Extreme Winter Precipitation Regimes in Eastern North America: Synoptic-Scale and Thermodynamic Environments
Bibliographic record
Abstract
Abstract We define extreme precipitation regimes (EPRs) during the eastern North American winter based on widespread and persistent heavy precipitation, using ERA5 precipitation data from 1979 to 2020. We find 62 EPRs and analyze their synoptic-scale and thermodynamic environments. EPRs impact most of eastern North America with heavy precipitation, especially from Louisiana to Quebec, and generally last for 5–8 days. They are associated with an anomalously strong 500-hPa trough–ridge over western–eastern North America that travels slowly eastward, favoring intrusions of moist, tropical air into eastern North America, and a strong baroclinic zone from the central United States to Atlantic Canada. They are also characterized by high frequencies of cyclones in the midwestern United States, anticyclones over eastern Canada and the subtropical Atlantic, and atmospheric rivers (ARs) in eastern North America. Precipitation is maintained by large moisture influxes, primarily from the Gulf of Mexico and Caribbean Sea, from the EPR start to the time midway through the EPR period. The influxes are often associated with ARs feeding into cyclones, where the moisture falls as precipitation. We also categorize EPRs based on the spatial anomaly correlation (AC) of synoptic-scale weather patterns between individual EPRs and the EPR composite. High AC EPRs have similar but stronger 500-hPa features over North America, greater moisture flux from the Gulf of Mexico and inland precipitation over eastern North America, farther inland cyclone track, higher frequency of subtropical Atlantic anticyclones, and lower EPR-to-EPR variability than low AC EPRs. Significance Statement Cool-season extreme precipitation regimes (EPRs) often lead to flooding and other impacts and represent a significant forecast challenge. We define and analyze EPRs during the eastern North American winter to obtain a better understanding of their associated meteorological conditions. We also categorize EPRs into two distinct categories to capture the variability among EPRs. EPRs generally last 5–8 days and are associated with slowly moving large-scale weather patterns favoring intrusions of moist, tropical air into eastern North America, a strong temperature contrast, and frequent cyclones in the midwestern United States with anticyclones to the north and south. The intrusions of moist, tropical air are often associated with atmospheric rivers (ARs) that deposit their moisture in cyclones as precipitation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".