|Tropical Depression Two||Winds: 30 kt|
|Pressure: 1009 mbar|
|Advisory 1 / 10:00 PM CDT Wed July 10, 2019|
The area of disturbed weather in the Gulf of Mexico has acquired enough organization to be declared a tropical depression. It was broad for most of the day, with disorganized thunderstorm activity embedded within a large cyclonic gyre. Over the past few hours, however, convection has become centralized about what appears to be an increasingly well-defined low-level circulation. Satellite intensity estimates at 0z were T1.5/25kt from both SAB and TAFB. In the case of TAFB, the organization was limited by Dvorak constraints and actually assessed a strict estimate of T2.0/30kt. The initial intensity is set to 30kt in agreement with that figure as well as recon data.
Tropical Depression Two is currently being steered west-southwest by an expansive mid-level ridge over New Mexico and Colorado. This ridge is expected to weaken over the coming days as a shortwave trough dives southeast over the Great Lakes. Concurrently, a ridge north of the Greater Antilles will shift west with time. The end result is that Two will find itself in a region with many different competing steering flows, and the exact magnitude of these flows will determine where it tracks. There is a wide range of forecasts as it pertains to the forecast track, with the UKMET highlighting the westernmost solution near Galveston, the HWRF/HMON models highlighting the easternmost solution near New Orleans, and a wide array of scenarios inbetween. A quick glance at 18z soundings versus model forecasts show that, for now, the ridge over the West United States is being slightly underestimated. If this trend continues, it would argue for the tropical cyclone to track more west toward western Louisiana. This trend may be accentuated if Two gains strength at a quick pace in the short term. If it remains weaker, the tendency may be for it to move farther east. For the purpose of my first forecast, I tend to side near the middle solutions, with a landfall over Marsh Island.
A mid-level recon flight about an hour ago found a potent circulation around 16,000 feet, featuring a sharp wind shift and a pressure of 1005mb. Based on shortwave imagery, the low-level circulation is displaced slightly to the northeast, as most model guidance suggested it would be while Two is in its formative stages. This displacement argues for only slow organization over the next 12 to 24 hours while the storm remains in an environment of moderate wind shear. By tomorrow night, though, upper-level winds are likely to become light as persistent convection releases latent heat and leads to the development of an anticyclone aloft. Water temperatures near or over 30C argue for plenty of moisture to sustain this convection and quell the effects of continental dry air. Like with the track forecast, there is a wide array of intensity forecasts. The GFS is weakest, portraying a strong tropical storm at peak. The HWRF and HMON, the former of which has been our best intensity model for several years running, represent a high-end solution where Two attains major hurricane strength. This is supported by the UKMET, although that would be the expectation with a storm that tracks as far west as that model suggests. The SHIPS shows a strong tropical storm, and the LGEM a weak one, but these models are not likely to be of much use in the short term because the large grid size they are derived from is likely keying in on enhanced wind shear in the non-immediate environment that will not affect Two itself. Given the environment and past model tendencies, my intuition is to follow model consensus as Two organizes, placing more weight on the HWRF/HMON hurricane models after the storm develops an inner core. This brings Two to near Category 2 strength prior to landfall. It goes without saying this is a low-confidence forecast.
FORECAST MAX WINDS
INIT 11/0300Z 30 KT 35 MPH
12H 11/1200Z 35 KT 40 MPH
24H 12/0000Z 40 KT 45 MPH
36H 12/1200Z 50 KT 60 MPH
48H 13/0000Z 65 KT 75 MPH
72H 14/0000Z 80 KT 90 MPH...APPROACHING LANDFALL
96H 15/0000Z 50 KT 60 MPH...INLAND120H 16/0000Z 25 KT 30 MPH...POST-TROP/REMNT LOW