| Abstrakt: |
We use short‐range ensemble forecasts and ensemble clustering analysis to study the factors affecting the intensification of Hurricane Patricia (2015). Convection‐permitting ensemble forecasts are classified into two groups: 10 spin‐down (SPD) members and 10 spin‐up (SPU) members with intensification rates of <0 and >0 m s−1 for the first 6 hr, respectively. Ensemble clustering analysis found that the wind–pressure relationship was incorrect in the SPD group, indicating that the SPD issue may be partly caused by an imbalance in the initial minimum sea‐level pressure (MSLP) and the maximum wind speed (MWS). The SPD issue appears to be related to three main points: (a) a weaker upper‐level warm core; (b) a drier inner core at low levels; and (c) a dry, cold air intrusion at mid‐levels. In contrast, the SPU group has a stronger upper‐level warm core and a relatively wet inner core at lower levels, as well as a relatively strong secondary circulation. These favorable initial conditions in the SPU group, combined with a greater updraft and stronger convection around the eyewall, result in more latent heating around or in the eyewall that favors the intensification of the tropical cyclone. Comparisons between the SPD and SPU groups suggest that the analyzed ensemble could not accurately capture the relationship between the initial MSLP and MWS, which, combined with the unfavorable thermodynamic conditions at the initial time, resulted in the incorrect evolution of the intensity. Therefore, improving the initial conditions appears to be an effective way to address the SPD issue. Plain Language Summary: Intensity spin‐down (SPD) has been identified as a major issue in numerical hurricane models because maximum wind speed can decrease significantly and artificially in the first few hours of a simulation, thereby degrading the remainder of the intensity forecast. Ensemble clustering analysis was performed to explore the role of the thermodynamic structure of the inner core in predicting the intensification of Hurricane Patricia (2015). Convection‐permitting ensemble forecasts are classified into SPD and spin‐up (SPU) groups based on the intensification rates for the first 6 hr. Several statistically significant differences between the SPD and SPU members were found in the wind–pressure relationship, the upper‐level warm core, moisture in the inner core, and secondary circulation. Particularly, the SPD issue may be partly caused by an imbalance in the initial wind–pressure relationship. Moreover, it also appears to be related to three main points: a weaker upper‐level warm core; a drier inner core at low levels; and a dry, cold air intrusion at mid‐levels. However, the intensification of the hurricane was sensitive to the upper‐level warm core, moisture in the inner core, and secondary circulation. Overall, thermodynamic structure of the inner core plays a key role in predicting the intensification of Hurricane Patricia (2015). Key Points: The spin‐down issue may be partly caused by an imbalance in the initial wind–pressure relationshipIntensification of the hurricane was sensitive to the upper‐level warm core, moisture in the inner core, and secondary circulationThe thermodynamic structure of the inner core plays a key role in predicting the intensification of Hurricane Patricia (2015) [ABSTRACT FROM AUTHOR] |
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