Nobody Is Ready For What Is Currently Forming In The Gulf...

[00:00:00]Three National Weather Service forecast offices looked at the same patch of the Gulf of Mexico on the same morning and published three different answers. One says it dies. One calls it the biggest uncertainty on their board. One says it may come west toward Texas, where rivers are already approaching their flood of record. The system has a 60% chance of becoming a tropical storm, and the next name on the Atlantic list is already waiting.

[00:00:21]In the next few minutes, you will understand exactly what decides which of those futures happens and what to watch for.

[00:00:30]There is a low pressure system sitting in the northeastern Gulf right now, roughly due west of Tampa, Florida. And as of yesterday morning, the National Hurricane Center put its chance of becoming a tropical cyclone at 60%.

[00:00:41]That number comes from the Weather Prediction Center's national forecast discussion, issued at 4:00 in the morning Eastern Time yesterday, and it is the only official development probability attached to the system. 60% better than a coin flip, well short of a certainty.

[00:00:55]The system has a designation. It is called Invest 91 in the Atlantic basin. An invest is an area of disturbed weather that forecasters have formally tagged so that specialized computer models and data collection can be pointed at it. The numbers 90 through 99 cycle through repeatedly over the course of a season.

[00:01:12]The designation itself means nothing about how strong the system will get or where it will go.

[00:01:17]It means somebody with authority decided this thing was worth watching closely.

[00:01:21]What it does not have is a name, a category, a wind speed, or forecast track that anyone is willing to stand behind.

[00:01:28]Here is the 8:00 advisory language from the National Hurricane Center yesterday morning, word for word. They describe it as an area of low pressure located over the northeastern Gulf that, quote, continues to become better defined, end quote, with associated shower and thunderstorm activity that, quote, is gradually increasing, end quote. Better defined.

[00:01:46]Gradually increasing.

[00:01:48]Those are the words of an agency watching something slowly assemble itself and declining to guess what it becomes.

[00:01:54]And that is where the story actually starts because the reason the system is worth your attention is not the intensity it might reach. It is currently a disorganized swirl of convection with a marginal chance of becoming a low-end tropical storm. If you are waiting for someone to tell you a hurricane is coming, nobody is telling you that. The reason it matters is that the professional forecast community cannot agree on where it goes, and the disagreement is not a minor difference of a hundred miles.

[00:02:20]It spans the entire northern Gulf coastline from the Florida panhandle all the way to the Texas coast.

[00:02:28]Three separate National Weather Service Forecast Offices looked at the same system on the same morning using the same data and published three materially different readings of what it is going to do. Start with Miami. The Miami office expects the low to be absorbed and to disappear. Their short-term discussion describes the upper-level low in the northeastern Gulf as remaining rather stagnant, stuck between a ridge off to the west and an elongated trough across the northeast United States.

[00:02:53]Their expectation is that by today, the low decreases in intensity while eventually getting, in their words, "sucked up into the upper-level troughing pattern across the northeast."

[00:03:03]Their stated worst-case scenario is that it becomes a tropical depression while it fades out early this week. They expect no major impacts for South Florida at all. Now, go north and west to Birmingham, Alabama.

[00:03:13]That office treats this same system as the single dominant uncertainty in their entire forecast. They call Invest 91L a broad, disorganized tropical disturbance which remains a primary source of uncertainty. They note that model guidance remains split with their leading scenario keeping the system south of their area and out in the Gulf.

[00:03:32]So, one office says it dies. A second office says it is the biggest question mark on their board. Then, there is Fort Worth, Texas. And Fort Worth raises the possibility that this thing comes west toward them.

[00:03:44]Here is their long-term discussion quoted directly because the precise wording matters enormously. They write that they will be monitoring the current tropical disturbance.

[00:03:53]Invest 91L over the next few days as some of the mesoscale hurricane models highlight the potential for the upper ridge to steer this disturbance toward the western Gulf during the second half of the work week.

[00:04:04]And then this sentence, quote, "None of the global models are picking up on this scenario yet, so for now it is just something to watch." end quote. That last line is the heart of everything you need to understand about this system.

[00:04:19]Before we get into what that model disagreement means, you need to understand why this system has not become a storm already because on satellite it looks like it should have.

[00:04:28]The convection is impressive. The thunderstorm activity has been increasing for days. There is visible rotation. And none of that is the thing that matters. A tropical cyclone is a warm core system that pulls its energy directly out of the ocean surface. To do that, it needs a closed circulation at the surface. A defined center at sea level that air spirals into, rises through, and vents out the top.

[00:04:51]Without that surface center, there is no engine. There is just a large, loud, disorganized pile of thunderstorms.

[00:04:58]What forecasters have been seeing over the last few days is mostly mid-level and upper-level spin. A system can look beautifully organized from above while having nothing holding it together at the bottom.

[00:05:08]That is the gap between looking like a storm and being one. And it is the reason you keep hearing careful, hedged language instead of a forecast track.

[00:05:17]There has been movement on that front.

[00:05:18]The Miami office reported that the latest scatterometer wind data, that is satellite instrumentation that measures wind at the ocean surface, appears to show a surface low pressure circulation due west of the Tampa area.

[00:05:30]They noted that the near surface circulation, the low, began to exhibit early yesterday morning, is likely to continue through the next couple of days. So, the surface center may be forming. That is the single most important development in this entire story. Because a system with a surface center is a system that can start using the Gulf as fuel.

[00:05:51]Working against it is a weak Saharan air layer sitting over South Florida. That is a dry, dusty mass of air that travels west off the African continent and rides across the Atlantic.

[00:06:01]Miami describes it as creating dry pockets in the atmospheric column. When dry air gets entrained into a developing tropical system, it chokes the deep convection that development requires.

[00:06:12]Every thunderstorm tower that tries to build gets undercut.

[00:06:15]There is a broader factor working against it as well.

[00:06:18]The oceanic Niño index for the April through June period came in at plus 0.98, which meets El Niño criteria, and the status is listed as warming.

[00:06:27]El Niño conditions in the Pacific typically increase wind shear over the Atlantic basin, and increased shear is hostile to tropical development. It is one of the reasons a system this marginal has spent days looking impressive on satellite without closing off a center.

[00:06:41]That is the current state of play.

[00:06:43]A center that may be assembling dry air trying to tear it apart, and a background pattern that is not doing it any favors.

[00:06:53]Now, the geography.

[00:06:54]Because a weak system does not choose its own path.

[00:06:57]A strong hurricane is deep enough to be steered by the flow high up in the atmosphere and can push its way through a pattern. A weak, shallow disturbance like this one is a passenger. It goes wherever the surrounding flow carries it, and right now it is caught between two features pulling in opposite directions.

[00:07:13]To the west, there's a ridge, a dome of high pressure. To the northeast, there is an elongated trough draped across the northeastern United States.

[00:07:21]The Miami office describes the low as stuck between the two and says it will struggle to propagate away from its current location in the near term. If the trough wins, it reaches down, grabs the system, and pulls it northeast into the broader flow. That is not a track.

[00:07:36]That is a death sentence. Shear tears the circulation apart, and the system dissolves into a plume of moisture that rains on somebody and disappears.

[00:07:44]The Boston office actually notes this outcome downstream saying the next northern stream disturbance draws tropical moisture northward from the northeast Gulf tomorrow into tomorrow night.

[00:07:54]That moisture reaches New England whether or not the system ever becomes a storm.

[00:07:58]If the ridge wins, something very different happens. The ridge acts as a wall to the north and the system slides west underneath it, not along the northern Gulf over water that is exceptionally warm in the third week of July.

[00:08:10]And instead of running out of runway, it gets days. The Houston and Galveston office flagged exactly this.

[00:08:16]They note that a portion of the mid-level troughiness across the eastern Gulf breaks off and slides under the ridge toward the western Gulf coast toward midweek. They add that most deterministic model data suppresses this offshore, but that there remains a subset of guidance suggesting some potential for development. One atmospheric decision, two completely different outcomes, and nobody gets to know which one is coming.

[00:08:40]Return to that Fort Worth sentence because it describes something genuinely unusual.

[00:08:45]Some of the mesoscale hurricane models are showing a westward track. None of the global models are showing that scenario at all. Those are two different families of computer model, and understanding why they disagree tells you exactly how uncertain the situation is.

[00:08:58]Global models simulate the entire atmosphere of the planet at once. To do that in a reasonable amount of computing time, they use coarse grid spacing. The atmosphere gets divided into relatively large boxes. That works well for large-scale features, a ridge, a trough, a jet stream.

[00:09:14]It works poorly for small compact systems because a developing tropical low can be smaller than the model's ability to resolve it. The model effectively smooths it away.

[00:09:23]Mesoscale hurricane models run at far finer resolution over much smaller area.

[00:09:28]They can represent a tight compact circulation that a global model never builds in the first place. So, when they disagree on a marginal system, the disagreement is usually about existence, not just position.

[00:09:39]The high resolution models are steering a storm that the global models have not created. The global models are not arguing that the storm goes somewhere else. They do not have a storm to argue about. This is why routine forecast spread is not the right description.

[00:09:52]This is a structural disagreement about which steering feature wins.

[00:09:56]And it will not resolve through more model runs. It resolves when the system either consolidates a center or fails to.

[00:10:03]And notice what Fort Worth did with that. They published the scenario that has the least model support. And they published it while explicitly saying no global model backs it up. That is a forecast office putting the unpopular possibility on the record rather than burying it.

[00:10:20]Independent forecast discussion circulating yesterday laid out a three branch framework for the system. And while the specific probabilities attached to those branches were not issued by the National Hurricane Center and should not be treated as official, the structure itself is a useful way to think about it. Branch one, the system tracks into the Florida panhandle, development unlikely. It comes ashore as a wet, disorganized mess, drops heavy rain, and never gets a name.

[00:10:43]Branch two, treated as the most probable outcome, the system tracks toward the New Orleans or Pensacola area and arrives as a low-end tropical storm, named Modest, mostly a rainfall event. Branch three, the low probability branch. The system tracks west toward the Houston area. And this is the only branch that produces a strong tropical storm or a hurricane.

[00:11:03]There's a physical logic underneath that ranking. The further west and south the center tracks, the more development potential it has, because a westward track buys more time over open, warm water before the system encounters land.

[00:11:14]Distance from the coast is fuel. The branch that keeps it offshore longest is the branch that lets it grow. So, the least likely outcome is also, by a wide margin, the worst one. That is an uncomfortable shape for a forecast to have, and it is why the Fort Worth office is watching rather than dismissing.

[00:11:29]There is already evidence that the system is capable of producing real weather without any of those branches resolving.

[00:11:35]The Tallahassee office issued two special marine warnings on the morning of yesterday covering Apalachee Bay, the waters from the Ochlockonee River to Apalachicola, from Mexico Beach to Apalachicola, and from the Okaloosa and Walton County line to Mexico Beach extending out 20 and 60 nautical miles.

[00:11:51]Special marine warnings are short-fuse products. They get issued when convection reaching the coast is strong enough to threaten boats immediately.

[00:11:58]That is an unnamed un-categorized disturbance already generating warnings on the water.

[00:12:03]One more piece of official caution worth noting.

[00:12:05]Regardless of whether this system ever organizes, the Weather Prediction Center is maintaining marginal risk areas for excessive rainfall from the coastal southeast and northern Florida through the central Gulf Coast with flash flooding possible Wednesday and Thursday. The rain is coming either way.

[00:12:20]Only the label is in question.

[00:12:24]If the system does close off a surface center and reach tropical storm strength, the next name on the Atlantic list is Bertha.

[00:12:31]The season's first named storm, Arthur, formed on June 17th.

[00:12:35]There's something strange about that arrangement. The name is already assigned. It has been sitting on a list for years waiting for a storm to claim it. Meanwhile, the thing that might claim it is an unnamed swirl of convection that three forecast offices described three different ways on the same morning.

[00:12:49]The certainty of the name against the uncertainty of the storm is the oddest feature of this whole event and it points at something worth understanding about how tropical forecasting actually works.

[00:12:59]The naming system is administrative. It is a communication tool designed so that emergency managers and the public have a single unambiguous label to attach warnings to. It says nothing about danger. A named low-end tropical storm can be almost a non-event. An unnamed disturbance that stalls over saturated ground can kill people.

[00:13:17]The name is not the threat. The rainfall, the storm surge, and the ground it lands on are the threat.

[00:13:23]Which brings us to the second half of this story because the same atmospheric setup that decides the fate of this Gulf system is simultaneously doing something else entirely several hundred miles to the north and it is doing it today.

[00:13:38]That trough across the northeastern United States the one that might reach down and destroy the Gulf low is not sitting still.

[00:13:46]It is part of a broader pattern that is producing a multi-day severe weather threat across the middle of the country and today is the peak of it. Yesterday was the setup. The Storm Prediction Center issued a slight risk covering the Dakotas into western Minnesota and a second slight risk from North Georgia into southern Virginia. Over the Dakotas model showed between 1,500 and 3,000 joules per kilogram of instability by mid-afternoon sitting underneath 70 to 90 knot winds at the 200 millibar level.

[00:14:12]Effective shear around 40 knots supported supercells right out of the gate.

[00:14:17]The Storm Prediction Center warned of very large hail 1 to 3 and 1/2 inches in diameter. Toward evening they expected outflow and storm mergers to consolidate everything into a severe wind producing linear cluster over eastern North Dakota into adjacent South Dakota and Minnesota with peak gusts in the 60 to 85 mile per hour range.

[00:14:36]The Bismarck office was blunter about it warning of hail as large as 2 inches damaging winds up to 70 miles per hour and a possible tornado.

[00:14:44]That was yesterday.

[00:14:46]Today is the enhanced risk.

[00:14:50]The Storm Prediction Center's day two outlook issued just after midnight Central Time yesterday placed an enhanced risk level three on a five level scale across far southeastern Minnesota northeastern Iowa northern Illinois all of Wisconsin and the upper peninsula of Michigan.

[00:15:08]That is today.

[00:15:10]Their summary reads that severe thunderstorms are probable across portions of the upper Midwest and Great Lakes vicinity with swaths of damaging winds the most likely hazard and isolated large hail as well.

[00:15:22]The mechanics.

[00:15:23]An upper shortwave trough over the northern plains strengthens as it moves east and southeast.

[00:15:29]Most guidance shows 50 to 60 knots at 500 millibars with the flow lower down potentially increasing past 40 knots by late afternoon.

[00:15:37]A surface low deepens as it shifts east across Ontario and the northern Great Lakes and a trailing cold front sweeps east and southeast through the afternoon and evening.

[00:15:46]Ahead of that front is a very moist air mass with dew points in the 70s.

[00:15:50]Inside that moisture, the Storm Prediction Center forecasts what they describe as strong to extreme instability, particularly from Iowa into Wisconsin. Their assessment, quoted directly, supercell wind profiles are evident in forecast soundings.

[00:16:03]A favorable thermodynamic and kinematic environment could support initial supercells capable of all severe hazards and possibly significant severe.

[00:16:12]Then, the escalation.

[00:16:14]Given the progressive nature of the upper trough and surface cold front, upscale growth into one or more bowing mesoscale convective systems appears possible and significant damaging wind potential increases with a transition to linear storm mode.

[00:16:28]If a mature complex develops during the evening, the severe wind risk could persist into portions of lower Michigan, northern Indiana, and northwestern Ohio overnight.

[00:16:36]The Milwaukee office has already told spotters they may be needed this afternoon and evening with all severe weather hazards possible.

[00:16:44]And the connective tissue back to the Gulf is exact. The upper trough generating this outbreak is the same feature that determines whether the Gulf system lives or dies.

[00:16:53]The storms over Wisconsin today and the storm that may never form off Tampa are two outcomes of one atmospheric configuration.

[00:17:00]There is a further wrinkle the Storm Prediction Center flagged themselves.

[00:17:04]They note that uncertainty remains concerning the placement of ongoing convection early today, which depends on how yesterday's storms evolved overnight and on the timing of a lead shortwave impulse.

[00:17:15]Tomorrow's threat in the Ohio Valley then depends on how today's complex evolves. Three consecutive days of forecast chained together, hinging on storms that had not formed when the outlooks were written. For tomorrow specifically, the official extended language calls for scattered severe thunderstorms across parts of the Ohio Valley in the afternoon and evening, likely as one or more line segments organizing ahead of the advancing cold front with damaging winds possible until the front moves offshore Wednesday evening.

[00:17:41]Some independent forecasters expect that risk category to be raised. As of the official product, it has not been.

[00:17:50]Now, go back to that low probability westward branch, the one that carries the system toward the Texas coast, and look at the ground it would be landing on. Texas rivers are already in trouble, not forecast to be, already. The Nueces River near Asherton in Dimmit County is under a flood warning that runs until Thursday afternoon.

[00:18:07]The National Weather Service office in Austin and San Antonio wrote yesterday morning that major flooding is occurring and major flooding is forecast, and then added this sentence, quote, "This approaches the flood of record." End quote. At 31 ft, the Nueces River and Turkey Creek are a mile and a half wide.

[00:18:24]Downstream at Cotulla, major flooding is forecast from this afternoon until further notice. The Frio River at Tilden, major flooding forecast from this morning until further notice. The Frio near Derby is in moderate flooding where the official impact statement notes that major flooding reaches the lowest homes and businesses downstream in Tilden, and hundreds of livestock are trapped.

[00:18:44]The San Antonio River near Runge stood at nearly 35 ft yesterday morning in moderate flooding. The San Saba River at San Saba was at 24.3 ft against a bankful stage of 20. The Devils River is in moderate flooding. The Rio Grande at Laredo was expected to crest near 19 ft.

[00:19:01]Texas is carrying 14 separate alert entries, tied for the highest of any state in the country.

[00:19:06]Here's the part that matters, and it is the reason this belongs in a story about a storm that may never form.

[00:19:12]This is not active flash flooding.

[00:19:14]Nobody in Dimmit County is watching rain come down. The rain that produced these crests fell days ago, hundreds of miles upstream in the Hill Country.

[00:19:22]What is moving through South Texas right now is a routed flood wave. Water traveling downstream on a multi-day timeline arriving under a clear sky.

[00:19:30]The delay between cause and consequence is exactly what makes the Westward Branch dangerous.

[00:19:35]Those channels and flood plains are already full.

[00:19:37]There is no absorptive capacity left in that system.

[00:19:40]Rain that falls on saturated ground does not soak in. It runs off almost immediately and goes straight into rivers that are already at or near their all-time highs.

[00:19:48]A weak, unnamed low-end tropical system arriving over that landscape would not need to be a hurricane to be a catastrophe.

[00:19:55]It would only need to rain. And the state is not in good condition to absorb that in any other sense, either.

[00:20:01]The Fort Worth office is forecasting 101° today with widespread triple-digit afternoon highs by tomorrow and Wednesday, and near record overnight lows by midweek as temperatures struggle to fall below 80° across parts of North Texas.

[00:20:14]The Weather Prediction Center's extended outlook for the 22nd through the 26th calls for at least major heat risk over much of the South with heat indices climbing past 105 and toward 110° in places.

[00:20:26]Emergency response capacity gets consumed by heat before a tropical system ever arrives.

[00:20:31]That combination, rivers at record stage, a population under extended extreme heat, and a low probability track that nobody can rule out is why the Fort Worth office scenario in writing, even while acknowledging that no global model supports it.

[00:20:45]When the consequence is that severe, a low probability is still worth publishing.

[00:20:53]So, where does this leave you? The single most important thing to watch over the next 48 hours is not wind speed and not a category. It is whether the National Hurricane Center confirms a closed low-level circulation. That is is threshold. Everything downstream of that, the name, the track, the warnings, follows from whether a surface center consolidates.

[00:21:12]If reconnaissance or scatterometer data confirms one, this becomes a forecastable system with a cone, and the guessing ends.

[00:21:19]If it does not consolidate by midweek, the trough almost certainly wins, and the whole thing washes out into a rain event.

[00:21:25]The second thing to watch is the 60% figure itself. It is not fixed. Watch whether the National Hurricane Center raises it, lowers it, or upgrades the system to a formal invest with aircraft investigation. Movement in that number is the clearest public signal of which way the internal assessment is trending.

[00:21:41]Third, watch which model family starts converging. Right now, the high-resolution hurricane models are showing a westward scenario the global models have not built at all. If the global models begin generating a system and steering it west, that is the moment the low-probability branch stops being low probability. If the mesoscale models drop the scenario, the story is effectively over. Fourth, and this holds regardless of what the system does, watch the rainfall forecasts along the central Gulf Coast for Wednesday and Thursday.

[00:22:09]The Weather Prediction Center is carrying flash flooding risk there whether or not anything gets named. If you live between northern Florida and Louisiana, the rain is your concern, not the label attached to it. And if you are in Wisconsin, northern Illinois, northeastern Iowa, southeastern Minnesota, or the upper peninsula today, the immediate threat is not in the Gulf at all. It is the enhanced risk over your head with damaging winds as the primary hazard and the possibility of a bowing complex developing this evening.

[00:22:36]Have a way to receive warnings that will wake you up because the wind threat may extend into lower Michigan, northern Indiana, and northwestern Ohio overnight.

[00:22:44]The honest summary is this: A marginal system in the Gulf has a 60% chance of becoming a storm. Three forecast offices read it three different ways. Two families of models disagree about whether it exists at all, and the least likely track is the one that would put it over the most vulnerable ground in the country. Nobody is hiding the answer. The answer has not been determined yet. We will be tracking it as the week develops.