The Impact of Tropical Remnants on Extratropical Cyclogenesis: Case Study of Hurricanes Danielle and Earl (1998)
Bibliographic record
Abstract
The importance of remnant tropical cyclone (TC) circulation and moisture structures is investigated for a simultaneous extratropical transition (ET) event involving ex-Hurricanes Danielle and Earl (September 1998). Although both storms undergo prolonged periods of reintensification following ET, the forcings involved in each of their redevelopment processes differ fundamentally. A review of the tropical and baroclinic ET modes in the North Atlantic stresses the importance of jet/front structures to the nature of the reintensification process. Ex-Hurricane Danielle begins to redevelop in the eastern half of the basin in the downstream, poleward sector of an intensifying polar jet. The system undergoes a tropical mode of reintensification, resulting in a troposphere-deep warm environment surrounding the storm, devoid of near-surface fronts and maintained by strong tropopause folds at its periphery. Ex-Hurricane Earl reintensifies near the eastern seaboard according to a baroclinic mode, under the influence of an upshear upper-level trough. A rapid cyclonic rollup of upper-level potential vorticity over the reintensifying low-level center results in a strong baroclinic system with well-defined frontal boundaries. The two elements of the remnant TCs considered here are circulation and moisture. Potential vorticity-based modifications are made to the initial atmospheric state of the Mesoscale Compressible Community model in order to remove either one or both of these possible cyclogenetic forcings. The resulting set of sensitivity tests is analyzed in terms of system intensity and structure. It is found that the tropical-mode reintensification (ex-Hurricane Danielle) process requires the presence of the remnant's circulation and moisture for rapid redevelopment. However, the baroclinic-mode transition studied (ex-Hurricane Earl) is remarkably insensitive to the removal of the ex-tropical vorticity and moisture structures of the TC remnant.
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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 | 0.000 | 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) | 0.001 | 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".