In this article the concept of weather regimes is used to assess the flow-dependent skill of the European Centre for Medium-range Weather Forecast (ECMWF) ensemble predictions at the late medium-range. The flow patterns leading to more or less accurate predictions are identified and the variations of skill in these situations are quantified. The focus is on the Euro-Atlantic sector during the extended winter period when the atmospheric regime structure is most pronounced. Verification results show that, in the medium range, forecasts initiated in the negative phase of North Atlantic Oscillation (NAO−) are the most skillful. For these forecasts the ensemble spread over Europe is lower than average, showing that the ensemble spread provides useful information about the error of the ensemble-mean forecast. The performance of the ensemble is further assessed by stratifying the cases according to their initial conditions, as well as by their accuracy at forecast day 10. Results indicate that the least skillful predictions are mainly associated with missing the transitions to a blocking regime circulation. Forecasts also underestimate the blocking persistence, whereas they overestimate the persistence of zonal flows. Transitions to a positive phase of the NAO are also overrepresented.

The accuracy of deterministic and probabilistic forecasts of storms in the Adriatic Sea that lead to the flooding of Venice is discussed. We consider ECMWF state-ofthe-art high-resolution single deterministic and lower-resolution ensemble-based forecasts of meteorological and sea states (

N-Protected b-propargylamino acrylic estersw ith ap ush-pull olefinic bonda ffordedg ood to high yields of dihydropyridines upont reatment with 5% tris(2-furyl)phosphine-gold(I) chloride/silver(I) tetrafluoroborate [(TFP)AuCl/AgBF 4 ]i na nhydrousb enzene.C arbamate and sulfonyl groups were employed for nitrogen protection. On am odel enyne, the p-methoxybenzenesulfonyl (MBS) group was found to be ab etter protective group than tosyl in termso fc yclization yield, and also the yield of elimination to the corresponding 2,3,4-trisubstituted pyridines.B oc-protectedd ihydropyridines underwent partiald eprotection/oxidationu nder the cyclization conditions,w hich enabled am ore straightforward, one-pot preparation of the corresponding pyridines. In another application, an appropriately substituted derivative protecteda sastablem ethoxycarbamate was subjected to catalytic hydrogenation affording the known precursor of paroxetine.T he chemoselectivity of enynec yclization (dihydropyridine vs. pyrrole) is governed, among other factors,b yC -3 substitution. Dihydropyridinesw ere obtained as sole products regardless of the catalyst/conditions when C-3 was unsubstituted.

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