The Setup
Open-sea vessel encounters in the past 45 days resolve at shorter average minimum ranges than approach channels or anchorages. 16.7% of those encounters pass within 0.1nm. The detection system classifies open-sea encounters approximately 46 minutes after the closest-approach moment has passed — nearly four times later than confined-water events.
That is the maritime finding. Here is the real estate question it raises.
Houston carries a cell-score composite of 52.4 out of 100. Economic strength: 58. Safety environment: 87. Development pipeline: 4. Seattle's composite is 53.4 — economic strength 65, safety 78, pipeline 1.6. Los Angeles: composite 51.5, economic strength 61, safety 81, pipeline 4.
These three metros share a structural feature: their economies are materially exposed to port-call timing. Houston's Ship Channel is the largest petrochemical export corridor in the United States. Los Angeles and Long Beach handle roughly 40% of US container imports. Seattle's port serves transpacific container and bulk export routes. When cargo arrival timing degrades, demand for port-adjacent industrial space — bonded warehouses, transload facilities, cold storage with variable dwell capacity — shifts.
The maritime timing signal is not currently in these cell scores.
The Chain
Cell scores aggregate signals measured at ground level: permit velocity, code enforcement backlogs, employment density, transit accessibility, safety incident rates. None of those inputs captures the upstream shipping encounter rate or the detection lag profile of the sea lanes feeding the port.
A 46-minute post-CPA classification window in open sea means cargo arrival timing carries hidden variance that does not surface in berth utilization data until it materializes as a congestion event. When vessels converge to 0.031nm minimum range in open water and the record is classified retrospectively, the cargo aboard is still days from berth. The timing uncertainty propagates downstream: transload operators build buffer inventory, warehouses absorb dwell variability, distribution hub throughput fluctuates.
Houston's economic strength score of 58 reflects realized economic output measured at ground level. It does not reflect the expected variance in that output attributable to upstream maritime timing noise. The same applies to Seattle (65) and LA (61).
The development pipeline scores — 4.0 for Houston and LA, 1.6 for Seattle — indicate limited new construction signal in the scored cell footprint. Port-adjacent industrial development is sensitive to cargo throughput predictability: predictable throughput supports longer leases, stronger tenant credit, and more pipeline activity. The current pipeline scores suggest those markets are not generating meaningful new construction signal at the cell level.
The Implication
The point is not that Houston's composite should be lower. Cell scores are designed to aggregate ground-level signals, and Houston's ground-level metrics support a composite in the low 50s. The point is that the composite's confidence bounds are narrower than appropriate for a market where upstream maritime timing risk is real and currently elevated.
A site-selection analyst treating 52.4 as a stable point estimate for Houston's economic environment is implicitly treating port cargo timing as stable. The maritime data suggests otherwise: 16.7% of open-sea encounters in the past 45 days passed within 0.1nm, the detection system runs 46 minutes behind in open water, and three of the largest US port corridors are served by those same sea lanes.
What to Watch
The most actionable signal is not the metro composite but the development pipeline score for port-adjacent hex cells specifically — not the metro average. A metro average of 4 can conceal a port-adjacent cluster at zero. If that cluster begins to move, maritime timing would be one plausible upstream driver, alongside port capital project announcements and lease-market tightening.
Limitations
Cell scores do not currently incorporate maritime data as a direct input. The link from open-sea encounter geometry to port-adjacent pipeline runs through cargo timing, throughput, lease demand, and construction signal — a chain with multiple intervening variables and indeterminate lag times. The 46-minute detection lag is an average across all open-sea contexts globally, not specific to US Gulf or Pacific routes.
The pipeline scores for Houston and LA at exactly 4.0 with zero standard deviation suggest a possible floor value or sparsely populated signal in those geographies. The comparison to Chicago's 15.7 may be partly a data coverage artifact rather than purely a market-structure difference.
Data as of 2026-05-12. Sources: pairwise_encounter (n=555,679, 45-day window); cell_scores (Houston n=130 cells, LA n=148, Seattle n=128, computed 2026-05-11/12).