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PIETER J. FETERIS

Abstract

A situation that led to rapid developmont of strong winds over the, Northern Persian Gulf is compared with a similar situation in which gales were anticipated but did not occur. In both cases, cold air accumulated over Syria and Northern Iraq. In the first case, deep moist convection over the mountains of Northwestern Iran was coupled with a rapid southwest surge of a tongue of cold air into the Persian Gulf. In the second case, deep convection did not occur, and the cold air did not move southward. Release of latent heat by deep convection and merging of the rising currents with strong winds aloft seemed to have reinforced upslope winds near the surface in the first case, which lifted the warm air in front of the advancing cold air. This explanation is made plausible by a simple energy budget.

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Pieter J. Feteris

Abstract

No abstract available.

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Pieter J. Feteris

Abstract

Records from a network of volunteer thunderstorm observers in the Netherlands are used with routine synoptic and upper-air data to investigate relations between storm severity and almost simultaneous (just prior) meteorological parameters. The latter are derived from fields of the meteorological variables. The χ2 test and screening regression show that the ratio of storm associated with lightning damage to the total number of storms increases significantly with the surface wet-bulb potential temperature (θ sw) and the instability index (ΔT), but the relations are rather weak. Hail frequency increases monotonically with the instability index, but is bimodally distributed with respect to the potential temperature. Hailsize-windshear relations are barely significant. Additional information provided by parameter combination over that in a single best predictor is limited by fairly strong correlations between wind velocities at 700 and 500 mb as well as by correlations among the surface wet-bulb potential temperature, the stability index and the saturation deficit (D). Stratification of the data according to synoptic situation and the use of nonlinear functions of the variables improve some of the relations.

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