First Forecast Cone of the Hurricane Season Issued as the Tropics Awaken

Potential Tropical Cyclone One to bring a serious flash flood threat to South Texas while NHC monitors two other areas for development

On Monday, the National Hurricane Center designated the sprawling area of low pressure twisting through the southern Gulf of Mexico Potential Tropical Cyclone One, introducing the first forecast cone of the 2024 hurricane season.

The designation of a Potential Tropical Cyclone for a system that isn’t yet a tropical depression or tropical storm but is likely to become one allows the Hurricane Center to issue watches and warnings when land impacts are expected.

Potential Tropical Cyclone One, forecast to become Tropical Storm Alberto by Wednesday, is ushering in a rich tropical airmass to northern Mexico and South Texas which will bring the threat for rounds of heavy rainfall and flash flooding beginning today through Thursday.

Rainfall forecast from Tuesday through early Sunday showing a large swath of 5 to 10 inches along the coastal plains of South Texas, stretching over 400 miles outside the northern bounds of the forecast cone. Rainfall amounts up to 15 inches locally are possible in parts of northern Mexico and South Texas in the coming days.

Because its circulation is expansive, stretching from the eastern Pacific across Mexico and Central America into the northern Gulf, the worst weather will extend well outside the forecast cone, which only captures the most likely location of the low-pressure center.

As we discussed in Monday’s newsletter, much of South Texas is facing moderate to extreme drought in places, so the rainfall isn’t entirely unwelcome, particularly south of the Texas Hill Country. Nevertheless, rainfall rates of 2 to 3 inches or more per hour could cause flash flooding problems, even for more parched grounds.

Weekly U.S. Drought Monitor for Texas showing areas of moderate to extreme drought across South Texas and the Texas Big Bend. Credit: University of Nebraska-Lincoln

The biggest flood concerns will be along the Coastal Bend and farther up the coast of southeast Texas, where strong onshore winds will also bring the threat of coastal storm surge flooding atop the heavy rainfall.

Peak storm surge flooding forecast for Potential Tropical Cyclone One as of 5 AM ET Tuesday showing up to 4 feet of coastal flooding possible from near Freeport, Texas, to the Texas/Louisiana border. Credit: National Hurricane Center

The worst of the rainfall will likely come from late Tuesday through Wednesday for much of South Texas. The heavy rains should begin to slowly taper off on Thursday as the system moves inland over Mexico, but the heavy rain threat, especially for our neighbors south of the border, will persist through the week.

Yet another possible system to come in the southern Gulf

As we previewed in last Friday’s newsletter, models are now indicating the possibility that the Central American Gyre spawns yet another tropical system this weekend right behind Potential Tropical Cyclone One (future Alberto?) in the extreme southern Gulf or Bay of Campeche.

Like the current system, it would likely stay broad and move westward toward Mexico or South Texas by Sunday into next Monday. Of course, the most concerning threat is the potential for back-to-back heavy rain and flood events for these same areas into early next week. Those affected by the rains and coastal hazards of the current system will want to keep tabs on this possible second system coming right on its heels.

Still watching off the southeast U.S. but development odds remain low

We continue to follow a broad area of low pressure left behind from a dying cold front north of Puerto Rico in the southwestern Atlantic. The low-pressure area hasn’t become any better organized since yesterday and strong upper-level winds nearby continue to hold any organization in check.

Low-pressure tracks from the European model ensemble system through Thursday. Forecasts continue to keep the low-pressure area weak and disorganized as it moves toward the southeastern U.S. by later this week. Credit: Weathernerds.org

The good news is rather than tracking in tandem with an upper-level area of low pressure, as models previously showed, it now looks like the disturbance and upper-low will be slightly out-of-sync, which will keep modest to even high wind shear over the area. So for now, development odds appear to be on the decline but given an expected track toward the southeast U.S., we’ll keep an eye on it just in case.

At this time, it’s no concern for South Florida.