rainfall may impact Texas and Mexico again next week.

Texas axis and Invest 91L

The focus for this week will be very much on Texas and Mexico as impacts from a combination of a long axis of atmospheric moisture and a possible Bay of Campeche tropical system work to deliver heavy rainfall to parts of the region.

The current rainfall forecast as of Monday morning for the upcoming week. Most of this will fall Tuesday night through Thursday morning. (Pivotal Weather)

The rainfall forecast for this system will be tricky. Much like was witnessed in Florida last week, plentiful amounts of moisture in the atmosphere will lead to efficient (read: heavy) rainfall production. Put simply? The potential for some very high rain rates will be in play for the entire Texas coast this week. While the amounts above are a good average for the period, there will almost certainly be higher amounts in spots.

The amount of moisture available in the atmosphere on Wednesday will be near record levels on much of the Texas coast. (Tomer Burg)

The biggest question we are faced with as forecasters is where those higher totals will occur. All weekend, we’ve seen some changes here and there in terms of where the “bullseye” of heavy rain will occur. In general, it looks focused on the Matagorda Bay region south into Corpus Christi, with locally heavy rain but gradually decreasing totals on either side of that. Given the moisture situation, we could easily see 10 to 15 inches in the most persistent bands, possible anywhere, but again most likely between Matagorda and Corpus Christi. Flash flooding will be a good bet in those areas, so please travel cautiously in coastal Texas this week.

In addition, coastal Mexico and the mountains south of the Rio Grande will likely see elevated totals, perhaps as high as 10 inches or so. Flash flooding is a good bet in parts of Tamaulipas and Nuevo Leon.

Conditions should gradually improve Thursday and Friday. Quick note: We are getting a lot of questions about vacation plans, flights, etc. We can’t get to all of those, so just use your best judgment and heed the advice of local officials around your travel. Prepare for at least some delays the next couple days.

In terms of tropical development, Invest 91L is what’s spinning in the Bay of Campeche and has a 70 percent chance of developing into a tropical system. Hurricane hunters will be out to investigate the system later today.

Invest 91L has a broad circulation associated with it over the Bay of Campeche. We’ll see what data is snatched up this afternoon when it’s investigated by the Hurricane Hunters. (Tropical Tidbits)

It seems that 91L has a broad circulation overall, mostly in the mid-levels of the atmosphere. To get declared as a tropical system, we’ll need a low-level circulation and low pressure at the surface. It’s got a little time to do this before it nudges inland over northeast Mexico midweek. Regardless of development, the broad southeast flow to the north side of it will help amplify the rain chances in South Texas and northern Mexico.

Southwest Atlantic rumblings

A disturbance sitting north of Puerto Rico will continue to backpedal to the west over the next few days, eventually approaching the Southeast U.S. coast by Friday or Saturday. It has about a 30 percent chance of developing right now, which seems reasonable given the amount of wind shear it will likely experience in the days ahead.

As the Atlantic disturbance tracks toward the Southeast coast, it is likely to run into a fair bit of wind shear that will likely serve to cap development and intensity chances. (University of Wisconsin CIMSS)

This remains an area to keep watching, but given the setup, it also seems likely that this will have a fairly low ceiling in terms of intensity and organization. The best guess for track would be toward Georgia or South Carolina, with perhaps some added rain up that way later this week.

Texas & Mexico rinse and repeat?

We continue to also keep tabs on the potential for a follow-up round of rain and low-end tropical development next week off the Gulf Coast. Models continue to indicate continued Central American gyre activity near the Yucatan and Bay of Campeche. The pattern will finally break down later next week, with high pressure likely building into the Gulf of Mexico. But before that happens, we could see another disturbance associated with the CAG begin to track into Mexico or South Texas. This shows up nicely when you look at the “spin” in the mid-levels of the atmosphere as forecast by the European ensemble model between this weekend and next Thursday below.

As the Central American gyre begins to get displaced and breaks down next week, one more round of heavy rain may get forced ashore on the Texas or Mexico coasts. (Tropical Tidbits)

It’s far too soon to figure out exact details here. But what we see: A CAG that begins to move and break down, the potential of a tropical system forming within that mess, and a strong signal for above normal rainfall, if not much above normal rainfall again next week in Mexico and South Texas. We’ll continue to watch this closely, especially after one round of heavy rain this week.

Western Gulf Coast to get soaked from major moisture plume as potential new system moves toward Florida

A happy Father’s Day to those celebrating today! We’re here on Sunday with the latest for you on what continues to be an active June in terms of impacts.

Headlines

  • Tropical development is very possible in the Bay of Campeche this week.
  • Regardless, the pattern supports a very heavy rainfall threat for the Texas and Louisiana coasts into Mexico as well, with flash flooding becoming increasingly likely.
  • A new disturbance may track toward Florida late in the week, but most impacts should be north of the areas worst impacted by last week’s rains.
  • Another western Gulf system is possible after this week with more rain in Texas.

Potential for widespread heavy rain and flooding in coastal Texas

The main story from an impacts perspective this week will almost certainly be the situation in the western Gulf of Mexico. We are still monitoring the potential for development from a system in the Bay of Campeche this week.

The National Hurricane Center continues moderate odds (60%) for development this week in the Bay of Campeche. (NOAA NHC)

The chances are fairly modest still, up to around 60 percent, and it would appear that any development should have a pretty low ceiling for intensity. The system should be inland over Mexico by Wednesday or early Thursday.

European ensemble members show a likely track of whatever forms in the Bay of Campeche to be toward the coast of Mexico and inland by later Wednesday or early Thursday. (Weathernerds.org)

The problem is that the overall pattern into the western Gulf remains extremely favorable for heavy rainfall over a very wide area. Extremely deep tropical moisture will be pushing in over top of the tropical low that moves into Mexico. This will crash into Texas on Tuesday and especially Wednesday. The forecast for precipitable water, or the amount of moisture available in the atmosphere will be running near both daily historical maxes and potentially all-time record levels for the Texas Coastal Bend. This means that rain will be efficient and heavy.

Rain totals over the next 7 days will potentially exceed a foot on the Texas coast, with lesser but still hefty amounts possible inland. Flash flooding is likely in spots and at times, especially Tuesday night and Wednesday when most of this falls. (Pivotal Weather)

Rain totals have been escalating all weekend and it now appears that perhaps a foot or more rain may fall on the Texas coast. Lesser amounts are likely inland, but they will still be heavy, and it cannot be stated more plainly that flash flooding and potentially serious flash flooding is possible anywhere between Beaumont and Brownsville, depending on exactly where the heaviest rainfall orients.

The Weather Prediction Center has already highlighted the Texas and western Louisiana coasts for a moderate risk (level 3/4) of heavy rainfall on Tuesday. (NOAA WPC)

A moderate risk (level 3/4) of excessive rainfall and flooding is already in place for portions of Texas and Louisiana on Tuesday, including Houston, Galveston, and Beaumont. Suffice to say, this is yet another example of potentially a low-end storm or nameless storm that can produce significant rain and flooding impacts. Folks in Texas and southwest Louisiana should monitor forecast developments closely today and tomorrow. Stick with Space City Weather for those in Houston for the latest.

A new disturbance tracks toward Florida or the Southeast this week

We left you on Friday with the idea that the focus would move to the western Gulf. What has changed since Friday is that a new tropical disturbance seems likely to form north of the Bahamas by Tuesday. The good news is that this will quickly track west, arriving in or near Florida by Thursday and eventually inland through the Southeast.

A new tropical disturbance will likely form north of the Bahamas and track toward Florida this week. (Tropical Tidbits)

The NHC has a 30 percent chance of development with this one as it tracks west. It would seem that whatever forms will probably be lower-end in nature, but given the amount of rain that recently fell in Florida we’ll obviously want to watch this closely. At present, most model guidance seems to favor it tracking toward areas north of the Space Coast. In that case, South Florida will be fine, with most heavier rain falling toward Jacksonville, Georgia, or South Carolina. As always, it will be good to monitor things the next couple days just to make sure everything behaves with this one.

Beyond this week

It still appears that another system may try to form, spiraling around the Central American gyre next week. Details remain uncertain, but it’s pretty evident that modeling supports a continued rainy pattern in Texas.

Rainfall of 200 to 500 percent of normal is likely on the Texas coast next week as well, which could further exacerbate flooding issues. (StormVista Weather Models)

Both the GFS and European ensemble members shown above indicate agreement on about 200 to 500 percent of normal rainfall for the 8 to 14 day period. This would be 1 to 2 inches more rainfall than usual, on average. So we’ll need to continue monitoring Texas and Louisiana for potential flooding concerns into next week too.

Outside of the western Gulf it looks quiet, and hopefully that area will begin to quiet down a bit too after next week.

Focus on Florida will shift away this weekend, as western Gulf gyrates with activity next week

Headlines

  • Florida rains will slowly subside the next couple days.
  • System likely in the Bay of Campeche next week, probably lower-end and heading quickly into Mexico.
  • Heavy rain around a broader easterly flow in the Gulf will become increasingly likely on the Louisiana, Texas, and Mexico coasts later this weekend and next week.
  • Additional rain and additional lower-end tropical development is possible the week of June 24th in Texas and/or Mexico.

Florida still soggy

Yesterday’s rains weren’t quite as bad as what we saw on Wednesday, but at this point, it’s just a lot of water and time for a break in Florida. More storms have fired up this afternoon and locally heavy downpours are likely between the southwest coast the urban corridor on I-95.

Scattered heavy downpours and localized flooding remain possible into this evening across much of South Florida. (GR Level 3)

The entire southern half of the Peninsula has seen north of 3 or 4 inches of rain this week, with 10 inches or more over a wide swath across Alligator Alley and spotty 15 to 20 inch totals in a few locations. We’ll see another half-inch to inch with locally higher amounts possible through tomorrow. The clean up can hopefully get underway in earnest after today or tomorrow.

CAGgy consternation in the Gulf

We continue to see plentiful signs that a weak system will develop in the Bay of Campeche next week.

About a 50/50 chance of development exists next week in the Bay of Campeche with any system likely ending up lower end and heading for Mexico. (NOAA NHC)

The National Hurricane Center continues to assign about 50 percent odds of development next week from this disturbance, which is currently just developing on the Pacific side of Central America. It will become embedded in this Central American Gyre (CAG) setup over the Yucatan which is a common pathway to development in June. You can learn more about CAGs here, which is a pretty well-put together article.

Anyway, the path for this feels pretty straightforward again today, with the expectation that it will produce a middling system that tracks around the Yucatan and west or west-northwest into Mexico next week.

Western Gulf’s turn to get soaked

Any direct impacts from a tropical system will likely be confined to the coast of Mexico near where it comes ashore. But broadly, this pattern is going to continue to produce a long “fetch” of moisture across the Gulf of Mexico.

Forecast from the European model for precipitable water next Wednesday. A lot of moisture will make its way to the Texas and Mexico coasts. (Pivotal Weather)

The map above shows precipitable water for next Wednesday, which is a measure of how much moisture is in the atmosphere. Values north of 2 inches like we see plentifully in Texas and Mexico usually produce locally heavy rainfall. And indeed, the rainfall forecast for the Texas, Louisiana, and Mexico coasts is pretty significant.

Total rainfall through next Friday totals around 4 to 8 inches on the coast from Louisiana into Mexico, with locally higher amounts possible. Rain totals will drop considerably as you move inland. (NOAA WPC)

I will emphasize for our Louisiana and Texas readers that this will potentially be a very sharp rainfall gradient. In other words, you could see 6 to 10 inches of rain on the immediate coast in, say, Galveston versus a more manageable 2 to 5 inches or so in Houston. So the highest impacts will very likely be on the literal coast. Same goes for Corpus Christi, Brownsville, and the Louisiana coast. Mexico is likely to see more widespread rainfall due to terrain considerations and their proximity to the tropical system, whatever it becomes.

Beyond next week?

A second system may follow as the CAG begins to break down the week of June 24th. You can safely ignore some of the silly GFS operational model solutions for now. But it appears that something is there. That system may or may not develop, which is to say that we don’t currently think this is going to be a huge deal. That said, the wet pattern into Mexico and southern Texas is likely to continue into that week.

The rainfall outlook from both the GFS (left) and Euro (right) ensemble models suggests rain totals of 200 to 400 percent of normal near the Texas and Mexico coasts from next Friday through the following Friday, June 28th. (StormVista Weather Models)

With about 200 to 400 percent of normal rainfall expected on the Texas and Mexico coasts, we may begin talking more about flooding for some areas. Heavy rains may also linger to the north. More on this next week.

We’ll take a breather tomorrow and come back on Sunday with the latest!