06/18/2026
Based on the GOES-East Channel 13 (Clean IR) satellite imagery from 9:35 PM CDT, we are looking at a highly asymmetric, heavily sheared tropical system typical of early-season Gulf developments.
Here is a scientific breakdown of the structural presentation, shear dynamics, and subsequent impacts for southeastern Louisiana.
1. Convective Structure & Organization
The satellite presentation highlights a classic sheared/disorganized tropical cyclone.
Core Convection: The deepest, most intense convection—denoted by the dark red and orange cold cloud tops (indicative of cloud-top temperatures likely dropping below -60^\circ\text{C} to -70^\circ\text{C})—is entirely displaced from the low-level circulation center (LLCC).
Banding & Rainfall Shield: Rather than a symmetrical core wrapping around a defined center, Arthur’s primary convective energy is concentrated in a massive cluster directly south of the Louisiana coast.
A broad multi-banded structure (represented by the green and blue cloud-top gradients) is lifting directly north-northeast over southeastern Louisiana, embedding New Orleans and surrounding coastal zones in a high-efficiency warm rain process.
2. Environmental Wind Shear:
The imagery provides clear evidence of moderate-to-strong westerly/northwesterly vertical wind shear:
Displacement: The low-level circulation is scraping the upper Texas/southwestern Louisiana border, yet almost the entirety of the deep convective canopy is blown out to the east and south-southeast.
Cirrus Outflow: Notice the classic asymmetric fan of the high-level cirrus shield blowing off toward the east and southeast.
This hostile upper-level environment is preventing the storm from vertically aligning, keeping Arthur a weak, lopsided system in terms of wind, but consolidating its deep tropical moisture entirely into a dangerous downpour engine over the northern Gulf Coast.
3. Expected Impacts: Southeastern Louisiana Coast:
Despite Arthur’s center tracking well to the west toward the upper Texas coast/SW Louisiana, the lopsided structure means southeastern Louisiana is bearing the brunt of the deepest moisture plume and convective energy.
🌧️ Torrential Rainfall & Flash Flooding (Primary Threat) Precipitation Efficiency:
The deep red convective core in the marine environment is pushing directly into the coastal and marine warning polygons visible on your display.
Totals: Widespread totals of 5 to 10 inches are expected, with isolated higher training bands capable of producing localized amounts up to 15–20 inches. Given the active Flash Flood Warnings (red polygons) already dr**ed over the New Orleans metro and coastal parishes, urban drainage systems will easily be overwhelmed.
🌊 Coastal Flooding & Storm Surge
Onshore Flow: Persistent, strong south-to-southeasterly low-level flow on the east side of the circulation will continue to push water into the bays, bayous, and Lake Pontchartrain.
Surge Totals: A storm surge of 2 to 4 feet (locally up to 5 feet in surge-prone coastal indents) is likely, exacerbated by high tide cycles. This will cause persistent inundation of low-lying coastal roads outside the levee protection systems.
🌪️ Embedded Severe / Tornado Threat
Helicity & Shear: The outer convective bands crossing the coast are operating in an environment with high low-level directional shear.
Tornadic Potential: As these cells cross the marine-to-land boundary (indicated by the blue marine warning polygons pushing inland), brief, rain-wrapped EF-0 to EF-1 tornadoes can easily spin up with little to no visual warning.
💨 Wind Gusts:
While sustained winds remain well below hurricane strength (40–45 mph), standard squalls within those deep convective bands will easily transfer higher momentum aloft down to the surface, bringing frequent marine and coastal gusts of 45 to 55 mph, capable of localized power outages and tree damage.
