The dates of the transition between winter and summer (W2S) and between summer and winter (S2W) regional-scale atmospheric regimes have been defined using daily weather types above and around the Caribbean basin from 1979 to 2017. The uncertainties due to either the use of two different reanalyses (i.e., NCEP-DOE and ERA-Interim) or the parametrization used for the definition of the transition dates have typically a small impact on the interannual variability of the seasonal transitions. When both reanalyses are considered together, the average W2S transition date occurs, on average, on May 13 (with a standard deviation of 9 days) while the S2W transition date occurs, on average, on October 26 (with a standard deviation of 12 days). The atmospheric characteristics associated with both transitions reveal asymmetries in the annual cycle. The W2S transition is rather abrupt and near-synchronous to a rather sharp increase of rainfall, propagating from Central America to the NE of the Caribbean basin, and a weakening of the Caribbean Low Level Jet. The W2S transition is also not preceded by any significant sea surface temperature (SST) anomalies either in the tropical North Atlantic or the Eastern Pacific. On the other hand, the S2W transition is overall smoother, and anomalously warm (cold) SST over the Caribbean Sea and Gulf of Mexico (Eastern Pacific) during the boreal summer are usually related to a delayed transition (and vice versa). The interannual variations of S2W and W2S transitions are mostly independent to each other. The potential and real-time predictability of the W2S transition is explored using a subseasonal-to-seasonal prediction ensemble (11 runs from 1998 to 2017) from the ECMWF model. Its skill is close to zero with a lead time longer than 15–20 days, confirming the weak impact of the antecedent SST upon the W2S transition. The skill suddenly increases from late April, 2–3 weeks only before the mean W2S transition date. It suggests that some atmospheric forcing, operating from synoptic to intra-seasonal time scale, plays a role, but it seems barely related to any occurrence, or sequence, of specific weather types.

冬季和夏季（W2S）以及夏季和冬季（S2W）区域尺度大气模式的过渡日期已使用1979年至2017年加勒比海盆地之上和周围的每日天气类型进行了定义。两个不同的重新分析（即NCEP-DOE和ERA-Interim）中的一个或用于定义过渡日期的参数化通常对季节性过渡的年际变化影响很小。当同时考虑两个重新分析时，平均W2S过渡日期平均发生在5月13日（标准偏差为9天），而S2W过渡日期平均发生在10月26日（标准偏差为12天） ）。与这两个转变有关的大气特征揭示了年周期的不对称性。W2S过渡非常突然，几乎与降雨同步急剧增加，从中美洲传播到加勒比海盆地的东北部，以及加勒比低空急流减弱。在W2S过渡之前，热带北大西洋或东太平洋也没有任何明显的海表温度（SST）异常。另一方面，S2W过渡总体上较为平稳，在北方夏季，加勒比海和墨西哥湾（东太平洋）异常暖（冷）的SST通常与延迟过渡有关（反之亦然）。S2W和W2S过渡的年际变化大多彼此独立。W2S转换的潜力和实时可预测性是使用ECMWF模型中的从季节到季节的预测合奏（1998年至2017年为11个阶段）进行探索的。它的技能接近于零，交货时间超过15–20天，证实了先前的SST对W2S过渡的弱影响。该技能从4月下旬（平均W2S过渡日期之前的2-3周）突然增加。这表明从天气天气到季节内时间尺度的某些大气强迫起作用，但似乎与特定天气类型的任何发生或顺序都没有关系。仅在平均W2S过渡日期之前的2-3周。这表明从天气天气到季节内时间尺度的某些大气强迫起作用，但似乎与特定天气类型的任何发生或顺序都没有关系。仅在平均W2S过渡日期之前的2-3周。这表明从天气天气到季节内时间尺度的某些大气强迫起作用，但似乎与特定天气类型的任何发生或顺序都没有关系。