Wildfire smoke Possible
Daily PM2.5 peaked at 37.9 µg/m³ near New Orleans across 1 covered metro home to 966,230 people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 1.3 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 1.3 million cigarettes. An awareness illustration of outdoor exposure at 22 µg/m³ per cigarette (Berkeley Earth), counting only the event's ranked days; not a medical dose.
Why we think this happened
New Orleans airport reported smoke during five hours of the exact PM2.5 event. FPA-FOD independently records three same-day Louisiana wildfires 33 to 41 miles north of the station, and their bearings align with the event-day wind-from sector while winds were predominantly calm or light. This supports wildfire smoke as a possible broad cause without identifying one contributing fire.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
USDA Forest Service Rocky Mountain Research Station hypothesis
FPA-FOD records three Louisiana wildfires discovered on October 20 within 33 to 41 miles of the New Orleans surface station. Their bearings from the station were 349.7, 9.9, and 39.3 degrees, overlapping the event-day circular mean wind-from direction of 14.7 degrees; 13 of 24 observed hours had winds at or below 3 knots.
NOAA/NWS surface observations via Iowa Environmental Mesonet · Oct 20, 2000 hypothesis
New Orleans - Louis Armstrong, 5.7 km from the PM2.5 target monitor, reported the official present-weather code FU (smoke) during 5 observed hours inside the catalog event window.
Inference, not direct attribution
surface_smoke_plus_bounded_fire_occurrences_possible.v1: This inference is recorded in the catalog methodology.
Evidence path
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
Source or mechanism
surface_smoke_plus_bounded_fire_occurrences_possible.v1. This inference is recorded in the catalog methodology.
Air-mass movement
NOAA HYSPLIT modeled 12 backward paths across multiple arrival times and heights. They show where the air traveled, not which source polluted it.
Explore the modeled paths ↓Local response
EPA monitors recorded the event across 1 metro. The peak daily concentration is roughly 1.7 cigarette-equivalents at the outdoor daily rate.
Inspect the pollutant and weather signals ↓Event autopsy
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Wildfire smoke” explanation; it does not assign the cause by itself.
New Orleans-Metairie, LA
Monitor comparison window 2000-10-17 to 2000-10-23 · PM2.5 target: Kenner
43% above nearby days
36% higher than surrounding days
43% higher than surrounding days
36% higher than surrounding days
46% higher than surrounding days
97% higher than surrounding days
30% higher than surrounding days
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
Air-mass reconstruction
NOAA HYSPLIT traces the air arriving at each metro backward for 72 hours. Multiple arrival times and heights show whether the broad path is stable—or sensitive to assumptions about when and where the polluted layer arrived.
Air arriving near New Orleans-Metairie
Peak-date arrivals · 2000-10-20
Each line begins 72 hours before arrival and points toward the metro. Color represents arrival height; repeated lines represent 00, 06, 12, and 18 UTC arrival assumptions. A path can show where the air traveled, but it cannot prove which source added the PM2.5.
Episode peak
-- cigarettes
The smoke map's scale, replayed over this event: the surface interpolates between covered metros' daily records, framed to the affected region. Hover for a reading, click a metro to pin it to the card. Days a monitor did not report draw nothing.
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| New Orleans-Metairie, LA | 37.9 µg/m³ | 1.7 | Oct 20, 2000 | #24 of its top days |
"Cigarettes, whole event" totals a metro's ranked event days at 22 µg/m³ per cigarette: what a person outdoors there breathed across the event, as the illustration. "All-time standing" is where this episode's days sit in each metro's ranked record (worst-area measure, since 1999). Full local context is on each metro's Air Records page.
Public evidence library
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
NOAA/NWS surface observations via Iowa Environmental Mesonet
New Orleans - Louis Armstrong, 5.7 km from the PM2.5 target monitor, reported the official present-weather code FU (smoke) during 5 observed hours inside the catalog event window.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The surface code establishes smoke at the nearby airport; it does not identify whether the source was a wildfire, prescribed burn, agricultural fire, or another local fire.
USDA Forest Service Rocky Mountain Research Station
FPA-FOD records three Louisiana wildfires discovered on October 20 within 33 to 41 miles of the New Orleans surface station. Their bearings from the station were 349.7, 9.9, and 39.3 degrees, overlapping the event-day circular mean wind-from direction of 14.7 degrees; 13 of 24 observed hours had winds at or below 3 knots.
This source supports a possible mechanism or occurrence; it does not establish the cause by itself.
The three same-day fires totaled only seven reported acres; FPA-FOD does not establish which occurrence produced the observed smoke.
Possible This is a transparent hypothesis supported by limited evidence or an explicit inference, not a definitive attribution.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.