A climatological assessment of Greenland blocking conditions associated with the track of Hurricane Sandy and historical North Atlantic hurricanes
Bibliographic record
Abstract
ABSTRACT In late October 2012, an extreme area of high pressure centred near Greenland, known as a ‘Greenland block’, forced Hurricane Sandy to turn westward into the Northeast coast of the United States. In light of this unusual and catastrophic event, the Greenland blocking conditions associated with Sandy and previous North Atlantic hurricane tracks are examined from a climatological perspective. Two primary questions raised by Sandy are investigated: (1) How anomalous were the Greenland blocking conditions observed prior to Sandy's landfall? (2) Were North Atlantic hurricane tracks in the historical record affected by Greenland blocking conditions in a manner similar to Sandy? The measure of blocking strength used to answer these questions is the Greenland Blocking Index (GBI), which is calculated as the spatial average of 500 hPa heights over the Greenland region. The GBI prior to Sandy's landfall was found to be more typical of late June conditions, exceeding the 90th percentile of late October climatology during the entire preceding week and peaking at near‐record values (99.8th percentile) on 25 October. Analysis of the GBI in relation to past North Atlantic hurricane tracks shows that above‐normal GBI values were associated with a southward displacement of hurricane tracks and an increased concentration of tracks near the Northeast US coast. Additionally, composites of atmospheric conditions for ‘anomalous’ hurricane tracks (defined as tracks with an initial bearing angle between 90° and 360°) revealed an atypical area of high pressure centred over the Canadian Maritimes during these events, whereas near‐climatological conditions of atmospheric pressure over the North Atlantic prevailed for ‘normal’ hurricane tracks. However, variations in Greenland blocking conditions were not associated with significant changes in the frequency of anomalous North Atlantic hurricane tracks.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".